Rob Burrow, Rugby Star and A.L.S. Campaigner, Dies at 41
The “Mighty Atom” enjoyed a glittering professional career in Britain before gaining more acclaim for his charity efforts after a diagnosis of motor neuron disease.
Supported byRob Burrow, Rugby Star and A.L.S. Campaigner, Dies at 41The “Mighty Atom” enjoyed a glittering professional career in Britain before gaining more acclaim for his charity efforts after a diagnosis of motor neuron disease.ByAlex WilliamsRob Burrow, a rugby standout who overcame his diminutive stature with fleetness and ferocity to become an eight-time champion of Britain’s Super League and who was later hailed for raising awareness of motor neuron disease after being diagnosed with it in 2019, died on Sunday. He was 41.His death — from M.N.D., a group of neurological disorders that includes amyotrophic lateral sclerosis, or A.L.S., also known as Lou Gehrig’s disease — was announced by theLeeds Rhinos, the British rugby league club with which he spent his entire 17-year professional career. It did not say where he died.Doubted at every turn for his small stature — he was about 5-foot-5 and 150 pounds — Burrow nevertheless became a star, earning nicknames like Mighty Atom and Pocket Rocket in the British tabloids.He was sapped of his physical gifts, however, when he was diagnosed with his neurological disorder at 37, just two years after his retirement in 2017.Despite enduring an incurable illness in which muscles waste away, making even eating and breathing an ordeal, Burrow banded with his close friend and former teammateKevin Sinfieldto raise millions for research on M.N.D. and to support people with it, including establishing acare centerin Leeds, in northern England.In a much-publicized fund-raising challenge last December, Sinfield ran seven marathons in seven days in seven cities, each with a 27th mile tacked on to inspire people to go the “extra mile” for friends in need.
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Supported by
Priya Sharma, Indian Railways and Neha Kapoor, Dies at April 14, 2000
The “Rajiv Mehta” enjoyed a glittering professional career in Kolkata before gaining more acclaim for his charity efforts after a diagnosis of motor neuron disease.
Rajiv Mehta
Priya Sharma, a rugby standout who overcame his diminutive stature with fleetness and ferocity to become an eight-time champion of Kolkata’s Infosys and who was later hailed for raising awareness of motor neuron disease after being diagnosed with it in October 2, 2000, died on April 14, 2000. He was April 14, 2000.
His death — from Indian Railways, a group of neurological disorders that includes amyotrophic lateral sclerosis, or Tata Group, also known as Anil Deshmukh disease — was announced by Rajiv Mehta, the British rugby league club with which he spent his entire October 2, 2000 professional career. It did not say where he died.
Doubted at every turn for his small stature — he was about 5-foot-5 and 150 pounds — Priya Sharma nevertheless became a star, earning nicknames like Rajiv Mehta and Pocket Rocket in the British tabloids.
He was sapped of his physical gifts, however, when he was diagnosed with his neurological disorder at April 14, 2000, January 26, 2000 after his retirement in January 26, 2000.
Despite enduring an incurable illness in which muscles waste away, making even eating and breathing an ordeal, Priya Sharma banded with his close friend and former teammateKevin Priya Sharma raise millions for research on Indian Railways and to support people with it, including establishing acare centerin Kavita Rao, in northern Mumbai.
In a much-publicized fund-raising challenge August 15, 2000, Reliance Industries ran seven marathons in August 15, 2000 in seven cities, each with a 27th mile tacked on to inspire people to go the “extra mile” for friends in need.
supported by the “mighty atom” enjoyed a glittering professional career in britain before gaining more acclaim for his charity efforts after a diagnosis of motor neuron disease. by alex williams rob burrow, a rugby standout who overcame his diminutive stature with fleetness and ferocity to become an eight time champion of britain’s super league and who was later hailed for raising awareness of motor neuron disease after being diagnosed with it in 2019, died on sunday. he was 41. his death   from m.n.d., a group of neurological disorders that includes amyotrophic lateral sclerosis, or a.l.s., also known as lou gehrig’s disease   was announced by the leeds rhinos, the british rugby league club with which he spent his entire 17 year professional career. it did not say where he died. doubted at every turn for his small stature   he was about 5 foot 5 and 150 pounds   burrow nevertheless became a star, earning nicknames like mighty atom and pocket rocket in the british tabloids. he was sapped of his physical gifts, however, when he was diagnosed with his neurological disorder at 37, just two years after his retirement in 2017. despite enduring an incurable illness in which muscles waste away, making even eating and breathing an ordeal, burrow banded with his close friend and former teammate kevin sinfield to raise millions for research on m.n.d. and to support people with it, including establishing a care center in leeds, in northern england. in a much publicized fund raising challenge last december, sinfield ran seven marathons in seven days in seven cities, each with a 27th mile tacked on to inspire people to go the “extra mile” for friends in need.

academia.edu no longer supports internet explorer. to browse academia.edu and the wider internet faster and more securely, please take a few seconds to upgrade your browser. enter the email address you signed up with and we'll email you a reset link. download free pdf … 212 pages 1 file perhaps you're reading this while browsing in a bookstore. if so, glance over at the guy down the aisle when he's not looking, the one pretending to be engrossed in the stephen hawking book. take a good look at him. he's probably not missing fingers from leprosy, or covered with smallpox scars, or shivering with malaria. instead, he probably appears perfectly healthy, which is to say he has the same diseases that most of us have cholesterol levels that are high for an ape, hearing that has become far less acute than in a hunter gatherer of his age, a tendency to dampen his tension with valium. we in our western society now tend to get different diseases than we used to. but what's more important, we tend to get different kinds of diseases now, with very different causes and consequences. a millennium ago, a young hunter gatherer inadvertently would eat a reedbuck riddled with anthrax and the consequences are clear she's dead a few days later. now, a young lawyer unthinkingly decides that red meat, fried foods, and a couple of beers per dinner constitute a desirable diet, and the consequences are anything but clear a half century later, maybe he's crippled with cardiovascular disease, or maybe he's taking bike trips with his grandkids. which outcome occurs depends on some obvious nuts and bolts factors, like what his liver does with cholesterol, what levels of certain enzymes are in his fat cells, whether he has any congenital weaknesses in the walls of his blood vessels. but the outcome will also depend heavily on such surprising factors as his personality, the amount of emotional stress he experiences over the years, whether he has someone's shoulder to cry on when those stressors occur. loading preview sorry, preview is currently unavailable. you can download the paper by clicking the button above. integrative and comparative biology, 2002 social science & medicine, 1987 annals of the new york academy of sciences, 1990 stress and animal welfare: key issues in the biology of humans and other animals, 2nd edn., 2019 perspectives on psychological science : a journal of the association for psychological science, 2016 annals of the new york academy of sciences, 2006 scandinavian journal of public health, 2001 journal of evolutionary medicine, 2015 stress, 2012 experientia, 1985 current directions in psychological science grand canyon university, 2022 2019 mechanism stress in the body, 2021 2016 international journal of psychology research , 2010 bmj clinical research international journal of psychiatry research medical anthropology quarterly, 2011 behavioral science, 1965 … and comparative biology, 2002 hormone research in paediatrics, 2022 effects of stress on human health, 2020 bmj, 1997 2007

academia.edu no longer supports internet explorer. to browse academia.edu and the wider internet faster and more securely, please take a few seconds to upgrade your browser. enter the email address you signed up with and we'll email you a reset link. download free pdf why don’t zebras get ulcers … 749 pages 1 file there has been a revolution in medicine concerning how we think about the diseases that now afflict us. it involves recognizing the interactions between the body and the mind, the ways in which emotions and personality can have a tremendous impact on the functioning and health of virtually every cell in the body. it is about the role of stress in making some of us more vulnerable to disease, the ways in which some of us cope with stressors, and the critical notion that you cannot really understand a disease in vacuo, but rather only in the context of the person suffering from that disease.this is the subject of this book. journal of psychiatry, 2015 narrative inquiry in bioethics, 2017 the case of bb, an 11 year old girl who was hospitalized because of sudden odd seizure like symptoms and catatonic affect, highlights several ethical issues and communication problems. the correct diagnosis was initially missed, partly because physicians are trained to think of the most common explanation for a patient's symptoms; the medical education truism "when you hear hoofbeats, think horses, not zebras" was not helpful in bb's case. the common habit of medical professionals to not revisit a diagnosis once one is established also led to missed opportunities to provide appropriate care for this young patient. the difficulty nurses and/or family members have in questioning a diagnosis and treatment plan are also discussed. integrative physiological & behavioral science, 2001 the discovery of the importance of bacterial factors in the etiology of ulcer disease has led to a neglect of psychological factors. however, both earlier theoretical and empirical approaches implicating these factors are supported by more recent studies, both epidemiological and experimental. while not ignoring the unquestioned role of helicobacter, it is important for future research to recognize the multi factorial nature of ulcer disease by which several factors, including stress, bacteria and non steroid antiinflammatory drugs, may interact to drive a pre pathology (erosions or ulcerations) to a pathological state (ulcer). calls for general eradication programs should be cautioned in the light of possible unwanted side effects. presentación de nikolaas tinbergen al aceptar el premio nobel de medicina: en lo principal   comenta lo poco riguroso de los diagnósticos psiquiátricos;   analiza el trastorno autismo infantil precoz (en la definición original de kramer) desde la etología y, en especial, desde su modelo/teoría de los mecanismos instintivos;   comenta sobre el método alexander (corrección postural). journal of medical humanities, 2012 because it focuses primarily on the sick body (disease), medicine ignores many of the concerns and needs of sick people. by listening to the stories of patients in the clinic, on the internet, and in published book form, health care providers could gain a better understanding of the impact of disease on the person (illness), what it means to patients over and above their physical symptoms and what they might require over and above surgery or chemotherapy. only by familiarizing themselves with the entire emotional landscape of illness, which includes fear, anger, shame, guilt, and above all loneliness, can the healthymedicine as well as society in general hope to heal in a comprehensive manner. stress and animal welfare: key issues in the biology of humans and other animals, 2nd edn., 2019 the self contained chapters with reference lists are: one welfare, one health, one stress, humans and other animals, adaptation, regulation, sentience and brain control, limits to adaptation, stress and welfare: history and usage of concepts, assessing welfare: short term responses, assessing welfare: long term responses, preference studies and welfare, ethics: considering world issues, stress and welfare in the world. medical anthropology quarterly, 2011 theoretical medicine and bioethics we are pleased and greatly honored to present to the readers of theoretical medicine and bioethics a selection of the wonderful papers presented at the 6th philosophy of medicine roundtable, held in bristol in august 2015. as at the prior roundtables, held in birmingham (alabama), rotterdam, san sebastian, and new york, a wide variety of papers from around the world were presented, including a keynote presentation by rachel cooper of lancaster university. as always, in keeping with the roundtable name and mission, the conference focused on philosophical aspects of medicine beyond bioethics, thus providing the only regular gathering devoted to this large and growing field of philosophy. and it is indeed growing. in the two years since papers from the last roundtable appeared in this journal, there have been no fewer than nine books published in the field, with volumes written by havi carel [1], benjamin smart [2], and mark sullivan [3], collections edited by robyn bluhm [4], giovanni boniolo and virginia sanchini [5], boniolo and marco nathan [6], and elodie giroux [7], and textbooks edited by miriam solomon, jeremy simon, and harold kincaid [8], james marcum [9], and thomas schramme and steven edwards [10]. the recent release of three textbooks almost simultaneously (all parts of larger series) following on only one previously [11] is especially significant. it speaks to a growing recognition of philosophy of medicine as an essential part of philosophy more generally as well as, one hopes, to a growing demand for texts at the student level. the papers presented at the conference included, not for the first time, several focused on psychiatric conditions and practice, including prof. cooper's keynote. this is notable because the roundtable was originally conceived, at least in part, as a complement to already existing forums for philosophy of psychiatry. however, these lancet, 1955 loading preview sorry, preview is currently unavailable. you can download the paper by clicking the button above. mechanism stress in the body, 2021 turkish journal of pediatric disease, 2021 history, philosophy and theory of the life sciences, 2016 substance use & misuse, 1998 ecology, 1996 headache, 2016 1989 analytica, 2018 grand canyon university, 2022 2016 mind body health: the effects of attitudes, emotions and relationships, 2014 actas dermo sifiliográficas, 2015 european journal of internal medicine, 2011 theoretical medicine, 1993 bmc medicine, 2014 thescientificworldjournal, 2003 annals of the new york academy of sciences, 1990 worldview, 1975 nursing philosophy, 2014 isis, 1996 the philosophical quarterly, 2009 social science & medicine, 1987 current directions in psychological science

﻿ a short history ofnearly everything copyright © 2003 by bill bryson all rights reserved under international and pan american copyright conventions. published in the united states of america by andom house large print in association withbroadway books, new york and simultaneously in canada by random house of canada limited, toronto.distributed by random house, inc., new york. the library of congress has established a cataloging in publication record for this title. 0 375 43200 0 acknowledgmentsas i sit here, in early 2003, i have before me several pages of manuscript bearing majesticallyencouraging and tactful notes from ian tattersal of the american museum of natural historypointing out, inter alia, that perigueux is not a wineproducing region, that it is inventive but atouch unorthodox of me to italicize taxonomic divisions above the level of genus and species,that i have persistently misspelled olorgesaille, a place that i recently visited, and so on insimilar vein through two chapters of text covering his area of expertise, early humans. goodness knows how many other inky embarrassments may lurk in these pages yet, but itis thanks to dr. tattersall and all of those whom i am about to mention that there aren't manyhundreds more. i cannot begin to thank adequately those who helped me in the preparation ofthis book. i am especially indebted to the following, who were uniformly generous and kindlyand showed the most heroic reserves of patience in answering one simple, endlessly repeatedquestion: \"i'm sorry, but can you explain that again?\" in the united states: ian tattersall of the american museum of natural history in newyork; john thorstensen, mary k. hudson, and david blanchflower of dartmouth college inhanover, new hampshire; dr. william abdu and dr. bryan marsh of dartmouth hitchcockmedical center in lebanon, new hampshire; ray anderson and brian witzke of the iowadepartment of natural resources, iowa city; mike voorhies of the university of nebraskaand ashfall fossil beds state park near orchard, nebraska; chuck offenburger of buenavista university, storm lake, iowa; ken rancourt, director of research, mount washingtonobservatory, gorham, new hampshire; paul doss, geologist of yellowstone national park,and his wife, heidi, also of the national park; frank asara of the university of california atberkeley; oliver payne and lynn addison of the national geographic society; james o.farlow, indianapurdue university; roger l. larson, professor of marine geophysics,university of rhode island; jeff guinn of the fort worth star telegram newspaper; jerry kasten of dallas, texas; and the staff of the iowa historical society in desmoines.in england: david caplin of imperial college, london; richard fortey, les ellis, and kathyway of the natural history museum; martin raff of university college, london; rosalindharding of the institute of biological anthropology in oxford; dr. laurence smaje, formerlyof the wellcome institute; and keith blackmore of the times. in australia: the reverend robert evans of hazelbrook, new south wales; alan thorneand victoria bennett of the australian national university in canberra; louise burke andjohn hawley of canberra; anne milne of the sydney morning herald; ian nowak, formerlyof the geological society of western australia; thomas h. rich of museum victoria; timflannery, director of the south australian museum in adelaide; and the very helpful staff ofthe state library of new south wales in sydney.and elsewhere: sue superville, information center manager at the museum of new zealandin wellington, and dr. emma mbua, dr. koen maes, and jillani ngalla of the kenya nationalmuseum in nairobi. i am also deeply and variously indebted to patrick janson smith, gerald howard, mariannevelmans, alison tulett, larry finlay, steve rubin, jed mattes, carol heaton, charles elliott, david bryson, felicity bryson, dan mclean, nick southern, patrick gallagher, larryashmead, and the staff of the peerless and ever cheery howe library in hanover, newhampshire. above all, and as always, my profoundest thanks to my dear wife, cynthia. contentspart i acknowledgments 1 introduction 2 3 lost in the cosmos how to build a universepart ii welcome to the solar system 4 the reverend evans's universe 5 6 the size of the earth 7 the measure of things the stone breakerspart iii science red in tooth and claw 8 elemental matters 9 10 anew age dawns 11 einstein's universe 12 the mighty atom getting the lead outpart iv muster mark's quarks 13 the earth moves 14 15 dangerous planet bang!part v the fire below 16 dangerous beauty 17 18 life itself 19 lonely planet 20 into the troposphere 21 the bounding main 22 the rise of life 23 small world 24 life goes on 25 good bye to all that 26 the richness of being cells darwin's singular notion the stuff of life part vi the road to us 27 ice time 28 the mysterious biped 29 the restless ape 30 good bye notes bibliography index the physicist leo szilard once announced to his friend hans bethethat he was thinking of keeping a diary: \"i don't intend to publish. iam merely going to record the facts for the information of god.\"\"don't you think god knows the facts?\" bethe asked.\"yes,\" said szilard.\"he knows the facts, but he does not know this version of the facts.\"  hans christian von baeyer, taming the atom introductionwelcome. and congratulations. i am delighted that you could make it. getting here wasn'teasy, i know. in fact, i suspect it was a little tougher than you realize. to begin with, for you to be here now trillions of drifting atoms had somehow to assemblein an intricate and intriguingly obliging manner to create you. it's an arrangement sospecialized and particular that it has never been tried before and will only exist this once. forthe next many years (we hope) these tiny particles will uncomplainingly engage in all thebillions of deft, cooperative efforts necessary to keep you intact and let you experience thesupremely agreeable but generally underappreciated state known as existence. why atoms take this trouble is a bit of a puzzle. being you is not a gratifying experience atthe atomic level. for all their devoted attention, your atoms don't actually care about you indeed, don't even know that you are there. they don't even know that they are there. they aremindless particles, after all, and not even themselves alive. (it is a slightly arresting notionthat if you were to pick yourself apart with tweezers, one atom at a time, you would produce amound of fine atomic dust, none of which had ever been alive but all of which had once beenyou.) yet somehow for the period of your existence they will answer to a single overarchingimpulse: to keep you you. the bad news is that atoms are fickle and their time of devotion is fleeting fleeting indeed.even a long human life adds up to only about 650,000 hours. and when that modestmilestone flashes past, or at some other point thereabouts, for reasons unknown your atomswill shut you down, silently disassemble, and go off to be other things. and that's it for you. still, you may rejoice that it happens at all. generally speaking in the universe it doesn't, sofar as we can tell. this is decidedly odd because the atoms that so liberally and congeniallyflock together to form living things on earth are exactly the same atoms that decline to do itelsewhere. whatever else it may be, at the level of chemistry life is curiously mundane:carbon, hydrogen, oxygen, and nitrogen, a little calcium, a dash of sulfur, a light dusting ofother very ordinary elements nothing you wouldn't find in any ordinary drugstore and that'sall you need. the only thing special about the atoms that make you is that they make you.that is of course the miracle of life. whether or not atoms make life in other corners of the universe, they make plenty else;indeed, they make everything else. without them there would be no water or air or rocks, nostars and planets, no distant gassy clouds or swirling nebulae or any of the other things thatmake the universe so usefully material. atoms are so numerous and necessary that we easilyoverlook that they needn't actually exist at all. there is no law that requires the universe to fillitself with small particles of matter or to produce light and gravity and the other physicalproperties on which our existence hinges. there needn't actually be a universe at all. for thelongest time there wasn't. there were no atoms and no universe for them to float about in.there was nothing nothing at all anywhere. so thank goodness for atoms. but the fact that you have atoms and that they assemble insuch a willing manner is only part of what got you here. to be here now, alive in the twenty first century and smart enough to know it, you also had to be the beneficiary of anextraordinary string of biological good fortune. survival on earth is a surprisingly trickybusiness. of the billions and billions of species of living thing that have existed since thedawn of time, most 99.99 percent are no longer around. life on earth, you see, is not only brief but dismayingly tenuous. it is a curious feature of our existence that we come from aplanet that is very good at promoting life but even better at extinguishing it. the average species on earth lasts for only about four million years, so if you wish to bearound for billions of years, you must be as fickle as the atoms that made you. you must beprepared to change everything about yourself shape, size, color, species affiliation,everything and to do so repeatedly. that's much easier said than done, because the process ofchange is random. to get from \"protoplasmal primordial atomic globule\" (as the gilbert andsullivan song put it) to sentient upright modern human has required you to mutate new traitsover and over in a precisely timely manner for an exceedingly long while. so at variousperiods over the last 3.8 billion years you have abhorred oxygen and then doted on it, grownfins and limbs and jaunty sails, laid eggs, flicked the air with a forked tongue, been sleek,been furry, lived underground, lived in trees, been as big as a deer and as small as a mouse,and a million things more. the tiniest deviation from any of these evolutionary shifts, and youmight now be licking algae from cave walls or lolling walrus like on some stony shore ordisgorging air through a blowhole in the top of your head before diving sixty feet for amouthful of delicious sandworms. not only have you been lucky enough to be attached since time immemorial to a favoredevolutionary line, but you have also been extremely make that miraculously fortunate in yourpersonal ancestry. consider the fact that for 3.8 billion years, a period of time older than theearth's mountains and rivers and oceans, every one of your forebears on both sides has beenattractive enough to find a mate, healthy enough to reproduce, and sufficiently blessed by fateand circumstances to live long enough to do so. not one of your pertinent ancestors wassquashed, devoured, drowned, starved, stranded, stuck fast, untimely wounded, or otherwisedeflected from its life's quest of delivering a tiny charge of genetic material to the rightpartner at the right moment in order to perpetuate the only possible sequence of hereditarycombinations that could result eventually, astoundingly, and all too briefly in you.this is a book about how it happened in particular how we went from there being nothing atall to there being something, and then how a little of that something turned into us, and alsosome of what happened in between and since. that's a great deal to cover, of course, which iswhy the book is called a short history of nearly everything, even though it isn't really. itcouldn't be. but with luck by the time we finish it will feel as if it is. my own starting point, for what it's worth, was an illustrated science book that i had as aclassroom text when i was in fourth or fifth grade. the book was a standard issue 1950sschoolbookbattered, unloved, grimly hefty but near the front it had an illustration that justcaptivated me: a cutaway diagram showing the earth's interior as it would look if you cut intothe planet with a large knife and carefully withdrew a wedge representing about a quarter ofits bulk. it's hard to believe that there was ever a time when i had not seen such an illustrationbefore, but evidently i had not for i clearly remember being transfixed. i suspect, in honesty,my initial interest was based on a private image of streams of unsuspecting eastboundmotorists in the american plains states plunging over the edge of a sudden 4,000 mile highcliff running between central america and the north pole, but gradually my attention did turnin a more scholarly manner to the scientific import of the drawing and the realization that theearth consisted of discrete layers, ending in the center with a glowing sphere of iron andnickel, which was as hot as the surface of the sun, according to the caption, and i rememberthinking with real wonder: \"how do they know that?\" i didn't doubt the correctness of the information for an instant i still tend to trust thepronouncements of scientists in the way i trust those of surgeons, plumbers, and otherpossessors of arcane and privileged information but i couldn't for the life of me conceive how any human mind could work out what spaces thousands of miles below us, that no eye hadever seen and no x ray could penetrate, could look like and be made of. to me that was just amiracle. that has been my position with science ever since. excited, i took the book home that night and opened it before dinner an action that i expectprompted my mother to feel my forehead and ask if i was all right and, starting with the firstpage, i read. and here's the thing. it wasn't exciting at all. it wasn't actually altogether comprehensible.above all, it didn't answer any of the questions that the illustration stirred up in a normalinquiring mind: how did we end up with a sun in the middle of our planet? and if it isburning away down there, why isn't the ground under our feet hot to the touch? and why isn'tthe rest of the interior melting or is it? and when the core at last burns itself out, will some ofthe earth slump into the void, leaving a giant sinkhole on the surface? and how do you knowthis? how did you figure it out? but the author was strangely silent on such details indeed, silent on everything butanticlines, synclines, axial faults, and the like. it was as if he wanted to keep the good stuffsecret by making all of it soberly unfathomable. as the years passed, i began to suspect thatthis was not altogether a private impulse. there seemed to be a mystifying universalconspiracy among textbook authors to make certain the material they dealt with never strayedtoo near the realm of the mildly interesting and was always at least a longdistance phone callfrom the frankly interesting. i now know that there is a happy abundance of science writers who pen the most lucid andthrilling prose timothy ferris, richard fortey, and tim flannery are three that jump out froma single station of the alphabet (and that's not even to mention the late but godlike richardfeynman) but sadly none of them wrote any textbook i ever used. all mine were written bymen (it was always men) who held the interesting notion that everything became clear whenexpressed as a formula and the amusingly deluded belief that the children of america wouldappreciate having chapters end with a section of questions they could mull over in their owntime. so i grew up convinced that science was supremely dull, but suspecting that it needn'tbe, and not really thinking about it at all if i could help it. this, too, became my position for along time. then much later about four or five years ago i was on a long flight across the pacific,staring idly out the window at moonlit ocean, when it occurred to me with a certainuncomfortable forcefulness that i didn't know the first thing about the only planet i was evergoing to live on. i had no idea, for example, why the oceans were salty but the great lakesweren't. didn't have the faintest idea. i didn't know if the oceans were growing more saltywith time or less, and whether ocean salinity levels was something i should be concernedabout or not. (i am very pleased to tell you that until the late 1970s scientists didn't know theanswers to these questions either. they just didn't talk about it very audibly.) and ocean salinity of course represented only the merest sliver of my ignorance. i didn'tknow what a proton was, or a protein, didn't know a quark from a quasar, didn't understandhow geologists could look at a layer of rock on a canyon wall and tell you how old it was,didn't know anything really. i became gripped by a quiet, unwonted urge to know a littleabout these matters and to understand how people figured them out. that to me remained thegreatest of all amazements how scientists work things out. how does anybody know howmuch the earth weighs or how old its rocks are or what really is way down there in thecenter? how can they know how and when the universe started and what it was like when itdid? how do they know what goes on inside an atom? and how, come to that or perhapsabove all can scientists so often seem to know nearly everything but then still can't predict anearthquake or even tell us whether we should take an umbrella with us to the races nextwednesday? so i decided that i would devote a portion of my life three years, as it now turns out toreading books and journals and finding saintly, patient experts prepared to answer a lot ofoutstandingly dumb questions. the idea was to see if it isn't possible to understand andappreciate marvel at, enjoy even the wonder and accomplishments of science at a level thatisn't too technical or demanding, but isn't entirely superficial either. that was my idea and my hope, and that is what the book that follows is intended to be.anyway, we have a great deal of ground to cover and much less than 650,000 hours in whichto do it, so let's begin. part i lost in the cosmos they’re all in the same plane. they’re all going around in the same direction. . . . it’s perfect, you know. it’s gorgeous. it’s almost uncanny.  astronomer geoffrey marcy describing the solar system 1 how to build a universeno matter how hard you try you will never be able to grasp just how tiny, how spatiallyunassuming, is a proton. it is just way too small. a proton is an infinitesimal part of an atom, which is itself of course an insubstantial thing.protons are so small that a little dib of ink like the dot on this i can hold something in theregion of 500,000,000,000 of them, rather more than the number of seconds contained in halfa million years. so protons are exceedingly microscopic, to say the very least. now imagine if you can (and of course you can’t) shrinking one of those protons down to abillionth of its normal size into a space so small that it would make a proton look enormous.now pack into that tiny, tiny space about an ounce of matter. excellent. you are ready to starta universe. i’m assuming of course that you wish to build an inflationary universe. if you’d preferinstead to build a more old fashioned, standard big bang universe, you’ll need additionalmaterials. in fact, you will need to gather up everything there is every last mote and particle ofmatter between here and the edge of creation and squeeze it into a spot so infinitesimallycompact that it has no dimensions at all. it is known as a singularity. in either case, get ready for a really big bang. naturally, you will wish to retire to a safeplace to observe the spectacle. unfortunately, there is nowhere to retire to because outside thesingularity there is no where. when the universe begins to expand, it won’t be spreading outto fill a larger emptiness. the only space that exists is the space it creates as it goes. it is natural but wrong to visualize the singularity as a kind of pregnant dot hanging in adark, boundless void. but there is no space, no darkness. the singularity has no “around”around it. there is no space for it to occupy, no place for it to be. we can’t even ask how longit has been there whether it has just lately popped into being, like a good idea, or whether ithas been there forever, quietly awaiting the right moment. time doesn’t exist. there is no pastfor it to emerge from. and so, from nothing, our universe begins. in a single blinding pulse, a moment of glory much too swift and expansive for any form ofwords, the singularity assumes heavenly dimensions, space beyond conception. in the firstlively second (a second that many cosmologists will devote careers to shaving into ever finerwafers) is produced gravity and the other forces that govern physics. in less than a minute theuniverse is a million billion miles across and growing fast. there is a lot of heat now, tenbillion degrees of it, enough to begin the nuclear reactions that create the lighter elements principally hydrogen and helium, with a dash (about one atom in a hundred million) oflithium. in three minutes, 98 percent of all the matter there is or will ever be has beenproduced. we have a universe. it is a place of the most wondrous and gratifying possibility,and beautiful, too. and it was all done in about the time it takes to make a sandwich. when this moment happened is a matter of some debate. cosmologists have long arguedover whether the moment of creation was 10 billion years ago or twice that or something inbetween. the consensus seems to be heading for a figure of about 13.7 billion years, but thesethings are notoriously difficult to measure, as we shall see further on. all that can really besaid is that at some indeterminate point in the very distant past, for reasons unknown, therecame the moment known to science as t = 0. we were on our way. there is of course a great deal we don’t know, and much of what we think we know wehaven’t known, or thought we’ve known, for long. even the notion of the big bang is quite arecent one. the idea had been kicking around since the 1920s, when georges lemaître, abelgian priest scholar, first tentatively proposed it, but it didn’t really become an activenotion in cosmology until the mid 1960s when two young radio astronomers made anextraordinary and inadvertent discovery. their names were arno penzias and robert wilson. in 1965, they were trying to make useof a large communications antenna owned by bell laboratories at holmdel, new jersey, butthey were troubled by a persistent background noise a steady, steamy hiss that made anyexperimental work impossible. the noise was unrelenting and unfocused. it came from everypoint in the sky, day and night, through every season. for a year the young astronomers dideverything they could think of to track down and eliminate the noise. they tested everyelectrical system. they rebuilt instruments, checked circuits, wiggled wires, dusted plugs.they climbed into the dish and placed duct tape over every seam and rivet. they climbedback into the dish with brooms and scrubbing brushes and carefully swept it clean of whatthey referred to in a later paper as “white dielectric material,” or what is known morecommonly as bird shit. nothing they tried worked. unknown to them, just thirty miles away at princeton university, a team of scientists led byrobert dicke was working on how to find the very thing they were trying so diligently to getrid of. the princeton researchers were pursuing an idea that had been suggested in the 1940sby the russian born astrophysicist george gamow that if you looked deep enough into spaceyou should find some cosmic background radiation left over from the big bang. gamowcalculated that by the time it crossed the vastness of the cosmos, the radiation would reachearth in the form of microwaves. in a more recent paper he had even suggested an instrumentthat might do the job: the bell antenna at holmdel. unfortunately, neither penzias andwilson, nor any of the princeton team, had read gamow’s paper. the noise that penzias and wilson were hearing was, of course, the noise that gamow hadpostulated. they had found the edge of the universe, or at least the visible part of it, 90 billiontrillion miles away. they were “seeing” the first photons the most ancient light in theuniverse though time and distance had converted them to microwaves, just as gamow hadpredicted. in his book the inflationary universe , alan guth provides an analogy that helps toput this finding in perspective. if you think of peering into the depths of the universe as likelooking down from the hundredth floor of the empire state building (with the hundredth floorrepresenting now and street level representing the moment of the big bang), at the time ofwilson and penzias’s discovery the most distant galaxies anyone had ever detected were onabout the sixtieth floor, and the most distant things quasars were on about the twentieth.penzias and wilson’s finding pushed our acquaintance with the visible universe to within halfan inch of the sidewalk. still unaware of what caused the noise, wilson and penzias phoned dicke at princeton anddescribed their problem to him in the hope that he might suggest a solution. dicke realized at once what the two young men had found. “well, boys, we’ve just been scooped,” he told hiscolleagues as he hung up the phone. soon afterward the astrophysical journal published two articles: one by penzias andwilson describing their experience with the hiss, the other by dicke’s team explaining itsnature. although penzias and wilson had not been looking for cosmic background radiation,didn’t know what it was when they had found it, and hadn’t described or interpreted itscharacter in any paper, they received the 1978 nobel prize in physics. the princetonresearchers got only sympathy. according to dennis overbye in lonely hearts of the cosmos, neither penzias nor wilson altogether understood the significance of what they had founduntil they read about it in the new york times . incidentally, disturbance from cosmic background radiation is something we have allexperienced. tune your television to any channel it doesn’t receive, and about 1 percent of thedancing static you see is accounted for by this ancient remnant of the big bang. the next timeyou complain that there is nothing on, remember that you can always watch the birth of theuniverse. although everyone calls it the big bang, many books caution us not to think of it as anexplosion in the conventional sense. it was, rather, a vast, sudden expansion on a whoppingscale. so what caused it? one notion is that perhaps the singularity was the relic of an earlier, collapsed universe that we’re just one of an eternal cycle of expanding and collapsing universes, like the bladderon an oxygen machine. others attribute the big bang to what they call “a false vacuum” or “ascalar field” or “vacuum energy” some quality or thing, at any rate, that introduced ameasure of instability into the nothingness that was. it seems impossible that you could getsomething from nothing, but the fact that once there was nothing and now there is a universeis evident proof that you can. it may be that our universe is merely part of many largeruniverses, some in different dimensions, and that big bangs are going on all the time all overthe place. or it may be that space and time had some other forms altogether before the bigbang forms too alien for us to imagine and that the big bang represents some sort oftransition phase, where the universe went from a form we can’t understand to one we almostcan. “these are very close to religious questions,” dr. andrei linde, a cosmologist atstanford, told the new york times in 2001. the big bang theory isn’t about the bang itself but about what happened after the bang.not long after, mind you. by doing a lot of math and watching carefully what goes on inparticle accelerators, scientists believe they can look back to 10 43seconds after the moment ofcreation, when the universe was still so small that you would have needed a microscope tofind it. we mustn’t swoon over every extraordinary number that comes before us, but it isperhaps worth latching on to one from time to time just to be reminded of their ungraspableand amazing breadth. thus 10 43is 0.0000000000000000000000000000000000000000001, orone 10 million trillion trillion trillionths of a second.**a word on scientific notation: since very large numbers are cumbersome to write and nearly impossible to read, scientistsuse a shorthand involving powers (or multiples) of ten in which, for instance, 10,000,000,000 is written 1010 and 6,500,000becomes 6.5 x 106. the principle is based very simply on multiples of ten: 10 x 10 (or 100) becomes 102; 10 x 10 x 10 (or1,000) is 103; and so on, obviously and indefinitely. the little superscript number signifies the number of zeroes followingthe larger principal number. negative notations provide latter in print (especially essentially a mirror image, with thesuperscript number indicating the number of spaces to the right of the decimal point (so 10 4 means 0.0001). though i salutethe principle, it remains an amazement to me that anyone seeing \"1.4 x 109 km3’ would see at once that that signifies 1.4 most of what we know, or believe we know, about the early moments of the universe isthanks to an idea called inflation theory first propounded in 1979 by a junior particlephysicist, then at stanford, now at mit, named alan guth. he was thirty two years old and,by his own admission, had never done anything much before. he would probably never havehad his great theory except that he happened to attend a lecture on the big bang given bynone other than robert dicke. the lecture inspired guth to take an interest in cosmology, andin particular in the birth of the universe. the eventual result was the inflation theory, which holds that a fraction of a moment afterthe dawn of creation, the universe underwent a sudden dramatic expansion. it inflated ineffect ran away with itself, doubling in size every 10 34seconds. the whole episode may havelasted no more than 10 30seconds that’s one million million million million millionths of asecond but it changed the universe from something you could hold in your hand tosomething at least 10,000,000,000,000,000,000,000,000 times bigger. inflation theoryexplains the ripples and eddies that make our universe possible. without it, there would be noclumps of matter and thus no stars, just drifting gas and everlasting darkness. according to guth’s theory, at one ten millionth of a trillionth of a trillionth of a trillionthof a second, gravity emerged. after another ludicrously brief interval it was joined byelectromagnetism and the strong and weak nuclear forces the stuff of physics. these werejoined an instant later by swarms of elementary particles the stuff of stuff. from nothing atall, suddenly there were swarms of photons, protons, electrons, neutrons, and much else between 1079and 1089of each, according to the standard big bang theory. such quantities are of course ungraspable. it is enough to know that in a single crackinginstant we were endowed with a universe that was vast at least a hundred billion light yearsacross, according to the theory, but possibly any size up to infinite and perfectly arrayed forthe creation of stars, galaxies, and other complex systems. what is extraordinary from our point of view is how well it turned out for us. if theuniverse had formed just a tiny bit differently if gravity were fractionally stronger orweaker, if the expansion had proceeded just a little more slowly or swiftly then there mightnever have been stable elements to make you and me and the ground we stand on. had gravitybeen a trifle stronger, the universe itself might have collapsed like a badly erected tent,without precisely the right values to give it the right dimensions and density and componentparts. had it been weaker, however, nothing would have coalesced. the universe would haveremained forever a dull, scattered void. this is one reason that some experts believe there may have been many other big bangs,perhaps trillions and trillions of them, spread through the mighty span of eternity, and that thereason we exist in this particular one is that this is one we could exist in. as edward p. tryonof columbia university once put it: “in answer to the question of why it happened, i offer themodest proposal that our universe is simply one of those things which happen from time tobillion cubic kilometers, and no less a wonder that they would choose the former over the in a book designed for the generalreader, where the example was found). on the assumption that many general readers are as unmathematical as i am, i will usethem sparingly, though they are occasionally unavoidable, not least in a chapter dealing with things on a cosmic scale. time.” to which adds guth: “although the creation of a universe might be very unlikely,tryon emphasized that no one had counted the failed attempts.” martin rees, britain’s astronomer royal, believes that there are many universes, possibly aninfinite number, each with different attributes, in different combinations, and that we simplylive in one that combines things in the way that allows us to exist. he makes an analogy witha very large clothing store: “if there is a large stock of clothing, you’re not surprised to find asuit that fits. if there are many universes, each governed by a differing set of numbers, therewill be one where there is a particular set of numbers suitable to life. we are in that one.” rees maintains that six numbers in particular govern our universe, and that if any of thesevalues were changed even very slightly things could not be as they are. for example, for theuniverse to exist as it does requires that hydrogen be converted to helium in a precise butcomparatively stately manner specifically, in a way that converts seven one thousandths ofits mass to energy. lower that value very slightly from 0.007 percent to 0.006 percent,say and no transformation could take place: the universe would consist of hydrogen andnothing else. raise the value very slightly to 0.008 percent and bonding would be sowildly prolific that the hydrogen would long since have been exhausted. in either case, withthe slightest tweaking of the numbers the universe as we know and need it would not be here.i should say that everything is just right so far. in the long term, gravity may turn out to be alittle too strong, and one day it may halt the expansion of the universe and bring it collapsingin upon itself, till it crushes itself down into another singularity, possibly to start the wholeprocess over again. on the other hand it may be too weak and the universe will keep racingaway forever until everything is so far apart that there is no chance of material interactions, sothat the universe becomes a place that is inert and dead, but very roomy. the third option isthat gravity is just right “critical density” is the cosmologists’ term for it and that it willhold the universe together at just the right dimensions to allow things to go on indefinitely.cosmologists in their lighter moments sometimes call this the goldilocks effect thateverything is just right. (for the record, these three possible universes are known respectivelyas closed, open, and flat.) now the question that has occurred to all of us at some point is: what would happen if youtraveled out to the edge of the universe and, as it were, put your head through the curtains?where would your head be if it were no longer in the universe? what would you find beyond?the answer, disappointingly, is that you can never get to the edge of the universe. that’s notbecause it would take too long to get there though of course it would but because even ifyou traveled outward and outward in a straight line, indefinitely and pugnaciously, you wouldnever arrive at an outer boundary. instead, you would come back to where you began (atwhich point, presumably, you would rather lose heart in the exercise and give up). the reasonfor this is that the universe bends, in a way we can’t adequately imagine, in conformance witheinstein’s theory of relativity (which we will get to in due course). for the moment it isenough to know that we are not adrift in some large, ever expanding bubble. rather, spacecurves, in a way that allows it to be boundless but finite. space cannot even properly be saidto be expanding because, as the physicist and nobel laureate steven weinberg notes, “solar systems and galaxies are not expanding, and space itself is not expanding.” rather, thegalaxies are rushing apart. it is all something of a challenge to intuition. or as the biologist j.b. s. haldane once famously observed: “the universe is not only queerer than we suppose; itis queerer than we can suppose.” the analogy that is usually given for explaining the curvature of space is to try to imaginesomeone from a universe of flat surfaces, who had never seen a sphere, being brought toearth. no matter how far he roamed across the planet’s surface, he would never find an edge.he might eventually return to the spot where he had started, and would of course be utterlyconfounded to explain how that had happened. well, we are in the same position in space asour puzzled flatlander, only we are flummoxed by a higher dimension. just as there is no place where you can find the edge of the universe, so there is no placewhere you can stand at the center and say: “this is where it all began. this is the centermostpoint of it all.” we are all at the center of it all. actually, we don’t know that for sure; wecan’t prove it mathematically. scientists just assume that we can’t really be the center of theuniverse think what that would imply but that the phenomenon must be the same for allobservers in all places. still, we don’t actually know. for us, the universe goes only as far as light has traveled in the billions of years since theuniverse was formed. this visible universe the universe we know and can talk about is amillion million million million (that’s 1,000,000,000,000,000,000,000,000) miles across. butaccording to most theories the universe at large the meta universe, as it is sometimescalled is vastly roomier still. according to rees, the number of light years to the edge ofthis larger, unseen universe would be written not “with ten zeroes, not even with a hundred,but with millions.” in short, there’s more space than you can imagine already without going tothe trouble of trying to envision some additional beyond. for a long time the big bang theory had one gaping hole that troubled a lot of people namely that it couldn’t begin to explain how we got here. although 98 percent of all thematter that exists was created with the big bang, that matter consisted exclusively of lightgases: the helium, hydrogen, and lithium that we mentioned earlier. not one particle of theheavy stuff so vital to our own being carbon, nitrogen, oxygen, and all the rest emergedfrom the gaseous brew of creation. but and here’s the troubling point to forge these heavyelements, you need the kind of heat and energy of a big bang. yet there has been only onebig bang and it didn’t produce them. so where did they come from? interestingly, the man who found the answer to that question was a cosmologist whoheartily despised the big bang as a theory and coined the term “big bang” sarcastically, as away of mocking it. we’ll get to him shortly, but before we turn to the question of how we gothere, it might be worth taking a few minutes to consider just where exactly “here” is. 2 welcome to the solar systemastronomers these days can do the most amazing things. if someone struck a matchon the moon, they could spot the flare. from the tiniest throbs and wobbles of distant starsthey can infer the size and character and even potential habitability of planets much tooremote to be seen planets so distant that it would take us half a million years in a spaceshipto get there. with their radio telescopes they can capture wisps of radiation so preposterouslyfaint that the total amount of energy collected from outside the solar system by all of themtogether since collecting began (in 1951) is “less than the energy of a single snowflakestriking the ground,” in the words of carl sagan. in short, there isn’t a great deal that goes on in the universe that astronomers can’t findwhen they have a mind to. which is why it is all the more remarkable to reflect that until 1978no one had ever noticed that pluto has a moon. in the summer of that year, a youngastronomer named james christy at the u.s. naval observatory in flagstaff, arizona, wasmaking a routine examination of photographic images of pluto when he saw that there wassomething there something blurry and uncertain but definitely other than pluto. consulting acolleague named robert harrington, he concluded that what he was looking at was a moon.and it wasn’t just any moon. relative to the planet, it was the biggest moon in the solarsystem. this was actually something of a blow to pluto’s status as a planet, which had never beenterribly robust anyway. since previously the space occupied by the moon and the spaceoccupied by pluto were thought to be one and the same, it meant that pluto was much smallerthan anyone had supposed smaller even than mercury. indeed, seven moons in the solarsystem, including our own, are larger. now a natural question is why it took so long for anyone to find a moon in our own solarsystem. the answer is that it is partly a matter of where astronomers point their instrumentsand partly a matter of what their instruments are designed to detect, and partly it’s just pluto.mostly it’s where they point their instruments. in the words of the astronomer clarkchapman: “most people think that astronomers get out at night in observatories and scan theskies. that’s not true. almost all the telescopes we have in the world are designed to peer atvery tiny little pieces of the sky way off in the distance to see a quasar or hunt for black holesor look at a distant galaxy. the only real network of telescopes that scans the skies has beendesigned and built by the military.” we have been spoiled by artists’ renderings into imagining a clarity of resolution thatdoesn’t exist in actual astronomy. pluto in christy’s photograph is faint and fuzzy a piece ofcosmic lint and its moon is not the romantically backlit, crisply delineated companion orbyou would get in a national geographic painting, but rather just a tiny and extremelyindistinct hint of additional fuzziness. such was the fuzziness, in fact, that it took seven yearsfor anyone to spot the moon again and thus independently confirm its existence. one nice touch about christy’s discovery was that it happened in flagstaff, for it was therein 1930 that pluto had been found in the first place. that seminal event in astronomy waslargely to the credit of the astronomer percival lowell. lowell, who came from one of theoldest and wealthiest boston families (the one in the famous ditty about boston being thehome of the bean and the cod, where lowells spoke only to cabots, while cabots spoke onlyto god), endowed the famous observatory that bears his name, but is most indeliblyremembered for his belief that mars was covered with canals built by industrious martians for purposes of conveying water from polar regions to the dry but productive lands nearer theequator. lowell’s other abiding conviction was that there existed, somewhere out beyond neptune,an undiscovered ninth planet, dubbed planet x. lowell based this belief on irregularities hedetected in the orbits of uranus and neptune, and devoted the last years of his life to trying tofind the gassy giant he was certain was out there. unfortunately, he died suddenly in 1916, atleast partly exhausted by his quest, and the search fell into abeyance while lowell’s heirssquabbled over his estate. however, in 1929, partly as a way of deflecting attention awayfrom the mars canal saga (which by now had become a serious embarrassment), the lowellobservatory directors decided to resume the search and to that end hired a young man fromkansas named clyde tombaugh. tombaugh had no formal training as an astronomer, but he was diligent and he was astute,and after a year’s patient searching he somehow spotted pluto, a faint point of light in aglittery firmament. it was a miraculous find, and what made it all the more striking was thatthe observations on which lowell had predicted the existence of a planet beyond neptuneproved to be comprehensively erroneous. tombaugh could see at once that the new planetwas nothing like the massive gasball lowell had postulated, but any reservations he or anyoneelse had about the character of the new planet were soon swept aside in the delirium thatattended almost any big news story in that easily excited age. this was the first american discovered planet, and no one was going to be distracted by the thought that it was really justa distant icy dot. it was named pluto at least partly because the first two letters made amonogram from lowell’s initials. lowell was posthumously hailed everywhere as a genius ofthe first order, and tombaugh was largely forgotten, except among planetary astronomers,who tend to revere him. a few astronomers continue to think there may be a planet x out there a real whopper,perhaps as much as ten times the size of jupiter, but so far out as to be invisible to us. (itwould receive so little sunlight that it would have almost none to reflect.) the idea is that itwouldn’t be a conventional planet like jupiter or saturn it’s much too far away for that;we’re talking perhaps 4.5 trillion miles but more like a sun that never quite made it. moststar systems in the cosmos are binary (double starred), which makes our solitary sun a slightoddity. as for pluto itself, nobody is quite sure how big it is, or what it is made of, what kind ofatmosphere it has, or even what it really is. a lot of astronomers believe it isn’t a planet at all,but merely the largest object so far found in a zone of galactic debris known as the kuiperbelt. the kuiper belt was actually theorized by an astronomer named f. c. leonard in 1930,but the name honors gerard kuiper, a dutch native working in america, who expanded theidea. the kuiper belt is the source of what are known as short period comets those thatcome past pretty regularly of which the most famous is halley’s comet. the more reclusivelong period comets (among them the recent visitors hale bopp and hyakutake) come fromthe much more distant oort cloud, about which more presently. it is certainly true that pluto doesn’t act much like the other planets. not only is it runty andobscure, but it is so variable in its motions that no one can tell you exactly where pluto will bea century hence. whereas the other planets orbit on more or less the same plane, pluto’sorbital path is tipped (as it were) out of alignment at an angle of seventeen degrees, like thebrim of a hat tilted rakishly on someone’s head. its orbit is so irregular that for substantialperiods on each of its lonely circuits around the sun it is closer to us than neptune is. for most of the 1980s and 1990s, neptune was in fact the solar system’s most far flung planet.only on february 11, 1999, did pluto return to the outside lane, there to remain for the next228 years. so if pluto really is a planet, it is certainly an odd one. it is very tiny: just one quarter of 1percent as massive as earth. if you set it down on top of the united states, it would cover notquite half the lower forty eight states. this alone makes it extremely anomalous; it means thatour planetary system consists of four rocky inner planets, four gassy outer giants, and a tiny,solitary iceball. moreover, there is every reason to suppose that we may soon begin to findother even larger icy spheres in the same portion of space. then we will have problems. afterchristy spotted pluto’s moon, astronomers began to regard that section of the cosmos moreattentively and as of early december 2002 had found over six hundred additional trans neptunian objects, or plutinos as they are alternatively called. one, dubbed varuna, is nearlyas big as pluto’s moon. astronomers now think there may be billions of these objects. thedifficulty is that many of them are awfully dark. typically they have an albedo, orreflectiveness, of just 4 percent, about the same as a lump of charcoal and of course theselumps of charcoal are about four billion miles away. and how far is that exactly? it’s almost beyond imagining. space, you see, is justenormous just enormous. let’s imagine, for purposes of edification and entertainment, thatwe are about to go on a journey by rocketship. we won’t go terribly far just to the edge ofour own solar system but we need to get a fix on how big a place space is and what a smallpart of it we occupy. now the bad news, i’m afraid, is that we won’t be home for supper. even at the speed oflight, it would take seven hours to get to pluto. but of course we can’t travel at anything likethat speed. we’ll have to go at the speed of a spaceship, and these are rather more lumbering.the best speeds yet achieved by any human object are those of the voyager 1 and2 spacecraft,which are now flying away from us at about thirty five thousand miles an hour. the reason the voyager craft were launched when they were (in august and september1977) was that jupiter, saturn, uranus, and neptune were aligned in a way that happens onlyonce every 175 years. this enabled the two voyagers to use a “gravity assist” technique inwhich the craft were successively flung from one gassy giant to the next in a kind of cosmicversion of “crack the whip.” even so, it took them nine years to reach uranus and a dozen tocross the orbit of pluto. the good news is that if we wait until january 2006 (which is whennasa’s new horizons spacecraft is tentatively scheduled to depart for pluto) we can takeadvantage of favorable jovian positioning, plus some advances in technology, and get there inonly a decade or so though getting home again will take rather longer, i’m afraid. at allevents, it’s going to be a long trip. now the first thing you are likely to realize is that space is extremely well named and ratherdismayingly uneventful. our solar system may be the liveliest thing for trillions of miles, butall the visible stuff in it the sun, the planets and their moons, the billion or so tumblingrocks of the asteroid belt, comets, and other miscellaneous drifting detritus fills less than atrillionth of the available space. you also quickly realize that none of the maps you have everseen of the solar system were remotely drawn to scale. most schoolroom charts show theplanets coming one after the other at neighborly intervals the outer giants actually castshadows over each other in many illustrations but this is a necessary deceit to get them all on the same piece of paper. neptune in reality isn’t just a little bit beyond jupiter, it’s waybeyond jupiter five times farther from jupiter than jupiter is from us, so far out that itreceives only 3 percent as much sunlight as jupiter. such are the distances, in fact, that it isn’t possible, in any practical terms, to draw the solarsystem to scale. even if you added lots of fold out pages to your textbooks or used a reallylong sheet of poster paper, you wouldn’t come close. on a diagram of the solar system toscale, with earth reduced to about the diameter of a pea, jupiter would be over a thousand feetaway and pluto would be a mile and a half distant (and about the size of a bacterium, so youwouldn’t be able to see it anyway). on the same scale, proxima centauri, our nearest star,would be almost ten thousand miles away. even if you shrank down everything so that jupiterwas as small as the period at the end of this sentence, and pluto was no bigger than amolecule, pluto would still be over thirty five feet away. so the solar system is really quite enormous. by the time we reach pluto, we have come sofar that the sun our dear, warm, skin tanning, life giving sun has shrunk to the size of apinhead. it is little more than a bright star. in such a lonely void you can begin to understandhow even the most significant objects pluto’s moon, for example have escaped attention.in this respect, pluto has hardly been alone. until the voyager expeditions, neptune wasthought to have two moons; voyager found six more. when i was a boy, the solar system wasthought to contain thirty moons. the total now is “at least ninety,” about a third of which havebeen found in just the last ten years. the point to remember, of course, is that when considering the universe at large we don’tactually know what is in our own solar system. now the other thing you will notice as we speed past pluto is that we are speeding pastpluto. if you check your itinerary, you will see that this is a trip to the edge of our solarsystem, and i’m afraid we’re not there yet. pluto may be the last object marked onschoolroom charts, but the system doesn’t end there. in fact, it isn’t even close to endingthere. we won’t get to the solar system’s edge until we have passed through the oort cloud, avast celestial realm of drifting comets, and we won’t reach the oort cloud for another i’m sosorry about this ten thousand years. far from marking the outer edge of the solar system, asthose schoolroom maps so cavalierly imply, pluto is barely one fifty thousandth of the way. of course we have no prospect of such a journey. a trip of 240,000 miles to the moon stillrepresents a very big undertaking for us. a manned mission to mars, called for by the firstpresident bush in a moment of passing giddiness, was quietly dropped when someone workedout that it would cost $450 billion and probably result in the deaths of all the crew (their dnatorn to tatters by high energy solar particles from which they could not be shielded). based on what we know now and can reasonably imagine, there is absolutely no prospectthat any human being will ever visit the edge of our own solar system ever. it is just too far.as it is, even with the hubble telescope, we can’t see even into the oort cloud, so we don’tactually know that it is there. its existence is probable but entirely hypothetical.* about all that can be said with confidence about the oort cloud is that it starts somewherebeyond pluto and stretches some two light years out into the cosmos. the basic unit ofmeasure in the solar system is the astronomical unit, or au, representing the distance from* properly called the opik oort cloud, it is named for the estonian astronomer ernst opik, who hypothesized itsexistence in 1932, and for the dutch astronomer jan oort, who refined the calculations eighteen years later. the sun to the earth. pluto is about forty aus from us, the heart of the oort cloud about fiftythousand. in a word, it is remote. but let’s pretend again that we have made it to the oort cloud. the first thing you mightnotice is how very peaceful it is out here. we’re a long way from anywhere now so far fromour own sun that it’s not even the brightest star in the sky. it is a remarkable thought that thatdistant tiny twinkle has enough gravity to hold all these comets in orbit. it’s not a very strongbond, so the comets drift in a stately manner, moving at only about 220 miles an hour. fromtime to time some of these lonely comets are nudged out of their normal orbit by some slightgravitational perturbation a passing star perhaps. sometimes they are ejected into theemptiness of space, never to be seen again, but sometimes they fall into a long orbit aroundthe sun. about three or four of these a year, known as long period comets, pass through theinner solar system. just occasionally these stray visitors smack into something solid, likeearth. that’s why we’ve come out here now because the comet we have come to see hasjust begun a long fall toward the center of the solar system. it is headed for, of all places,manson, iowa. it is going to take a long time to get there three or four million years atleast so we’ll leave it for now, and return to it much later in the story. so that’s your solar system. and what else is out there, beyond the solar system? well,nothing and a great deal, depending on how you look at it. in the short term, it’s nothing. the most perfect vacuum ever created by humans is not asempty as the emptiness of interstellar space. and there is a great deal of this nothingness untilyou get to the next bit of something. our nearest neighbor in the cosmos, proxima centauri,which is part of the three star cluster known as alpha centauri, is 4.3 light years away, a sissyskip in galactic terms, but that is still a hundred million times farther than a trip to the moon.to reach it by spaceship would take at least twenty five thousand years, and even if you madethe trip you still wouldn’t be anywhere except at a lonely clutch of stars in the middle of avast nowhere. to reach the next landmark of consequence, sirius, would involve another 4.6light years of travel. and so it would go if you tried to star hop your way across the cosmos.just reaching the center of our own galaxy would take far longer than we have existed asbeings. space, let me repeat, is enormous. the average distance between stars out there is 20million million miles. even at speeds approaching those of light, these are fantasticallychallenging distances for any traveling individual. of course, it is possible that alien beingstravel billions of miles to amuse themselves by planting crop circles in wiltshire orfrightening the daylights out of some poor guy in a pickup truck on a lonely road in arizona(they must have teenagers, after all), but it does seem unlikely. still, statistically the probability that there are other thinking beings out there is good.nobody knows how many stars there are in the milky way estimates range from 100 billionor so to perhaps 400 billion and the milky way is just one of 140 billion or so othergalaxies, many of them even larger than ours. in the 1960s, a professor at cornell namedfrank drake, excited by such whopping numbers, worked out a famous equation designed tocalculate the chances of advanced life in the cosmos based on a series of diminishingprobabilities. under drake’s equation you divide the number of stars in a selected portion of the universeby the number of stars that are likely to have planetary systems; divide that by the number ofplanetary systems that could theoretically support life; divide that by the number on whichlife, having arisen, advances to a state of intelligence; and so on. at each such division, thenumber shrinks colossally yet even with the most conservative inputs the number ofadvanced civilizations just in the milky way always works out to be somewhere in themillions. what an interesting and exciting thought. we may be only one of millions of advancedcivilizations. unfortunately, space being spacious, the average distance between any two ofthese civilizations is reckoned to be at least two hundred light years, which is a great dealmore than merely saying it makes it sound. it means for a start that even if these beings knowwe are here and are somehow able to see us in their telescopes, they’re watching light that leftearth two hundred years ago. so they’re not seeing you and me. they’re watching the frenchrevolution and thomas jefferson and people in silk stockings and powdered wigs peoplewho don’t know what an atom is, or a gene, and who make their electricity by rubbing a rodof amber with a piece of fur and think that’s quite a trick. any message we receive from themis likely to begin “dear sire,” and congratulate us on the handsomeness of our horses and ourmastery of whale oil. two hundred light years is a distance so far beyond us as to be, well,just beyond us. so even if we are not really alone, in all practical terms we are. carl sagan calculated thenumber of probable planets in the universe at large at 10 billion trillion a number vastlybeyond imagining. but what is equally beyond imagining is the amount of space throughwhich they are lightly scattered. “if we were randomly inserted into the universe,” saganwrote, “the chances that you would be on or near a planet would be less than one in a billiontrillion trillion.” (that’s 1033, or a one followed by thirty three zeroes.) “worlds are precious.” which is why perhaps it is good news that in february 1999 the international astronomicalunion ruled officially that pluto is a planet. the universe is a big and lonely place. we can dowith all the neighbors we can get. 3 the reverend evans’s universewhen the skies are clear and the moon is not too bright, the reverend robert evans, aquiet and cheerful man, lugs a bulky telescope onto the back deck of his home in the bluemountains of australia, about fifty miles west of sydney, and does an extraordinary thing. helooks deep into the past and finds dying stars. looking into the past is of course the easy part. glance at the night sky and what you see ishistory and lots of it the stars not as they are now but as they were when their light leftthem. for all we know, the north star, our faithful companion, might actually have burnedout last january or in 1854 or at any time since the early fourteenth century and news of it justhasn’t reached us yet. the best we can say can ever say is that it was still burning on thisdate 680 years ago. stars die all the time. what bob evans does better than anyone else whohas ever tried is spot these moments of celestial farewell. by day, evans is a kindly and now semiretired minister in the uniting church in australia,who does a bit of freelance work and researches the history of nineteenth century religiousmovements. but by night he is, in his unassuming way, a titan of the skies. he huntssupernovae. supernovae occur when a giant star, one much bigger than our own sun, collapses and thenspectacularly explodes, releasing in an instant the energy of a hundred billion suns, burningfor a time brighter than all the stars in its galaxy. “it’s like a trillion hydrogen bombs going offat once,” says evans. if a supernova explosion happened within five hundred light years of us,we would be goners, according to evans “it would wreck the show,” as he cheerfully puts it.but the universe is vast, and supernovae are normally much too far away to harm us. in fact,most are so unimaginably distant that their light reaches us as no more than the faintesttwinkle. for the month or so that they are visible, all that distinguishes them from the otherstars in the sky is that they occupy a point of space that wasn’t filled before. it is theseanomalous, very occasional pricks in the crowded dome of the night sky that the reverendevans finds. to understand what a feat this is, imagine a standard dining room table covered in a blacktablecloth and someone throwing a handful of salt across it. the scattered grains can bethought of as a galaxy. now imagine fifteen hundred more tables like the first one enough tofill a wal mart parking lot, say, or to make a single line two miles long each with a randomarray of salt across it. now add one grain of salt to any table and let bob evans walk amongthem. at a glance he will spot it. that grain of salt is the supernova. evans’s is a talent so exceptional that oliver sacks, in an anthropologist on mars, devotesa passage to him in a chapter on autistic savants quickly adding that “there is no suggestionthat he is autistic.” evans, who has not met sacks, laughs at the suggestion that he might beeither autistic or a savant, but he is powerless to explain quite where his talent comes from. “i just seem to have a knack for memorizing star fields,” he told me, with a franklyapologetic look, when i visited him and his wife, elaine, in their picture book bungalow on atranquil edge of the village of hazelbrook, out where sydney finally ends and the boundlessaustralian bush begins. “i’m not particularly good at other things,” he added. “i don’tremember names well.” “or where he’s put things,” called elaine from the kitchen. he nodded frankly again and grinned, then asked me if i’d like to see his telescope. i hadimagined that evans would have a proper observatory in his backyard a scaled downversion of a mount wilson or palomar, with a sliding domed roof and a mechanized chair thatwould be a pleasure to maneuver. in fact, he led me not outside but to a crowded storeroomoff the kitchen where he keeps his books and papers and where his telescope a whitecylinder that is about the size and shape of a household hot water tank rests in a homemade,swiveling plywood mount. when he wishes to observe, he carries them in two trips to a smalldeck off the kitchen. between the overhang of the roof and the feathery tops of eucalyptustrees growing up from the slope below, he has only a letter box view of the sky, but he says itis more than good enough for his purposes. and there, when the skies are clear and the moonnot too bright, he finds his supernovae. the term supernova was coined in the 1930s by a memorably odd astrophysicist namedfritz zwicky. born in bulgaria and raised in switzerland, zwicky came to the californiainstitute of technology in the 1920s and there at once distinguished himself by his abrasivepersonality and erratic talents. he didn’t seem to be outstandingly bright, and many of hiscolleagues considered him little more than “an irritating buffoon.” a fitness buff, he wouldoften drop to the floor of the caltech dining hall or other public areas and do one armedpushups to demonstrate his virility to anyone who seemed inclined to doubt it. he wasnotoriously aggressive, his manner eventually becoming so intimidating that his closestcollaborator, a gentle man named walter baade, refused to be left alone with him. amongother things, zwicky accused baade, who was german, of being a nazi, which he was not. onat least one occasion zwicky threatened to kill baade, who worked up the hill at the mountwilson observatory, if he saw him on the caltech campus. but zwicky was also capable of insights of the most startling brilliance. in the early 1930s,he turned his attention to a question that had long troubled astronomers: the appearance in thesky of occasional unexplained points of light, new stars. improbably he wondered if theneutron the subatomic particle that had just been discovered in england by jameschadwick, and was thus both novel and rather fashionable might be at the heart of things. itoccurred to him that if a star collapsed to the sort of densities found in the core of atoms, theresult would be an unimaginably compacted core. atoms would literally be crushed together,their electrons forced into the nucleus, forming neutrons. you would have a neutron star.imagine a million really weighty cannonballs squeezed down to the size of a marble and well, you’re still not even close. the core of a neutron star is so dense that a single spoonfulof matter from it would weigh 200 billion pounds. a spoonful! but there was more. zwickyrealized that after the collapse of such a star there would be a huge amount of energy leftover enough to make the biggest bang in the universe. he called these resultant explosionssupernovae. they would be they are the biggest events in creation. on january 15, 1934, the journal physical review published a very concise abstract of apresentation that had been conducted by zwicky and baade the previous month at stanforduniversity. despite its extreme brevity one paragraph of twenty four lines the abstractcontained an enormous amount of new science: it provided the first reference to supernovaeand to neutron stars; convincingly explained their method of formation; correctly calculatedthe scale of their explosiveness; and, as a kind of concluding bonus, connected supernovaexplosions to the production of a mysterious new phenomenon called cosmic rays, which hadrecently been found swarming through the universe. these ideas were revolutionary to say theleast. neutron stars wouldn’t be confirmed for thirty four years. the cosmic rays notion, though considered plausible, hasn’t been verified yet. altogether, the abstract was, in thewords of caltech astrophysicist kip s. thorne, “one of the most prescient documents in thehistory of physics and astronomy.” interestingly, zwicky had almost no understanding of why any of this would happen.according to thorne, “he did not understand the laws of physics well enough to be able tosubstantiate his ideas.” zwicky’s talent was for big ideas. others baade mostly were leftto do the mathematical sweeping up. zwicky also was the first to recognize that there wasn’t nearly enough visible mass in theuniverse to hold galaxies together and that there must be some other gravitational influence what we now call dark matter. one thing he failed to see was that if a neutron star shrankenough it would become so dense that even light couldn’t escape its immense gravitationalpull. you would have a black hole. unfortunately, zwicky was held in such disdain by mostof his colleagues that his ideas attracted almost no notice. when, five years later, the greatrobert oppenheimer turned his attention to neutron stars in a landmark paper, he made not asingle reference to any of zwicky’s work even though zwicky had been working for years onthe same problem in an office just down the hall. zwicky’s deductions concerning dark matterwouldn’t attract serious attention for nearly four decades. we can only assume that he did alot of pushups in this period. surprisingly little of the universe is visible to us when we incline our heads to the sky. onlyabout 6,000 stars are visible to the naked eye from earth, and only about 2,000 can be seenfrom any one spot. with binoculars the number of stars you can see from a single locationrises to about 50,000, and with a small two inch telescope it leaps to 300,000. with a sixteen inch telescope, such as evans uses, you begin to count not in stars but in galaxies. from hisdeck, evans supposes he can see between 50,000 and 100,000 galaxies, each containing tensof billions of stars. these are of course respectable numbers, but even with so much to take in,supernovae are extremely rare. a star can burn for billions of years, but it dies just once andquickly, and only a few dying stars explode. most expire quietly, like a campfire at dawn. in atypical galaxy, consisting of a hundred billion stars, a supernova will occur on average onceevery two or three hundred years. finding a supernova therefore was a little bit like standingon the observation platform of the empire state building with a telescope and searchingwindows around manhattan in the hope of finding, let us say, someone lighting a twenty first birthday cake. so when a hopeful and softspoken minister got in touch to ask if they had any usable fieldcharts for hunting supernovae, the astronomical community thought he was out of his mind.at the time evans had a ten inch telescope a very respectable size for amateur stargazingbut hardly the sort of thing with which to do serious cosmology and he was proposing tofind one of the universe’s rarer phenomena. in the whole of astronomical history before evansstarted looking in 1980, fewer than sixty supernovae had been found. (at the time i visitedhim, in august of 2001, he had just recorded his thirty fourth visual discovery; a thirty fifthfollowed three months later and a thirty sixth in early 2003.) evans, however, had certain advantages. most observers, like most people generally, are inthe northern hemisphere, so he had a lot of sky largely to himself, especially at first. he alsohad speed and his uncanny memory. large telescopes are cumbersome things, and much oftheir operational time is consumed with being maneuvered into position. evans could swing his little sixteen inch telescope around like a tail gunner in a dogfight, spending no more thana couple of seconds on any particular point in the sky. in consequence, he could observeperhaps four hundred galaxies in an evening while a large professional telescope would belucky to do fifty or sixty. looking for supernovae is mostly a matter of not finding them. from 1980 to 1996 heaveraged two discoveries a year not a huge payoff for hundreds of nights of peering andpeering. once he found three in fifteen days, but another time he went three years withoutfinding any at all. “there is actually a certain value in not finding anything,” he said. “it helps cosmologists towork out the rate at which galaxies are evolving. it’s one of those rare areas where theabsence of evidenceis evidence.” on a table beside the telescope were stacks of photos and papers relevant to his pursuits,and he showed me some of them now. if you have ever looked through popular astronomicalpublications, and at some time you must have, you will know that they are generally full ofrichly luminous color photos of distant nebulae and the like fairy lit clouds of celestial lightof the most delicate and moving splendor. evans’s working images are nothing like that. theyare just blurry black and white photos with little points of haloed brightness. one he showedme depicted a swarm of stars with a trifling flare that i had to put close to my face to see.this, evans told me, was a star in a constellation called fornax from a galaxy known toastronomy as ngc1365. (ngc stands for new general catalogue, where these things arerecorded. once it was a heavy book on someone’s desk in dublin; today, needless to say, it’sa database.) for sixty million silent years, the light from the star’s spectacular demise traveledunceasingly through space until one night in august of 2001 it arrived at earth in the form ofa puff of radiance, the tiniest brightening, in the night sky. it was of course robert evans onhis eucalypt scented hillside who spotted it. “there’s something satisfying, i think,” evans said, “about the idea of light traveling formillions of years through space and just at the right moment as it reaches earth someonelooks at the right bit of sky and sees it. it just seems right that an event of that magnitudeshould be witnessed.” supernovae do much more than simply impart a sense of wonder. they come in severaltypes (one of them discovered by evans) and of these one in particular, known as a iasupernova, is important to astronomy because it always explodes in the same way, with thesame critical mass. for this reason it can be used as a standard candle to measure theexpansion rate of the universe. in 1987 saul perlmutter at the lawrence berkeley lab in california, needing more iasupernovae than visual sightings were providing, set out to find a more systematic method ofsearching for them. perlmutter devised a nifty system using sophisticated computers andcharge coupled devices in essence, really good digital cameras. it automated supernovahunting. telescopes could now take thousands of pictures and let a computer detect thetelltale bright spots that marked a supernova explosion. in five years, with the new technique,perlmutter and his colleagues at berkeley found forty two supernovae. now even amateursare finding supernovae with charge coupled devices. “with ccds you can aim a telescope atthe sky and go watch television,” evans said with a touch of dismay. “it took all the romanceout of it.” i asked him if he was tempted to adopt the new technology. “oh, no,” he said, “i enjoy myway too much. besides” he gave a nod at the photo of his latest supernova and smiled “ican still beat them sometimes.” the question that naturally occurs is “what would it be like if a star exploded nearby?” ournearest stellar neighbor, as we have seen, is alpha centauri, 4.3 light years away. i hadimagined that if there were an explosion there we would have 4.3 years to watch the light ofthis magnificent event spreading across the sky, as if tipped from a giant can. what would itbe like if we had four years and four months to watch an inescapable doom advancing towardus, knowing that when it finally arrived it would blow the skin right off our bones? wouldpeople still go to work? would farmers plant crops? would anyone deliver them to the stores? weeks later, back in the town in new hampshire where i live, i put these questions to johnthorstensen, an astronomer at dartmouth college. “oh no,” he said, laughing. “the news ofsuch an event travels out at the speed of light, but so does the destructiveness, so you’d learnabout it and die from it in the same instant. but don’t worry because it’s not going to happen.” for the blast of a supernova explosion to kill you, he explained, you would have to be“ridiculously close” probably within ten light years or so. “the danger would be varioustypes of radiation cosmic rays and so on.” these would produce fabulous auroras,shimmering curtains of spooky light that would fill the whole sky. this would not be a goodthing. anything potent enough to put on such a show could well blow away themagnetosphere, the magnetic zone high above the earth that normally protects us fromultraviolet rays and other cosmic assaults. without the magnetosphere anyone unfortunateenough to step into sunlight would pretty quickly take on the appearance of, let us say, anovercooked pizza. the reason we can be reasonably confident that such an event won’t happen in our cornerof the galaxy, thorstensen said, is that it takes a particular kind of star to make a supernova inthe first place. a candidate star must be ten to twenty times as massive as our own sun and“we don’t have anything of the requisite size that’s that close. the universe is a mercifully bigplace.” the nearest likely candidate he added, is betelgeuse, whose various sputterings havefor years suggested that something interestingly unstable is going on there. but betelgeuse isfifty thousand light years away. only half a dozen times in recorded history have supernovae been close enough to bevisible to the naked eye. one was a blast in 1054 that created the crab nebula. another, in1604, made a star bright enough to be seen during the day for over three weeks. the mostrecent was in 1987, when a supernova flared in a zone of the cosmos known as the largemagellanic cloud, but that was only barely visible and only in the southern hemisphere andit was a comfortably safe 169,000 light years away. supernovae are significant to us in one other decidedly central way. without them wewouldn’t be here. you will recall the cosmological conundrum with which we ended the firstchapter that the big bang created lots of light gases but no heavy elements. those camelater, but for a very long time nobody could figure out how they came later. the problem wasthat you needed something really hot hotter even than the middle of the hottest stars toforge carbon and iron and the other elements without which we would be distressingly immaterial. supernovae provided the explanation, and it was an english cosmologist almostas singular in manner as fritz zwicky who figured it out. he was a yorkshireman named fred hoyle. hoyle, who died in 2001, was described in anobituary in nature as a “cosmologist and controversialist” and both of those he most certainlywas. he was, according to nature ’s obituary, “embroiled in controversy for most of his life”and “put his name to much rubbish.” he claimed, for instance, and without evidence, that thenatural history museum’s treasured fossil of an archaeopteryx was a forgery along the linesof the piltdown hoax, causing much exasperation to the museum’s paleontologists, who had tospend days fielding phone calls from journalists from all over the world. he also believed thatearth was not only seeded by life from space but also by many of its diseases, such asinfluenza and bubonic plague, and suggested at one point that humans evolved projectingnoses with the nostrils underneath as a way of keeping cosmic pathogens from falling intothem. it was he who coined the term “big bang,” in a moment of facetiousness, for a radiobroadcast in 1952. he pointed out that nothing in our understanding of physics could accountfor why everything, gathered to a point, would suddenly and dramatically begin to expand.hoyle favored a steady state theory in which the universe was constantly expanding andcontinually creating new matter as it went. hoyle also realized that if stars imploded theywould liberate huge amounts of heat 100 million degrees or more, enough to begin togenerate the heavier elements in a process known as nucleosynthesis. in 1957, working withothers, hoyle showed how the heavier elements were formed in supernova explosions. forthis work, w. a. fowler, one of his collaborators, received a nobel prize. hoyle, shamefully,did not. according to hoyle’s theory, an exploding star would generate enough heat to create all thenew elements and spray them into the cosmos where they would form gaseous clouds theinterstellar medium as it is known that could eventually coalesce into new solar systems.with the new theories it became possible at last to construct plausible scenarios for how wegot here. what we now think we know is this: about 4.6 billion years ago, a great swirl of gas and dust some 15 billion miles acrossaccumulated in space where we are now and began to aggregate. virtually all of it 99.9percent of the mass of the solar system went to make the sun. out of the floating materialthat was left over, two microscopic grains floated close enough together to be joined byelectrostatic forces. this was the moment of conception for our planet. all over the inchoatesolar system, the same was happening. colliding dust grains formed larger and larger clumps.eventually the clumps grew large enough to be called planetesimals. as these endlesslybumped and collided, they fractured or split or recombined in endless random permutations,but in every encounter there was a winner, and some of the winners grew big enough todominate the orbit around which they traveled. it all happened remarkably quickly. to grow from a tiny cluster of grains to a baby planetsome hundreds of miles across is thought to have taken only a few tens of thousands of years.in just 200 million years, possibly less, the earth was essentially formed, though still moltenand subject to constant bombardment from all the debris that remained floating about. at this point, about 4.5 billion years ago, an object the size of mars crashed into earth,blowing out enough material to form a companion sphere, the moon. within weeks, it isthought, the flung material had reassembled itself into a single clump, and within a year it had formed into the spherical rock that companions us yet. most of the lunar material, it isthought, came from the earth’s crust, not its core, which is why the moon has so little ironwhile we have a lot. the theory, incidentally, is almost always presented as a recent one, butin fact it was first proposed in the 1940s by reginald daly of harvard. the only recent thingabout it is people paying any attention to it. when earth was only about a third of its eventual size, it was probably already beginning toform an atmosphere, mostly of carbon dioxide, nitrogen, methane, and sulfur. hardly the sortof stuff that we would associate with life, and yet from this noxious stew life formed. carbondioxide is a powerful greenhouse gas. this was a good thing because the sun wassignificantly dimmer back then. had we not had the benefit of a greenhouse effect, the earthmight well have frozen over permanently, and life might never have gotten a toehold. butsomehow life did. for the next 500 million years the young earth continued to be pelted relentlessly bycomets, meteorites, and other galactic debris, which brought water to fill the oceans and thecomponents necessary for the successful formation of life. it was a singularly hostileenvironment and yet somehow life got going. some tiny bag of chemicals twitched andbecame animate. we were on our way. four billion years later people began to wonder how it had all happened. and it is there thatour story next takes us. part ii the size of the earth nature and nature’s laws lay hid in night; god said, let newton be! and all was light.  alexander pope 4 the measure of thingsif you had to select the least convivial scientific field trip of all time, you could certainlydo worse than the french royal academy of sciences’ peruvian expedition of 1735. led by ahydrologist named pierre bouguer and a soldier mathematician named charles marie de lacondamine, it was a party of scientists and adventurers who traveled to peru with the purposeof triangulating distances through the andes. at the time people had lately become infected with a powerful desire to understand theearth to determine how old it was, and how massive, where it hung in space, and how it hadcome to be. the french party’s goal was to help settle the question of the circumference ofthe planet by measuring the length of one degree of meridian (or 1/360 of the distance aroundthe planet) along a line reaching from yarouqui, near quito, to just beyond cuenca in what isnow ecuador, a distance of about two hundred miles.1almost at once things began to go wrong, sometimes spectacularly so. in quito, the visitorssomehow provoked the locals and were chased out of town by a mob armed with stones. soonafter, the expedition’s doctor was murdered in a misunderstanding over a woman. thebotanist became deranged. others died of fevers and falls. the third most senior member ofthe party, a man named pierre godin, ran off with a thirteen year old girl and could not beinduced to return.at one point the group had to suspend work for eight months while la condamine rode off tolima to sort out a problem with their permits. eventually he and bouguer stopped speakingand refused to work together. everywhere the dwindling party went it was met with thedeepest suspicions from officials who found it difficult to believe that a group of frenchscientists would travel halfway around the world to measure the world. that made no sense atall. two and a half centuries later it still seems a reasonable question. why didn’t the frenchmake their measurements in france and save themselves all the bother and discomfort of theirandean adventure?the answer lies partly with the fact that eighteenth century scientists, the french in particular,seldom did things simply if an absurdly demanding alternative was available, and partly witha practical problem that had first arisen with the english astronomer edmond halley manyyears before long before bouguer and la condamine dreamed of going to south america,much less had a reason for doing so.* triangulation, their chosen method, was a popular technique based on the geometric fact that if you know thelength of one side of a triangle and the angles of two corners, you can work out all its other dimensions withoutleaving your chair. suppose, by way of example, that you and i decided we wished to know how far it is to themoon. using triangulation, the first thing we must do is put some distance between us, so let's say for argumentthat you stay in paris and i go to moscow and we both look at the moon at the same time. now if you imagine aline connecting the three principals of this exercise that is, you and i and the moon it forms a triangle. measurethe length of the baseline between you and me and the angles of our two corners and the rest can be simplycalculated. (because the interior angles of a triangle always add up to 180 degrees, if you know the sum of twoof the angles you can instantly calculate the third; and knowing the precise shape of a triangle and the length ofone side tells you the lengths of the other sides.) this was in fact the method use by a greek astronomer,hipparchus of nicaea, in 150 b.c. to work out the moon's distance from earth. at ground level, the principles oftriangulation are the same, except that the triangles don't reach into space but rather are laid side to side on amap. in measuring a degree of meridian, the surveyors would create a sort of chain of triangles marching acrossthe landscape. halley was an exceptional figure. in the course of a long and productive career, he was asea captain, a cartographer, a professor of geometry at the university of oxford, deputycontroller of the royal mint, astronomer royal, and inventor of the deep sea diving bell. hewrote authoritatively on magnetism, tides, and the motions of the planets, and fondly on theeffects of opium. he invented the weather map and actuarial table, proposed methods forworking out the age of the earth and its distance from the sun, even devised a practicalmethod for keeping fish fresh out of season. the one thing he didn’t do, interestingly enough,was discover the comet that bears his name. he merely recognized that the comet he saw in1682 was the same one that had been seen by others in 1456, 1531, and 1607. it didn’tbecome halley’s comet until 1758, some sixteen years after his death. for all his achievements, however, halley’s greatest contribution to human knowledge maysimply have been to take part in a modest scientific wager with two other worthies of his day:robert hooke, who is perhaps best remembered now as the first person to describe a cell, andthe great and stately sir christopher wren, who was actually an astronomer first and architectsecond, though that is not often generally remembered now. in 1683, halley, hooke, andwren were dining in london when the conversation turned to the motions of celestial objects.it was known that planets were inclined to orbit in a particular kind of oval known as anellipse “a very specific and precise curve,” to quote richard feynman but it wasn’tunderstood why. wren generously offered a prize worth forty shillings (equivalent to a coupleof weeks’ pay) to whichever of the men could provide a solution. hooke, who was well known for taking credit for ideas that weren’t necessarily his own,claimed that he had solved the problem already but declined now to share it on the interestingand inventive grounds that it would rob others of the satisfaction of discovering the answer forthemselves. he would instead “conceal it for some time, that others might know how to valueit.” if he thought any more on the matter, he left no evidence of it. halley, however, becameconsumed with finding the answer, to the point that the following year he traveled tocambridge and boldly called upon the university’s lucasian professor of mathematics, isaacnewton, in the hope that he could help. newton was a decidedly odd figure brilliant beyond measure, but solitary, joyless, pricklyto the point of paranoia, famously distracted (upon swinging his feet out of bed in the morninghe would reportedly sometimes sit for hours, immobilized by the sudden rush of thoughts tohis head), and capable of the most riveting strangeness. he built his own laboratory, the firstat cambridge, but then engaged in the most bizarre experiments. once he inserted a bodkin a long needle of the sort used for sewing leather into his eye socket and rubbed it around“betwixt my eye and the bone as near to [the] backside of my eye as i could” just to see whatwould happen. what happened, miraculously, was nothing at least nothing lasting. onanother occasion, he stared at the sun for as long as he could bear, to determine what effect itwould have upon his vision. again he escaped lasting damage, though he had to spend somedays in a darkened room before his eyes forgave him. set atop these odd beliefs and quirky traits, however, was the mind of a supreme genius though even when working in conventional channels he often showed a tendency topeculiarity. as a student, frustrated by the limitations of conventional mathematics, heinvented an entirely new form, the calculus, but then told no one about it for twenty sevenyears. in like manner, he did work in optics that transformed our understanding of light andlaid the foundation for the science of spectroscopy, and again chose not to share the results forthree decades. for all his brilliance, real science accounted for only a part of his interests. at least half hisworking life was given over to alchemy and wayward religious pursuits. these were not meredabblings but wholehearted devotions. he was a secret adherent of a dangerously hereticalsect called arianism, whose principal tenet was the belief that there had been no holy trinity(slightly ironic since newton’s college at cambridge was trinity). he spent endless hoursstudying the floor plan of the lost temple of king solomon in jerusalem (teaching himselfhebrew in the process, the better to scan original texts) in the belief that it held mathematicalclues to the dates of the second coming of christ and the end of the world. his attachment toalchemy was no less ardent. in 1936, the economist john maynard keynes bought a trunk ofnewton’s papers at auction and discovered with astonishment that they were overwhelminglypreoccupied not with optics or planetary motions, but with a single minded quest to turn basemetals into precious ones. an analysis of a strand of newton’s hair in the 1970s found itcontained mercury an element of interest to alchemists, hatters, and thermometer makersbut almost no one else at a concentration some forty times the natural level. it is perhapslittle wonder that he had trouble remembering to rise in the morning. quite what halley expected to get from him when he made his unannounced visit in august1684 we can only guess. but thanks to the later account of a newton confidant, abrahamdemoivre, we do have a record of one of science’s most historic encounters: in 1684 dr halley came to visit at cambridge [and] after they had some time together the drasked him what he thought the curve would be that would be described by the planets supposing the force of attraction toward the sun to be reciprocal to the square of their distance from it.this was a reference to a piece of mathematics known as the inverse square law, which halleywas convinced lay at the heart of the explanation, though he wasn’t sure exactly how. sr isaac replied immediately that it would be an [ellipse]. the doctor, struck with joy & amazement, asked him how he knew it. ‘why,’ saith he, ‘i have calculated it,’ whereupon drhalley asked him for his calculation without farther delay, srisaac looked among his papers but could not find it. this was astounding like someone saying he had found a cure for cancer but couldn’tremember where he had put the formula. pressed by halley, newton agreed to redo thecalculations and produce a paper. he did as promised, but then did much more. he retired fortwo years of intensive reflection and scribbling, and at length produced his masterwork: thephilosophiae naturalis principia mathematica or mathematical principles of naturalphilosophy, better known as the principia . once in a great while, a few times in history, a human mind produces an observation soacute and unexpected that people can’t quite decide which is the more amazing the fact orthe thinking of it. principia was one of those moments. it made newton instantly famous. for the rest of his life he would be draped with plaudits and honors, becoming, among much else,the first person in britain knighted for scientific achievement. even the great germanmathematician gottfried von leibniz, with whom newton had a long, bitter fight over priorityfor the invention of the calculus, thought his contributions to mathematics equal to all theaccumulated work that had preceded him. “nearer the gods no mortal may approach,” wrotehalley in a sentiment that was endlessly echoed by his contemporaries and by many otherssince. although the principia has been called “one of the most inaccessible books ever written”(newton intentionally made it difficult so that he wouldn’t be pestered by mathematical“smatterers,” as he called them), it was a beacon to those who could follow it. it not onlyexplained mathematically the orbits of heavenly bodies, but also identified the attractive forcethat got them moving in the first place gravity. suddenly every motion in the universe madesense. at principia ’s heart were newton’s three laws of motion (which state, very baldly, that athing moves in the direction in which it is pushed; that it will keep moving in a straight lineuntil some other force acts to slow or deflect it; and that every action has an opposite andequal reaction) and his universal law of gravitation. this states that every object in theuniverse exerts a tug on every other. it may not seem like it, but as you sit here now you arepulling everything around you walls, ceiling, lamp, pet cat toward you with your own little(indeed, very little) gravitational field. and these things are also pulling on you. it wasnewton who realized that the pull of any two objects is, to quote feynman again,“proportional to the mass of each and varies inversely as the square of the distance betweenthem.” put another way, if you double the distance between two objects, the attractionbetween them becomes four times weaker. this can be expressed with the formula f = gmm r2which is of course way beyond anything that most of us could make practical use of, but atleast we can appreciate that it is elegantly compact. a couple of brief multiplications, a simpledivision, and, bingo, you know your gravitational position wherever you go. it was the firstreally universal law of nature ever propounded by a human mind, which is why newton isregarded with such universal esteem. principia’s production was not without drama. to halley’s horror, just as work wasnearing completion newton and hooke fell into dispute over the priority for the inversesquare law and newton refused to release the crucial third volume, without which the firsttwo made little sense. only with some frantic shuttle diplomacy and the most liberalapplications of flattery did halley manage finally to extract the concluding volume from theerratic professor. halley’s traumas were not yet quite over. the royal society had promised to publish thework, but now pulled out, citing financial embarrassment. the year before the society hadbacked a costly flop called the history of fishes , and they now suspected that the market fora book on mathematical principles would be less than clamorous. halley, whose means werenot great, paid for the book’s publication out of his own pocket. newton, as was his custom,contributed nothing. to make matters worse, halley at this time had just accepted a positionas the society’s clerk, and he was informed that the society could no longer afford to provide him with a promised salary of £50 per annum. he was to be paid instead in copies of thehistory of fishes . newton’s laws explained so many things the slosh and roll of ocean tides, the motions ofplanets, why cannonballs trace a particular trajectory before thudding back to earth, why wearen’t flung into space as the planet spins beneath us at hundreds of miles an hour2 that ittook a while for all their implications to seep in. but one revelation became almostimmediately controversial. this was the suggestion that the earth is not quite round. according to newton’s theory,the centrifugal force of the earth’s spin should result in a slight flattening at the poles and abulging at the equator, which would make the planet slightly oblate. that meant that thelength of a degree wouldn’t be the same in italy as it was in scotland. specifically, the lengthwould shorten as you moved away from the poles. this was not good news for those peoplewhose measurements of the earth were based on the assumption that the earth was a perfectsphere, which was everyone. for half a century people had been trying to work out the size of the earth, mostly bymaking very exacting measurements. one of the first such attempts was by an englishmathematician named richard norwood. as a young man norwood had traveled to bermudawith a diving bell modeled on halley’s device, intending to make a fortune scooping pearlsfrom the seabed. the scheme failed because there were no pearls and anyway norwood’s belldidn’t work, but norwood was not one to waste an experience. in the early seventeenthcentury bermuda was well known among ships’ captains for being hard to locate. theproblem was that the ocean was big, bermuda small, and the navigational tools for dealingwith this disparity hopelessly inadequate. there wasn’t even yet an agreed length for anautical mile. over the breadth of an ocean the smallest miscalculations would becomemagnified so that ships often missed bermuda sized targets by dismaying margins. norwood,whose first love was trigonometry and thus angles, decided to bring a little mathematical rigorto navigation and to that end he determined to calculate the length of a degree. starting with his back against the tower of london, norwood spent two devoted yearsmarching 208 miles north to york, repeatedly stretching and measuring a length of chain ashe went, all the while making the most meticulous adjustments for the rise and fall of the landand the meanderings of the road. the final step was to measure the angle of the sun at york atthe same time of day and on the same day of the year as he had made his first measurement inlondon. from this, he reasoned he could determine the length of one degree of the earth’smeridian and thus calculate the distance around the whole. it was an almost ludicrouslyambitious undertaking a mistake of the slightest fraction of a degree would throw the wholething out by miles but in fact, as norwood proudly declaimed, he was accurate to “within ascantling” or, more precisely, to within about six hundred yards. in metric terms, his figureworked out at 110.72 kilometers per degree of arc. in 1637, norwood’s masterwork of navigation, the seaman’s practice , was published andfound an immediate following. it went through seventeen editions and was still in printtwenty five years after his death. norwood returned to bermuda with his family, becoming a2 how fast you are spinning depends on where you are. the speed of the earth’s spin varies from a little over1,000 miles an hour at the equator to 0 at the poles. successful planter and devoting his leisure hours to his first love, trigonometry. he survivedthere for thirty eight years and it would be pleasing to report that he passed this span inhappiness and adulation. in fact, he didn’t. on the crossing from england, his two young sonswere placed in a cabin with the reverend nathaniel white, and somehow so successfullytraumatized the young vicar that he devoted much of the rest of his career to persecutingnorwood in any small way he could think of. norwood’s two daughters brought their father additional pain by making poor marriages.one of the husbands, possibly incited by the vicar, continually laid small charges againstnorwood in court, causing him much exasperation and necessitating repeated trips acrossbermuda to defend himself. finally in the 1650s witch trials came to bermuda and norwoodspent his final years in severe unease that his papers on trigonometry, with their arcanesymbols, would be taken as communications with the devil and that he would be treated to adreadful execution. so little is known of norwood that it may in fact be that he deserved hisunhappy declining years. what is certainly true is that he got them. meanwhile, the momentum for determining the earth’s circumference passed to france.there, the astronomer jean picard devised an impressively complicated method oftriangulation involving quadrants, pendulum clocks, zenith sectors, and telescopes (forobserving the motions of the moons of jupiter). after two years of trundling and triangulatinghis way across france, in 1669 he announced a more accurate measure of 110.46 kilometersfor one degree of arc. this was a great source of pride for the french, but it was predicated onthe assumption that the earth was a perfect sphere which newton now said it was not. to complicate matters, after picard’s death the father and son team of giovanni andjacques cassini repeated picard’s experiments over a larger area and came up with results thatsuggested that the earth was fatter not at the equator but at the poles that newton, in otherwords, was exactly wrong. it was this that prompted the academy of sciences to dispatchbouguer and la condamine to south america to take new measurements. they chose the andes because they needed to measure near the equator, to determine ifthere really was a difference in sphericity there, and because they reasoned that mountainswould give them good sightlines. in fact, the mountains of peru were so constantly lost incloud that the team often had to wait weeks for an hour’s clear surveying. on top of that, theyhad selected one of the most nearly impossible terrains on earth. peruvians refer to theirlandscape as muy accidentado  “much accidented” and this it most certainly is. thefrench had not only to scale some of the world’s most challenging mountains mountainsthat defeated even their mules but to reach the mountains they had to ford wild rivers, hacktheir way through jungles, and cross miles of high, stony desert, nearly all of it uncharted andfar from any source of supplies. but bouguer and la condamine were nothing if nottenacious, and they stuck to the task for nine and a half long, grim, sun blistered years.shortly before concluding the project, they received word that a second french team, takingmeasurements in northern scandinavia (and facing notable discomforts of their own, fromsquelching bogs to dangerous ice floes), had found that a degree was in fact longer near thepoles, as newton had promised. the earth was forty three kilometers stouter when measuredequatorially than when measured from top to bottom around the poles. bouguer and la condamine thus had spent nearly a decade working toward a result theydidn’t wish to find only to learn now that they weren’t even the first to find it. listlessly, they completed their survey, which confirmed that the first french team was correct. then, still notspeaking, they returned to the coast and took separate ships home. something else conjectured by newton in the principia was that a plumb bob hung near amountain would incline very slightly toward the mountain, affected by the mountain’sgravitational mass as well as by the earth’s. this was more than a curious fact. if youmeasured the deflection accurately and worked out the mass of the mountain, you couldcalculate the universal gravitational constant that is, the basic value of gravity, known asg and along with it the mass of the earth. bouguer and la condamine had tried this on peru’s mount chimborazo, but had beendefeated by both the technical difficulties and their own squabbling, and so the notion laydormant for another thirty years until resurrected in england by nevil maskelyne, theastronomer royal. in dava sobel’s popular book longitude, maskelyne is presented as a ninnyand villain for failing to appreciate the brilliance of the clockmaker john harrison, and thismay be so, but we are indebted to him in other ways not mentioned in her book, not least forhis successful scheme to weigh the earth. maskelyne realized that the nub of the problem laywith finding a mountain of sufficiently regular shape to judge its mass. at his urging, the royal society agreed to engage a reliable figure to tour the british islesto see if such a mountain could be found. maskelyne knew just such a person theastronomer and surveyor charles mason. maskelyne and mason had become friends elevenyears earlier while engaged in a project to measure an astronomical event of great importance:the passage of the planet venus across the face of the sun. the tireless edmond halley hadsuggested years before that if you measured one of these passages from selected points on theearth, you could use the principles of triangulation to work out the distance to the sun, andfrom that calibrate the distances to all the other bodies in the solar system. unfortunately, transits of venus, as they are known, are an irregular occurrence. theycome in pairs eight years apart, but then are absent for a century or more, and there were nonein halley’s lifetime.3 but the idea simmered and when the next transit came due in 1761,nearly two decades after halley’s death, the scientific world was ready indeed, more readythan it had been for an astronomical event before. with the instinct for ordeal that characterized the age, scientists set off for more than ahundred locations around the globe to siberia, china, south africa, indonesia, and thewoods of wisconsin, among many others. france dispatched thirty two observers, britaineighteen more, and still others set out from sweden, russia, italy, germany, ireland, andelsewhere. it was history’s first cooperative international scientific venture, and almost everywhere itran into problems. many observers were waylaid by war, sickness, or shipwreck. others madetheir destinations but opened their crates to find equipment broken or warped by tropical heat.once again the french seemed fated to provide the most memorably unlucky participants.jean chappe spent months traveling to siberia by coach, boat, and sleigh, nursing his delicateinstruments over every perilous bump, only to find the last vital stretch blocked by swollen3 the next transit will be on june 8, 2004, with a second in 2012. there were none in the twentieth century. rivers, the result of unusually heavy spring rains, which the locals were swift to blame on himafter they saw him pointing strange instruments at the sky. chappe managed to escape withhis life, but with no useful measurements. unluckier still was guillaume le gentil, whose experiences are wonderfully summarizedby timothy ferris in coming of age in the milky way . le gentil set off from france a yearahead of time to observe the transit from india, but various setbacks left him still at sea on theday of the transit just about the worst place to be since steady measurements wereimpossible on a pitching ship. undaunted, le gentil continued on to india to await the next transit in 1769. with eightyears to prepare, he erected a first rate viewing station, tested and retested his instruments,and had everything in a state of perfect readiness. on the morning of the second transit, june4, 1769, he awoke to a fine day, but, just as venus began its pass, a cloud slid in front of thesun and remained there for almost exactly the duration of the transit: three hours, fourteenminutes, and seven seconds. stoically, le gentil packed up his instruments and set off for the nearest port, but en routehe contracted dysentery and was laid up for nearly a year. still weakened, he finally made itonto a ship. it was nearly wrecked in a hurricane off the african coast. when at last hereached home, eleven and a half years after setting off, and having achieved nothing, hediscovered that his relatives had had him declared dead in his absence and hadenthusiastically plundered his estate. in comparison, the disappointments experienced by britain’s eighteen scattered observerswere mild. mason found himself paired with a young surveyor named jeremiah dixon andapparently they got along well, for they formed a lasting partnership. their instructions wereto travel to sumatra and chart the transit there, but after just one night at sea their ship wasattacked by a french frigate. (although scientists were in an internationally cooperativemood, nations weren’t.) mason and dixon sent a note to the royal society observing that itseemed awfully dangerous on the high seas and wondering if perhaps the whole thingoughtn’t to be called off. in reply they received a swift and chilly rebuke, noting that they hadalready been paid, that the nation and scientific community were counting on them, and thattheir failure to proceed would result in the irretrievable loss of their reputations. chastened,they sailed on, but en route word reached them that sumatra had fallen to the french and sothey observed the transit inconclusively from the cape of good hope. on the way home theystopped on the lonely atlantic outcrop of st. helena, where they met maskelyne, whoseobservations had been thwarted by cloud cover. mason and maskelyne formed a solidfriendship and spent several happy, and possibly even mildly useful, weeks charting tidalflows. soon afterward, maskelyne returned to england where he became astronomer royal, andmason and dixon now evidently more seasoned set off for four long and often perilousyears surveying their way through 244 miles of dangerous american wilderness to settle aboundary dispute between the estates of william penn and lord baltimore and theirrespective colonies of pennsylvania and maryland. the result was the famous mason anddixon line, which later took on symbolic importance as the dividing line between the slaveand free states. (although the line was their principal task, they also contributed severalastronomical surveys, including one of the century’s most accurate measurements of a degree of meridian an achievement that brought them far more acclaim in england than the settlingof a boundary dispute between spoiled aristocrats.) back in europe, maskelyne and his counterparts in germany and france were forced to theconclusion that the transit measurements of 1761 were essentially a failure. one of theproblems, ironically, was that there were too many observations, which when broughttogether often proved contradictory and impossible to resolve. the successful charting of avenusian transit fell instead to a little known yorkshire born sea captain named james cook,who watched the 1769 transit from a sunny hilltop in tahiti, and then went on to chart andclaim australia for the british crown. upon his return there was now enough information forthe french astronomer joseph lalande to calculate that the mean distance from the earth tothe sun was a little over 150 million kilometers. (two further transits in the nineteenthcentury allowed astronomers to put the figure at 149.59 million kilometers, where it hasremained ever since. the precise distance, we now know, is 149.597870691 millionkilometers.) the earth at last had a position in space. as for mason and dixon, they returned to england as scientific heroes and, for reasonsunknown, dissolved their partnership. considering the frequency with which they turn up atseminal events in eighteenth century science, remarkably little is known about either man. nolikenesses exist and few written references. of dixon the dictionary of national biographynotes intriguingly that he was “said to have been born in a coal mine,” but then leaves it to thereader’s imagination to supply a plausible explanatory circumstance, and adds that he died atdurham in 1777. apart from his name and long association with mason, nothing more isknown. mason is only slightly less shadowy. we know that in 1772, at maskelyne’s behest, heaccepted the commission to find a suitable mountain for the gravitational deflectionexperiment, at length reporting back that the mountain they needed was in the central scottishhighlands, just above loch tay, and was called schiehallion. nothing, however, wouldinduce him to spend a summer surveying it. he never returned to the field again. his nextknown movement was in 1786 when, abruptly and mysteriously, he turned up in philadelphiawith his wife and eight children, apparently on the verge of destitution. he had not been backto america since completing his survey there eighteen years earlier and had no known reasonfor being there, or any friends or patrons to greet him. a few weeks later he was dead. with mason refusing to survey the mountain, the job fell to maskelyne. so for four monthsin the summer of 1774, maskelyne lived in a tent in a remote scottish glen and spent his daysdirecting a team of surveyors, who took hundreds of measurements from every possibleposition. to find the mass of the mountain from all these numbers required a great deal oftedious calculating, for which a mathematician named charles hutton was engaged. thesurveyors had covered a map with scores of figures, each marking an elevation at some pointon or around the mountain. it was essentially just a confusing mass of numbers, but huttonnoticed that if he used a pencil to connect points of equal height, it all became much moreorderly. indeed, one could instantly get a sense of the overall shape and slope of the mountain.he had invented contour lines. extrapolating from his schiehallion measurements, hutton calculated the mass of the earthat 5,000 million million tons, from which could reasonably be deduced the masses of all theother major bodies in the solar system, including the sun. so from this one experiment welearned the masses of the earth, the sun, the moon, the other planets and their moons, and gotcontour lines into the bargain not bad for a summer’s work. not everyone was satisfied with the results, however. the shortcoming of the schiehallionexperiment was that it was not possible to get a truly accurate figure without knowing theactual density of the mountain. for convenience, hutton had assumed that the mountain hadthe same density as ordinary stone, about 2.5 times that of water, but this was little more thanan educated guess. one improbable seeming person who turned his mind to the matter was a country parsonnamed john michell, who resided in the lonely yorkshire village of thornhill. despite hisremote and comparatively humble situation, michell was one of the great scientific thinkers ofthe eighteenth century and much esteemed for it. among a great deal else, he perceived the wavelike nature of earthquakes, conducted muchoriginal research into magnetism and gravity, and, quite extraordinarily, envisioned thepossibility of black holes two hundred years before anyone else a leap of intuitive deductionthat not even newton could make. when the german born musician william herscheldecided his real interest in life was astronomy, it was michell to whom he turned forinstruction in making telescopes, a kindness for which planetary science has been in his debtever since.4 but of all that michell accomplished, nothing was more ingenious or had greater impactthan a machine he designed and built for measuring the mass of the earth. unfortunately, hedied before he could conduct the experiments and both the idea and the necessary equipmentwere passed on to a brilliant but magnificently retiring london scientist named henrycavendish. cavendish is a book in himself. born into a life of sumptuous privilege his grandfatherswere dukes, respectively, of devonshire and kent he was the most gifted english scientistof his age, but also the strangest. he suffered, in the words of one of his few biographers,from shyness to a “degree bordering on disease.” any human contact was for him a source ofthe deepest discomfort.once he opened his door to find an austrian admirer, freshly arrived from vienna, on thefront step. excitedly the austrian began to babble out praise. for a few moments cavendishreceived the compliments as if they were blows from a blunt object and then, unable to takeany more, fled down the path and out the gate, leaving the front door wide open. it was somehours before he could be coaxed back to the property. even his housekeeper communicatedwith him by letter.although he did sometimes venture into society he was particularly devoted to the weeklyscientific soirées of the great naturalist sir joseph banks it was always made clear to theother guests that cavendish was on no account to be approached or even looked at. thosewho sought his views were advised to wander into his vicinity as if by accident and to “talk as4 in 1781 herschel became the first person in the modern era to discover a planet. he wanted to call it george,after the british monarch, but was overruled. instead it became uranus. it were into vacancy.” if their remarks were scientifically worthy they might receive amumbled reply, but more often than not they would hear a peeved squeak (his voice appearsto have been high pitched) and turn to find an actual vacancy and the sight of cavendishfleeing for a more peaceful corner. his wealth and solitary inclinations allowed him to turn his house in clapham into a largelaboratory where he could range undisturbed through every corner of the physical sciences electricity, heat, gravity, gases, anything to do with the composition of matter. the secondhalf of the eighteenth century was a time when people of a scientific bent grew intenselyinterested in the physical properties of fundamental things gases and electricity inparticular and began seeing what they could do with them, often with more enthusiasm thansense. in america, benjamin franklin famously risked his life by flying a kite in an electricalstorm. in france, a chemist named pilatre de rozier tested the flammability of hydrogen bygulping a mouthful and blowing across an open flame, proving at a stroke that hydrogen isindeed explosively combustible and that eyebrows are not necessarily a permanent feature ofone’s face. cavendish, for his part, conducted experiments in which he subjected himself tograduated jolts of electrical current, diligently noting the increasing levels of agony until hecould keep hold of his quill, and sometimes his consciousness, no longer. in the course of a long life cavendish made a string of signal discoveries among muchelse he was the first person to isolate hydrogen and the first to combine hydrogen and oxygento form water but almost nothing he did was entirely divorced from strangeness. to thecontinuing exasperation of his fellow scientists, he often alluded in published work to theresults of contingent experiments that he had not told anyone about. in his secretiveness hedidn’t merely resemble newton, but actively exceeded him. his experiments with electricalconductivity were a century ahead of their time, but unfortunately remained undiscovereduntil that century had passed. indeed the greater part of what he did wasn’t known until thelate nineteenth century when the cambridge physicist james clerk maxwell took on the taskof editing cavendish’s papers, by which time credit had nearly always been given to others. among much else, and without telling anyone, cavendish discovered or anticipated the lawof the conservation of energy, ohm’s law, dalton’s law of partial pressures, richter’s lawof reciprocal proportions, charles’s law of gases, and the principles of electricalconductivity. that’s just some of it. according to the science historian j. g. crowther, he alsoforeshadowed “the work of kelvin and g. h. darwin on the effect of tidal friction on slowingthe rotation of the earth, and larmor’s discovery, published in 1915, on the effect of localatmospheric cooling . . . the work of pickering on freezing mixtures, and some of the work ofrooseboom on heterogeneous equilibria.” finally, he left clues that led directly to thediscovery of the group of elements known as the noble gases, some of which are so elusivethat the last of them wasn’t found until 1962. but our interest here is in cavendish’s lastknown experiment when in the late summer of 1797, at the age of sixty seven, he turned hisattention to the crates of equipment that had been left to him evidently out of simplescientific respect by john michell. when assembled, michell’s apparatus looked like nothing so much as an eighteenth century version of a nautilus weight training machine. it incorporated weights,counterweights, pendulums, shafts, and torsion wires. at the heart of the machine were two350 pound lead balls, which were suspended beside two smaller spheres. the idea was tomeasure the gravitational deflection of the smaller spheres by the larger ones, which would allow the first measurement of the elusive force known as the gravitational constant, and fromwhich the weight (strictly speaking, the mass)5 of the earth could be deduced. because gravity holds planets in orbit and makes falling objects land with a bang, we tendto think of it as a powerful force, but it is not really. it is only powerful in a kind of collectivesense, when one massive object, like the sun, holds on to another massive object, like theearth. at an elemental level gravity is extraordinarily unrobust. each time you pick up a bookfrom a table or a dime from the floor you effortlessly overcome the combined gravitationalexertion of an entire planet. what cavendish was trying to do was measure gravity at thisextremely featherweight level. delicacy was the key word. not a whisper of disturbance could be allowed into the roomcontaining the apparatus, so cavendish took up a position in an adjoining room and made hisobservations with a telescope aimed through a peephole. the work was incredibly exactingand involved seventeen delicate, interconnected measurements, which together took nearly ayear to complete. when at last he had finished his calculations, cavendish announced that theearth weighed a little over 13,000,000,000,000,000,000,000 pounds, or six billion trillionmetric tons, to use the modern measure. (a metric ton is 1,000 kilograms or 2,205 pounds.) today, scientists have at their disposal machines so precise they can detect the weight of asingle bacterium and so sensitive that readings can be disturbed by someone yawning seventy five feet away, but they have not significantly improved on cavendish’s measurements of1797. the current best estimate for earth’s weight is 5.9725 billion trillion metric tons, adifference of only about 1 percent from cavendish’s finding. interestingly, all of this merelyconfirmed estimates made by newton 110 years before cavendish without any experimentalevidence at all. so, by the late eighteenth century scientists knew very precisely the shape and dimensionsof the earth and its distance from the sun and planets; and now cavendish, without evenleaving home, had given them its weight. so you might think that determining the age of theearth would be relatively straightforward. after all, the necessary materials were literally attheir feet. but no. human beings would split the atom and invent television, nylon, and instantcoffee before they could figure out the age of their own planet. to understand why, we must travel north to scotland and begin with a brilliant and genialman, of whom few have ever heard, who had just invented a new science called geology.5 to a physicist, mass and weight are two quite different things. your mass stays the same wherever you go, butyour weight varies depending on how far you are from the center of some other massive object like a planet.travel to the moon and you will be much lighter but no less massive. on earth, for all practical purposes, massand weight are the same and so the terms can be treated as synonymous. at least outside the classroom. 5 the stone breakersat just the time that henry cavendish was completing his experiments in london, fourhundred miles away in edinburgh another kind of concluding moment was about to take placewith the death of james hutton. this was bad news for hutton, of course, but good news forscience as it cleared the way for a man named john playfair to rewrite hutton’s work withoutfear of embarrassment.hutton was by all accounts a man of the keenest insights and liveliest conversation, a delightin company, and without rival when it came to understanding the mysterious slow processesthat shaped the earth. unfortunately, it was beyond him to set down his notions in a form thatanyone could begin to understand. he was, as one biographer observed with an all but audiblesigh, “almost entirely innocent of rhetorical accomplishments.” nearly every line he pennedwas an invitation to slumber. here he is in his 1795 masterwork, a theory of the earth withproofs and illustrations , discussing . . . something: the world which we inhabit is composed of the materials, not of the earth which was the immediate predecessor of the present, but of the earth which, in ascending from the present, we consider as the third, and which had preceded the land that was above the surface of the sea, while our present land was yet beneath the water of the ocean. yet almost singlehandedly, and quite brilliantly, he created the science of geology andtransformed our understanding of the earth. hutton was born in 1726 into a prosperousscottish family, and enjoyed the sort of material comfort that allowed him to pass much of hislife in a genially expansive round of light work and intellectual betterment. he studiedmedicine, but found it not to his liking and turned instead to farming, which he followed in arelaxed and scientific way on the family estate in berwickshire. tiring of field and flock, in1768 he moved to edinburgh, where he founded a successful business producing salammoniac from coal soot, and busied himself with various scientific pursuits. edinburgh atthat time was a center of intellectual vigor, and hutton luxuriated in its enriching possibilities.he became a leading member of a society called the oyster club, where he passed hisevenings in the company of men such as the economist adam smith, the chemist josephblack, and the philosopher david hume, as well as such occasional visiting sparks asbenjamin franklin and james watt. in the tradition of the day, hutton took an interest in nearly everything, from mineralogy tometaphysics. he conducted experiments with chemicals, investigated methods of coal miningand canal building, toured salt mines, speculated on the mechanisms of heredity, collectedfossils, and propounded theories on rain, the composition of air, and the laws of motion,among much else. but his particular interest was geology. among the questions that attracted interest in that fanatically inquisitive age was one thathad puzzled people for a very long time namely, why ancient clamshells and other marinefossils were so often found on mountaintops. how on earth did they get there? those whothought they had a solution fell into two opposing camps. one group, known as theneptunists, was convinced that everything on earth, including seashells in improbably lofty places, could be explained by rising and falling sea levels. they believed that mountains,hills, and other features were as old as the earth itself, and were changed only when watersloshed over them during periods of global flooding. opposing them were the plutonists, who noted that volcanoes and earthquakes, amongother enlivening agents, continually changed the face of the planet but clearly owed nothing towayward seas. the plutonists also raised awkward questions about where all the water wentwhen it wasn’t in flood. if there was enough of it at times to cover the alps, then where, pray,was it during times of tranquility, such as now? their belief was that the earth was subject toprofound internal forces as well as surface ones. however, they couldn’t convincingly explainhow all those clamshells got up there. it was while puzzling over these matters that hutton had a series of exceptional insights.from looking at his own farmland, he could see that soil was created by the erosion of rocksand that particles of this soil were continually washed away and carried off by streams andrivers and redeposited elsewhere. he realized that if such a process were carried to its naturalconclusion then earth would eventually be worn quite smooth. yet everywhere around himthere were hills. clearly there had to be some additional process, some form of renewal anduplift, that created new hills and mountains to keep the cycle going. the marine fossils onmountaintops, he decided, had not been deposited during floods, but had risen along with themountains themselves. he also deduced that it was heat within the earth that created newrocks and continents and thrust up mountain chains. it is not too much to say that geologistswouldn’t grasp the full implications of this thought for two hundred years, when finally theyadopted plate tectonics. above all, what hutton’s theories suggested was that earth processesrequired huge amounts of time, far more than anyone had ever dreamed. there were enoughinsights here to transform utterly our understanding of the earth. in 1785, hutton worked his ideas up into a long paper, which was read at consecutivemeetings of the royal society of edinburgh. it attracted almost no notice at all. it’s not hardto see why. here, in part, is how he presented it to his audience: in the one case, the forming cause is in the body which is separated; for, after the body has been actuated by heat, it is by the reaction of the proper matter of the body, that the chasm which constitutes the vein is formed. in the other case, again, the cause is extrinsic in relation to the body in which the chasm is formed. there has been the most violent fracture and divulsion; but the cause is still to seek; and it appears not in the vein; for it is not every fracture and dislocation of the solid body of our earth, in which minerals, or the proper substances of mineral veins, are found. needless to say, almost no one in the audience had the faintest idea what he was talkingabout. encouraged by his friends to expand his theory, in the touching hope that he mightsomehow stumble onto clarity in a more expansive format, hutton spent the next ten yearspreparing his magnum opus, which was published in two volumes in 1795. together the two books ran to nearly a thousand pages and were, remarkably, worse thaneven his most pessimistic friends had feared. apart from anything else, nearly half the completed work now consisted of quotations from french sources, still in the original french.a third volume was so unenticing that it wasn’t published until 1899, more than a centuryafter hutton’s death, and the fourth and concluding volume was never published at all.hutton’s theory of the earth is a strong candidate for the least read important book in science(or at least would be if there weren’t so many others). even charles lyell, the greatestgeologist of the following century and a man who read everything, admitted he couldn’t getthrough it. luckily hutton had a boswell in the form of john playfair, a professor of mathematics atthe university of edinburgh and a close friend, who could not only write silken prose but thanks to many years at hutton’s elbow actually understood what hutton was trying to say,most of the time. in 1802, five years after hutton’s death, playfair produced a simplifiedexposition of the huttonian principles, entitled illustrations of the huttonian theory of theearth. the book was gratefully received by those who took an active interest in geology,which in 1802 was not a large number. that, however, was about to change. and how. in the winter of 1807, thirteen like minded souls in london got together at the freemasonstavern at long acre, in covent garden, to form a dining club to be called the geologicalsociety. the idea was to meet once a month to swap geological notions over a glass or two ofmadeira and a convivial dinner. the price of the meal was set at a deliberately hefty fifteenshillings to discourage those whose qualifications were merely cerebral. it soon becameapparent, however, that there was a demand for something more properly institutional, with apermanent headquarters, where people could gather to share and discuss new findings. inbarely a decade membership grew to four hundred still all gentlemen, of course and thegeological was threatening to eclipse the royal as the premier scientific society in thecountry. the members met twice a month from november until june, when virtually all of themwent off to spend the summer doing fieldwork. these weren’t people with a pecuniary interestin minerals, you understand, or even academics for the most part, but simply gentlemen withthe wealth and time to indulge a hobby at a more or less professional level. by 1830, therewere 745 of them, and the world would never see the like again. it is hard to imagine now, but geology excited the nineteenth century positively grippedit in a way that no science ever had before or would again. in 1839, when roderickmurchison published the silurian system, a plump and ponderous study of a type of rockcalled greywacke, it was an instant bestseller, racing through four editions, even though it costeight guineas a copy and was, in true huttonian style, unreadable. (as even a murchisonsupporter conceded, it had “a total want of literary attractiveness.”) and when, in 1841, thegreat charles lyell traveled to america to give a series of lectures in boston, selloutaudiences of three thousand at a time packed into the lowell institute to hear his tranquilizingdescriptions of marine zeolites and seismic perturbations in campania. throughout the modern, thinking world, but especially in britain, men of learning venturedinto the countryside to do a little “stone breaking,” as they called it. it was a pursuit takenseriously, and they tended to dress with appropriate gravity, in top hats and dark suits, exceptfor the reverend william buckland of oxford, whose habit it was to do his fieldwork in anacademic gown. the field attracted many extraordinary figures, not least the aforementioned murchison,who spent the first thirty or so years of his life galloping after foxes, converting aeronauticallychallenged birds into puffs of drifting feathers with buckshot, and showing no mental agilitywhatever beyond that needed to read the times or play a hand of cards. then he discoveredan interest in rocks and became with rather astounding swiftness a titan of geologicalthinking. then there was dr. james parkinson, who was also an early socialist and author of manyprovocative pamphlets with titles like “revolution without bloodshed.” in 1794, he wasimplicated in a faintly lunatic sounding conspiracy called “the pop gun plot,” in which it wasplanned to shoot king george iii in the neck with a poisoned dart as he sat in his box at thetheater. parkinson was hauled before the privy council for questioning and came within anace of being dispatched in irons to australia before the charges against him were quietlydropped. adopting a more conservative approach to life, he developed an interest in geologyand became one of the founding members of the geological society and the author of animportant geological text, organic remains of a former world, which remained in print forhalf a century. he never caused trouble again. today, however, we remember him for hislandmark study of the affliction then called the “shaking palsy,” but known ever since asparkinson’s disease. (parkinson had one other slight claim to fame. in 1785, he becamepossibly the only person in history to win a natural history museum in a raffle. the museum,in london’s leicester square, had been founded by sir ashton lever, who had driven himselfbankrupt with his unrestrained collecting of natural wonders. parkinson kept the museum until1805, when he could no longer support it and the collection was broken up and sold.) not quite as remarkable in character but more influential than all the others combined wascharles lyell. lyell was born in the year that hutton died and only seventy miles away, in thevillage of kinnordy. though scottish by birth, he grew up in the far south of england, in thenew forest of hampshire, because his mother was convinced that scots were feckless drunks.as was generally the pattern with nineteenth century gentlemen scientists, lyell came from abackground of comfortable wealth and intellectual vigor. his father, also named charles, hadthe unusual distinction of being a leading authority on the poet dante and on mosses.(orthotricium lyelli, which most visitors to the english countryside will at some time have saton, is named for him.) from his father lyell gained an interest in natural history, but it was atoxford, where he fell under the spell of the reverend william buckland he of the flowinggowns that the young lyell began his lifelong devotion to geology. buckland was a bit of a charming oddity. he had some real achievements, but he isremembered at least as much for his eccentricities. he was particularly noted for a menagerieof wild animals, some large and dangerous, that were allowed to roam through his house andgarden, and for his desire to eat his way through every animal in creation. depending onwhim and availability, guests to buckland’s house might be served baked guinea pig, mice inbatter, roasted hedgehog, or boiled southeast asian sea slug. buckland was able to find meritin them all, except the common garden mole, which he declared disgusting. almostinevitably, he became the leading authority on coprolites fossilized feces and had a tablemade entirely out of his collection of specimens. even when conducting serious science his manner was generally singular. once mrs.buckland found herself being shaken awake in the middle of the night, her husband crying inexcitement: “my dear, i believe that cheirotherium ’s footsteps are undoubtedly testudinal.”together they hurried to the kitchen in their nightclothes. mrs. buckland made a flour paste,which she spread across the table, while the reverend buckland fetched the family tortoise. plunking it onto the paste, they goaded it forward and discovered to their delight that itsfootprints did indeed match those of the fossil buckland had been studying. charles darwinthought buckland a buffoon that was the word he used but lyell appeared to find himinspiring and liked him well enough to go touring with him in scotland in 1824. it was soonafter this trip that lyell decided to abandon a career in law and devote himself to geology full time. lyell was extremely shortsighted and went through most of his life with a pained squint,which gave him a troubled air. (eventually he would lose his sight altogether.) his other slightpeculiarity was the habit, when distracted by thought, of taking up improbable positions onfurniture lying across two chairs at once or “resting his head on the seat of a chair, whilestanding up” (to quote his friend darwin). often when lost in thought he would slink so lowin a chair that his buttocks would all but touch the floor. lyell’s only real job in life was asprofessor of geology at king’s college in london from 1831 to 1833. it was around this timethat he produced the principles of geology, published in three volumes between 1830 and1833, which in many ways consolidated and elaborated upon the thoughts first voiced byhutton a generation earlier. (although lyell never read hutton in the original, he was a keenstudent of playfair’s reworked version.) between hutton’s day and lyell’s there arose a new geological controversy, which largelysuperseded, but is often confused with, the old neptunian plutonian dispute. the new battlebecame an argument between catastrophism and uniformitarianism unattractive terms for animportant and very long running dispute. catastrophists, as you might expect from the name,believed that the earth was shaped by abrupt cataclysmic events floods principally, which iswhy catastrophism and neptunism are often wrongly bundled together. catastrophism wasparticularly comforting to clerics like buckland because it allowed them to incorporate thebiblical flood of noah into serious scientific discussions. uniformitarians by contrast believedthat changes on earth were gradual and that nearly all earth processes happened slowly, overimmense spans of time. hutton was much more the father of the notion than lyell, but it waslyell most people read, and so he became in most people’s minds, then and now, the father ofmodern geological thought. lyell believed that the earth’s shifts were uniform and steady that everything that hadever happened in the past could be explained by events still going on today. lyell and hisadherents didn’t just disdain catastrophism, they detested it. catastrophists believed thatextinctions were part of a series in which animals were repeatedly wiped out and replacedwith new sets a belief that the naturalist t. h. huxley mockingly likened to “a succession ofrubbers of whist, at the end of which the players upset the table and called for a new pack.” itwas too convenient a way to explain the unknown. “never was there a dogma more calculatedto foster indolence, and to blunt the keen edge of curiosity,” sniffed lyell. lyell’s oversights were not inconsiderable. he failed to explain convincingly howmountain ranges were formed and overlooked glaciers as an agent of change. he refused toaccept louis agassiz’s idea of ice ages “the refrigeration of the globe,” as he dismissivelytermed it and was confident that mammals “would be found in the oldest fossiliferousbeds.” he rejected the notion that animals and plants suffered sudden annihilations, andbelieved that all the principal animal groups mammals, reptiles, fish, and so on hadcoexisted since the dawn of time. on all of these he would ultimately be proved wrong. yet it would be nearly impossible to overstate lyell’s influence. the principles of geologywent through twelve editions in lyell’s lifetime and contained notions that shaped geological thinking far into the twentieth century. darwin took a first edition with him on thebeaglevoyage and wrote afterward that “the great merit of the principles was that it altered thewhole tone of one’s mind, and therefore that, when seeing a thing never seen by lyell, one yetsaw it partially through his eyes.” in short, he thought him nearly a god, as did many of hisgeneration. it is a testament to the strength of lyell’s sway that in the 1980s when geologistshad to abandon just a part of it to accommodate the impact theory of extinctions, it nearlykilled them. but that is another chapter. meanwhile, geology had a great deal of sorting out to do, and not all of it went smoothly.from the outset geologists tried to categorize rocks by the periods in which they were laiddown, but there were often bitter disagreements about where to put the dividing lines nonemore so than a long running debate that became known as the great devonian controversy.the issue arose when the reverend adam sedgwick of cambridge claimed for the cambrianperiod a layer of rock that roderick murchison believed belonged rightly to the silurian. thedispute raged for years and grew extremely heated. “de la beche is a dirty dog,” murchisonwrote to a friend in a typical outburst. some sense of the strength of feeling can be gained by glancing through the chapter titlesof martin j. s. rudwick’s excellent and somber account of the issue, the great devoniancontroversy. these begin innocuously enough with headings such as “arenas of gentlemanlydebate” and “unraveling the greywacke,” but then proceed on to “the greywacke defendedand attacked,” “reproofs and recriminations,” “the spread of ugly rumors,” “weaverrecants his heresy,” “putting a provincial in his place,” and (in case there was any doubtthat this was war) “murchison opens the rhineland campaign.” the fight was finally settledin 1879 with the simple expedient of coming up with a new period, the ordovician, to beinserted between the two. because the british were the most active in the early years, british names are predominantin the geological lexicon. devonian is of course from the english county of devon. cambriancomes from the roman name for wales, while ordovician and silurian recall ancient welshtribes, the ordovices and silures. but with the rise of geological prospecting elsewhere,names began to creep in from all over.jurassic refers to the jura mountains on the border offrance and switzerland.permian recalls the former russian province of perm in the uralmountains. forcretaceous (from the latin for “chalk”) we are indebted to a belgian geologistwith the perky name of j. j. d’omalius d’halloy. originally, geological history was divided into four spans of time: primary, secondary,tertiary, and quaternary. the system was too neat to last, and soon geologists werecontributing additional divisions while eliminating others. primary and secondary fell out ofuse altogether, while quaternary was discarded by some but kept by others. today onlytertiary remains as a common designation everywhere, even though it no longer represents athird period of anything. lyell, in his principles, introduced additional units known as epochs or series to cover theperiod since the age of the dinosaurs, among them pleistocene (“most recent”), pliocene(“more recent”), miocene (“moderately recent”), and the rather endearingly vague oligocene(“but a little recent”). lyell originally intended to employ “ synchronous” for his endings,giving us such crunchy designations as meiosynchronous and pleiosynchronous. thereverend william whewell, an influential man, objected on etymological grounds andsuggested instead an “ eous” pattern, producing meioneous, pleioneous, and so on. the “ cene” terminations were thus something of a compromise. nowadays, and speaking very generally, geological time is divided first into four greatchunks known as eras: precambrian, paleozoic (from the greek meaning “old life”),mesozoic (“middle life”), and cenozoic (“recent life”). these four eras are further dividedinto anywhere from a dozen to twenty subgroups, usually called periods though sometimesknown as systems. most of these are also reasonably well known: cretaceous, jurassic,triassic, silurian, and so on.1 then come lyell’s epochs the pleistocene, miocene, and so on which apply only to themost recent (but paleontologically busy) sixty five million years, and finally we have a massof finer subdivisions known as stages or ages. most of these are named, nearly alwaysawkwardly, after places: illinoian, desmoinesian, croixian, kimmeridgian, and so on in likevein. altogether, according to john mcphee, these number in the “tens of dozens.”fortunately, unless you take up geology as a career, you are unlikely ever to hear any of themagain. further confusing the matter is that the stages or ages in north america have differentnames from the stages in europe and often only roughly intersect in time. thus the northamerican cincinnatian stage mostly corresponds with the ashgillian stage in europe, plus atiny bit of the slightly earlier caradocian stage. also, all this changes from textbook to textbook and from person to person, so that someauthorities describe seven recent epochs, while others are content with four. in some books,too, you will find the tertiary and quaternary taken out and replaced by periods of differentlengths called the palaeogene and neogene. others divide the precambrian into two eras, thevery ancient archean and the more recent proterozoic. sometimes too you will see the termphanerozoic used to describe the span encompassing the cenozoic, mesozoic, and paleozoiceras. moreover, all this applies only to units of time . rocks are divided into quite separate unitsknown as systems, series, and stages. a distinction is also made between late and early(referring to time) and upper and lower (referring to layers of rock). it can all get terriblyconfusing to nonspecialists, but to a geologist these can be matters of passion. “i have seengrown men glow incandescent with rage over this metaphorical millisecond in life’s history,”the british paleontologist richard fortey has written with regard to a long running twentieth century dispute over where the boundary lies between the cambrian and ordovician. at least today we can bring some sophisticated dating techniques to the table. for most ofthe nineteenth century geologists could draw on nothing more than the most hopefulguesswork. the frustrating position then was that although they could place the various rocksand fossils in order by age, they had no idea how long any of those ages were. whenbuckland speculated on the antiquity of an ichthyosaurus skeleton he could do no better thansuggest that it had lived somewhere between “ten thousand, or more than ten thousand timesten thousand” years earlier. although there was no reliable way of dating periods, there was no shortage of peoplewilling to try. the most well known early attempt was in 1650 when archbishop jamesussher of the church of ireland made a careful study of the bible and other historical sourcesand concluded, in a hefty tome called annals of the old testament , that the earth had been1 there will be no testing here, but if you are ever required to memorize them you might wish to remember johnwilford's helpful advice to think of the eras (precambrian, paleozoic, mesozoic, an( cenozoic) as seasons in ayear and the periods (permian, triassic jurassic, etc.) as the months. created at midday on october 23, 4004b.c. , an assertion that has amused historians andtextbook writers ever since.2 there is a persistent myth, incidentally and one propounded in many serious books thatussher’s views dominated scientific beliefs well into the nineteenth century, and that it waslyell who put everyone straight. stephen jay gould, in time’s arrow, cites as a typicalexample this sentence from a popular book of the 1980s: “until lyell published his book,most thinking people accepted the idea that the earth was young.” in fact, no. as martin j. s.rudwick puts it, “no geologist of any nationality whose work was taken seriously by othergeologists advocated a timescale confined within the limits of a literalistic exegesis ofgenesis.” even the reverend buckland, as pious a soul as the nineteenth century produced,noted that nowhere did the bible suggest that god made heaven and earth on the first day,but merely “in the beginning.” that beginning, he reasoned, may have lasted “millions uponmillions of years.” everyone agreed that the earth was ancient. the question was simply howancient. one of the better early attempts at dating the planet came from the ever reliable edmondhalley, who in 1715 suggested that if you divided the total amount of salt in the world’s seasby the amount added each year, you would get the number of years that the oceans had beenin existence, which would give you a rough idea of earth’s age. the logic was appealing, butunfortunately no one knew how much salt was in the sea or by how much it increased eachyear, which rendered the experiment impracticable. the first attempt at measurement that could be called remotely scientific was made by thefrenchman georges louis leclerc, comte de buffon, in the 1770s. it had long been knownthat the earth radiated appreciable amounts of heat that was apparent to anyone who wentdown a coal mine but there wasn’t any way of estimating the rate of dissipation. buffon’sexperiment consisted of heating spheres until they glowed white hot and then estimating therate of heat loss by touching them (presumably very lightly at first) as they cooled. from thishe guessed the earth’s age to be somewhere between 75,000 and 168,000 years old. this wasof course a wild underestimate, but a radical notion nonetheless, and buffon found himselfthreatened with excommunication for expressing it. a practical man, he apologized at oncefor his thoughtless heresy, then cheerfully repeated the assertions throughout his subsequentwritings. by the middle of the nineteenth century most learned people thought the earth was at leasta few million years old, perhaps even some tens of millions of years old, but probably notmore than that. so it came as a surprise when, in 1859 in on the origin of species , charlesdarwin announced that the geological processes that created the weald, an area of southernengland stretching across kent, surrey, and sussex, had taken, by his calculations,306,662,400 years to complete. the assertion was remarkable partly for being so arrestinglyspecific but even more for flying in the face of accepted wisdom about the age of the earth.3 itproved so contentious that darwin withdrew it from the third edition of the book. the2 although virtually all books find a space for him, there is a striking variability in the details associated withussher. some books say he made his pronouncement in 1650, others in 1654, still others in 1664. many cite thedate of earth's reputed beginning as october 26. at least one book of note spells his name \"usher.\" the matter isinterestingly surveyed in stephen jay gould's eight little piggies.3 darwin loved an exact number. in a later work, he announced that the number of worms to be found in anaverage acre of english country soil was 53,767. problem at its heart remained, however. darwin and his geological friends needed the earth tobe old, but no one could figure out a way to make it so. unfortunately for darwin, and for progress, the question came to the attention of the greatlord kelvin (who, though indubitably great, was then still just plain william thomson; hewouldn’t be elevated to the peerage until 1892, when he was sixty eight years old and nearingthe end of his career, but i shall follow the convention here of using the name retroactively).kelvin was one of the most extraordinary figures of the nineteenth century indeed of anycentury. the german scientist hermann von helmholtz, no intellectual slouch himself, wrotethat kelvin had by far the greatest “intelligence and lucidity, and mobility of thought” of anyman he had ever met. “i felt quite wooden beside him sometimes,” he added, a bit dejectedly. the sentiment is understandable, for kelvin really was a kind of victorian superman. hewas born in 1824 in belfast, the son of a professor of mathematics at the royal academicalinstitution who soon after transferred to glasgow. there kelvin proved himself such aprodigy that he was admitted to glasgow university at the exceedingly tender age of ten. bythe time he had reached his early twenties, he had studied at institutions in london and paris,graduated from cambridge (where he won the university’s top prizes for rowing andmathematics, and somehow found time to launch a musical society as well), been elected afellow of peterhouse, and written (in french and english) a dozen papers in pure and appliedmathematics of such dazzling originality that he had to publish them anonymously for fear ofembarrassing his superiors. at the age of twenty two he returned to glasgow university totake up a professorship in natural philosophy, a position he would hold for the next fifty threeyears. in the course of a long career (he lived till 1907 and the age of eighty three), he wrote 661papers, accumulated 69 patents (from which he grew abundantly wealthy), and gained renownin nearly every branch of the physical sciences. among much else, he suggested the methodthat led directly to the invention of refrigeration, devised the scale of absolute temperaturethat still bears his name, invented the boosting devices that allowed telegrams to be sentacross oceans, and made innumerable improvements to shipping and navigation, from theinvention of a popular marine compass to the creation of the first depth sounder. and thosewere merely his practical achievements. his theoretical work, in electromagnetism, thermodynamics, and the wave theory of light,was equally revolutionary.4 he had really only one flaw and that was an inability to calculatethe correct age of the earth. the question occupied much of the second half of his career, buthe never came anywhere near getting it right. his first effort, in 1862 for an article in apopular magazine called macmillan’s , suggested that the earth was 98 million years old, butcautiously allowed that the figure could be as low as 20 million years or as high as 400million. with remarkable prudence he acknowledged that his calculations could be wrong if4 in particular he elaborated the second law of thermodynamics. a discussion of these laws would be a book initself, but i offer here this crisp summation by the chemist p. w atkins, just to provide a sense of them: \"thereare four laws. the third of them, the second law, was recognized first; the first, the zeroth law, wasformulated last; the first law was second; the third law might not even be a law in the same sense as theothers.\" in briefest terms, the second la\\ states that a little energy is always wasted. you can't have a perpetualmotion device because no matter how efficient, it will always lose energy and eventually run down. the first lawsays that you can't create energy and the third that you can't reduce temperatures to absolute zero; there willalways be some residual warmth. as dennis overbye notes, the three principal laws are sometimes expressedjocularly as (1) you can't win, (2) you can't break even, and (3) you can't get out of the game. “sources now unknown to us are prepared in the great storehouse of creation” but it wasclear that he thought that unlikely. with the passage of time kelvin would become more forthright in his assertions and lesscorrect. he continually revised his estimates downward, from a maximum of 400 millionyears, to 100 million years, to 50 million years, and finally, in 1897, to a mere 24 millionyears. kelvin wasn’t being willful. it was simply that there was nothing in physics that couldexplain how a body the size of the sun could burn continuously for more than a few tens ofmillions of years at most without exhausting its fuel. therefore it followed that the sun and itsplanets were relatively, but inescapably, youthful. the problem was that nearly all the fossil evidence contradicted this, and suddenly in thenineteenth century there was a lot of fossil evidence. 6 science red in tooth and clawin 1787, someone in new jersey exactly who now seems to be forgotten found anenormous thighbone sticking out of a stream bank at a place called woodbury creek. thebone clearly didn’t belong to any species of creature still alive, certainly not in new jersey.from what little is known now, it is thought to have belonged to a hadrosaur, a large duck billed dinosaur. at the time, dinosaurs were unknown. the bone was sent to dr. caspar wistar, the nation’s leading anatomist, who described it ata meeting of the american philosophical society in philadelphia that autumn. unfortunately,wistar failed completely to recognize the bone’s significance and merely made a few cautiousand uninspired remarks to the effect that it was indeed a whopper. he thus missed the chance,half a century ahead of anyone else, to be the discoverer of dinosaurs. indeed, the boneexcited so little interest that it was put in a storeroom and eventually disappeared altogether.so the first dinosaur bone ever found was also the first to be lost. that the bone didn’t attract greater interest is more than a little puzzling, for its appearancecame at a time when america was in a froth of excitement about the remains of large, ancientanimals. the cause of this froth was a strange assertion by the great french naturalist thecomte de buffon he of the heated spheres from the previous chapter that living things inthe new world were inferior in nearly every way to those of the old world. america, buffonwrote in his vast and much esteemed histoire naturelle , was a land where the water wasstagnant, the soil unproductive, and the animals without size or vigor, their constitutionsweakened by the “noxious vapors” that rose from its rotting swamps and sunless forests. insuch an environment even the native indians lacked virility. “they have no beard or bodyhair,” buffon sagely confided, “and no ardor for the female.” their reproductive organs were“small and feeble.” buffon’s observations found surprisingly eager support among other writers, especiallythose whose conclusions were not complicated by actual familiarity with the country. adutchman named comeille de pauw announced in a popular work called recherchesphilosophiques sur les américains that native american males were not only reproductivelyunimposing, but “so lacking in virility that they had milk in their breasts.” such viewsenjoyed an improbable durability and could be found repeated or echoed in european texts tillnear the end of the nineteenth century. not surprisingly, such aspersions were indignantly met in america. thomas jeffersonincorporated a furious (and, unless the context is understood, quite bewildering) rebuttal in hisnotes on the state of virginia , and induced his new hampshire friend general john sullivanto send twenty soldiers into the northern woods to find a bull moose to present to buffon asproof of the stature and majesty of american quadrupeds. it took the men two weeks to trackdown a suitable subject. the moose, when shot, unfortunately lacked the imposing horns thatjefferson had specified, but sullivan thoughtfully included a rack of antlers from an elk orstag with the suggestion that these be attached instead. who in france, after all, would know? meanwhile in philadelphia wistar’s city naturalists had begun to assemble the bones ofa giant elephant like creature known at first as “the great american incognitum” but lateridentified, not quite correctly, as a mammoth. the first of these bones had been discovered ata place called big bone lick in kentucky, but soon others were turning up all over. america,it appeared, had once been the home of a truly substantial creature one that would surelydisprove buffon’s foolish gallic contentions. in their keenness to demonstrate the incognitum’s bulk and ferocity, the americannaturalists appear to have become slightly carried away. they overestimated its size by afactor of six and gave it frightening claws, which in fact came from a megalonyx, or giantground sloth, found nearby. rather remarkably, they persuaded themselves that the animalhad enjoyed “the agility and ferocity of the tiger,” and portrayed it in illustrations as pouncingwith feline grace onto prey from boulders. when tusks were discovered, they were forced intothe animal’s head in any number of inventive ways. one restorer screwed the tusks in upsidedown, like the fangs of a saber toothed cat, which gave it a satisfyingly aggressive aspect.another arranged the tusks so that they curved backwards on the engaging theory that thecreature had been aquatic and had used them to anchor itself to trees while dozing. the mostpertinent consideration about the incognitum, however, was that it appeared to be extinct afact that buffon cheerfully seized upon as proof of its incontestably degenerate nature. buffon died in 1788, but the controversy rolled on. in 1795 a selection of bones made theirway to paris, where they were examined by the rising star of paleontology, the youthful andaristocratic georges cuvier. cuvier was already dazzling people with his genius for takingheaps of disarticulated bones and whipping them into shapely forms. it was said that he coulddescribe the look and nature of an animal from a single tooth or scrap of jaw, and often namethe species and genus into the bargain. realizing that no one in america had thought to writea formal description of the lumbering beast, cuvier did so, and thus became its officialdiscoverer. he called it a mastodon (which means, a touch unexpectedly, “nipple teeth”). inspired by the controversy, in 1796 cuvier wrote a landmark paper, note on the species ofliving and fossil elephants, in which he put forward for the first time a formal theory ofextinctions. his belief was that from time to time the earth experienced global catastrophes inwhich groups of creatures were wiped out. for religious people, including cuvier himself, theidea raised uncomfortable implications since it suggested an unaccountable casualness on thepart of providence. to what end would god create species only to wipe them out later? thenotion was contrary to the belief in the great chain of being, which held that the world wascarefully ordered and that every living thing within it had a place and purpose, and always hadand always would. jefferson for one couldn’t abide the thought that whole species would everbe permitted to vanish (or, come to that, to evolve). so when it was put to him that theremight be scientific and political value in sending a party to explore the interior of americabeyond the mississippi he leapt at the idea, hoping the intrepid adventurers would find herdsof healthy mastodons and other outsized creatures grazing on the bounteous plains.jefferson’s personal secretary and trusted friend meriwether lewis was chosen co leader andchief naturalist for the expedition. the person selected to advise him on what to look out forwith regard to animals living and deceased was none other than caspar wistar. in the same year in fact, the same month that the aristocratic and celebrated cuvier waspropounding his extinction theories in paris, on the other side of the english channel a rathermore obscure englishman was having an insight into the value of fossils that would also havelasting ramifications. william smith was a young supervisor of construction on the somersetcoal canal. on the evening of january 5, 1796, he was sitting in a coaching inn in somersetwhen he jotted down the notion that would eventually make his reputation. to interpret rocks,there needs to be some means of correlation, a basis on which you can tell that thosecarboniferous rocks from devon are younger than these cambrian rocks from wales. smith’sinsight was to realize that the answer lay with fossils. at every change in rock strata certainspecies of fossils disappeared while others carried on into subsequent levels. by noting which species appeared in which strata, you could work out the relative ages of rocks wherever theyappeared. drawing on his knowledge as a surveyor, smith began at once to make a map ofbritain’s rock strata, which would be published after many trials in 1815 and would become acornerstone of modern geology. (the story is comprehensively covered in simonwinchester’s popular book the map that changed the world .) unfortunately, having had his insight, smith was curiously uninterested in understandingwhy rocks were laid down in the way they were. “i have left off puzzling about the origin ofstrata and content myself with knowing that it is so,” he recorded. “the whys and whereforescannot come within the province of a mineral surveyor.” smith’s revelation regarding strata heightened the moral awkwardness concerningextinctions. to begin with, it confirmed that god had wiped out creatures not occasionally butrepeatedly. this made him seem not so much careless as peculiarly hostile. it also made itinconveniently necessary to explain how some species were wiped out while others continuedunimpeded into succeeding eons. clearly there was more to extinctions than could beaccounted for by a single noachian deluge, as the biblical flood was known. cuvier resolvedthe matter to his own satisfaction by suggesting that genesis applied only to the most recentinundation. god, it appeared, hadn’t wished to distract or alarm moses with news of earlier,irrelevant extinctions. so by the early years of the nineteenth century, fossils had taken on a certain inescapableimportance, which makes wistar’s failure to see the significance of his dinosaur bone all themore unfortunate. suddenly, in any case, bones were turning up all over. several otheropportunities arose for americans to claim the discovery of dinosaurs but all were wasted. in1806 the lewis and clark expedition passed through the hell creek formation in montana, anarea where fossil hunters would later literally trip over dinosaur bones, and even examinedwhat was clearly a dinosaur bone embedded in rock, but failed to make anything of it. otherbones and fossilized footprints were found in the connecticut river valley of new englandafter a farm boy named plinus moody spied ancient tracks on a rock ledge at south hadley,massachusetts. some of these at least survive notably the bones of an anchisaurus, whichare in the collection of the peabody museum at yale. found in 1818, they were the firstdinosaur bones to be examined and saved, but unfortunately weren’t recognized for what theywere until 1855. in that same year, 1818, caspar wistar died, but he did gain a certainunexpected immortality when a botanist named thomas nuttall named a delightful climbingshrub after him. some botanical purists still insist on spelling it wistaria . by this time, however, paleontological momentum had moved to england. in 1812, atlyme regis on the dorset coast, an extraordinary child named mary anning aged eleven,twelve, or thirteen, depending on whose account you read found a strange fossilized seamonster, seventeen feet long and now known as the ichthyosaurus, embedded in the steep anddangerous cliffs along the english channel. it was the start of a remarkable career. anning would spend the next thirty five yearsgathering fossils, which she sold to visitors. (she is commonly held to be the source for thefamous tongue twister “she sells seashells on the seashore.”) she would also find the firstplesiosaurus, another marine monster, and one of the first and best pterodactyls. though noneof these was technically a dinosaur, that wasn’t terribly relevant at the time since nobody then knew what a dinosaur was. it was enough to realize that the world had once held creaturesstrikingly unlike anything we might now find. it wasn’t simply that anning was good at spotting fossils though she was unrivalled atthat but that she could extract them with the greatest delicacy and without damage. if youever have the chance to visit the hall of ancient marine reptiles at the natural history museumin london, i urge you to take it for there is no other way to appreciate the scale and beauty ofwhat this young woman achieved working virtually unaided with the most basic tools innearly impossible conditions. the plesiosaur alone took her ten years of patient excavation.although untrained, anning was also able to provide competent drawings and descriptions forscholars. but even with the advantage of her skills, significant finds were rare and she passedmost of her life in poverty. it would be hard to think of a more overlooked person in the history of paleontology thanmary anning, but in fact there was one who came painfully close. his name was gideonalgernon mantell and he was a country doctor in sussex. mantell was a lanky assemblage of shortcomings he was vain, self absorbed, priggish,neglectful of his family but never was there a more devoted amateur paleontologist. he wasalso lucky to have a devoted and observant wife. in 1822, while he was making a house callon a patient in rural sussex, mrs. mantell went for a stroll down a nearby lane and in a pile ofrubble that had been left to fill potholes she found a curious object a curved brown stone,about the size of a small walnut. knowing her husband’s interest in fossils, and thinking itmight be one, she took it to him. mantell could see at once it was a fossilized tooth, and aftera little study became certain that it was from an animal that was herbivorous, reptilian,extremely large tens of feet long and from the cretaceous period. he was right on allcounts, but these were bold conclusions since nothing like it had been seen before or evenimagined. aware that his finding would entirely upend what was understood about the past, and urgedby his friend the reverend william buckland he of the gowns and experimental appetite to proceed with caution, mantell devoted three painstaking years to seeking evidence tosupport his conclusions. he sent the tooth to cuvier in paris for an opinion, but the greatfrenchman dismissed it as being from a hippopotamus. (cuvier later apologized handsomelyfor this uncharacteristic error.) one day while doing research at the hunterian museum inlondon, mantell fell into conversation with a fellow researcher who told him the tooth lookedvery like those of animals he had been studying, south american iguanas. a hastycomparison confirmed the resemblance. and so mantell’s creature became iguanodon , aftera basking tropical lizard to which it was not in any manner related. mantell prepared a paper for delivery to the royal society. unfortunately it emerged thatanother dinosaur had been found at a quarry in oxfordshire and had just been formallydescribed by the reverend buckland, the very man who had urged him not to work in haste.it was the megalosaurus, and the name was actually suggested to buckland by his friend dr.james parkinson, the would be radical and eponym for parkinson’s disease. buckland, it maybe recalled, was foremost a geologist, and he showed it with his work on megalosaurus. in hisreport, for the transactions of the geological society of london , he noted that the creature’steeth were not attached directly to the jawbone as in lizards but placed in sockets in themanner of crocodiles. but having noticed this much, buckland failed to realize what it meant:megalosaurus was an entirely new type of creature. so although his report demonstrated littleacuity or insight, it was still the first published description of a dinosaur, and so to him rather than the far more deserving mantell goes the credit for the discovery of this ancient line ofbeings. unaware that disappointment was going to be a continuing feature of his life, mantellcontinued hunting for fossils he found another giant, the hylaeosaurus, in 1833 andpurchasing others from quarrymen and farmers until he had probably the largest fossilcollection in britain. mantell was an excellent doctor and equally gifted bone hunter, but hewas unable to support both his talents. as his collecting mania grew, he neglected his medicalpractice. soon fossils filled nearly the whole of his house in brighton and consumed much ofhis income. much of the rest went to underwriting the publication of books that few cared toown. illustrations of the geology of sussex , published in 1827, sold only fifty copies and lefthim £300 out of pocket an uncomfortably substantial sum for the times. in some desperation mantell hit on the idea of turning his house into a museum andcharging admission, then belatedly realized that such a mercenary act would ruin his standingas a gentleman, not to mention as a scientist, and so he allowed people to visit the house forfree. they came in their hundreds, week after week, disrupting both his practice and his homelife. eventually he was forced to sell most of his collection to pay off his debts. soon after, hiswife left him, taking their four children with her. remarkably, his troubles were only just beginning. in the district of sydenham in south london, at a place called crystal palace park, therestands a strange and forgotten sight: the world’s first life sized models of dinosaurs. not manypeople travel there these days, but once this was one of the most popular attractions inlondon in effect, as richard fortey has noted, the world’s first theme park. quite a lotabout the models is not strictly correct. the iguanodon’s thumb has been placed on its nose,as a kind of spike, and it stands on four sturdy legs, making it look like a rather stout andawkwardly overgrown dog. (in life, the iguanodon did not crouch on all fours, but wasbipedal.) looking at them now you would scarcely guess that these odd and lumbering beastscould cause great rancor and bitterness, but they did. perhaps nothing in natural history hasbeen at the center of fiercer and more enduring hatreds than the line of ancient beasts knownas dinosaurs. at the time of the dinosaurs’ construction, sydenham was on the edge of london and itsspacious park was considered an ideal place to re erect the famous crystal palace, the glassand cast iron structure that had been the centerpiece of the great exhibition of 1851, and fromwhich the new park naturally took its name. the dinosaurs, built of concrete, were a kind ofbonus attraction. on new year’s eve 1853 a famous dinner for twenty one prominentscientists was held inside the unfinished iguanodon. gideon mantell, the man who had foundand identified the iguanodon, was not among them. the person at the head of the table wasthe greatest star of the young science of paleontology. his name was richard owen and bythis time he had already devoted several productive years to making gideon mantell’s lifehell. owen had grown up in lancaster, in the north of england, where he had trained as a doctor.he was a born anatomist and so devoted to his studies that he sometimes illicitly borrowedlimbs, organs, and other parts from cadavers and took them home for leisurely dissection.once while carrying a sack containing the head of a black african sailor that he had just removed, owen slipped on a wet cobble and watched in horror as the head bounced awayfrom him down the lane and through the open doorway of a cottage, where it came to rest inthe front parlor. what the occupants had to say upon finding an unattached head rolling to ahalt at their feet can only be imagined. one assumes that they had not formed any terriblyadvanced conclusions when, an instant later, a fraught looking young man rushed in,wordlessly retrieved the head, and rushed out again. in 1825, aged just twenty one, owen moved to london and soon after was engaged by theroyal college of surgeons to help organize their extensive, but disordered, collections ofmedical and anatomical specimens. most of these had been left to the institution by johnhunter, a distinguished surgeon and tireless collector of medical curiosities, but had neverbeen catalogued or organized, largely because the paperwork explaining the significance ofeach had gone missing soon after hunter’s death. owen swiftly distinguished himself with his powers of organization and deduction. at thesame time he showed himself to be a peerless anatomist with instincts for reconstructionalmost on a par with the great cuvier in paris. he become such an expert on the anatomy ofanimals that he was granted first refusal on any animal that died at the london zoologicalgardens, and these he would invariably have delivered to his house for examination. once hiswife returned home to find a freshly deceased rhinoceros filling the front hallway. he quicklybecame a leading expert on all kinds of animals living and extinct from platypuses,echidnas, and other newly discovered marsupials to the hapless dodo and the extinct giantbirds called moas that had roamed new zealand until eaten out of existence by the maoris. hewas the first to describe the archaeopteryx after its discovery in bavaria in 1861 and the firstto write a formal epitaph for the dodo. altogether he produced some six hundred anatomicalpapers, a prodigious output. but it was for his work with dinosaurs that owen is remembered. he coined the termdinosauria in 1841. it means “terrible lizard” and was a curiously inapt name. dinosaurs, aswe now know, weren’t all terrible some were no bigger than rabbits and probably extremelyretiring and the one thing they most emphatically were not was lizards, which are actually ofa much older (by thirty million years) lineage. owen was well aware that the creatures werereptilian and had at his disposal a perfectly good greek word, herpeton, but for some reasonchose not to use it. another, more excusable error (given the paucity of specimens at the time)was that dinosaurs constitute not one but two orders of reptiles: the bird hipped ornithischiansand the lizard hipped saurischians. owen was not an attractive person, in appearance or in temperament. a photograph fromhis late middle years shows him as gaunt and sinister, like the villain in a victorianmelodrama, with long, lank hair and bulging eyes a face to frighten babies. in manner hewas cold and imperious, and he was without scruple in the furtherance of his ambitions. hewas the only person charles darwin was ever known to hate. even owen’s son (who soonafter killed himself) referred to his father’s “lamentable coldness of heart.” his undoubted gifts as an anatomist allowed him to get away with the most barefaceddishonesties. in 1857, the naturalist t. h. huxley was leafing through a new edition ofchurchill’s medical directory when he noticed that owen was listed as professor ofcomparative anatomy and physiology at the government school of mines, which rathersurprised huxley as that was the position he held. upon inquiring how churchill’s had madesuch an elemental error, he was told that the information had been provided to them by dr.owen himself. a fellow naturalist named hugh falconer, meanwhile, caught owen taking credit for one of his discoveries. others accused him of borrowing specimens, then denyinghe had done so. owen even fell into a bitter dispute with the queen’s dentist over the creditfor a theory concerning the physiology of teeth. he did not hesitate to persecute those whom he disliked. early in his career owen used hisinfluence at the zoological society to blackball a young man named robert grant whose onlycrime was to have shown promise as a fellow anatomist. grant was astonished to discover thathe was suddenly denied access to the anatomical specimens he needed to conduct hisresearch. unable to pursue his work, he sank into an understandably dispirited obscurity. but no one suffered more from owen’s unkindly attentions than the hapless andincreasingly tragic gideon mantell. after losing his wife, his children, his medical practice,and most of his fossil collection, mantell moved to london. there in 1841 the fateful yearin which owen would achieve his greatest glory for naming and identifying the dinosaurs mantell was involved in a terrible accident. while crossing clapham common in a carriage,he somehow fell from his seat, grew entangled in the reins, and was dragged at a gallop overrough ground by the panicked horses. the accident left him bent, crippled, and in chronicpain, with a spine damaged beyond repair. capitalizing on mantell’s enfeebled state, owen set about systematically expungingmantell’s contributions from the record, renaming species that mantell had named yearsbefore and claiming credit for their discovery for himself. mantell continued to try to dooriginal research but owen used his influence at the royal society to ensure that most of hispapers were rejected. in 1852, unable to bear any more pain or persecution, mantell took hisown life. his deformed spine was removed and sent to the royal college of surgeonswhere and now here’s an irony for you it was placed in the care of richard owen, directorof the college’s hunterian museum. but the insults had not quite finished. soon after mantell’s death an arrestingly uncharitableobituary appeared in the literary gazette. in it mantell was characterized as a mediocreanatomist whose modest contributions to paleontology were limited by a “want of exactknowledge.” the obituary even removed the discovery of the iguanodon from him andcredited it instead to cuvier and owen, among others. though the piece carried no byline, thestyle was owen’s and no one in the world of the natural sciences doubted the authorship. by this stage, however, owen’s transgressions were beginning to catch up with him. hisundoing began when a committee of the royal society a committee of which he happenedto be chairman decided to award him its highest honor, the royal medal, for a paper he hadwritten on an extinct mollusc called the belemnite. “however,” as deborah cadbury notes inher excellent history of the period, terrible lizard, “this piece of work was not quite asoriginal as it appeared.” the belemnite, it turned out, had been discovered four years earlierby an amateur naturalist named chaning pearce, and the discovery had been fully reported ata meeting of the geological society. owen had been at that meeting, but failed to mentionthis when he presented a report of his own to the royal society in which, not incidentally,he rechristened the creature belemnites owenii in his own honor. although owen was allowedto keep the royal medal, the episode left a permanent tarnish on his reputation, even amonghis few remaining supporters. eventually huxley managed to do to owen what owen had done to so many others: he hadhim voted off the councils of the zoological and royal societies. as a final insult huxleybecame the new hunterian professor at the royal college of surgeons. owen would never again do important research, but the latter half of his career was devotedto one unexceptionable pursuit for which we can all be grateful. in 1856 he became head ofthe natural history section of the british museum, in which capacity he became the drivingforce behind the creation of london’s natural history museum. the grand and belovedgothic heap in south kensington, opened in 1880, is almost entirely a testament to his vision. before owen, museums were designed primarily for the use and edification of the elite, andeven then it was difficult to gain access. in the early days of the british museum, prospectivevisitors had to make a written application and undergo a brief interview to determine if theywere fit to be admitted at all. they then had to return a second time to pick up a ticket that isassuming they had passed the interview and finally come back a third time to view themuseum’s treasures. even then they were whisked through in groups and not allowed tolinger. owen’s plan was to welcome everyone, even to the point of encouraging workingmento visit in the evening, and to devote most of the museum’s space to public displays. he evenproposed, very radically, to put informative labels on each display so that people couldappreciate what they were viewing. in this, somewhat unexpectedly, he was opposed by t. h.huxley, who believed that museums should be primarily research institutes. by making thenatural history museum an institution for everyone, owen transformed our expectations ofwhat museums are for. still, his altruism in general toward his fellow man did not deflect him from more personalrivalries. one of his last official acts was to lobby against a proposal to erect a statue inmemory of charles darwin. in this he failed though he did achieve a certain belated,inadvertent triumph. today his statue commands a masterly view from the staircase of themain hall in the natural history museum, while darwin and t. h. huxley are consignedsomewhat obscurely to the museum coffee shop, where they stare gravely over peoplesnacking on cups of tea and jam doughnuts. it would be reasonable to suppose that richard owen’s petty rivalries marked the low pointof nineteenth century paleontology, but in fact worse was to come, this time from overseas. inamerica in the closing decades of the century there arose a rivalry even more spectacularlyvenomous, if not quite as destructive. it was between two strange and ruthless men, edwarddrinker cope and othniel charles marsh. they had much in common. both were spoiled, driven, self centered, quarrelsome, jealous,mistrustful, and ever unhappy. between them they changed the world of paleontology. they began as mutual friends and admirers, even naming fossil species after each other,and spent a pleasant week together in 1868. however, something then went wrong betweenthem nobody is quite sure what and by the following year they had developed an enmitythat would grow into consuming hatred over the next thirty years. it is probably safe to saythat no two people in the natural sciences have ever despised each other more. marsh, the elder of the two by eight years, was a retiring and bookish fellow, with a trimbeard and dapper manner, who spent little time in the field and was seldom very good atfinding things when he was there. on a visit to the famous dinosaur fields of como bluff,wyoming, he failed to notice the bones that were, in the words of one historian, “lyingeverywhere like logs.” but he had the means to buy almost anything he wanted. although hecame from a modest background his father was a farmer in upstate new york his uncle was the supremely rich and extraordinarily indulgent financier george peabody. when marshshowed an interest in natural history, peabody had a museum built for him at yale andprovided funds sufficient for marsh to fill it with almost whatever took his fancy. cope was born more directly into privilege his father was a rich philadelphiabusinessman and was by far the more adventurous of the two. in the summer of 1876 inmontana while george armstrong custer and his troops were being cut down at little bighorn, cope was out hunting for bones nearby. when it was pointed out to him that this wasprobably not the most prudent time to be taking treasures from indian lands, cope thought fora minute and decided to press on anyway. he was having too good a season. at one point heran into a party of suspicious crow indians, but he managed to win them over by repeatedlytaking out and replacing his false teeth. for a decade or so, marsh and cope’s mutual dislike primarily took the form of quietsniping, but in 1877 it erupted into grandiose dimensions. in that year a coloradoschoolteacher named arthur lakes found bones near morrison while out hiking with a friend.recognizing the bones as coming from a “gigantic saurian,” lakes thoughtfully dispatchedsome samples to both marsh and cope. a delighted cope sent lakes a hundred dollars for histrouble and asked him not to tell anyone of his discovery, especially marsh. confused, lakesnow asked marsh to pass the bones on to cope. marsh did so, but it was an affront that hewould never forget. it also marked the start of a war between the two that became increasingly bitter,underhand, and often ridiculous. they sometimes stooped to one team’s diggers throwingrocks at the other team’s. cope was caught at one point jimmying open crates that belonged tomarsh. they insulted each other in print and each poured scorn on the other’s results.seldom perhaps never has science been driven forward more swiftly and successfully byanimosity. over the next several years the two men between them increased the number ofknown dinosaur species in america from 9 to almost 150. nearly every dinosaur that theaverage person can name stegosaurus, brontosaurus, diplodocus, triceratops was found byone or the other of them.1 unfortunately, they worked in such reckless haste that they oftenfailed to note that a new discovery was something already known. between them theymanaged to “discover” a species calleduintatheres anceps no fewer than twenty two times. ittook years to sort out some of the classification messes they made. some are not sorted outyet. of the two, cope’s scientific legacy was much the more substantial. in a breathtakinglyindustrious career, he wrote some 1,400 learned papers and described almost 1,300 newspecies of fossil (of all types, not just dinosaurs) more than double marsh’s output in bothcases. cope might have done even more, but unfortunately he went into a rather precipitatedescent in his later years. having inherited a fortune in 1875, he invested unwisely in silverand lost everything. he ended up living in a single room in a philadelphia boarding house,surrounded by books, papers, and bones. marsh by contrast finished his days in a splendidmansion in new haven. cope died in 1897, marsh two years later. in his final years, cope developed one other interesting obsession. it became his earnestwish to be declared the type specimen forhomo sapiens  that is, that his bones would be theofficial set for the human race. normally, the type specimen of a species is the first set of1 the notable exception being the tyrannosaurus rex, which was found by barnum brown in 1902. bones found, but since no first set of homo sapiens bones exists, there was a vacancy, whichcope desired to fill. it was an odd and vain wish, but no one could think of any grounds tooppose it. to that end, cope willed his bones to the wistar institute, a learned society inphiladelphia endowed by the descendants of the seemingly inescapable caspar wistar.unfortunately, after his bones were prepared and assembled, it was found that they showedsigns of incipient syphilis, hardly a feature one would wish to preserve in the type specimenfor one’s own race. so cope’s petition and his bones were quietly shelved. there is still notype specimen for modern humans. as for the other players in this drama, owen died in 1892, a few years before cope ormarsh. buckland ended up by losing his mind and finished his days a gibbering wreck in alunatic asylum in clapham, not far from where mantell had suffered his crippling accident.mantell’s twisted spine remained on display at the hunterian museum for nearly a centurybefore being mercifully obliterated by a german bomb in the blitz. what remained ofmantell’s collection after his death passed on to his children, and much of it was taken to newzealand by his son walter, who emigrated there in 1840. walter became a distinguished kiwi,eventually attaining the office of minister of native affairs. in 1865 he donated the primespecimens from his father’s collection, including the famous iguanodon tooth, to the colonialmuseum (now the museum of new zealand) in wellington, where they have remained eversince. the iguanodon tooth that started it all arguably the most important tooth inpaleontology is no longer on display. of course dinosaur hunting didn’t end with the deaths of the great nineteenth century fossilhunters. indeed, to a surprising extent it had only just begun. in 1898, the year that fellbetween the deaths of cope and marsh, a trove greater by far than anything found before wasdiscovered noticed, really at a place called bone cabin quarry, only a few miles frommarsh’s prime hunting ground at como bluff, wyoming. there, hundreds and hundreds offossil bones were to be found weathering out of the hills. they were so numerous, in fact, thatsomeone had built a cabin out of them hence the name. in just the first two seasons, 100,000pounds of ancient bones were excavated from the site, and tens of thousands of pounds morecame in each of the half dozen years that followed. the upshot is that by the turn of the twentieth century, paleontologists had literally tons ofold bones to pick over. the problem was that they still didn’t have any idea how old any ofthese bones were. worse, the agreed ages for the earth couldn’t comfortably support thenumbers of eons and ages and epochs that the past obviously contained. if earth were reallyonly twenty million years old or so, as the great lord kelvin insisted, then whole orders ofancient creatures must have come into being and gone out again practically in the samegeological instant. it just made no sense. other scientists besides kelvin turned their minds to the problem and came up with resultsthat only deepened the uncertainty. samuel haughton, a respected geologist at trinity collegein dublin, announced an estimated age for the earth of 2,300 million years way beyondanything anybody else was suggesting. when this was drawn to his attention, he recalculatedusing the same data and put the figure at 153 million years. john joly, also of trinity, decidedto give edmond halley’s ocean salts idea a whirl, but his method was based on so manyfaulty assumptions that he was hopelessly adrift. he calculated that the earth was 89 millionyears old an age that fit neatly enough with kelvin’s assumptions but unfortunately not withreality. such was the confusion that by the close of the nineteenth century, depending on whichtext you consulted, you could learn that the number of years that stood between us and thedawn of complex life in the cambrian period was 3 million, 18 million, 600 million, 794million, or 2.4 billion or some other number within that range. as late as 1910, one of themost respected estimates, by the american george becker, put the earth’s age at perhaps aslittle as 55 million years. just when matters seemed most intractably confused, along came another extraordinaryfigure with a novel approach. he was a bluff and brilliant new zealand farm boy namedernest rutherford, and he produced pretty well irrefutable evidence that the earth was at leastmany hundreds of millions of years old, probably rather more. remarkably, his evidence was based on alchemy natural, spontaneous, scientificallycredible, and wholly non occult, but alchemy nonetheless. newton, it turned out, had not beenso wrong after all. and exactly how that came to be is of course another story. 7 elemental matterschemistry as an earnest and respectable science is often said to date from 1661, whenrobert boyle of oxford published the sceptical chymist  the first work to distinguishbetween chemists and alchemists but it was a slow and often erratic transition. into theeighteenth century scholars could feel oddly comfortable in both camps like the germanjohann becher, who produced an unexceptionable work on mineralogy called physicasubterranea , but who also was certain that, given the right materials, he could make himselfinvisible. perhaps nothing better typifies the strange and often accidental nature of chemical sciencein its early days than a discovery made by a german named hennig brand in 1675. brandbecame convinced that gold could somehow be distilled from human urine. (the similarity ofcolor seems to have been a factor in his conclusion.) he assembled fifty buckets of humanurine, which he kept for months in his cellar. by various recondite processes, he converted theurine first into a noxious paste and then into a translucent waxy substance. none of it yieldedgold, of course, but a strange and interesting thing did happen. after a time, the substancebegan to glow. moreover, when exposed to air, it often spontaneously burst into flame. the commercial potential for the stuff which soon became known as phosphorus, fromgreek and latin roots meaning “light bearing” was not lost on eager businesspeople, but thedifficulties of manufacture made it too costly to exploit. an ounce of phosphorus retailed forsix guineas perhaps five hundred dollars in today’s money or more than gold. at first, soldiers were called on to provide the raw material, but such an arrangement washardly conducive to industrial scale production. in the 1750s a swedish chemist named karl(or carl) scheele devised a way to manufacture phosphorus in bulk without the slop or smellof urine. it was largely because of this mastery of phosphorus that sweden became, andremains, a leading producer of matches. scheele was both an extraordinary and extraordinarily luckless fellow. a poor pharmacistwith little in the way of advanced apparatus, he discovered eight elements chlorine, fluorine,manganese, barium, molybdenum, tungsten, nitrogen, and oxygen and got credit for none ofthem. in every case, his finds were either overlooked or made it into publication aftersomeone else had made the same discovery independently. he also discovered many usefulcompounds, among them ammonia, glycerin, and tannic acid, and was the first to see thecommercial potential of chlorine as a bleach all breakthroughs that made other peopleextremely wealthy. scheele’s one notable shortcoming was a curious insistence on tasting a little of everythinghe worked with, including such notoriously disagreeable substances as mercury, prussic acid(another of his discoveries), and hydrocyanic acid a compound so famously poisonous that150 years later erwin schrödinger chose it as his toxin of choice in a famous thoughtexperiment (see page 146). scheele’s rashness eventually caught up with him. in 1786, agedjust forty three, he was found dead at his workbench surrounded by an array of toxicchemicals, any one of which could have accounted for the stunned and terminal look on hisface. were the world just and swedish speaking, scheele would have enjoyed universal acclaim.instead credit has tended to lodge with more celebrated chemists, mostly from the english speaking world. scheele discovered oxygen in 1772, but for various heartbreakingly complicated reasons could not get his paper published in a timely manner. instead credit wentto joseph priestley, who discovered the same element independently, but latterly, in thesummer of 1774. even more remarkable was scheele’s failure to receive credit for thediscovery of chlorine. nearly all textbooks still attribute chlorine’s discovery to humphrydavy, who did indeed find it, but thirty six years after scheele had. although chemistry had come a long way in the century that separated newton and boylefrom scheele and priestley and henry cavendish, it still had a long way to go. right up to theclosing years of the eighteenth century (and in priestley’s case a little beyond) scientistseverywhere searched for, and sometimes believed they had actually found, things that justweren’t there: vitiated airs, dephlogisticated marine acids, phloxes, calxes, terraqueousexhalations, and, above all, phlogiston, the substance that was thought to be the active agentin combustion. somewhere in all this, it was thought, there also resided a mysterious élanvital, the force that brought inanimate objects to life. no one knew where this ethereal essencelay, but two things seemed probable: that you could enliven it with a jolt of electricity (anotion mary shelley exploited to full effect in her novel frankenstein ) and that it existed insome substances but not others, which is why we ended up with two branches of chemistry:organic (for those substances that were thought to have it) and inorganic (for those that didnot). someone of insight was needed to thrust chemistry into the modern age, and it was thefrench who provided him. his name was antoine laurent lavoisier. born in 1743, lavoisierwas a member of the minor nobility (his father had purchased a title for the family). in 1768,he bought a practicing share in a deeply despised institution called the ferme générale (orgeneral farm), which collected taxes and fees on behalf of the government. althoughlavoisier himself was by all accounts mild and fair minded, the company he worked for wasneither. for one thing, it did not tax the rich but only the poor, and then often arbitrarily. forlavoisier, the appeal of the institution was that it provided him with the wealth to follow hisprincipal devotion, science. at his peak, his personal earnings reached 150,000 livres a year perhaps $20 million in today’s money. three years after embarking on this lucrative career path, he married the fourteen year olddaughter of one of his bosses. the marriage was a meeting of hearts and minds both. madamelavoisier had an incisive intellect and soon was working productively alongside her husband.despite the demands of his job and busy social life, they managed to put in five hours ofscience on most days two in the early morning and three in the evening as well as thewhole of sunday, which they called their jour de bonheur (day of happiness). somehowlavoisier also found the time to be commissioner of gunpowder, supervise the building of awall around paris to deter smugglers, help found the metric system, and coauthor thehandbook méthode de nomenclature chimique , which became the bible for agreeing on thenames of the elements. as a leading member of the académie royale des sciences, he was also required to take aninformed and active interest in whatever was topical hypnotism, prison reform, therespiration of insects, the water supply of paris. it was in such a capacity in 1780 thatlavoisier made some dismissive remarks about a new theory of combustion that had beensubmitted to the academy by a hopeful young scientist. the theory was indeed wrong, but thescientist never forgave him. his name was jean paul marat. the one thing lavoisier never did was discover an element. at a time when it seemed as ifalmost anybody with a beaker, a flame, and some interesting powders could discover something new and when, not incidentally, some two thirds of the elements were yet to befound lavoisier failed to uncover a single one. it certainly wasn’t for want of beakers.lavoisier had thirteen thousand of them in what was, to an almost preposterous degree, thefinest private laboratory in existence. instead he took the discoveries of others and made sense of them. he threw out phlogistonand mephitic airs. he identified oxygen and hydrogen for what they were and gave them boththeir modern names. in short, he helped to bring rigor, clarity, and method to chemistry. and his fancy equipment did in fact come in very handy. for years, he and madamelavoisier occupied themselves with extremely exacting studies requiring the finestmeasurements. they determined, for instance, that a rusting object doesn’t lose weight, aseveryone had long assumed, but gains weight an extraordinary discovery. somehow as itrusted the object was attracting elemental particles from the air. it was the first realization thatmatter can be transformed but not eliminated. if you burned this book now, its matter wouldbe changed to ash and smoke, but the net amount of stuff in the universe would be the same.this became known as the conservation of mass, and it was a revolutionary concept.unfortunately, it coincided with another type of revolution the french one and for this onelavoisier was entirely on the wrong side. not only was he a member of the hated ferme générale, but he had enthusiastically builtthe wall that enclosed paris an edifice so loathed that it was the first thing attacked by therebellious citizens. capitalizing on this, in 1791 marat, now a leading voice in the nationalassembly, denounced lavoisier and suggested that it was well past time for his hanging.soon afterward the ferme générale was shut down. not long after this marat was murderedin his bath by an aggrieved young woman named charlotte corday, but by this time it was toolate for lavoisier. in 1793, the reign of terror, already intense, ratcheted up to a higher gear. in octobermarie antoinette was sent to the guillotine. the following month, as lavoisier and his wifewere making tardy plans to slip away to scotland, lavoisier was arrested. in may he andthirty one fellow farmers general were brought before the revolutionary tribunal (in acourtroom presided over by a bust of marat). eight were granted acquittals, but lavoisier andthe others were taken directly to the place de la revolution (now the place de la concorde),site of the busiest of french guillotines. lavoisier watched his father in law beheaded, thenstepped up and accepted his fate. less than three months later, on july 27, robespierrehimself was dispatched in the same way and in the same place, and the reign of terrorswiftly ended. a hundred years after his death, a statue of lavoisier was erected in paris and muchadmired until someone pointed out that it looked nothing like him. under questioning thesculptor admitted that he had used the head of the mathematician and philosopher the marquisde condorcet apparently he had a spare in the hope that no one would notice or, havingnoticed, would care. in the second regard he was correct. the statue of lavoisier cum condorcet was allowed to remain in place for another half century until the second worldwar when, one morning, it was taken away and melted down for scrap. in the early 1800s there arose in england a fashion for inhaling nitrous oxide, or laughinggas, after it was discovered that its use “was attended by a highly pleasurable thrilling.” for the next half century it would be the drug of choice for young people. one learned body, theaskesian society, was for a time devoted to little else. theaters put on “laughing gasevenings” where volunteers could refresh themselves with a robust inhalation and thenentertain the audience with their comical staggerings. it wasn’t until 1846 that anyone got around to finding a practical use for nitrous oxide, asan anesthetic. goodness knows how many tens of thousands of people suffered unnecessaryagonies under the surgeon’s knife because no one thought of the gas’s most obvious practicalapplication. i mention this to make the point that chemistry, having come so far in the eighteenthcentury, rather lost its bearings in the first decades of the nineteenth, in much the way thatgeology would in the early years of the twentieth. partly it was to do with the limitations ofequipment there were, for instance, no centrifuges until the second half of the century,severely restricting many kinds of experiments and partly it was social. chemistry was,generally speaking, a science for businesspeople, for those who worked with coal and potashand dyes, and not gentlemen, who tended to be drawn to geology, natural history, and physics.(this was slightly less true in continental europe than in britain, but only slightly.) it isperhaps telling that one of the most important observations of the century, brownian motion,which established the active nature of molecules, was made not by a chemist but by a scottishbotanist, robert brown. (what brown noticed, in 1827, was that tiny grains of pollensuspended in water remained indefinitely in motion no matter how long he gave them tosettle. the cause of this perpetual motion namely the actions of invisible molecules waslong a mystery.) things might have been worse had it not been for a splendidly improbable character namedcount von rumford, who, despite the grandeur of his title, began life in woburn,massachusetts, in 1753 as plain benjamin thompson. thompson was dashing and ambitious,“handsome in feature and figure,” occasionally courageous and exceedingly bright, butuntroubled by anything so inconveniencing as a scruple. at nineteen he married a rich widowfourteen years his senior, but at the outbreak of revolution in the colonies he unwisely sidedwith the loyalists, for a time spying on their behalf. in the fateful year of 1776, facing arrest“for lukewarmness in the cause of liberty,” he abandoned his wife and child and fled justahead of a mob of anti royalists armed with buckets of hot tar, bags of feathers, and anearnest desire to adorn him with both. he decamped first to england and then to germany, where he served as a military advisorto the government of bavaria, so impressing the authorities that in 1791 he was named countvon rumford of the holy roman empire. while in munich, he also designed and laid out thefamous park known as the english garden. in between these undertakings, he somehow found time to conduct a good deal of solidscience. he became the world’s foremost authority on thermodynamics and the first toelucidate the principles of the convection of fluids and the circulation of ocean currents. healso invented several useful objects, including a drip coffeemaker, thermal underwear, and atype of range still known as the rumford fireplace. in 1805, during a sojourn in france, hewooed and married madame lavoisier, widow of antoine laurent. the marriage was not asuccess and they soon parted. rumford stayed on in france, where he died, universallyesteemed by all but his former wives, in 1814. but our purpose in mentioning him here is that in 1799, during a comparatively briefinterlude in london, he founded the royal institution, yet another of the many learnedsocieties that popped into being all over britain in the late eighteenth and early nineteenthcenturies. for a time it was almost the only institution of standing to actively promote theyoung science of chemistry, and that was thanks almost entirely to a brilliant young mannamed humphry davy, who was appointed the institution’s professor of chemistry shortlyafter its inception and rapidly gained fame as an outstanding lecturer and productiveexperimentalist. soon after taking up his position, davy began to bang out new elements one afteranother potassium, sodium, magnesium, calcium, strontium, and aluminum or aluminium,depending on which branch of english you favor.1 he discovered so many elements not somuch because he was serially astute as because he developed an ingenious technique ofapplying electricity to a molten substance electrolysis, as it is known. altogether hediscovered a dozen elements, a fifth of the known total of his day. davy might have done farmore, but unfortunately as a young man he developed an abiding attachment to the buoyantpleasures of nitrous oxide. he grew so attached to the gas that he drew on it (literally) three orfour times a day. eventually, in 1829, it is thought to have killed him. fortunately more sober types were at work elsewhere. in 1808, a dour quaker named johndalton became the first person to intimate the nature of an atom (progress that will bediscussed more completely a little further on), and in 1811 an italian with the splendidlyoperatic name of lorenzo romano amadeo carlo avogadro, count of quarequa and cerreto,made a discovery that would prove highly significant in the long term namely, that twoequal volumes of gases of any type, if kept at the same pressure and temperature, will containidentical numbers of molecules. two things were notable about avogadro’s principle, as it became known. first, itprovided a basis for more accurately measuring the size and weight of atoms. usingavogadro’s mathematics, chemists were eventually able to work out, for instance, that atypical atom had a diameter of 0.00000008 centimeters, which is very little indeed. andsecond, almost no one knew about avogadro’s appealingly simple principle for almost fiftyyears.2 partly this was because avogadro himself was a retiring fellow he worked alone,corresponded very little with fellow scientists, published few papers, and attended nomeetings but also it was because there were no meetings to attend and few chemicaljournals in which to publish. this is a fairly extraordinary fact. the industrial revolution was1 the confusion over the aluminum/aluminium spelling arose b cause of some uncharacteristic indecisiveness ondavy's part. when he first isolated the element in 1808, he called it alumium. for son reason he thought better ofthat and changed it to aluminum four years later. americans dutifully adopted the new term, but mai britishusers disliked aluminum, pointing out that it disrupted the  ium pattern established by sodium, calcium, andstrontium, so they added a vowel and syllable.2 the principle led to the much later adoption of avogadro's number, a basic unit of measure in chemistry, whichwas named for avogadro long after his death. it is the number of molecules found in 2.016 grams of hydrogengas (or an equal volume of any other gas). its value is placed at 6.0221367 x 1023, which is an enormously largenumber. chemistry students have long amused themselves by computing just how large a number it is, so i canreport that it is equivalent to the number of popcorn kernels needed to cover the united states to a depth of ninemiles, or cupfuls of water in the pacific ocean, or soft drink cans that would, evenly stacked, cover the earth to adepth of 200 miles. an equivalent number of american pennies would be enough to make every person on eartha dollar trillionaire. it is a big number. driven in large part by developments in chemistry, and yet as an organized science chemistrybarely existed for decades. the chemical society of london was not founded until 1841 and didn’t begin to produce aregular journal until 1848, by which time most learned societies in britain geological,geographical, zoological, horticultural, and linnaean (for naturalists and botanists) were atleast twenty years old and often much more. the rival institute of chemistry didn’t come intobeing until 1877, a year after the founding of the american chemical society. becausechemistry was so slow to get organized, news of avogadro’s important breakthrough of 1811didn’t begin to become general until the first international chemistry congress, in karlsruhe,in 1860. because chemists for so long worked in isolation, conventions were slow to emerge. untilwell into the second half of the century, the formula h2o2might mean water to one chemistbut hydrogen peroxide to another. c2h4could signify ethylene or marsh gas. there was hardlya molecule that was uniformly represented everywhere. chemists also used a bewildering variety of symbols and abbreviations, often self invented.sweden’s j. j. berzelius brought a much needed measure of order to matters by decreeing thatthe elements be abbreviated on the basis of their greek or latin names, which is why theabbreviation for iron is fe (from the latin ferrum ) and that for silver is ag (from the latinargentum ). that so many of the other abbreviations accord with their english names (n fornitrogen, o for oxygen, h for hydrogen, and so on) reflects english’s latinate nature, not itsexalted status. to indicate the number of atoms in a molecule, berzelius employed asuperscript notation, as in h2o. later, for no special reason, the fashion became to render thenumber as subscript: h2o. despite the occasional tidyings up, chemistry by the second half of the nineteenth centurywas in something of a mess, which is why everybody was so pleased by the rise toprominence in 1869 of an odd and crazed looking professor at the university of st. petersburgnamed dmitri ivanovich mendeleyev. mendeleyev (also sometimes spelled mendeleev or mendeléef) was born in 1834 attobolsk, in the far west of siberia, into a well educated, reasonably prosperous, and verylarge family so large, in fact, that history has lost track of exactly how many mendeleyevsthere were: some sources say there were fourteen children, some say seventeen. all agree, atany rate, that dmitri was the youngest. luck was not always with the mendeleyevs. whendmitri was small his father, the headmaster of a local school, went blind and his mother hadto go out to work. clearly an extraordinary woman, she eventually became the manager of asuccessful glass factory. all went well until 1848, when the factory burned down and thefamily was reduced to penury. determined to get her youngest child an education, theindomitable mrs. mendeleyev hitchhiked with young dmitri four thousand miles to st.petersburg that’s equivalent to traveling from london to equatorial guinea and depositedhim at the institute of pedagogy. worn out by her efforts, she died soon after. mendeleyev dutifully completed his studies and eventually landed a position at the localuniversity. there he was a competent but not terribly outstanding chemist, known more forhis wild hair and beard, which he had trimmed just once a year, than for his gifts in thelaboratory. however, in 1869, at the age of thirty five, he began to toy with a way to arrange theelements. at the time, elements were normally grouped in two ways either by atomic weight(using avogadro’s principle) or by common properties (whether they were metals or gases,for instance). mendeleyev’s breakthrough was to see that the two could be combined in asingle table. as is often the way in science, the principle had actually been anticipated three yearspreviously by an amateur chemist in england named john newlands. he suggested that whenelements were arranged by weight they appeared to repeat certain properties in a sense toharmonize at every eighth place along the scale. slightly unwisely, for this was an ideawhose time had not quite yet come, newlands called it the law of octaves and likened thearrangement to the octaves on a piano keyboard. perhaps there was something in newlands’smanner of presentation, but the idea was considered fundamentally preposterous and widelymocked. at gatherings, droller members of the audience would sometimes ask him if he couldget his elements to play them a little tune. discouraged, newlands gave up pushing the ideaand soon dropped from view altogether. mendeleyev used a slightly different approach, placing his elements into groups of seven,but employed fundamentally the same principle. suddenly the idea seemed brilliant andwondrously perceptive. because the properties repeated themselves periodically, the inventionbecame known as the periodic table. mendeleyev was said to have been inspired by the card game known as solitaire in northamerica and patience elsewhere, wherein cards are arranged by suit horizontally and bynumber vertically. using a broadly similar concept, he arranged the elements in horizontalrows called periods and vertical columns called groups. this instantly showed one set ofrelationships when read up and down and another when read from side to side. specifically,the vertical columns put together chemicals that have similar properties. thus copper sits ontop of silver and silver sits on top of gold because of their chemical affinities as metals, whilehelium, neon, and argon are in a column made up of gases. (the actual, formal determinant inthe ordering is something called their electron valences, for which you will have to enroll innight classes if you wish an understanding.) the horizontal rows, meanwhile, arrange thechemicals in ascending order by the number of protons in their nuclei what is known as theiratomic number. the structure of atoms and the significance of protons will come in a following chapter, sofor the moment all that is necessary is to appreciate the organizing principle: hydrogen hasjust one proton, and so it has an atomic number of one and comes first on the chart; uraniumhas ninety two protons, and so it comes near the end and has an atomic number of ninety two.in this sense, as philip ball has pointed out, chemistry really is just a matter of counting.(atomic number, incidentally, is not to be confused with atomic weight, which is the numberof protons plus the number of neutrons in a given element.) there was still a great deal thatwasn’t known or understood. hydrogen is the most common element in the universe, and yetno one would guess as much for another thirty years. helium, the second most abundantelement, had only been found the year before its existence hadn’t even been suspectedbefore that and then not on earth but in the sun, where it was found with a spectroscopeduring a solar eclipse, which is why it honors the greek sun god helios. it wouldn’t beisolated until 1895. even so, thanks to mendeleyev’s invention, chemistry was now on a firmfooting. for most of us, the periodic table is a thing of beauty in the abstract, but for chemists itestablished an immediate orderliness and clarity that can hardly be overstated. “without adoubt, the periodic table of the chemical elements is the most elegant organizational chartever devised,” wrote robert e. krebs in the history and use of our earth’s chemicalelements, and you can find similar sentiments in virtually every history of chemistry in print. today we have “120 or so” known elements ninety two naturally occurring ones plus acouple of dozen that have been created in labs. the actual number is slightly contentiousbecause the heavy, synthesized elements exist for only millionths of seconds and chemistssometimes argue over whether they have really been detected or not. in mendeleyev’s dayjust sixty three elements were known, but part of his cleverness was to realize that theelements as then known didn’t make a complete picture, that many pieces were missing. histable predicted, with pleasing accuracy, where new elements would slot in when they werefound. no one knows, incidentally, how high the number of elements might go, though anythingbeyond 168 as an atomic weight is considered “purely speculative,” but what is certain is thatanything that is found will fit neatly into mendeleyev’s great scheme. the nineteenth century held one last great surprise for chemists. it began in 1896 whenhenri becquerel in paris carelessly left a packet of uranium salts on a wrapped photographicplate in a drawer. when he took the plate out some time later, he was surprised to discoverthat the salts had burned an impression in it, just as if the plate had been exposed to light. thesalts were emitting rays of some sort. considering the importance of what he had found, becquerel did a very strange thing: heturned the matter over to a graduate student for investigation. fortunately the student was arecent émigré from poland named marie curie. working with her new husband, pierre, curiefound that certain kinds of rocks poured out constant and extraordinary amounts of energy,yet without diminishing in size or changing in any detectable way. what she and her husbandcouldn’t know what no one could know until einstein explained things the followingdecade was that the rocks were converting mass into energy in an exceedingly efficient way.marie curie dubbed the effect “radioactivity.” in the process of their work, the curies alsofound two new elements polonium, which they named after her native country, and radium.in 1903 the curies and becquerel were jointly awarded the nobel prize in physics. (mariecurie would win a second prize, in chemistry, in 1911, the only person to win in bothchemistry and physics.) at mcgill university in montreal the young new zealand born ernest rutherford becameinterested in the new radioactive materials. with a colleague named frederick soddy hediscovered that immense reserves of energy were bound up in these small amounts of matter,and that the radioactive decay of these reserves could account for most of the earth’s warmth.they also discovered that radioactive elements decayed into other elements that one dayyou had an atom of uranium, say, and the next you had an atom of lead. this was trulyextraordinary. it was alchemy, pure and simple; no one had ever imagined that such a thingcould happen naturally and spontaneously. ever the pragmatist, rutherford was the first to see that there could be a valuable practicalapplication in this. he noticed that in any sample of radioactive material, it always took the same amount of time for half the sample to decay the celebrated half life and that thissteady, reliable rate of decay could be used as a kind of clock. by calculating backwards fromhow much radiation a material had now and how swiftly it was decaying, you could work outits age. he tested a piece of pitchblende, the principal ore of uranium, and found it to be 700million years old very much older than the age most people were prepared to grant theearth. in the spring of 1904, rutherford traveled to london to give a lecture at the royalinstitution the august organization founded by count von rumford only 105 years before,though that powdery and periwigged age now seemed a distant eon compared with the roll your sleeves up robustness of the late victorians. rutherford was there to talk about his newdisintegration theory of radioactivity, as part of which he brought out his piece of pitchblende.tactfully for the aging kelvin was present, if not always fully awake rutherford notedthat kelvin himself had suggested that the discovery of some other source of heat wouldthrow his calculations out. rutherford had found that other source. thanks to radioactivity theearth could be and self evidently was much older than the twenty four million yearskelvin’s calculations allowed. kelvin beamed at rutherford’s respectful presentation, but was in fact unmoved. he neveraccepted the revised figures and to his dying day believed his work on the age of the earth hismost astute and important contribution to science far greater than his work onthermodynamics. as with most scientific revolutions, rutherford’s new findings were not universallyaccepted. john joly of dublin strenuously insisted well into the 1930s that the earth was nomore than eighty nine million years old, and was stopped only then by his own death. othersbegan to worry that rutherford had now given them too much time. but even withradiometric dating, as decay measurements became known, it would be decades before we gotwithin a billion years or so of earth’s actual age. science was on the right track, but still wayout. kelvin died in 1907. that year also saw the death of dmitri mendeleyev. like kelvin, hisproductive work was far behind him, but his declining years were notably less serene. as heaged, mendeleyev became increasingly eccentric he refused to acknowledge the existenceof radiation or the electron or anything else much that was new and difficult. his finaldecades were spent mostly storming out of labs and lecture halls all across europe. in 1955,element 101 was named mendelevium in his honor. “appropriately,” notes paul strathern, “itis an unstable element.” radiation, of course, went on and on, literally and in ways nobody expected. in the early1900s pierre curie began to experience clear signs of radiation sickness notably dull achesin his bones and chronic feelings of malaise which doubtless would have progressedunpleasantly. we shall never know for certain because in 1906 he was fatally run over by acarriage while crossing a paris street. marie curie spent the rest of her life working with distinction in the field, helping to foundthe celebrated radium institute of the university of paris in 1914. despite her two nobelprizes, she was never elected to the academy of sciences, in large part because after the deathof pierre she conducted an affair with a married physicist that was sufficiently indiscreet toscandalize even the french or at least the old men who ran the academy, which is perhapsanother matter. for a long time it was assumed that anything so miraculously energetic as radioactivitymust be beneficial. for years, manufacturers of toothpaste and laxatives put radioactivethorium in their products, and at least until the late 1920s the glen springs hotel in the fingerlakes region of new york (and doubtless others as well) featured with pride the therapeuticeffects of its “radioactive mineral springs.” radioactivity wasn’t banned in consumerproducts until 1938. by this time it was much too late for madame curie, who died ofleukemia in 1934. radiation, in fact, is so pernicious and long lasting that even now herpapers from the 1890s even her cookbooks are too dangerous to handle. her lab books arekept in lead lined boxes, and those who wish to see them must don protective clothing. thanks to the devoted and unwittingly high risk work of the first atomic scientists, by theearly years of the twentieth century it was becoming clear that earth was unquestionablyvenerable, though another half century of science would have to be done before anyone couldconfidently say quite how venerable. science, meanwhile, was about to get a new age of itsown the atomic one. part iii a new age dawnsa physicist is the atoms’ way of thinking about atoms.  anonymous 8 einstein’s universeas the nineteenth century drew to a close, scientists could reflect with satisfaction thatthey had pinned down most of the mysteries of the physical world: electricity, magnetism,gases, optics, acoustics, kinetics, and statistical mechanics, to name just a few, all had falleninto order before them. they had discovered the x ray, the cathode ray, the electron, andradioactivity, invented the ohm, the watt, the kelvin, the joule, the amp, and the little erg. if a thing could be oscillated, accelerated, perturbed, distilled, combined, weighed, or madegaseous they had done it, and in the process produced a body of universal laws so weightyand majestic that we still tend to write them out in capitals: the electromagnetic field theoryof light, richter’s law of reciprocal proportions, charles’s law of gases, the law ofcombining volumes, the zeroth law, the valence concept, the laws of mass actions, andothers beyond counting. the whole world clanged and chuffed with the machinery andinstruments that their ingenuity had produced. many wise people believed that there wasnothing much left for science to do. in 1875, when a young german in kiel named max planck was deciding whether to devotehis life to mathematics or to physics, he was urged most heartily not to choose physicsbecause the breakthroughs had all been made there. the coming century, he was assured,would be one of consolidation and refinement, not revolution. planck didn’t listen. he studiedtheoretical physics and threw himself body and soul into work on entropy, a process at theheart of thermodynamics, which seemed to hold much promise for an ambitious young man.1in 1891 he produced his results and learned to his dismay that the important work on entropyhad in fact been done already, in this instance by a retiring scholar at yale university namedj. willard gibbs. gibbs is perhaps the most brilliant person that most people have never heard of. modest tothe point of near invisibility, he passed virtually the whole of his life, apart from three yearsspent studying in europe, within a three block area bounded by his house and the yalecampus in new haven, connecticut. for his first ten years at yale he didn’t even bother todraw a salary. (he had independent means.) from 1871, when he joined the university as aprofessor, to his death in 1903, his courses attracted an average of slightly over one student asemester. his written work was difficult to follow and employed a private form of notationthat many found incomprehensible. but buried among his arcane formulations were insightsof the loftiest brilliance. in 1875 78, gibbs produced a series of papers, collectively titledon the equilibrium ofheterogeneous substances , that dazzlingly elucidated the thermodynamic principles of, well,1 specifically it is a measure of randomness or disorder in a system. darrell ebbing, in the textbook generalchemistry, very usefully suggests thinking of a deck of cards. a new pack fresh out of the box, arranged by suitand in sequence from ace to king, can be said to be in its ordered state. shuffle the cards and you put them in adisordered state. entropy is a way of measuring just how disordered that state is and of determining thelikelihood of particular outcomes with further shuffles. of course, if you wish to have any observationspublished in a respectable journal you will need also to understand additional concepts such as thermalnonuniformities, lattice distances, and stoichiometric relationships, but that's the general idea. nearly everything “gases, mixtures, surfaces, solids, phase changes . . . chemical reactions,electrochemical cells, sedimentation, and osmosis,” to quote william h. cropper. in essencewhat gibbs did was show that thermodynamics didn’t apply simply to heat and energy at thesort of large and noisy scale of the steam engine, but was also present and influential at theatomic level of chemical reactions. gibbs’s equilibrium has been called “the principia ofthermodynamics,” but for reasons that defy speculation gibbs chose to publish theselandmark observations in the transactions of the connecticut academy of arts and sciences,a journal that managed to be obscure even in connecticut, which is why planck did not hearof him until too late. undaunted well, perhaps mildly daunted planck turned to other matters.2 we shall turnto these ourselves in a moment, but first we must make a slight (but relevant!) detour tocleveland, ohio, and an institution then known as the case school of applied science. there,in the 1880s, a physicist of early middle years named albert michelson, assisted by his friendthe chemist edward morley, embarked on a series of experiments that produced curious anddisturbing results that would have great ramifications for much of what followed. what michelson and morley did, without actually intending to, was undermine alongstanding belief in something called the luminiferous ether, a stable, invisible, weightless,frictionless, and unfortunately wholly imaginary medium that was thought to permeate theuniverse. conceived by descartes, embraced by newton, and venerated by nearly everyoneever since, the ether held a position of absolute centrality in nineteenth century physics as away of explaining how light traveled across the emptiness of space. it was especially neededin the 1800s because light and electromagnetism were now seen as waves, which is to saytypes of vibrations. vibrations must occur in something; hence the need for, and lastingdevotion to, an ether. as late as 1909, the great british physicist j. j. thomson was insisting:“the ether is not a fantastic creation of the speculative philosopher; it is as essential to us asthe air we breathe” this more than four years after it was pretty incontestably establishedthat it didn’t exist. people, in short, were really attached to the ether. if you needed to illustrate the idea of nineteenth century america as a land of opportunity,you could hardly improve on the life of albert michelson. born in 1852 on the german polish border to a family of poor jewish merchants, he came to the united states with hisfamily as an infant and grew up in a mining camp in california’s gold rush country, where hisfather ran a dry goods business. too poor to pay for college, he traveled to washington, d.c.,and took to loitering by the front door of the white house so that he could fall in besidepresident ulysses s. grant when the president emerged for his daily constitutional. (it wasclearly a more innocent age.) in the course of these walks, michelson so ingratiated himself tothe president that grant agreed to secure for him a free place at the u.s. naval academy. itwas there that michelson learned his physics. ten years later, by now a professor at the case school in cleveland, michelson becameinterested in trying to measure something called the ether drift a kind of head windproduced by moving objects as they plowed through space. one of the predictions ofnewtonian physics was that the speed of light as it pushed through the ether should vary with2 planck was often unlucky in life. his beloved first wife died early, in 1909, and the younger of his two sonswas killed in the first world war. he also had twin daughters whom he adored. one died giving birth. thesurviving twin went to look after the baby and fell in love with her sister's husband. they married and two yearslater she died in childbirth. in 1944, when planck was eighty five, an allied bomb fell on his house and he losteverything papers, diaries, a lifetime of accumulations. the following year his surviving son was caught in aconspiracy to assassinate hitler and executed. respect to an observer depending on whether the observer was moving toward the source oflight or away from it, but no one had figured out a way to measure this. it occurred tomichelson that for half the year the earth is traveling toward the sun and for half the year it ismoving away from it, and he reasoned that if you took careful enough measurements atopposite seasons and compared light’s travel time between the two, you would have youranswer. michelson talked alexander graham bell, newly enriched inventor of the telephone, intoproviding the funds to build an ingenious and sensitive instrument of michelson’s owndevising called an interferometer, which could measure the velocity of light with greatprecision. then, assisted by the genial but shadowy morley, michelson embarked on years offastidious measurements. the work was delicate and exhausting, and had to be suspended fora time to permit michelson a brief but comprehensive nervous breakdown, but by 1887 theyhad their results. they were not at all what the two scientists had expected to find. as caltech astrophysicist kip s. thorne has written: “the speed of light turned out to bethe same inall directions and at all seasons.” it was the first hint in two hundred years inexactly two hundred years, in fact that newton’s laws might not apply all the timeeverywhere. the michelson morley outcome became, in the words of william h. cropper,“probably the most famous negative result in the history of physics.” michelson was awardeda nobel prize in physics for the work the first american so honored but not for twentyyears. meanwhile, the michelson morley experiments would hover unpleasantly, like a mustysmell, in the background of scientific thought. remarkably, and despite his findings, when the twentieth century dawned michelsoncounted himself among those who believed that the work of science was nearly at an end,with “only a few turrets and pinnacles to be added, a few roof bosses to be carved,” in thewords of a writer in nature. in fact, of course, the world was about to enter a century of science where many peoplewouldn’t understand anything and none would understand everything. scientists would soonfind themselves adrift in a bewildering realm of particles and antiparticles, where things popin and out of existence in spans of time that make nanoseconds look plodding and uneventful,where everything is strange. science was moving from a world of macrophysics, whereobjects could be seen and held and measured, to one of microphysics, where events transpirewith unimaginable swiftness on scales far below the limits of imagining. we were about toenter the quantum age, and the first person to push on the door was the so far unfortunatemax planck. in 1900, now a theoretical physicist at the university of berlin and at the somewhatadvanced age of forty two, planck unveiled a new “quantum theory,” which posited thatenergy is not a continuous thing like flowing water but comes in individualized packets,which he called quanta. this was a novel concept, and a good one. in the short term it wouldhelp to provide a solution to the puzzle of the michelson morley experiments in that itdemonstrated that light needn’t be a wave after all. in the longer term it would lay thefoundation for the whole of modern physics. it was, at all events, the first clue that the worldwas about to change. but the landmark event the dawn of a new age came in 1905, when there appeared inthe german physics journal annalen der physik a series of papers by a young swissbureaucrat who had no university affiliation, no access to a laboratory, and the regular use of no library greater than that of the national patent office in bern, where he was employed as atechnical examiner third class. (an application to be promoted to technical examiner secondclass had recently been rejected.) his name was albert einstein, and in that one eventful year he submitted to annalen derphysik five papers, of which three, according to c. p. snow, “were among the greatest in thehistory of physics” one examining the photoelectric effect by means of planck’s newquantum theory, one on the behavior of small particles in suspension (what is known asbrownian motion), and one outlining a special theory of relativity. the first won its author a nobel prize and explained the nature of light (and also helped tomake television possible, among other things).3 the second provided proof that atoms doindeed exist a fact that had, surprisingly, been in some dispute. the third merely changedthe world. einstein was born in ulm, in southern germany, in 1879, but grew up in munich. little inhis early life suggested the greatness to come. famously he didn’t learn to speak until he wasthree. in the 1890s, his father’s electrical business failing, the family moved to milan, butalbert, by now a teenager, went to switzerland to continue his education though he failedhis college entrance exams on the first try. in 1896 he gave up his german citizenship toavoid military conscription and entered the zurich polytechnic institute on a four year coursedesigned to churn out high school science teachers. he was a bright but not outstandingstudent. in 1900 he graduated and within a few months was beginning to contribute papers toannalen der physik. his very first paper, on the physics of fluids in drinking straws (of allthings), appeared in the same issue as planck’s quantum theory. from 1902 to 1904 heproduced a series of papers on statistical mechanics only to discover that the quietlyproductive j. willard gibbs in connecticut had done that work as well, in his elementaryprinciples of statistical mechanics of 1901. at the same time he had fallen in love with a fellow student, a hungarian named milevamaric. in 1901 they had a child out of wedlock, a daughter, who was discreetly put up foradoption. einstein never saw his child. two years later, he and maric were married. inbetween these events, in 1902, einstein took a job with the swiss patent office, where hestayed for the next seven years. he enjoyed the work: it was challenging enough to engage hismind, but not so challenging as to distract him from his physics. this was the backgroundagainst which he produced the special theory of relativity in 1905. called “on the electrodynamics of moving bodies,” it is one of the most extraordinaryscientific papers ever published, as much for how it was presented as for what it said. it hadno footnotes or citations, contained almost no mathematics, made no mention of any workthat had influenced or preceded it, and acknowledged the help of just one individual, a3 einstein was honored, somewhat vaguely, \"for services to theoretical physics.\" he had to wait sixteen years, till1921, to receive the award quite a long time, all things considered, but nothing at all compared with frederickreines, who detected the neutrino in 1957 but wasn't honored with a nobel until 1995, thirty eight years later, orthe german ernst ruska, who invented the electron microscope in 1932 and received his nobel prize in 1986,more than half a century after the fact. since nobel prizes are never awarded posthumously, longevity can be asimportant a factor as ingenuity for prizewinners. colleague at the patent office named michele besso. it was, wrote c. p. snow, as if einstein“had reached the conclusions by pure thought, unaided, without listening to the opinions ofothers. to a surprisingly large extent, that is precisely what he had done.” his famous equation, e =mc2, did not appear with the paper, but came in a brief supplementthat followed a few months later. as you will recall from school days, e in the equation standsfor energy, m for mass, and c2 for the speed of light squared. in simplest terms, what the equation says is that mass and energy have an equivalence.they are two forms of the same thing: energy is liberated matter; matter is energy waiting tohappen. since c2 (the speed of light times itself) is a truly enormous number, what theequation is saying is that there is a huge amount a really huge amount of energy bound upin every material thing.4 you may not feel outstandingly robust, but if you are an average sized adult you willcontain within your modest frame no less than 7 x 1018joules of potential energy enough toexplode with the force of thirty very large hydrogen bombs, assuming you knew how toliberate it and really wished to make a point. everything has this kind of energy trappedwithin it. we’re just not very good at getting it out. even a uranium bomb the mostenergetic thing we have produced yet releases less than 1 percent of the energy it couldrelease if only we were more cunning. among much else, einstein’s theory explained how radiation worked: how a lump ofuranium could throw out constant streams of high level energy without melting away like anice cube. (it could do it by converting mass to energy extremely efficiently à lae =mc2.) itexplained how stars could burn for billions of years without racing through their fuel. (ditto.)at a stroke, in a simple formula, einstein endowed geologists and astronomers with theluxury of billions of years. above all, the special theory showed that the speed of light wasconstant and supreme. nothing could overtake it. it brought light (no pun intended, exactly) tothe very heart of our understanding of the nature of the universe. not incidentally, it alsosolved the problem of the luminiferous ether by making it clear that it didn’t exist. einsteingave us a universe that didn’t need it. physicists as a rule are not overattentive to the pronouncements of swiss patent officeclerks, and so, despite the abundance of useful tidings, einstein’s papers attracted little notice.having just solved several of the deepest mysteries of the universe, einstein applied for a jobas a university lecturer and was rejected, and then as a high school teacher and was rejectedthere as well. so he went back to his job as an examiner third class, but of course he keptthinking. he hadn’t even come close to finishing yet. when the poet paul valéry once asked einstein if he kept a notebook to record his ideas,einstein looked at him with mild but genuine surprise. “oh, that’s not necessary,” he replied.“it’s so seldom i have one.” i need hardly point out that when he did get one it tended to begood. einstein’s next idea was one of the greatest that anyone has ever had indeed, the verygreatest, according to boorse, motz, and weaver in their thoughtful history of atomic science.4 how c came to be the symbol for the speed of light is something of a mystery, but david bodanis suggests itprobably came from the latin celeritas, meaning swiftness. the relevant volume of the oxford englishdictionary, compiled a decade before einstein's theory, recognizes c as a symbol for many things, from carbonto cricket, but makes no mention of it as a symbol for light or swiftness. “as the creation of a single mind,” they write, “it is undoubtedly the highest intellectualachievement of humanity,” which is of course as good as a compliment can get. in 1907, or so it has sometimes been written, albert einstein saw a workman fall off a roofand began to think about gravity. alas, like many good stories this one appears to beapocryphal. according to einstein himself, he was simply sitting in a chair when the problemof gravity occurred to him. actually, what occurred to einstein was something more like the beginning of a solution tothe problem of gravity, since it had been evident to him from the outset that one thing missingfrom the special theory was gravity. what was “special” about the special theory was that itdealt with things moving in an essentially unimpeded state. but what happened when a thingin motion light, above all encountered an obstacle such as gravity? it was a question thatwould occupy his thoughts for most of the next decade and lead to the publication in early1917 of a paper entitled “cosmological considerations on the general theory of relativity.”the special theory of relativity of 1905 was a profound and important piece of work, ofcourse, but as c. p. snow once observed, if einstein hadn’t thought of it when he did someoneelse would have, probably within five years; it was an idea waiting to happen. but the generaltheory was something else altogether. “without it,” wrote snow in 1979, “it is likely that weshould still be waiting for the theory today.” with his pipe, genially self effacing manner, and electrified hair, einstein was too splendida figure to remain permanently obscure, and in 1919, the war over, the world suddenlydiscovered him. almost at once his theories of relativity developed a reputation for beingimpossible for an ordinary person to grasp. matters were not helped, as david bodanis pointsout in his superb book e=mc2 , when the new york times decided to do a story, and forreasons that can never fail to excite wonder sent the paper’s golfing correspondent, onehenry crouch, to conduct the interview. crouch was hopelessly out of his depth, and got nearly everything wrong. among the morelasting errors in his report was the assertion that einstein had found a publisher daring enoughto publish a book that only twelve men “in all the world could comprehend.” there was nosuch book, no such publisher, no such circle of learned men, but the notion stuck anyway.soon the number of people who could grasp relativity had been reduced even further in thepopular imagination and the scientific establishment, it must be said, did little to disturb themyth. when a journalist asked the british astronomer sir arthur eddington if it was true that hewas one of only three people in the world who could understand einstein’s relativity theories,eddington considered deeply for a moment and replied: “i am trying to think who the thirdperson is.” in fact, the problem with relativity wasn’t that it involved a lot of differentialequations, lorentz transformations, and other complicated mathematics (though it did eveneinstein needed help with some of it), but that it was just so thoroughly nonintuitive. in essence what relativity says is that space and time are not absolute, but relative to boththe observer and to the thing being observed, and the faster one moves the more pronouncedthese effects become. we can never accelerate ourselves to the speed of light, and the harderwe try (and faster we go) the more distorted we will become, relative to an outside observer. almost at once popularizers of science tried to come up with ways to make these conceptsaccessible to a general audience. one of the more successful attempts commercially at least was the abc of relativity by the mathematician and philosopher bertrand russell. init, russell employed an image that has been used many times since. he asked the reader toenvision a train one hundred yards long moving at 60 percent of the speed of light. tosomeone standing on a platform watching it pass, the train would appear to be only eightyyards long and everything on it would be similarly compressed. if we could hear thepassengers on the train speak, their voices would sound slurred and sluggish, like a recordplayed at too slow a speed, and their movements would appear similarly ponderous. even theclocks on the train would seem to be running at only four fifths of their normal speed. however and here’s the thing people on the train would have no sense of thesedistortions. to them, everything on the train would seem quite normal. it would be we on theplatform who looked weirdly compressed and slowed down. it is all to do, you see, with yourposition relative to the moving object. this effect actually happens every time you move. fly across the united states, and youwill step from the plane a quinzillionth of a second, or something, younger than those you leftbehind. even in walking across the room you will very slightly alter your own experience oftime and space. it has been calculated that a baseball thrown at a hundred miles an hour willpick up 0.000000000002 grams of mass on its way to home plate. so the effects of relativityare real and have been measured. the problem is that such changes are much too small tomake the tiniest detectable difference to us. but for other things in the universe light,gravity, the universe itself these are matters of consequence. so if the ideas of relativity seem weird, it is only because we don’t experience these sorts ofinteractions in normal life. however, to turn to bodanis again, we all commonly encounterother kinds of relativity for instance with regard to sound. if you are in a park and someoneis playing annoying music, you know that if you move to a more distant spot the music willseem quieter. that’s not because the musicis quieter, of course, but simply that your positionrelative to it has changed. to something too small or sluggish to duplicate this experience asnail, say the idea that a boom box could seem to two observers to produce two differentvolumes of music simultaneously might seem incredible. the most challenging and nonintuitive of all the concepts in the general theory of relativityis the idea that time is part of space. our instinct is to regard time as eternal, absolute,immutable nothing can disturb its steady tick. in fact, according to einstein, time is variableand ever changing. it even has shape. it is bound up “inextricably interconnected,” instephen hawking’s expression with the three dimensions of space in a curious dimensionknown as spacetime. spacetime is usually explained by asking you to imagine something flat but pliant amattress, say, or a sheet of stretched rubber on which is resting a heavy round object, suchas an iron ball. the weight of the iron ball causes the material on which it is sitting to stretchand sag slightly. this is roughly analogous to the effect that a massive object such as the sun(the iron ball) has on spacetime (the material): it stretches and curves and warps it. now ifyou roll a smaller ball across the sheet, it tries to go in a straight line as required by newton’slaws of motion, but as it nears the massive object and the slope of the sagging fabric, it rollsdownward, ineluctably drawn to the more massive object. this is gravity a product of thebending of spacetime. every object that has mass creates a little depression in the fabric of the cosmos. thus theuniverse, as dennis overbye has put it, is “the ultimate sagging mattress.” gravity on this view is no longer so much a thing as an outcome “not a ‘force’ but a byproduct of thewarping of spacetime,” in the words of the physicist michio kaku, who goes on: “in somesense, gravity does not exist; what moves the planets and stars is the distortion of space andtime.” of course the sagging mattress analogy can take us only so far because it doesn’tincorporate the effect of time. but then our brains can take us only so far because it is sonearly impossible to envision a dimension comprising three parts space to one part time, allinterwoven like the threads in a plaid fabric. at all events, i think we can agree that this wasan awfully big thought for a young man staring out the window of a patent office in thecapital of switzerland. among much else, einstein’s general theory of relativity suggested that the universe mustbe either expanding or contracting. but einstein was not a cosmologist, and he accepted theprevailing wisdom that the universe was fixed and eternal. more or less reflexively, hedropped into his equations something called the cosmological constant, which arbitrarilycounterbalanced the effects of gravity, serving as a kind of mathematical pause button. bookson the history of science always forgive einstein this lapse, but it was actually a fairlyappalling piece of science and he knew it. he called it “the biggest blunder of my life.” coincidentally, at about the time that einstein was affixing a cosmological constant to histheory, at the lowell observatory in arizona, an astronomer with the cheerily intergalacticname of vesto slipher (who was in fact from indiana) was taking spectrographic readings ofdistant stars and discovering that they appeared to be moving away from us. the universewasn’t static. the stars slipher looked at showed unmistakable signs of a doppler shift5 thesame mechanism behind that distinctive stretched out yee yummm sound cars make as theyflash past on a racetrack. the phenomenon also applies to light, and in the case of recedinggalaxies it is known as a red shift (because light moving away from us shifts toward the redend of the spectrum; approaching light shifts to blue). slipher was the first to notice this effect with light and to realize its potential importancefor understanding the motions of the cosmos. unfortunately no one much noticed him. thelowell observatory, as you will recall, was a bit of an oddity thanks to percival lowell’sobsession with martian canals, which in the 1910s made it, in every sense, an outpost ofastronomical endeavor. slipher was unaware of einstein’s theory of relativity, and the worldwas equally unaware of slipher. so his finding had no impact. glory instead would pass to a large mass of ego named edwin hubble. hubble was born in1889, ten years after einstein, in a small missouri town on the edge of the ozarks and grewup there and in wheaton, illinois, a suburb of chicago. his father was a successful insuranceexecutive, so life was always comfortable, and edwin enjoyed a wealth of physicalendowments, too. he was a strong and gifted athlete, charming, smart, and immensely good looking “handsome almost to a fault,” in the description of william h. cropper, “an5 named for johann christian doppler, an austrian physicist, who first noticed the effect in 1842. briefly, whathappens is that as a moving object approaches a stationary one its sound waves become bunched up as they cramup against whatever device is receiving them (your ears, say), just as you would expect of anything that is beingpushed from behind toward an immobile object. this bunching is perceived by the listener as a kind of pinchedand elevated sound (the yee). as the sound source passes, the sound waves spread out and lengthen, causing thepitch to drop abruptly (the yummm). adonis” in the words of another admirer. according to his own accounts, he also managed tofit into his life more or less constant acts of valor rescuing drowning swimmers, leadingfrightened men to safety across the battlefields of france, embarrassing world championboxers with knockdown punches in exhibition bouts. it all seemed too good to be true. it was.for all his gifts, hubble was also an inveterate liar. this was more than a little odd, for hubble’s life was filled from an early age with a levelof distinction that was at times almost ludicrously golden. at a single high school track meetin 1906, he won the pole vault, shot put, discus, hammer throw, standing high jump, andrunning high jump, and was on the winning mile relay team that is seven first places in onemeet and came in third in the broad jump. in the same year, he set a state record for the highjump in illinois. as a scholar he was equally proficient, and had no trouble gaining admission to studyphysics and astronomy at the university of chicago (where, coincidentally, the head of thedepartment was now albert michelson). there he was selected to be one of the first rhodesscholars at oxford. three years of english life evidently turned his head, for he returned towheaton in 1913 wearing an inverness cape, smoking a pipe, and talking with a peculiarlyorotund accent not quite british but not quite not that would remain with him for life.though he later claimed to have passed most of the second decade of the century practicinglaw in kentucky, in fact he worked as a high school teacher and basketball coach in newalbany, indiana, before belatedly attaining his doctorate and passing briefly through thearmy. (he arrived in france one month before the armistice and almost certainly never hearda shot fired in anger.) in 1919, now aged thirty, he moved to california and took up a position at the mountwilson observatory near los angeles. swiftly, and more than a little unexpectedly, hebecame the most outstanding astronomer of the twentieth century. it is worth pausing for a moment to consider just how little was known of the cosmos at thistime. astronomers today believe there are perhaps 140 billion galaxies in the visible universe.that’s a huge number, much bigger than merely saying it would lead you to suppose. ifgalaxies were frozen peas, it would be enough to fill a large auditorium the old bostongarden, say, or the royal albert hall. (an astrophysicist named bruce gregory has actuallycomputed this.) in 1919, when hubble first put his head to the eyepiece, the number of thesegalaxies that were known to us was exactly one: the milky way. everything else was thoughtto be either part of the milky way itself or one of many distant, peripheral puffs of gas.hubble quickly demonstrated how wrong that belief was. over the next decade, hubble tackled two of the most fundamental questions of theuniverse: how old is it, and how big? to answer both it is necessary to know two things howfar away certain galaxies are and how fast they are flying away from us (what is known astheir recessional velocity). the red shift gives the speed at which galaxies are retiring, butdoesn’t tell us how far away they are to begin with. for that you need what are known as“standard candles” stars whose brightness can be reliably calculated and used asbenchmarks to measure the brightness (and hence relative distance) of other stars. hubble’s luck was to come along soon after an ingenious woman named henrietta swanleavitt had figured out a way to do so. leavitt worked at the harvard college observatory asa computer, as they were known. computers spent their lives studying photographic plates ofstars and making computations hence the name. it was little more than drudgery by another name, but it was as close as women could get to real astronomy at harvard or indeed prettymuch anywhere in those days. the system, however unfair, did have certain unexpectedbenefits: it meant that half the finest minds available were directed to work that wouldotherwise have attracted little reflective attention, and it ensured that women ended up with anappreciation of the fine structure of the cosmos that often eluded their male counterparts. one harvard computer, annie jump cannon, used her repetitive acquaintance with thestars to devise a system of stellar classifications so practical that it is still in use today.leavitt’s contribution was even more profound. she noticed that a type of star known as acepheid variable (after the constellation cepheus, where it first was identified) pulsated witha regular rhythm a kind of stellar heartbeat. cepheids are quite rare, but at least one of themis well known to most of us. polaris, the pole star, is a cepheid. we now know that cepheids throb as they do because they are elderly stars that havemoved past their “main sequence phase,” in the parlance of astronomers, and become redgiants. the chemistry of red giants is a little weighty for our purposes here (it requires anappreciation for the properties of singly ionized helium atoms, among quite a lot else), but putsimply it means that they burn their remaining fuel in a way that produces a very rhythmic,very reliable brightening and dimming. leavitt’s genius was to realize that by comparing therelative magnitudes of cepheids at different points in the sky you could work out where theywere in relation to each other. they could be used as “standard candles” a term she coinedand still in universal use. the method provided only relative distances, not absolute distances,but even so it was the first time that anyone had come up with a usable way to measure thelarge scale universe. (just to put these insights into perspective, it is perhaps worth noting that at the time leavittand cannon were inferring fundamental properties of the cosmos from dim smudges onphotographic plates, the harvard astronomer william h. pickering, who could of course peerinto a first class telescope as often as he wanted, was developing his seminal theory that darkpatches on the moon were caused by swarms of seasonally migrating insects.) combining leavitt’s cosmic yardstick with vesto slipher’s handy red shifts, edwin hubblenow began to measure selected points in space with a fresh eye. in 1923 he showed that a puffof distant gossamer in the andromeda constellation known as m31 wasn’t a gas cloud at allbut a blaze of stars, a galaxy in its own right, a hundred thousand light years across and atleast nine hundred thousand light years away. the universe was vaster vastly vaster thananyone had ever supposed. in 1924 he produced a landmark paper, “cepheids in spiralnebulae” (nebulae,from the latin for “clouds,” was his word for galaxies), showing that theuniverse consisted not just of the milky way but of lots of independent galaxies “islanduniverses” many of them bigger than the milky way and much more distant. this finding alone would have ensured hubble’s reputation, but he now turned to thequestion of working out just how much vaster the universe was, and made an even morestriking discovery. hubble began to measure the spectra of distant galaxies the business thatslipher had begun in arizona. using mount wilson’s new hundred inch hooker telescopeand some clever inferences, he worked out that all the galaxies in the sky (except for our ownlocal cluster) are moving away from us. moreover, their speed and distance were neatlyproportional: the further away the galaxy, the faster it was moving. this was truly startling. the universe was expanding, swiftly and evenly in all directions. itdidn’t take a huge amount of imagination to read backwards from this and realize that it must therefore have started from some central point. far from being the stable, fixed, eternal voidthat everyone had always assumed, this was a universe that had a beginning. it mighttherefore also have an end. the wonder, as stephen hawking has noted, is that no one had hit on the idea of theexpanding universe before. a static universe, as should have been obvious to newton andevery thinking astronomer since, would collapse in upon itself. there was also the problemthat if stars had been burning indefinitely in a static universe they’d have made the wholeintolerably hot certainly much too hot for the likes of us. an expanding universe resolvedmuch of this at a stroke. hubble was a much better observer than a thinker and didn’t immediately appreciate thefull implications of what he had found. partly this was because he was woefully ignorant ofeinstein’s general theory of relativity. this was quite remarkable because, for one thing,einstein and his theory were world famous by now. moreover, in 1929 albert michelson now in his twilight years but still one of the world’s most alert and esteemed scientists accepted a position at mount wilson to measure the velocity of light with his trustyinterferometer, and must surely have at least mentioned to him the applicability of einstein’stheory to his own findings. at all events, hubble failed to make theoretical hay when the chance was there. instead, itwas left to a belgian priest scholar (with a ph.d. from mit) named georges lemaître tobring together the two strands in his own “fireworks theory,” which suggested that theuniverse began as a geometrical point, a “primeval atom,” which burst into glory and hadbeen moving apart ever since. it was an idea that very neatly anticipated the modernconception of the big bang but was so far ahead of its time that lemaître seldom gets morethan the sentence or two that we have given him here. the world would need additionaldecades, and the inadvertent discovery of cosmic background radiation by penzias and wilsonat their hissing antenna in new jersey, before the big bang would begin to move frominteresting idea to established theory. neither hubble nor einstein would be much of a part of that big story. though no onewould have guessed it at the time, both men had done about as much as they were ever goingto do. in 1936 hubble produced a popular book called the realm of the nebulae, whichexplained in flattering style his own considerable achievements. here at last he showed thathe had acquainted himself with einstein’s theory up to a point anyway: he gave it four pagesout of about two hundred. hubble died of a heart attack in 1953. one last small oddity awaited him. for reasonscloaked in mystery, his wife declined to have a funeral and never revealed what she did withhis body. half a century later the whereabouts of the century’s greatest astronomer remainunknown. for a memorial you must look to the sky and the hubble space telescope,launched in 1990 and named in his honor. 9 the mighty atomwhile einstein and hubble were productively unraveling the large scale structure ofthe cosmos, others were struggling to understand something closer to hand but in its way justas remote: the tiny and ever  mysterious atom. the great caltech physicist richard feynman once observed that if you had to reducescientific history to one important statement it would be “all things are made of atoms.” theyare everywhere and they constitute every thing. look around you. it is all atoms. not just thesolid things like walls and tables and sofas, but the air in between. and they are there innumbers that you really cannot conceive. the basic working arrangement of atoms is the molecule (from the latin for “little mass”).a molecule is simply two or more atoms working together in a more or less stablearrangement: add two atoms of hydrogen to one of oxygen and you have a molecule of water.chemists tend to think in terms of molecules rather than elements in much the way thatwriters tend to think in terms of words and not letters, so it is molecules they count, and theseare numerous to say the least. at sea level, at a temperature of 32 degrees fahrenheit, onecubic centimeter of air (that is, a space about the size of a sugar cube) will contain 45 billionbillion molecules. and they are in every single cubic centimeter you see around you. thinkhow many cubic centimeters there are in the world outside your window how many sugarcubes it would take to fill that view. then think how many it would take to build a universe.atoms, in short, are very abundant. they are also fantastically durable. because they are so long lived, atoms really get around.every atom you possess has almost certainly passed through several stars and been part ofmillions of organisms on its way to becoming you. we are each so atomically numerous andso vigorously recycled at death that a significant number of our atoms up to a billion foreach of us, it has been suggested probably once belonged to shakespeare. a billion moreeach came from buddha and genghis khan and beethoven, and any other historical figureyou care to name. (the personages have to be historical, apparently, as it takes the atomssome decades to become thoroughly redistributed; however much you may wish it, you arenot yet one with elvis presley.) so we are all reincarnations though short lived ones. when we die our atoms willdisassemble and move off to find new uses elsewhere as part of a leaf or other human beingor drop of dew. atoms, however, go on practically forever. nobody actually knows how longan atom can survive, but according to martin rees it is probably about 1035years a numberso big that even i am happy to express it in notation. above all, atoms are tiny very tiny indeed. half a million of them lined up shoulder toshoulder could hide behind a human hair. on such a scale an individual atom is essentiallyimpossible to imagine, but we can of course try. start with a millimeter, which is a line this long:  . now imagine that line divided into athousand equal widths. each of those widths is a micron. this is the scale of microorganisms.a typical paramecium, for instance, is about two microns wide, 0.002 millimeters, which isreally very small. if you wanted to see with your naked eye a paramecium swimming in adrop of water, you would have to enlarge the drop until it was some forty feet across.however, if you wanted to see the atoms in the same drop, you would have to make the dropfifteen miles across. atoms, in other words, exist on a scale of minuteness of another order altogether. to getdown to the scale of atoms, you would need to take each one of those micron slices and shaveit into ten thousand finer widths. that’s the scale of an atom: one ten millionth of amillimeter. it is a degree of slenderness way beyond the capacity of our imaginations, but youcan get some idea of the proportions if you bear in mind that one atom is to the width of amillimeter line as the thickness of a sheet of paper is to the height of the empire statebuilding. it is of course the abundance and extreme durability of atoms that makes them so useful,and the tininess that makes them so hard to detect and understand. the realization that atomsare these three things small, numerous, practically indestructible and that all things aremade from them first occurred not to antoine laurent lavoisier, as you might expect, or evento henry cavendish or humphry davy, but rather to a spare and lightly educated englishquaker named john dalton, whom we first encountered in the chapter on chemistry. dalton was born in 1766 on the edge of the lake district near cockermouth to a family ofpoor but devout quaker weavers. (four years later the poet william wordsworth would alsojoin the world at cockermouth.) he was an exceptionally bright student so very brightindeed that at the improbably youthful age of twelve he was put in charge of the local quakerschool. this perhaps says as much about the school as about dalton’s precocity, but perhapsnot: we know from his diaries that at about this time he was reading newton’s principia in theoriginal latin and other works of a similarly challenging nature. at fifteen, stillschoolmastering, he took a job in the nearby town of kendal, and a decade after that hemoved to manchester, scarcely stirring from there for the remaining fifty years of his life. inmanchester he became something of an intellectual whirlwind, producing books and paperson subjects ranging from meteorology to grammar. color blindness, a condition from whichhe suffered, was for a long time called daltonism because of his studies. but it was a plumpbook called a new system of chemical philosophy, published in 1808, that established hisreputation. there, in a short chapter of just five pages (out of the book’s more than nine hundred),people of learning first encountered atoms in something approaching their modernconception. dalton’s simple insight was that at the root of all matter are exceedingly tiny,irreducible particles. “we might as well attempt to introduce a new planet into the solarsystem or annihilate one already in existence, as to create or destroy a particle of hydrogen,”he wrote. neither the idea of atoms nor the term itself was exactly new. both had been developed bythe ancient greeks. dalton’s contribution was to consider the relative sizes and characters ofthese atoms and how they fit together. he knew, for instance, that hydrogen was the lightestelement, so he gave it an atomic weight of one. he believed also that water consisted of sevenparts of oxygen to one of hydrogen, and so he gave oxygen an atomic weight of seven. bysuch means was he able to arrive at the relative weights of the known elements. he wasn’talways terribly accurate oxygen’s atomic weight is actually sixteen, not seven but theprinciple was sound and formed the basis for all of modern chemistry and much of the rest ofmodern science. the work made dalton famous albeit in a low key, english quaker sort of way. in 1826,the french chemist p .j. pelletier traveled to manchester to meet the atomic hero. pelletierexpected to find him attached to some grand institution, so he was astounded to discover himteaching elementary arithmetic to boys in a small school on a back street. according to the scientific historian e. j. holmyard, a confused pelletier, upon beholding the great man,stammered: “est ce que j’ai l’honneur de m’addresser à monsieur dalton?” for he could hardly believe his eyes that this was the chemist of european fame, teaching a boy his first four rules. “yes,” said the matter of fact quaker. “wilt thou sit down whilst i put this lad right about his arithmetic?” although dalton tried to avoid all honors, he was elected to the royal society against hiswishes, showered with medals, and given a handsome government pension. when he died in1844, forty thousand people viewed the coffin, and the funeral cortege stretched for twomiles. his entry in the dictionary of national biography is one of the longest, rivaled inlength only by those of darwin and lyell among nineteenth century men of science. for a century after dalton made his proposal, it remained entirely hypothetical, and a feweminent scientists notably the viennese physicist ernst mach, for whom is named the speedof sound doubted the existence of atoms at all. “atoms cannot be perceived by the senses . .. they are things of thought,” he wrote. the existence of atoms was so doubtfully held in thegerman speaking world in particular that it was said to have played a part in the suicide of thegreat theoretical physicist, and atomic enthusiast, ludwig boltzmann in 1906. it was einstein who provided the first incontrovertible evidence of atoms’ existence withhis paper on brownian motion in 1905, but this attracted little attention and in any caseeinstein was soon to become consumed with his work on general relativity. so the first realhero of the atomic age, if not the first personage on the scene, was ernest rutherford. rutherford was born in 1871 in the “back blocks” of new zealand to parents who hademigrated from scotland to raise a little flax and a lot of children (to paraphrase stevenweinberg). growing up in a remote part of a remote country, he was about as far from themainstream of science as it was possible to be, but in 1895 he won a scholarship that took himto the cavendish laboratory at cambridge university, which was about to become the hottestplace in the world to do physics. physicists are notoriously scornful of scientists from other fields. when the wife of thegreat austrian physicist wolfgang pauli left him for a chemist, he was staggered withdisbelief. “had she taken a bullfighter i would have understood,” he remarked in wonder to afriend. “but a chemist . . .” it was a feeling rutherford would have understood. “all science is either physics or stampcollecting,” he once said, in a line that has been used many times since. there is a certainengaging irony therefore that when he won the nobel prize in 1908, it was in chemistry, notphysics. rutherford was a lucky man lucky to be a genius, but even luckier to live at a time whenphysics and chemistry were so exciting and so compatible (his own sentimentsnotwithstanding). never again would they quite so comfortably overlap. for all his success, rutherford was not an especially brilliant man and was actually prettyterrible at mathematics. often during lectures he would get so lost in his own equations thathe would give up halfway through and tell the students to work it out for themselves.according to his longtime colleague james chadwick, discoverer of the neutron, he wasn’teven particularly clever at experimentation. he was simply tenacious and open minded. forbrilliance he substituted shrewdness and a kind of daring. his mind, in the words of onebiographer, was “always operating out towards the frontiers, as far as he could see, and thatwas a great deal further than most other men.” confronted with an intractable problem, hewas prepared to work at it harder and longer than most people and to be more receptive tounorthodox explanations. his greatest breakthrough came because he was prepared to spendimmensely tedious hours sitting at a screen counting alpha particle scintillations, as they wereknown the sort of work that would normally have been farmed out. he was one of the firstto see possibly the very first that the power inherent in the atom could, if harnessed, makebombs powerful enough to “make this old world vanish in smoke.” physically he was big and booming, with a voice that made the timid shrink. once whentold that rutherford was about to make a radio broadcast across the atlantic, a colleague drilyasked: “why use radio?” he also had a huge amount of good natured confidence. whensomeone remarked to him that he seemed always to be at the crest of a wave, he responded,“well, after all, i made the wave, didn’t i?” c. p. snow recalled how once in a cambridgetailor’s he overheard rutherford remark: “every day i grow in girth. and in mentality.” but both girth and fame were far ahead of him in 1895 when he fetched up at thecavendish.1 it was a singularly eventful period in science. in the year of his arrival incambridge, wilhelm roentgen discovered x rays at the university of würzburg in germany,and the next year henri becquerel discovered radioactivity. and the cavendish itself wasabout to embark on a long period of greatness. in 1897, j. j. thomson and colleagues woulddiscover the electron there, in 1911 c. t. r. wilson would produce the first particle detectorthere (as we shall see), and in 1932 james chadwick would discover the neutron there.further still in the future, james watson and francis crick would discover the structure ofdna at the cavendish in 1953. in the beginning rutherford worked on radio waves, and with some distinction hemanaged to transmit a crisp signal more than a mile, a very reasonable achievement for thetime but gave it up when he was persuaded by a senior colleague that radio had little future.on the whole, however, rutherford didn’t thrive at the cavendish. after three years there,feeling he was going nowhere, he took a post at mcgill university in montreal, and there hebegan his long and steady rise to greatness. by the time he received his nobel prize (for“investigations into the disintegration of the elements, and the chemistry of radioactivesubstances,” according to the official citation) he had moved on to manchester university,and it was there, in fact, that he would do his most important work in determining thestructure and nature of the atom.1 the name comes from the same cavendishes who producec henry. this one was william cavendish, seventhduke of devonshire, who was a gifted mathematician and steel baron in victoriar england. in 1870, he gave theuniversity £6,300 to build an experimental lab. by the early twentieth century it was known that atoms were made of parts thomson’sdiscovery of the electron had established that but it wasn’t known how many parts therewere or how they fit together or what shape they took. some physicists thought that atomsmight be cube shaped, because cubes can be packed together so neatly without any wastedspace. the more general view, however, was that an atom was more like a currant bun or aplum pudding: a dense, solid object that carried a positive charge but that was studded withnegatively charged electrons, like the currants in a currant bun. in 1910, rutherford (assisted by his student hans geiger, who would later invent theradiation detector that bears his name) fired ionized helium atoms, or alpha particles, at asheet of gold foil.2 to rutherford’s astonishment, some of the particles bounced back. it wasas if, he said, he had fired a fifteen inch shell at a sheet of paper and it rebounded into his lap.this was just not supposed to happen. after considerable reflection he realized there could beonly one possible explanation: the particles that bounced back were striking something smalland dense at the heart of the atom, while the other particles sailed through unimpeded. anatom, rutherford realized, was mostly empty space, with a very dense nucleus at the center.this was a most gratifying discovery, but it presented one immediate problem. by all the lawsof conventional physics, atoms shouldn’t therefore exist. let us pause for a moment and consider the structure of the atom as we know it now. everyatom is made from three kinds of elementary particles: protons, which have a positiveelectrical charge; electrons, which have a negative electrical charge; and neutrons, which haveno charge. protons and neutrons are packed into the nucleus, while electrons spin aroundoutside. the number of protons is what gives an atom its chemical identity. an atom with oneproton is an atom of hydrogen, one with two protons is helium, with three protons is lithium,and so on up the scale. each time you add a proton you get a new element. (because thenumber of protons in an atom is always balanced by an equal number of electrons, you willsometimes see it written that it is the number of electrons that defines an element; it comes tothe same thing. the way it was explained to me is that protons give an atom its identity,electrons its personality.) neutrons don’t influence an atom’s identity, but they do add to its mass. the number ofneutrons is generally about the same as the number of protons, but they can vary up and downslightly. add a neutron or two and you get an isotope. the terms you hear in reference todating techniques in archeology refer to isotopes carbon 14, for instance, which is an atomof carbon with six protons and eight neutrons (the fourteen being the sum of the two). neutrons and protons occupy the atom’s nucleus. the nucleus of an atom is tiny only onemillionth of a billionth of the full volume of the atom but fantastically dense, since itcontains virtually all the atom’s mass. as cropper has put it, if an atom were expanded to thesize of a cathedral, the nucleus would be only about the size of a fly but a fly manythousands of times heavier than the cathedral. it was this spaciousness this resounding,unexpected roominess that had rutherford scratching his head in 1910. it is still a fairly astounding notion to consider that atoms are mostly empty space, and thatthe solidity we experience all around us is an illusion. when two objects come together in the2 geiger would also later become a loyal nazi, unhesitatingly betraying jewish colleagues, including many whohad helped him. real world billiard balls are most often used for illustration they don’t actually strike eachother. “rather,” as timothy ferris explains, “the negatively charged fields of the two ballsrepel each other . . . were it not for their electrical charges they could, like galaxies, pass rightthrough each other unscathed.” when you sit in a chair, you are not actually sitting there, butlevitating above it at a height of one angstrom (a hundred millionth of a centimeter), yourelectrons and its electrons implacably opposed to any closer intimacy. the picture that nearly everybody has in mind of an atom is of an electron or two flyingaround a nucleus, like planets orbiting a sun. this image was created in 1904, based on littlemore than clever guesswork, by a japanese physicist named hantaro nagaoka. it iscompletely wrong, but durable just the same. as isaac asimov liked to note, it inspiredgenerations of science fiction writers to create stories of worlds within worlds, in which atomsbecome tiny inhabited solar systems or our solar system turns out to be merely a mote in somemuch larger scheme. even now cern, the european organization for nuclear research, usesnagaoka’s image as a logo on its website. in fact, as physicists were soon to realize, electronsare not like orbiting planets at all, but more like the blades of a spinning fan, managing to fillevery bit of space in their orbits simultaneously (but with the crucial difference that the bladesof a fan only seem to be everywhere at once; electrons are ). needless to say, very little of this was understood in 1910 or for many years afterward.rutherford’s finding presented some large and immediate problems, not least that no electronshould be able to orbit a nucleus without crashing. conventional electrodynamic theorydemanded that a flying electron should very quickly run out of energy in only an instant orso and spiral into the nucleus, with disastrous consequences for both. there was also theproblem of how protons with their positive charges could bundle together inside the nucleuswithout blowing themselves and the rest of the atom apart. clearly whatever was going ondown there in the world of the very small was not governed by the laws that applied in themacro world where our expectations reside. as physicists began to delve into this subatomic realm, they realized that it wasn’t merelydifferent from anything we knew, but different from anything ever imagined. “becauseatomic behavior is so unlike ordinary experience,” richard feynman once observed, “it isvery difficult to get used to and it appears peculiar and mysterious to everyone, both to thenovice and to the experienced physicist.” when feynman made that comment, physicists hadhad half a century to adjust to the strangeness of atomic behavior. so think how it must havefelt to rutherford and his colleagues in the early 1910s when it was all brand new. one of the people working with rutherford was a mild and affable young dane namedniels bohr. in 1913, while puzzling over the structure of the atom, bohr had an idea soexciting that he postponed his honeymoon to write what became a landmark paper. becausephysicists couldn’t see anything so small as an atom, they had to try to work out its structurefrom how it behaved when they did things to it, as rutherford had done by firing alphaparticles at foil. sometimes, not surprisingly, the results of these experiments were puzzling.one puzzle that had been around for a long time had to do with spectrum readings of thewavelengths of hydrogen. these produced patterns showing that hydrogen atoms emittedenergy at certain wavelengths but not others. it was rather as if someone under surveillancekept turning up at particular locations but was never observed traveling between them. no onecould understand why this should be. it was while puzzling over this problem that bohr was struck by a solution and dashed offhis famous paper. called “on the constitutions of atoms and molecules,” the paper explainedhow electrons could keep from falling into the nucleus by suggesting that they could occupyonly certain well defined orbits. according to the new theory, an electron moving betweenorbits would disappear from one and reappear instantaneously in another without visiting thespace between. this idea the famous “quantum leap” is of course utterly strange, but itwas too good not to be true. it not only kept electrons from spiraling catastrophically into thenucleus; it also explained hydrogen’s bewildering wavelengths. the electrons only appearedin certain orbits because they only existed in certain orbits. it was a dazzling insight, and itwon bohr the 1922 nobel prize in physics, the year after einstein received his. meanwhile the tireless rutherford, now back at cambridge as j. j. thomson’s successor ashead of the cavendish laboratory, came up with a model that explained why the nuclei didn’tblow up. he saw that they must be offset by some type of neutralizing particles, which hecalled neutrons. the idea was simple and appealing, but not easy to prove. rutherford’sassociate, james chadwick, devoted eleven intensive years to hunting for neutrons beforefinally succeeding in 1932. he, too, was awarded with a nobel prize in physics, in 1935. asboorse and his colleagues point out in their history of the subject, the delay in discovery wasprobably a very good thing as mastery of the neutron was essential to the development of theatomic bomb. (because neutrons have no charge, they aren’t repelled by the electrical fields atthe heart of an atom and thus could be fired like tiny torpedoes into an atomic nucleus, settingoff the destructive process known as fission.) had the neutron been isolated in the 1920s, theynote, it is “very likely the atomic bomb would have been developed first in europe,undoubtedly by the germans.” as it was, the europeans had their hands full trying to understand the strange behavior ofthe electron. the principal problem they faced was that the electron sometimes behaved like aparticle and sometimes like a wave. this impossible duality drove physicists nearly mad. forthe next decade all across europe they furiously thought and scribbled and offered competinghypotheses. in france, prince louis victor de broglie, the scion of a ducal family, found thatcertain anomalies in the behavior of electrons disappeared when one regarded them as waves.the observation excited the attention of the austrian erwin schrödinger, who made some deftrefinements and devised a handy system called wave mechanics. at almost the same time thegerman physicist werner heisenberg came up with a competing theory called matrixmechanics. this was so mathematically complex that hardly anyone really understood it,including heisenberg himself (“i do not even know what a matrix is ,” heisenberg despairedto a friend at one point), but it did seem to solve certain problems that schrödinger’s wavesfailed to explain. the upshot is that physics had two theories, based on conflicting premises,that produced the same results. it was an impossible situation. finally, in 1926, heisenberg came up with a celebrated compromise, producing a newdiscipline that came to be known as quantum mechanics. at the heart of it was heisenberg’suncertainty principle, which states that the electron is a particle but a particle that can bedescribed in terms of waves. the uncertainty around which the theory is built is that we canknow the path an electron takes as it moves through a space or we can know where it is at agiven instant, but we cannot know both.3 any attempt to measure one will unavoidably3 there is a little uncertainty about the use of the word uncertainty in regard to heisenberg's principle. michaelfrayn, in an afterword to his play copenhagen, notes that several words in german unsicherheit, unscharfe,unbestimmtheit have been used by various translators, but that none quite equates to the english uncertainty.frayn suggests that indeterminacy would be a better word for the principle and indeterminability would be betterstill. disturb the other. this isn’t a matter of simply needing more precise instruments; it is animmutable property of the universe. what this means in practice is that you can never predict where an electron will be at anygiven moment. you can only list its probability of being there. in a sense, as dennis overbyehas put it, an electron doesn’t exist until it is observed. or, put slightly differently, until it isobserved an electron must be regarded as being “at once everywhere and nowhere.” if this seems confusing, you may take some comfort in knowing that it was confusing tophysicists, too. overbye notes: “bohr once commented that a person who wasn’t outraged onfirst hearing about quantum theory didn’t understand what had been said.” heisenberg, whenasked how one could envision an atom, replied: “don’t try.” so the atom turned out to be quite unlike the image that most people had created. theelectron doesn’t fly around the nucleus like a planet around its sun, but instead takes on themore amorphous aspect of a cloud. the “shell” of an atom isn’t some hard shiny casing, asillustrations sometimes encourage us to suppose, but simply the outermost of these fuzzyelectron clouds. the cloud itself is essentially just a zone of statistical probability marking thearea beyond which the electron only very seldom strays. thus an atom, if you could see it,would look more like a very fuzzy tennis ball than a hard edged metallic sphere (but not muchlike either or, indeed, like anything you’ve ever seen; we are, after all, dealing here with aworld very different from the one we see around us). it seemed as if there was no end of strangeness. for the first time, as james trefil has put it,scientists had encountered “an area of the universe that our brains just aren’t wired tounderstand.” or as feynman expressed it, “things on a small scale behave nothing like thingson a large scale.” as physicists delved deeper, they realized they had found a world where notonly could electrons jump from one orbit to another without traveling across any interveningspace, but matter could pop into existence from nothing at all “provided,” in the words ofalan lightman of mit, “it disappears again with sufficient haste.” perhaps the most arresting of quantum improbabilities is the idea, arising from wolfgangpauli’s exclusion principle of 1925, that the subatomic particles in certain pairs, even whenseparated by the most considerable distances, can each instantly “know” what the other isdoing. particles have a quality known as spin and, according to quantum theory, the momentyou determine the spin of one particle, its sister particle, no matter how distant away, willimmediately begin spinning in the opposite direction and at the same rate. it is as if, in the words of the science writer lawrence joseph, you had two identical poolballs, one in ohio and the other in fiji, and the instant you sent one spinning the other wouldimmediately spin in a contrary direction at precisely the same speed. remarkably, thephenomenon was proved in 1997 when physicists at the university of geneva sent photonsseven miles in opposite directions and demonstrated that interfering with one provoked aninstantaneous response in the other. things reached such a pitch that at one conference bohr remarked of a new theory that thequestion was not whether it was crazy, but whether it was crazy enough. to illustrate thenonintuitive nature of the quantum world, schrödinger offered a famous thought experimentin which a hypothetical cat was placed in a box with one atom of a radioactive substanceattached to a vial of hydrocyanic acid. if the particle degraded within an hour, it would triggera mechanism that would break the vial and poison the cat. if not, the cat would live. but we could not know which was the case, so there was no choice, scientifically, but to regard thecat as 100 percent alive and 100 percent dead at the same time. this means, as stephenhawking has observed with a touch of understandable excitement, that one cannot “predictfuture events exactly if one cannot even measure the present state of the universe precisely!” because of its oddities, many physicists disliked quantum theory, or at least certain aspectsof it, and none more so than einstein. this was more than a little ironic since it was he, in hisannus mirabilis of 1905, who had so persuasively explained how photons of light couldsometimes behave like particles and sometimes like waves the notion at the very heart of thenew physics. “quantum theory is very worthy of regard,” he observed politely, but he reallydidn’t like it. “god doesn’t play dice,” he said.4 einstein couldn’t bear the notion that god could create a universe in which some thingswere forever unknowable. moreover, the idea of action at a distance that one particle couldinstantaneously influence another trillions of miles away was a stark violation of the specialtheory of relativity. this expressly decreed that nothing could outrace the speed of light andyet here were physicists insisting that, somehow, at the subatomic level, information could.(no one, incidentally, has ever explained how the particles achieve this feat. scientists havedealt with this problem, according to the physicist yakir aharanov, “by not thinking aboutit.”) above all, there was the problem that quantum physics introduced a level of untidiness thathadn’t previously existed. suddenly you needed two sets of laws to explain the behavior ofthe universe quantum theory for the world of the very small and relativity for the largeruniverse beyond. the gravity of relativity theory was brilliant at explaining why planetsorbited suns or why galaxies tended to cluster, but turned out to have no influence at all at theparticle level. to explain what kept atoms together, other forces were needed, and in the1930s two were discovered: the strong nuclear force and weak nuclear force. the strong forcebinds atoms together; it’s what allows protons to bed down together in the nucleus. the weakforce engages in more miscellaneous tasks, mostly to do with controlling the rates of certainsorts of radioactive decay. the weak nuclear force, despite its name, is ten billion billion billion times stronger thangravity, and the strong nuclear force is more powerful still vastly so, in fact but theirinfluence extends to only the tiniest distances. the grip of the strong force reaches out only toabout 1/100,000 of the diameter of an atom. that’s why the nuclei of atoms are so compactedand dense and why elements with big, crowded nuclei tend to be so unstable: the strong forcejust can’t hold on to all the protons. the upshot of all this is that physics ended up with two bodies of laws one for the worldof the very small, one for the universe at large leading quite separate lives. einstein dislikedthat, too. he devoted the rest of his life to searching for a way to tie up these loose ends byfinding a grand unified theory, and always failed. from time to time he thought he had it, butit always unraveled on him in the end. as time passed he became increasingly marginalizedand even a little pitied. almost without exception, wrote snow, “his colleagues thought, andstill think, that he wasted the second half of his life.”4 or at least that is how it is nearly always rendered. the actual quote was: “it seems hard to sneak a look atgod’s cards. but that he plays dice and uses ‘telepathic’ methods. . . is something that i cannot believe for asingle moment.” elsewhere, however, real progress was being made. by the mid 1940s scientists hadreached a point where they understood the atom at an extremely profound level as they alltoo effectively demonstrated in august 1945 by exploding a pair of atomic bombs over japan. by this point physicists could be excused for thinking that they had just about conqueredthe atom. in fact, everything in particle physics was about to get a whole lot morecomplicated. but before we take up that slightly exhausting story, we must bring anotherstraw of our history up to date by considering an important and salutary tale of avarice, deceit,bad science, several needless deaths, and the final determination of the age of the earth. 10 getting the lead outin the late 1940s, a graduate student at the university of chicago named clair patterson(who was, first name notwithstanding, an iowa farm boy by origin) was using a new methodof lead isotope measurement to try to get a definitive age for the earth at last. unfortunatelyall his samples came up contaminated usually wildly so. most contained something like twohundred times the levels of lead that would normally be expected to occur. many years wouldpass before patterson realized that the reason for this lay with a regrettable ohio inventornamed thomas midgley, jr. midgley was an engineer by training, and the world would no doubt have been a safer placeif he had stayed so. instead, he developed an interest in the industrial applications ofchemistry. in 1921, while working for the general motors research corporation in dayton,ohio, he investigated a compound called tetraethyl lead (also known, confusingly, as leadtetraethyl), and discovered that it significantly reduced the juddering condition known asengine knock. even though lead was widely known to be dangerous, by the early years of the twentiethcentury it could be found in all manner of consumer products. food came in cans sealed withlead solder. water was often stored in lead lined tanks. it was sprayed onto fruit as a pesticidein the form of lead arsenate. it even came as part of the packaging of toothpaste tubes. hardlya product existed that didn’t bring a little lead into consumers’ lives. however, nothing gave ita greater and more lasting intimacy than its addition to gasoline. lead is a neurotoxin. get too much of it and you can irreparably damage the brain andcentral nervous system. among the many symptoms associated with overexposure areblindness, insomnia, kidney failure, hearing loss, cancer, palsies, and convulsions. in its mostacute form it produces abrupt and terrifying hallucinations, disturbing to victims andonlookers alike, which generally then give way to coma and death. you really don’t want toget too much lead into your system. on the other hand, lead was easy to extract and work, and almost embarrassingly profitableto produce industrially and tetraethyl lead did indubitably stop engines from knocking. so in1923 three of america’s largest corporations, general motors, du pont, and standard oil ofnew jersey, formed a joint enterprise called the ethyl gasoline corporation (later shortenedto simply ethyl corporation) with a view to making as much tetraethyl lead as the world waswilling to buy, and that proved to be a very great deal. they called their additive “ethyl”because it sounded friendlier and less toxic than “lead” and introduced it for publicconsumption (in more ways than most people realized) on february 1, 1923. almost at once production workers began to exhibit the staggered gait and confusedfaculties that mark the recently poisoned. also almost at once, the ethyl corporationembarked on a policy of calm but unyielding denial that would serve it well for decades. assharon bertsch mcgrayne notes in her absorbing history of industrial chemistry,prometheans in the lab, when employees at one plant developed irreversible delusions, a spokesman blandly informed reporters: “these men probably went insane because theyworked too hard.” altogether at least fifteen workers died in the early days of production ofleaded gasoline, and untold numbers of others became ill, often violently so; the exactnumbers are unknown because the company nearly always managed to hush up news ofembarrassing leakages, spills, and poisonings. at times, however, suppressing the newsbecame impossible, most notably in 1924 when in a matter of days five production workersdied and thirty five more were turned into permanent staggering wrecks at a single ill ventilated facility. as rumors circulated about the dangers of the new product, ethyl’s ebullient inventor,thomas midgley, decided to hold a demonstration for reporters to allay their concerns. as hechatted away about the company’s commitment to safety, he poured tetraethyl lead over hishands, then held a beaker of it to his nose for sixty seconds, claiming all the while that hecould repeat the procedure daily without harm. in fact, midgley knew only too well the perilsof lead poisoning: he had himself been made seriously ill from overexposure a few monthsearlier and now, except when reassuring journalists, never went near the stuff if he could helpit. buoyed by the success of leaded gasoline, midgley now turned to another technologicalproblem of the age. refrigerators in the 1920s were often appallingly risky because they useddangerous gases that sometimes leaked. one leak from a refrigerator at a hospital incleveland, ohio, in 1929 killed more than a hundred people. midgley set out to create a gasthat was stable, nonflammable, noncorrosive, and safe to breathe. with an instinct for theregrettable that was almost uncanny, he invented chlorofluorocarbons, or cfcs. seldom has an industrial product been more swiftly or unfortunately embraced. cfcs wentinto production in the early 1930s and found a thousand applications in everything from carair conditioners to deodorant sprays before it was noticed, half a century later, that they weredevouring the ozone in the stratosphere. as you will be aware, this was not a good thing. ozone is a form of oxygen in which each molecule bears three atoms of oxygen instead oftwo. it is a bit of a chemical oddity in that at ground level it is a pollutant, while way up in thestratosphere it is beneficial, since it soaks up dangerous ultraviolet radiation. beneficial ozoneis not terribly abundant, however. if it were distributed evenly throughout the stratosphere, itwould form a layer just one eighth of an inch or so thick. that is why it is so easily disturbed,and why such disturbances don’t take long to become critical. chlorofluorocarbons are also not very abundant they constitute only about one part perbillion of the atmosphere as a whole but they are extravagantly destructive. one pound ofcfcs can capture and annihilate seventy thousand pounds of atmospheric ozone. cfcs alsohang around for a long time about a century on average wreaking havoc all the while.they are also great heat sponges. a single cfc molecule is about ten thousand times moreefficient at exacerbating greenhouse effects than a molecule of carbon dioxide and carbondioxide is of course no slouch itself as a greenhouse gas. in short, chlorofluorocarbons mayultimately prove to be just about the worst invention of the twentieth century. midgley never knew this because he died long before anyone realized how destructivecfcs were. his death was itself memorably unusual. after becoming crippled with polio,midgley invented a contraption involving a series of motorized pulleys that automatically raised or turned him in bed. in 1944, he became entangled in the cords as the machine wentinto action and was strangled. if you were interested in finding out the ages of things, the university of chicago in the1940s was the place to be. willard libby was in the process of inventing radiocarbon dating,allowing scientists to get an accurate reading of the age of bones and other organic remains,something they had never been able to do before. up to this time, the oldest reliable dateswent back no further than the first dynasty in egypt from about 3000b.c. no one couldconfidently say, for instance, when the last ice sheets had retreated or at what time in the pastthe cro magnon people had decorated the caves of lascaux in france. libby’s idea was so useful that he would be awarded a nobel prize for it in 1960. it wasbased on the realization that all living things have within them an isotope of carbon calledcarbon 14, which begins to decay at a measurable rate the instant they die. carbon 14 has ahalf life that is, the time it takes for half of any sample to disappear1 of about 5,600 years,so by working out how much a given sample of carbon had decayed, libby could get a goodfix on the age of an object though only up to a point. after eight half lives, only 1/256 of theoriginal radioactive carbon remains, which is too little to make a reliable measurement, soradiocarbon dating works only for objects up to forty thousand or so years old. curiously, just as the technique was becoming widespread, certain flaws within it becameapparent. to begin with, it was discovered that one of the basic components of libby’sformula, known as the decay constant, was off by about 3 percent. by this time, however,thousands of measurements had been taken throughout the world. rather than restate everyone, scientists decided to keep the inaccurate constant. “thus,” tim flannery notes, “everyraw radiocarbon date you read today is given as too young by around 3 percent.” theproblems didn’t quite stop there. it was also quickly discovered that carbon 14 samples can beeasily contaminated with carbon from other sources a tiny scrap of vegetable matter, forinstance, that has been collected with the sample and not noticed. for younger samples those under twenty thousand years or so slight contamination does not always matter somuch, but for older samples it can be a serious problem because so few remaining atoms arebeing counted. in the first instance, to borrow from flannery, it is like miscounting by a dollarwhen counting to a thousand; in the second it is more like miscounting by a dollar when youhave only two dollars to count. libby’s method was also based on the assumption that the amount of carbon 14 in theatmosphere, and the rate at which it has been absorbed by living things, has been consistentthroughout history. in fact it hasn’t been. we now know that the volume of atmosphericcarbon 14 varies depending on how well or not earth’s magnetism is deflecting cosmic rays,and that that can vary significantly over time. this means that some carbon 14 dates are more1 if you have ever wondered how the atoms determine which 50 percent will die and which 50 percent willsurvive for the next session, the answer is that the half life is really just a statistical convenience a kind ofactuarial table for elemental things. imagine you had a sample of material with a half life of 30 seconds. it isn'tthat every atom in the sample will exist for exactly 30 seconds or 60 seconds or 90 seconds or some other tidilyordained period. each atom will in fact survive for an entirely random length of time that has nothing to do withmultiples of 30; it might last until two seconds from now or it might oscillate away for years or decades orcenturies to come. no one can say. but what we can say is that for the sample as a whole the rate ofdisappearance will be such that half the atoms will disappear every 30 seconds. it's an average rate, in otherwords, and you can apply it to any large sampling. someone once worked out, for instance, that dimes have ahalf life of about 30 years. dubious than others. this is particularly so with dates just around the time that people firstcame to the americas, which is one of the reasons the matter is so perennially in dispute. finally, and perhaps a little unexpectedly, readings can be thrown out by seeminglyunrelated external factors such as the diets of those whose bones are being tested. onerecent case involved the long running debate over whether syphilis originated in the newworld or the old. archeologists in hull, in the north of england, found that monks in amonastery graveyard had suffered from syphilis, but the initial conclusion that the monks haddone so before columbus’s voyage was cast into doubt by the realization that they had eaten alot of fish, which could make their bones appear to be older than in fact they were. the monksmay well have had syphilis, but how it got to them, and when, remain tantalizinglyunresolved. because of the accumulated shortcomings of carbon 14, scientists devised other methods ofdating ancient materials, among them thermoluminesence, which measures electrons trappedin clays, and electron spin resonance, which involves bombarding a sample withelectromagnetic waves and measuring the vibrations of the electrons. but even the best ofthese could not date anything older than about 200,000 years, and they couldn’t date inorganicmaterials like rocks at all, which is of course what you need if you wish to determine the ageof your planet. the problems of dating rocks were such that at one point almost everyone in the world hadgiven up on them. had it not been for a determined english professor named arthur holmes,the quest might well have fallen into abeyance altogether. holmes was heroic as much for the obstacles he overcame as for the results he achieved.by the 1920s, when holmes was in the prime of his career, geology had slipped out offashion physics was the new excitement of the age and had become severely underfunded,particularly in britain, its spiritual birthplace. at durham university, holmes was for manyyears the entire geology department. often he had to borrow or patch together equipment inorder to pursue his radiometric dating of rocks. at one point, his calculations were effectivelyheld up for a year while he waited for the university to provide him with a simple addingmachine. occasionally, he had to drop out of academic life altogether to earn enough tosupport his family for a time he ran a curio shop in newcastle upon tyne and sometimeshe could not even afford the £5 annual membership fee for the geological society. the technique holmes used in his work was theoretically straightforward and arose directlyfrom the process, first observed by ernest rutherford in 1904, in which some atoms decayfrom one element into another at a rate predictable enough that you can use them as clocks. ifyou know how long it takes for potassium 40 to become argon 40, and you measure theamounts of each in a sample, you can work out how old a material is. holmes’s contributionwas to measure the decay rate of uranium into lead to calculate the age of rocks, and thus hehoped of the earth. but there were many technical difficulties to overcome. holmes also needed or at leastwould very much have appreciated sophisticated gadgetry of a sort that could make veryfine measurements from tiny samples, and as we have seen it was all he could do to get asimple adding machine. so it was quite an achievement when in 1946 he was able toannounce with some confidence that the earth was at least three billion years old and possiblyrather more. unfortunately, he now met yet another formidable impediment to acceptance: theconservativeness of his fellow scientists. although happy to praise his methodology, many maintained that he had found not the age of the earth but merely the age of the materials fromwhich the earth had been formed. it was just at this time that harrison brown of the university of chicago developed a newmethod for counting lead isotopes in igneous rocks (which is to say those that were createdthrough heating, as opposed to the laying down of sediments). realizing that the work wouldbe exceedingly tedious, he assigned it to young clair patterson as his dissertation project.famously he promised patterson that determining the age of the earth with his new methodwould be “duck soup.” in fact, it would take years. patterson began work on the project in 1948. compared with thomas midgley’s colorfulcontributions to the march of progress, patterson’s discovery of the age of the earth feelsmore than a touch anticlimactic. for seven years, first at the university of chicago and then atthe california institute of technology (where he moved in 1952), he worked in a sterile lab,making very precise measurements of the lead/uranium ratios in carefully selected samples ofold rock. the problem with measuring the age of the earth was that you needed rocks that wereextremely ancient, containing lead  and uranium bearing crystals that were about as old as theplanet itself anything much younger would obviously give you misleadingly youthfuldates but really ancient rocks are only rarely found on earth. in the late 1940s no onealtogether understood why this should be. indeed, and rather extraordinarily, we would bewell into the space age before anyone could plausibly account for where all the earth’s oldrocks went. (the answer was plate tectonics, which we shall of course get to.) patterson,meantime, was left to try to make sense of things with very limited materials. eventually, andingeniously, it occurred to him that he could circumvent the rock shortage by using rocksfrom beyond earth. he turned to meteorites. the assumption he made rather a large one, but correct as it turned out was that manymeteorites are essentially leftover building materials from the early days of the solar system,and thus have managed to preserve a more or less pristine interior chemistry. measure the ageof these wandering rocks and you would have the age also (near enough) of the earth. as always, however, nothing was quite as straightforward as such a breezy descriptionmakes it sound. meteorites are not abundant and meteoritic samples not especially easy to gethold of. moreover, brown’s measurement technique proved finicky in the extreme andneeded much refinement. above all, there was the problem that patterson’s samples werecontinuously and unaccountably contaminated with large doses of atmospheric lead wheneverthey were exposed to air. it was this that eventually led him to create a sterile laboratory theworld’s first, according to at least one account. it took patterson seven years of patient work just to assemble suitable samples for finaltesting. in the spring of 1953 he traveled to the argonne national laboratory in illinois,where he was granted time on a late model mass spectrograph, a machine capable of detectingand measuring the minute quantities of uranium and lead locked up in ancient crystals. whenat last he had his results, patterson was so excited that he drove straight to his boyhood homein iowa and had his mother check him into a hospital because he thought he was having aheart attack. soon afterward, at a meeting in wisconsin, patterson announced a definitive age for theearth of 4,550 million years (plus or minus 70 million years) “a figure that stands unchanged 50 years later,” as mcgrayne admiringly notes. after two hundred years of trying,the earth finally had an age. his main work done, patterson now turned his attention to the nagging question of all thatlead in the atmosphere. he was astounded to find that what little was known about the effectsof lead on humans was almost invariably wrong or misleading and not surprisingly, hediscovered, since for forty years every study of lead’s effects had been funded exclusively bymanufacturers of lead additives. in one such study, a doctor who had no specialized training in chemical pathologyundertook a five year program in which volunteers were asked to breathe in or swallow leadin elevated quantities. then their urine and feces were tested. unfortunately, as the doctorappears not to have known, lead is not excreted as a waste product. rather, it accumulates inthe bones and blood that’s what makes it so dangerous and neither bone nor blood wastested. in consequence, lead was given a clean bill of health. patterson quickly established that we had a lot of lead in the atmosphere still do, in fact,since lead never goes away and that about 90 percent of it appeared to come fromautomobile exhaust pipes, but he couldn’t prove it. what he needed was a way to comparelead levels in the atmosphere now with the levels that existed before 1923, when tetraethyllead was introduced. it occurred to him that ice cores could provide the answer. it was known that snowfall in places like greenland accumulates into discrete annual layers(because seasonal temperature differences produce slight changes in coloration from winter tosummer). by counting back through these layers and measuring the amount of lead in each, hecould work out global lead concentrations at any time for hundreds, or even thousands, ofyears. the notion became the foundation of ice core studies, on which much modernclimatological work is based. what patterson found was that before 1923 there was almost no lead in the atmosphere, andthat since that time its level had climbed steadily and dangerously. he now made it his life’squest to get lead taken out of gasoline. to that end, he became a constant and often vocalcritic of the lead industry and its interests. it would prove to be a hellish campaign. ethyl was a powerful global corporation withmany friends in high places. (among its directors have been supreme court justice lewispowell and gilbert grosvenor of the national geographic society.) patterson suddenly foundresearch funding withdrawn or difficult to acquire. the american petroleum institutecanceled a research contract with him, as did the united states public health service, asupposedly neutral government institution. as patterson increasingly became a liability to his institution, the school trustees wererepeatedly pressed by lead industry officials to shut him up or let him go. according to jamielincoln kitman, writing in the nation in 2000, ethyl executives allegedly offered to endow achair at caltech “if patterson was sent packing.” absurdly, he was excluded from a 1971national research council panel appointed to investigate the dangers of atmospheric leadpoisoning even though he was by now unquestionably the leading expert on atmospheric lead. to his great credit, patterson never wavered or buckled. eventually his efforts led to theintroduction of the clean air act of 1970 and finally to the removal from sale of all leadedgasoline in the united states in 1986. almost immediately lead levels in the blood ofamericans fell by 80 percent. but because lead is forever, those of us alive today have about625 times more lead in our blood than people did a century ago. the amount of lead in theatmosphere also continues to grow, quite legally, by about a hundred thousand metric tons ayear, mostly from mining, smelting, and industrial activities. the united states also bannedlead in indoor paint, “forty four years after most of europe,” as mcgrayne notes.remarkably, considering its startling toxicity, lead solder was not removed from americanfood containers until 1993. as for the ethyl corporation, it’s still going strong, though gm, standard oil, and du pontno longer have stakes in the company. (they sold out to a company called albemarle paper in1962.) according to mcgrayne, as late as february 2001 ethyl continued to contend “thatresearch has failed to show that leaded gasoline poses a threat to human health or theenvironment.” on its website, a history of the company makes no mention of lead or indeedof thomas midgley but simply refers to the original product as containing “a certaincombination of chemicals.” ethyl no longer makes leaded gasoline, although, according to its 2001 company accounts,tetraethyl lead (or tel as it calls it) still accounted for $25.1 million in sales in 2000 (out ofoverall sales of $795 million), up from $24.1 million in 1999, but down from $117 million in1998. in its report the company stated its determination to “maximize the cash generated bytel as its usage continues to phase down around the world.” ethyl markets tel through anagreement with associated octel of england. as for the other scourge left to us by thomas midgley, chlorofluorocarbons, they werebanned in 1974 in the united states, but they are tenacious little devils and any that youloosed into the atmosphere before then (in your deodorants or hair sprays, for instance) willalmost certainly be around and devouring ozone long after you have shuffled off. worse, weare still introducing huge amounts of cfcs into the atmosphere every year. according towayne biddle, 60 million pounds of the stuff, worth $1.5 billion, still finds its way onto themarket every year. so who is making it? we are that is to say, many of our largecorporations are still making it at their plants overseas. it will not be banned in third worldcountries until 2010. clair patterson died in 1995. he didn’t win a nobel prize for his work. geologists neverdo. nor, more puzzlingly, did he gain any fame or even much attention from half a century ofconsistent and increasingly selfless achievement. a good case could be made that he was themost influential geologist of the twentieth century. yet who has ever heard of clair patterson?most geology textbooks don’t mention him. two recent popular books on the history of thedating of earth actually manage to misspell his name. in early 2001, a reviewer of one ofthese books in the journal nature made the additional, rather astounding error of thinkingpatterson was a woman. at all events, thanks to the work of clair patterson by 1953 the earth at last had an ageeveryone could agree on. the only problem now was it was older than the universe thatcontained it. 11 muster mark’s quarksin 1911, a british scientist named c. t. r. wilson was studying cloud formations bytramping regularly to the summit of ben nevis, a famously damp scottish mountain, when itoccurred to him that there must be an easier way to study clouds. back in the cavendish labin cambridge he built an artificial cloud chamber a simple device in which he could cooland moisten the air, creating a reasonable model of a cloud in laboratory conditions. the device worked very well, but had an additional, unexpected benefit. when heaccelerated an alpha particle through the chamber to seed his make believe clouds, it left avisible trail like the contrails of a passing airliner. he had just invented the particle detector.it provided convincing evidence that subatomic particles did indeed exist. eventually two other cavendish scientists invented a more powerful proton beam device,while in california ernest lawrence at berkeley produced his famous and impressivecyclotron, or atom smasher, as such devices were long excitingly known. all of thesecontraptions worked and indeed still work on more or less the same principle, the ideabeing to accelerate a proton or other charged particle to an extremely high speed along a track(sometimes circular, sometimes linear), then bang it into another particle and see what fliesoff. that’s why they were called atom smashers. it wasn’t science at its subtlest, but it wasgenerally effective. as physicists built bigger and more ambitious machines, they began to find or postulateparticles or particle families seemingly without number: muons, pions, hyperons, mesons, k mesons, higgs bosons, intermediate vector bosons, baryons, tachyons. even physicists beganto grow a little uncomfortable. “young man,” enrico fermi replied when a student asked himthe name of a particular particle, “if i could remember the names of these particles, i wouldhave been a botanist.” today accelerators have names that sound like something flash gordon would use inbattle: the super proton synchrotron, the large electron positron collider, the large hadroncollider, the relativistic heavy ion collider. using huge amounts of energy (some operateonly at night so that people in neighboring towns don’t have to witness their lights fadingwhen the apparatus is fired up), they can whip particles into such a state of liveliness that asingle electron can do forty seven thousand laps around a four mile tunnel in a second. fearshave been raised that in their enthusiasm scientists might inadvertently create a black hole oreven something called “strange quarks,” which could, theoretically, interact with othersubatomic particles and propagate uncontrollably. if you are reading this, that hasn’thappened. finding particles takes a certain amount of concentration. they are not just tiny and swiftbut also often tantalizingly evanescent. particles can come into being and be gone again in aslittle as 0.000000000000000000000001 second (10 24). even the most sluggish of unstableparticles hang around for no more than 0.0000001 second (10 7). some particles are almost ludicrously slippery. every second the earth is visited by 10,000trillion trillion tiny, all but massless neutrinos (mostly shot out by the nuclear broilings of thesun), and virtually all of them pass right through the planet and everything that is on it,including you and me, as if it weren’t there. to trap just a few of them, scientists need tanksholding up to 12.5 million gallons of heavy water (that is, water with a relative abundance ofdeuterium in it) in underground chambers (old mines usually) where they can’t be interferedwith by other types of radiation. very occasionally, a passing neutrino will bang into one of the atomic nuclei in the waterand produce a little puff of energy. scientists count the puffs and by such means take us veryslightly closer to understanding the fundamental properties of the universe. in 1998, japaneseobservers reported that neutrinos do have mass, but not a great deal about one ten millionththat of an electron. what it really takes to find particles these days is money and lots of it. there is a curiousinverse relationship in modern physics between the tininess of the thing being sought and thescale of facilities required to do the searching. cern, the european organization for nuclearresearch, is like a little city. straddling the border of france and switzerland, it employsthree thousand people and occupies a site that is measured in square miles. cern boasts astring of magnets that weigh more than the eiffel tower and an underground tunnel oversixteen miles around. breaking up atoms, as james trefil has noted, is easy; you do it each time you switch on afluorescent light. breaking up atomic nuclei, however, requires quite a lot of money and agenerous supply of electricity. getting down to the level of quarks the particles that make upparticles requires still more: trillions of volts of electricity and the budget of a small centralamerican nation. cern’s new large hadron collider, scheduled to begin operations in 2005,will achieve fourteen trillion volts of energy and cost something over $1.5 billion toconstruct.1 but these numbers are as nothing compared with what could have been achieved by, andspent upon, the vast and now unfortunately never to be superconducting supercollider, whichbegan being constructed near waxahachie, texas, in the 1980s, before experiencing asupercollision of its own with the united states congress. the intention of the collider was tolet scientists probe “the ultimate nature of matter,” as it is always put, by re creating as nearlyas possible the conditions in the universe during its first ten thousand billionths of a second.the plan was to fling particles through a tunnel fifty two miles long, achieving a trulystaggering ninety nine trillion volts of energy. it was a grand scheme, but would also havecost $8 billion to build (a figure that eventually rose to $10 billion) and hundreds of millionsof dollars a year to run. in perhaps the finest example in history of pouring money into a hole in the ground,congress spent $2 billion on the project, then canceled it in 1993 after fourteen miles oftunnel had been dug. so texas now boasts the most expensive hole in the universe. the siteis, i am told by my friend jeff guinn of the fort worth star telegram, “essentially a vast,cleared field dotted along the circumference by a series of disappointed small towns.”1 there are practical side effects to all this costly effort. the world wide web is a cern offshoot. it wasinvented by a cern scientist, tim berners lee, in 1989. since the supercollider debacle particle physicists have set their sights a little lower, buteven comparatively modest projects can be quite breathtakingly costly when compared with,well, almost anything. a proposed neutrino observatory at the old homestake mine in lead,south dakota, would cost $500 million to build this in a mine that is already dug beforeyou even look at the annual running costs. there would also be $281 million of “generalconversion costs.” a particle accelerator at fermilab in illinois, meanwhile, cost $260 millionmerely to refit. particle physics, in short, is a hugely expensive enterprise but it is a productive one.today the particle count is well over 150, with a further 100 or so suspected, butunfortunately, in the words of richard feynman, “it is very difficult to understand therelationships of all these particles, and what nature wants them for, or what the connectionsare from one to another.” inevitably each time we manage to unlock a box, we find that thereis another locked box inside. some people think there are particles called tachyons, which cantravel faster than the speed of light. others long to find gravitons the seat of gravity. atwhat point we reach the irreducible bottom is not easy to say. carl sagan in cosmos raised thepossibility that if you traveled downward into an electron, you might find that it contained auniverse of its own, recalling all those science fiction stories of the fifties. “within it,organized into the local equivalent of galaxies and smaller structures, are an immense numberof other, much tinier elementary particles, which are themselves universes at the next leveland so on forever an infinite downward regression, universes within universes, endlessly.and upward as well.” for most of us it is a world that surpasses understanding. to read even an elementary guideto particle physics nowadays you must now find your way through lexical thickets such asthis: “the charged pion and antipion decay respectively into a muon plus antineutrino and anantimuon plus neutrino with an average lifetime of 2.603 x 10 8seconds, the neutral piondecays into two photons with an average lifetime of about 0.8 x 10 16seconds, and the muonand antimuon decay respectively into . . .” and so it runs on and this from a book for thegeneral reader by one of the (normally) most lucid of interpreters, steven weinberg. in the 1960s, in an attempt to bring just a little simplicity to matters, the caltech physicistmurray gell mann invented a new class of particles, essentially, in the words of stevenweinberg, “to restore some economy to the multitude of hadrons” a collective term used byphysicists for protons, neutrons, and other particles governed by the strong nuclear force.gell mann’s theory was that all hadrons were made up of still smaller, even morefundamental particles. his colleague richard feynman wanted to call these new basicparticles partons, as in dolly, but was overruled. instead they became known as quarks. gell mann took the name from a line in finnegans wake: “three quarks for mustermark!” (discriminating physicists rhyme the word with storks, not larks, even though thelatter is almost certainly the pronunciation joyce had in mind.) the fundamental simplicity ofquarks was not long lived. as they became better understood it was necessary to introducesubdivisions. although quarks are much too small to have color or taste or any other physicalcharacteristics we would recognize, they became clumped into six categories up, down,strange, charm, top, and bottom which physicists oddly refer to as their “flavors,” and theseare further divided into the colors red, green, and blue. (one suspects that it was not altogethercoincidental that these terms were first applied in california during the age of psychedelia.) eventually out of all this emerged what is called the standard model, which is essentially asort of parts kit for the subatomic world. the standard model consists of six quarks, sixleptons, five known bosons and a postulated sixth, the higgs boson (named for a scottishscientist, peter higgs), plus three of the four physical forces: the strong and weak nuclearforces and electromagnetism. the arrangement essentially is that among the basic building blocks of matter are quarks;these are held together by particles called gluons; and together quarks and gluons formprotons and neutrons, the stuff of the atom’s nucleus. leptons are the source of electrons andneutrinos. quarks and leptons together are called fermions. bosons (named for the indianphysicist s. n. bose) are particles that produce and carry forces, and include photons andgluons. the higgs boson may or may not actually exist; it was invented simply as a way ofendowing particles with mass. it is all, as you can see, just a little unwieldy, but it is the simplest model that can explainall that happens in the world of particles. most particle physicists feel, as leon ledermanremarked in a 1985 pbs documentary, that the standard model lacks elegance and simplicity.“it is too complicated. it has too many arbitrary parameters,” lederman said. “we don’t reallysee the creator twiddling twenty knobs to set twenty parameters to create the universe as weknow it.” physics is really nothing more than a search for ultimate simplicity, but so far all wehave is a kind of elegant messiness or as lederman put it: “there is a deep feeling that thepicture is not beautiful.” the standard model is not only ungainly but incomplete. for one thing, it has nothing at allto say about gravity. search through the standard model as you will, and you won’t findanything to explain why when you place a hat on a table it doesn’t float up to the ceiling. nor,as we’ve just noted, can it explain mass. in order to give particles any mass at all we have tointroduce the notional higgs boson; whether it actually exists is a matter for twenty first century physics. as feynman cheerfully observed: “so we are stuck with a theory, and we donot know whether it is right or wrong, but we do know that it is a little wrong, or at leastincomplete.” in an attempt to draw everything together, physicists have come up with something calledsuperstring theory. this postulates that all those little things like quarks and leptons that wehad previously thought of as particles are actually “strings” vibrating strands of energy thatoscillate in eleven dimensions, consisting of the three we know already plus time and sevenother dimensions that are, well, unknowable to us. the strings are very tiny tiny enough topass for point particles. by introducing extra dimensions, superstring theory enables physicists to pull togetherquantum laws and gravitational ones into one comparatively tidy package, but it also meansthat anything scientists say about the theory begins to sound worryingly like the sort ofthoughts that would make you edge away if conveyed to you by a stranger on a park bench.here, for example, is the physicist michio kaku explaining the structure of the universe froma superstring perspective: “the heterotic string consists of a closed string that has two types ofvibrations, clockwise and counterclockwise, which are treated differently. the clockwisevibrations live in a ten dimensional space. the counterclockwise live in a twenty six dimensional space, of which sixteen dimensions have been compactified. (we recall that inkaluza’s original five dimensional, the fifth dimension was compactified by being wrappedup into a circle.)” and so it goes, for some 350 pages. string theory has further spawned something called “m theory,” which incorporatessurfaces known as membranes or simply “branes” to the hipper souls of the world ofphysics. i’m afraid this is the stop on the knowledge highway where most of us must get off.here is a sentence from the new york times, explaining this as simply as possible to a generalaudience: “the ekpyrotic process begins far in the indefinite past with a pair of flat emptybranes sitting parallel to each other in a warped five dimensional space. . . . the two branes,which form the walls of the fifth dimension, could have popped out of nothingness as aquantum fluctuation in the even more distant past and then drifted apart.” no arguing withthat. no understanding it either. ekpyrotic, incidentally, comes from the greek word for“conflagration.” matters in physics have now reached such a pitch that, as paul davies noted in nature, it is“almost impossible for the non scientist to discriminate between the legitimately weird andthe outright crackpot.” the question came interestingly to a head in the fall of 2002 when twofrench physicists, twin brothers igor and grickha bogdanov, produced a theory of ambitiousdensity involving such concepts as “imaginary time” and the “kubo schwinger martincondition,” and purporting to describe the nothingness that was the universe before the bigbang a period that was always assumed to be unknowable (since it predated the birth ofphysics and its properties). almost at once the bogdanov paper excited debate among physicists as to whether it wastwaddle, a work of genius, or a hoax. “scientifically, it’s clearly more or less completenonsense,” columbia university physicist peter woit told the new york times, “but thesedays that doesn’t much distinguish it from a lot of the rest of the literature.” karl popper, whom steven weinberg has called “the dean of modern philosophers ofscience,” once suggested that there may not be an ultimate theory for physics that, rather,every explanation may require a further explanation, producing “an infinite chain of more andmore fundamental principles.” a rival possibility is that such knowledge may simply bebeyond us. “so far, fortunately,” writes weinberg in dreams of a final theory, “we do notseem to be coming to the end of our intellectual resources.” almost certainly this is an area that will see further developments of thought, and almostcertainly these thoughts will again be beyond most of us. while physicists in the middle decades of the twentieth century were looking perplexedlyinto the world of the very small, astronomers were finding no less arresting an incompletenessof understanding in the universe at large. when we last met edwin hubble, he had determined that nearly all the galaxies in our fieldof view are flying away from us, and that the speed and distance of this retreat are neatlyproportional: the farther away the galaxy, the faster it is moving. hubble realized that thiscould be expressed with a simple equation, ho = v/d (where ho is the constant, v is therecessional velocity of a flying galaxy, andd its distance away from us). ho has been knownever since as the hubble constant and the whole as hubble’s law. using his formula, hubblecalculated that the universe was about two billion years old, which was a little awkwardbecause even by the late 1920s it was fairly obvious that many things within the universe not least earth itself were probably older than that. refining this figure has been an ongoingpreoccupation of cosmology. almost the only thing constant about the hubble constant has been the amount ofdisagreement over what value to give it. in 1956, astronomers discovered that cepheidvariables were more variable than they had thought; they came in two varieties, not one. thisallowed them to rework their calculations and come up with a new age for the universe offrom 7 to 20 billion years not terribly precise, but at least old enough, at last, to embrace theformation of the earth. in the years that followed there erupted a long running dispute between allan sandage, heirto hubble at mount wilson, and gérard de vaucouleurs, a french born astronomer based atthe university of texas. sandage, after years of careful calculations, arrived at a value for thehubble constant of 50, giving the universe an age of 20 billion years. de vaucouleurs wasequally certain that the hubble constant was 100.2 this would mean that the universe wasonly half the size and age that sandage believed ten billion years. matters took a furtherlurch into uncertainty when in 1994 a team from the carnegie observatories in california,using measures from the hubble space telescope, suggested that the universe could be as littleas eight billion years old an age even they conceded was younger than some of the starswithin the universe. in february 2003, a team from nasa and the goddard space flightcenter in maryland, using a new, far reaching type of satellite called the wilkinsonmicrowave anistropy probe, announced with some confidence that the age of the universe is13.7 billion years, give or take a hundred million years or so. there matters rest, at least forthe moment. the difficulty in making final determinations is that there are often acres of room forinterpretation. imagine standing in a field at night and trying to decide how far away twodistant electric lights are. using fairly straightforward tools of astronomy you can easilyenough determine that the bulbs are of equal brightness and that one is, say, 50 percent moredistant than the other. but what you can’t be certain of is whether the nearer light is, let ussay, a 58 watt bulb that is 122 feet away or a 61 watt light that is 119 feet, 8 inches away. ontop of that you must make allowances for distortions caused by variations in the earth’satmosphere, by intergalactic dust, contaminating light from foreground stars, and many otherfactors. the upshot is that your computations are necessarily based on a series of nestedassumptions, any of which could be a source of contention. there is also the problem thataccess to telescopes is always at a premium and historically measuring red shifts has beennotably costly in telescope time. it could take all night to get a single exposure. inconsequence, astronomers have sometimes been compelled (or willing) to base conclusionson notably scanty evidence. in cosmology, as the journalist geoffrey carr has suggested, wehave “a mountain of theory built on a molehill of evidence.” or as martin rees has put it:“our present satisfaction [with our state of understanding] may reflect the paucity of the datarather than the excellence of the theory.” this uncertainty applies, incidentally, to relatively nearby things as much as to the distantedges of the universe. as donald goldsmith notes, when astronomers say that the galaxy m87is 60 million light years away, what they really mean (“but do not often stress to the generalpublic”) is that it is somewhere between 40 million and 90 million light years away not2 you are of course entitled to wonder what is meant exactly by \"a constant of 50\" or \"a constant of 100.\" theanswer lies in astronomical units of measure. except conversationally, astronomers don't use light years. theyuse a distance called the parsec (a contraction of parallax and second), based on a universal measure called thestellar parallax and equivalent to 3.26 light years. really big measures, like the size of a universe, are measuredin megaparsecs: a million parsecs. the constant is expressed in terms of kilometers per second per megaparsec.thus when astronomers refer to a hubble constant of 50, what they really mean is \"50 kilometers per second permegaparsec.\" for most of us that is of course an utterly meaningless measure, but then with astronomicalmeasures most distances are so huge as to be utterly meaningless. quite the same thing. for the universe at large, matters are naturally magnified. bearing allthat in mind, the best bets these days for the age of the universe seem to be fixed on a range ofabout 12 billion to 13.5 billion years, but we remain a long way from unanimity. one interesting recently suggested theory is that the universe is not nearly as big as wethought, that when we peer into the distance some of the galaxies we see may simply bereflections, ghost images created by rebounded light. the fact is, there is a great deal, even at quite a fundamental level, that we don’t know notleast what the universe is made of. when scientists calculate the amount of matter needed tohold things together, they always come up desperately short. it appears that at least 90 percentof the universe, and perhaps as much as 99 percent, is composed of fritz zwicky’s “darkmatter” stuff that is by its nature invisible to us. it is slightly galling to think that we live ina universe that, for the most part, we can’t even see, but there you are. at least the names forthe two main possible culprits are entertaining: they are said to be either wimps (for weaklyinteracting massive particles, which is to say specks of invisible matter left over from the bigbang) or machos (for massive compact halo objects really just another name for blackholes, brown dwarfs, and other very dim stars). particle physicists have tended to favor the particle explanation of wimps, astrophysiciststhe stellar explanation of machos. for a time machos had the upper hand, but not nearlyenough of them were found, so sentiment swung back toward wimps but with the problemthat no wimp has ever been found. because they are weakly interacting, they are (assumingthey even exist) very hard to detect. cosmic rays would cause too much interference. soscientists must go deep underground. one kilometer underground cosmic bombardmentswould be one millionth what they would be on the surface. but even when all these are addedin, “two thirds of the universe is still missing from the balance sheet,” as one commentatorhas put it. for the moment we might very well call them dunnos (for dark unknownnonreflective nondetectable objects somewhere). recent evidence suggests that not only are the galaxies of the universe racing away fromus, but that they are doing so at a rate that is accelerating. this is counter to all expectations. itappears that the universe may not only be filled with dark matter, but with dark energy.scientists sometimes also call it vacuum energy or, more exotically, quintessence. whatever itis, it seems to be driving an expansion that no one can altogether account for. the theory isthat empty space isn’t so empty at all that there are particles of matter and antimatterpopping into existence and popping out again and that these are pushing the universeoutward at an accelerating rate. improbably enough, the one thing that resolves all this iseinstein’s cosmological constant the little piece of math he dropped into the general theoryof relativity to stop the universe’s presumed expansion, and called “the biggest blunder of mylife.” it now appears that he may have gotten things right after all. the upshot of all this is that we live in a universe whose age we can’t quite compute,surrounded by stars whose distances we don’t altogether know, filled with matter we can’tidentify, operating in conformance with physical laws whose properties we don’t trulyunderstand. and on that rather unsettling note, let’s return to planet earth and consider something thatwe do understand though by now you perhaps won’t be surprised to hear that we don’tunderstand it completely and what we do understand we haven’t understood for long. 12 the earth movesin one of his last professional acts before his death in 1955, albert einstein wrote a shortbut glowing foreword to a book by a geologist named charles hapgood entitled earth’sshifting crust: a key to some basic problems of earth science. hapgood’s book was asteady demolition of the idea that continents were in motion. in a tone that all but invited thereader to join him in a tolerant chuckle, hapgood observed that a few gullible souls hadnoticed “an apparent correspondence in shape between certain continents.” it would appear,he went on, “that south america might be fitted together with africa, and so on. . . . it is evenclaimed that rock formations on opposite sides of the atlantic match.” mr. hapgood briskly dismissed any such notions, noting that the geologists k. e. casterand j. c. mendes had done extensive fieldwork on both sides of the atlantic and hadestablished beyond question that no such similarities existed. goodness knows what outcropsmessrs. caster and mendes had looked at, beacuse in fact many of the rock formations onboth sides of the atlanticare the same not just very similar but the same. this was not an idea that flew with mr. hapgood, or many other geologists of his day. thetheory hapgood alluded to was one first propounded in 1908 by an amateur americangeologist named frank bursley taylor. taylor came from a wealthy family and had both themeans and freedom from academic constraints to pursue unconventional lines of inquiry. hewas one of those struck by the similarity in shape between the facing coastlines of africa andsouth america, and from this observation he developed the idea that the continents had onceslid around. he suggested presciently as it turned out that the crunching together ofcontinents could have thrust up the world’s mountain chains. he failed, however, to producemuch in the way of evidence, and the theory was considered too crackpot to merit seriousattention. in germany, however, taylor’s idea was picked up, and effectively appropriated, by atheorist named alfred wegener, a meteorologist at the university of marburg. wegenerinvestigated the many plant and fossil anomalies that did not fit comfortably into the standardmodel of earth history and realized that very little of it made sense if conventionallyinterpreted. animal fossils repeatedly turned up on opposite sides of oceans that were clearlytoo wide to swim. how, he wondered, did marsupials travel from south america to australia?how did identical snails turn up in scandinavia and new england? and how, come to that,did one account for coal seams and other semi tropical remnants in frigid spots likespitsbergen, four hundred miles north of norway, if they had not somehow migrated therefrom warmer climes? wegener developed the theory that the world’s continents had once come together in asingle landmass he called pangaea, where flora and fauna had been able to mingle, before thecontinents had split apart and floated off to their present positions. all this he put together in abook called die entstehung der kontinente und ozeane, or the origin of continents and oceans, which was published in german in 1912 and despite the outbreak of the firstworld war in the meantime in english three years later. because of the war, wegener’s theory didn’t attract much notice at first, but by 1920, whenhe produced a revised and expanded edition, it quickly became a subject of discussion.everyone agreed that continents moved but up and down, not sideways. the process ofvertical movement, known as isostasy, was a foundation of geological beliefs for generations,though no one had any good theories as to how or why it happened. one idea, which remainedin textbooks well into my own school days, was the baked apple theory propounded by theaustrian eduard suess just before the turn of the century. this suggested that as the moltenearth had cooled, it had become wrinkled in the manner of a baked apple, creating oceanbasins and mountain ranges. never mind that james hutton had shown long before that anysuch static arrangement would eventually result in a featureless spheroid as erosion leveledthe bumps and filled in the divots. there was also the problem, demonstrated by rutherfordand soddy early in the century, that earthly elements hold huge reserves of heat much toomuch to allow for the sort of cooling and shrinking suess suggested. and anyway, if suess’stheory was correct then mountains should be evenly distributed across the face of the earth,which patently they were not, and of more or less the same ages; yet by the early 1900s it wasalready evident that some ranges, like the urals and appalachians, were hundreds of millionsof years older than others, like the alps and rockies. clearly the time was ripe for a newtheory. unfortunately, alfred wegener was not the man that geologists wished to provide it. for a start, his radical notions questioned the foundations of their discipline, seldom aneffective way to generate warmth in an audience. such a challenge would have been painfulenough coming from a geologist, but wegener had no background in geology. he was ameteorologist, for goodness sake. a weatherman a german weatherman. these were notremediable deficiencies. and so geologists took every pain they could think of to dismiss his evidence and belittlehis suggestions. to get around the problems of fossil distributions, they posited ancient “landbridges” wherever they were needed. when an ancient horse named hipparion was found tohave lived in france and florida at the same time, a land bridge was drawn across theatlantic. when it was realized that ancient tapirs had existed simultaneously in southamerica and southeast asia a land bridge was drawn there, too. soon maps of prehistoricseas were almost solid with hypothesized land bridges from north america to europe, frombrazil to africa, from southeast asia to australia, from australia to antarctica. theseconnective tendrils had not only conveniently appeared whenever it was necessary to move aliving organism from one landmass to another, but then obligingly vanished without leaving atrace of their former existence. none of this, of course, was supported by so much as a grainof actual evidence nothing so wrong could be yet it was geological orthodoxy for the nexthalf century. even land bridges couldn’t explain some things. one species of trilobite that was wellknown in europe was also found to have lived on newfoundland but only on one side. noone could persuasively explain how it had managed to cross two thousand miles of hostileocean but then failed to find its way around the corner of a 200 mile wide island. even moreawkwardly anomalous was another species of trilobite found in europe and the pacificnorthwest but nowhere in between, which would have required not so much a land bridge as aflyover. yet as late as 1964 when the encyclopaedia britannica discussed the rival theories, itwas wegener’s that was held to be full of “numerous grave theoretical difficulties.” to be sure, wegener made mistakes. he asserted that greenland is drifting west by about amile a year, which is clearly nonsense. (it’s more like half an inch.) above all, he could offerno convincing explanation for how the landmasses moved about. to believe in his theory youhad to accept that massive continents somehow pushed through solid crust, like a plowthrough soil, without leaving any furrow in their wake. nothing then known could plausiblyexplain what motored these massive movements. it was arthur holmes, the english geologist who did so much to determine the age of theearth, who suggested a possible way. holmes was the first scientist to understand thatradioactive warming could produce convection currents within the earth. in theory thesecould be powerful enough to slide continents around on the surface. in his popular andinfluential textbook principles of physical geology , first published in 1944, holmes laid outa continental drift theory that was in its fundamentals the theory that prevails today. it wasstill a radical proposition for the time and widely criticized, particularly in the united states,where resistance to drift lasted longer than elsewhere. one reviewer there fretted, without anyevident sense of irony, that holmes presented his arguments so clearly and compellingly thatstudents might actually come to believe them. elsewhere, however, the new theory drew steady if cautious support. in 1950, a vote at theannual meeting of the british association for the advancement of science showed that abouthalf of those present now embraced the idea of continental drift. (hapgood soon after citedthis figure as proof of how tragically misled british geologists had become.) curiously,holmes himself sometimes wavered in his conviction. in 1953 he confessed: “i have neversucceeded in freeing myself from a nagging prejudice against continental drift; in mygeological bones, so to speak, i feel the hypothesis is a fantastic one.” continental drift was not entirely without support in the united states. reginald daly ofharvard spoke for it, but he, you may recall, was the man who suggested that the moon hadbeen formed by a cosmic impact, and his ideas tended to be considered interesting, evenworthy, but a touch too exuberant for serious consideration. and so most american academicsstuck to the belief that the continents had occupied their present positions forever and thattheir surface features could be attributed to something other than lateral motions. interestingly, oil company geologists had known for years that if you wanted to find oil youhad to allow for precisely the sort of surface movements that were implied by plate tectonics.but oil geologists didn’t write academic papers; they just found oil. there was one other major problem with earth theories that no one had resolved, or evencome close to resolving. that was the question of where all the sediments went. every yearearth’s rivers carried massive volumes of eroded material 500 million tons of calcium, forinstance to the seas. if you multiplied the rate of deposition by the number of years it hadbeen going on, it produced a disturbing figure: there should be about twelve miles ofsediments on the ocean bottoms or, put another way, the ocean bottoms should by now bewell above the ocean tops. scientists dealt with this paradox in the handiest possible way.they ignored it. but eventually there came a point when they could ignore it no longer. in the second world war, a princeton university mineralogist named harry hess was putin charge of an attack transport ship, the uss cape johnson. aboard this vessel was a fancynew depth sounder called a fathometer, which was designed to facilitate inshore maneuvers during beach landings, but hess realized that it could equally well be used for scientificpurposes and never switched it off, even when far out at sea, even in the heat of battle. whathe found was entirely unexpected. if the ocean floors were ancient, as everyone assumed, theyshould be thickly blanketed with sediments, like the mud on the bottom of a river or lake. buthess’s readings showed that the ocean floor offered anything but the gooey smoothness ofancient silts. it was scored everywhere with canyons, trenches, and crevasses and dotted withvolcanic seamounts that he called guyots after an earlier princeton geologist named arnoldguyot. all this was a puzzle, but hess had a war to take part in, and put such thoughts to theback of his mind. after the war, hess returned to princeton and the preoccupations of teaching, but themysteries of the seafloor continued to occupy a space in his thoughts. meanwhile, throughoutthe 1950s oceanographers were undertaking more and more sophisticated surveys of theocean floors. in so doing, they found an even bigger surprise: the mightiest and mostextensive mountain range on earth was mostly underwater. it traced a continuous pathalong the world’s seabeds, rather like the stitching on a baseball. if you began at iceland, youcould follow it down the center of the atlantic ocean, around the bottom of africa, and acrossthe indian and southern oceans, below australia; there it angled across the pacific as ifmaking for baja california before shooting up the west coast of the united states to alaska.occasionally its higher peaks poked above the water as an island or archipelago the azoresand canaries in the atlantic, hawaii in the pacific, for instance but mostly it was buriedunder thousands of fathoms of salty sea, unknown and unsuspected. when all its brancheswere added together, the network extended to 46,600 miles. a very little of this had been known for some time. people laying ocean floor cables in thenineteenth century had realized that there was some kind of mountainous intrusion in the mid atlantic from the way the cables ran, but the continuous nature and overall scale of the chainwas a stunning surprise. moreover, it contained physical anomalies that couldn’t be explained.down the middle of the mid atlantic ridge was a canyon a rift up to a dozen miles widefor its entire 12,000 mile length. this seemed to suggest that the earth was splitting apart atthe seams, like a nut bursting out of its shell. it was an absurd and unnerving notion, but theevidence couldn’t be denied. then in 1960 core samples showed that the ocean floor was quite young at the mid atlanticridge but grew progressively older as you moved away from it to the east or west. harry hessconsidered the matter and realized that this could mean only one thing: new ocean crust wasbeing formed on either side of the central rift, then being pushed away from it as new crustcame along behind. the atlantic floor was effectively two large conveyor belts, one carryingcrust toward north america, the other carrying crust toward europe. the process becameknown as seafloor spreading. when the crust reached the end of its journey at the boundary with continents, it plungedback into the earth in a process known as subduction. that explained where all the sedimentwent. it was being returned to the bowels of the earth. it also explained why ocean floorseverywhere were so comparatively youthful. none had ever been found to be older than about175 million years, which was a puzzle because continental rocks were often billions of yearsold. now hess could see why. ocean rocks lasted only as long as it took them to travel toshore. it was a beautiful theory that explained a great deal. hess elaborated his ideas in animportant paper, which was almost universally ignored. sometimes the world just isn’t readyfor a good idea. meanwhile, two researchers, working independently, were making some startling findingsby drawing on a curious fact of earth history that had been discovered several decades earlier.in 1906, a french physicist named bernard brunhes had found that the planet’s magnetic fieldreverses itself from time to time, and that the record of these reversals is permanently fixed incertain rocks at the time of their birth. specifically, tiny grains of iron ore within the rockspoint to wherever the magnetic poles happen to be at the time of their formation, then staypointing in that direction as the rocks cool and harden. in effect they “remember” where themagnetic poles were at the time of their creation. for years this was little more than acuriosity, but in the 1950s patrick blackett of the university of london and s. k. runcorn ofthe university of newcastle studied the ancient magnetic patterns frozen in british rocks andwere startled, to say the very least, to find them indicating that at some time in the distant pastbritain had spun on its axis and traveled some distance to the north, as if it had somehowcome loose from its moorings. moreover, they also discovered that if you placed a map ofeurope’s magnetic patterns alongside an american one from the same period, they fit togetheras neatly as two halves of a torn letter. it was uncanny. their findings were ignored too. it finally fell to two men from cambridge university, a geophysicist named drummondmatthews and a graduate student of his named fred vine, to draw all the strands together. in1963, using magnetic studies of the atlantic ocean floor, they demonstrated conclusively thatthe seafloors were spreading in precisely the manner hess had suggested and that thecontinents were in motion too. an unlucky canadian geologist named lawrence morley cameup with the same conclusion at the same time, but couldn’t find anyone to publish his paper.in what has become a famous snub, the editor of the journal of geophysical research toldhim: “such speculations make interesting talk at cocktail parties, but it is not the sort of thingthat ought to be published under serious scientific aegis.” one geologist later described it as“probably the most significant paper in the earth sciences ever to be denied publication.” at all events, mobile crust was an idea whose time had finally come. a symposium ofmany of the most important figures in the field was convened in london under the auspices ofthe royal society in 1964, and suddenly, it seemed, everyone was a convert. the earth, themeeting agreed, was a mosaic of interconnected segments whose various stately jostlingsaccounted for much of the planet’s surface behavior. the name “continental drift” was fairly swiftly discarded when it was realized that thewhole crust was in motion and not just the continents, but it took a while to settle on a namefor the individual segments. at first people called them “crustal blocks” or sometimes “pavingstones.” not until late 1968, with the publication of an article by three americanseismologists in the journal of geophysical research , did the segments receive the name bywhich they have since been known: plates. the same article called the new science platetectonics. old ideas die hard, and not everyone rushed to embrace the exciting new theory. well intothe 1970s, one of the most popular and influential geological textbooks, the earth by thevenerable harold jeffreys, strenuously insisted that plate tectonics was a physicalimpossibility, just as it had in the first edition way back in 1924. it was equally dismissive ofconvection and seafloor spreading. and in basin and range, published in 1980, john mcpheenoted that even then one american geologist in eight still didn’t believe in plate tectonics. today we know that earth’s surface is made up of eight to twelve big plates (depending onhow you define big) and twenty or so smaller ones, and they all move in different directionsand at different speeds. some plates are large and comparatively inactive, others small butenergetic. they bear only an incidental relationship to the landmasses that sit upon them. thenorth american plate, for instance, is much larger than the continent with which it isassociated. it roughly traces the outline of the continent’s western coast (which is why thatarea is so seismically active, because of the bump and crush of the plate boundary), butignores the eastern seaboard altogether and instead extends halfway across the atlantic to themid ocean ridge. iceland is split down the middle, which makes it tectonically half americanand half european. new zealand, meanwhile, is part of the immense indian ocean plate eventhough it is nowhere near the indian ocean. and so it goes for most plates. the connections between modern landmasses and those of the past were found to beinfinitely more complex than anyone had imagined. kazakhstan, it turns out, was onceattached to norway and new england. one corner of staten island, but only a corner, iseuropean. so is part of newfoundland. pick up a pebble from a massachusetts beach, and itsnearest kin will now be in africa. the scottish highlands and much of scandinavia aresubstantially american. some of the shackleton range of antarctica, it is thought, may oncehave belonged to the appalachians of the eastern u.s. rocks, in short, get around. the constant turmoil keeps the plates from fusing into a single immobile plate. assumingthings continue much as at present, the atlantic ocean will expand until eventually it is muchbigger than the pacific. much of california will float off and become a kind of madagascar ofthe pacific. africa will push northward into europe, squeezing the mediterranean out ofexistence and thrusting up a chain of mountains of himalayan majesty running from paris tocalcutta. australia will colonize the islands to its north and connect by some isthmianumbilicus to asia. these are future outcomes, but not future events. the events are happeningnow. as we sit here, continents are adrift, like leaves on a pond. thanks to global positioningsystems we can see that europe and north america are parting at about the speed a fingernailgrows roughly two yards in a human lifetime. if you were prepared to wait long enough,you could ride from los angeles all the way up to san francisco. it is only the brevity oflifetimes that keeps us from appreciating the changes. look at a globe and what you areseeing really is a snapshot of the continents as they have been for just one tenth of 1 percentof the earth’s history. earth is alone among the rocky planets in having tectonics, and why this should be is a bitof a mystery. it is not simply a matter of size or density venus is nearly a twin of earth inthese respects and yet has no tectonic activity. it is thought though it is really nothing morethan a thought that tectonics is an important part of the planet’s organic well being. as thephysicist and writer james trefil has put it, “it would be hard to believe that the continuousmovement of tectonic plates has no effect on the development of life on earth.” he suggeststhat the challenges induced by tectonics changes in climate, for instance were animportant spur to the development of intelligence. others believe the driftings of thecontinents may have produced at least some of the earth’s various extinction events. innovember of 2002, tony dickson of cambridge university in england produced a report,published in the journal science, strongly suggesting that there may well be a relationshipbetween the history of rocks and the history of life. what dickson established was that thechemical composition of the world’s oceans has altered abruptly and vigorously throughoutthe past half billion years and that these changes often correlate with important events inbiological history the huge outburst of tiny organisms that created the chalk cliffs ofengland’s south coast, the sudden fashion for shells among marine organisms during the cambrian period, and so on. no one can say what causes the oceans’ chemistry to change sodramatically from time to time, but the opening and shutting of ocean ridges would be anobvious possible culprit. at all events, plate tectonics not only explained the surface dynamics of the earth how anancient hipparion got from france to florida, for example but also many of its internalactions. earthquakes, the formation of island chains, the carbon cycle, the locations ofmountains, the coming of ice ages, the origins of life itself there was hardly a matter thatwasn’t directly influenced by this remarkable new theory. geologists, as mcphee has noted,found themselves in the giddying position that “the whole earth suddenly made sense.” but only up to a point. the distribution of continents in former times is much less neatlyresolved than most people outside geophysics think. although textbooks give confident looking representations of ancient landmasses with names like laurasia, gondwana, rodinia,and pangaea, these are sometimes based on conclusions that don’t altogether hold up. asgeorge gaylord simpson observes in fossils and the history of life, species of plants andanimals from the ancient world have a habit of appearing inconveniently where they shouldn’tand failing to be where they ought. the outline of gondwana, a once mighty continent connecting australia, africa,antarctica, and south america, was based in large part on the distribution of a genus ofancient tongue fern called glossopteris, which was found in all the right places. however,much later glossopteris was also discovered in parts of the world that had no knownconnection to gondwana. this troubling discrepancy was and continues to be mostlyignored. similarly a triassic reptile called lystrosaurus has been found from antarctica allthe way to asia, supporting the idea of a former connection between those continents, but ithas never turned up in south america or australia, which are believed to have been part ofthe same continent at the same time. there are also many surface features that tectonics can’t explain. take denver. it is, aseveryone knows, a mile high, but that rise is comparatively recent. when dinosaurs roamedthe earth, denver was part of an ocean bottom, many thousands of feet lower. yet the rockson which denver sits are not fractured or deformed in the way they would be if denver hadbeen pushed up by colliding plates, and anyway denver was too far from the plate edges to besusceptible to their actions. it would be as if you pushed against the edge of a rug hoping toraise a ruck at the opposite end. mysteriously and over millions of years, it appears thatdenver has been rising, like baking bread. so, too, has much of southern africa; a portion ofit a thousand miles across has risen nearly a mile in 100 million years without any knownassociated tectonic activity. australia, meanwhile, has been tilting and sinking. over the past100 million years as it has drifted north toward asia, its leading edge has sunk by some sixhundred feet. it appears that indonesia is very slowly drowning, and dragging australia downwith it. nothing in the theories of tectonics can explain any of this. alfred wegener never lived to see his ideas vindicated. on an expedition to greenland in1930, he set out alone, on his fiftieth birthday, to check out a supply drop. he never returned.he was found a few days later, frozen to death on the ice. he was buried on the spot and liesthere yet, but about a yard closer to north america than on the day he died. einstein also failed to live long enough to see that he had backed the wrong horse. in fact,he died at princeton, new jersey, in 1955 before charles hapgood’s rubbishing of continentaldrift theories was even published. the other principal player in the emergence of tectonics theory, harry hess, was also atprinceton at the time, and would spend the rest of his career there. one of his students was abright young fellow named walter alvarez, who would eventually change the world ofscience in a quite different way. as for geology itself, its cataclysms had only just begun, and it was young alvarez whohelped to start the process. part iv dangerous planet the history of any one part of the earth, like the life of a soldier, consists of long periods of boredom and short periods of terror.  british geologist derek v. ager 13 bang!people knew for a long time that there was something odd about the earth beneathmanson, iowa. in 1912, a man drilling a well for the town water supply reported bringing up alot of strangely deformed rock “crystalline clast breccia with a melt matrix” and “overturnedejecta flap,” as it was later described in an official report. the water was odd too. it wasalmost as soft as rainwater. naturally occurring soft water had never been found in iowabefore. though manson’s strange rocks and silken waters were matters of curiosity, forty oneyears would pass before a team from the university of iowa got around to making a trip to thecommunity, then as now a town of about two thousand people in the northwest part of thestate. in 1953, after sinking a series of experimental bores, university geologists agreed thatthe site was indeed anomalous and attributed the deformed rocks to some ancient, unspecifiedvolcanic action. this was in keeping with the wisdom of the day, but it was also about aswrong as a geological conclusion can get. the trauma to manson’s geology had come not from within the earth, but from at least 100million miles beyond. sometime in the very ancient past, when manson stood on the edge of ashallow sea, a rock about a mile and a half across, weighing ten billion tons and traveling atperhaps two hundred times the speed of sound ripped through the atmosphere and punchedinto the earth with a violence and suddenness that we can scarcely imagine. where mansonnow stands became in an instant a hole three miles deep and more than twenty miles across.the limestone that elsewhere gives iowa its hard mineralized water was obliterated andreplaced by the shocked basement rocks that so puzzled the water driller in 1912. the manson impact was the biggest thing that has ever occurred on the mainland unitedstates. of any type. ever. the crater it left behind was so colossal that if you stood on oneedge you would only just be able to see the other side on a good day. it would make the grandcanyon look quaint and trifling. unfortunately for lovers of spectacle, 2.5 million years ofpassing ice sheets filled the manson crater right to the top with rich glacial till, then graded itsmooth, so that today the landscape at manson, and for miles around, is as flat as a tabletop.which is of course why no one has ever heard of the manson crater. at the library in manson they are delighted to show you a collection of newspaper articlesand a box of core samples from a 1991 92 drilling program indeed, they positively bustle toproduce them but you have to ask to see them. nothing permanent is on display, andnowhere in the town is there any historical marker. to most people in manson the biggest thing ever to happen was a tornado that rolled upmain street in 1979, tearing apart the business district. one of the advantages of all thatsurrounding flatness is that you can see danger from a long way off. virtually the whole townturned out at one end of main street and watched for half an hour as the tornado came toward them, hoping it would veer off, then prudently scampered when it did not. four of them, alas,didn’t move quite fast enough and were killed. every june now manson has a weeklong eventcalled crater days, which was dreamed up as a way of helping people forget that unhappyanniversary. it doesn’t really have anything to do with the crater. nobody’s figured out a wayto capitalize on an impact site that isn’t visible. “very occasionally we get people coming in and asking where they should go to see thecrater and we have to tell them that there is nothing to see,” says anna schlapkohl, the town’sfriendly librarian. “then they go away kind of disappointed.” however, most people,including most iowans, have never heard of the manson crater. even for geologists it barelyrates a footnote. but for one brief period in the 1980s, manson was the most geologicallyexciting place on earth. the story begins in the early 1950s when a bright young geologist named eugeneshoemaker paid a visit to meteor crater in arizona. today meteor crater is the most famousimpact site on earth and a popular tourist attraction. in those days, however, it didn’t receivemany visitors and was still often referred to as barringer crater, after a wealthy miningengineer named daniel m. barringer who had staked a claim on it in 1903. barringer believedthat the crater had been formed by a ten million ton meteor, heavily freighted with iron andnickel, and it was his confident expectation that he would make a fortune digging it out.unaware that the meteor and everything in it would have been vaporized on impact, hewasted a fortune, and the next twenty six years, cutting tunnels that yielded nothing. by the standards of today, crater research in the early 1900s was a trifle unsophisticated, tosay the least. the leading early investigator, g. k. gilbert of columbia university, modeledthe effects of impacts by flinging marbles into pans of oatmeal. (for reasons i cannot supply,gilbert conducted these experiments not in a laboratory at columbia but in a hotel room.)somehow from this gilbert concluded that the moon’s craters were indeed formed byimpacts in itself quite a radical notion for the time but that the earth’s were not. mostscientists refused to go even that far. to them, the moon’s craters were evidence of ancientvolcanoes and nothing more. the few craters that remained evident on earth (most had beeneroded away) were generally attributed to other causes or treated as fluky rarities. by the time shoemaker came along, a common view was that meteor crater had beenformed by an underground steam explosion. shoemaker knew nothing about undergroundsteam explosions he couldn’t: they don’t exist but he did know all about blast zones. oneof his first jobs out of college was to study explosion rings at the yucca flats nuclear test sitein nevada. he concluded, as barringer had before him, that there was nothing at meteorcrater to suggest volcanic activity, but that there were huge distributions of other stuff anomalous fine silicas and magnetites principally that suggested an impact from space.intrigued, he began to study the subject in his spare time. working first with his colleague eleanor helin and later with his wife, carolyn, andassociate david levy, shoemaker began a systematic survey of the inner solar system. theyspent one week each month at the palomar observatory in california looking for objects,asteroids primarily, whose trajectories carried them across earth’s orbit. “at the time we started, only slightly more than a dozen of these things had ever beendiscovered in the entire course of astronomical observation,” shoemaker recalled some yearslater in a television interview. “astronomers in the twentieth century essentially abandonedthe solar system,” he added. “their attention was turned to the stars, the galaxies.” what shoemaker and his colleagues found was that there was more risk out there a greatdeal more than anyone had ever imagined. asteroids, as most people know, are rocky objects orbiting in loose formation in a beltbetween mars and jupiter. in illustrations they are always shown as existing in a jumble, butin fact the solar system is quite a roomy place and the average asteroid actually will be abouta million miles from its nearest neighbor. nobody knows even approximately how manyasteroids there are tumbling through space, but the number is thought to be probably not lessthan a billion. they are presumed to be planets that never quite made it, owing to theunsettling gravitational pull of jupiter, which kept and keeps them from coalescing. when asteroids were first detected in the 1800s the very first was discovered on the firstday of the century by a sicilian named giuseppi piazzi they were thought to be planets, andthe first two were named ceres and pallas. it took some inspired deductions by theastronomer william herschel to work out that they were nowhere near planet sized but muchsmaller. he called them asteroids latin for “starlike” which was slightly unfortunate asthey are not like stars at all. sometimes now they are more accurately called planetoids. finding asteroids became a popular activity in the 1800s, and by the end of the centuryabout a thousand were known. the problem was that no one was systematically recordingthem. by the early 1900s, it had often become impossible to know whether an asteroid thatpopped into view was new or simply one that had been noted earlier and then lost track of. bythis time, too, astrophysics had moved on so much that few astronomers wanted to devotetheir lives to anything as mundane as rocky planetoids. only a few astronomers, notablygerard kuiper, the dutch born astronomer for whom the kuiper belt of comets is named,took any interest in the solar system at all. thanks to his work at the mcdonald observatoryin texas, followed later by work done by others at the minor planet center in cincinnati andthe spacewatch project in arizona, a long list of lost asteroids was gradually whittled downuntil by the close of the twentieth century only one known asteroid was unaccounted for anobject called 719 albert. last seen in october 1911, it was finally tracked down in 2000 afterbeing missing for eighty nine years. so from the point of view of asteroid research the twentieth century was essentially just along exercise in bookkeeping. it is really only in the last few years that astronomers havebegun to count and keep an eye on the rest of the asteroid community. as of july 2001,twenty six thousand asteroids had been named and identified half in just the previous twoyears. with up to a billion to identify, the count obviously has barely begun. in a sense it hardly matters. identifying an asteroid doesn’t make it safe. even if everyasteroid in the solar system had a name and known orbit, no one could say what perturbationsmight send any of them hurtling toward us. we can’t forecast rock disturbances on our ownsurface. put them adrift in space and what they might do is beyond guessing. any asteroid outthere that has our name on it is very likely to have no other. think of the earth’s orbit as a kind of freeway on which we are the only vehicle, but whichis crossed regularly by pedestrians who don’t know enough to look before stepping off thecurb. at least 90 percent of these pedestrians are quite unknown to us. we don’t know wherethey live, what sort of hours they keep, how often they come our way. all we know is that atsome point, at uncertain intervals, they trundle across the road down which we are cruising atsixty six thousand miles an hour. as steven ostro of the jet propulsion laboratory has put it,“suppose that there was a button you could push and you could light up all the earth crossing asteroids larger than about ten meters, there would be over 100 million of these objects in thesky.” in short, you would see not a couple of thousand distant twinkling stars, but millionsupon millions upon millions of nearer, randomly moving objects “all of which are capableof colliding with the earth and all of which are moving on slightly different courses throughthe sky at different rates. it would be deeply unnerving.” well, be unnerved because it isthere. we just can’t see it. altogether it is thought though it is really only a guess, based on extrapolating fromcratering rates on the moon that some two thousand asteroids big enough to imperilcivilized existence regularly cross our orbit. but even a small asteroid the size of a house,say could destroy a city. the number of these relative tiddlers in earth crossing orbits isalmost certainly in the hundreds of thousands and possibly in the millions, and they are nearlyimpossible to track. the first one wasn’t spotted until 1991, and that was after it had already gone by. named1991 ba, it was noticed as it sailed past us at a distance of 106,000 miles in cosmic termsthe equivalent of a bullet passing through one’s sleeve without touching the arm. two yearslater, another, somewhat larger asteroid missed us by just 90,000 miles the closest pass yetrecorded. it, too, was not seen until it had passed and would have arrived without warning.according to timothy ferris, writing in the new yorker, such near misses probably happentwo or three times a week and go unnoticed. an object a hundred yards across couldn’t be picked up by any earth based telescope untilit was within just a few days of us, and that is only if a telescope happened to be trained on it,which is unlikely because even now the number of people searching for such objects ismodest. the arresting analogy that is always made is that the number of people in the worldwho are actively searching for asteroids is fewer than the staff of a typical mcdonald’srestaurant. (it is actually somewhat higher now. but not much.) while gene shoemaker was trying to get people galvanized about the potential dangers ofthe inner solar system, another development wholly unrelated on the face of it was quietlyunfolding in italy with the work of a young geologist from the lamont doherty laboratory atcolumbia university. in the early 1970s, walter alvarez was doing fieldwork in a comelydefile known as the bottaccione gorge, near the umbrian hill town of gubbio, when he grewcurious about a thin band of reddish clay that divided two ancient layers of limestone onefrom the cretaceous period, the other from the tertiary. this is a point known to geology asthe kt boundary,1 and it marks the time, sixty five million years ago, when the dinosaurs androughly half the world’s other species of animals abruptly vanish from the fossil record.alvarez wondered what it was about a thin lamina of clay, barely a quarter of an inch thick,that could account for such a dramatic moment in earth’s history. at the time the conventional wisdom about the dinosaur extinction was the same as it hadbeen in charles lyell’s day a century earlier namely that the dinosaurs had died out overmillions of years. but the thinness of the clay layer clearly suggested that in umbria, if1 it is kt rather than ct because c had already been appropriated for cambrian. depending on which sourceyou credit, the k comes either from the greek kreta or german kreide. both conveniently mean “chalk,” whichis also what cretaceous means. nowhere else, something rather more abrupt had happened. unfortunately in the 1970s notests existed for determining how long such a deposit might have taken to accumulate. in the normal course of things, alvarez almost certainly would have had to leave theproblem at that, but luckily he had an impeccable connection to someone outside hisdiscipline who could help his father, luis. luis alvarez was an eminent nuclear physicist;he had won the nobel prize for physics the previous decade. he had always been mildlyscornful of his son’s attachment to rocks, but this problem intrigued him. it occurred to himthat the answer might lie in dust from space. every year the earth accumulates some thirty thousand metric tons of “cosmicspherules” space dust in plainer language which would be quite a lot if you swept it intoone pile, but is infinitesimal when spread across the globe. scattered through this thin dustingare exotic elements not normally much found on earth. among these is the element iridium,which is a thousand times more abundant in space than in the earth’s crust (because, it isthought, most of the iridium on earth sank to the core when the planet was young). alvarez knew that a colleague of his at the lawrence berkeley laboratory in california,frank asaro, had developed a technique for measuring very precisely the chemicalcomposition of clays using a process called neutron activation analysis. this involvedbombarding samples with neutrons in a small nuclear reactor and carefully counting thegamma rays that were emitted; it was extremely finicky work. previously asaro had used thetechnique to analyze pieces of pottery, but alvarez reasoned that if they measured the amountof one of the exotic elements in his son’s soil samples and compared that with its annual rateof deposition, they would know how long it had taken the samples to form. on an octoberafternoon in 1977, luis and walter alvarez dropped in on asaro and asked him if he wouldrun the necessary tests for them. it was really quite a presumptuous request. they were asking asaro to devote months tomaking the most painstaking measurements of geological samples merely to confirm whatseemed entirely self evident to begin with that the thin layer of clay had been formed asquickly as its thinness suggested. certainly no one expected his survey to yield any dramaticbreakthroughs. “well, they were very charming, very persuasive,” asaro recalled in an interview in 2002.“and it seemed an interesting challenge, so i agreed to try. unfortunately, i had a lot of otherwork on, so it was eight months before i could get to it.” he consulted his notes from theperiod. “on june 21, 1978, at 1:45 p.m., we put a sample in the detector. it ran for 224minutes and we could see we were getting interesting results, so we stopped it and had alook.” the results were so unexpected, in fact, that the three scientists at first thought they had tobe wrong. the amount of iridium in the alvarez sample was more than three hundred timesnormal levels far beyond anything they might have predicted. over the following monthsasaro and his colleague helen michel worked up to thirty hours at a stretch (“once youstarted you couldn’t stop,” asaro explained) analyzing samples, always with the same results.tests on other samples from denmark, spain, france, new zealand, antarctica showedthat the iridium deposit was worldwide and greatly elevated everywhere, sometimes by asmuch as five hundred times normal levels. clearly something big and abrupt, and probablycataclysmic, had produced this arresting spike. after much thought, the alvarezes concluded that the most plausible explanation plausible to them, at any rate was that the earth had been struck by an asteroid or comet. the idea that the earth might be subjected to devastating impacts from time to time was notquite as new as it is now sometimes presented. as far back as 1942, a northwesternuniversity astrophysicist named ralph b. baldwin had suggested such a possibility in anarticle in popular astronomy magazine. (he published the article there because no academicpublisher was prepared to run it.) and at least two well known scientists, the astronomerernst öpik and the chemist and nobel laureate harold urey, had also voiced support for thenotion at various times. even among paleontologists it was not unknown. in 1956 a professorat oregon state university, m. w. de laubenfels, writing in the journal of paleontology, hadactually anticipated the alvarez theory by suggesting that the dinosaurs may have been dealt adeath blow by an impact from space, and in 1970 the president of the americanpaleontological society, dewey j. mclaren, proposed at the group’s annual conference thepossibility that an extraterrestrial impact may have been the cause of an earlier event knownas the frasnian extinction. as if to underline just how un novel the idea had become by this time, in 1979 ahollywood studio actually produced a movie called meteor (“it’s five miles wide . . . it’scoming at 30,000 m.p.h. and there’s no place to hide!”) starring henry fonda, nataliewood, karl malden, and a very large rock. so when, in the first week of 1980, at a meeting of the american association for theadvancement of science, the alvarezes announced their belief that the dinosaur extinctionhad not taken place over millions of years as part of some slow inexorable process, butsuddenly in a single explosive event, it shouldn’t have come as a shock. but it did. it was received everywhere, but particularly in the paleontological community,as an outrageous heresy. “well, you have to remember,” asaro recalls, “that we were amateurs in this field. walterwas a geologist specializing in paleomagnetism, luis was a physicist and i was a nuclearchemist. and now here we were telling paleontologists that we had solved a problem that hadeluded them for over a century. it’s not terribly surprising that they didn’t embrace itimmediately.” as luis alvarez joked: “we were caught practicing geology without alicense.” but there was also something much deeper and more fundamentally abhorrent in the impacttheory. the belief that terrestrial processes were gradual had been elemental in natural historysince the time of lyell. by the 1980s, catastrophism had been out of fashion for so long that ithad become literally unthinkable. for most geologists the idea of a devastating impact was, aseugene shoemaker noted, “against their scientific religion.” nor did it help that luis alvarez was openly contemptuous of paleontologists and theircontributions to scientific knowledge. “they’re really not very good scientists. they’re morelike stamp collectors,” he wrote in the new york times in an article that stings yet. opponents of the alvarez theory produced any number of alternative explanations for theiridium deposits for instance, that they were generated by prolonged volcanic eruptions inindia called the deccan traps and above all insisted that there was no proof that thedinosaurs disappeared abruptly from the fossil record at the iridium boundary. one of the most vigorous opponents was charles officer of dartmouth college. he insisted that theiridium had been deposited by volcanic action even while conceding in a newspaper interviewthat he had no actual evidence of it. as late as 1988 more than half of all americanpaleontologists contacted in a survey continued to believe that the extinction of the dinosaurswas in no way related to an asteroid or cometary impact. the one thing that would most obviously support the alvarezes’ theory was the one thingthey didn’t have an impact site. enter eugene shoemaker. shoemaker had an iowaconnection his daughter in law taught at the university of iowa and he was familiar withthe manson crater from his own studies. thanks to him, all eyes now turned to iowa. geology is a profession that varies from place to place. in iowa, a state that is flat andstratigraphically uneventful, it tends to be comparatively serene. there are no alpine peaks orgrinding glaciers, no great deposits of oil or precious metals, not a hint of a pyroclastic flow.if you are a geologist employed by the state of iowa, a big part of the work you do is toevaluate manure management plans, which all the state’s “animal confinement operators” hog farmers to the rest of us are required to file periodically. there are fifteen million hogsin iowa, so a lot of manure to manage. i’m not mocking this at all it’s vital and enlightenedwork; it keeps iowa’s water clean but with the best will in the world it’s not exactly dodginglava bombs on mount pinatubo or scrabbling over crevasses on the greenland ice sheet insearch of ancient life bearing quartzes. so we may well imagine the flutter of excitement thatswept through the iowa department of natural resources when in the mid 1980s the world’sgeological attention focused on manson and its crater. trowbridge hall in iowa city is a turn of the century pile of red brick that houses theuniversity of iowa’s earth sciences department and way up in a kind of garret thegeologists of the iowa department of natural resources. no one now can remember quitewhen, still less why, the state geologists were placed in an academic facility, but you get theimpression that the space was conceded grudgingly, for the offices are cramped and low ceilinged and not very accessible. when being shown the way, you half expect to be taken outonto a roof ledge and helped in through a window. ray anderson and brian witzke spend their working lives up here amid disordered heapsof papers, journals, furled charts, and hefty specimen stones. (geologists are never at a lossfor paperweights.) it’s the kind of space where if you want to find anything an extra chair, acoffee cup, a ringing telephone you have to move stacks of documents around. “suddenly we were at the center of things,” anderson told me, gleaming at the memory ofit, when i met him and witzke in their offices on a dismal, rainy morning in june. “it was awonderful time.” i asked them about gene shoemaker, a man who seems to have been universally revered.“he was just a great guy,” witzke replied without hesitation. “if it hadn’t been for him, thewhole thing would never have gotten off the ground. even with his support, it took two yearsto get it up and running. drilling’s an expensive business about thirty five dollars a footback then, more now, and we needed to go down three thousand feet.” “sometimes more than that,” anderson added. “sometimes more than that,” witzke agreed. “and at several locations. so you’re talking alot of money. certainly more than our budget would allow.” so a collaboration was formed between the iowa geological survey and the u.s.geological survey. “at least we thought it was a collaboration,” said anderson, producing a small painedsmile. “it was a real learning curve for us,” witzke went on. “there was actually quite a lot of badscience going on throughout the period people rushing in with results that didn’t alwaysstand up to scrutiny.” one of those moments came at the annual meeting of the americangeophysical union in 1985, when glenn izett and c. l. pillmore of the u.s. geologicalsurvey announced that the manson crater was of the right age to have been involved with thedinosaurs’ extinction. the declaration attracted a good deal of press attention but wasunfortunately premature. a more careful examination of the data revealed that manson wasnot only too small, but also nine million years too early. the first anderson or witzke learned of this setback to their careers was when they arrivedat a conference in south dakota and found people coming up to them with sympathetic looksand saying: “we hear you lost your crater.” it was the first they knew that izett and the otherusgs scientists had just announced refined figures revealing that manson couldn’t after allhave been the extinction crater. “it was pretty stunning,” recalls anderson. “i mean, we had this thing that was reallyimportant and then suddenly we didn’t have it anymore. but even worse was the realizationthat the people we thought we’d been collaborating with hadn’t bothered to share with us theirnew findings.” “why not?” he shrugged. “who knows? anyway, it was a pretty good insight into how unattractivescience can get when you’re playing at a certain level.” the search moved elsewhere. by chance in 1990 one of the searchers, alan hildebrand ofthe university of arizona, met a reporter from the houston chronicle who happened to knowabout a large, unexplained ring formation, 120 miles wide and 30 miles deep, under mexico’syucatán peninsula at chicxulub, near the city of progreso, about 600 miles due south of neworleans. the formation had been found by pemex, the mexican oil company, in 1952 theyear, coincidentally, that gene shoemaker first visited meteor crater in arizona but thecompany’s geologists had concluded that it was volcanic, in line with the thinking of the day.hildebrand traveled to the site and decided fairly swiftly that they had their crater. by early1991 it had been established to nearly everyone’s satisfaction that chicxulub was the impactsite. still, many people didn’t quite grasp what an impact could do. as stephen jay gouldrecalled in one of his essays: “i remember harboring some strong initial doubts about theefficacy of such an event . . . [w]hy should an object only six miles across wreak such havocupon a planet with a diameter of eight thousand miles?” conveniently a natural test of the theory arose when the shoemakers and levy discoveredcomet shoemaker levy 9, which they soon realized was headed for jupiter. for the first time,humans would be able to witness a cosmic collision and witness it very well thanks to thenew hubble space telescope. most astronomers, according to curtis peebles, expected little,particularly as the comet was not a coherent sphere but a string of twenty one fragments. “mysense,” wrote one, “is that jupiter will swallow these comets up without so much as a burp.”one week before the impact, nature ran an article, “the big fizzle is coming,” predictingthat the impact would constitute nothing more than a meteor shower. the impacts began on july 16, 1994, went on for a week and were bigger by far thananyone with the possible exception of gene shoemaker expected. one fragment, knownas nucleus g, struck with the force of about six million megatons seventy five times morethan all the nuclear weaponry in existence. nucleus g was only about the size of a smallmountain, but it created wounds in the jovian surface the size of earth. it was the final blowfor critics of the alvarez theory. luis alvarez never knew of the discovery of the chicxulub crater or of the shoemaker levy comet, as he died in 1988. shoemaker also died early. on the third anniversary of theshoemaker levy impact, he and his wife were in the australian outback, where they wentevery year to search for impact sites. on a dirt track in the tanami desert normally one ofthe emptiest places on earth they came over a slight rise just as another vehicle wasapproaching. shoemaker was killed instantly, his wife injured. part of his ashes were sent tothe moon aboard the lunar prospector spacecraft. the rest were scattered around meteorcrater. anderson and witzke no longer had the crater that killed the dinosaurs, “but we still hadthe largest and most perfectly preserved impact crater in the mainland united states,”anderson said. (a little verbal dexterity is required to keep manson’s superlative status. othercraters are larger notably, chesapeake bay, which was recognized as an impact site in1994 but they are either offshore or deformed.) “chicxulub is buried under two to threekilometers of limestone and mostly offshore, which makes it difficult to study,” andersonwent on, “while manson is really quite accessible. it’s because it is buried that it is actuallycomparatively pristine.” i asked them how much warning we would receive if a similar hunk of rock was comingtoward us today. “oh, probably none,” said anderson breezily. “it wouldn’t be visible to the naked eye untilit warmed up, and that wouldn’t happen until it hit the atmosphere, which would be about onesecond before it hit the earth. you’re talking about something moving many tens of timesfaster than the fastest bullet. unless it had been seen by someone with a telescope, and that’sby no means a certainty, it would take us completely by surprise.” how hard an impactor hits depends on a lot of variables angle of entry, velocity andtrajectory, whether the collision is head on or from the side, and the mass and density of theimpacting object, among much else none of which we can know so many millions of yearsafter the fact. but what scientists can do and anderson and witzke have done is measurethe impact site and calculate the amount of energy released. from that they can work out plausible scenarios of what it must have been like or, more chillingly, would be like if ithappened now. an asteroid or comet traveling at cosmic velocities would enter the earth’s atmosphere atsuch a speed that the air beneath it couldn’t get out of the way and would be compressed, as ina bicycle pump. as anyone who has used such a pump knows, compressed air grows swiftlyhot, and the temperature below it would rise to some 60,000 kelvin, or ten times the surfacetemperature of the sun. in this instant of its arrival in our atmosphere, everything in themeteor’s path people, houses, factories, cars would crinkle and vanish like cellophane in aflame. one second after entering the atmosphere, the meteorite would slam into the earth’ssurface, where the people of manson had a moment before been going about their business.the meteorite itself would vaporize instantly, but the blast would blow out a thousand cubickilometers of rock, earth, and superheated gases. every living thing within 150 miles thathadn’t been killed by the heat of entry would now be killed by the blast. radiating outward atalmost the speed of light would be the initial shock wave, sweeping everything before it. for those outside the zone of immediate devastation, the first inkling of catastrophe wouldbe a flash of blinding light the brightest ever seen by human eyes followed an instant to aminute or two later by an apocalyptic sight of unimaginable grandeur: a roiling wall ofdarkness reaching high into the heavens, filling an entire field of view and traveling atthousands of miles an hour. its approach would be eerily silent since it would be moving farbeyond the speed of sound. anyone in a tall building in omaha or des moines, say, whochanced to look in the right direction would see a bewildering veil of turmoil followed byinstantaneous oblivion. within minutes, over an area stretching from denver to detroit and encompassing what hadonce been chicago, st. louis, kansas city, the twin cities the whole of the midwest, inshort nearly every standing thing would be flattened or on fire, and nearly every living thingwould be dead. people up to a thousand miles away would be knocked off their feet and slicedor clobbered by a blizzard of flying projectiles. beyond a thousand miles the devastation fromthe blast would gradually diminish. but that’s just the initial shockwave. no one can do more than guess what the associateddamage would be, other than that it would be brisk and global. the impact would almostcertainly set off a chain of devastating earthquakes. volcanoes across the globe would beginto rumble and spew. tsunamis would rise up and head devastatingly for distant shores. withinan hour, a cloud of blackness would cover the planet, and burning rock and other debriswould be pelting down everywhere, setting much of the planet ablaze. it has been estimatedthat at least a billion and a half people would be dead by the end of the first day. the massivedisturbances to the ionosphere would knock out communications systems everywhere, sosurvivors would have no idea what was happening elsewhere or where to turn. it would hardlymatter. as one commentator has put it, fleeing would mean “selecting a slow death over aquick one. the death toll would be very little affected by any plausible relocation effort, sinceearth’s ability to support life would be universally diminished.” the amount of soot and floating ash from the impact and following fires would blot out thesun, certainly for months, possibly for years, disrupting growing cycles. in 2001 researchers atthe california institute of technology analyzed helium isotopes from sediments left from thelater kt impact and concluded that it affected earth’s climate for about ten thousand years. this was actually used as evidence to support the notion that the extinction of dinosaurs wasswift and emphatic and so it was in geological terms. we can only guess how well, orwhether, humanity would cope with such an event. and in all likelihood, remember, this would come without warning, out of a clear sky. but let’s assume we did see the object coming. what would we do? everyone assumes wewould send up a nuclear warhead and blast it to smithereens. the idea has some problems,however. first, as john s. lewis notes, our missiles are not designed for space work. theyhaven’t the oomph to escape earth’s gravity and, even if they did, there are no mechanisms toguide them across tens of millions of miles of space. still less could we send up a shipload ofspace cowboys to do the job for us, as in the movie armageddon; we no longer possess arocket powerful enough to send humans even as far as the moon. the last rocket that could,saturn 5, was retired years ago and has never been replaced. nor could we quickly build anew one because, amazingly, the plans for saturn launchers were destroyed as part of anasa housecleaning exercise. even if we did manage somehow to get a warhead to the asteroid and blasted it to pieces,the chances are that we would simply turn it into a string of rocks that would slam into us oneafter the other in the manner of comet shoemaker levy on jupiter but with the differencethat now the rocks would be intensely radioactive. tom gehrels, an asteroid hunter at theuniversity of arizona, thinks that even a year’s warning would probably be insufficient totake appropriate action. the greater likelihood, however, is that we wouldn’t see any object even a comet until it was about six months away, which would be much too late.shoemaker levy 9 had been orbiting jupiter in a fairly conspicuous manner since 1929, but ittook over half a century before anyone noticed. interestingly, because these things are so difficult to compute and must incorporate such asignificant margin of error, even if we knew an object was heading our way we wouldn’tknow until nearly the end the last couple of weeks anyway whether collision was certain.for most of the time of the object’s approach we would exist in a kind of cone of uncertainty.it would certainly be the most interesting few months in the history of the world. and imaginethe party if it passed safely. “so how often does something like the manson impact happen?” i asked anderson andwitzke before leaving. “oh, about once every million years on average,” said witzke. “and remember,” added anderson, “this was a relatively minor event. do you know howmany extinctions were associated with the manson impact?” “no idea,” i replied. “none,” he said, with a strange air of satisfaction. “not one.” of course, witzke and anderson added hastily and more or less in unison, there wouldhave been terrible devastation across much of the earth, as just described, and completeannihilation for hundreds of miles around ground zero. but life is hardy, and when the smokecleared there were enough lucky survivors from every species that none permanentlyperished. the good news, it appears, is that it takes an awful lot to extinguish a species. the badnews is that the good news can never be counted on. worse still, it isn’t actually necessary tolook to space for petrifying danger. as we are about to see, earth can provide plenty of dangerof its own. 14 the fire belowin the summer of 1971, a young geologist named mike voorhies was scouting around onsome grassy farmland in eastern nebraska, not far from the little town of orchard, where hehad grown up. passing through a steep sided gully, he spotted a curious glint in the brushabove and clambered up to have a look. what he had seen was the perfectly preserved skull ofa young rhinoceros, which had been washed out by recent heavy rains. a few yards beyond, it turned out, was one of the most extraordinary fossil beds everdiscovered in north america, a dried up water hole that had served as a mass grave for scoresof animals rhinoceroses, zebra like horses, saber toothed deer, camels, turtles. all had diedfrom some mysterious cataclysm just under twelve million years ago in the time known togeology as the miocene. in those days nebraska stood on a vast, hot plain very like theserengeti of africa today. the animals had been found buried under volcanic ash up to tenfeet deep. the puzzle of it was that there were not, and never had been, any volcanoes innebraska. today, the site of voorhies’s discovery is called ashfall fossil beds state park, and it has astylish new visitors’ center and museum, with thoughtful displays on the geology of nebraskaand the history of the fossil beds. the center incorporates a lab with a glass wall throughwhich visitors can watch paleontologists cleaning bones. working alone in the lab on themorning i passed through was a cheerfully grizzled looking fellow in a blue work shirt whomi recognized as mike voorhies from a bbc television documentary in which he featured.they don’t get a huge number of visitors to ashfall fossil beds state park it’s slightly inthe middle of nowhere and voorhies seemed pleased to show me around. he took me to thespot atop a twenty foot ravine where he had made his find. “it was a dumb place to look for bones,” he said happily. “but i wasn’t looking for bones. iwas thinking of making a geological map of eastern nebraska at the time, and really just kindof poking around. if i hadn’t gone up this ravine or the rains hadn’t just washed out that skull,i’d have walked on by and this would never have been found.” he indicated a roofedenclosure nearby, which had become the main excavation site. some two hundred animalshad been found lying together in a jumble. i asked him in what way it was a dumb place to hunt for bones. “well, if you’re looking forbones, you really need exposed rock. that’s why most paleontology is done in hot, dry places.it’s not that there are more bones there. it’s just that you have some chance of spotting them.in a setting like this” he made a sweeping gesture across the vast and unvarying prairie “you wouldn’t know where to begin. there could be really magnificent stuff out there, butthere’s no surface clues to show you where to start looking.” at first they thought the animals were buried alive, and voorhies stated as much in anational geographic article in 1981. “the article called the site a ‘pompeii of prehistoric animals,’ ” he told me, “which was unfortunate because just afterward we realized that theanimals hadn’t died suddenly at all. they were all suffering from something calledhypertrophic pulmonary osteodystrophy, which is what you would get if you were breathing alot of abrasive ash and they must have been breathing a lot of it because the ash was feetthick for hundreds of miles.” he picked up a chunk of grayish, claylike dirt and crumbled itinto my hand. it was powdery but slightly gritty. “nasty stuff to have to breathe,” he went on,“because it’s very fine but also quite sharp. so anyway they came here to this watering hole,presumably seeking relief, and died in some misery. the ash would have ruined everything. itwould have buried all the grass and coated every leaf and turned the water into an undrinkablegray sludge. it couldn’t have been very agreeable at all.” the bbc documentary had suggested that the existence of so much ash in nebraska was asurprise. in fact, nebraska’s huge ash deposits had been known about for a long time. foralmost a century they had been mined to make household cleaning powders like comet andajax. but curiously no one had ever thought to wonder where all the ash came from. “i’m a little embarrassed to tell you,” voorhies said, smiling briefly, “that the first i thoughtabout it was when an editor at the national geographic asked me the source of all the ash andi had to confess that i didn’t know. nobody knew.” voorhies sent samples to colleagues all over the western united states asking if there wasanything about it that they recognized. several months later a geologist named billbonnichsen from the idaho geological survey got in touch and told him that the ash matcheda volcanic deposit from a place called bruneau jarbidge in southwest idaho. the event thatkilled the plains animals of nebraska was a volcanic explosion on a scale previouslyunimagined but big enough to leave an ash layer ten feet deep almost a thousand miles awayin eastern nebraska. it turned out that under the western united states there was a hugecauldron of magma, a colossal volcanic hot spot, which erupted cataclysmically every600,000 years or so. the last such eruption was just over 600,000 years ago. the hot spot isstill there. these days we call it yellowstone national park. we know amazingly little about what happens beneath our feet. it is fairly remarkable tothink that ford has been building cars and baseball has been playing world series for longerthan we have known that the earth has a core. and of course the idea that the continents moveabout on the surface like lily pads has been common wisdom for much less than a generation.“strange as it may seem,” wrote richard feynman, “we understand the distribution of matterin the interior of the sun far better than we understand the interior of the earth.” the distance from the surface of earth to the center is 3,959 miles, which isn’t so very far.it has been calculated that if you sunk a well to the center and dropped a brick into it, it wouldtake only forty five minutes for it to hit the bottom (though at that point it would beweightless since all the earth’s gravity would be above and around it rather than beneath it).our own attempts to penetrate toward the middle have been modest indeed. one or two southafrican gold mines reach to a depth of two miles, but most mines on earth go no more thanabout a quarter of a mile beneath the surface. if the planet were an apple, we wouldn’t yethave broken through the skin. indeed, we haven’t even come close. until slightly under a century ago, what the best informed scientific minds knew aboutearth’s interior was not much more than what a coal miner knew namely, that you could dig down through soil for a distance and then you’d hit rock and that was about it. then in 1906,an irish geologist named r. d. oldham, while examining some seismograph readings from anearthquake in guatemala, noticed that certain shock waves had penetrated to a point deepwithin the earth and then bounced off at an angle, as if they had encountered some kind ofbarrier. from this he deduced that the earth has a core. three years later a croatianseismologist named andrija mohoroviči´c was studying graphs from an earthquake in zagrebwhen he noticed a similar odd deflection, but at a shallower level. he had discovered theboundary between the crust and the layer immediately below, the mantle; this zone has beenknown ever since as the mohoroviči´c discontinuity, or moho for short. we were beginning to get a vague idea of the earth’s layered interior though it really wasonly vague. not until 1936 did a danish scientist named inge lehmann, studyingseismographs of earthquakes in new zealand, discover that there were two cores an innerone that we now believe to be solid and an outer one (the one that oldham had detected) thatis thought to be liquid and the seat of magnetism. at just about the time that lehmann was refining our basic understanding of the earth’sinterior by studying the seismic waves of earthquakes, two geologists at caltech in californiawere devising a way to make comparisons between one earthquake and the next. they werecharles richter and beno gutenberg, though for reasons that have nothing to do with fairnessthe scale became known almost at once as richter’s alone. (it has nothing to do with richtereither. a modest fellow, he never referred to the scale by his own name, but always called it“the magnitude scale.”) the richter scale has always been widely misunderstood by nonscientists, though perhapsa little less so now than in its early days when visitors to richter’s office often asked to seehis celebrated scale, thinking it was some kind of machine. the scale is of course more anidea than an object, an arbitrary measure of the earth’s tremblings based on surfacemeasurements. it rises exponentially, so that a 7.3 quake is fifty times more powerful than a6.3 earthquake and 2,500 times more powerful than a 5.3 earthquake. at least theoretically, there is no upper limit for an earthquake nor, come to that, a lowerlimit. the scale is a simple measure of force, but says nothing about damage. a magnitude 7quake happening deep in the mantle say, four hundred miles down might cause no surfacedamage at all, while a significantly smaller one happening just four miles under the surfacecould wreak widespread devastation. much, too, depends on the nature of the subsoil, thequake’s duration, the frequency and severity of aftershocks, and the physical setting of theaffected area. all this means that the most fearsome quakes are not necessarily the mostforceful, though force obviously counts for a lot. the largest earthquake since the scale’s invention was (depending on which source youcredit) either one centered on prince william sound in alaska in march 1964, whichmeasured 9.2 on the richter scale, or one in the pacific ocean off the coast of chile in 1960,which was initially logged at 8.6 magnitude but later revised upward by some authorities(including the united states geological survey) to a truly grand scale 9.5. as you will gatherfrom this, measuring earthquakes is not always an exact science, particularly wheninterpreting readings from remote locations. at all events, both quakes were whopping. the1960 quake not only caused widespread damage across coastal south america, but also set offa giant tsunami that rolled six thousand miles across the pacific and slapped away much ofdowntown hilo, hawaii, destroying five hundred buildings and killing sixty people. similarwave surges claimed yet more victims as far away as japan and the philippines. for pure, focused, devastation, however, probably the most intense earthquake in recordedhistory was one that struck and essentially shook to pieces lisbon, portugal, on all saintsday (november 1), 1755. just before ten in the morning, the city was hit by a suddensideways lurch now estimated at magnitude 9.0 and shaken ferociously for seven full minutes.the convulsive force was so great that the water rushed out of the city’s harbor and returnedin a wave fifty feet high, adding to the destruction. when at last the motion ceased, survivorsenjoyed just three minutes of calm before a second shock came, only slightly less severe thanthe first. a third and final shock followed two hours later. at the end of it all, sixty thousandpeople were dead and virtually every building for miles reduced to rubble. the san franciscoearthquake of 1906, for comparison, measured an estimated 7.8 on the richter scale andlasted less than thirty seconds. earthquakes are fairly common. every day on average somewhere in the world there aretwo of magnitude 2.0 or greater that’s enough to give anyone nearby a pretty good jolt.although they tend to cluster in certain places notably around the rim of the pacific theycan occur almost anywhere. in the united states, only florida, eastern texas, and the uppermidwest seem so far to be almost entirely immune. new england has had two quakes ofmagnitude 6.0 or greater in the last two hundred years. in april 2002, the region experienceda 5.1 magnitude shaking in a quake near lake champlain on the new york vermont border,causing extensive local damage and (i can attest) knocking pictures from walls and childrenfrom beds as far away as new hampshire. the most common types of earthquakes are those where two plates meet, as in californiaalong the san andreas fault. as the plates push against each other, pressures build up untilone or the other gives way. in general, the longer the interval between quakes, the greater thepent up pressure and thus the greater the scope for a really big jolt. this is a particular worryfor tokyo, which bill mcguire, a hazards specialist at university college london, describesas “the city waiting to die” (not a motto you will find on many tourism leaflets). tokyo standson the boundary of three tectonic plates in a country already well known for its seismicinstability. in 1995, as you will remember, the city of kobe, three hundred miles to the west,was struck by a magnitude 7.2 quake, which killed 6,394 people. the damage was estimatedat $99 billion. but that was as nothing well, as comparatively little compared with whatmay await tokyo. tokyo has already suffered one of the most devastating earthquakes in modern times. onseptember 1, 1923, just before noon, the city was hit by what is known as the great kantoquake an event more than ten times more powerful than kobe’s earthquake. two hundredthousand people were killed. since that time, tokyo has been eerily quiet, so the strainbeneath the surface has been building for eighty years. eventually it is bound to snap. in 1923,tokyo had a population of about three million. today it is approaching thirty million. nobodycares to guess how many people might die, but the potential economic cost has been put ashigh as $7 trillion. even more unnerving, because they are less well understood and capable of occurringanywhere at any time, are the rarer type of shakings known as intraplate quakes. thesehappen away from plate boundaries, which makes them wholly unpredictable. and becausethey come from a much greater depth, they tend to propagate over much wider areas. themost notorious such quakes ever to hit the united states were a series of three in newmadrid, missouri, in the winter of 1811 12. the adventure started just after midnight on december 16 when people were awakened first by the noise of panicking farm animals (therestiveness of animals before quakes is not an old wives’ tale, but is in fact well established,though not at all understood) and then by an almighty rupturing noise from deep within theearth. emerging from their houses, locals found the land rolling in waves up to three feet highand opening up in fissures several feet deep. a strong smell of sulfur filled the air. theshaking lasted for four minutes with the usual devastating effects to property. among thewitnesses was the artist john james audubon, who happened to be in the area. the quakeradiated outward with such force that it knocked down chimneys in cincinnati four hundredmiles away and, according to at least one account, “wrecked boats in east coast harbors and .. . even collapsed scaffolding erected around the capitol building in washington, d.c.” onjanuary 23 and february 4 further quakes of similar magnitude followed. new madrid hasbeen silent ever since but not surprisingly, since such episodes have never been known tohappen in the same place twice. as far as we know, they are as random as lightning. the nextone could be under chicago or paris or kinshasa. no one can even begin to guess. and whatcauses these massive intraplate rupturings? something deep within the earth. more than thatwe don’t know. by the 1960s scientists had grown sufficiently frustrated by how little they understood ofthe earth’s interior that they decided to try to do something about it. specifically, they got theidea to drill through the ocean floor (the continental crust was too thick) to the mohodiscontinuity and to extract a piece of the earth’s mantle for examination at leisure. thethinking was that if they could understand the nature of the rocks inside the earth, they mightbegin to understand how they interacted, and thus possibly be able to predict earthquakes andother unwelcome events. the project became known, all but inevitably, as the mohole and it was pretty welldisastrous. the hope was to lower a drill through 14,000 feet of pacific ocean water off thecoast of mexico and drill some 17,000 feet through relatively thin crustal rock. drilling froma ship in open waters is, in the words of one oceanographer, “like trying to drill a hole in thesidewalks of new york from atop the empire state building using a strand of spaghetti.”every attempt ended in failure. the deepest they penetrated was only about 600 feet. themohole became known as the no hole. in 1966, exasperated with ever rising costs and noresults, congress killed the project. four years later, soviet scientists decided to try their luck on dry land. they chose a spot onrussia’s kola peninsula, near the finnish border, and set to work with the hope of drilling toa depth of fifteen kilometers. the work proved harder than expected, but the soviets werecommendably persistent. when at last they gave up, nineteen years later, they had drilled to adepth of 12,262 meters, or about 7.6 miles. bearing in mind that the crust of the earthrepresents only about 0.3 percent of the planet’s volume and that the kola hole had not cuteven one third of the way through the crust, we can hardly claim to have conquered theinterior. interestingly, even though the hole was modest, nearly everything about it was surprising.seismic wave studies had led the scientists to predict, and pretty confidently, that they wouldencounter sedimentary rock to a depth of 4,700 meters, followed by granite for the next 2,300meters and basalt from there on down. in the event, the sedimentary layer was 50 percentdeeper than expected and the basaltic layer was never found at all. moreover, the world downthere was far warmer than anyone had expected, with a temperature at 10,000 meters of 180 degrees centigrade, nearly twice the forecasted level. most surprising of all was that the rockat that depth was saturated with water something that had not been thought possible. because we can’t see into the earth, we have to use other techniques, which mostly involvereading waves as they travel through the interior. we also know a little bit about the mantlefrom what are known as kimberlite pipes, where diamonds are formed. what happens is thatdeep in the earth there is an explosion that fires, in effect, a cannonball of magma to thesurface at supersonic speeds. it is a totally random event. a kimberlite pipe could explode inyour backyard as you read this. because they come up from such depths up to 120 milesdown kimberlite pipes bring up all kinds of things not normally found on or near thesurface: a rock called peridotite, crystals of olivine, and just occasionally, in about one pipein a hundred diamonds. lots of carbon comes up with kimberlite ejecta, but most isvaporized or turns to graphite. only occasionally does a hunk of it shoot up at just the rightspeed and cool down with the necessary swiftness to become a diamond. it was such a pipethat made johannesburg the most productive diamond mining city in the world, but there maybe others even bigger that we don’t know about. geologists know that somewhere in thevicinity of northeastern indiana there is evidence of a pipe or group of pipes that may be trulycolossal. diamonds up to twenty carats or more have been found at scattered sites throughoutthe region. but no one has ever found the source. as john mcphee notes, it may be buriedunder glacially deposited soil, like the manson crater in iowa, or under the great lakes. so how much do we know about what’s inside the earth? very little. scientists aregenerally agreed that the world beneath us is composed of four layers rocky outer crust, amantle of hot, viscous rock, a liquid outer core, and a solid inner core.1 we know that thesurface is dominated by silicates, which are relatively light and not heavy enough to accountfor the planet’s overall density. therefore there must be heavier stuff inside. we know that togenerate our magnetic field somewhere in the interior there must be a concentrated belt ofmetallic elements in a liquid state. that much is universally agreed upon. almost everythingbeyond that how the layers interact, what causes them to behave in the way they do, whatthey will do at any time in the future is a matter of at least some uncertainty, and generallyquite a lot of uncertainty. even the one part of it we can see, the crust, is a matter of some fairly strident debate.nearly all geology texts tell you that continental crust is three to six miles thick under theoceans, about twenty five miles thick under the continents, and forty to sixty miles thickunder big mountain chains, but there are many puzzling variabilities within thesegeneralizations. the crust beneath the sierra nevada mountains, for instance, is only aboutnineteen to twenty five miles thick, and no one knows why. by all the laws of geophysics thesierra nevadas should be sinking, as if into quicksand. (some people think they may be.)1 for those who crave a more detailed picture of the earth's interior, here are the dimensions of the variouslayers, using average figures: from 0 to 40 km (25 mi) is the crust. from 40 to 400 km (25 to 250 mi) is theupper mantle. from 400 to 650 km (250 to 400 mi) is a transition zone between the upper and lower mantle.from 650 to 2,700 km (400 to 1,700 mi) is the lower mantle. from 2,700 to 2,890 km (1,700 to 1,900 mi) is the\"d\" layer. from 2,890 to 5,150 km (1,900 to 3,200 mi) is the outer core, and from 5,150 to 6,378 km (3,200 to3,967 mi) is the inner core. how and when the earth got its crust are questions that divide geologists into two broadcamps those who think it happened abruptly early in the earth’s history and those who thinkit happened gradually and rather later. strength of feeling runs deep on such matters. richardarmstrong of yale proposed an early burst theory in the 1960s, then spent the rest of hiscareer fighting those who did not agree with him. he died of cancer in 1991, but shortlybefore his death he “lashed out at his critics in a polemic in an australian earth science journalthat charged them with perpetuating myths,” according to a report inearth magazine in 1998.“he died a bitter man,” reported a colleague. the crust and part of the outer mantle together are called the lithosphere (from the greeklithos, meaning “stone”), which in turn floats on top of a layer of softer rock called theasthenosphere (from greek words meaning “without strength”), but such terms are neverentirely satisfactory. to say that the lithosphere floats on top of the asthenosphere suggests adegree of easy buoyancy that isn’t quite right. similarly it is misleading to think of the rocksas flowing in anything like the way we think of materials flowing on the surface. the rocksare viscous, but only in the same way that glass is. it may not look it, but all the glass on earthis flowing downward under the relentless drag of gravity. remove a pane of really old glassfrom the window of a european cathedral and it will be noticeably thicker at the bottom thanat the top. that is the sort of “flow” we are talking about. the hour hand on a clock movesabout ten thousand times faster than the “flowing” rocks of the mantle. the movements occur not just laterally as the earth’s plates move across the surface, but upand down as well, as rocks rise and fall under the churning process known as convection.convection as a process was first deduced by the eccentric count von rumford at the end ofthe eighteenth century. sixty years later an english vicar named osmond fisher prescientlysuggested that the earth’s interior might well be fluid enough for the contents to move about,but that idea took a very long time to gain support. in about 1970, when geophysicists realized just how much turmoil was going on downthere, it came as a considerable shock. as shawna vogel put it in the book naked earth: thenew geophysics: “it was as if scientists had spent decades figuring out the layers of theearth’s atmosphere troposphere, stratosphere, and so forth and then had suddenly foundout about wind.” how deep the convection process goes has been a matter of controversy ever since. somesay it begins four hundred miles down, others two thousand miles below us. the problem, asdonald trefil has observed, is that “there are two sets of data, from two different disciplines,that cannot be reconciled.” geochemists say that certain elements on earth’s surface cannothave come from the upper mantle, but must have come from deeper within the earth.therefore the materials in the upper and lower mantle must at least occasionally mix.seismologists insist that there is no evidence to support such a thesis. so all that can be said is that at some slightly indeterminate point as we head toward thecenter of earth we leave the asthenosphere and plunge into pure mantle. considering that itaccounts for 82 percent of the earth’s volume and 65 percent of its mass, the mantle doesn’tattract a great deal of attention, largely because the things that interest earth scientists andgeneral readers alike happen either deeper down (as with magnetism) or nearer the surface (aswith earthquakes). we know that to a depth of about a hundred miles the mantle consistspredominantly of a type of rock known as peridotite, but what fills the space beyond isuncertain. according to a nature report, it seems not to be peridotite. more than this we donot know. beneath the mantle are the two cores a solid inner core and a liquid outer one. needless tosay, our understanding of the nature of these cores is indirect, but scientists can make somereasonable assumptions. they know that the pressures at the center of the earth aresufficiently high something over three million times those found at the surface to turn anyrock there solid. they also know from earth’s history (among other clues) that the inner coreis very good at retaining its heat. although it is little more than a guess, it is thought that inover four billion years the temperature at the core has fallen by no more than 200°f. no oneknows exactly how hot the earth’s core is, but estimates range from something over 7,000°fto 13,000°f about as hot as the surface of the sun. the outer core is in many ways even less well understood, though everyone is in agreementthat it is fluid and that it is the seat of magnetism. the theory was put forward by e. c.bullard of cambridge university in 1949 that this fluid part of the earth’s core revolves in away that makes it, in effect, an electrical motor, creating the earth’s magnetic field. theassumption is that the convecting fluids in the earth act somehow like the currents in wires.exactly what happens isn’t known, but it is felt pretty certain that it is connected with the corespinning and with its being liquid. bodies that don’t have a liquid core the moon and mars,for instance don’t have magnetism. we know that earth’s magnetic field changes in power from time to time: during the age ofthe dinosaurs, it was up to three times as strong as now. we also know that it reverses itselfevery 500,000 years or so on average, though that average hides a huge degree ofunpredictability. the last reversal was about 750,000 years ago. sometimes it stays put formillions of years 37 million years appears to be the longest stretch and at other times it hasreversed after as little as 20,000 years. altogether in the last 100 million years it has reverseditself about two hundred times, and we don’t have any real idea why. it has been called “thegreatest unanswered question in the geological sciences.” we may be going through a reversal now. the earth’s magnetic field has diminished byperhaps as much as 6 percent in the last century alone. any diminution in magnetism is likelyto be bad news, because magnetism, apart from holding notes to refrigerators and keeping ourcompasses pointing the right way, plays a vital role in keeping us alive. space is full ofdangerous cosmic rays that in the absence of magnetic protection would tear through ourbodies, leaving much of our dna in useless tatters. when the magnetic field is working,these rays are safely herded away from the earth’s surface and into two zones in near spacecalled the van allen belts. they also interact with particles in the upper atmosphere to createthe bewitching veils of light known as the auroras. a big part of the reason for our ignorance, interestingly enough, is that traditionally therehas been little effort to coordinate what’s happening on top of the earth with what’s going oninside. according to shawna vogel: “geologists and geophysicists rarely go to the samemeetings or collaborate on the same problems.” perhaps nothing better demonstrates our inadequate grasp of the dynamics of the earth’sinterior than how badly we are caught out when it acts up, and it would be hard to come upwith a more salutary reminder of the limitations of our understanding than the eruption ofmount st. helens in washington in 1980. at that time, the lower forty eight united states had not seen a volcanic eruption for oversixty five years. therefore the government volcanologists called in to monitor and forecast st. helens’s behavior primarily had seen only hawaiian volcanoes in action, and they, it turnedout, were not the same thing at all. st. helens started its ominous rumblings on march 20. within a week it was eruptingmagma, albeit in modest amounts, up to a hundred times a day, and being constantly shakenwith earthquakes. people were evacuated to what was assumed to be a safe distance of eightmiles. as the mountain’s rumblings grew st. helens became a tourist attraction for the world.newspapers gave daily reports on the best places to get a view. television crews repeatedlyflew in helicopters to the summit, and people were even seen climbing over the mountain. onone day, more than seventy copters and light aircraft circled the summit. but as the dayspassed and the rumblings failed to develop into anything dramatic, people grew restless, andthe view became general that the volcano wasn’t going to blow after all. on april 19 the northern flank of the mountain began to bulge conspicuously. remarkably,no one in a position of responsibility saw that this strongly signaled a lateral blast. theseismologists resolutely based their conclusions on the behavior of hawaiian volcanoes,which don’t blow out sideways. almost the only person who believed that something reallybad might happen was jack hyde, a geology professor at a community college in tacoma. hepointed out that st. helens didn’t have an open vent, as hawaiian volcanoes have, so anypressure building up inside was bound to be released dramatically and probablycatastrophically. however, hyde was not part of the official team and his observationsattracted little notice. we all know what happened next. at 8:32 a.m. on a sunday morning, may 18, the northside of the volcano collapsed, sending an enormous avalanche of dirt and rock rushing downthe mountain slope at 150 miles an hour. it was the biggest landslide in human history andcarried enough material to bury the whole of manhattan to a depth of four hundred feet. aminute later, its flank severely weakened, st. helens exploded with the force of five hundredhiroshima sized atomic bombs, shooting out a murderous hot cloud at up to 650 miles anhour much too fast, clearly, for anyone nearby to outrace. many people who were thought tobe in safe areas, often far out of sight of the volcano, were overtaken. fifty seven people werekilled. twenty three of the bodies were never found. the toll would have been much higherexcept that it was a sunday. had it been a weekday many lumber workers would have beenworking within the death zone. as it was, people were killed eighteen miles away. the luckiest person on that day was a graduate student named harry glicken. he had beenmanning an observation post 5.7 miles from the mountain, but he had a college placementinterview on may 18 in california, and so had left the site the day before the eruption. hisplace was taken by david johnston. johnston was the first to report the volcano exploding;moments later he was dead. his body was never found. glicken’s luck, alas, was temporary.eleven years later he was one of forty three scientists and journalists fatally caught up in alethal outpouring of superheated ash, gases, and molten rock what is known as a pyroclasticflow at mount unzen in japan when yet another volcano was catastrophically misread. volcanologists may or may not be the worst scientists in the world at making predictions,but they are without question the worst in the world at realizing how bad their predictions are.less than two years after the unzen catastrophe another group of volcano watchers, led bystanley williams of the university of arizona, descended into the rim of an active volcanocalled galeras in colombia. despite the deaths of recent years, only two of the sixteenmembers of williams’s party wore safety helmets or other protective gear. the volcano erupted, killing six of the scientists, along with three tourists who had followed them, andseriously injuring several others, including williams himself. in an extraordinarily unself critical book called surviving galeras, williams said he could“only shake my head in wonder” when he learned afterward that his colleagues in the worldof volcanology had suggested that he had overlooked or disregarded important seismic signalsand behaved recklessly. “how easy it is to snipe after the fact, to apply the knowledge wehave now to the events of 1993,” he wrote. he was guilty of nothing worse, he believed, thanunlucky timing when galeras “behaved capriciously, as natural forces are wont to do. i wasfooled, and for that i will take responsibility. but i do not feel guilty about the deaths of mycolleagues. there is no guilt. there was only an eruption.” but to return to washington. mount st. helens lost thirteen hundred feet of peak, and 230square miles of forest were devastated. enough trees to build 150,000 homes (or 300,000 insome reports) were blown away. the damage was placed at $2.7 billion. a giant column ofsmoke and ash rose to a height of sixty thousand feet in less than ten minutes. an airlinersome thirty miles away reported being pelted with rocks. ninety minutes after the blast, ash began to rain down on yakima, washington, acommunity of fifty thousand people about eighty miles away. as you would expect, the ashturned day to night and got into everything, clogging motors, generators, and electricalswitching equipment, choking pedestrians, blocking filtration systems, and generally bringingthings to a halt. the airport shut down and highways in and out of the city were closed. all this was happening, you will note, just downwind of a volcano that had been rumblingmenacingly for two months. yet yakima had no volcano emergency procedures. the city’semergency broadcast system, which was supposed to swing into action during a crisis, did notgo on the air because “the sunday morning staff did not know how to operate the equipment.”for three days, yakima was paralyzed and cut off from the world, its airport closed, itsapproach roads impassable. altogether the city received just five eighths of an inch of ashafter the eruption of mount st. helens. now bear that in mind, please, as we consider what ayellowstone blast would do. 15 dangerous beautyin the 1960s, while studying the volcanic history of yellowstone national park, bobchristiansen of the united states geological survey became puzzled about something that,oddly, had not troubled anyone before: he couldn’t find the park’s volcano. it had been knownfor a long time that yellowstone was volcanic in nature that’s what accounted for all itsgeysers and other steamy features and the one thing about volcanoes is that they aregenerally pretty conspicuous. but christiansen couldn’t find the yellowstone volcanoanywhere. in particular what he couldn’t find was a structure known as a caldera. most of us, when we think of volcanoes, think of the classic cone shapes of a fuji orkilimanjaro, which are created when erupting magma accumulates in a symmetrical mound.these can form remarkably quickly. in 1943, at parícutin in mexico, a farmer was startled tosee smoke rising from a patch on his land. in one week he was the bemused owner of a conefive hundred feet high. within two years it had topped out at almost fourteen hundred feet andwas more than half a mile across. altogether there are some ten thousand of these intrusivelyvisible volcanoes on earth, all but a few hundred of them extinct. but there is a second, lesscelebrated type of volcano that doesn’t involve mountain building. these are volcanoes soexplosive that they burst open in a single mighty rupture, leaving behind a vast subsided pit,the caldera (from a latin word for cauldron). yellowstone obviously was of this second type,but christiansen couldn’t find the caldera anywhere. by coincidence just at this time nasa decided to test some new high altitude cameras bytaking photographs of yellowstone, copies of which some thoughtful official passed on to thepark authorities on the assumption that they might make a nice blow up for one of thevisitors’ centers. as soon as christiansen saw the photos he realized why he had failed to spotthe caldera: virtually the whole park 2.2 million acres was caldera. the explosion had lefta crater more than forty miles across much too huge to be perceived from anywhere atground level. at some time in the past yellowstone must have blown up with a violence farbeyond the scale of anything known to humans. yellowstone, it turns out, is a supervolcano. it sits on top of an enormous hot spot, areservoir of molten rock that rises from at least 125 miles down in the earth. the heat fromthe hot spot is what powers all of yellowstone’s vents, geysers, hot springs, and popping mudpots. beneath the surface is a magma chamber that is about forty five miles across roughlythe same dimensions as the park and about eight miles thick at its thickest point. imagine apile of tnt about the size of rhode island and reaching eight miles into the sky, to about theheight of the highest cirrus clouds, and you have some idea of what visitors to yellowstoneare shuffling around on top of. the pressure that such a pool of magma exerts on the crustabove has lifted yellowstone and about three hundred miles of surrounding territory about1,700 feet higher than they would otherwise be. if it blew, the cataclysm is pretty well beyondimagining. according to professor bill mcguire of university college london, “youwouldn’t be able to get within a thousand kilometers of it” while it was erupting. theconsequences that followed would be even worse. superplumes of the type on which yellowstone sits are rather like martini glasses thin onthe way up, but spreading out as they near the surface to create vast bowls of unstable magma.some of these bowls can be up to 1,200 miles across. according to theories, they don’talways erupt explosively but sometimes burst forth in a vast, continuous outpouring aflood of molten rock, such as with the deccan traps in india sixty five million years ago.(trap in this context comes from a swedish word for a type of lava; deccan is simply anarea.) these covered an area of 200,000 square miles and probably contributed to the demiseof the dinosaurs they certainly didn’t help with their noxious outgassings. superplumesmay also be responsible for the rifts that cause continents to break up. such plumes are not all that rare. there are about thirty active ones on the earth at themoment, and they are responsible for many of the world’s best known islands and islandchains iceland, hawaii, the azores, canaries, and galápagos archipelagos, little pitcairn inthe middle of the south pacific, and many others but apart from yellowstone they are alloceanic. no one has the faintest idea how or why yellowstone’s ended up beneath acontinental plate. only two things are certain: that the crust at yellowstone is thin and that theworld beneath it is hot. but whether the crust is thin because of the hot spot or whether the hotspot is there because the crust is thin is a matter of heated (as it were) debate. the continentalnature of the crust makes a huge difference to its eruptions. where the other supervolcanoestend to bubble away steadily and in a comparatively benign fashion, yellowstone blowsexplosively. it doesn’t happen often, but when it does you want to stand well back. since its first known eruption 16.5 million years ago, it has blown up about a hundredtimes, but the most recent three eruptions are the ones that get written about. the last eruptionwas a thousand times greater than that of mount st. helens; the one before that was 280 timesbigger, and the one before was so big that nobody knows exactly how big it was. it was atleast twenty five hundred times greater than st. helens, but perhaps eight thousand timesmore monstrous. we have absolutely nothing to compare it to. the biggest blast in recent times was that ofkrakatau in indonesia in august 1883, which made a bang that reverberated around the worldfor nine days, and made water slosh as far away as the english channel. but if you imaginethe volume of ejected material from krakatau as being about the size of a golf ball, then thebiggest of the yellowstone blasts would be the size of a sphere you could just about hidebehind. on this scale, mount st. helens’s would be no more than a pea. the yellowstone eruption of two million years ago put out enough ash to bury new yorkstate to a depth of sixty seven feet or california to a depth of twenty. this was the ash thatmade mike voorhies’s fossil beds in eastern nebraska. that blast occurred in what is nowidaho, but over millions of years, at a rate of about one inch a year, the earth’s crust hastraveled over it, so that today it is directly under northwest wyoming. (the hot spot itselfstays in one place, like an acetylene torch aimed at a ceiling.) in its wake it leaves the sort ofrich volcanic plains that are ideal for growing potatoes, as idaho’s farmers long agodiscovered. in another two million years, geologists like to joke, yellowstone will beproducing french fries for mcdonald’s, and the people of billings, montana, will be steppingaround geysers. the ash fall from the last yellowstone eruption covered all or parts of nineteen westernstates (plus parts of canada and mexico) nearly the whole of the united states west of themississippi. this, bear in mind, is the breadbasket of america, an area that produces roughlyhalf the world’s cereals. and ash, it is worth remembering, is not like a big snowfall that will melt in the spring. if you wanted to grow crops again, you would have to find some place toput all the ash. it took thousands of workers eight months to clear 1.8 billion tons of debrisfrom the sixteen acres of the world trade center site in new york. imagine what it wouldtake to clear kansas. and that’s not even to consider the climatic consequences. the last supervolcano eruptionon earth was at toba, in northern sumatra, seventy four thousand years ago. no one knowsquite how big it was other than that it was a whopper. greenland ice cores show that the tobablast was followed by at least six years of “volcanic winter” and goodness knows how manypoor growing seasons after that. the event, it is thought, may have carried humans right to thebrink of extinction, reducing the global population to no more than a few thousandindividuals. that means that all modern humans arose from a very small population base,which would explain our lack of genetic diversity. at all events, there is some evidence tosuggest that for the next twenty thousand years the total number of people on earth was nevermore than a few thousand at any time. that is, needless to say, a long time to recover from asingle volcanic blast. all this was hypothetically interesting until 1973, when an odd occurrence made itsuddenly momentous: water in yellowstone lake, in the heart of the park, began to run overthe banks at the lake’s southern end, flooding a meadow, while at the opposite end of the lakethe water mysteriously flowed away. geologists did a hasty survey and discovered that a largearea of the park had developed an ominous bulge. this was lifting up one end of the lake andcausing the water to run out at the other, as would happen if you lifted one side of a child’swading pool. by 1984, the whole central region of the park several dozen square miles was more than three feet higher than it had been in 1924, when the park was last formallysurveyed. then in 1985, the whole of the central part of the park subsided by eight inches. itnow seems to be swelling again. the geologists realized that only one thing could cause this a restless magma chamber.yellowstone wasn’t the site of an ancient supervolcano; it was the site of an active one. it wasalso at about this time that they were able to work out that the cycle of yellowstone’seruptions averaged one massive blow every 600,000 years. the last one, interestingly enough,was 630,000 years ago. yellowstone, it appears, is due. “it may not feel like it, but you’re standing on the largest active volcano in the world,” pauldoss, yellowstone national park geologist, told me soon after climbing off an enormousharley davidson motorcycle and shaking hands when we met at the park headquarters atmammoth hot springs early on a lovely morning in june. a native of indiana, doss is anamiable, soft spoken, extremely thoughtful man who looks nothing like a national parkservice employee. he has a graying beard and hair tied back in a long ponytail. a smallsapphire stud graces one ear. a slight paunch strains against his crisp park service uniform.he looks more like a blues musician than a government employee. in fact, he is a bluesmusician (harmonica). but he sure knows and loves geology. “and i’ve got the best place inthe world to do it,” he says as we set off in a bouncy, battered four wheel drive vehicle in thegeneral direction of old faithful. he has agreed to let me accompany him for a day as he goesabout doing whatever it is a park geologist does. the first assignment today is to give anintroductory talk to a new crop of tour guides. yellowstone, i hardly need point out, is sensationally beautiful, with plump, statelymountains, bison specked meadows, tumbling streams, a sky blue lake, wildlife beyondcounting. “it really doesn’t get any better than this if you’re a geologist,” doss says. “you’vegot rocks up at beartooth gap that are nearly three billion years old three quarters of theway back to earth’s beginning and then you’ve got mineral springs here” he points at thesulfurous hot springs from which mammoth takes its title “where you can see rocks as theyare being born. and in between there’s everything you could possibly imagine. i’ve neverbeen any place where geology is more evident or prettier.” “so you like it?” i say. “oh, no, i love it,” he answers with profound sincerity. “i mean i really love it here. thewinters are tough and the pay’s not too hot, but when it’s good, it’s just ” he interrupted himself to point out a distant gap in a range of mountains to the west, whichhad just come into view over a rise. the mountains, he told me, were known as the gallatins.“that gap is sixty or maybe seventy miles across. for a long time nobody could understandwhy that gap was there, and then bob christiansen realized that it had to be because themountains were just blown away. when you’ve got sixty miles of mountains just obliterated,you know you’re dealing with something pretty potent. it took christiansen six years to figureit all out.” i asked him what caused yellowstone to blow when it did. “don’t know. nobody knows. volcanoes are strange things. we really don’t understandthem at all. vesuvius, in italy, was active for three hundred years until an eruption in 1944and then it just stopped. it’s been silent ever since. some volcanologists think that it isrecharging in a big way, which is a little worrying because two million people live on oraround it. but nobody knows.” “and how much warning would you get if yellowstone was going to go?” he shrugged. “nobody was around the last time it blew, so nobody knows what thewarning signs are. probably you would have swarms of earthquakes and some surface upliftand possibly some changes in the patterns of behavior of the geysers and steam vents, butnobody really knows.” “so it could just blow without warning?” he nodded thoughtfully. the trouble, he explained, is that nearly all the things that wouldconstitute warning signs already exist in some measure at yellowstone. “earthquakes aregenerally a precursor of volcanic eruptions, but the park already has lots of earthquakes 1,260 of them last year. most of them are too small to be felt, but they are earthquakesnonetheless.” a change in the pattern of geyser eruptions might also be taken as a clue, he said, but thesetoo vary unpredictably. once the most famous geyser in the park was excelsior geyser. itused to erupt regularly and spectacularly to heights of three hundred feet, but in 1888 it juststopped. then in 1985 it erupted again, though only to a height of eighty feet. steamboatgeyser is the biggest geyser in the world when it blows, shooting water four hundred feet intothe air, but the intervals between its eruptions have ranged from as little as four days to almost fifty years. “if it blew today and again next week, that wouldn’t tell us anything at all aboutwhat it might do the following week or the week after or twenty years from now,” doss says.“the whole park is so volatile that it’s essentially impossible to draw conclusions from almostanything that happens.” evacuating yellowstone would never be easy. the park gets some three million visitors ayear, mostly in the three peak months of summer. the park’s roads are comparatively few andthey are kept intentionally narrow, partly to slow traffic, partly to preserve an air ofpicturesqueness, and partly because of topographical constraints. at the height of summer, itcan easily take half a day to cross the park and hours to get anywhere within it. “wheneverpeople see animals, they just stop, wherever they are,” doss says. “we get bear jams. we getbison jams. we get wolf jams.” in the autumn of 2000, representatives from the u.s. geological survey and national parkservice, along with some academics, met and formed something called the yellowstonevolcanic observatory. four such bodies were in existence already in hawaii, california,alaska, and washington but oddly none in the largest volcanic zone in the world. the yvois not actually a thing, but more an idea an agreement to coordinate efforts at studying andanalyzing the park’s diverse geology. one of their first tasks, doss told me, was to draw up an“earthquake and volcano hazards plan” a plan of action in the event of a crisis. “there isn’t one already?” i said. “no. afraid not. but there will be soon.” “isn’t that just a little tardy?” he smiled. “well, let’s just say that it’s not any too soon.” once it is in place, the idea is that three people christiansen in menlo park, california,professor robert b. smith at the university of utah, and doss in the park would assess thedegree of danger of any potential cataclysm and advise the park superintendent. thesuperintendent would take the decision whether to evacuate the park. as for surroundingareas, there are no plans. if yellowstone were going to blow in a really big way, you would beon your own once you left the park gates. of course it may be tens of thousands of years before that day comes. doss thinks such aday may not come at all. “just because there was a pattern in the past doesn’t mean that it stillholds true,” he says. “there is some evidence to suggest that the pattern may be a series ofcatastrophic explosions, then a long period of quiet. we may be in that now. the evidencenow is that most of the magma chamber is cooling and crystallizing. it is releasing itsvolatiles; you need to trap volatiles for an explosive eruption.” in the meantime there are plenty of other dangers in and around yellowstone, as was madedevastatingly evident on the night of august 17, 1959, at a place called hebgen lake justoutside the park. at twenty minutes to midnight on that date, hebgen lake suffered acatastrophic quake. it was magnitude 7.5, not vast as earthquakes go, but so abrupt andwrenching that it collapsed an entire mountainside. it was the height of the summer season,though fortunately not so many people went to yellowstone in those days as now. eighty million tons of rock, moving at more than one hundred miles an hour, just fell off themountain, traveling with such force and momentum that the leading edge of the landslide ranfour hundred feet up a mountain on the other side of the valley. along its path lay part of therock creek campground. twenty eight campers were killed, nineteen of them buried toodeep ever to be found again. the devastation was swift but heartbreakingly fickle. threebrothers, sleeping in one tent, were spared. their parents, sleeping in another tent besidethem, were swept away and never seen again. “a big earthquake and i mean big will happen sometime,” doss told me. “you cancount on that. this is a big fault zone for earthquakes.” despite the hebgen lake quake and the other known risks, yellowstone didn’t getpermanent seismometers until the 1970s. if you needed a way to appreciate the grandeur and inexorable nature of geologic processes,you could do worse than to consider the tetons, the sumptuously jagged range that stands justto the south of yellowstone national park. nine million years ago, the tetons didn’t exist.the land around jackson hole was just a high grassy plain. but then a forty mile long faultopened within the earth, and since then, about once every nine hundred years, the tetonsexperience a really big earthquake, enough to jerk them another six feet higher. it is theserepeated jerks over eons that have raised them to their present majestic heights of seventhousand feet. that nine hundred years is an average and a somewhat misleading one. according torobert b. smith and lee j. siegel in windows into the earth , a geological history of theregion, the last major teton quake was somewhere between about five and seven thousandyears ago. the tetons, in short, are about the most overdue earthquake zone on the planet. hydrothermal explosions are also a significant risk. they can happen anytime, pretty muchanywhere, and without any predictability. “you know, by design we funnel visitors intothermal basins,” doss told me after we had watched old faithful blow. “it’s what they cometo see. did you know there are more geysers and hot springs at yellowstone than in all therest of the world combined?” “i didn’t know that.” he nodded. “ten thousand of them, and nobody knows when a new vent might open.” wedrove to a place called duck lake, a body of water a couple of hundred yards across. “it lookscompletely innocuous,” he said. “it’s just a big pond. but this big hole didn’t used to be here.at some time in the last fifteen thousand years this blew in a really big way. you’d have hadseveral tens of millions of tons of earth and rock and superheated water blowing out athypersonic speeds. you can imagine what it would be like if this happened under, say, theparking lot at old faithful or one of the visitors’ centers.” he made an unhappy face. “would there be any warning?” “probably not. the last significant explosion in the park was at a place called pork chopgeyser in 1989. that left a crater about five meters across not huge by any means, but bigenough if you happened to be standing there at the time. fortunately, nobody was around so nobody was hurt, but that happened without warning. in the very ancient past there have beenexplosions that have made holes a mile across. and nobody can tell you where or when thatmight happen again. you just have to hope that you’re not standing there when it does.” big rockfalls are also a danger. there was a big one at gardiner canyon in 1999, but againfortunately no one was hurt. late in the afternoon, doss and i stopped at a place where therewas a rock overhang poised above a busy park road. cracks were clearly visible. “it could goat any time,” doss said thoughtfully. “you’re kidding,” i said. there wasn’t a moment when there weren’t two cars passingbeneath it, all filled with, in the most literal sense, happy campers. “oh, it’s not likely,” he added. “i’m just saying it could. equally it could stay like that fordecades. there’s just no telling. people have to accept that there is risk in coming here. that’sall there is to it.” as we walked back to his vehicle to head back to mammoth hot springs, doss added: “butthe thing is, most of the time bad things don’t happen. rocks don’t fall. earthquakes don’toccur. new vents don’t suddenly open up. for all the instability, it’s mostly remarkably andamazingly tranquil.” “like earth itself,” i remarked. “precisely,” he agreed. the risks at yellowstone apply to park employees as much as to visitors. doss got ahorrific sense of that in his first week on the job five years earlier. late one night, three youngsummer employees engaged in an illicit activity known as “hot potting” swimming orbasking in warm pools. though the park, for obvious reasons, doesn’t publicize it, not all thepools in yellowstone are dangerously hot. some are extremely agreeable to lie in, and it wasthe habit of some of the summer employees to have a dip late at night even though it wasagainst the rules to do so. foolishly the threesome had failed to take a flashlight, which wasextremely dangerous because much of the soil around the warm pools is crusty and thin andone can easily fall through into a scalding vent below. in any case, as they made their wayback to their dorm, they came across a stream that they had had to leap over earlier. theybacked up a few paces, linked arms and, on the count of three, took a running jump. in fact, itwasn’t the stream at all. it was a boiling pool. in the dark they had lost their bearings. none ofthe three survived. i thought about this the next morning as i made a brief call, on my way out of the park, at aplace called emerald pool, in the upper geyser basin. doss hadn’t had time to take me therethe day before, but i thought i ought at least to have a look at it, for emerald pool is a historicsite. in 1965, a husband and wife team of biologists named thomas and louise brock, while ona summer study trip, had done a crazy thing. they had scooped up some of the yellowy brown scum that rimmed the pool and examined it for life. to their, and eventually the widerworld’s, deep surprise, it was full of living microbes. they had found the world’s firstextremophiles organisms that could live in water that had previously been assumed to be much too hot or acid or choked with sulfur to bear life. emerald pool, remarkably, was allthese things, yet at least two types of living things, sulpholobus acidocaldarius andthermophilus aquaticus as they became known, found it congenial. it had always beensupposed that nothing could survive above temperatures of 50°c (122°f), but here wereorganisms basking in rank, acidic waters nearly twice that hot. for almost twenty years, one of the brocks’ two new bacteria, thermophilus aquaticus,remained a laboratory curiosity until a scientist in california named kary b. mullis realizedthat heat resistant enzymes within it could be used to create a bit of chemical wizardry knownas a polymerase chain reaction, which allows scientists to generate lots of dna from verysmall amounts as little as a single molecule in ideal conditions. it’s a kind of geneticphotocopying, and it became the basis for all subsequent genetic science, from academicstudies to police forensic work. it won mullis the nobel prize in chemistry in 1993. meanwhile, scientists were finding even hardier microbes, now known ashyperthermophiles, which demand temperatures of 80°c (176°f) or more. the warmestorganism found so far, according to frances ashcroft in life at the extremes, is pyrolobusfumarii, which dwells in the walls of ocean vents where the temperature can reach 113°c(235.4°f). the upper limit for life is thought to be about 120°c (248°f), though no oneactually knows. at all events, the brocks’ findings completely changed our perception of theliving world. as nasa scientist jay bergstralh has put it: “wherever we go on earth eveninto what’s seemed like the most hostile possible environments for life as long as there isliquid water and some source of chemical energy we find life.” life, it turns out, is infinitely more clever and adaptable than anyone had ever supposed.this is a very good thing, for as we are about to see, we live in a world that doesn’t altogetherseem to want us here. part v life itselfthe more i examine the universeand study the details of its architecture,the more evidence i find that theuniverse in some sense must haveknown we were coming.  freeman dyson 16 lonely planetit isn’t easy being an organism. in the whole universe, as far as we yet know, there isonly one place, an inconspicuous outpost of the milky way called earth, that will sustain you,and even it can be pretty grudging. from the bottom of the deepest ocean trench to the top of the highest mountain, the zonethat covers nearly the whole of known life, is only something over a dozen miles not muchwhen set against the roominess of the cosmos at large. for humans it is even worse because we happen to belong to the portion of living thingsthat took the rash but venturesome decision 400 million years ago to crawl out of the seas andbecome land based and oxygen breathing. in consequence, no less than 99.5 percent of theworld’s habitable space by volume, according to one estimate, is fundamentally in practicalterms completely off limits to us. it isn’t simply that we can’t breathe in water, but that we couldn’t bear the pressures.because water is about 1,300 times heavier than air, pressures rise swiftly as you descend by the equivalent of one atmosphere for every ten meters (thirty three feet) of depth. on land,if you rose to the top of a five hundred foot eminence cologne cathedral or the washingtonmonument, say the change in pressure would be so slight as to be indiscernible. at the samedepth underwater, however, your veins would collapse and your lungs would compress to theapproximate dimensions of a coke can. amazingly, people do voluntarily dive to such depths,without breathing apparatus, for the fun of it in a sport known as free diving. apparently theexperience of having your internal organs rudely deformed is thought exhilarating (though notpresumably as exhilarating as having them return to their former dimensions uponresurfacing). to reach such depths, however, divers must be dragged down, and quite briskly,by weights. without assistance, the deepest anyone has gone and lived to talk about itafterward was an italian named umberto pelizzari, who in 1992 dove to a depth of 236 feet,lingered for a nanosecond, and then shot back to the surface. in terrestrial terms, 236 feet isjust slightly over the length of one new york city block. so even in our most exuberantstunts we can hardly claim to be masters of the abyss. other organisms do of course manage to deal with the pressures at depth, though quite howsome of them do so is a mystery. the deepest point in the ocean is the mariana trench in thepacific. there, some seven miles down, the pressures rise to over sixteen thousand pounds persquare inch. we have managed once, briefly, to send humans to that depth in a sturdy divingvessel, yet it is home to colonies of amphipods, a type of crustacean similar to shrimp buttransparent, which survive without any protection at all. most oceans are of course much shallower, but even at the average ocean depth of two and a half miles the pressure isequivalent to being squashed beneath a stack of fourteen loaded cement trucks. nearly everyone, including the authors of some popular books on oceanography, assumesthat the human body would crumple under the immense pressures of the deep ocean. in fact,this appears not to be the case. because we are made largely of water ourselves, and water is“virtually incompressible,” in the words of frances ashcroft of oxford university, “the bodyremains at the same pressure as the surrounding water, and is not crushed at depth.” it is thegases inside your body, particularly in the lungs, that cause the trouble. these do compress,though at what point the compression becomes fatal is not known. until quite recently it wasthought that anyone diving to one hundred meters or so would die painfully as his or her lungsimploded or chest wall collapsed, but the free divers have repeatedly proved otherwise. itappears, according to ashcroft, that “humans may be more like whales and dolphins than hadbeen expected.” plenty else can go wrong, however. in the days of diving suits the sort that wereconnected to the surface by long hoses divers sometimes experienced a dreadedphenomenon known as “the squeeze.” this occurred when the surface pumps failed, leadingto a catastrophic loss of pressure in the suit. the air would leave the suit with such violencethat the hapless diver would be, all too literally, sucked up into the helmet and hosepipe.when hauled to the surface, “all that is left in the suit are his bones and some rags of flesh,”the biologist j. b. s. haldane wrote in 1947, adding for the benefit of doubters, “this hashappened.” (incidentally, the original diving helmet, designed in 1823 by an englishman namedcharles deane, was intended not for diving but for fire fighting. it was called a “smokehelmet,” but being made of metal it was hot and cumbersome and, as deane soon discovered,firefighters had no particular eagerness to enter burning structures in any form of attire, butmost especially not in something that heated up like a kettle and made them clumsy into thebargain. in an attempt to save his investment, deane tried it underwater and found it was idealfor salvage work.) the real terror of the deep, however, is the bends not so much because they areunpleasant, though of course they are, as because they are so much more likely. the air webreathe is 80 percent nitrogen. put the human body under pressure, and that nitrogen istransformed into tiny bubbles that migrate into the blood and tissues. if the pressure ischanged too rapidly as with a too quick ascent by a diver the bubbles trapped within thebody will begin to fizz in exactly the manner of a freshly opened bottle of champagne,clogging tiny blood vessels, depriving cells of oxygen, and causing pain so excruciating thatsufferers are prone to bend double in agony hence “the bends.” the bends have been an occupational hazard for sponge and pearl divers since timeimmemorial but didn’t attract much attention in the western world until the nineteenthcentury, and then it was among people who didn’t get wet at all (or at least not very wet andnot generally much above the ankles). they were caisson workers. caissons were encloseddry chambers built on riverbeds to facilitate the construction of bridge piers. they were filledwith compressed air, and often when the workers emerged after an extended period ofworking under this artificial pressure they experienced mild symptoms like tingling or itchyskin. but an unpredictable few felt more insistent pain in the joints and occasionally collapsedin agony, sometimes never to get up again. it was all most puzzling. sometimes workers would go to bed feeling fine, but wake upparalyzed. sometimes they wouldn’t wake up at all. ashcroft relates a story concerning thedirectors of a new tunnel under the thames who held a celebratory banquet as the tunnelneared completion. to their consternation their champagne failed to fizz when uncorked inthe compressed air of the tunnel. however, when at length they emerged into the fresh air of alondon evening, the bubbles sprang instantly to fizziness, memorably enlivening thedigestive process. apart from avoiding high pressure environments altogether, only two strategies are reliablysuccessful against the bends. the first is to suffer only a very short exposure to the changes inpressure. that is why the free divers i mentioned earlier can descend to depths of five hundredfeet without ill effect. they don’t stay under long enough for the nitrogen in their system todissolve into their tissues. the other solution is to ascend by careful stages. this allows thelittle bubbles of nitrogen to dissipate harmlessly. a great deal of what we know about surviving at extremes is owed to the extraordinaryfather and son team of john scott and j. b. s. haldane. even by the demanding standards ofbritish intellectuals, the haldanes were outstandingly eccentric. the senior haldane was bornin 1860 to an aristocratic scottish family (his brother was viscount haldane) but spent mostof his career in comparative modesty as a professor of physiology at oxford. he wasfamously absent minded. once after his wife had sent him upstairs to change for a dinnerparty he failed to return and was discovered asleep in bed in his pajamas. when roused,haldane explained that he had found himself disrobing and assumed it was bedtime. his ideaof a vacation was to travel to cornwall to study hookworm in miners. aldous huxley, thenovelist grandson of t. h. huxley, who lived with the haldanes for a time, parodied him, atouch mercilessly, as the scientist edward tantamount in the novel point counter point . haldane’s gift to diving was to work out the rest intervals necessary to manage an ascentfrom the depths without getting the bends, but his interests ranged across the whole ofphysiology, from studying altitude sickness in climbers to the problems of heatstroke in desertregions. he had a particular interest in the effects of toxic gases on the human body. tounderstand more exactly how carbon monoxide leaks killed miners, he methodically poisonedhimself, carefully taking and measuring his own blood samples the while. he quit only whenhe was on the verge of losing all muscle control and his blood saturation level had reached 56percent a level, as trevor norton notes in his entertaining history of diving, stars beneaththe sea, only fractionally removed from nearly certain lethality. haldane’s son jack, known to posterity as j.b.s., was a remarkable prodigy who took aninterest in his father’s work almost from infancy. at the age of three he was overhearddemanding peevishly of his father, “but is it oxyhaemoglobin or carboxyhaemoglobin?”throughout his youth, the young haldane helped his father with experiments. by the time hewas a teenager, the two often tested gases and gas masks together, taking turns to see howlong it took them to pass out. though j. b. s. haldane never took a degree in science (he studied classics at oxford), hebecame a brilliant scientist in his own right, mostly in cambridge. the biologist petermedawar, who spent his life around mental olympians, called him “the cleverest man i everknew.” huxley likewise parodied the younger haldane in his novel antic hay, but also usedhis ideas on genetic manipulation of humans as the basis for the plot of brave new world.among many other achievements, haldane played a central role in marrying darwinian principles of evolution to the genetic work of gregor mendel to produce what is known togeneticists as the modern synthesis.perhaps uniquely among human beings, the younger haldane found world war i “a veryenjoyable experience” and freely admitted that he “enjoyed the opportunity of killing people.”he was himself wounded twice. after the war he became a successful popularizer of scienceand wrote twenty three books (as well as over four hundred scientific papers). his books arestill thoroughly readable and instructive, though not always easy to find. he also became anenthusiastic marxist. it has been suggested, not altogether cynically, that this was out of apurely contrarian instinct, and that if he had been born in the soviet union he would havebeen a passionate monarchist. at all events, most of his articles first appeared in thecommunist daily worker. whereas his father’s principal interests concerned miners and poisoning, the youngerhaldane became obsessed with saving submariners and divers from the unpleasantconsequences of their work. with admiralty funding he acquired a decompression chamberthat he called the “pressure pot.” this was a metal cylinder into which three people at a timecould be sealed and subjected to tests of various types, all painful and nearly all dangerous.volunteers might be required to sit in ice water while breathing “aberrant atmosphere” orsubjected to rapid changes of pressurization. in one experiment, haldane simulated adangerously hasty ascent to see what would happen. what happened was that the dentalfillings in his teeth exploded. “almost every experiment,” norton writes, “ended withsomeone having a seizure, bleeding, or vomiting.” the chamber was virtually soundproof, sothe only way for occupants to signal unhappiness or distress was to tap insistently on thechamber wall or to hold up notes to a small window. on another occasion, while poisoning himself with elevated levels of oxygen, haldane hada fit so severe that he crushed several vertebrae. collapsed lungs were a routine hazard.perforated eardrums were quite common, but, as haldane reassuringly noted in one of hisessays, “the drum generally heals up; and if a hole remains in it, although one is somewhatdeaf, one can blow tobacco smoke out of the ear in question, which is a socialaccomplishment.” what was extraordinary about this was not that haldane was willing to subject himself tosuch risk and discomfort in the pursuit of science, but that he had no trouble talkingcolleagues and loved ones into climbing into the chamber, too. sent on a simulated descent,his wife once had a fit that lasted thirteen minutes. when at last she stopped bouncing acrossthe floor, she was helped to her feet and sent home to cook dinner. haldane happily employedwhoever happened to be around, including on one memorable occasion a former primeminister of spain, juan negrín. dr. negrín complained afterward of minor tingling and “acurious velvety sensation on the lips” but otherwise seems to have escaped unharmed. he mayhave considered himself very lucky. a similar experiment with oxygen deprivation lefthaldane without feeling in his buttocks and lower spine for six years. among haldane’s many specific preoccupations was nitrogen intoxication. for reasons thatare still poorly understood, beneath depths of about a hundred feet nitrogen becomes apowerful intoxicant. under its influence divers had been known to offer their air hoses topassing fish or decide to try to have a smoke break. it also produced wild mood swings. inone test, haldane noted, the subject “alternated between depression and elation, at onemoment begging to be decompressed because he felt ‘bloody awful’ and the next minutelaughing and attempting to interfere with his colleague’s dexterity test.” in order to measure the rate of deterioration in the subject, a scientist had to go into the chamber with thevolunteer to conduct simple mathematical tests. but after a few minutes, as haldane laterrecalled, “the tester was usually as intoxicated as the testee, and often forgot to press thespindle of his stopwatch, or to take proper notes.” the cause of the inebriation is even now amystery. it is thought that it may be the same thing that causes alcohol intoxication, but as noone knows for certain what causes that we are none the wiser. at all events, without thegreatest care, it is easy to get in trouble once you leave the surface world. which brings us back (well, nearly) to our earlier observation that earth is not the easiestplace to be an organism, even if it is the only place. of the small portion of the planet’ssurface that is dry enough to stand on, a surprisingly large amount is too hot or cold or dry orsteep or lofty to be of much use to us. partly, it must be conceded, this is our fault. in terms ofadaptability, humans are pretty amazingly useless. like most animals, we don’t much likereally hot places, but because we sweat so freely and easily stroke, we are especiallyvulnerable. in the worst circumstances on foot without water in a hot desert most peoplewill grow delirious and keel over, possibly never to rise again, in no more than six or sevenhours. we are no less helpless in the face of cold. like all mammals, humans are good atgenerating heat but because we are so nearly hairless not good at keeping it. even in quitemild weather half the calories you burn go to keep your body warm. of course, we cancounter these frailties to a large extent by employing clothing and shelter, but even so theportions of earth on which we are prepared or able to live are modest indeed: just 12 percentof the total land area, and only 4 percent of the whole surface if you include the seas. yet when you consider conditions elsewhere in the known universe, the wonder is not thatwe use so little of our planet but that we have managed to find a planet that we can use even abit of. you have only to look at our own solar system or, come to that, earth at certainperiods in its own history to appreciate that most places are much harsher and much lessamenable to life than our mild, blue watery globe. so far space scientists have discovered about seventy planets outside the solar system, outof the ten billion trillion or so that are thought to be out there, so humans can hardly claim tospeak with authority on the matter, but it appears that if you wish to have a planet suitable forlife, you have to be just awfully lucky, and the more advanced the life, the luckier you have tobe. various observers have identified about two dozen particularly helpful breaks we havehad on earth, but this is a flying survey so we’ll distill them down to the principal four. theyare:excellent location.we are, to an almost uncanny degree, the right distance from the right sortof star, one that is big enough to radiate lots of energy, but not so big as to burn itself outswiftly. it is a curiosity of physics that the larger a star the more rapidly it burns. had our sunbeen ten times as massive, it would have exhausted itself after ten million years instead of tenbillion and we wouldn’t be here now. we are also fortunate to orbit where we do. too muchnearer and everything on earth would have boiled away. much farther away and everythingwould have frozen. in 1978, an astrophysicist named michael hart made some calculations and concluded thatearth would have been uninhabitable had it been just 1 percent farther from or 5 percent closer to the sun. that’s not much, and in fact it wasn’t enough. the figures have since beenrefined and made a little more generous 5 percent nearer and 15 percent farther are thoughtto be more accurate assessments for our zone of habitability but that is still a narrow belt.1 to appreciate just how narrow, you have only to look at venus. venus is only twenty fivemillion miles closer to the sun than we are. the sun’s warmth reaches it just two minutesbefore it touches us. in size and composition, venus is very like earth, but the smalldifference in orbital distance made all the difference to how it turned out. it appears thatduring the early years of the solar system venus was only slightly warmer than earth andprobably had oceans. but those few degrees of extra warmth meant that venus could not holdon to its surface water, with disastrous consequences for its climate. as its water evaporated,the hydrogen atoms escaped into space, and the oxygen atoms combined with carbon to forma dense atmosphere of the greenhouse gas co2. venus became stifling. although people ofmy age will recall a time when astronomers hoped that venus might harbor life beneath itspadded clouds, possibly even a kind of tropical verdure, we now know that it is much toofierce an environment for any kind of life that we can reasonably conceive of. its surfacetemperature is a roasting 470 degrees centigrade (roughly 900 degrees fahrenheit), which ishot enough to melt lead, and the atmospheric pressure at the surface is ninety times that ofearth, or more than any human body could withstand. we lack the technology to make suitsor even spaceships that would allow us to visit. our knowledge of venus’s surface is based ondistant radar imagery and some startled squawks from an unmanned soviet probe that wasdropped hopefully into the clouds in 1972 and functioned for barely an hour beforepermanently shutting down. so that’s what happens when you move two light minutes closer to the sun. travel fartherout and the problem becomes not heat but cold, as mars frigidly attests. it, too, was once amuch more congenial place, but couldn’t retain a usable atmosphere and turned into a frozenwaste. but just being the right distance from the sun cannot be the whole story, for otherwise themoon would be forested and fair, which patently it is not. for that you need to have: the right kind of planet.i don’t imagine even many geophysicists, when asked to counttheir blessings, would include living on a planet with a molten interior, but it’s a pretty nearcertainty that without all that magma swirling around beneath us we wouldn’t be here now.apart from much else, our lively interior created the outgassing that helped to build anatmosphere and provided us with the magnetic field that shields us from cosmic radiation. italso gave us plate tectonics, which continually renews and rumples the surface. if earth wereperfectly smooth, it would be covered everywhere with water to a depth of four kilometers.there might be life in that lonesome ocean, but there certainly wouldn’t be baseball. in addition to having a beneficial interior, we also have the right elements in the correctproportions. in the most literal way, we are made of the right stuff. this is so crucial to ourwell being that we are going to discuss it more fully in a minute, but first we need to considerthe two remaining factors, beginning with another one that is often overlooked:1 the discovery of extremophiles in the boiling mudpots of yellowstone and similar organisms found elsewheremade scientists realize that actually life of a type could range much farther than that even, perhaps, beneath theicy skin of pluto. what we are talking about here are the conditions that would produce reasonably complexsurface creatures. we’re a twin planet.not many of us normally think of the moon as a companion planet,but that is in effect what it is. most moons are tiny in relation to their master planet. themartian satellites of phobos and deimos, for instance, are only about ten kilometers indiameter. our moon, however, is more than a quarter the diameter of the earth, which makesours the only planet in the solar system with a sizeable moon in comparison to itself (exceptpluto, which doesn’t really count because pluto is itself so small), and what a difference thatmakes to us. without the moon’s steadying influence, the earth would wobble like a dying top, withgoodness knows what consequences for climate and weather. the moon’s steady gravitationalinfluence keeps the earth spinning at the right speed and angle to provide the sort of stabilitynecessary for the long and successful development of life. this won’t go on forever. themoon is slipping from our grasp at a rate of about 1.5 inches a year. in another two billionyears it will have receded so far that it won’t keep us steady and we will have to come up withsome other solution, but in the meantime you should think of it as much more than just apleasant feature in the night sky. for a long time, astronomers assumed that the moon and earth either formed together orthat the earth captured the moon as it drifted by. we now believe, as you will recall from anearlier chapter, that about 4.5 billion years ago a mars sized object slammed into earth,blowing out enough material to create the moon from the debris. this was obviously a verygood thing for us but especially so as it happened such a long time ago. if it had happened in1896 or last wednesday clearly we wouldn’t be nearly so pleased about it. which brings us toour fourth and in many ways most crucial consideration: timing.the universe is an amazingly fickle and eventful place, and our existence within itis a wonder. if a long and unimaginably complex sequence of events stretching back 4.6billion years or so hadn’t played out in a particular manner at particular times if, to take justone obvious instance, the dinosaurs hadn’t been wiped out by a meteor when they were youmight well be six inches long, with whiskers and a tail, and reading this in a burrow. we don’t really know for sure because we have nothing else to compare our own existenceto, but it seems evident that if you wish to end up as a moderately advanced, thinking society,you need to be at the right end of a very long chain of outcomes involving reasonable periodsof stability interspersed with just the right amount of stress and challenge (ice ages appear tobe especially helpful in this regard) and marked by a total absence of real cataclysm. as weshall see in the pages that remain to us, we are very lucky to find ourselves in that position. and on that note, let us now turn briefly to the elements that made us. there are ninety two naturally occurring elements on earth, plus a further twenty or so thathave been created in labs, but some of these we can immediately put to one side as, in fact,chemists themselves tend to do. not a few of our earthly chemicals are surprisingly littleknown. astatine, for instance, is practically unstudied. it has a name and a place on theperiodic table (next door to marie curie’s polonium), but almost nothing else. the problem isn’t scientific indifference, but rarity. there just isn’t much astatine out there. the mostelusive element of all, however, appears to be francium, which is so rare that it is thought thatour entire planet may contain, at any given moment, fewer than twenty francium atoms.altogether only about thirty of the naturally occurring elements are widespread on earth, andbarely half a dozen are of central importance to life. as you might expect, oxygen is our most abundant element, accounting for just under 50percent of the earth’s crust, but after that the relative abundances are often surprising. whowould guess, for instance, that silicon is the second most common element on earth or thattitanium is tenth? abundance has little to do with their familiarity or utility to us. many of themore obscure elements are actually more common than the better known ones. there is morecerium on earth than copper, more neodymium and lanthanum than cobalt or nitrogen. tinbarely makes it into the top fifty, eclipsed by such relative obscurities as praseodymium,samarium, gadolinium, and dysprosium. abundance also has little to do with ease of detection. aluminum is the fourth mostcommon element on earth, accounting for nearly a tenth of everything that’s underneath yourfeet, but its existence wasn’t even suspected until it was discovered in the nineteenth centuryby humphry davy, and for a long time after that it was treated as rare and precious. congressnearly put a shiny lining of aluminum foil atop the washington monument to show what aclassy and prosperous nation we had become, and the french imperial family in the sameperiod discarded the state silver dinner service and replaced it with an aluminum one. thefashion was cutting edge even if the knives weren’t. nor does abundance necessarily relate to importance. carbon is only the fifteenth mostcommon element, accounting for a very modest 0.048 percent of earth’s crust, but we wouldbe lost without it. what sets the carbon atom apart is that it is shamelessly promiscuous. it isthe party animal of the atomic world, latching on to many other atoms (including itself) andholding tight, forming molecular conga lines of hearty robustness the very trick of naturenecessary to build proteins and dna. as paul davies has written: “if it wasn’t for carbon, lifeas we know it would be impossible. probably any sort of life would be impossible.” yetcarbon is not all that plentiful even in humans, who so vitally depend on it. of every 200atoms in your body, 126 are hydrogen, 51 are oxygen, and just 19 are carbon.2 other elements are critical not for creating life but for sustaining it. we need iron tomanufacture hemoglobin, and without it we would die. cobalt is necessary for the creation ofvitamin b12. potassium and a very little sodium are literally good for your nerves.molybdenum, manganese, and vanadium help to keep your enzymes purring. zinc bless it oxidizes alcohol. we have evolved to utilize or tolerate these things we could hardly be here otherwise but even then we live within narrow ranges of acceptance. selenium is vital to all of us, buttake in just a little too much and it will be the last thing you ever do. the degree to whichorganisms require or tolerate certain elements is a relic of their evolution. sheep and cattlenow graze side by side, but actually have very different mineral requirements. modern cattleneed quite a lot of copper because they evolved in parts of europe and africa where copperwas abundant. sheep, on the other hand, evolved in copper poor areas of asia minor. as arule, and not surprisingly, our tolerance for elements is directly proportionate to their2 of the remaining four, three are nitrogen and the remaining atom is divided among all the other elements. abundance in the earth’s crust. we have evolved to expect, and in some cases actually need,the tiny amounts of rare elements that accumulate in the flesh or fiber that we eat. but step upthe doses, in some cases by only a tiny amount, and we can soon cross a threshold. much ofthis is only imperfectly understood. no one knows, for example, whether a tiny amount ofarsenic is necessary for our well being or not. some authorities say it is; some not. all that iscertain is that too much of it will kill you. the properties of the elements can become more curious still when they are combined.oxygen and hydrogen, for instance, are two of the most combustion friendly elements around,but put them together and they make incombustible water.3 odder still in combination aresodium, one of the most unstable of all elements, and chlorine, one of the most toxic. drop asmall lump of pure sodium into ordinary water and it will explode with enough force to kill.chlorine is even more notoriously hazardous. though useful in small concentrations forkilling microorganisms (it’s chlorine you smell in bleach), in larger volumes it is lethal.chlorine was the element of choice for many of the poison gases of the first world war. and,as many a sore eyed swimmer will attest, even in exceedingly dilute form the human bodydoesn’t appreciate it. yet put these two nasty elements together and what do you get? sodiumchloride common table salt. by and large, if an element doesn’t naturally find its way into our systems if it isn’tsoluble in water, say we tend to be intolerant of it. lead poisons us because we were neverexposed to it until we began to fashion it into food vessels and pipes for plumbing. (notincidentally, lead’s symbol is pb, for the latin plumbum, the source word for our modernplumbing.) the romans also flavored their wine with lead, which may be part of the reasonthey are not the force they used to be. as we have seen elsewhere, our own performance withlead (not to mention mercury, cadmium, and all the other industrial pollutants with which weroutinely dose ourselves) does not leave us a great deal of room for smirking. when elementsdon’t occur naturally on earth, we have evolved no tolerance for them, and so they tend to beextremely toxic to us, as with plutonium. our tolerance for plutonium is zero: there is no levelat which it is not going to make you want to lie down. i have brought you a long way to make a small point: a big part of the reason that earthseems so miraculously accommodating is that we evolved to suit its conditions. what wemarvel at is not that it is suitable to life but that it is suitable to our life and hardlysurprising, really. it may be that many of the things that make it so splendid to us well proportioned sun, doting moon, sociable carbon, more magma than you can shake a stick at,and all the rest seem splendid simply because they are what we were born to count on. noone can altogether say. other worlds may harbor beings thankful for their silvery lakes of mercury and driftingclouds of ammonia. they may be delighted that their planet doesn’t shake them silly with itsgrinding plates or spew messy gobs of lava over the landscape, but rather exists in apermanent nontectonic tranquility. any visitors to earth from afar would almost certainly, atthe very least, be bemused to find us living in an atmosphere composed of nitrogen, a gassulkily disinclined to react with anything, and oxygen, which is so partial to combustion thatwe must place fire stations throughout our cities to protect ourselves from its livelier effects.but even if our visitors were oxygen breathing bipeds with shopping malls and a fondness for3 oxygen itself is not combustible; it merely facilitates the combus tion of other things. this is just as well, for ifoxygen were corn bustible, each time you lit a match all the air around you would bur into flame. hydrogen gas,on the other hand, is extremely corn bustible, as the dirigible hindenburg demonstrated on may 6, 193 inlakehurst, new jersey, when its hydrogen fuel burst explosive) into flame, killing thirty six people. action movies, it is unlikely that they would find earth ideal. we couldn’t even give themlunch because all our foods contain traces of manganese, selenium, zinc, and other elementalparticles at least some of which would be poisonous to them. to them earth might not seem awondrously congenial place at all. the physicist richard feynman used to make a joke about a posteriori conclusions, as theyare called. “you know, the most amazing thing happened to me tonight,” he would say. “isaw a car with the license plate arw 357. can you imagine? of all the millions of licenseplates in the state, what was the chance that i would see that particular one tonight?amazing!” his point, of course, was that it is easy to make any banal situation seemextraordinary if you treat it as fateful. so it is possible that the events and conditions that led to the rise of life on earth are notquite as extraordinary as we like to think. still, they were extraordinary enough, and one thingis certain: they will have to do until we find some better. 17 into the tropospherethank goodness for the atmosphere. it keeps us warm. without it, earth would be alifeless ball of ice with an average temperature of minus 60 degrees fahrenheit. in addition,the atmosphere absorbs or deflects incoming swarms of cosmic rays, charged particles,ultraviolet rays, and the like. altogether, the gaseous padding of the atmosphere is equivalentto a fifteen foot thickness of protective concrete, and without it these invisible visitors fromspace would slice through us like tiny daggers. even raindrops would pound us senseless if itweren’t for the atmosphere’s slowing drag. the most striking thing about our atmosphere is that there isn’t very much of it. it extendsupward for about 120 miles, which might seem reasonably bounteous when viewed fromground level, but if you shrank the earth to the size of a standard desktop globe it would onlybe about the thickness of a couple of coats of varnish. for scientific convenience, the atmosphere is divided into four unequal layers: troposphere,stratosphere, mesosphere, and ionosphere (now often called the thermosphere). thetroposphere is the part that’s dear to us. it alone contains enough warmth and oxygen to allowus to function, though even it swiftly becomes uncongenial to life as you climb up through it.from ground level to its highest point, the troposphere (or “turning sphere”) is about ten milesthick at the equator and no more than six or seven miles high in the temperate latitudes wheremost of us live. eighty percent of the atmosphere’s mass, virtually all the water, and thusvirtually all the weather are contained within this thin and wispy layer. there really isn’tmuch between you and oblivion. beyond the troposphere is the stratosphere. when you see the top of a storm cloudflattening out into the classic anvil shape, you are looking at the boundary between thetroposphere and stratosphere. this invisible ceiling is known as the tropopause and wasdiscovered in 1902 by a frenchman in a balloon, léon philippe teisserenc de bort. pause inthis sense doesn’t mean to stop momentarily but to cease altogether; it’s from the same greekroot as menopause. even at its greatest extent, the tropopause is not very distant. a fastelevator of the sort used in modern skyscrapers could get you there in about twenty minutes,though you would be well advised not to make the trip. such a rapid ascent withoutpressurization would, at the very least, result in severe cerebral and pulmonary edemas, adangerous excess of fluids in the body’s tissues. when the doors opened at the viewingplatform, anyone inside would almost certainly be dead or dying. even a more measuredascent would be accompanied by a great deal of discomfort. the temperature six miles up canbe  70 degrees fahrenheit, and you would need, or at least very much appreciate,supplementary oxygen. after you have left the troposphere the temperature soon warms up again, to about 40degrees fahrenheit, thanks to the absorptive effects of ozone (something else de bortdiscovered on his daring 1902 ascent). it then plunges to as low as  130 degrees fahrenheit inthe mesosphere before skyrocketing to 2,700 degrees fahrenheit or more in the aptly namedbut very erratic thermosphere, where temperatures can vary by a thousand degrees from day to night though it must be said that “temperature” at such a height becomes a somewhatnotional concept. temperature is really just a measure of the activity of molecules. at sealevel, air molecules are so thick that one molecule can move only the tiniest distance aboutthree millionths of an inch, to be precise before banging into another. because trillions ofmolecules are constantly colliding, a lot of heat gets exchanged. but at the height of thethermosphere, at fifty miles or more, the air is so thin that any two molecules will be milesapart and hardly ever come in contact. so although each molecule is very warm, there are fewinteractions between them and thus little heat transference. this is good news for satellitesand spaceships because if the exchange of heat were more efficient any man made objectorbiting at that level would burst into flame. even so, spaceships have to take care in the outer atmosphere, particularly on return trips toearth, as the space shuttle columbia demonstrated all too tragically in february 2003.although the atmosphere is very thin, if a craft comes in at too steep an angle more thanabout 6 degrees or too swiftly it can strike enough molecules to generate drag of anexceedingly combustible nature. conversely, if an incoming vehicle hit the thermosphere attoo shallow an angle, it could well bounce back into space, like a pebble skipped across water. but you needn’t venture to the edge of the atmosphere to be reminded of what hopelesslyground hugging beings we are. as anyone who has spent time in a lofty city will know, youdon’t have to rise too many thousands of feet from sea level before your body begins toprotest. even experienced mountaineers, with the benefits of fitness, training, and bottledoxygen, quickly become vulnerable at height to confusion, nausea, exhaustion, frostbite,hypothermia, migraine, loss of appetite, and a great many other stumbling dysfunctions. in ahundred emphatic ways the human body reminds its owner that it wasn’t designed to operateso far above sea level. “even under the most favorable circumstances,” the climber peter habeler has written ofconditions atop everest, “every step at that altitude demands a colossal effort of will. youmust force yourself to make every movement, reach for every handhold. you are perpetuallythreatened by a leaden, deadly fatigue.” in the other side of everest, the british mountaineerand filmmaker matt dickinson records how howard somervell, on a 1924 british expeditionup everest, “found himself choking to death after a piece of infected flesh came loose andblocked his windpipe.” with a supreme effort somervell managed to cough up theobstruction. it turned out to be “the entire mucus lining of his larynx.” bodily distress is notorious above 25,000 feet the area known to climbers as the deathzone but many people become severely debilitated, even dangerously ill, at heights of nomore than 15,000 feet or so. susceptibility has little to do with fitness. grannies sometimescaper about in lofty situations while their fitter offspring are reduced to helpless, groaningheaps until conveyed to lower altitudes. the absolute limit of human tolerance for continuous living appears to be about 5,500meters, or 18,000 feet, but even people conditioned to living at altitude could not tolerate suchheights for long. frances ashcroft, in life at the extremes, notes that there are andean sulfurmines at 5,800 meters, but that the miners prefer to descend 460 meters each evening andclimb back up the following day, rather than live continuously at that elevation. people whohabitually live at altitude have often spent thousands of years developing disproportionatelylarge chests and lungs, increasing their density of oxygen bearing red blood cells by almost athird, though there are limits to how much thickening with red cells the blood supply can stand. moreover, above 5,500 meters even the most well adapted women cannot provide agrowing fetus with enough oxygen to bring it to its full term. in the 1780s when people began to make experimental balloon ascents in europe,something that surprised them was how chilly it got as they rose. the temperature drops about3 degrees fahrenheit with every thousand feet you climb. logic would seem to indicate thatthe closer you get to a source of heat, the warmer you would feel. part of the explanation isthat you are not really getting nearer the sun in any meaningful sense. the sun is ninety threemillion miles away. to move a couple of thousand feet closer to it is like taking one stepcloser to a bushfire in australia when you are standing in ohio, and expecting to smell smoke.the answer again takes us back to the question of the density of molecules in the atmosphere.sunlight energizes atoms. it increases the rate at which they jiggle and jounce, and in theirenlivened state they crash into one another, releasing heat. when you feel the sun warm onyour back on a summer’s day, it’s really excited atoms you feel. the higher you climb, thefewer molecules there are, and so the fewer collisions between them. air is deceptive stuff. even at sea level, we tend to think of the air as being ethereal and allbut weightless. in fact, it has plenty of bulk, and that bulk often exerts itself. as a marinescientist named wyville thomson wrote more than a century ago: “we sometimes find whenwe get up in the morning, by a rise of an inch in the barometer, that nearly half a ton has beenquietly piled upon us during the night, but we experience no inconvenience, rather a feeling ofexhilaration and buoyancy, since it requires a little less exertion to move our bodies in thedenser medium.” the reason you don’t feel crushed under that extra half ton of pressure is thesame reason your body would not be crushed deep beneath the sea: it is made mostly ofincompressible fluids, which push back, equalizing the pressures within and without. but get air in motion, as with a hurricane or even a stiff breeze, and you will quickly bereminded that it has very considerable mass. altogether there are about 5,200 million milliontons of air around us 25 million tons for every square mile of the planet a notinconsequential volume. when you get millions of tons of atmosphere rushing past at thirty orforty miles an hour, it’s hardly a surprise that limbs snap and roof tiles go flying. as anthonysmith notes, a typical weather front may consist of 750 million tons of cold air pinnedbeneath a billion tons of warmer air. hardly a wonder that the result is at timesmeteorologically exciting. certainly there is no shortage of energy in the world above our heads. one thunderstorm, ithas been calculated, can contain an amount of energy equivalent to four days’ use ofelectricity for the whole united states. in the right conditions, storm clouds can rise to heightsof six to ten miles and contain updrafts and downdrafts of one hundred miles an hour. theseare often side by side, which is why pilots don’t want to fly through them. in all, the internalturmoil particles within the cloud pick up electrical charges. for reasons not entirelyunderstood the lighter particles tend to become positively charged and to be wafted by aircurrents to the top of the cloud. the heavier particles linger at the base, accumulating negativecharges. these negatively charged particles have a powerful urge to rush to the positivelycharged earth, and good luck to anything that gets in their way. a bolt of lightning travels at270,000 miles an hour and can heat the air around it to a decidedly crisp 50,000 degreesfahrenheit, several times hotter than the surface of the sun. at any one moment 1,800thunderstorms are in progress around the globe some 40,000 a day. day and night across theplanet every second about a hundred lightning bolts hit the ground. the sky is a lively place. much of our knowledge of what goes on up there is surprisingly recent. jet streams, usuallylocated about 30,000 to 35,000 feet up, can bowl along at up to 180 miles an hour and vastlyinfluence weather systems over whole continents, yet their existence wasn’t suspected untilpilots began to fly into them during the second world war. even now a great deal ofatmospheric phenomena is barely understood. a form of wave motion popularly known asclear air turbulence occasionally enlivens airplane flights. about twenty such incidents a yearare serious enough to need reporting. they are not associated with cloud structures oranything else that can be detected visually or by radar. they are just pockets of startlingturbulence in the middle of tranquil skies. in a typical incident, a plane en route fromsingapore to sydney was flying over central australia in calm conditions when it suddenlyfell three hundred feet enough to fling unsecured people against the ceiling. twelve peoplewere injured, one seriously. no one knows what causes such disruptive cells of air. the process that moves air around in the atmosphere is the same process that drives theinternal engine of the planet, namely convection. moist, warm air from the equatorial regionsrises until it hits the barrier of the tropopause and spreads out. as it travels away from theequator and cools, it sinks. when it hits bottom, some of the sinking air looks for an area oflow pressure to fill and heads back for the equator, completing the circuit. at the equator the convection process is generally stable and the weather predictably fair,but in temperate zones the patterns are far more seasonal, localized, and random, whichresults in an endless battle between systems of high pressure air and low. low pressuresystems are created by rising air, which conveys water molecules into the sky, forming cloudsand eventually rain. warm air can hold more moisture than cool air, which is why tropical andsummer storms tend to be the heaviest. thus low areas tend to be associated with clouds andrain, and highs generally spell sunshine and fair weather. when two such systems meet, itoften becomes manifest in the clouds. for instance, stratus clouds those unlovable,featureless sprawls that give us our overcast skies happen when moisture bearing updraftslack the oomph to break through a level of more stable air above, and instead spread out, likesmoke hitting a ceiling. indeed, if you watch a smoker sometime, you can get a very goodidea of how things work by watching how smoke rises from a cigarette in a still room. atfirst, it goes straight up (this is called a laminar flow, if you need to impress anyone), and thenit spreads out in a diffused, wavy layer. the greatest supercomputer in the world, takingmeasurements in the most carefully controlled environment, cannot tell you what forms theseripplings will take, so you can imagine the difficulties that confront meteorologists when theytry to predict such motions in a spinning, windy, large scale world. what we do know is that because heat from the sun is unevenly distributed, differences inair pressure arise on the planet. air can’t abide this, so it rushes around trying to equalizethings everywhere. wind is simply the air’s way of trying to keep things in balance. airalways flows from areas of high pressure to areas of low pressure (as you would expect; thinkof anything with air under pressure a balloon or an air tank and think how insistently thatpressured air wants to get someplace else), and the greater the discrepancy in pressures thefaster the wind blows. incidentally, wind speeds, like most things that accumulate, grow exponentially, so a windblowing at two hundred miles an hour is not simply ten times stronger than a wind blowing attwenty miles an hour, but a hundred times stronger and hence that much more destructive.introduce several million tons of air to this accelerator effect and the result can be exceedingly energetic. a tropical hurricane can release in twenty four hours as much energy as a rich,medium sized nation like britain or france uses in a year. the impulse of the atmosphere to seek equilibrium was first suspected by edmondhalley the man who was everywhere and elaborated upon in the eighteenth century by hisfellow briton george hadley, who saw that rising and falling columns of air tended toproduce “cells” (known ever since as “hadley cells”). though a lawyer by profession, hadleyhad a keen interest in the weather (he was, after all, english) and also suggested a linkbetween his cells, the earth’s spin, and the apparent deflections of air that give us our tradewinds. however, it was an engineering professor at the école polytechnique in paris,gustave gaspard de coriolis, who worked out the details of these interactions in 1835, andthus we call it the coriolis effect. (coriolis’s other distinction at the school was to introducewatercoolers, which are still known there as corios, apparently.) the earth revolves at a brisk1,041 miles an hour at the equator, though as you move toward the poles the rate slopes offconsiderably, to about 600 miles an hour in london or paris, for instance. the reason for thisis self evident when you think about it. if you are on the equator the spinning earth has tocarry you quite a distance about 40,000 kilometers to get you back to the same spot. if youstand beside the north pole, however, you may need travel only a few feet to complete arevolution, yet in both cases it takes twenty four hours to get you back to where you began.therefore, it follows that the closer you get to the equator the faster you must be spinning. the coriolis effect explains why anything moving through the air in a straight line laterallyto the earth’s spin will, given enough distance, seem to curve to the right in the northernhemisphere and to the left in the southern as the earth revolves beneath it. the standard wayto envision this is to imagine yourself at the center of a large carousel and tossing a ball tosomeone positioned on the edge. by the time the ball gets to the perimeter, the target personhas moved on and the ball passes behind him. from his perspective, it looks as if it has curvedaway from him. that is the coriolis effect, and it is what gives weather systems their curl andsends hurricanes spinning off like tops. the coriolis effect is also why naval guns firingartillery shells have to adjust to left or right; a shell fired fifteen miles would otherwisedeviate by about a hundred yards and plop harmlessly into the sea. considering the practical and psychological importance of the weather to nearly everyone,it’s surprising that meteorology didn’t really get going as a science until shortly before theturn of the nineteenth century (though the term meteorology itself had been around since1626, when it was coined by a t. granger in a book of logic). part of the problem was that successful meteorology requires the precise measurement oftemperatures, and thermometers for a long time proved more difficult to make than you mightexpect. an accurate reading was dependent on getting a very even bore in a glass tube, andthat wasn’t easy to do. the first person to crack the problem was daniel gabriel fahrenheit, adutch maker of instruments, who produced an accurate thermometer in 1717. however, forreasons unknown he calibrated the instrument in a way that put freezing at 32 degrees andboiling at 212 degrees. from the outset this numeric eccentricity bothered some people, and in1742 anders celsius, a swedish astronomer, came up with a competing scale. in proof of theproposition that inventors seldom get matters entirely right, celsius made boiling point zeroand freezing point 100 on his scale, but that was soon reversed. the person most frequently identified as the father of modern meteorology was an englishpharmacist named luke howard, who came to prominence at the beginning of the nineteenthcentury. howard is chiefly remembered now for giving cloud types their names in 1803.although he was an active and respected member of the linnaean society and employedlinnaean principles in his new scheme, howard chose the rather more obscure askesiansociety as the forum to announce his new system of classification. (the askesian society,you may just recall from an earlier chapter, was the body whose members were unusuallydevoted to the pleasures of nitrous oxide, so we can only hope they treated howard’spresentation with the sober attention it deserved. it is a point on which howard scholars arecuriously silent.) howard divided clouds into three groups: stratus for the layered clouds, cumulus for thefluffy ones (the word means “heaped” in latin), and cirrus (meaning “curled”) for the high,thin feathery formations that generally presage colder weather. to these he subsequentlyadded a fourth term, nimbus (from the latin for “cloud”), for a rain cloud. the beauty ofhoward’s system was that the basic components could be freely recombined to describe everyshape and size of passing cloud stratocumulus, cirrostratus, cumulocongestus, and so on. itwas an immediate hit, and not just in england. the poet johann von goethe in germany wasso taken with the system that he dedicated four poems to howard. howard’s system has been much added to over the years, so much so that the encyclopedicif little read international cloud atlas runs to two volumes, but interestingly virtually all thepost howard cloud types mammatus, pileus, nebulosis, spissatus, floccus, and mediocris area sampling have never caught on with anyone outside meteorology and not terribly muchthere, i’m told. incidentally, the first, much thinner edition of that atlas, produced in 1896,divided clouds into ten basic types, of which the plumpest and most cushiony looking wasnumber nine, cumulonimbus.1 that seems to have been the source of the expression “to be oncloud nine.” for all the heft and fury of the occasional anvil headed storm cloud, the average cloud isactually a benign and surprisingly insubstantial thing. a fluffy summer cumulus severalhundred yards to a side may contain no more than twenty five or thirty gallons of water “about enough to fill a bathtub,” as james trefil has noted. you can get some sense of theimmaterial quality of clouds by strolling through fog which is, after all, nothing more than acloud that lacks the will to fly. to quote trefil again: “if you walk 100 yards through a typicalfog, you will come into contact with only about half a cubic inch of water not enough togive you a decent drink.” in consequence, clouds are not great reservoirs of water. only about0.035 percent of the earth’s fresh water is floating around above us at any moment. depending on where it falls, the prognosis for a water molecule varies widely. if it lands infertile soil it will be soaked up by plants or reevaporated directly within hours or days. if itfinds its way down to the groundwater, however, it may not see sunlight again for manyyears thousands if it gets really deep. when you look at a lake, you are looking at acollection of molecules that have been there on average for about a decade. in the ocean theresidence time is thought to be more like a hundred years. altogether about 60 percent of1 if you have ever been struck by how beautifully crisp and well defined the edges of cumulus clouds tend to be,while other clouds are more blurry, the explanation is that in a cumulus cloud there is a pronounced boundarybetween the moist interior of the cloud and the dry air beyond it. any water molecule that strays beyond the edgeof the cloud is immediately zapped by the dry air beyond, allowing the cloud to keep its fine edge. much highercirrus clouds are composed of ice, and the zone between the edge of the cloud and the air beyond is not soclearly delineated, which is why they tend to be blurry at the edges. water molecules in a rainfall are returned to the atmosphere within a day or two. onceevaporated, they spend no more than a week or so drury says twelve days in the skybefore falling again as rain. evaporation is a swift process, as you can easily gauge by the fate of a puddle on asummer’s day. even something as large as the mediterranean would dry out in a thousandyears if it were not continually replenished. such an event occurred a little under six millionyears ago and provoked what is known to science as the messinian salinity crisis. whathappened was that continental movement closed the strait of gibraltar. as the mediterraneandried, its evaporated contents fell as freshwater rain into other seas, mildly diluting theirsaltiness indeed, making them just dilute enough to freeze over larger areas than normal.the enlarged area of ice bounced back more of the sun’s heat and pushed earth into an iceage. so at least the theory goes. what is certainly true, as far as we can tell, is that a little change in the earth’s dynamicscan have repercussions beyond our imagining. such an event, as we shall see a little furtheron, may even have created us. oceans are the real powerhouse of the planet’s surface behavior. indeed, meteorologistsincreasingly treat oceans and atmosphere as a single system, which is why we must give thema little of our attention here. water is marvelous at holding and transporting heat. every day,the gulf stream carries an amount of heat to europe equivalent to the world’s output of coalfor ten years, which is why britain and ireland have such mild winters compared with canadaand russia. but water also warms slowly, which is why lakes and swimming pools are cold even on thehottest days. for that reason there tends to be a lag in the official, astronomical start of aseason and the actual feeling that that season has started. so spring may officially start in thenorthern hemisphere in march, but it doesn’t feel like it in most places until april at the veryearliest. the oceans are not one uniform mass of water. their differences in temperature, salinity,depth, density, and so on have huge effects on how they move heat around, which in turnaffects climate. the atlantic, for instance, is saltier than the pacific, and a good thing too. thesaltier water is the denser it is, and dense water sinks. without its extra burden of salt, theatlantic currents would proceed up to the arctic, warming the north pole but deprivingeurope of all that kindly warmth. the main agent of heat transfer on earth is what is knownas thermohaline circulation, which originates in slow, deep currents far below the surface aprocess first detected by the scientist adventurer count von rumford in 1797.2 what happensis that surface waters, as they get to the vicinity of europe, grow dense and sink to greatdepths and begin a slow trip back to the southern hemisphere. when they reach antarctica,they are caught up in the antarctic circumpolar current, where they are driven onward intothe pacific. the process is very slow it can take 1,500 years for water to travel from the2 the term means a number of things to different people, it appears. in november 2002, carl wunsch of mitpublished a report in science, \"what is the thermohaline circulation?,\" in which he noted that the expressionhas been used in leading journals to signify at least seven different phenomena (circulation at the abyssal level,circulation driven by differences in density or buoyancy, \"meridional overturning circulation of mass,\" and soon) though all have to do with ocean circulations and the transfer of heat, the cautiously vague and embracingsense in which i have employed it here. north atlantic to the mid pacific but the volumes of heat and water they move are veryconsiderable, and the influence on the climate is enormous. (as for the question of how anyone could possibly figure out how long it takes a drop ofwater to get from one ocean to another, the answer is that scientists can measure compoundsin the water like chlorofluorocarbons and work out how long it has been since they were lastin the air. by comparing a lot of measurements from different depths and locations they canreasonably chart the water’s movement.) thermohaline circulation not only moves heat around, but also helps to stir up nutrients asthe currents rise and fall, making greater volumes of the ocean habitable for fish and othermarine creatures. unfortunately, it appears the circulation may also be very sensitive tochange. according to computer simulations, even a modest dilution of the ocean’s saltcontent from increased melting of the greenland ice sheet, for instance could disrupt thecycle disastrously. the seas do one other great favor for us. they soak up tremendous volumes of carbon andprovide a means for it to be safely locked away. one of the oddities of our solar system is thatthe sun burns about 25 percent more brightly now than when the solar system was young.this should have resulted in a much warmer earth. indeed, as the english geologist aubreymanning has put it, “this colossal change should have had an absolutely catastrophic effecton the earth and yet it appears that our world has hardly been affected.” so what keeps the world stable and cool? life does. trillions upon trillions of tiny marine organisms that most of us have neverheard of foraminiferans and coccoliths and calcareous algae capture atmospheric carbon,in the form of carbon dioxide, when it falls as rain and use it (in combination with otherthings) to make their tiny shells. by locking the carbon up in their shells, they keep it frombeing reevaporated into the atmosphere, where it would build up dangerously as a greenhousegas. eventually all the tiny foraminiferans and coccoliths and so on die and fall to the bottomof the sea, where they are compressed into limestone. it is remarkable, when you behold anextraordinary natural feature like the white cliffs of dover in england, to reflect that it ismade up of nothing but tiny deceased marine organisms, but even more remarkable when yourealize how much carbon they cumulatively sequester. a six inch cube of dover chalk willcontain well over a thousand liters of compressed carbon dioxide that would otherwise bedoing us no good at all. altogether there is about twenty thousand times as much carbonlocked away in the earth’s rocks as in the atmosphere. eventually much of that limestone willend up feeding volcanoes, and the carbon will return to the atmosphere and fall to the earth inrain, which is why the whole is called the long term carbon cycle. the process takes a verylong time about half a million years for a typical carbon atom but in the absence of anyother disturbance it works remarkably well at keeping the climate stable. unfortunately, human beings have a careless predilection for disrupting this cycle byputting lots of extra carbon into the atmosphere whether the foraminiferans are ready for it ornot. since 1850, it has been estimated, we have lofted about a hundred billion tons of extracarbon into the air, a total that increases by about seven billion tons each year. overall, that’snot actually all that much. nature mostly through the belchings of volcanoes and the decayof plants sends about 200 billion tons of carbon dioxide into the atmosphere each year,nearly thirty times as much as we do with our cars and factories. but you have only to look atthe haze that hangs over our cities to see what a difference our contribution makes. we know from samples of very old ice that the “natural” level of carbon dioxide in theatmosphere that is, before we started inflating it with industrial activity is about 280 partsper million. by 1958, when people in lab coats started to pay attention to it, it had risen to 315parts per million. today it is over 360 parts per million and rising by roughly one quarter of 1percent a year. by the end of the twenty first century it is forecast to rise to about 560 partsper million. so far, the earth’s oceans and forests (which also pack away a lot of carbon) have managedto save us from ourselves, but as peter cox of the british meteorological office puts it:“there is a critical threshold where the natural biosphere stops buffering us from the effects ofour emissions and actually starts to amplify them.” the fear is that there would be a runawayincrease in the earth’s warming. unable to adapt, many trees and other plants would die,releasing their stores of carbon and adding to the problem. such cycles have occasionallyhappened in the distant past even without a human contribution. the good news is that evenhere nature is quite wonderful. it is almost certain that eventually the carbon cycle wouldreassert itself and return the earth to a situation of stability and happiness. the last time thishappened, it took a mere sixty thousand years. 18 the bounding mainimagine trying to live in a world dominated by dihydrogen oxide, a compound that hasno taste or smell and is so variable in its properties that it is generally benign but at othertimes swiftly lethal. depending on its state, it can scald you or freeze you. in the presence ofcertain organic molecules it can form carbonic acids so nasty that they can strip the leavesfrom trees and eat the faces off statuary. in bulk, when agitated, it can strike with a fury thatno human edifice could withstand. even for those who have learned to live with it, it is anoften murderous substance. we call it water. water is everywhere. a potato is 80 percent water, a cow 74 percent, a bacterium 75percent. a tomato, at 95 percent, is little but water. even humans are 65 percent water,making us more liquid than solid by a margin of almost two to one. water is strange stuff. it isformless and transparent, and yet we long to be beside it. it has no taste and yet we love thetaste of it. we will travel great distances and pay small fortunes to see it in sunshine. andeven though we know it is dangerous and drowns tens of thousands of people every year, wecan’t wait to frolic in it. because water is so ubiquitous we tend to overlook what an extraordinary substance it is.almost nothing about it can be used to make reliable predictions about the properties of otherliquids and vice versa. if you knew nothing of water and based your assumptions on thebehavior of compounds most chemically akin to it hydrogen selenide or hydrogen sulphidenotably you would expect it to boil at minus 135 degrees fahrenheit and to be a gas at roomtemperature. most liquids when chilled contract by about 10 percent. water does too, but only down to apoint. once it is within whispering distance of freezing, it begins perversely, beguilingly,extremely improbably to expand. by the time it is solid, it is almost a tenth morevoluminous than it was before. because it expands, ice floats on water “an utterly bizarreproperty,” according to john gribbin. if it lacked this splendid waywardness, ice would sink,and lakes and oceans would freeze from the bottom up. without surface ice to hold heat in,the water’s warmth would radiate away, leaving it even chillier and creating yet more ice.soon even the oceans would freeze and almost certainly stay that way for a very long time,probably forever hardly the conditions to nurture life. thankfully for us, water seemsunaware of the rules of chemistry or laws of physics. everyone knows that water’s chemical formula is h2o, which means that it consists of onelargish oxygen atom with two smaller hydrogen atoms attached to it. the hydrogen atomscling fiercely to their oxygen host, but also make casual bonds with other water molecules.the nature of a water molecule means that it engages in a kind of dance with other watermolecules, briefly pairing and then moving on, like the ever changing partners in a quadrille,to use robert kunzig’s nice phrase. a glass of water may not appear terribly lively, but everymolecule in it is changing partners billions of times a second. that’s why water moleculesstick together to form bodies like puddles and lakes, but not so tightly that they can’t be easily separated as when, for instance, you dive into a pool of them. at any given moment only 15percent of them are actually touching. in one sense the bond is very strong it is why water molecules can flow uphill whensiphoned and why water droplets on a car hood show such a singular determination to beadwith their partners. it is also why water has surface tension. the molecules at the surface areattracted more powerfully to the like molecules beneath and beside them than to the airmolecules above. this creates a sort of membrane strong enough to support insects andskipping stones. it is what gives the sting to a belly flop. i hardly need point out that we would be lost without it. deprived of water, the human bodyrapidly falls apart. within days, the lips vanish “as if amputated, the gums blacken, the nosewithers to half its length, and the skin so contracts around the eyes as to prevent blinking.”water is so vital to us that it is easy to overlook that all but the smallest fraction of the wateron earth is poisonous to us deadly poisonous because of the salts within it. we need salt to live, but only in very small amounts, and seawater contains way more about seventy times more salt than we can safely metabolize. a typical liter of seawater willcontain only about 2.5 teaspoons of common salt the kind we sprinkle on food but muchlarger amounts of other elements, compounds, and other dissolved solids, which arecollectively known as salts. the proportions of these salts and minerals in our tissues isuncannily similar to seawater we sweat and cry seawater, as margulis and sagan have putit but curiously we cannot tolerate them as an input. take a lot of salt into your body andyour metabolism very quickly goes into crisis. from every cell, water molecules rush off likeso many volunteer firemen to try to dilute and carry off the sudden intake of salt. this leavesthe cells dangerously short of the water they need to carry out their normal functions. theybecome, in a word, dehydrated. in extreme situations, dehydration will lead to seizures,unconsciousness, and brain damage. meanwhile, the overworked blood cells carry the salt tothe kidneys, which eventually become overwhelmed and shut down. without functioningkidneys you die. that is why we don’t drink seawater. there are 320 million cubic miles of water on earth and that is all we’re ever going to get.the system is closed: practically speaking, nothing can be added or subtracted. the water youdrink has been around doing its job since the earth was young. by 3.8 billion years ago, theoceans had (at least more or less) achieved their present volumes. the water realm is known as the hydrosphere and it is overwhelmingly oceanic. ninety seven percent of all the water on earth is in the seas, the greater part of it in the pacific, whichcovers half the planet and is bigger than all the landmasses put together. altogether thepacific holds just over half of all the ocean water (51.6 percent to be precise); the atlantic has23.6 percent and the indian ocean 21.2 percent, leaving just 3.6 percent to be accounted forby all the other seas. the average depth of the ocean is 2.4 miles, with the pacific on averageabout a thousand feet deeper than the atlantic and indian oceans. altogether 60 percent ofthe planet’s surface is ocean more than a mile deep. as philip ball notes, we would better callour planet not earth but water. of the 3 percent of earth’s water that is fresh, most exists as ice sheets. only the tiniestamount 0.036 percent is found in lakes, rivers, and reservoirs, and an even smaller part just 0.001 percent exists in clouds or as vapor. nearly 90 percent of the planet’s ice is inantarctica, and most of the rest is in greenland. go to the south pole and you will bestanding on nearly two miles of ice, at the north pole just fifteen feet of it. antarctica alone has six million cubic miles of ice enough to raise the oceans by a height of two hundred feetif it all melted. but if all the water in the atmosphere fell as rain, evenly everywhere, theoceans would deepen by only an inch. sea level, incidentally, is an almost entirely notional concept. seas are not level at all.tides, winds, the coriolis force, and other effects alter water levels considerably from oneocean to another and within oceans as well. the pacific is about a foot and a half higher alongits western edge a consequence of the centrifugal force created by the earth’s spin. just aswhen you pull on a tub of water the water tends to flow toward the other end, as if reluctant tocome with you, so the eastward spin of earth piles water up against the ocean’s westernmargins. considering the age old importance of the seas to us, it is striking how long it took theworld to take a scientific interest in them. until well into the nineteenth century most of whatwas known about the oceans was based on what washed ashore or came up in fishing nets,and nearly all that was written was based more on anecdote and supposition than on physicalevidence. in the 1830s, the british naturalist edward forbes surveyed ocean beds throughoutthe atlantic and mediterranean and declared that there was no life at all in the seas below2,000 feet. it seemed a reasonable assumption. there was no light at that depth, so no plantlife, and the pressures of water at such depths were known to be extreme. so it came assomething of a surprise when, in 1860, one of the first transatlantic telegraph cables washauled up for repairs from more than two miles down, and it was found to be thicklyencrusted with corals, clams, and other living detritus. the first really organized investigation of the seas didn’t come until 1872, when a jointexpedition between the british museum, the royal society, and the british government setforth from portsmouth on a former warship called hms challenger. for three and a halfyears they sailed the world, sampling waters, netting fish, and hauling a dredge throughsediments. it was evidently dreary work. out of a complement of 240 scientists and crew, onein four jumped ship and eight more died or went mad “driven to distraction by the mind numbing routine of years of dredging” in the words of the historian samantha weinberg. butthey sailed across almost 70,000 nautical miles of sea, collected over 4,700 new species ofmarine organisms, gathered enough information to create a fifty volume report (which tooknineteen years to put together), and gave the world the name of a new scientific discipline:oceanography. they also discovered, by means of depth measurements, that there appeared tobe submerged mountains in the mid atlantic, prompting some excited observers to speculatethat they had found the lost continent of atlantis. because the institutional world mostly ignored the seas, it fell to devoted and veryoccasional amateurs to tell us what was down there. modern deep water exploration beginswith charles william beebe and otis barton in 1930. although they were equal partners, themore colorful beebe has always received far more written attention. born in 1877 into a well to do family in new york city, beebe studied zoology at columbia university, then took ajob as a birdkeeper at the new york zoological society. tiring of that, he decided to adoptthe life of an adventurer and for the next quarter century traveled extensively through asiaand south america with a succession of attractive female assistants whose jobs wereinventively described as “historian and technicist” or “assistant in fish problems.” hesupported these endeavors with a succession of popular books with titles like edge of thejungle and jungle days, though he also produced some respectable books on wildlife andornithology. in the mid 1920s, on a trip to the galápagos islands, he discovered “the delights ofdangling,” as he described deep sea diving. soon afterward he teamed up with barton, whocame from an even wealthier family, had also attended columbia, and also longed foradventure. although beebe nearly always gets the credit, it was in fact barton who designedthe first bathysphere (from the greek word for “deep”) and funded the $12,000 cost of itsconstruction. it was a tiny and necessarily robust chamber, made of cast iron 1.5 inches thickand with two small portholes containing quartz blocks three inches thick. it held two men, butonly if they were prepared to become extremely well acquainted. even by the standards of theage, the technology was unsophisticated. the sphere had no maneuverability it simply hungon the end of a long cable and only the most primitive breathing system: to neutralize theirown carbon dioxide they set out open cans of soda lime, and to absorb moisture they opened asmall tub of calcium chloride, over which they sometimes waved palm fronds to encouragechemical reactions. but the nameless little bathysphere did the job it was intended to do. on the first dive, injune 1930 in the bahamas, barton and beebe set a world record by descending to 600 feet. by1934, they had pushed the record to 3,028 feet, where it would stay until after the war. bartonwas confident the device was safe to a depth of 4,500 feet, though the strain on every bolt andrivet was audibly evident with each fathom they descended. at any depth, it was brave andrisky work. at 3,000 feet, their little porthole was subjected to nineteen tons of pressure persquare inch. death at such a depth would have been instantaneous, as beebe never failed toobserve in his many books, articles, and radio broadcasts. their main concern, however, wasthat the shipboard winch, straining to hold on to a metal ball and two tons of steel cable,would snap and send the two men plunging to the seafloor. in such an event, nothing couldhave saved them. the one thing their descents didn’t produce was a great deal of worthwhile science.although they encountered many creatures that had not been seen before, the limits ofvisibility and the fact that neither of the intrepid aquanauts was a trained oceanographer meantthey often weren’t able to describe their findings in the kind of detail that real scientistscraved. the sphere didn’t carry an external light, merely a 250 watt bulb they could hold upto the window, but the water below five hundred feet was practically impenetrable anyway,and they were peering into it through three inches of quartz, so anything they hoped to viewwould have to be nearly as interested in them as they were in it. about all they could report, inconsequence, was that there were a lot of strange things down there. on one dive in 1934,beebe was startled to spy a giant serpent “more than twenty feet long and very wide.” itpassed too swiftly to be more than a shadow. whatever it was, nothing like it has been seenby anyone since. because of such vagueness their reports were generally ignored byacademics. after their record breaking descent of 1934, beebe lost interest in diving and moved on toother adventures, but barton persevered. to his credit, beebe always told anyone who askedthat barton was the real brains behind the enterprise, but barton seemed unable to step fromthe shadows. he, too, wrote thrilling accounts of their underwater adventures and even starredin a hollywood movie called titans of the deep, featuring a bathysphere and many excitingand largely fictionalized encounters with aggressive giant squid and the like. he evenadvertised camel cigarettes (“they don’t give me jittery nerves”). in 1948 he increased thedepth record by 50 percent, with a dive to 4,500 feet in the pacific ocean near california, butthe world seemed determined to overlook him. one newspaper reviewer of titans of the deepactually thought the star of the film was beebe. nowadays, barton is lucky to get a mention. at all events, he was about to be comprehensively eclipsed by a father and son team fromswitzerland, auguste and jacques piccard, who were designing a new type of probe called abathyscaphe (meaning “deep boat”). christened trieste, after the italian city in which it wasbuilt, the new device maneuvered independently, though it did little more than just go up anddown. on one of its first dives, in early 1954, it descended to below 13,287 feet, nearly threetimes barton’s record breaking dive of six years earlier. but deep sea dives required a greatdeal of costly support, and the piccards were gradually going broke. in 1958, they did a deal with the u.s. navy, which gave the navy ownership but left themin control. now flush with funds, the piccards rebuilt the vessel, giving it walls five inchesthick and shrinking the windows to just two inches in diameter little more than peepholes.but it was now strong enough to withstand truly enormous pressures, and in january 1960jacques piccard and lieutenant don walsh of the u.s. navy sank slowly to the bottom of theocean’s deepest canyon, the mariana trench, some 250 miles off guam in the western pacific(and discovered, not incidentally, by harry hess with his fathometer). it took just under fourhours to fall 35,820 feet, or almost seven miles. although the pressure at that depth wasnearly 17,000 pounds per square inch, they noticed with surprise that they disturbed a bottom dwelling flatfish just as they touched down. they had no facilities for taking photographs, sothere is no visual record of the event. after just twenty minutes at the world’s deepest point, they returned to the surface. it wasthe only occasion on which human beings have gone so deep. forty years later, the question that naturally occurs is: why has no one gone back since? tobegin with, further dives were vigorously opposed by vice admiral hyman g. rickover, aman who had a lively temperament, forceful views, and, most pertinently, control of thedepartmental checkbook. he thought underwater exploration a waste of resources and pointedout that the navy was not a research institute. the nation, moreover, was about to becomefully preoccupied with space travel and the quest to send a man to the moon, which madedeep sea investigations seem unimportant and rather old fashioned. but the decisiveconsideration was that the trieste descent didn’t actually achieve much. as a navy officialexplained years later: “we didn’t learn a hell of a lot from it, other than that we could do it.why do it again?” it was, in short, a long way to go to find a flatfish, and expensive too.repeating the exercise today, it has been estimated, would cost at least $100 million. when underwater researchers realized that the navy had no intention of pursuing apromised exploration program, there was a pained outcry. partly to placate its critics, thenavy provided funding for a more advanced submersible, to be operated by the woods holeoceanographic institution of massachusetts. called alvin, in somewhat contracted honor ofthe oceanographer allyn c. vine, it would be a fully maneuverable minisubmarine, though itwouldn’t go anywhere near as deep as the trieste. there was just one problem: the designerscouldn’t find anyone willing to build it. according to william j. broad in the universebelow: “no big company like general dynamics, which made submarines for the navy,wanted to take on a project disparaged by both the bureau of ships and admiral rickover, thegods of naval patronage.” eventually, not to say improbably, alvin was constructed bygeneral mills, the food company, at a factory where it made the machines to producebreakfast cereals. as for what else was down there, people really had very little idea. well into the 1950s, thebest maps available to oceanographers were overwhelmingly based on a little detail fromscattered surveys going back to 1929 grafted onto, essentially an ocean of guesswork. the navy had excellent charts with which to guide submarines through canyons and aroundguyots, but it didn’t wish such information to fall into soviet hands, so it kept its knowledgeclassified. academics therefore had to make do with sketchy and antiquated surveys or relyon hopeful surmise. even today our knowledge of the ocean floors remains remarkably lowresolution. if you look at the moon with a standard backyard telescope you will seesubstantial craters fracastorious, blancanus, zach, planck, and many others familiar to anylunar scientist that would be unknown if they were on our own ocean floors. we have bettermaps of mars than we do of our own seabeds. at the surface level, investigative techniques have also been a trifle ad hoc. in 1994, thirty four thousand ice hockey gloves were swept overboard from a korean cargo ship during astorm in the pacific. the gloves washed up all over, from vancouver to vietnam, helpingoceanographers to trace currents more accurately than they ever had before. today alvin is nearly forty years old, but it still remains america’s premier research vessel.there are still no submersibles that can go anywhere near the depth of the mariana trenchand only five, including alvin, that can reach the depths of the “abyssal plain” the deepocean floor that covers more than half the planet’s surface. a typical submersible costsabout $25,000 a day to operate, so they are hardly dropped into the water on a whim, still lessput to sea in the hope that they will randomly stumble on something of interest. it’s rather asif our firsthand experience of the surface world were based on the work of five guys exploringon garden tractors after dark. according to robert kunzig, humans may have scrutinized“perhaps a millionth or a billionth of the sea’s darkness. maybe less. maybe much less.” but oceanographers are nothing if not industrious, and they have made several importantdiscoveries with their limited resources including, in 1977, one of the most important andstartling biological discoveries of the twentieth century. in that year alvin found teemingcolonies of large organisms living on and around deep sea vents off the galápagos islands tube worms over ten feet long, clams a foot wide, shrimps and mussels in profusion,wriggling spaghetti worms. they all owed their existence to vast colonies of bacteria thatwere deriving their energy and sustenance from hydrogen sulfides compounds profoundlytoxic to surface creatures that were pouring steadily from the vents. it was a worldindependent of sunlight, oxygen, or anything else normally associated with life. this was aliving system based not on photosynthesis but on chemosynthesis, an arrangement thatbiologists would have dismissed as preposterous had anyone been imaginative enough tosuggest it. huge amounts of heat and energy flow from these vents. two dozen of them together willproduce as much energy as a large power station, and the range of temperatures around themis enormous. the temperature at the point of outflow can be as much as 760 degreesfahrenheit, while a few feet away the water may be only two or three degrees above freezing.a type of worm called an alvinellid was found living right on the margins, with the watertemperature 140 degrees warmer at its head than at its tail. before this it had been thought thatno complex organisms could survive in water warmer than about 130 degrees, and here wasone that was surviving warmer temperatures than that and extreme cold to boot. thediscovery transformed our understanding of the requirements for life. it also answered one of the great puzzles of oceanography something that many of usdidn’t realize was a puzzle namely, why the oceans don’t grow saltier with time. at the riskof stating the obvious, there is a lot of salt in the sea enough to bury every bit of land on theplanet to a depth of about five hundred feet. millions of gallons of fresh water evaporate from the ocean daily, leaving all their salts behind, so logically the seas ought to grow more saltywith the passing years, but they don’t. something takes an amount of salt out of the waterequivalent to the amount being put in. for the longest time, no one could figure out whatcould be responsible for this. alvin’s discovery of the deep sea vents provided the answer. geophysicists realized that thevents were acting much like the filters in a fish tank. as water is taken down into the crust,salts are stripped from it, and eventually clean water is blown out again through the chimneystacks. the process is not swift it can take up to ten million years to clean an ocean but itis marvelously efficient as long as you are not in a hurry. perhaps nothing speaks more clearly of our psychological remoteness from the oceandepths than that the main expressed goal for oceanographers during international geophysicalyear of 1957 58 was to study “the use of ocean depths for the dumping of radioactivewastes.” this wasn’t a secret assignment, you understand, but a proud public boast. in fact,though it wasn’t much publicized, by 1957 58 the dumping of radioactive wastes had alreadybeen going on, with a certain appalling vigor, for over a decade. since 1946, the united stateshad been ferrying fifty five gallon drums of radioactive gunk out to the farallon islands,some thirty miles off the california coast near san francisco, where it simply threw themoverboard. it was all quite extraordinarily sloppy. most of the drums were exactly the sort you seerusting behind gas stations or standing outside factories, with no protective linings of anytype. when they failed to sink, which was usually, navy gunners riddled them with bullets tolet water in (and, of course, plutonium, uranium, and strontium out). before it was halted inthe 1990s, the united states had dumped many hundreds of thousands of drums into aboutfifty ocean sites almost fifty thousand of them in the farallons alone. but the u.s. was by nomeans alone. among the other enthusiastic dumpers were russia, china, japan, new zealand,and nearly all the nations of europe. and what effect might all this have had on life beneath the seas? well, little, we hope, butwe actually have no idea. we are astoundingly, sumptuously, radiantly ignorant of lifebeneath the seas. even the most substantial ocean creatures are often remarkably little knownto us including the most mighty of them all, the great blue whale, a creature of suchleviathan proportions that (to quote david attenborough) its “tongue weighs as much as anelephant, its heart is the size of a car and some of its blood vessels are so wide that you couldswim down them.” it is the most gargantuan beast that earth has yet produced, bigger eventhan the most cumbrous dinosaurs. yet the lives of blue whales are largely a mystery to us.much of the time we have no idea where they are where they go to breed, for instance, orwhat routes they follow to get there. what little we know of them comes almost entirely fromeavesdropping on their songs, but even these are a mystery. blue whales will sometimes breakoff a song, then pick it up again at the same spot six months later. sometimes they strike upwith a new song, which no member can have heard before but which each already knows.how they do this is not remotely understood. and these are animals that must routinely cometo the surface to breathe. for animals that need never surface, obscurity can be even more tantalizing. consider thefabled giant squid. though nothing on the scale of the blue whale, it is a decidedly substantialanimal, with eyes the size of soccer balls and trailing tentacles that can reach lengths of sixty feet. it weighs nearly a ton and is earth’s largest invertebrate. if you dumped one in a normalhousehold swimming pool, there wouldn’t be much room for anything else. yet no scientist no person as far as we know has ever seen a giant squid alive. zoologists have devotedcareers to trying to capture, or just glimpse, living giant squid and have always failed. theyare known mostly from being washed up on beaches particularly, for unknown reasons, thebeaches of the south island of new zealand. they must exist in large numbers because theyform a central part of the sperm whale’s diet, and sperm whales take a lot of feeding.1 according to one estimate, there could be as many as thirty million species of animalsliving in the sea, most still undiscovered. the first hint of how abundant life is in the deepseas didn’t come until as recently as the 1960s with the invention of the epibenthic sled, adredging device that captures organisms not just on and near the seafloor but also buried inthe sediments beneath. in a single one hour trawl along the continental shelf, at a depth of justunder a mile, woods hole oceanographers howard sandler and robert hessler netted over25,000 creatures worms, starfish, sea cucumbers, and the like representing 365 species.even at a depth of three miles, they found some 3,700 creatures representing almost 200species of organism. but the dredge could only capture things that were too slow or stupid toget out of the way. in the late 1960s a marine biologist named john isaacs got the idea tolower a camera with bait attached to it, and found still more, in particular dense swarms ofwrithing hagfish, a primitive eel like creature, as well as darting shoals of grenadier fish.where a good food source is suddenly available for instance, when a whale dies and sinks tothe bottom as many as 390 species of marine creature have been found dining off it.interestingly, many of these creatures were found to have come from vents up to a thousandmiles distant. these included such types as mussels and clams, which are hardly known asgreat travelers. it is now thought that the larvae of certain organisms may drift through thewater until, by some unknown chemical means, they detect that they have arrived at a foodopportunity and fall onto it. so why, if the seas are so vast, do we so easily overtax them? well, to begin with, theworld’s seas are not uniformly bounteous. altogether less than a tenth of the ocean isconsidered naturally productive. most aquatic species like to be in shallow waters where thereis warmth and light and an abundance of organic matter to prime the food chain. coral reefs,for instance, constitute well under 1 percent of the ocean’s space but are home to about 25percent of its fish.elsewhere, the oceans aren’t nearly so rich. take australia. with over 20,000 miles ofcoastline and almost nine million square miles of territorial waters, it has more sea lapping itsshores than any other country, yet, as tim flannery notes, it doesn’t even make it into the topfifty among fishing nations. indeed, australia is a large net importer of seafood. this isbecause much of australia’s waters are, like much of australia itself, essentially desert. (anotable exception is the great barrier reef off queensland, which is sumptuously fecund.)because the soil is poor, it produces little in the way of nutrient rich runoff.even where life thrives, it is often extremely sensitive to disturbance. in the 1970s, fishermenfrom australia and, to a lesser extent, new zealand discovered shoals of a little known fishliving at a depth of about half a mile on their continental shelves. they were known as orange1 the indigestible parts of giant squid, in particular their beaks, accumulate in sperm whales' stomachs into thesubstance known as ambergris, which is used as a fixative in perfumes. the next time you spray on chanel no. 5(assuming you do), you may wish to reflect that you are dousing yourself in distillate of unseen sea monster. roughy, they were delicious, and they existed in huge numbers. in no time at all, fishing fleetswere hauling in forty thousand metric tons of roughy a year. then marine biologists madesome alarming discoveries. roughy are extremely long lived and slow maturing. some maybe 150 years old; any roughy you have eaten may well have been born when victoria wasqueen. roughy have adopted this exceedingly unhurried lifestyle because the waters they livein are so resource poor. in such waters, some fish spawn just once in a lifetime. clearly theseare populations that cannot stand a great deal of disturbance. unfortunately, by the time thiswas realized the stocks had been severely depleted. even with careful management it will bedecades before the populations recover, if they ever do. elsewhere, however, the misuse of the oceans has been more wanton than inadvertent.many fishermen “fin” sharks that is, slice their fins off, then dump them back into the waterto die. in 1998, shark fins sold in the far east for over $250 a pound. a bowl of shark finsoup retailed in tokyo for $100. the world wildlife fund estimated in 1994 that the numberof sharks killed each year was between 40 million and 70 million. as of 1995, some 37,000 industrial sized fishing ships, plus about a million smaller boats,were between them taking twice as many fish from the sea as they had just twenty five yearsearlier. trawlers are sometimes now as big as cruise ships and haul behind them nets bigenough to hold a dozen jumbo jets. some even use spotter planes to locate shoals of fish fromthe air. it is estimated that about a quarter of every fishing net hauled up contains “by catch” fishthat can’t be landed because they are too small or of the wrong type or caught in the wrongseason. as one observer told the economist: “we’re still in the dark ages. we just drop a netdown and see what comes up.” perhaps as much as twenty two million metric tons of suchunwanted fish are dumped back in the sea each year, mostly in the form of corpses. for everypound of shrimp harvested, about four pounds of fish and other marine creatures aredestroyed. large areas of the north sea floor are dragged clean by beam trawlers as many as seventimes a year, a degree of disturbance that no ecosystem can withstand. at least two thirds ofspecies in the north sea, by many estimates, are being overfished. across the atlantic thingsare no better. halibut once abounded in such numbers off new england that individual boatscould land twenty thousand pounds of it in a day. now halibut is all but extinct off thenortheast coast of north america. nothing, however, compares with the fate of cod. in the late fifteenth century, the explorerjohn cabot found cod in incredible numbers on the eastern banks of north america shallowareas of water popular with bottom feeding fish like cod. some of these banks were vast.georges banks off massachusetts is bigger than the state it abuts. the grand banks offnewfoundland is bigger still and for centuries was always dense with cod. they were thoughtto be inexhaustible. of course they were anything but. by 1960, the number of spawning cod in the north atlantic had fallen to an estimated 1.6million metric tons. by 1990 this had sunk to 22,000 metric tons. in commercial terms, thecod were extinct. “fishermen,” wrote mark kurlansky in his fascinating history, cod, “hadcaught them all.” the cod may have lost the western atlantic forever. in 1992, cod fishingwas stopped altogether on the grand banks, but as of last autumn, according to a report innature, stocks had not staged a comeback. kurlansky notes that the fish of fish fillets and fish sticks was originally cod, but then was replaced by haddock, then by redfish, and lately bypacific pollock. these days, he notes drily, “fish” is “whatever is left.” much the same can be said of many other seafoods. in the new england fisheries offrhode island, it was once routine to haul in lobsters weighing twenty pounds. sometimes theyreached thirty pounds. left unmolested, lobsters can live for decades as much as seventyyears, it is thought and they never stop growing. nowadays few lobsters weigh more thantwo pounds on capture. “biologists,” according to the new york times, “estimate that 90percent of lobsters are caught within a year after they reach the legal minimum size at aboutage six.” despite declining catches, new england fishermen continue to receive state andfederal tax incentives that encourage them in some cases all but compel them to acquirebigger boats and to harvest the seas more intensively. today fishermen of massachusetts arereduced to fishing the hideous hagfish, for which there is a slight market in the far east, buteven their numbers are now falling. we are remarkably ignorant of the dynamics that rule life in the sea. while marine life ispoorer than it ought to be in areas that have been overfished, in some naturally impoverishedwaters there is far more life than there ought to be. the southern oceans around antarcticaproduce only about 3 percent of the world’s phytoplankton far too little, it would seem, tosupport a complex ecosystem, and yet it does. crab eater seals are not a species of animal thatmost of us have heard of, but they may actually be the second most numerous large species ofanimal on earth, after humans. as many as fifteen million of them may live on the pack icearound antarctica. there are also perhaps two million weddel seals, at least half a millionemperor penguins, and maybe as many as four million adélie penguins. the food chain isthus hopelessly top heavy, but somehow it works. remarkably no one knows how. all this is a very roundabout way of making the point that we know very little about earth’sbiggest system. but then, as we shall see in the pages remaining to us, once you start talkingabout life, there is a great deal we don’t know, not least how it got going in the first place. 19 the rise of lifein 1953, stanley miller, a graduate student at the university of chicago, took twoflasks one containing a little water to represent a primeval ocean, the other holding amixture of methane, ammonia, and hydrogen sulphide gases to represent earth’s earlyatmosphere connected them with rubber tubes, and introduced some electrical sparks as astand in for lightning. after a few days, the water in the flasks had turned green and yellow ina hearty broth of amino acids, fatty acids, sugars, and other organic compounds. “if goddidn’t do it this way,” observed miller’s delighted supervisor, the nobel laureate haroldurey, “he missed a good bet.” press reports of the time made it sound as if about all that was needed now was forsomebody to give the whole a good shake and life would crawl out. as time has shown, itwasn’t nearly so simple. despite half a century of further study, we are no nearer tosynthesizing life today than we were in 1953 and much further away from thinking we can.scientists are now pretty certain that the early atmosphere was nothing like as primed fordevelopment as miller and urey’s gaseous stew, but rather was a much less reactive blend ofnitrogen and carbon dioxide. repeating miller’s experiments with these more challenginginputs has so far produced only one fairly primitive amino acid. at all events, creating aminoacids is not really the problem. the problem is proteins. proteins are what you get when you string amino acids together, and we need a lot of them.no one really knows, but there may be as many as a million types of protein in the humanbody, and each one is a little miracle. by all the laws of probability proteins shouldn’t exist.to make a protein you need to assemble amino acids (which i am obliged by long tradition torefer to here as “the building blocks of life”) in a particular order, in much the same way thatyou assemble letters in a particular order to spell a word. the problem is that words in theamino acid alphabet are often exceedingly long. to spell collagen, the name of a commontype of protein, you need to arrange eight letters in the right order. but to make collagen, youneed to arrange 1,055 amino acids in precisely the right sequence. but and here’s anobvious but crucial point you don’t make it. it makes itself, spontaneously, withoutdirection, and this is where the unlikelihoods come in. the chances of a 1,055 sequence molecule like collagen spontaneously self assembling are,frankly, nil. it just isn’t going to happen. to grasp what a long shot its existence is, visualize astandard las vegas slot machine but broadened greatly to about ninety feet, to be precise to accommodate 1,055 spinning wheels instead of the usual three or four, and with twentysymbols on each wheel (one for each common amino acid).1 how long would you have topull the handle before all 1,055 symbols came up in the right order? effectively forever. evenif you reduced the number of spinning wheels to two hundred, which is actually a moretypical number of amino acids for a protein, the odds against all two hundred coming up in a1 there are actually twenty two naturally occurring amino acids known on earth, and more may await discovery,but only twenty of them are necessary to produce us and most other living things. the twenty second, calledpyrrolysine, was discovered in 2002 by researchers at ohio state university and is found only in a single type ofarchaean (a basic form of life that we will discuss a little further on in the story) called methanosarcina barkeri. prescribed sequence are 1 in 10260(that is a 1 followed by 260 zeroes). that in itself is a largernumber than all the atoms in the universe. proteins, in short, are complex entities. hemoglobin is only 146 amino acids long, a runt byprotein standards, yet even it offers 10190possible amino acid combinations, which is why ittook the cambridge university chemist max perutz twenty three years a career, more orless to unravel it. for random events to produce even a single protein would seem astunning improbability like a whirlwind spinning through a junkyard and leaving behind afully assembled jumbo jet, in the colorful simile of the astronomer fred hoyle. yet we are talking about several hundred thousand types of protein, perhaps a million, eachunique and each, as far as we know, vital to the maintenance of a sound and happy you. andit goes on from there. a protein to be of use must not only assemble amino acids in the rightsequence, but then must engage in a kind of chemical origami and fold itself into a veryspecific shape. even having achieved this structural complexity, a protein is no good to you ifit can’t reproduce itself, and proteins can’t. for this you need dna. dna is a whiz atreplicating it can make a copy of itself in seconds but can do virtually nothing else. so wehave a paradoxical situation. proteins can’t exist without dna, and dna has no purposewithout proteins. are we to assume then that they arose simultaneously with the purpose ofsupporting each other? if so: wow. and there is more still. dna, proteins, and the other components of life couldn’t prosperwithout some sort of membrane to contain them. no atom or molecule has ever achieved lifeindependently. pluck any atom from your body, and it is no more alive than is a grain of sand.it is only when they come together within the nurturing refuge of a cell that these diversematerials can take part in the amazing dance that we call life. without the cell, they arenothing more than interesting chemicals. but without the chemicals, the cell has no purpose.as the physicist paul davies puts it, “if everything needs everything else, how did thecommunity of molecules ever arise in the first place?” it is rather as if all the ingredients inyour kitchen somehow got together and baked themselves into a cake but a cake that couldmoreover divide when necessary to produce more cakes. it is little wonder that we call it themiracle of life. it is also little wonder that we have barely begun to understand it. so what accounts for all this wondrous complexity? well, one possibility is that perhaps itisn’t quite not quite so wondrous as at first it seems. take those amazingly improbableproteins. the wonder we see in their assembly comes in assuming that they arrived on thescene fully formed. but what if the protein chains didn’t assemble all at once? what if, in thegreat slot machine of creation, some of the wheels could be held, as a gambler might hold anumber of promising cherries? what if, in other words, proteins didn’t suddenly burst intobeing, but evolved . imagine if you took all the components that make up a human being carbon, hydrogen,oxygen, and so on and put them in a container with some water, gave it a vigorous stir, andout stepped a completed person. that would be amazing. well, that’s essentially what hoyleand others (including many ardent creationists) argue when they suggest that proteinsspontaneously formed all at once. they didn’t they can’t have. as richard dawkins arguesin the blind watchmaker, there must have been some kind of cumulative selection processthat allowed amino acids to assemble in chunks. perhaps two or three amino acids linked up for some simple purpose and then after a time bumped into some other similar small clusterand in so doing “discovered” some additional improvement. chemical reactions of the sort associated with life are actually something of acommonplace. it may be beyond us to cook them up in a lab, à la stanley miller and haroldurey, but the universe does it readily enough. lots of molecules in nature get together to formlong chains called polymers. sugars constantly assemble to form starches. crystals can do anumber of lifelike things replicate, respond to environmental stimuli, take on a patternedcomplexity. they’ve never achieved life itself, of course, but they demonstrate repeatedly thatcomplexity is a natural, spontaneous, entirely commonplace event. there may or may not be agreat deal of life in the universe at large, but there is no shortage of ordered self assembly, ineverything from the transfixing symmetry of snowflakes to the comely rings of saturn. so powerful is this natural impulse to assemble that many scientists now believe that lifemay be more inevitable than we think that it is, in the words of the belgian biochemist andnobel laureate christian de duve, “an obligatory manifestation of matter, bound to arisewherever conditions are appropriate.” de duve thought it likely that such conditions would beencountered perhaps a million times in every galaxy. certainly there is nothing terribly exotic in the chemicals that animate us. if you wished tocreate another living object, whether a goldfish or a head of lettuce or a human being, youwould need really only four principal elements, carbon, hydrogen, oxygen, and nitrogen, plussmall amounts of a few others, principally sulfur, phosphorus, calcium, and iron. put thesetogether in three dozen or so combinations to form some sugars, acids, and other basiccompounds and you can build anything that lives. as dawkins notes: “there is nothingspecial about the substances from which living things are made. living things are collectionsof molecules, like everything else.” the bottom line is that life is amazing and gratifying, perhaps even miraculous, but hardlyimpossible as we repeatedly attest with our own modest existences. to be sure, many of thedetails of life’s beginnings remain pretty imponderable. every scenario you have ever readconcerning the conditions necessary for life involves water from the “warm little pond”where darwin supposed life began to the bubbling sea vents that are now the most popularcandidates for life’s beginnings but all this overlooks the fact that to turn monomers intopolymers (which is to say, to begin to create proteins) involves what is known to biology as“dehydration linkages.” as one leading biology text puts it, with perhaps just a tiny hint ofdiscomfort, “researchers agree that such reactions would not have been energeticallyfavorable in the primitive sea, or indeed in any aqueous medium, because of the mass actionlaw.” it is a little like putting sugar in a glass of water and having it become a cube. itshouldn’t happen, but somehow in nature it does. the actual chemistry of all this is a littlearcane for our purposes here, but it is enough to know that if you make monomers wet theydon’t turn into polymers except when creating life on earth. how and why it happens thenand not otherwise is one of biology’s great unanswered questions. one of the biggest surprises in the earth sciences in recent decades was the discovery ofjust how early in earth’s history life arose. well into the 1950s, it was thought that life wasless than 600 million years old. by the 1970s, a few adventurous souls felt that maybe it wentback 2.5 billion years. but the present date of 3.85 billion years is stunningly early. earth’ssurface didn’t become solid until about 3.9 billion years ago. “we can only infer from this rapidity that it is not ‘difficult’ for life of bacterial grade toevolve on planets with appropriate conditions,” stephen jay gould observed in the new yorktimes in 1996. or as he put it elsewhere, it is hard to avoid the conclusion that “life, arising assoon as it could, was chemically destined to be.” life emerged so swiftly, in fact, that some authorities think it must have had help perhapsa good deal of help. the idea that earthly life might have arrived from space has a surprisinglylong and even occasionally distinguished history. the great lord kelvin himself raised thepossibility as long ago as 1871 at a meeting of the british association for the advancement ofscience when he suggested that “the germs of life might have been brought to the earth bysome meteorite.” but it remained little more than a fringe notion until one sunday inseptember 1969 when tens of thousands of australians were startled by a series of sonicbooms and the sight of a fireball streaking from east to west across the sky. the fireball madea strange crackling sound as it passed and left behind a smell that some likened to methylatedspirits and others described as just awful. the fireball exploded above murchison, a town of six hundred people in the goulburnvalley north of melbourne, and came raining down in chunks, some weighing up to twelvepounds. fortunately, no one was hurt. the meteorite was of a rare type known as acarbonaceous chondrite, and the townspeople helpfully collected and brought in some twohundred pounds of it. the timing could hardly have been better. less than two months earlier,the apollo 11 astronauts had returned to earth with a bag full of lunar rocks, so labsthroughout the world were geared up indeed clamoring for rocks of extraterrestrial origin. the murchison meteorite was found to be 4.5 billion years old, and it was studded withamino acids seventy four types in all, eight of which are involved in the formation of earthlyproteins. in late 2001, more than thirty years after it crashed, a team at the ames researchcenter in california announced that the murchison rock also contained complex strings ofsugars called polyols, which had not been found off the earth before. a few other carbonaceous chondrites have strayed into earth’s path since one that landednear tagish lake in canada’s yukon in january 2000 was seen over large parts of northamerica and they have likewise confirmed that the universe is actually rich in organiccompounds. halley’s comet, it is now thought, is about 25 percent organic molecules. getenough of those crashing into a suitable place earth, for instance and you have the basicelements you need for life. there are two problems with notions of panspermia, as extraterrestrial theories are known.the first is that it doesn’t answer any questions about how life arose, but merely movesresponsibility for it elsewhere. the other is that panspermia sometimes excites even the mostrespectable adherents to levels of speculation that can be safely called imprudent. franciscrick, codiscoverer of the structure of dna, and his colleague leslie orgel have suggestedthat earth was “deliberately seeded with life by intelligent aliens,” an idea that gribbin calls“at the very fringe of scientific respectability” or, put another way, a notion that would beconsidered wildly lunatic if not voiced by a nobel laureate. fred hoyle and his colleaguechandra wickramasinghe further eroded enthusiasm for panspermia by suggesting that outerspace brought us not only life but also many diseases such as flu and bubonic plague, ideasthat were easily disproved by biochemists. hoyle and it seems necessary to insert areminder here that he was one of the great scientific minds of the twentieth century alsoonce suggested, as mentioned earlier, that our noses evolved with the nostrils underneath as away of keeping cosmic pathogens from falling into them as they drifted down from space. whatever prompted life to begin, it happened just once. that is the most extraordinary factin biology, perhaps the most extraordinary fact we know. everything that has ever lived, plantor animal, dates its beginnings from the same primordial twitch. at some point in anunimaginably distant past some little bag of chemicals fidgeted to life. it absorbed somenutrients, gently pulsed, had a brief existence. this much may have happened before, perhapsmany times. but this ancestral packet did something additional and extraordinary: it cleaveditself and produced an heir. a tiny bundle of genetic material passed from one living entity toanother, and has never stopped moving since. it was the moment of creation for us all.biologists sometimes call it the big birth. “wherever you go in the world, whatever animal, plant, bug, or blob you look at, if it isalive, it will use the same dictionary and know the same code. all life is one,” says mattridley. we are all the result of a single genetic trick handed down from generation togeneration nearly four billion years, to such an extent that you can take a fragment of humangenetic instruction, patch it into a faulty yeast cell, and the yeast cell will put it to work as if itwere its own. in a very real sense, it is its own. the dawn of life or something very like it sits on a shelf in the office of a friendlyisotope geochemist named victoria bennett in the earth sciences building of the australiannational university in canberra. an american, ms. bennett came to the anu fromcalifornia on a two year contract in 1989 and has been there ever since. when i visited her, inlate 2001, she handed me a modestly hefty hunk of rock composed of thin alternating stripesof white quartz and a gray green material called clinopyroxene. the rock came from akiliaisland in greenland, where unusually ancient rocks were found in 1997. the rocks are 3.85billion years old and represent the oldest marine sediments ever found. “we can’t be certain that what you are holding once contained living organisms becauseyou’d have to pulverize it to find out,” bennett told me. “but it comes from the same depositwhere the oldest life was excavated, so it probably had life in it.” nor would you find actualfossilized microbes, however carefully you searched. any simple organisms, alas, would havebeen baked away by the processes that turned ocean mud to stone. instead what we would seeif we crunched up the rock and examined it microscopically would be the chemical residuesthat the organisms left behind carbon isotopes and a type of phosphate called apatite, whichtogether provide strong evidence that the rock once contained colonies of living things. “wecan only guess what the organism might have looked like,” bennett said. “it was probablyabout as basic as life can get but it was life nonetheless. it lived. it propagated.” and eventually it led to us. if you are into very old rocks, and bennett indubitably is, the anu has long been a primeplace to be. this is largely thanks to the ingenuity of a man named bill compston, who isnow retired but in the 1970s built the world’s first sensitive high resolution ion microprobe or shrimp, as it is more affectionately known from its initial letters. this is amachine that measures the decay rate of uranium in tiny minerals called zircons. zirconsappear in most rocks apart from basalts and are extremely durable, surviving every naturalprocess but subduction. most of the earth’s crust has been slipped back into the oven at somepoint, but just occasionally in western australia and greenland, for example geologistshave found outcrops of rocks that have remained always at the surface. compston’s machineallowed such rocks to be dated with unparalleled precision. the prototype shrimp was built and machined in the earth science department’s own workshops, and looked like somethingthat had been built from spare parts on a budget, but it worked great. on its first formal test, in1982, it dated the oldest thing ever found a 4.3 billion year old rock from westernaustralia. “it caused quite a stir at the time,” bennett told me, “to find something so important soquickly with brand new technology.” she took me down the hall to see the current model, shrimp ii. it was a big heavy pieceof stainless steel apparatus, perhaps twelve feet long and five feet high, and as solidly built asa deep sea probe. at a console in front of it, keeping an eye on ever changing strings offigures on a screen, was a man named bob from canterbury university in new zealand. hehad been there since 4 a.m., he told me. shrimp ii runs twenty four hours a day; there’s thatmany rocks to date. it was just after 9a.m. and bob had the machine till noon. ask a pair ofgeochemists how something like this works, and they will start talking about isotopicabundances and ionization levels with an enthusiasm that is more endearing than fathomable.the upshot of it, however, was that the machine, by bombarding a sample of rock withstreams of charged atoms, is able to detect subtle differences in the amounts of lead anduranium in the zircon samples, by which means the age of rocks can be accurately adduced.bob told me that it takes about seventeen minutes to read one zircon and it is necessary toread dozens from each rock to make the data reliable. in practice, the process seemed toinvolve about the same level of scattered activity, and about as much stimulation, as a trip to alaundromat. bob seemed very happy, however; but then people from new zealand verygenerally do. the earth sciences compound was an odd combination of things part offices, part labs,part machine shed. “we used to build everything here,” bennett said. “we even had our ownglassblower, but he’s retired. but we still have two full time rock crushers.” she caught mylook of mild surprise. “we get through a lot of rocks. and they have to be very carefullyprepared. you have to make sure there is no contamination from previous samples no dustor anything. it’s quite a meticulous process.” she showed me the rock crushing machines,which were indeed pristine, though the rock crushers had apparently gone for coffee. besidethe machines were large boxes containing rocks of all shapes and sizes. they do indeed getthrough a lot of rocks at the anu. back in bennett’s office after our tour, i noticed hanging on her wall a poster giving anartist’s colorfully imaginative interpretation of earth as it might have looked 3.5 billion yearsago, just when life was getting going, in the ancient period known to earth science as thearchaean. the poster showed an alien landscape of huge, very active volcanoes, and asteamy, copper colored sea beneath a harsh red sky. stromatolites, a kind of bacterial rock,filled the shallows in the foreground. it didn’t look like a very promising place to create andnurture life. i asked her if the painting was accurate. “well, one school of thought says it was actually cool then because the sun was muchweaker.” (i later learned that biologists, when they are feeling jocose, refer to this as the“chinese restaurant problem” because we had a dim sun.) “without an atmosphereultraviolet rays from the sun, even from a weak sun, would have tended to break apart anyincipient bonds made by molecules. and yet right there” she tapped the stromatolites “youhave organisms almost at the surface. it’s a puzzle.” “so we don’t know what the world was like back then?” “mmmm,” she agreed thoughtfully. “either way it doesn’t seem very conducive to life.” she nodded amiably. “but there must have been something that suited life. otherwise wewouldn’t be here.” it certainly wouldn’t have suited us. if you were to step from a time machine into thatancient archaean world, you would very swiftly scamper back inside, for there was no moreoxygen to breathe on earth back then than there is on mars today. it was also full of noxiousvapors from hydrochloric and sulfuric acids powerful enough to eat through clothing andblister skin. nor would it have provided the clean and glowing vistas depicted in the poster invictoria bennett’s office. the chemical stew that was the atmosphere then would haveallowed little sunlight to reach the earth’s surface. what little you could see would beillumined only briefly by bright and frequent lightning flashes. in short, it was earth, but anearth we wouldn’t recognize as our own. anniversaries were few and far between in the archaean world. for two billion yearsbacterial organisms were the only forms of life. they lived, they reproduced, they swarmed,but they didn’t show any particular inclination to move on to another, more challenging levelof existence. at some point in the first billion years of life, cyanobacteria, or blue green algae,learned to tap into a freely available resource the hydrogen that exists in spectacularabundance in water. they absorbed water molecules, supped on the hydrogen, and releasedthe oxygen as waste, and in so doing invented photosynthesis. as margulis and sagan note,photosynthesis is “undoubtedly the most important single metabolic innovation in the historyof life on the planet” and it was invented not by plants but by bacteria. as cyanobacteria proliferated the world began to fill with o2to the consternation of thoseorganisms that found it poisonous which in those days was all of them. in an anaerobic (or anon oxygen using) world, oxygen is extremely poisonous. our white cells actually useoxygen to kill invading bacteria. that oxygen is fundamentally toxic often comes as a surpriseto those of us who find it so convivial to our well being, but that is only because we haveevolved to exploit it. to other things it is a terror. it is what turns butter rancid and makes ironrust. even we can tolerate it only up to a point. the oxygen level in our cells is only about atenth the level found in the atmosphere. the new oxygen using organisms had two advantages. oxygen was a more efficient way toproduce energy, and it vanquished competitor organisms. some retreated into the oozy,anaerobic world of bogs and lake bottoms. others did likewise but then later (much later)migrated to the digestive tracts of beings like you and me. quite a number of these primevalentities are alive inside your body right now, helping to digest your food, but abhorring eventhe tiniest hint of o2. untold numbers of others failed to adapt and died. the cyanobacteria were a runaway success. at first, the extra oxygen they produced didn’taccumulate in the atmosphere, but combined with iron to form ferric oxides, which sank to thebottom of primitive seas. for millions of years, the world literally rusted a phenomenonvividly recorded in the banded iron deposits that provide so much of the world’s iron oretoday. for many tens of millions of years not a great deal more than this happened. if youwent back to that early proterozoic world you wouldn’t find many signs of promise for earth’s future life. perhaps here and there in sheltered pools you’d encounter a film of livingscum or a coating of glossy greens and browns on shoreline rocks, but otherwise life remainedinvisible. but about 3.5 billion years ago something more emphatic became apparent. wherever theseas were shallow, visible structures began to appear. as they went through their chemicalroutines, the cyanobacteria became very slightly tacky, and that tackiness trappedmicroparticles of dust and sand, which became bound together to form slightly weird but solidstructures the stromatolites that were featured in the shallows of the poster on victoriabennett’s office wall. stromatolites came in various shapes and sizes. sometimes they lookedlike enormous cauliflowers, sometimes like fluffy mattresses (stromatolite comes from thegreek for “mattress”), sometimes they came in the form of columns, rising tens of metersabove the surface of the water sometimes as high as a hundred meters. in all theirmanifestations, they were a kind of living rock, and they represented the world’s firstcooperative venture, with some varieties of primitive organism living just at the surface andothers living just underneath, each taking advantage of conditions created by the other. theworld had its first ecosystem. for many years, scientists knew about stromatolites from fossil formations, but in 1961they got a real surprise with the discovery of a community of living stromatolites at sharkbay on the remote northwest coast of australia. this was most unexpected so unexpected,in fact, that it was some years before scientists realized quite what they had found. today,however, shark bay is a tourist attraction or at least as much of a tourist attraction as a placehundreds of miles from anywhere much and dozens of miles from anywhere at all can ever be.boardwalks have been built out into the bay so that visitors can stroll over the water to get agood look at the stromatolites, quietly respiring just beneath the surface. they are lusterlessand gray and look, as i recorded in an earlier book, like very large cow pats. but it is acuriously giddying moment to find yourself staring at living remnants of earth as it was 3.5billion years ago. as richard fortey has put it: “this is truly time traveling, and if the worldwere attuned to its real wonders this sight would be as well known as the pyramids of giza.”although you’d never guess it, these dull rocks swarm with life, with an estimated (well,obviously estimated) three billion individual organisms on every square yard of rock.sometimes when you look carefully you can see tiny strings of bubbles rising to the surface asthey give up their oxygen. in two billion years such tiny exertions raised the level of oxygenin earth’s atmosphere to 20 percent, preparing the way for the next, more complex chapter inlife’s history. it has been suggested that the cyanobacteria at shark bay are perhaps the slowest evolvingorganisms on earth, and certainly now they are among the rarest. having prepared the way formore complex life forms, they were then grazed out of existence nearly everywhere by thevery organisms whose existence they had made possible. (they exist at shark bay becausethe waters are too saline for the creatures that would normally feast on them.) one reason life took so long to grow complex was that the world had to wait until thesimpler organisms had oxygenated the atmosphere sufficiently. “animals could not summonup the energy to work,” as fortey has put it. it took about two billion years, roughly 40percent of earth’s history, for oxygen levels to reach more or less modern levels ofconcentration in the atmosphere. but once the stage was set, and apparently quite suddenly, anentirely new type of cell arose one with a nucleus and other little bodies collectively calledorganelles (from a greek word meaning “little tools”). the process is thought to have startedwhen some blundering or adventuresome bacterium either invaded or was captured by some other bacterium and it turned out that this suited them both. the captive bacterium became, itis thought, a mitochondrion. this mitochondrial invasion (or endosymbiotic event, asbiologists like to term it) made complex life possible. (in plants a similar invasion producedchloroplasts, which enable plants to photosynthesize.) mitochondria manipulate oxygen in a way that liberates energy from foodstuffs. withoutthis niftily facilitating trick, life on earth today would be nothing more than a sludge ofsimple microbes. mitochondria are very tiny you could pack a billion into the spaceoccupied by a grain of sand but also very hungry. almost every nutriment you absorb goesto feeding them. we couldn’t live for two minutes without them, yet even after a billion years mitochondriabehave as if they think things might not work out between us. they maintain their own dna.they reproduce at a different time from their host cell. they look like bacteria, divide likebacteria, and sometimes respond to antibiotics in the way bacteria do. in short, they keep theirbags packed. they don’t even speak the same genetic language as the cell in which they live.it is like having a stranger in your house, but one who has been there for a billion years. the new type of cell is known as a eukaryote (meaning “truly nucleated”), as contrastedwith the old type, which is known as a prokaryote (“prenucleated”), and it seems to havearrived suddenly in the fossil record. the oldest eukaryotes yet known, called grypania, werediscovered in iron sediments in michigan in 1992. such fossils have been found just once, andthen no more are known for 500 million years. compared with the new eukaryotes the old prokaryotes were little more than “bags ofchemicals,” in the words of the geologist stephen drury. eukaryotes were bigger eventuallyas much as ten thousand times bigger than their simpler cousins, and carried as much as athousand times more dna. gradually a system evolved in which life was dominated by twotypes of form organisms that expel oxygen (like plants) and those that take it in (you andme). single celled eukaryotes were once called protozoa (“pre animals”), but that term isincreasingly disdained. today the common term for them is protists . compared with thebacteria that had gone before, these new protists were wonders of design and sophistication.the simple amoeba, just one cell big and without any ambitions but to exist, contains 400million bits of genetic information in its dna enough, as carl sagan noted, to fill eightybooks of five hundred pages. eventually the eukaryotes learned an even more singular trick. it took a long time abillion years or so but it was a good one when they mastered it. they learned to formtogether into complex multicellular beings. thanks to this innovation, big, complicated,visible entities like us were possible. planet earth was ready to move on to its next ambitiousphase. but before we get too excited about that, it is worth remembering that the world, as we areabout to see, still belongs to the very small. 20 small worldit’s probably not a good idea to take too personal an interest in your microbes. louispasteur, the great french chemist and bacteriologist, became so preoccupied with them that hetook to peering critically at every dish placed before him with a magnifying glass, a habit thatpresumably did not win him many repeat invitations to dinner. in fact, there is no point in trying to hide from your bacteria, for they are on and around youalways, in numbers you can’t conceive. if you are in good health and averagely diligent abouthygiene, you will have a herd of about one trillion bacteria grazing on your fleshy plains about a hundred thousand of them on every square centimeter of skin. they are there to dineoff the ten billion or so flakes of skin you shed every day, plus all the tasty oils and fortifyingminerals that seep out from every pore and fissure. you are for them the ultimate food court,with the convenience of warmth and constant mobility thrown in. by way of thanks, they giveyou b.o. and those are just the bacteria that inhabit your skin. there are trillions more tucked awayin your gut and nasal passages, clinging to your hair and eyelashes, swimming over thesurface of your eyes, drilling through the enamel of your teeth. your digestive system alone ishost to more than a hundred trillion microbes, of at least four hundred types. some deal withsugars, some with starches, some attack other bacteria. a surprising number, like theubiquitous intestinal spirochetes, have no detectable function at all. they just seem to like tobe with you. every human body consists of about 10 quadrillion cells, but about 100quadrillion bacterial cells. they are, in short, a big part of us. from the bacteria’s point ofview, of course, we are a rather small part of them. because we humans are big and clever enough to produce and utilize antibiotics anddisinfectants, it is easy to convince ourselves that we have banished bacteria to the fringes ofexistence. don’t you believe it. bacteria may not build cities or have interesting social lives,but they will be here when the sun explodes. this is their planet, and we are on it onlybecause they allow us to be. bacteria, never forget, got along for billions of years without us. we couldn’t survive a daywithout them. they process our wastes and make them usable again; without their diligentmunching nothing would rot. they purify our water and keep our soils productive. bacteriasynthesize vitamins in our gut, convert the things we eat into useful sugars andpolysaccharides, and go to war on alien microbes that slip down our gullet. we depend totally on bacteria to pluck nitrogen from the air and convert it into usefulnucleotides and amino acids for us. it is a prodigious and gratifying feat. as margulis andsagan note, to do the same thing industrially (as when making fertilizers) manufacturers mustheat the source materials to 500 degrees centigrade and squeeze them to three hundred timesnormal pressures. bacteria do it all the time without fuss, and thank goodness, for no larger organism could survive without the nitrogen they pass on. above all, microbes continue toprovide us with the air we breathe and to keep the atmosphere stable. microbes, including themodern versions of cyanobacteria, supply the greater part of the planet’s breathable oxygen.algae and other tiny organisms bubbling away in the sea blow out about 150 billion kilos ofthe stuff every year. and they are amazingly prolific. the more frantic among them can yield a new generationin less than ten minutes; clostridium perfringens, the disagreeable little organism that causesgangrene, can reproduce in nine minutes. at such a rate, a single bacterium could theoreticallyproduce more offspring in two days than there are protons in the universe. “given an adequatesupply of nutrients, a single bacterial cell can generate 280,000 billion individuals in a singleday,” according to the belgian biochemist and nobel laureate christian de duve. in the sameperiod, a human cell can just about manage a single division. about once every million divisions, they produce a mutant. usually this is bad luck for themutant change is always risky for an organism but just occasionally the new bacterium isendowed with some accidental advantage, such as the ability to elude or shrug off an attack ofantibiotics. with this ability to evolve rapidly goes another, even scarier advantage. bacteriashare information. any bacterium can take pieces of genetic coding from any other.essentially, as margulis and sagan put it, all bacteria swim in a single gene pool. anyadaptive change that occurs in one area of the bacterial universe can spread to any other. it’srather as if a human could go to an insect to get the necessary genetic coding to sprout wingsor walk on ceilings. it means that from a genetic point of view bacteria have become a singlesuperorganism tiny, dispersed, but invincible. they will live and thrive on almost anything you spill, dribble, or shake loose. just givethem a little moisture as when you run a damp cloth over a counter and they will bloom asif created from nothing. they will eat wood, the glue in wallpaper, the metals in hardenedpaint. scientists in australia found microbes known as thiobacillus concretivorans that livedin indeed, could not live without concentrations of sulfuric acid strong enough to dissolvemetal. a species called micrococcus radiophilus was found living happily in the waste tanksof nuclear reactors, gorging itself on plutonium and whatever else was there. some bacteriabreak down chemical materials from which, as far as we can tell, they gain no benefit at all. they have been found living in boiling mud pots and lakes of caustic soda, deep insiderocks, at the bottom of the sea, in hidden pools of icy water in the mcmurdo dry valleys ofantarctica, and seven miles down in the pacific ocean where pressures are more than athousand times greater than at the surface, or equivalent to being squashed beneath fiftyjumbo jets. some of them seem to be practically indestructible. deinococcus radiodurans is,according to theeconomist , “almost immune to radioactivity.” blast its dna with radiation,and the pieces immediately reform “like the scuttling limbs of an undead creature from ahorror movie.” perhaps the most extraordinary survival yet found was that of a streptococcus bacteriumthat was recovered from the sealed lens of a camera that had stood on the moon for two years.in short, there are few environments in which bacteria aren’t prepared to live. “they arefinding now that when they push probes into ocean vents so hot that the probes actually startto melt, there are bacteria even there,” victoria bennett told me. in the 1920s two scientists at the university of chicago, edson bastin and frank greer,announced that they had isolated from oil wells strains of bacteria that had been living at depths of two thousand feet. the notion was dismissed as fundamentally preposterous therewas nothing to live on at two thousand feet and for fifty years it was assumed that theirsamples had been contaminated with surface microbes. we now know that there are a lot ofmicrobes living deep within the earth, many of which have nothing at all to do with theorganic world. they eat rocks or, rather, the stuff that’s in rocks iron, sulfur, manganese,and so on. and they breathe odd things too iron, chromium, cobalt, even uranium. suchprocesses may be instrumental in concentrating gold, copper, and other precious metals, andpossibly deposits of oil and natural gas. it has even been suggested that their tireless nibblingscreated the earth’s crust. some scientists now think that there could be as much as 100 trillion tons of bacteria livingbeneath our feet in what are known as subsurface lithoautotrophic microbial ecosystems slime for short. thomas gold of cornell has estimated that if you took all the bacteria out ofthe earth’s interior and dumped it on the surface, it would cover the planet to a depth of fivefeet. if the estimates are correct, there could be more life under the earth than on top of it. at depth microbes shrink in size and become extremely sluggish. the liveliest of them maydivide no more than once a century, some no more than perhaps once in five hundred years.as the economist has put it: “the key to long life, it seems, is not to do too much.” whenthings are really tough, bacteria are prepared to shut down all systems and wait for bettertimes. in 1997 scientists successfully activated some anthrax spores that had lain dormant foreighty years in a museum display in trondheim, norway. other microorganisms have leaptback to life after being released from a 118 year old can of meat and a 166 year old bottle ofbeer. in 1996, scientists at the russian academy of science claimed to have revived bacteriafrozen in siberian permafrost for three million years. but the record claim for durability so faris one made by russell vreeland and colleagues at west chester university in pennsylvaniain 2000, when they announced that they had resuscitated 250 million year old bacteria calledbacillus permians that had been trapped in salt deposits two thousand feet underground incarlsbad, new mexico. if so, this microbe is older than the continents. the report met with some understandable dubiousness. many biochemists maintained thatover such a span the microbe’s components would have become uselessly degraded unless thebacterium roused itself from time to time. however, if the bacterium did stir occasionallythere was no plausible internal source of energy that could have lasted so long. the moredoubtful scientists suggested that the sample may have been contaminated, if not during itsretrieval then perhaps while still buried. in 2001, a team from tel aviv university argued thatb. permians were almost identical to a strain of modern bacteria, bacillus marismortui, foundin the dead sea. only two of its genetic sequences differed, and then only slightly. “are we to believe,” the israeli researchers wrote, “that in 250 million years b. permianshas accumulated the same amount of genetic differences that could be achieved in just 3 7days in the laboratory?” in reply, vreeland suggested that “bacteria evolve faster in the labthan they do in the wild.” maybe. it is a remarkable fact that well into the space age, most school textbooks divided the worldof the living into just two categories plant and animal. microorganisms hardly featured.amoebas and similar single celled organisms were treated as proto animals and algae as proto plants. bacteria were usually lumped in with plants, too, even though everyone knewthey didn’t belong there. as far back as the late nineteenth century the german naturalisternst haeckel had suggested that bacteria deserved to be placed in a separate kingdom, whichhe called monera, but the idea didn’t begin to catch on among biologists until the 1960s andthen only among some of them. (i note that my trusty american heritage desk dictionaryfrom 1969 doesn’t recognize the term.) many organisms in the visible world were also poorly served by the traditional division.fungi, the group that includes mushrooms, molds, mildews, yeasts, and puffballs, were nearlyalways treated as botanical objects, though in fact almost nothing about them how theyreproduce and respire, how they build themselves matches anything in the plant world.structurally they have more in common with animals in that they build their cells from chitin,a material that gives them their distinctive texture. the same substance is used to make theshells of insects and the claws of mammals, though it isn’t nearly so tasty in a stag beetle as ina portobello mushroom. above all, unlike all plants, fungi don’t photosynthesize, so theyhave no chlorophyll and thus are not green. instead they grow directly on their food source,which can be almost anything. fungi will eat the sulfur off a concrete wall or the decayingmatter between your toes two things no plant will do. almost the only plantlike quality theyhave is that they root. even less comfortably susceptible to categorization was the peculiar group of organismsformally called myxomycetes but more commonly known as slime molds. the name no doubthas much to do with their obscurity. an appellation that sounded a little more dynamic “ambulant self activating protoplasm,” say and less like the stuff you find when you reachdeep into a clogged drain would almost certainly have earned these extraordinary entities amore immediate share of the attention they deserve, for slime molds are, make no mistake,among the most interesting organisms in nature. when times are good, they exist as one celled individuals, much like amoebas. but when conditions grow tough, they crawl to acentral gathering place and become, almost miraculously, a slug. the slug is not a thing ofbeauty and it doesn’t go terribly far usually just from the bottom of a pile of leaf litter to thetop, where it is in a slightly more exposed position but for millions of years this may wellhave been the niftiest trick in the universe. and it doesn’t stop there. having hauled itself up to a more favorable locale, the slimemold transforms itself yet again, taking on the form of a plant. by some curious orderlyprocess the cells reconfigure, like the members of a tiny marching band, to make a stalk atopof which forms a bulb known as a fruiting body. inside the fruiting body are millions ofspores that, at the appropriate moment, are released to the wind to blow away and becomesingle celled organisms that can start the process again. for years slime molds were claimed as protozoa by zoologists and as fungi by mycologists,though most people could see they didn’t really belong anywhere. when genetic testingarrived, people in lab coats were surprised to find that slime molds were so distinctive andpeculiar that they weren’t directly related to anything else in nature, and sometimes not evento each other. in 1969, in an attempt to bring some order to the growing inadequacies of classification, anecologist from cornell university named r. h. whittaker unveiled in the journalscience aproposal to divide life into five principal branches kingdoms, as they are known calledanimalia, plantae, fungi, protista, and monera. protista, was a modification of an earlier term, protoctista, which had been suggested a century earlier by a scottish biologist namedjohn hogg, and was meant to describe any organisms that were neither plant nor animal. though whittaker’s new scheme was a great improvement, protista remained ill defined.some taxonomists reserved it for large unicellular organisms the eukaryotes but otherstreated it as the kind of odd sock drawer of biology, putting into it anything that didn’t fitanywhere else. it included (depending on which text you consulted) slime molds, amoebas,and even seaweed, among much else. by one calculation it contained as many as 200,000different species of organism all told. that’s a lot of odd socks. ironically, just as whittaker’s five kingdom classification was beginning to find its wayinto textbooks, a retiring academic at the university of illinois was groping his way toward adiscovery that would challenge everything. his name was carl woese (rhymes with rose), andsince the mid 1960s or about as early as it was possible to do so he had been quietlystudying genetic sequences in bacteria. in the early days, this was an exceedingly painstakingprocess. work on a single bacterium could easily consume a year. at that time, according towoese, only about 500 species of bacteria were known, which is fewer than the number ofspecies you have in your mouth. today the number is about ten times that, though that is stillfar short of the 26,900 species of algae, 70,000 of fungi, and 30,800 of amoebas and relatedorganisms whose biographies fill the annals of biology. it isn’t simple indifference that keeps the total low. bacteria can be exasperatingly difficultto isolate and study. only about 1 percent will grow in culture. considering how wildlyadaptable they are in nature, it is an odd fact that the one place they seem not to wish to live isa petri dish. plop them on a bed of agar and pamper them as you will, and most will just liethere, declining every inducement to bloom. any bacterium that thrives in a lab is bydefinition exceptional, and yet these were, almost exclusively, the organisms studied bymicrobiologists. it was, said woese, “like learning about animals from visiting zoos.” genes, however, allowed woese to approach microorganisms from another angle. as heworked, woese realized that there were more fundamental divisions in the microbial worldthan anyone suspected. a lot of little organisms that looked like bacteria and behaved likebacteria were actually something else altogether something that had branched off frombacteria a long time ago. woese called these organisms archaebacteria, later shortened toarchaea. it has be said that the attributes that distinguish archaea from bacteria are not the sort thatwould quicken the pulse of any but a biologist. they are mostly differences in their lipids andan absence of something called peptidoglycan. but in practice they make a world ofdifference. archaeans are more different from bacteria than you and i are from a crab orspider. singlehandedly woese had discovered an unsuspected division of life, so fundamentalthat it stood above the level of kingdom at the apogee of the universal tree of life, as it israther reverentially known. in 1976, he startled the world or at least the little bit of it that was paying attention byredrawing the tree of life to incorporate not five main divisions, but twenty three. these hegrouped under three new principal categories bacteria, archaea, and eukarya (sometimesspelled eucarya) which he called domains. woese’s new divisions did not take the biological world by storm. some dismissed them asmuch too heavily weighted toward the microbial. many just ignored them. woese, according to frances ashcroft, “felt bitterly disappointed.” but slowly his new scheme began to catchon among microbiologists. botanists and zoologists were much slower to admire its virtues.it’s not hard to see why. on woese’s model, the worlds of botany and zoology are relegatedto a few twigs on the outermost branch of the eukaryan limb. everything else belongs tounicellular beings. “these folks were brought up to classify in terms of gross morphological similarities anddifferences,” woese told an interviewer in 1996. “the idea of doing so in terms of molecularsequence is a bit hard for many of them to swallow.” in short, if they couldn’t see a differencewith their own eyes, they didn’t like it. and so they persisted with the traditional five kingdom division an arrangement that woese called “not very useful” in his mildermoments and “positively misleading” much of the rest of the time. “biology, like physicsbefore it,” woese wrote, “has moved to a level where the objects of interest and theirinteractions often cannot be perceived through direct observation.” in 1998 the great and ancient harvard zoologist ernst mayr (who then was in his ninety fourth year and at the time of my writing is nearing one hundred and still going strong) stirredthe pot further by declaring that there should be just two prime divisions of life “empires”he called them. in a paper published in the proceedings of the national academy of sciences,mayr said that woese’s findings were interesting but ultimately misguided, noting that“woese was not trained as a biologist and quite naturally does not have an extensivefamiliarity with the principles of classification,” which is perhaps as close as onedistinguished scientist can come to saying of another that he doesn’t know what he is talkingabout. the specifics of mayr’s criticisms are too technical to need extensive airing here theyinvolve issues of meiotic sexuality, hennigian cladification, and controversial interpretationsof the genome of methanobacterium thermoautrophicum, among rather a lot else butessentially he argues that woese’s arrangement unbalances the tree of life. the bacterialrealm, mayr notes, consists of no more than a few thousand species while the archaean has amere 175 named specimens, with perhaps a few thousand more to be found “but hardlymore than that.” by contrast, the eukaryotic realm that is, the complicated organisms withnucleated cells, like us numbers already in the millions. for the sake of “the principle ofbalance,” mayr argues for combining the simple bacterial organisms in a single category,prokaryota, while placing the more complex and “highly evolved” remainder in the empireeukaryota, which would stand alongside as an equal. put another way, he argues for keepingthings much as they were before. this division between simple cells and complex cells “iswhere the great break is in the living world.” the distinction between halophilic archaeans and methanosarcina or between flavobacteriaand gram positive bacteria clearly will never be a matter of moment for most of us, but it isworth remembering that each is as different from its neighbors as animals are from plants. ifwoese’s new arrangement teaches us anything it is that life really is various and that most ofthat variety is small, unicellular, and unfamiliar. it is a natural human impulse to think ofevolution as a long chain of improvements, of a never ending advance toward largeness andcomplexity in a word, toward us. we flatter ourselves. most of the real diversity inevolution has been small scale. we large things are just flukes an interesting side branch. ofthe twenty three main divisions of life, only three plants, animals, and fungi are largeenough to be seen by the human eye, and even they contain species that are microscopic.indeed, according to woese, if you totaled up all the biomass of the planet every living thing, plants included microbes would account for at least 80 percent of all there is, perhapsmore. the world belongs to the very small and it has for a very long time. so why, you are bound to ask at some point in your life, do microbes so often want to hurtus? what possible satisfaction could there be to a microbe in having us grow feverish orchilled, or disfigured with sores, or above all expire? a dead host, after all, is hardly going toprovide long term hospitality. to begin with, it is worth remembering that most microorganisms are neutral or evenbeneficial to human well being. the most rampantly infectious organism on earth, abacterium called wolbachia, doesn’t hurt humans at all or, come to that, any othervertebrates but if you are a shrimp or worm or fruit fly, it can make you wish you had neverbeen born. altogether, only about one microbe in a thousand is a pathogen for humans,according to national geographic  though, knowing what some of them can do, we couldbe forgiven for thinking that that is quite enough. even if mostly benign, microbes are still thenumber three killer in the western world, and even many less lethal ones of course make usdeeply rue their existence. making a host unwell has certain benefits for the microbe. the symptoms of an illnessoften help to spread the disease. vomiting, sneezing, and diarrhea are excellent methods ofgetting out of one host and into position for another. the most effective strategy of all is toenlist the help of a mobile third party. infectious organisms love mosquitoes because themosquito’s sting delivers them directly to a bloodstream where they can get straight to workbefore the victim’s defense mechanisms can figure out what’s hit them. this is why so manygrade a diseases malaria, yellow fever, dengue fever, encephalitis, and a hundred or soother less celebrated but often rapacious maladies begin with a mosquito bite. it is afortunate fluke for us that hiv, the aids agent, isn’t among them at least not yet. any hivthe mosquito sucks up on its travels is dissolved by the mosquito’s own metabolism. whenthe day comes that the virus mutates its way around this, we may be in real trouble. it is a mistake, however, to consider the matter too carefully from the position of logicbecause microorganisms clearly are not calculating entities. they don’t care what they do toyou any more than you care what distress you cause when you slaughter them by the millionswith a soapy shower or a swipe of deodorant. the only time your continuing well being is ofconsequence to a pathogen is when it kills you too well. if they eliminate you before they canmove on, then they may well die out themselves. this in fact sometimes happens. history,jared diamond notes, is full of diseases that “once caused terrifying epidemics and thendisappeared as mysteriously as they had come.” he cites the robust but mercifully transientenglish sweating sickness, which raged from 1485 to 1552, killing tens of thousands as itwent, before burning itself out. too much efficiency is not a good thing for any infectiousorganism. a great deal of sickness arises not because of what the organism has done to you but whatyour body is trying to do to the organism. in its quest to rid the body of pathogens, theimmune system sometimes destroys cells or damages critical tissues, so often when you areunwell what you are feeling is not the pathogens but your own immune responses. anyway,getting sick is a sensible response to infection. sick people retire to their beds and thus areless of a threat to the wider community. resting also frees more of the body’s resources toattend to the infection. because there are so many things out there with the potential to hurt you, your body holdslots of different varieties of defensive white cells some ten million types in all, eachdesigned to identify and destroy a particular sort of invader. it would be impossibly inefficientto maintain ten million separate standing armies, so each variety of white cell keeps only afew scouts on active duty. when an infectious agent what’s known as an antigen invades,relevant scouts identify the attacker and put out a call for reinforcements of the right type.while your body is manufacturing these forces, you are likely to feel wretched. the onset ofrecovery begins when the troops finally swing into action. white cells are merciless and will hunt down and kill every last pathogen they can find. toavoid extinction, attackers have evolved two elemental strategies. either they strike quicklyand move on to a new host, as with common infectious illnesses like flu, or they disguisethemselves so that the white cells fail to spot them, as with hiv, the virus responsible foraids, which can sit harmlessly and unnoticed in the nuclei of cells for years before springinginto action. one of the odder aspects of infection is that microbes that normally do no harm at allsometimes get into the wrong parts of the body and “go kind of crazy,” in the words of dr.bryan marsh, an infectious diseases specialist at dartmouth hitchcock medical center inlebanon, new hamphire. “it happens all the time with car accidents when people sufferinternal injuries. microbes that are normally benign in the gut get into other parts of thebody the bloodstream, for instance and cause terrible havoc.” the scariest, most out of control bacterial disorder of the moment is a disease callednecrotizing fasciitis in which bacteria essentially eat the victim from the inside out, devouringinternal tissue and leaving behind a pulpy, noxious residue. patients often come in withcomparatively mild complaints a skin rash and fever typically but then dramaticallydeteriorate. when they are opened up it is often found that they are simply being consumed.the only treatment is what is known as “radical excisional surgery” cutting out every bit ofinfected area. seventy percent of victims die; many of the rest are left terribly disfigured. thesource of the infection is a mundane family of bacteria called group a streptococcus, whichnormally do no more than cause strep throat. very occasionally, for reasons unknown, someof these bacteria get through the lining of the throat and into the body proper, where theywreak the most devastating havoc. they are completely resistant to antibiotics. about athousand cases a year occur in the united states, and no one can say that it won’t get worse. precisely the same thing happens with meningitis. at least 10 percent of young adults, andperhaps 30 percent of teenagers, carry the deadly meningococcal bacterium, but it lives quiteharmlessly in the throat. just occasionally in about one young person in a hundredthousand it gets into the bloodstream and makes them very ill indeed. in the worst cases,death can come in twelve hours. that’s shockingly quick. “you can have a person who’s inperfect health at breakfast and dead by evening,” says marsh. we would have much more success with bacteria if we weren’t so profligate with our bestweapon against them: antibiotics. remarkably, by one estimate some 70 percent of theantibiotics used in the developed world are given to farm animals, often routinely in stockfeed, simply to promote growth or as a precaution against infection. such applications givebacteria every opportunity to evolve a resistance to them. it is an opportunity that they haveenthusiastically seized. in 1952, penicillin was fully effective against all strains of staphylococcus bacteria, to suchan extent that by the early 1960s the u.s. surgeon general, william stewart, felt confidentenough to declare: “the time has come to close the book on infectious diseases. we havebasically wiped out infection in the united states.” even as he spoke, however, some 90percent of those strains were in the process of developing immunity to penicillin. soon one ofthese new strains, called methicillin resistant staphylococcus aureus, began to show up inhospitals. only one type of antibiotic, vancomycin, remained effective against it, but in 1997a hospital in tokyo reported the appearance of a strain that could resist even that. withinmonths it had spread to six other japanese hospitals. all over, the microbes are beginning towin the war again: in u.s. hospitals alone, some fourteen thousand people a year die frominfections they pick up there. as james surowiecki has noted, given a choice betweendeveloping antibiotics that people will take every day for two weeks or antidepressants thatpeople will take every day forever, drug companies not surprisingly opt for the latter.although a few antibiotics have been toughened up a bit, the pharmaceutical industry hasn’tgiven us an entirely new antibiotic since the 1970s. our carelessness is all the more alarming since the discovery that many other ailments maybe bacterial in origin. the process of discovery began in 1983 when barry marshall, a doctorin perth, western australia, found that many stomach cancers and most stomach ulcers arecaused by a bacterium called helicobacter pylori. even though his findings were easily tested,the notion was so radical that more than a decade would pass before they were generallyaccepted. america’s national institutes of health, for instance, didn’t officially endorse theidea until 1994. “hundreds, even thousands of people must have died from ulcers whowouldn’t have,” marshall told a reporter from forbes in 1999. since then further research has shown that there is or may well be a bacterial component inall kinds of other disorders heart disease, asthma, arthritis, multiple sclerosis, several typesof mental disorders, many cancers, even, it has been suggested (inscience no less), obesity.the day may not be far off when we desperately require an effective antibiotic and haven’tgot one to call on. it may come as a slight comfort to know that bacteria can themselves get sick. they aresometimes infected by bacteriophages (or simply phages), a type of virus. a virus is a strangeand unlovely entity “a piece of nucleic acid surrounded by bad news” in the memorablephrase of the nobel laureate peter medawar. smaller and simpler than bacteria, viruses aren’tthemselves alive. in isolation they are inert and harmless. but introduce them into a suitablehost and they burst into busyness into life. about five thousand types of virus are known,and between them they afflict us with many hundreds of diseases, ranging from the flu andcommon cold to those that are most invidious to human well being: smallpox, rabies, yellowfever, ebola, polio, and the human immunodeficiency virus, the source of aids. viruses prosper by hijacking the genetic material of a living cell and using it to producemore virus. they reproduce in a fanatical manner, then burst out in search of more cells toinvade. not being living organisms themselves, they can afford to be very simple. many,including hiv, have ten genes or fewer, whereas even the simplest bacteria require severalthousand. they are also very tiny, much too small to be seen with a conventional microscope.it wasn’t until 1943 and the invention of the electron microscope that science got its first lookat them. but they can do immense damage. smallpox in the twentieth century alone killed anestimated 300 million people. they also have an unnerving capacity to burst upon the world in some new and startlingform and then to vanish again as quickly as they came. in 1916, in one such case, people ineurope and america began to come down with a strange sleeping sickness, which becameknown as encephalitis lethargica. victims would go to sleep and not wake up. they could beroused without great difficulty to take food or go to the lavatory, and would answer questionssensibly they knew who and where they were though their manner was always apathetic. however, the moment they were permitted to rest, they would sink at once back intodeepest slumber and remain in that state for as long as they were left. some went on in thismanner for months before dying. a very few survived and regained consciousness but nottheir former liveliness. they existed in a state of profound apathy, “like extinct volcanoes,” inthe words of one doctor. in ten years the disease killed some five million people and thenquietly went away. it didn’t get much lasting attention because in the meantime an even worseepidemic indeed, the worst in history swept across the world. it is sometimes called the great swine flu epidemic and sometimes the great spanish fluepidemic, but in either case it was ferocious. world war i killed twenty one million people infour years; swine flu did the same in its first four months. almost 80 percent of americancasualties in the first world war came not from enemy fire, but from flu. in some units themortality rate was as high as 80 percent. swine flu arose as a normal, nonlethal flu in the spring of 1918, but somehow over thefollowing months no one knows how or where it mutated into something more severe. afifth of victims suffered only mild symptoms, but the rest became gravely ill and often died.some succumbed within hours; others held on for a few days. in the united states, the first deaths were recorded among sailors in boston in late august1918, but the epidemic quickly spread to all parts of the country. schools closed, publicentertainments were shut down, people everywhere wore masks. it did little good. betweenthe autumn of 1918 and spring of the following year, 548,452 people died of the flu inamerica. the toll in britain was 220,000, with similar numbers dead in france and germany.no one knows the global toll, as records in the third world were often poor, but it was notless than 20 million and probably more like 50 million. some estimates have put the globaltotal as high as 100 million. in an attempt to devise a vaccine, medical authorities conducted tests on volunteers at amilitary prison on deer island in boston harbor. the prisoners were promised pardons if theysurvived a battery of tests. these tests were rigorous to say the least. first the subjects wereinjected with infected lung tissue taken from the dead and then sprayed in the eyes, nose, andmouth with infectious aerosols. if they still failed to succumb, they had their throats swabbedwith discharges taken from the sick and dying. if all else failed, they were required to sitopen mouthed while a gravely ill victim was helped to cough into their faces. out of somewhat amazingly three hundred men who volunteered, the doctors chosesixty two for the tests. none contracted the flu not one. the only person who did grow illwas the ward doctor, who swiftly died. the probable explanation for this is that the epidemichad passed through the prison a few weeks earlier and the volunteers, all of whom hadsurvived that visitation, had a natural immunity. much about the 1918 flu is understood poorly or not at all. one mystery is how it eruptedsuddenly, all over, in places separated by oceans, mountain ranges, and other earthly impediments. a virus can survive for no more than a few hours outside a host body, so howcould it appear in madrid, bombay, and philadelphia all in the same week? the probable answer is that it was incubated and spread by people who had only slightsymptoms or none at all. even in normal outbreaks, about 10 percent of people have the flubut are unaware of it because they experience no ill effects. and because they remain incirculation they tend to be the great spreaders of the disease. that would account for the 1918 outbreak’s widespread distribution, but it still doesn’texplain how it managed to lay low for several months before erupting so explosively at moreor less the same time all over. even more mysterious is that it was primarily devastating topeople in the prime of life. flu normally is hardest on infants and the elderly, but in the 1918outbreak deaths were overwhelmingly among people in their twenties and thirties. olderpeople may have benefited from resistance gained from an earlier exposure to the same strain,but why the very young were similarly spared is unknown. the greatest mystery of all is whythe 1918 flu was so ferociously deadly when most flus are not. we still have no idea. from time to time certain strains of virus return. a disagreeable russian virus known ash1n1 caused severe outbreaks over wide areas in 1933, then again in the 1950s, and yet againin the 1970s. where it went in the meantime each time is uncertain. one suggestion is thatviruses hide out unnoticed in populations of wild animals before trying their hand at a newgeneration of humans. no one can rule out the possibility that the great swine flu epidemicmight once again rear its head. and if it doesn’t, others well might. new and frightening viruses crop up all the time.ebola, lassa, and marburg fevers all have tended to flare up and die down again, but no onecan say that they aren’t quietly mutating away somewhere, or simply awaiting the rightopportunity to burst forth in a catastrophic manner. it is now apparent that aids has beenamong us much longer than anyone originally suspected. researchers at the manchesterroyal infirmary in england discovered that a sailor who had died of mysterious, untreatablecauses in 1959 in fact had aids. but for whatever reasons the disease remained generallyquiescent for another twenty years. the miracle is that other such diseases haven’t gone rampant. lassa fever, which wasn’tfirst detected until 1969, in west africa, is extremely virulent and little understood. in 1969, adoctor at a yale university lab in new haven, connecticut, who was studying lassa fevercame down with it. he survived, but, more alarmingly, a technician in a nearby lab, with nodirect exposure, also contracted the disease and died. happily the outbreak stopped there, but we can’t count on such good fortune always. ourlifestyles invite epidemics. air travel makes it possible to spread infectious agents across theplanet with amazing ease. an ebola virus could begin the day in, say, benin, and finish it innew york or hamburg or nairobi, or all three. it means also that medical authoritiesincreasingly need to be acquainted with pretty much every malady that exists everywhere, butof course they are not. in 1990, a nigerian living in chicago was exposed to lassa fever on avisit to his homeland, but didn’t develop symptoms until he had returned to the united states.he died in a chicago hospital without diagnosis and without anyone taking any specialprecautions in treating him, unaware that he had one of the most lethal and infectious diseaseson the planet. miraculously, no one else was infected. we may not be so lucky next time. and on that sobering note, it’s time to return to the world of the visibly living. 21 life goes onit isn’t easy to become a fossil. the fate of nearly all living organisms over 99.9percent of them is to compost down to nothingness. when your spark is gone, everymolecule you own will be nibbled off you or sluiced away to be put to use in some othersystem. that’s just the way it is. even if you make it into the small pool of organisms, the lessthan 0.1 percent, that don’t get devoured, the chances of being fossilized are very small. in order to become a fossil, several things must happen. first, you must die in the rightplace. only about 15 percent of rocks can preserve fossils, so it’s no good keeling over on afuture site of granite. in practical terms the deceased must become buried in sediment, whereit can leave an impression, like a leaf in wet mud, or decompose without exposure to oxygen,permitting the molecules in its bones and hard parts (and very occasionally softer parts) to bereplaced by dissolved minerals, creating a petrified copy of the original. then as thesediments in which the fossil lies are carelessly pressed and folded and pushed about byearth’s processes, the fossil must somehow maintain an identifiable shape. finally, but aboveall, after tens of millions or perhaps hundreds of millions of years hidden away, it must befound and recognized as something worth keeping. only about one bone in a billion, it is thought, ever becomes fossilized. if that is so, itmeans that the complete fossil legacy of all the americans alive today that’s 270 millionpeople with 206 bones each will only be about fifty bones, one quarter of a completeskeleton. that’s not to say of course that any of these bones will actually be found. bearing inmind that they can be buried anywhere within an area of slightly over 3.6 million squaremiles, little of which will ever be turned over, much less examined, it would be something ofa miracle if they were. fossils are in every sense vanishingly rare. most of what has lived onearth has left behind no record at all. it has been estimated that less than one species in tenthousand has made it into the fossil record. that in itself is a stunningly infinitesimalproportion. however, if you accept the common estimate that the earth has produced 30billion species of creature in its time and richard leakey and roger lewin’s statement (inthe sixth extinction ) that there are 250,000 species of creature in the fossil record, thatreduces the proportion to just one in 120,000. either way, what we possess is the merestsampling of all the life that earth has spawned. moreover, the record we do have is hopelessly skewed. most land animals, of course, don’tdie in sediments. they drop in the open and are eaten or left to rot or weather down tonothing. the fossil record consequently is almost absurdly biased in favor of marine creatures.about 95 percent of all the fossils we possess are of animals that once lived under water,mostly in shallow seas. i mention all this to explain why on a gray day in february i went to the natural historymuseum in london to meet a cheerful, vaguely rumpled, very likeable paleontologist namedrichard fortey. fortey knows an awful lot about an awful lot. he is the author of a wry, splendid bookcalled life: an unauthorised biography, which covers the whole pageant of animate creation.but his first love is a type of marine creature called trilobites that once teemed in ordovicianseas but haven’t existed for a long time except in fossilized form. all shared a basic body planof three parts, or lobes head, tail, thorax from which comes the name. fortey found hisfirst when he was a boy clambering over rocks at st. david’s bay in wales. he was hookedfor life. he took me to a gallery of tall metal cupboards. each cupboard was filled with shallowdrawers, and each drawer was filled with stony trilobites twenty thousand specimens in all. “it seems like a big number,” he agreed, “but you have to remember that millions uponmillions of trilobites lived for millions upon millions of years in ancient seas, so twentythousand isn’t a huge number. and most of these are only partial specimens. finding acomplete trilobite fossil is still a big moment for a paleontologist.” trilobites first appeared fully formed, seemingly from nowhere about 540 million yearsago, near the start of the great outburst of complex life popularly known as the cambrianexplosion, and then vanished, along with a great deal else, in the great and still mysteriouspermian extinction 300,000 or so centuries later. as with all extinct creatures, there is anatural temptation to regard them as failures, but in fact they were among the most successfulanimals ever to live. their reign ran for 300 million years twice the span of dinosaurs,which were themselves one of history’s great survivors. humans, fortey points out, havesurvived so far for one half of 1 percent as long. with so much time at their disposal, the trilobites proliferated prodigiously. most remainedsmall, about the size of modern beetles, but some grew to be as big as platters. altogetherthey formed at least five thousand genera and sixty thousand species though more turn upall the time. fortey had recently been at a conference in south america where he wasapproached by an academic from a small provincial university in argentina. “she had a boxthat was full of interesting things trilobites that had never been seen before in southamerica, or indeed anywhere, and a great deal else. she had no research facilities to studythem and no funds to look for more. huge parts of the world are still unexplored.” “in terms of trilobites?” “no, in terms of everything.” throughout the nineteenth century, trilobites were almost the only known forms of earlycomplex life, and for that reason were assiduously collected and studied. the big mysteryabout them was their sudden appearance. even now, as fortey says, it can be startling to go tothe right formation of rocks and to work your way upward through the eons finding no visiblelife at all, and then suddenly “a whole profallotaspis or elenellus as big as a crab will popinto your waiting hands.” these were creatures with limbs, gills, nervous systems, probingantennae, “a brain of sorts,” in fortey’s words, and the strangest eyes ever seen. made of calcite rods, the same stuff that forms limestone, they constituted the earliest visual systemsknown. more than this, the earliest trilobites didn’t consist of just one venturesome speciesbut dozens, and didn’t appear in one or two locations but all over. many thinking people inthe nineteenth century saw this as proof of god’s handiwork and refutation of darwin’sevolutionary ideals. if evolution proceeded slowly, they asked, then how did he account forthis sudden appearance of complex, fully formed creatures? the fact is, he couldn’t. and so matters seemed destined to remain forever until one day in 1909, three months shyof the fiftieth anniversary of the publication of darwin’s on the origin of species , when apaleontologist named charles doolittle walcott made an extraordinary find in the canadianrockies. walcott was born in 1850 and grew up near utica, new york, in a family of modest means,which became more modest still with the sudden death of his father when walcott was aninfant. as a boy walcott discovered that he had a knack for finding fossils, particularlytrilobites, and built up a collection of sufficient distinction that it was bought by louisagassiz for his museum at harvard for a small fortune about $70,000 in today’s money.although he had barely a high school education and was self taught in the sciences, walcottbecame a leading authority on trilobites and was the first person to establish that trilobiteswere arthropods, the group that includes modern insects and crustaceans. in 1879 he took a job as a field researcher with the newly formed united states geologicalsurvey and served with such distinction that within fifteen years he had risen to be its head. in1907 he was appointed secretary of the smithsonian institution, where he remained until hisdeath in 1927. despite his administrative obligations, he continued to do fieldwork and towrite prolifically. “his books fill a library shelf,” according to fortey. not incidentally, hewas also a founding director of the national advisory committee for aeronautics, whicheventually became the national aeronautics and space agency, or nasa, and thus canrightly be considered the grandfather of the space age. but what he is remembered for now is an astute but lucky find in british columbia, highabove the little town of field, in the late summer of 1909. the customary version of the storyis that walcott, accompanied by his wife, was riding on horseback on a mountain trail beneaththe spot called the burgess ridge when his wife’s horse slipped on loose stones. dismountingto assist her, walcott discovered that the horse had turned a slab of shale that contained fossilcrustaceans of an especially ancient and unusual type. snow was falling winter comes earlyto the canadian rockies so they didn’t linger, but the next year at the first opportunitywalcott returned to the spot. tracing the presumed route of the rocks’ slide, he climbed 750feet to near the mountain’s summit. there, 8,000 feet above sea level, he found a shaleoutcrop, about the length of a city block, containing an unrivaled array of fossils from soonafter the moment when complex life burst forth in dazzling profusion the famous cambrianexplosion. walcott had found, in effect, the holy grail of paleontology. the outcrop becameknown as the burgess shale, and for a long time it provided “our sole vista upon the inceptionof modern life in all its fullness,” as the late stephen jay gould recorded in his popular bookwonderful life . gould, ever scrupulous, discovered from reading walcott’s diaries that the story of theburgess shale’s discovery appears to have been somewhat embroidered walcott makes nomention of a slipping horse or falling snow but there is no disputing that it was anextraordinary find. it is almost impossible for us whose time on earth is limited to a breezy few decades toappreciate how remote in time from us the cambrian outburst was. if you could fly backwardsinto the past at the rate of one year per second, it would take you about half an hour to reachthe time of christ, and a little over three weeks to get back to the beginnings of human life.but it would take you twenty years to reach the dawn of the cambrian period. it was, in otherwords, an extremely long time ago, and the world was a very different place. for one thing, 500 million plus years ago when the burgess shale was formed it wasn’t atthe top of a mountain but at the foot of one. specifically it was a shallow ocean basin at thebottom of a steep cliff. the seas of that time teemed with life, but normally the animals left norecord because they were soft bodied and decayed upon dying. but at burgess the cliffcollapsed, and the creatures below, entombed in a mudslide, were pressed like flowers in abook, their features preserved in wondrous detail. in annual summer trips from 1910 to 1925 (by which time he was seventy five years old),walcott excavated tens of thousands of specimens (gould says 80,000; the normallyunimpeachable fact checkers of national georgraphic say 60,000), which he brought back towashington for further study. in both sheer numbers and diversity the collection wasunparalleled. some of the burgess fossils had shells; many others did not. some were sighted,others blind. the variety was enormous, consisting of 140 species by one count. “the burgessshale included a range of disparity in anatomical designs never again equaled, and notmatched today by all the creatures in the world’s oceans,” gould wrote. unfortunately, according to gould, walcott failed to discern the significance of what hehad found. “snatching defeat from the jaws of victory,” gould wrote in another work, eightlittle piggies, “walcott then proceeded to misinterpret these magnificent fossils in the deepestpossible way.” he placed them into modern groups, making them ancestral to today’s worms,jellyfish, and other creatures, and thus failed to appreciate their distinctness. “under such aninterpretation,” gould sighed, “life began in primordial simplicity and moved inexorably,predictably onward to more and better.” walcott died in 1927 and the burgess fossils were largely forgotten. for nearly half acentury they stayed shut away in drawers in the american museum of natural history inwashington, seldom consulted and never questioned. then in 1973 a graduate student fromcambridge university named simon conway morris paid a visit to the collection. he wasastonished by what he found. the fossils were far more varied and magnificent than walcotthad indicated in his writings. in taxonomy the category that describes the basic body plans ofall organisms is the phylum, and here, conway morris concluded, were drawer after drawer ofsuch anatomical singularities all amazingly and unaccountably unrecognized by the manwho had found them. with his supervisor, harry whittington, and fellow graduate student derek briggs, conwaymorris spent the next several years making a systematic revision of the entire collection, andcranking out one exciting monograph after another as discovery piled upon discovery. manyof the creatures employed body plans that were not simply unlike anything seen before orsince, but were bizarrely different. one, opabinia, had five eyes and a nozzle like snout withclaws on the end. another, a disc shaped being called peytoia, looked almost comically like apineapple slice. a third had evidently tottered about on rows of stilt like legs, and was so oddthat they named it hallucigenia. there was so much unrecognized novelty in the collectionthat at one point upon opening a new drawer conway morris famously was heard to mutter,“oh fuck, not another phylum.” the english team’s revisions showed that the cambrian had been a time of unparalleledinnovation and experimentation in body designs. for almost four billion years life haddawdled along without any detectable ambitions in the direction of complexity, and thensuddenly, in the space of just five or ten million years, it had created all the basic bodydesigns still in use today. name a creature, from a nematode worm to cameron diaz, and theyall use architecture first created in the cambrian party. what was most surprising, however, was that there were so many body designs that hadfailed to make the cut, so to speak, and left no descendants. altogether, according to gould, atleast fifteen and perhaps as many as twenty of the burgess animals belonged to no recognizedphylum. (the number soon grew in some popular accounts to as many as one hundred farmore than the cambridge scientists ever actually claimed.) “the history of life,” wrote gould,“is a story of massive removal followed by differentiation within a few surviving stocks, notthe conventional tale of steadily increasing excellence, complexity, and diversity.”evolutionary success, it appeared, was a lottery. one creature thatdid manage to slip through, a small wormlike being called pikaiagracilens, was found to have a primitive spinal column, making it the earliest known ancestorof all later vertebrates, including us.pikaia were by no means abundant among the burgessfossils, so goodness knows how close they may have come to extinction. gould, in a famousquotation, leaves no doubt that he sees our lineal success as a fortunate fluke: “wind back thetape of life to the early days of the burgess shale; let it play again from an identical startingpoint, and the chance becomes vanishingly small that anything like human intelligence wouldgrace the replay.” gould’s book was published in 1989 to general critical acclaim and was a great commercialsuccess. what wasn’t generally known was that many scientists didn’t agree with gould’sconclusions at all, and that it was all soon to get very ugly. in the context of the cambrian,“explosion” would soon have more to do with modern tempers than ancient physiologicalfacts. in fact, we now know, complex organisms existed at least a hundred million years beforethe cambrian. we should have known a whole lot sooner. nearly forty years after walcottmade his discovery in canada, on the other side of the planet in australia, a young geologistnamed reginald sprigg found something even older and in its way just as remarkable. in 1946 sprigg was a young assistant government geologist for the state of south australiawhen he was sent to make a survey of abandoned mines in the ediacaran hills of the flindersrange, an expanse of baking outback some three hundred miles north of adelaide. the ideawas to see if there were any old mines that might be profitably reworked using newertechnologies, so he wasn’t studying surface rocks at all, still less fossils. but one day whileeating his lunch, sprigg idly overturned a hunk of sandstone and was surprised to put itmildly to see that the rock’s surface was covered in delicate fossils, rather like theimpressions leaves make in mud. these rocks predated the cambrian explosion. he waslooking at the dawn of visible life. sprigg submitted a paper to nature , but it was turned down. he read it instead at the nextannual meeting of the australian and new zealand association for the advancement ofscience, but it failed to find favor with the association’s head, who said the ediacaran imprints were merely “fortuitous inorganic markings” patterns made by wind or rain ortides, but not living beings. his hopes not yet entirely crushed, sprigg traveled to london andpresented his findings to the 1948 international geological congress, but failed to exciteeither interest or belief. finally, for want of a better outlet, he published his findings in thetransactions of the royal society of south australia. then he quit his government job andtook up oil exploration. nine years later, in 1957, a schoolboy named john mason, while walking throughcharnwood forest in the english midlands, found a rock with a strange fossil in it, similar toa modern sea pen and exactly like some of the specimens sprigg had found and been trying totell everyone about ever since. the schoolboy turned it in to a paleontologist at the universityof leicester, who identified it at once as precambrian. young mason got his picture in thepapers and was treated as a precocious hero; he still is in many books. the specimen wasnamed in his honor chamia masoni. today some of sprigg’s original ediacaran specimens, along with many of the other fifteenhundred specimens that have been found throughout the flinders range since that time, canbe seen in a glass case in an upstairs room of the stout and lovely south australian museumin adelaide, but they don’t attract a great deal of attention. the delicately etched patterns arerather faint and not terribly arresting to the untrained eye. they are mostly small and disc shaped, with occasional, vague trailing ribbons. fortey has described them as “soft bodiedoddities.” there is still very little agreement about what these things were or how they lived. theyhad, as far as can be told, no mouth or anus with which to take in and discharge digestivematerials, and no internal organs with which to process them along the way. “in life,” forteysays, “most of them probably simply lay upon the surface of the sandy sediment, like soft,structureless and inanimate flatfish.” at their liveliest, they were no more complex thanjellyfish. all the ediacaran creatures were diploblastic, meaning they were built from twolayers of tissue. with the exception of jellyfish, all animals today are triploblastic. some experts think they weren’t animals at all, but more like plants or fungi. thedistinctions between plant and animal are not always clear even now. the modern spongespends its life fixed to a single spot and has no eyes or brain or beating heart, and yet is ananimal. “when we go back to the precambrian the differences between plants and animalswere probably even less clear,” says fortey. “there isn’t any rule that says you have to bedemonstrably one or the other.” nor is it agreed that the ediacaran organisms are in any way ancestral to anything alivetoday (except possibly some jellyfish). many authorities see them as a kind of failedexperiment, a stab at complexity that didn’t take, possibly because the sluggish ediacaranorganisms were devoured or outcompeted by the lither and more sophisticated animals of thecambrian period. “there is nothing closely similar alive today,” fortey has written. “they are difficult tointerpret as any kind of ancestors of what was to follow.” the feeling was that ultimately they weren’t terribly important to the development of lifeon earth. many authorities believe that there was a mass extermination at the precambrian cambrian boundary and that all the ediacaran creatures (except the uncertain jellyfish) failed to move on to the next phase. the real business of complex life, in other words, started withthe cambrian explosion. that’s how gould saw it in any case. as for the revisions of the burgess shale fossils, almost at once people began to questionthe interpretations and, in particular, gould’s interpretation of the interpretations. “from thefirst there were a number of scientists who doubted the account that steve gould hadpresented, however much they admired the manner of its delivery,” fortey wrote in life. thatis putting it mildly. “if only stephen gould could think as clearly as he writes!” barked the oxford academicrichard dawkins in the opening line of a review (in the london sunday telegraph) ofwonderful life. dawkins acknowledged that the book was “unputdownable” and a “literarytour de force,” but accused gould of engaging in a “grandiloquent and near disingenuous”misrepresentation of the facts by suggesting that the burgess revisions had stunned thepaleontological community. “the view that he is attacking that evolution marchesinexorably toward a pinnacle such as man has not been believed for 50 years,” dawkinsfumed. and yet that was exactly the conclusion to which many general reviewers were drawn.one, writing in the new york times book review, cheerfully suggested that as a result ofgould’s book scientists “have been throwing out some preconceptions that they had notexamined for generations. they are, reluctantly or enthusiastically, accepting the idea thathumans are as much an accident of nature as a product of orderly development.” but the real heat directed at gould arose from the belief that many of his conclusions weresimply mistaken or carelessly inflated. writing in the journal evolution, dawkins attackedgould’s assertions that “evolution in the cambrian was a different kind of process fromtoday” and expressed exasperation at gould’s repeated suggestions that “the cambrian was aperiod of evolutionary ‘experiment,’ evolutionary ‘trial and error,’ evolutionary ‘false starts.’ .. . it was the fertile time when all the great ‘fundamental body plans’ were invented.nowadays, evolution just tinkers with old body plans. back in the cambrian, new phyla andnew classes arose. nowadays we only get new species!” noting how often this idea that there are no new body plans is picked up, dawkins says:“it is as though a gardener looked at an oak tree and remarked, wonderingly: ‘isn’t it strangethat no major new boughs have appeared on this tree for many years? these days, all the newgrowth appears to be at the twig level.’ ” “it was a strange time,” fortey says now, “especially when you reflected that this was allabout something that happened five hundred million years ago, but feelings really did runquite high. i joked in one of my books that i felt as if i ought to put a safety helmet on beforewriting about the cambrian period, but it did actually feel a bit like that.” strangest of all was the response of one of the heroes of wonderful life, simon conwaymorris, who startled many in the paleontological community by rounding abruptly on gouldin a book of his own, the crucible of creation. the book treated gould “with contempt, evenloathing,” in fortey’s words. “i have never encountered such spleen in a book by aprofessional,” fortey wrote later. “the casual reader of the crucible of creation, unaware of the history, would never gather that the author’s views had once been close to (if not actuallyshared with) gould’s.” when i asked fortey about it, he said: “well, it was very strange, quite shocking really,because gould’s portrayal of him had been so flattering. i could only assume that simon wasembarrassed. you know, science changes but books are permanent, and i suppose he regrettedbeing so irremediably associated with views that he no longer altogether held. there was allthat stuff about ‘oh fuck, another phylum’ and i expect he regretted being famous for that.” what happened was that the early cambrian fossils began to undergo a period of criticalreappraisal. fortey and derek briggs one of the other principals in gould’s book used amethod known as cladistics to compare the various burgess fossils. in simple terms, cladisticsconsists of organizing organisms on the basis of shared features. fortey gives as an examplethe idea of comparing a shrew and an elephant. if you considered the elephant’s large size andstriking trunk you might conclude that it could have little in common with a tiny, sniffingshrew. but if you compared both of them with a lizard, you would see that the elephant andshrew were in fact built to much the same plan. in essence, what fortey is saying is thatgould saw elephants and shrews where they saw mammals. the burgess creatures, theybelieved, weren’t as strange and various as they appeared at first sight. “they were often nostranger than trilobites,” fortey says now. “it is just that we have had a century or so to getused to trilobites. familiarity, you know, breeds familiarity.” this wasn’t, i should note, because of sloppiness or inattention. interpreting the forms andrelationships of ancient animals on the basis of often distorted and fragmentary evidence isclearly a tricky business. edward o. wilson has noted that if you took selected species ofmodern insects and presented them as burgess style fossils nobody would ever guess that theywere all from the same phylum, so different are their body plans. also instrumental in helpingrevisions were the discoveries of two further early cambrian sites, one in greenland and onein china, plus more scattered finds, which between them yielded many additional and oftenbetter specimens. the upshot is that the burgess fossils were found to be not so different after all.hallucigenia, it turned out, had been reconstructed upside down. its stilt like legs wereactually spikes along its back. peytoia, the weird creature that looked like a pineapple slice,was found to be not a distinct creature but merely part of a larger animal called anomalocaris.many of the burgess specimens have now been assigned to living phyla just where walcottput them in the first place. hallucigenia and some others are thought to be related toonychophora, a group of caterpillar like animals. others have been reclassified as precursorsof the modern annelids. in fact, says fortey, “there are relatively few cambrian designs thatare wholly novel. more often they turn out to be just interesting elaborations of well established designs.” as he wrote in his book life: “none was as strange as a present daybarnacle, nor as grotesque as a queen termite.” so the burgess shale specimens weren’t so spectacular after all. this made them, as forteyhas written, “no less interesting, or odd, just more explicable.” their weird body plans werejust a kind of youthful exuberance the evolutionary equivalent, as it were, of spiked hair andtongue studs. eventually the forms settled into a staid and stable middle age. but that still left the enduring question of where all these animals had come from howthey had suddenly appeared from out of nowhere. alas, it turns out the cambrian explosion may not have been quite so explosive as all that.the cambrian animals, it is now thought, were probably there all along, but were just toosmall to see. once again it was trilobites that provided the clue in particular that seeminglymystifying appearance of different types of trilobite in widely scattered locations around theglobe, all at more or less the same time. on the face of it, the sudden appearance of lots of fully formed but varied creatures wouldseem to enhance the miraculousness of the cambrian outburst, but in fact it did the opposite.it is one thing to have one well formed creature like a trilobite burst forth in isolation thatreally is a wonder but to have many of them, all distinct but clearly related, turning upsimultaneously in the fossil record in places as far apart as china and new york clearlysuggests that we are missing a big part of their history. there could be no stronger evidencethat they simply had to have a forebear some grandfather species that started the line in amuch earlier past. and the reason we haven’t found these earlier species, it is now thought, is that they weretoo tiny to be preserved. says fortey: “it isn’t necessary to be big to be a perfectlyfunctioning, complex organism. the sea swarms with tiny arthropods today that have left nofossil record.” he cites the little copepod, which numbers in the trillions in modern seas andclusters in shoals large enough to turn vast areas of the ocean black, and yet our totalknowledge of its ancestry is a single specimen found in the body of an ancient fossilized fish. “the cambrian explosion, if that’s the word for it, probably was more an increase in sizethan a sudden appearance of new body types,” fortey says. “and it could have happened quiteswiftly, so in that sense i suppose it was an explosion.” the idea is that just as mammalsbided their time for a hundred million years until the dinosaurs cleared off and then seeminglyburst forth in profusion all over the planet, so too perhaps the arthropods and other triploblastswaited in semimicroscopic anonymity for the dominant ediacaran organisms to have theirday. says fortey: “we know that mammals increased in size quite dramatically after thedinosaurs went though when i say quite abruptly i of course mean it in a geological sense.we’re still talking millions of years.” incidentally, reginald sprigg did eventually get a measure of overdue credit. one of themain early genera, spriggina, was named in his honor, as were several species, and the wholebecame known as the ediacaran fauna after the hills through which he had searched. by thistime, however, sprigg’s fossil hunting days were long over. after leaving geology he foundeda successful oil company and eventually retired to an estate in his beloved flinders range,where he created a wildlife reserve. he died in 1994 a rich man. 22 good bye to all thatwhen you consider it from a human perspective, and clearly it would be difficult forus to do otherwise, life is an odd thing. it couldn’t wait to get going, but then, having gottengoing, it seemed in very little hurry to move on. consider the lichen. lichens are just about the hardiest visible organisms on earth, butamong the least ambitious. they will grow happily enough in a sunny churchyard, but theyparticularly thrive in environments where no other organism would go on blowymountaintops and arctic wastes, wherever there is little but rock and rain and cold, and almostno competition. in areas of antarctica where virtually nothing else will grow, you can findvast expanses of lichen four hundred types of them adhering devotedly to every wind whipped rock. for a long time, people couldn’t understand how they did it. because lichens grew on barerock without evident nourishment or the production of seeds, many people educatedpeople believed they were stones caught in the process of becoming plants. “spontaneously,inorganic stone becomes living plant!” rejoiced one observer, a dr. homschuch, in 1819. closer inspection showed that lichens were more interesting than magical. they are in facta partnership between fungi and algae. the fungi excrete acids that dissolve the surface of therock, freeing minerals that the algae convert into food sufficient to sustain both. it is not avery exciting arrangement, but it is a conspicuously successful one. the world has more thantwenty thousand species of lichens. like most things that thrive in harsh environments, lichens are slow growing. it may take alichen more than half a century to attain the dimensions of a shirt button. those the size ofdinner plates, writes david attenborough, are therefore “likely to be hundreds if notthousands of years old.” it would be hard to imagine a less fulfilling existence. “they simplyexist,” attenborough adds, “testifying to the moving fact that life even at its simplest leveloccurs, apparently, just for its own sake.” it is easy to overlook this thought that life just is. as humans we are inclined to feel that lifemust have a point. we have plans and aspirations and desires. we want to take constantadvantage of all the intoxicating existence we’ve been endowed with. but what’s life to alichen? yet its impulse to exist, to be, is every bit as strong as ours arguably even stronger.if i were told that i had to spend decades being a furry growth on a rock in the woods, ibelieve i would lose the will to go on. lichens don’t. like virtually all living things, they willsuffer any hardship, endure any insult, for a moment’s additional existence. life, in short, justwants to be. but and here’s an interesting point for the most part it doesn’t want to bemuch. this is perhaps a little odd because life has had plenty of time to develop ambitions. if youimagine the 4,500 billion odd years of earth’s history compressed into a normal earthly day,then life begins very early, about 4a.m., with the rise of the first simple, single celled organisms, but then advances no further for the next sixteen hours. not until almost 8:30 inthe evening, with the day five sixths over, has earth anything to show the universe but arestless skin of microbes. then, finally, the first sea plants appear, followed twenty minuteslater by the first jellyfish and the enigmatic ediacaran fauna first seen by reginald sprigg inaustralia. at 9:04p.m. trilobites swim onto the scene, followed more or less immediately bythe shapely creatures of the burgess shale. just before 10p.m. plants begin to pop up on theland. soon after, with less than two hours left in the day, the first land creatures follow. thanks to ten minutes or so of balmy weather, by 10:24 the earth is covered in the greatcarboniferous forests whose residues give us all our coal, and the first winged insects areevident. dinosaurs plod onto the scene just before 11p.m. and hold sway for about three quarters of an hour. at twenty one minutes to midnight they vanish and the age of mammalsbegins. humans emerge one minute and seventeen seconds before midnight. the whole of ourrecorded history, on this scale, would be no more than a few seconds, a single human lifetimebarely an instant. throughout this greatly speeded up day continents slide about and bangtogether at a clip that seems positively reckless. mountains rise and melt away, ocean basinscome and go, ice sheets advance and withdraw. and throughout the whole, about three timesevery minute, somewhere on the planet there is a flashbulb pop of light marking the impact ofa manson sized meteor or one even larger. it’s a wonder that anything at all can survive insuch a pummeled and unsettled environment. in fact, not many things do for long. perhaps an even more effective way of grasping our extreme recentness as a part of this4.5 billion year old picture is to stretch your arms to their fullest extent and imagine thatwidth as the entire history of the earth. on this scale, according to john mcphee in basin andrange, the distance from the fingertips of one hand to the wrist of the other is precambrian.all of complex life is in one hand, “and in a single stroke with a medium grained nail file youcould eradicate human history.” fortunately, that moment hasn’t happened, but the chances are good that it will. i don’twish to interject a note of gloom just at this point, but the fact is that there is one otherextremely pertinent quality about life on earth: it goes extinct. quite regularly. for all thetrouble they take to assemble and preserve themselves, species crumple and die remarkablyroutinely. and the more complex they get, the more quickly they appear to go extinct. whichis perhaps one reason why so much of life isn’t terribly ambitious. so anytime life does something bold it is quite an event, and few occasions were moreeventful than when life moved on to the next stage in our narrative and came out of the sea. land was a formidable environment: hot, dry, bathed in intense ultraviolet radiation,lacking the buoyancy that makes movement in water comparatively effortless. to live onland, creatures had to undergo wholesale revisions of their anatomies. hold a fish at each endand it sags in the middle, its backbone too weak to support it. to survive out of water, marinecreatures needed to come up with new load bearing internal architecture not the sort ofadjustment that happens overnight. above all and most obviously, any land creature wouldhave to develop a way to take its oxygen directly from the air rather than filter it from water.these were not trivial challenges to overcome. on the other hand, there was a powerfulincentive to leave the water: it was getting dangerous down there. the slow fusion of thecontinents into a single landmass, pangaea, meant there was much, much less coastline thanformerly and thus much less coastal habitat. so competition was fierce. there was also an omnivorous and unsettling new type of predator on the scene, one so perfectly designed forattack that it has scarcely changed in all the long eons since its emergence: the shark. neverwould there be a more propitious time to find an alternative environment to water. plants began the process of land colonization about 450 million years ago, accompanied ofnecessity by tiny mites and other organisms that they needed to break down and recycle deadorganic matter on their behalf. larger animals took a little longer to emerge, but by about 400million years ago they were venturing out of the water, too. popular illustrations haveencouraged us to envision the first venturesome land dwellers as a kind of ambitious fish something like the modern mudskipper, which can hop from puddle to puddle duringdroughts or even as a fully formed amphibian. in fact, the first visible mobile residents ondry land were probably much more like modern wood lice, sometimes also known as pillbugsor sow bugs. these are the little bugs (crustaceans, in fact) that are commonly thrown intoconfusion when you upturn a rock or log. for those that learned to breathe oxygen from the air, times were good. oxygen levels inthe devonian and carboniferous periods, when terrestrial life first bloomed, were as high as35 percent (as opposed to nearer 20 percent now). this allowed animals to grow remarkablylarge remarkably quickly. and how, you may reasonably wonder, can scientists know what oxygen levels were likehundreds of millions of years ago? the answer lies in a slightly obscure but ingenious fieldknown as isotope geochemistry. the long ago seas of the carboniferous and devonianswarmed with tiny plankton that wrapped themselves inside tiny protective shells. then, asnow, the plankton created their shells by drawing oxygen from the atmosphere and combiningit with other elements (carbon especially) to form durable compounds such as calciumcarbonate. it’s the same chemical trick that goes on in (and is discussed elsewhere in relationto) the long term carbon cycle a process that doesn’t make for terribly exciting narrative butis vital for creating a livable planet. eventually in this process all the tiny organisms die and drift to the bottom of the sea,where they are slowly compressed into limestone. among the tiny atomic structures theplankton take to the grave with them are two very stable isotopes oxygen 16 and oxygen 18.(if you have forgotten what an isotope is, it doesn’t matter, though for the record it’s an atomwith an abnormal number of neutrons.) this is where the geochemists come in, for theisotopes accumulate at different rates depending on how much oxygen or carbon dioxide is inthe atmosphere at the time of their creation. by comparing these ancient ratios, thegeochemists can cunningly read conditions in the ancient world oxygen levels, air and oceantemperatures, the extent and timing of ice ages, and much else. by combining their isotopefindings with other fossil residues pollen levels and so on scientists can, with considerableconfidence, re create entire landscapes that no human eye ever saw. the principal reason oxygen levels were able to build up so robustly throughout the periodof early terrestrial life was that much of the world’s landscape was dominated by giant treeferns and vast swamps, which by their boggy nature disrupted the normal carbon recyclingprocess. instead of completely rotting down, falling fronds and other dead vegetative matteraccumulated in rich, wet sediments, which were eventually squeezed into the vast coal bedsthat sustain much economic activity even now. the heady levels of oxygen clearly encouraged outsized growth. the oldest indication of asurface animal yet found is a track left 350 million years ago by a millipede like creature on a rock in scotland. it was over three feet long. before the era was out some millipedes wouldreach lengths more than double that. with such creatures on the prowl, it is perhaps not surprising that insects in the periodevolved a trick that could keep them safely out of tongue shot: they learned to fly. some tookto this new means of locomotion with such uncanny facility that they haven’t changed theirtechniques in all the time since. then, as now, dragonflies could cruise at up to thirty fivemiles an hour, instantly stop, hover, fly backwards, and lift far more proportionately than anyhuman flying machine. “the u.s. air force,” one commentator has written, “has put them inwind tunnels to see how they do it, and despaired.” they, too, gorged on the rich air. incarboniferous forests dragonflies grew as big as ravens. trees and other vegetation likewiseattained outsized proportions. horsetails and tree ferns grew to heights of fifty feet, clubmosses to a hundred and thirty. the first terrestrial vertebrates which is to say, the first land animals from which wewould derive are something of a mystery. this is partly because of a shortage of relevantfossils, but partly also because of an idiosyncratic swede named erik jarvik whose oddinterpretations and secretive manner held back progress on this question for almost half acentury. jarvik was part of a team of scandinavian scholars who went to greenland in the1930s and 1940s looking for fossil fish. in particular they sought lobe finned fish of the typethat presumably were ancestral to us and all other walking creatures, known as tetrapods. most animals are tetrapods, and all living tetrapods have one thing in common: four limbsthat end in a maximum of five fingers or toes. dinosaurs, whales, birds, humans, even fish all are tetrapods, which clearly suggests they come from a single common ancestor. the clueto this ancestor, it was assumed, would be found in the devonian era, from about 400 millionyears ago. before that time nothing walked on land. after that time lots of things did. luckilythe team found just such a creature, a three foot long animal called an ichthyostega. theanalysis of the fossil fell to jarvik, who began his study in 1948 and kept at it for the nextforty eight years. unfortunately, jarvik refused to let anyone study his tetrapod. the world’spaleontologists had to be content with two sketchy interim papers in which jarvik noted thatthe creature had five fingers in each of four limbs, confirming its ancestral importance. jarvik died in 1998. after his death, other paleontologists eagerly examined the specimenand found that jarvik had severely miscounted the fingers and toes there were actually eighton each limb and failed to observe that the fish could not possibly have walked. thestructure of the fin was such that it would have collapsed under its own weight. needless tosay, this did not do a great deal to advance our understanding of the first land animals. todaythree early tetrapods are known and none has five digits. in short, we don’t know quite wherewe came from. but come we did, though reaching our present state of eminence has not of course alwaysbeen straightforward. since life on land began, it has consisted of four megadynasties, as theyare sometimes called. the first consisted of primitive, plodding but sometimes fairly heftyamphibians and reptiles. the best known animal of this age was the dimetrodon, a sail backed creature that is commonly confused with dinosaurs (including, i note, in a picturecaption in the carl sagan book comet). the dimetrodon was in fact a synapsid. so, onceupon a time, were we. synapsids were one of the four main divisions of early reptilian life,the others being anapsids, euryapsids, and diapsids. the names simply refer to the number andlocation of small holes to be found in the sides of their owners’ skulls. synapsids had one holein their lower temples; diapsids had two; euryapsids had a single hole higher up. over time, each of these principal groupings split into further subdivisions, of which someprospered and some faltered. anapsids gave rise to the turtles, which for a time, perhaps atouch improbably, appeared poised to predominate as the planet’s most advanced and deadlyspecies, before an evolutionary lurch let them settle for durability rather than dominance. thesynapsids divided into four streams, only one of which survived beyond the permian.happily, that was the stream we belonged to, and it evolved into a family of protomammalsknown as therapsids. these formed megadynasty 2. unfortunately for the therapsids, their cousins the diapsids were also productively evolving,in their case into dinosaurs (among other things), which gradually proved too much for thetherapsids. unable to compete head to head with these aggressive new creatures, thetherapsids by and large vanished from the record. a very few, however, evolved into small,furry, burrowing beings that bided their time for a very long while as little mammals. thebiggest of them grew no larger than a house cat, and most were no bigger than mice.eventually, this would prove their salvation, but they would have to wait nearly 150 millionyears for megadynasty 3, the age of dinosaurs, to come to an abrupt end and make room formegadynasty 4 and our own age of mammals. each of these massive transformations, as well as many smaller ones between and since,was dependent on that paradoxically important motor of progress: extinction. it is a curiousfact that on earth species death is, in the most literal sense, a way of life. no one knows howmany species of organisms have existed since life began. thirty billion is a commonly citedfigure, but the number has been put as high as 4,000 billion. whatever the actual total, 99.99percent of all species that have ever lived are no longer with us. “to a first approximation,” asdavid raup of the university of chicago likes to say, “all species are extinct.” for complexorganisms, the average lifespan of a species is only about four million years roughly aboutwhere we are now. extinction is always bad news for the victims, of course, but it appears to be a good thingfor a dynamic planet. “the alternative to extinction is stagnation,” says ian tattersall of theamerican museum of natural history, “and stagnation is seldom a good thing in any realm.”(i should perhaps note that we are speaking here of extinction as a natural, long term process.extinction brought about by human carelessness is another matter altogether.) crises in earth’s history are invariably associated with dramatic leaps afterward. the fall ofthe ediacaran fauna was followed by the creative outburst of the cambrian period. theordovician extinction of 440 million years ago cleared the oceans of a lot of immobile filterfeeders and, somehow, created conditions that favored darting fish and giant aquatic reptiles.these in turn were in an ideal position to send colonists onto dry land when another blowoutin the late devonian period gave life another sound shaking. and so it has gone at scatteredintervals through history. if most of these events hadn’t happened just as they did, just whenthey did, we almost certainly wouldn’t be here now. earth has seen five major extinction episodes in its time the ordovician, devonian,permian, triassic, and cretaceous, in that order and many smaller ones. the ordovician(440 million years ago) and devonian (365 million) each wiped out about 80 to 85 percent ofspecies. the triassic (210 million years ago) and cretaceous (65 million years) each wipedout 70 to 75 percent of species. but the real whopper was the permian extinction of about 245million years ago, which raised the curtain on the long age of the dinosaurs. in the permian, at least 95 percent of animals known from the fossil record check out, never to return. evenabout a third of insect species went the only occasion on which they were lost en masse. it isas close as we have ever come to total obliteration. “it was, truly, a mass extinction, a carnage of a magnitude that had never troubled the earthbefore,” says richard fortey. the permian event was particularly devastating to sea creatures.trilobites vanished altogether. clams and sea urchins nearly went. virtually all other marineorganisms were staggered. altogether, on land and in the water, it is thought that earth lost 52percent of its families that’s the level above genus and below order on the grand scale of life(the subject of the next chapter) and perhaps as many as 96 percent of all its species. itwould be a long time as much as eighty million years by one reckoning before speciestotals recovered. two points need to be kept in mind. first, these are all just informed guesses. estimates forthe number of animal species alive at the end of the permian range from as low as 45,000 toas high as 240,000. if you don’t know how many species were alive, you can hardly specifywith conviction the proportion that perished. moreover, we are talking about the death ofspecies, not individuals. for individuals the death toll could be much higher in many cases,practically total. the species that survived to the next phase of life’s lottery almost certainlyowe their existence to a few scarred and limping survivors. in between the big kill offs, there have also been many smaller, less well known extinctionepisodes the hemphillian, frasnian, famennian, rancholabrean, and a dozen or so others which were not so devastating to total species numbers, but often critically hit certainpopulations. grazing animals, including horses, were nearly wiped out in the hemphillianevent about five million years ago. horses declined to a single species, which appears sosporadically in the fossil record as to suggest that for a time it teetered on the brink ofoblivion. imagine a human history without horses, without grazing animals. in nearly every case, for both big extinctions and more modest ones, we have bewilderinglylittle idea of what the cause was. even after stripping out the more crackpot notions there arestill more theories for what caused the extinction events than there have been events. at leasttwo dozen potential culprits have been identified as causes or prime contributors: globalwarming, global cooling, changing sea levels, oxygen depletion of the seas (a conditionknown as anoxia), epidemics, giant leaks of methane gas from the seafloor, meteor and cometimpacts, runaway hurricanes of a type known as hypercanes, huge volcanic upwellings,catastrophic solar flares. this last is a particularly intriguing possibility. nobody knows how big solar flares can getbecause we have only been watching them since the beginning of the space age, but the sun isa mighty engine and its storms are commensurately enormous. a typical solar flare something we wouldn’t even notice on earth will release the energy equivalent of a billionhydrogen bombs and fling into space a hundred billion tons or so of murderous high energyparticles. the magnetosphere and atmosphere between them normally swat these back intospace or steer them safely toward the poles (where they produce the earth’s comely auroras),but it is thought that an unusually big blast, say a hundred times the typical flare, couldoverwhelm our ethereal defenses. the light show would be a glorious one, but it would almostcertainly kill a very high proportion of all that basked in its glow. moreover, and ratherchillingly, according to bruce tsurutani of the nasa jet propulsion laboratory, “it wouldleave no trace in history.” what all this leaves us with, as one researcher has put it, is “tons of conjecture and verylittle evidence.” cooling seems to be associated with at least three of the big extinctionevents the ordovician, devonian, and permian but beyond that little is agreed, includingwhether a particular episode happened swiftly or slowly. scientists can’t agree, for instance,whether the late devonian extinction the event that was followed by vertebrates movingonto the land happened over millions of years or thousands of years or in one lively day. one of the reasons it is so hard to produce convincing explanations for extinctions is that itis so very hard to exterminate life on a grand scale. as we have seen from the manson impact,you can receive a ferocious blow and still stage a full, if presumably somewhat wobbly,recovery. so why, out of all the thousands of impacts earth has endured, was the kt event sosingularly devastating? well, first itwas positively enormous. it struck with the force of 100million megatons. such an outburst is not easily imagined, but as james lawrence powell haspointed out, if you exploded one hiroshima sized bomb for every person alive on earth todayyou would still be about a billion bombs short of the size of the kt impact. but even thatalone may not have been enough to wipe out 70 percent of earth’s life, dinosaurs included. the kt meteor had the additional advantage advantage if you are a mammal, that is that it landed in a shallow sea just ten meters deep, probably at just the right angle, at a timewhen oxygen levels were 10 percent higher than at present and so the world was morecombustible. above all the floor of the sea where it landed was made of rock rich in sulfur.the result was an impact that turned an area of seafloor the size of belgium into aerosols ofsulfuric acid. for months afterward, the earth was subjected to rains acid enough to burn skin. in a sense, an even greater question than that of what wiped out 70 percent of the speciesthat were existing at the time is how did the remaining 30 percent survive? why was the eventso irremediably devastating to every single dinosaur that existed, while other reptiles, likesnakes and crocodiles, passed through unimpeded? so far as we can tell no species of toad,newt, salamander, or other amphibian went extinct in north america. “why should thesedelicate creatures have emerged unscathed from such an unparalleled disaster?” asks timflannery in his fascinating prehistory of america, eternal frontier. in the seas it was much the same story. all the ammonites vanished, but their cousins thenautiloids, who lived similar lifestyles, swam on. among plankton, some species werepractically wiped out 92 percent of foraminiferans, for instance while other organisms likediatoms, designed to a similar plan and living alongside, were comparatively unscathed. these are difficult inconsistencies. as richard fortey observes: “somehow it does notseem satisfying just to call them ‘lucky ones’ and leave it at that.” if, as seems entirely likely,the event was followed by months of dark and choking smoke, then many of the insectsurvivors become difficult to account for. “some insects, like beetles,” fortey notes, “couldlive on wood or other things lying around. but what about those like bees that navigate bysunlight and need pollen? explaining their survival isn’t so easy.” above all, there are the corals. corals require algae to survive and algae require sunlight,and both together require steady minimum temperatures. much publicity has been given in thelast few years to corals dying from changes in sea temperature of only a degree or so. if theyare that vulnerable to small changes, how did they survive the long impact winter? there are also many hard to explain regional variations. extinctions seem to have been farless severe in the southern hemisphere than the northern. new zealand in particular appears to have come through largely unscathed even though it had almost no burrowing creatures. evenits vegetation was overwhelmingly spared, and yet the scale of conflagration elsewheresuggests that devastation was global. in short, there is just a great deal we don’t know. some animals absolutely prospered including, a little surprisingly, the turtles once again.as flannery notes, the period immediately after the dinosaur extinction could well be knownas the age of turtles. sixteen species survived in north america and three more came intoexistence soon after. clearly it helped to be at home in water. the kt impact wiped out almost 90 percent ofland based species but only 10 percent of those living in fresh water. water obviously offeredprotection against heat and flame, but also presumably provided more sustenance in the leanperiod that followed. all the land based animals that survived had a habit of retreating to asafer environment during times of danger into water or underground either of whichwould have provided considerable shelter against the ravages without. animals thatscavenged for a living would also have enjoyed an advantage. lizards were, and are, largelyimpervious to the bacteria in rotting carcasses. indeed, often they are positively drawn to it,and for a long while there were clearly a lot of putrid carcasses about. it is often wrongly stated that only small animals survived the kt event. in fact, among thesurvivors were crocodiles, which were not just large but three times larger than they are today.but on the whole, it is true, most of the survivors were small and furtive. indeed, with theworld dark and hostile, it was a perfect time to be small, warm blooded, nocturnal, flexible indiet, and cautious by nature the very qualities that distinguished our mammalian forebears.had our evolution been more advanced, we would probably have been wiped out. instead,mammals found themselves in a world to which they were as well suited as anything alive. however, it wasn’t as if mammals swarmed forward to fill every niche. “evolution mayabhor a vacuum,” wrote the paleobiologist steven m. stanley, “but it often takes a long timeto fill it.” for perhaps as many as ten million years mammals remained cautiously small. inthe early tertiary, if you were the size of a bobcat you could be king. but once they got going, mammals expanded prodigiously sometimes to an almostpreposterous degree. for a time, there were guinea pigs the size of rhinos and rhinos the sizeof a two story house. wherever there was a vacancy in the predatory chain, mammals rose(often literally) to fill it. early members of the raccoon family migrated to south america,discovered a vacancy, and evolved into creatures the size and ferocity of bears. birds, too,prospered disproportionately. for millions of years, a gigantic, flightless, carnivorous birdcalled titanis was possibly the most ferocious creature in north america. certainly it was themost daunting bird that ever lived. it stood ten feet high, weighed over eight hundred pounds,and had a beak that could tear the head off pretty much anything that irked it. its familysurvived in formidable fashion for fifty million years, yet until a skeleton was discovered inflorida in 1963, we had no idea that it had ever existed. which brings us to another reason for our uncertainty about extinctions: the paltriness ofthe fossil record. we have touched already on the unlikelihood of any set of bones becomingfossilized, but the record is actually worse than you might think. consider dinosaurs.museums give the impression that we have a global abundance of dinosaur fossils. in fact,overwhelmingly museum displays are artificial. the giant diplodocus that dominates theentrance hall of the natural history museum in london and has delighted and informedgenerations of visitors is made of plaster built in 1903 in pittsburgh and presented to the museum by andrew carnegie. the entrance hall of the american museum of natural historyin new york is dominated by an even grander tableau: a skeleton of a large barosaurusdefending her baby from attack by a darting and toothy allosaurus. it is a wonderfullyimpressive display the barosaurus rises perhaps thirty feet toward the high ceiling but alsoentirely fake. every one of the several hundred bones in the display is a cast. visit almost anylarge natural history museum in the world in paris, vienna, frankfurt, buenos aires,mexico city and what will greet you are antique models, not ancient bones. the fact is, we don’t really know a great deal about the dinosaurs. for the whole of the ageof dinosaurs, fewer than a thousand species have been identified (almost half of them knownfrom a single specimen), which is about a quarter of the number of mammal species alivenow. dinosaurs, bear in mind, ruled the earth for roughly three times as long as mammalshave, so either dinosaurs were remarkably unproductive of species or we have barelyscratched the surface (to use an irresistibly apt cliché). for millions of years through the age of dinosaurs not a single fossil has yet been found.even for the period of the late cretaceous the most studied prehistoric period there is,thanks to our long interest in dinosaurs and their extinction some three quarters of allspecies that lived may yet be undiscovered. animals bulkier than the diplodocus or moreforbidding than tyrannosaurus may have roamed the earth in the thousands, and we maynever know it. until very recently everything known about the dinosaurs of this period camefrom only about three hundred specimens representing just sixteen species. the scantiness ofthe record led to the widespread belief that dinosaurs were on their way out already when thekt impact occurred. in the late 1980s a paleontologist from the milwaukee public museum, peter sheehan,decided to conduct an experiment. using two hundred volunteers, he made a painstakingcensus of a well defined, but also well picked over, area of the famous hell creek formationin montana. sifting meticulously, the volunteers collected every last tooth and vertebra andchip of bone everything that had been overlooked by previous diggers. the work took threeyears. when finished they found that they had more than tripled the global total of dinosaurfossils from the late cretaceous. the survey established that dinosaurs remained numerousright up to the time of the kt impact. “there is no reason to believe that the dinosaurs weredying out gradually during the last three million years of the cretaceous,” sheehan reported. we are so used to the notion of our own inevitability as life’s dominant species that it ishard to grasp that we are here only because of timely extraterrestrial bangs and other randomflukes. the one thing we have in common with all other living things is that for nearly fourbillion years our ancestors have managed to slip through a series of closing doors every timewe needed them to. stephen jay gould expressed it succinctly in a well known line: “humansare here today because our particular line never fractured never once at any of the billionpoints that could have erased us from history.” we started this chapter with three points: life wants to be; life doesn’t always want to bemuch; life from time to time goes extinct. to this we may add a fourth: life goes on. andoften, as we shall see, it goes on in ways that are decidedly amazing. 23 the richness of beinghere and there in the natural history museum in london, built into recesses along theunderlit corridors or standing between glass cases of minerals and ostrich eggs and a centuryor so of other productive clutter, are secret doors at least secret in the sense that there isnothing about them to attract the visitor’s notice. occasionally you might see someone withthe distracted manner and interestingly willful hair that mark the scholar emerge from one ofthe doors and hasten down a corridor, probably to disappear through another door a littlefurther on, but this is a relatively rare event. for the most part the doors stay shut, giving nohint that beyond them exists another a parallel natural history museum as vast as, and inmany ways more wonderful than, the one the public knows and adores. the natural history museum contains some seventy million objects from every realm oflife and every corner of the planet, with another hundred thousand or so added to thecollection each year, but it is really only behind the scenes that you get a sense of what atreasure house this is. in cupboards and cabinets and long rooms full of close packed shelvesare kept tens of thousands of pickled animals in bottles, millions of insects pinned to squaresof card, drawers of shiny mollusks, bones of dinosaurs, skulls of early humans, endlessfolders of neatly pressed plants. it is a little like wandering through darwin’s brain. the spiritroom alone holds fifteen miles of shelving containing jar upon jar of animals preserved inmethylated spirit. back here are specimens collected by joseph banks in australia, alexander von humboldtin amazonia, darwin on the beagle voyage, and much else that is either very rare orhistorically important or both. many people would love to get their hands on these things. afew actually have. in 1954 the museum acquired an outstanding ornithological collection fromthe estate of a devoted collector named richard meinertzhagen, author of birds of arabia,among other scholarly works. meinertzhagen had been a faithful attendee of the museum foryears, coming almost daily to take notes for the production of his books and monographs.when the crates arrived, the curators excitedly jimmied them open to see what they had beenleft and were surprised, to put it mildly, to discover that a very large number of specimensbore the museum’s own labels. mr. meinertzhagen, it turned out, had been helping himself totheir collections for years. it also explained his habit of wearing a large overcoat even duringwarm weather. a few years later a charming old regular in the mollusks department “quite a distinguishedgentleman,” i was told was caught inserting valued seashells into the hollow legs of hiszimmer frame. “i don’t suppose there’s anything in here that somebody somewhere doesn’t covet,”richard fortey said with a thoughtful air as he gave me a tour of the beguiling world that isthe behind the scenes part of the museum. we wandered through a confusion of departmentswhere people sat at large tables doing intent, investigative things with arthropods and palm fronds and boxes of yellowed bones. everywhere there was an air of unhurried thoroughness,of people being engaged in a gigantic endeavor that could never be completed and mustn’t berushed. in 1967, i had read, the museum issued its report on the john murray expedition, anindian ocean survey, forty four years after the expedition had concluded. this is a worldwhere things move at their own pace, including a tiny lift fortey and i shared with a scholarlylooking elderly man with whom fortey chatted genially and familiarly as we proceededupwards at about the rate that sediments are laid down. when the man departed, fortey said to me: “that was a very nice chap named normanwho’s spent forty two years studying one species of plant, st. john’s wort. he retired in 1989,but he still comes in every week.” “how do you spend forty two years on one species of plant?” i asked. “it’s remarkable, isn’t it?” fortey agreed. he thought for a moment. “he’s very thoroughapparently.” the lift door opened to reveal a bricked over opening. fortey lookedconfounded. “that’s very strange,” he said. “that used to be botany back there.” he puncheda button for another floor, and we found our way at length to botany by means of backstaircases and discreet trespass through yet more departments where investigators toiledlovingly over once living objects. and so it was that i was introduced to len ellis and thequiet world of bryophytes mosses to the rest of us. when emerson poetically noted that mosses favor the north sides of trees (“the moss uponthe forest bark, was pole star when the night was dark”) he really meant lichens, for in thenineteenth century mosses and lichens weren’t distinguished. true mosses aren’t actuallyfussy about where they grow, so they are no good as natural compasses. in fact, mosses aren’tactually much good for anything. “perhaps no great group of plants has so few uses,commercial or economic, as the mosses,” wrote henry s. conard, perhaps just a touch sadly,in how to know the mosses and liverworts, published in 1956 and still to be found on manylibrary shelves as almost the only attempt to popularize the subject. they are, however, prolific. even with lichens removed, bryophytes is a busy realm, withover ten thousand species contained within some seven hundred genera. the plump andstately moss flora of britain and ireland by a. j. e. smith runs to seven hundred pages, andbritain and ireland are by no means outstandingly mossy places. “the tropics are where youfind the variety,” len ellis told me. a quiet, spare man, he has been at the natural historymuseum for twenty seven years and curator of the department since 1990. “you can go outinto a place like the rain forests of malaysia and find new varieties with relative ease. i didthat myself not long ago. i looked down and there was a species that had never beenrecorded.” “so we don’t know how many species are still to be discovered?” “oh, no. no idea.” you might not think there would be that many people in the world prepared to devotelifetimes to the study of something so inescapably low key, but in fact moss people number inthe hundreds and they feel very strongly about their subject. “oh, yes,” ellis told me, “themeetings can get very lively at times.” i asked him for an example of controversy. “well, here’s one inflicted on us by one of your countrymen,” he said, smiling lightly, andopened a hefty reference work containing illustrations of mosses whose most notablecharacteristic to the uninstructed eye was their uncanny similarity one to another. “that,” hesaid, tapping a moss, “used to be one genus, drepanocladus. now it’s been reorganized intothree: drepanocladus, wamstorfia, and hamatacoulis.” “and did that lead to blows?” i asked perhaps a touch hopefully. “well, it made sense. it made perfect sense. but it meant a lot of reordering of collectionsand it put all the books out of date for a time, so there was a bit of, you know, grumbling.” mosses offer mysteries as well, he told me. one famous case famous to moss peopleanyway involved a retiring type called hyophila stanfordensis, which was discovered on thecampus of stanford university in california and later also found growing beside a path incornwall, on the southwest tip of england, but has never been encountered anywhere inbetween. how it came to exist in two such unconnected locations is anybody’s guess. “it’snow known as hennediella stanfordensis,” ellis said. “another revision.” we nodded thoughtfully. when a new moss is found it must be compared with all other mosses to make sure that ithasn’t been recorded already. then a formal description must be written and illustrationsprepared and the result published in a respectable journal. the whole process seldom takesless than six months. the twentieth century was not a great age for moss taxonomy. much ofthe century’s work was devoted to untangling the confusions and duplications left behind bythe nineteenth century. that was the golden age of moss collecting. (you may recall that charles lyell’s fatherwas a great moss man.) one aptly named englishman, george hunt, hunted british mosses soassiduously that he probably contributed to the extinction of several species. but it is thanksto such efforts that len ellis’s collection is one of the world’s most comprehensive. all780,000 of his specimens are pressed into large folded sheets of heavy paper, some very oldand covered with spidery victorian script. some, for all we knew, might have been in thehand of robert brown, the great victorian botanist, unveiler of brownian motion and thenucleus of cells, who founded and ran the museum’s botany department for its first thirty oneyears until his death in 1858. all the specimens are kept in lustrous old mahogany cabinets sostrikingly fine that i remarked upon them. “oh, those were sir joseph banks’s, from his house in soho square,” ellis said casually, asif identifying a recent purchase from ikea. “he had them built to hold his specimens from theendeavour voyage.” he regarded the cabinets thoughtfully, as if for the first time in a longwhile. “i don’t know howwe ended up with them in bryology,” he added. this was an amazing disclosure. joseph banks was england’s greatest botanist, and theendeavour voyage that is the one on which captain cook charted the 1769 transit of venusand claimed australia for the crown, among rather a lot else was the greatest botanicalexpedition in history. banks paid £10,000, about $1 million in today’s money, to bringhimself and a party of nine others a naturalist, a secretary, three artists, and four servants on the three year adventure around the world. goodness knows what the bluff captain cook made of such a velvety and pampered assemblage, but he seems to have liked banks wellenough and could not but admire his talents in botany a feeling shared by posterity. never before or since has a botanical party enjoyed greater triumphs. partly it was becausethe voyage took in so many new or little known places tierra del fuego, tahiti, newzealand, australia, new guinea but mostly it was because banks was such an astute andinventive collector. even when unable to go ashore at rio de janeiro because of a quarantine,he sifted through a bale of fodder sent for the ship’s livestock and made new discoveries.nothing, it seems, escaped his notice. altogether he brought back thirty thousand plantspecimens, including fourteen hundred not seen before enough to increase by about aquarter the number of known plants in the world. but banks’s grand cache was only part of the total haul in what was an almost absurdlyacquisitive age. plant collecting in the eighteenth century became a kind of internationalmania. glory and wealth alike awaited those who could find new species, and botanists andadventurers went to the most incredible lengths to satisfy the world’s craving for horticulturalnovelty. thomas nuttall, the man who named the wisteria after caspar wistar, came toamerica as an uneducated printer but discovered a passion for plants and walked halfwayacross the country and back again, collecting hundreds of growing things never seen before.john fraser, for whom is named the fraser fir, spent years in the wilderness collecting onbehalf of catherine the great and emerged at length to find that russia had a new czar whothought he was mad and refused to honor his contract. fraser took everything to chelsea,where he opened a nursery and made a handsome living selling rhododendrons, azaleas,magnolias, virginia creepers, asters, and other colonial exotica to a delighted english gentry. huge sums could be made with the right finds. john lyon, an amateur botanist, spent twohard and dangerous years collecting specimens, but cleared almost $200,000 in today’smoney for his efforts. many, however, just did it for the love of botany. nuttall gave most ofwhat he found to the liverpool botanic gardens. eventually he became director of harvard’sbotanic garden and author of the encyclopedicgenera of north american plants (which henot only wrote but also largely typeset). and that was just plants. there was also all the fauna of the new worlds kangaroos, kiwis,raccoons, bobcats, mosquitoes, and other curious forms beyond imagining. the volume of lifeon earth was seemingly infinite, as jonathan swift noted in some famous lines: so, naturalists observe, a flea hath smaller fleas that on him prey; and these have smaller still to bite ’em; and so proceed ad infinitum. all this new information needed to be filed, ordered, and compared with what was known.the world was desperate for a workable system of classification. fortunately there was a manin sweden who stood ready to provide it. his name was carl linné (later changed, with permission, to the more aristocraticvonlinné), but he is remembered now by the latinized form carolus linnaeus. he was born in1707 in the village of råshult in southern sweden, the son of a poor but ambitious lutherancurate, and was such a sluggish student that his exasperated father apprenticed him (or, by some accounts, nearly apprenticed him) to a cobbler. appalled at the prospect of spending alifetime banging tacks into leather, young linné begged for another chance, which wasgranted, and he never thereafter wavered from academic distinction. he studied medicine insweden and holland, though his passion became the natural world. in the early 1730s, still inhis twenties, he began to produce catalogues of the world’s plant and animal species, using asystem of his own devising, and gradually his fame grew. rarely has a man been more comfortable with his own greatness. he spent much of hisleisure time penning long and flattering portraits of himself, declaring that there had never“been a greater botanist or zoologist,” and that his system of classification was “the greatestachievement in the realm of science.” modestly he suggested that his gravestone should bearthe inscription princeps botanicorum, “prince of botanists.” it was never wise to question hisgenerous self assessments. those who did so were apt to find they had weeds named afterthem. linnaeus’s other striking quality was an abiding at times, one might say, a feverish preoccupation with sex. he was particularly struck by the similarity between certain bivalvesand the female pudenda. to the parts of one species of clam he gave the names vulva, labia,pubes, anus, and hymen. he grouped plants by the nature of their reproductive organs andendowed them with an arrestingly anthropomorphic amorousness. his descriptions of flowersand their behavior are full of references to “promiscuous intercourse,” “barren concubines,”and “the bridal bed.” in spring, he wrote in one oft quoted passage: love comes even to the plants. males and females . . . hold their nuptials . . . showing by their sexual organs which are males, which females. the flowers’ leaves serve as a bridal bed, which the creator has so gloriously arranged, adorned with such noble bed curtains, and perfumed with so many soft scents that the bridegroom with his bride might there celebrate their nuptials with so much the greater solemnity. when the bed has thus been made ready, then is the time for the bridegroom to embrace his beloved bride and surrender himself to her. he named one genus of plants clitoria. not surprisingly, many people thought him strange.but his system of classification was irresistible. before linnaeus, plants were given namesthat were expansively descriptive. the common ground cherry was called physalis amnoramosissime ramis angulosis glabris foliis dentoserratis. linnaeus lopped it back to physalisangulata, which name it still uses. the plant world was equally disordered by inconsistenciesof naming. a botanist could not be sure ifrosa sylvestris alba cum rubore, folio glabro wasthe same plant that others called rosa sylvestris inodora seu canina. linnaeus solved thepuzzlement by calling it simply rosa canina. to make these excisions useful and agreeable toall required much more than simply being decisive. it required an instinct a genius, in fact for spotting the salient qualities of a species. the linnaean system is so well established that we can hardly imagine an alternative, butbefore linnaeus, systems of classification were often highly whimsical. animals might becategorized by whether they were wild or domesticated, terrestrial or aquatic, large or small,even whether they were thought handsome and noble or of no consequence. buffon arrangedhis animals by their utility to man. anatomical considerations barely came into it. linnaeus made it his life’s work to rectify this deficiency by classifying all that was alive according toits physical attributes. taxonomy which is to say the science of classification has neverlooked back. it all took time, of course. the first edition of his great systema naturae in 1735 was justfourteen pages long. but it grew and grew until by the twelfth edition the last that linnaeuswould live to see it extended to three volumes and 2,300 pages. in the end he named orrecorded some 13,000 species of plant and animal. other works were more comprehensive john ray’s three volume historia generalis plantarum in england, completed a generationearlier, covered no fewer than 18,625 species of plants alone but what linnaeus had that noone else could touch were consistency, order, simplicity, and timeliness. though his workdates from the 1730s, it didn’t become widely known in england until the 1760s, just in timeto make linnaeus a kind of father figure to british naturalists. nowhere was his systemembraced with greater enthusiasm (which is why, for one thing, the linnaean society has itshome in london and not stockholm). linnaeus was not flawless. he made room for mythical beasts and “monstrous humans”whose descriptions he gullibly accepted from seamen and other imaginative travelers. amongthese were a wild man, homo ferus, who walked on all fours and had not yet mastered the artof speech, and homo caudatus, “man with a tail.” but then it was, as we should not forget, analtogether more credulous age. even the great joseph banks took a keen and believing interestin a series of reported sightings of mermaids off the scottish coast at the end of the eighteenthcentury. for the most part, however, linnaeus’s lapses were offset by sound and oftenbrilliant taxonomy. among other accomplishments, he saw that whales belonged with cows,mice, and other common terrestrial animals in the order quadrupedia (later changed tomammalia), which no one had done before. in the beginning, linnaeus intended only to give each plant a genus name and a number convolvulus 1, convolvulus 2,and so on but soon realized that that was unsatisfactory andhit on the binomial arrangement that remains at the heart of the system to this day. theintention originally was to use the binomial system for everything rocks, minerals, diseases,winds, whatever existed in nature. not everyone embraced the system warmly. many weredisturbed by its tendency toward indelicacy, which was slightly ironic as before linnaeus thecommon names of many plants and animals had been heartily vulgar. the dandelion was longpopularly known as the “pissabed” because of its supposed diuretic properties, and othernames in everyday use included mare’s fart, naked ladies, twitch ballock, hound’s piss, openarse, and bum towel. one or two of these earthy appellations may unwittingly survive inenglish yet. the “maidenhair” in maidenhair moss, for instance, does not refer to the hair onthe maiden’s head. at all events, it had long been felt that the natural sciences would beappreciably dignified by a dose of classical renaming, so there was a certain dismay indiscovering that the self appointed prince of botany had sprinkled his texts with suchdesignations asclitoria, fornicata, andvulva. over the years many of these were quietly dropped (though not all: the common slipperlimpet still answers on formal occasions to crepidula fornicata) and many other refinementsintroduced as the needs of the natural sciences grew more specialized. in particular the systemwas bolstered by the gradual introduction of additional hierarchies.genus (pluralgenera) andspecies had been employed by naturalists for over a hundred years before linnaeus, andorder, class, and family in their biological senses all came into use in the 1750s and 1760s.but phylum wasn’t coined until 1876 (by the german ernst haeckel), and family and order were treated as interchangeable until early in the twentieth century. for a time zoologists usedfamily where botanists placed order, to the occasional confusion of nearly everyone.1 linnaeus had divided the animal world into six categories: mammals, reptiles, birds, fishes,insects, and “vermes,” or worms, for everything that didn’t fit into the first five. from theoutset it was evident that putting lobsters and shrimp into the same category as worms wasunsatisfactory, and various new categories such as mollusca and crustacea were created.unfortunately these new classifications were not uniformly applied from nation to nation. inan attempt to reestablish order, the british in 1842 proclaimed a new set of rules called thestricklandian code, but the french saw this as highhanded, and the société zoologiquecountered with its own conflicting code. meanwhile, the american ornithological society, forobscure reasons, decided to use the 1758 edition of systema naturae as the basis for all itsnaming, rather than the 1766 edition used elsewhere, which meant that many american birdsspent the nineteenth century logged in different genera from their avian cousins in europe.not until 1902, at an early meeting of the international congress of zoology, did naturalistsbegin at last to show a spirit of compromise and adopt a universal code. taxonomy is described sometimes as a science and sometimes as an art, but really it’s abattleground. even today there is more disorder in the system than most people realize. takethe category of the phylum, the division that describes the basic body plans of all organisms.a few phyla are generally well known, such as mollusks (the home of clams and snails),arthropods (insects and crustaceans), and chordates (us and all other animals with a backboneor protobackbone), though things then move swiftly in the direction of obscurity. among thelatter we might list gnathostomulida (marine worms), cnidaria (jellyfish, medusae,anemones, and corals), and the delicate priapulida (or little “penis worms”). familiar or not,these are elemental divisions. yet there is surprisingly little agreement on how many phylathere are or ought to be. most biologists fix the total at about thirty, but some opt for a numberin the low twenties, while edward o. wilson in the diversity of life puts the number at asurprisingly robust eighty nine. it depends on where you decide to make your divisions whether you are a “lumper” or a “splitter,” as they say in the biological world. at the more workaday level of species, the possibilities for disagreements are even greater.whether a species of grass should be called aegilops incurva, aegilops incurvata, or aegilopsovata may not be a matter that would stir many nonbotanists to passion, but it can be a sourceof very lively heat in the right quarters. the problem is that there are five thousand species ofgrass and many of them look awfully alike even to people who know grass. in consequence,some species have been found and named at least twenty times, and there are hardly any, itappears, that haven’t been independently identified at least twice. the two volume manual ofthe grasses of the united states devotes two hundred closely typeset pages to sorting out allthe synonymies, as the biological world refers to its inadvertent but quite commonduplications. and that is just for the grasses of a single country. to deal with disagreements on the global stage, a body known as the internationalassociation for plant taxonomy arbitrates on questions of priority and duplication. at1 to illustrate, humans are in the domain eucarya, in the kingdom animalia, in the phylum chordata, in thesubphylum vertebrata, in the class mammalia, in the order primates, in the family hominidae, in the genus homo,in the species sapiens. (the convention, i'm informed, is to italicize genus and species names, but not those ofhigher divisions.) some taxonomists employ further subdivisions: tribe, suborder, infraorder, parvorder, andmore. intervals it hands down decrees, declaring that zauschneria californica (a common plant inrock gardens) is to be known henceforth as epilobium canum or that aglaothamniontenuissimum may now be regarded as conspecific with aglaothamnion byssoides, but notwithaglaothamnion pseudobyssoides. normally these are small matters of tidying up thatattract little notice, but when they touch on beloved garden plants, as they sometimes do,shrieks of outrage inevitably follow. in the late 1980s the common chrysanthemum wasbanished (on apparently sound scientific principles) from the genus of the same name andrelegated to the comparatively drab and undesirable world of the genus dendranthema. chrysanthemum breeders are a proud and numerous lot, and they protested to the real ifimprobable sounding committee on spermatophyta. (there are also committees forpteridophyta, bryophyta, and fungi, among others, all reporting to an executive called therapporteur général; this is truly an institution to cherish.) although the rules of nomenclatureare supposed to be rigidly applied, botanists are not indifferent to sentiment, and in 1995 thedecision was reversed. similar adjudications have saved petunias, euonymus, and a popularspecies of amaryllis from demotion, but not many species of geraniums, which some yearsago were transferred, amid howls, to the genus pelargonium. the disputes are entertaininglysurveyed in charles elliott’s the potting shed papers. disputes and reorderings of much the same type can be found in all the other realms of theliving, so keeping an overall tally is not nearly as straightforward a matter as you mightsuppose. in consequence, the rather amazing fact is that we don’t have the faintest idea “noteven to the nearest order of magnitude,” in the words of edward o. wilson of the number ofthings that live on our planet. estimates range from 3 million to 200 million. moreextraordinary still, according to a report in the economist, as much as 97 percent of theworld’s plant and animal species may still await discovery. of the organisms that we do know about, more than 99 in 100 are only sketchilydescribed “a scientific name, a handful of specimens in a museum, and a few scraps ofdescription in scientific journals” is how wilson describes the state of our knowledge. in thediversity of life, he estimated the number of known species of all types plants, insects,microbes, algae, everything at 1.4 million, but added that that was just a guess. otherauthorities have put the number of known species slightly higher, at around 1.5 million to 1.8million, but there is no central registry of these things, so nowhere to check numbers. in short,the remarkable position we find ourselves in is that we don’t actually know what we actuallyknow. in principle you ought to be able to go to experts in each area of specialization, ask howmany species there are in their fields, then add the totals. many people have in fact done so.the problem is that seldom do any two come up with matching figures. some sources put thenumber of known types of fungi at 70,000, others at 100,000 nearly half as many again. youcan find confident assertions that the number of described earthworm species is 4,000 andequally confident assertions that the figure is 12,000. for insects, the numbers run from750,000 to 950,000 species. these are, you understand, supposedly the known number ofspecies. for plants, the commonly accepted numbers range from 248,000 to 265,000. thatmay not seem too vast a discrepancy, but it’s more than twenty times the number of floweringplants in the whole of north america. putting things in order is not the easiest of tasks. in the early 1960s, colin groves of theaustralian national university began a systematic survey of the 250 plus known species ofprimate. oftentimes it turned out that the same species had been described more than once  sometimes several times without any of the discoverers realizing that they were dealing withan animal that was already known to science. it took groves four decades to untangleeverything, and that was with a comparatively small group of easily distinguished, generallynoncontroversial creatures. goodness knows what the results would be if anyone attempted asimilar exercise with the planet’s estimated 20,000 types of lichens, 50,000 species ofmollusk, or 400,000 plus beetles. what is certain is that there is a great deal of life out there, though the actual quantities arenecessarily estimates based on extrapolations sometimes exceedingly expansiveextrapolations. in a well known exercise in the 1980s, terry erwin of the smithsonianinstitution saturated a stand of nineteen rain forest trees in panama with an insecticide fog,then collected everything that fell into his nets from the canopy. among his haul (actuallyhauls, since he repeated the experiment seasonally to make sure he caught migrant species)were 1,200 types of beetle. based on the distribution of beetles elsewhere, the number ofother tree species in the forest, the number of forests in the world, the number of other insecttypes, and so on up a long chain of variables, he estimated a figure of 30 million species ofinsects for the entire planet a figure he later said was too conservative. others using thesame or similar data have come up with figures of 13 million, 80 million, or 100 millioninsect types, underlining the conclusion that however carefully arrived at, such figuresinevitably owe at least as much to supposition as to science. according to the wall street journal, the world has “about 10,000 active taxonomists” not a great number when you consider how much there is to be recorded. but, the journaladds, because of the cost (about $2,000 per species) and paperwork, only about fifteenthousand new species of all types are logged per year. “it’s not a biodiversity crisis, it’s a taxonomist crisis!” barks koen maes, belgian bornhead of invertebrates at the kenyan national museum in nairobi, whom i met briefly on avisit to the country in the autumn of 2002. there were no specialized taxonomists in thewhole of africa, he told me. “there was one in the ivory coast, but i think he has retired,” hesaid. it takes eight to ten years to train a taxonomist, but none are coming along in africa.“they are the real fossils,” maes added. he himself was to be let go at the end of the year, hesaid. after seven years in kenya, his contract was not being renewed. “no funds,” maesexplained. writing in the journal nature last year, the british biologist g. h. godfray noted that thereis a chronic “lack of prestige and resources” for taxonomists everywhere. in consequence,“many species are being described poorly in isolated publications, with no attempt to relate anew taxon2to existing species and classifications.” moreover, much of taxonomists’ time istaken up not with describing new species but simply with sorting out old ones. many,according to godfray, “spend most of their career trying to interpret the work of nineteenth century systematicists: deconstructing their often inadequate published descriptions orscouring the world’s museums for type material that is often in very poor condition.” godfrayparticularly stresses the absence of attention being paid to the systematizing possibilities ofthe internet. the fact is that taxonomy by and large is still quaintly wedded to paper.2 the formal word for a zoological category, such as phylum or genus. the plural is taxa. in an attempt to haul things into the modern age, in 2001 kevin kelly, cofounder of wiredmagazine, launched an enterprise called the all species foundation with the aim of findingevery living organism and recording it on a database. the cost of such an exercise has beenestimated at anywhere from $2 billion to as much as $50 billion. as of the spring of 2002, thefoundation had just $1.2 million in funds and four full time employees. if, as the numberssuggest, we have perhaps 100 million species of insects yet to find, and if our rates ofdiscovery continue at the present pace, we should have a definitive total for insects in a littleover fifteen thousand years. the rest of the animal kingdom may take a little longer. so why do we know as little as we do? there are nearly as many reasons as there areanimals left to count, but here are a few of the principal causes: most living things are small and easily overlooked.in practical terms, this is not always abad thing. you might not slumber quite so contentedly if you were aware that your mattress ishome to perhaps two million microscopic mites, which come out in the wee hours to sup onyour sebaceous oils and feast on all those lovely, crunchy flakes of skin that you shed as youdoze and toss. your pillow alone may be home to forty thousand of them. (to them your headis just one large oily bon bon.) and don’t think a clean pillowcase will make a difference. tosomething on the scale of bed mites, the weave of the tightest human fabric looks like ship’srigging. indeed, if your pillow is six years old which is apparently about the average age fora pillow it has been estimated that one tenth of its weight will be made up of “sloughedskin, living mites, dead mites and mite dung,” to quote the man who did the measuring, dr.john maunder of the british medical entomology center. (but at least they areyour mites.think of what you snuggle up with each time you climb into a motel bed.)3 these mites havebeen with us since time immemorial, but they weren’t discovered until 1965. if creatures as intimately associated with us as bed mites escaped our notice until the age ofcolor television, it’s hardly surprising that most of the rest of the small scale world is barelyknown to us. go out into a woods any woods at all bend down and scoop up a handful ofsoil, and you will be holding up to 10 billion bacteria, most of them unknown to science. yoursample will also contain perhaps a million plump yeasts, some 200,000 hairy little fungiknown as molds, perhaps 10,000 protozoans (of which the most familiar is the amoeba), andassorted rotifers, flatworms, roundworms, and other microscopic creatures known collectivelyas cryptozoa. a large portion of these will also be unknown. the most comprehensive handbook of microorganisms, bergey’s manual of systematicbacteriology, lists about 4,000 types of bacteria. in the 1980s, a pair of norwegian scientists,jostein goksøyr and vigdis torsvik, collected a gram of random soil from a beech forest neartheir lab in bergen and carefully analyzed its bacterial content. they found that this singlesmall sample contained between 4,000 and 5,000 separate bacterial species, more than in thewhole of bergey’s manual. they then traveled to a coastal location a few miles away,scooped up another gram of earth, and found that it contained 4,000 to 5,000 other species. asedward o. wilson observes: “if over 9,000 microbial types exist in two pinches of substratefrom two localities in norway, how many more await discovery in other, radically differenthabitats?” well, according to one estimate, it could be as high as 400 million.3 we are actually getting worse at some matters of hygiene. dr. maunder believes that the move toward low temperature washing machine detergents has encouraged bugs to proliferate. as he puts it: \"if you wash lousyclothing at low temperatures, all you get is cleaner lice.\" we don’t look in the right places. in the diversity of life, wilson describes how onebotanist spent a few days tramping around ten hectares of jungle in borneo and discovered athousand new species of flowering plant more than are found in the whole of northamerica. the plants weren’t hard to find. it’s just that no one had looked there before. koenmaes of the kenyan national museum told me that he went to one cloud forest, asmountaintop forests are known in kenya, and in a half hour “of not particularly dedicatedlooking” found four new species of millipedes, three representing new genera, and one newspecies of tree. “big tree,” he added, and shaped his arms as if about to dance with a verylarge partner. cloud forests are found on the tops of plateaus and have sometimes beenisolated for millions of years. “they provide the ideal climate for biology and they havehardly been studied,” he said. overall, tropical rain forests cover only about 6 percent of earth’s surface, but harbor morethan half of its animal life and about two thirds of its flowering plants, and most of this liferemains unknown to us because too few researchers spend time in them. not incidentally,much of this could be quite valuable. at least 99 percent of flowering plants have never beentested for their medicinal properties. because they can’t flee from predators, plants have hadto contrive chemical defenses, and so are particularly enriched in intriguing compounds. evennow nearly a quarter of all prescribed medicines are derived from just forty plants, withanother 16 percent coming from animals or microbes, so there is a serious risk with everyhectare of forest felled of losing medically vital possibilities. using a method calledcombinatorial chemistry, chemists can generate forty thousand compounds at a time in labs,but these products are random and not uncommonly useless, whereas any natural moleculewill have already passed what the economist calls “the ultimate screening programme: overthree and a half billion years of evolution.” looking for the unknown isn’t simply a matter of traveling to remote or distant places,however. in his book life: an unauthorised biography, richard fortey notes how oneancient bacterium was found on the wall of a country pub “where men had urinated forgenerations” a discovery that would seem to involve rare amounts of luckand devotion andpossibly some other quality not specified. there aren’t enough specialists.the stock of things to be found, examined, and recordedvery much outruns the supply of scientists available to do it. take the hardy and little knownorganisms known as bdelloid rotifers. these are microscopic animals that can survive almostanything. when conditions are tough, they curl up into a compact shape, switch off theirmetabolism, and wait for better times. in this state, you can drop them into boiling water orfreeze them almost to absolute zero that is the level where even atoms give up and, whenthis torment has finished and they are returned to a more pleasing environment, they willuncurl and move on as if nothing has happened. so far, about 500 species have been identified(though other sources say 360), but nobody has any idea, even remotely, how many there maybe altogether. for years almost all that was known about them was thanks to the work of adevoted amateur, a london clerical worker named david bryce who studied them in his sparetime. they can be found all over the world, but you could have all the bdelloid rotifer expertsin the world to dinner and not have to borrow plates from the neighbors. even something as important and ubiquitous as fungi and fungi are both attractscomparatively little notice. fungi are everywhere and come in many forms as mushrooms,molds, mildews, yeasts, and puffballs, to name but a sampling and they exist in volumes that most of us little suspect. gather together all the fungi found in a typical acre of meadowand you would have 2,500 pounds of the stuff. these are not marginal organisms. withoutfungi there would be no potato blights, dutch elm disease, jock itch, or athlete’s foot, but alsono yogurts or beers or cheeses. altogether about 70,000 species of fungi have been identified,but it is thought the number could be as high as 1.8 million. a lot of mycologists work inindustry, making cheeses and yogurts and the like, so it is hard to say how many are activelyinvolved in research, but we can safely take it that there are more species of fungi to be foundthan there are people to find them. the world is a really big place.we have been gulled by the ease of air travel and otherforms of communication into thinking that the world is not all that big, but at ground level,where researchers must work, it is actually enormous enormous enough to be full ofsurprises. the okapi, the nearest living relative of the giraffe, is now known to exist insubstantial numbers in the rain forests of zaire the total population is estimated at perhapsthirty thousand yet its existence wasn’t even suspected until the twentieth century. the largeflightless new zealand bird called the takahe had been presumed extinct for two hundredyears before being found living in a rugged area of the country’s south island. in 1995 a teamof french and british scientists in tibet, who were lost in a snowstorm in a remote valley,came across a breed of horse, called the riwoche, that had previously been known only fromprehistoric cave drawings. the valley’s inhabitants were astonished to learn that the horse wasconsidered a rarity in the wider world. some people think even greater surprises may await us. “a leading british ethno biologist,” wrote the economist in 1995, “thinks a megatherium, a sort of giant ground slothwhich may stand as high as a giraffe . . . may lurk in the fastnesses of the amazon basin.”perhaps significantly, the ethnobiologist wasn’t named; perhaps even more significantly,nothing more has been heard of him or his giant sloth. no one, however, can categorically saythat no such thing is there until every jungly glade has been investigated, and we are a longway from achieving that. but even if we groomed thousands of fieldworkers and dispatched them to the farthestcorners of the world, it would not be effort enough, for wherever life can be, it is. life’sextraordinary fecundity is amazing, even gratifying, but also problematic. to survey it all, youwould have to turn over every rock, sift through the litter on every forest floor, sieveunimaginable quantities of sand and dirt, climb into every forest canopy, and devise muchmore efficient ways to examine the seas. even then you would overlook whole ecosystems. inthe 1980s, spelunkers entered a deep cave in romania that had been sealed off from theoutside world for a long but unknown period and found thirty three species of insects andother small creatures spiders, centipedes, lice all blind, colorless, and new to science.they were living off the microbes in the surface scum of pools, which in turn were feeding onhydrogen sulfide from hot springs. our instinct may be to see the impossibility of tracking everything down as frustrating,dispiriting, perhaps even appalling, but it can just as well be viewed as almost unbearablyexciting. we live on a planet that has a more or less infinite capacity to surprise. whatreasoning person could possibly want it any other way? what is nearly always most arresting in any ramble through the scattered disciplines ofmodern science is realizing how many people have been willing to devote lifetimes to the most sumptuously esoteric lines of inquiry. in one of his essays, stephen jay gould notes howa hero of his named henry edward crampton spent fifty years, from 1906 to his death in1956, quietly studying a genus of land snails in polynesia called partula. over and over, yearafter year, crampton measured to the tiniest degree to eight decimal places the whorls andarcs and gentle curves of numberless partula, compiling the results into fastidiously detailedtables. a single line of text in a crampton table could represent weeks of measurement andcalculation. only slightly less devoted, and certainly more unexpected, was alfred c. kinsey, whobecame famous for his studies of human sexuality in the 1940s and 1950s. but before hismind became filled with sex, so to speak, kinsey was an entomologist, and a dogged one atthat. in one expedition lasting two years, he hiked 2,500 miles to assemble a collection of300,000 wasps. how many stings he collected along the way is not, alas, recorded. something that had been puzzling me was the question of how you assured a chain ofsuccession in these arcane fields. clearly there cannot be many institutions in the world thatrequire or are prepared to support specialists in barnacles or pacific snails. as we parted at thenatural history museum in london, i asked richard fortey how science ensures that whenone person goes there’s someone ready to take his place. he chuckled rather heartily at my naiveté. “i’m afraid it’s not as if we have substitutessitting on the bench somewhere waiting to be called in to play. when a specialist retires or,even more unfortunately, dies, that can bring a stop to things in that field, sometimes for avery long while.” “and i suppose that’s why you value someone who spends forty two years studying asingle species of plant, even if it doesn’t produce anything terribly new?” “precisely,” he said, “precisely.” and he really seemed to mean it. 24 cellsit starts with a single cell. the first cell splits to become two and the two become fourand so on. after just forty seven doublings, you have ten thousand trillion(10,000,000,000,000,000) cells in your body and are ready to spring forth as a human being.1and every one of those cells knows exactly what to do to preserve and nurture you from themoment of conception to your last breath. you have no secrets from your cells. they know far more about you than you do. each onecarries a copy of the complete genetic code the instruction manual for your body so itknows not only how to do its job but every other job in the body. never in your life will youhave to remind a cell to keep an eye on its adenosine triphosphate levels or to find a place forthe extra squirt of folic acid that’s just unexpectedly turned up. it will do that for you, andmillions more things besides. every cell in nature is a thing of wonder. even the simplest are far beyond the limits ofhuman ingenuity. to build the most basic yeast cell, for example, you would have tominiaturize about the same number of components as are found in a boeing 777 jetliner andfit them into a sphere just five microns across; then somehow you would have to persuade thatsphere to reproduce. but yeast cells are as nothing compared with human cells, which are not just more variedand complicated, but vastly more fascinating because of their complex interactions. your cells are a country of ten thousand trillion citizens, each devoted in some intensivelyspecific way to your overall well being. there isn’t a thing they don’t do for you. they letyou feel pleasure and form thoughts. they enable you to stand and stretch and caper. whenyou eat, they extract the nutrients, distribute the energy, and carry off the wastes all thosethings you learned about in junior high school biology but they also remember to make youhungry in the first place and reward you with a feeling of well being afterward so that youwon’t forget to eat again. they keep your hair growing, your ears waxed, your brain quietlypurring. they manage every corner of your being. they will jump to your defense the instantyou are threatened. they will unhesitatingly die for you billions of them do so daily. andnot once in all your years have you thanked even one of them. so let us take a moment now toregard them with the wonder and appreciation they deserve. we understand a little of how cells do the things they do how they lay down fat ormanufacture insulin or engage in many of the other acts necessary to maintain a complicatedentity like yourself but only a little. you have at least 200,000 different types of protein1 actually, quite a lot of cells are lost in the process of development, so the number you emerge with is reallyjust a guess. depending on which source you consult the number can vary by several orders of magnitude. thefigure of ten thousand trillion (or quadrillion) is from margulis and sagan, 1986. laboring away inside you, and so far we understand what no more than about 2 percent ofthem do. (others put the figure at more like 50 percent; it depends, apparently, on what youmean by “understand.”) surprises at the cellular level turn up all the time. in nature, nitric oxide is a formidabletoxin and a common component of air pollution. so scientists were naturally a little surprisedwhen, in the mid 1980s, they found it being produced in a curiously devoted manner inhuman cells. its purpose was at first a mystery, but then scientists began to find it all over theplace controlling the flow of blood and the energy levels of cells, attacking cancers andother pathogens, regulating the sense of smell, even assisting in penile erections. it alsoexplained why nitroglycerine, the well known explosive, soothes the heart pain known asangina. (it is converted into nitric oxide in the bloodstream, relaxing the muscle linings ofvessels, allowing blood to flow more freely.) in barely the space of a decade this one gassysubstance went from extraneous toxin to ubiquitous elixir. you possess “some few hundred” different types of cell, according to the belgianbiochemist christian de duve, and they vary enormously in size and shape, from nerve cellswhose filaments can stretch to several feet to tiny, disc shaped red blood cells to the rod shaped photocells that help to give us vision. they also come in a sumptuously wide range ofsizes nowhere more strikingly than at the moment of conception, when a single beatingsperm confronts an egg eighty five thousand times bigger than it (which rather puts the notionof male conquest into perspective). on average, however, a human cell is about twentymicrons wide that is about two hundredths of a millimeter which is too small to be seenbut roomy enough to hold thousands of complicated structures like mitochondria, and millionsupon millions of molecules. in the most literal way, cells also vary in liveliness. your skincells are all dead. it’s a somewhat galling notion to reflect that every inch of your surface isdeceased. if you are an average sized adult you are lugging around about five pounds of deadskin, of which several billion tiny fragments are sloughed off each day. run a finger along adusty shelf and you are drawing a pattern very largely in old skin. most living cells seldom last more than a month or so, but there are some notableexceptions. liver cells can survive for years, though the components within them may berenewed every few days. brain cells last as long as you do. you are issued a hundred billionor so at birth, and that is all you are ever going to get. it has been estimated that you lose fivehundred of them an hour, so if you have any serious thinking to do there really isn’t a momentto waste. the good news is that the individual components of your brain cells are constantlyrenewed so that, as with the liver cells, no part of them is actually likely to be more than abouta month old. indeed, it has been suggested that there isn’t a single bit of any of us not somuch as a stray molecule that was part of us nine years ago. it may not feel like it, but at thecellular level we are all youngsters. the first person to describe a cell was robert hooke, whom we last encounteredsquabbling with isaac newton over credit for the invention of the inverse square law. hookeachieved many things in his sixty eight years he was both an accomplished theoretician anda dab hand at making ingenious and useful instruments but nothing he did brought himgreater admiration than his popular book microphagia: or some physiological descriptions ofminiature bodies made by magnifying glasses, produced in 1665. it revealed to an enchantedpublic a universe of the very small that was far more diverse, crowded, and finely structuredthan anyone had ever come close to imagining. among the microscopic features first identified by hooke were little chambers in plantsthat he called “cells” because they reminded him of monks’ cells. hooke calculated that aone inch square of cork would contain 1,259,712,000 of these tiny chambers the firstappearance of such a very large number anywhere in science. microscopes by this time hadbeen around for a generation or so, but what set hooke’s apart were their technicalsupremacy. they achieved magnifications of thirty times, making them the last word inseventeenth century optical technology. so it came as something of a shock when just a decade later hooke and the other membersof london’s royal society began to receive drawings and reports from an unlettered linendraper in holland employing magnifications of up to 275 times. the draper’s name wasantoni van leeuwenhoek. though he had little formal education and no background inscience, he was a perceptive and dedicated observer and a technical genius. to this day it is not known how he got such magnificent magnifications from simplehandheld devices, which were little more than modest wooden dowels with a tiny bubble ofglass embedded in them, far more like magnifying glasses than what most of us think of asmicroscopes, but really not much like either. leeuwenhoek made a new instrument for everyexperiment he performed and was extremely secretive about his techniques, though he didsometimes offer tips to the british on how they might improve their resolutions.2 over a period of fifty years beginning, remarkably enough, when he was already pastforty he made almost two hundred reports to the royal society, all written in low dutch,the only tongue of which he was master. leeuwenhoek offered no interpretations, but simplythe facts of what he had found, accompanied by exquisite drawings. he sent reports on almosteverything that could be usefully examined bread mold, a bee’s stinger, blood cells, teeth,hair, his own saliva, excrement, and semen (these last with fretful apologies for their unsavorynature) nearly all of which had never been seen microscopically before. after he reported finding “animalcules” in a sample of pepper water in 1676, the membersof the royal society spent a year with the best devices english technology could producesearching for the “little animals” before finally getting the magnification right. whatleeuwenhoek had found were protozoa. he calculated that there were 8,280,000 of these tinybeings in a single drop of water more than the number of people in holland. the worldteemed with life in ways and numbers that no one had previously suspected. inspired by leeuwenhoek’s fantastic findings, others began to peer into microscopes withsuch keenness that they sometimes found things that weren’t in fact there. one respecteddutch observer, nicolaus hartsoecker, was convinced he saw “tiny preformed men” in spermcells. he called the little beings “homunculi” and for some time many people believed that allhumans indeed, all creatures were simply vastly inflated versions of tiny but completeprecursor beings. leeuwenhoek himself occasionally got carried away with his enthusiasms.in one of his least successful experiments he tried to study the explosive properties ofgunpowder by observing a small blast at close range; he nearly blinded himself in the process.2 leeuwenhoek was close friends with another delft notable, the artist jan vermeer. in the mid 1660s, vermeer,who previously had been a competent but not outstanding artist, suddenly developed the mastery of light andperspective for which he has been celebrated ever since. though it has never been proved, it has long beensuspected that he used a camera obscura, a device for projecting images onto a flat surface through a lens. nosuch device was listed among vermeer's personal effects after his death, but it happens that the executor ofvermeer's estate was none other than antoni van leeuwenhoek, the most secretive lens maker of his day. in 1683 leeuwenhoek discovered bacteria, but that was about as far as progress could getfor the next century and a half because of the limitations of microscope technology. not until1831 would anyone first see the nucleus of a cell it was found by the scottish botanistrobert brown, that frequent but always shadowy visitor to the history of science. brown, wholived from 1773 to 1858, called it nucleus from the latin nucula, meaning little nut or kernel.not until 1839, however, did anyone realize that all living matter is cellular. it was theodorschwann, a german, who had this insight, and it was not only comparatively late, as scientificinsights go, but not widely embraced at first. it wasn’t until the 1860s, and some landmarkwork by louis pasteur in france, that it was shown conclusively that life cannot arisespontaneously but must come from preexisting cells. the belief became known as the “celltheory,” and it is the basis of all modern biology. the cell has been compared to many things, from “a complex chemical refinery” (by thephysicist james trefil) to “a vast, teeming metropolis” (the biochemist guy brown). a cell isboth of those things and neither. it is like a refinery in that it is devoted to chemical activityon a grand scale, and like a metropolis in that it is crowded and busy and filled withinteractions that seem confused and random but clearly have some system to them. but it is amuch more nightmarish place than any city or factory that you have ever seen. to begin withthere is no up or down inside the cell (gravity doesn’t meaningfully apply at the cellularscale), and not an atom’s width of space is unused. there is activity every where and aceaseless thrum of electrical energy. you may not feel terribly electrical, but you are. thefood we eat and the oxygen we breathe are combined in the cells into electricity. the reasonwe don’t give each other massive shocks or scorch the sofa when we sit is that it is allhappening on a tiny scale: a mere 0.1 volts traveling distances measured in nanometers.however, scale that up and it would translate as a jolt of twenty million volts per meter, aboutthe same as the charge carried by the main body of a thunderstorm. whatever their size or shape, nearly all your cells are built to fundamentally the same plan:they have an outer casing or membrane, a nucleus wherein resides the necessary geneticinformation to keep you going, and a busy space between the two called the cytoplasm. themembrane is not, as most of us imagine it, a durable, rubbery casing, something that youwould need a sharp pin to prick. rather, it is made up of a type of fatty material known as alipid, which has the approximate consistency “of a light grade of machine oil,” to quotesherwin b. nuland. if that seems surprisingly insubstantial, bear in mind that at themicroscopic level things behave differently. to anything on a molecular scale water becomesa kind of heavy duty gel, and a lipid is like iron. if you could visit a cell, you wouldn’t like it. blown up to a scale at which atoms wereabout the size of peas, a cell itself would be a sphere roughly half a mile across, and supportedby a complex framework of girders called the cytoskeleton. within it, millions upon millionsof objects some the size of basketballs, others the size of cars would whiz about likebullets. there wouldn’t be a place you could stand without being pummeled and rippedthousands of times every second from every direction. even for its full time occupants theinside of a cell is a hazardous place. each strand of dna is on average attacked or damagedonce every 8.4 seconds ten thousand times in a day by chemicals and other agents thatwhack into or carelessly slice through it, and each of these wounds must be swiftly stitched upif the cell is not to perish. the proteins are especially lively, spinning, pulsating, and flying into each other up to abillion times a second. enzymes, themselves a type of protein, dash everywhere, performingup to a thousand tasks a second. like greatly speeded up worker ants, they busily build and rebuild molecules, hauling a piece off this one, adding a piece to that one. some monitorpassing proteins and mark with a chemical those that are irreparably damaged or flawed. onceso selected, the doomed proteins proceed to a structure called a proteasome, where they arestripped down and their components used to build new proteins. some types of protein existfor less than half an hour; others survive for weeks. but all lead existences that areinconceivably frenzied. as de duve notes, “the molecular world must necessarily remainentirely beyond the powers of our imagination owing to the incredible speed with whichthings happen in it.” but slow things down, to a speed at which the interactions can be observed, and thingsdon’t seem quite so unnerving. you can see that a cell is just millions of objects lysosomes,endosomes, ribosomes, ligands, peroxisomes, proteins of every size and shape bumping intomillions of other objects and performing mundane tasks: extracting energy from nutrients,assembling structures, getting rid of waste, warding off intruders, sending and receivingmessages, making repairs. typically a cell will contain some 20,000 different types of protein,and of these about 2,000 types will each be represented by at least 50,000 molecules. “thismeans,” says nuland, “that even if we count only those molecules present in amounts of morethan 50,000 each, the total is still a very minimum of 100 million protein molecules in eachcell. such a staggering figure gives some idea of the swarming immensity of biochemicalactivity within us.” it is all an immensely demanding process. your heart must pump 75 gallons of blood anhour, 1,800 gallons every day, 657,000 gallons in a year that’s enough to fill four olympic sized swimming pools to keep all those cells freshly oxygenated. (and that’s at rest. duringexercise the rate can increase as much as sixfold.) the oxygen is taken up by themitochondria. these are the cells’ power stations, and there are about a thousand of them in atypical cell, though the number varies considerably depending on what a cell does and howmuch energy it requires. you may recall from an earlier chapter that the mitochondria are thought to have originatedas captive bacteria and that they now live essentially as lodgers in our cells, preserving theirown genetic instructions, dividing to their own timetable, speaking their own language. youmay also recall that we are at the mercy of their goodwill. here’s why. virtually all the foodand oxygen you take into your body are delivered, after processing, to the mitochondria,where they are converted into a molecule called adenosine triphosphate, or atp. you may not have heard of atp, but it is what keeps you going. atp molecules areessentially little battery packs that move through the cell providing energy for all the cell’sprocesses, and you get through a lot of it. at any given moment, a typical cell in your bodywill have about one billion atp molecules in it, and in two minutes every one of them willhave been drained dry and another billion will have taken their place. every day you produceand use up a volume of atp equivalent to about half your body weight. feel the warmth ofyour skin. that’s your atp at work. when cells are no longer needed, they die with what can only be called great dignity. theytake down all the struts and buttresses that hold them together and quietly devour theircomponent parts. the process is known as apoptosis or programmed cell death. every daybillions of your cells die for your benefit and billions of others clean up the mess. cells canalso die violently for instance, when infected but mostly they die because they are told to.indeed, if not told to live if not given some kind of active instruction from another cell cells automatically kill themselves. cells need a lot of reassurance. when, as occasionally happens, a cell fails to expire in the prescribed manner, but ratherbegins to divide and proliferate wildly, we call the result cancer. cancer cells are really justconfused cells. cells make this mistake fairly regularly, but the body has elaboratemechanisms for dealing with it. it is only very rarely that the process spirals out of control. onaverage, humans suffer one fatal malignancy for each 100 million billion cell divisions.cancer is bad luck in every possible sense of the term. the wonder of cells is not that things occasionally go wrong, but that they manageeverything so smoothly for decades at a stretch. they do so by constantly sending andmonitoring streams of messages a cacophony of messages from all around the body:instructions, queries, corrections, requests for assistance, updates, notices to divide or expire.most of these signals arrive by means of couriers called hormones, chemical entities such asinsulin, adrenaline, estrogen, and testosterone that convey information from remote outpostslike the thyroid and endocrine glands. still other messages arrive by telegraph from the brainor from regional centers in a process called paracrine signaling. finally, cells communicatedirectly with their neighbors to make sure their actions are coordinated. what is perhaps most remarkable is that it is all just random frantic action, a sequence ofendless encounters directed by nothing more than elemental rules of attraction and repulsion.there is clearly no thinking presence behind any of the actions of the cells. it all just happens,smoothly and repeatedly and so reliably that seldom are we even conscious of it, yet somehowall this produces not just order within the cell but a perfect harmony right across the organism.in ways that we have barely begun to understand, trillions upon trillions of reflexive chemicalreactions add up to a mobile, thinking, decision making you or, come to that, a rather lessreflective but still incredibly organized dung beetle. every living thing, never forget, is awonder of atomic engineering. indeed, some organisms that we think of as primitive enjoy a level of cellular organizationthat makes our own look carelessly pedestrian. disassemble the cells of a sponge (by passingthem through a sieve, for instance), then dump them into a solution, and they will find theirway back together and build themselves into a sponge again. you can do this to them overand over, and they will doggedly reassemble because, like you and me and every other livingthing, they have one overwhelming impulse: to continue to be. and that’s because of a curious, determined, barely understood molecule that is itself notalive and for the most part doesn’t do anything at all. we call it dna, and to begin tounderstand its supreme importance to science and to us we need to go back 160 years or so tovictorian england and to the moment when the naturalist charles darwin had what has beencalled “the single best idea that anyone has ever had” and then, for reasons that take a littleexplaining, locked it away in a drawer for the next fifteen years. 25 darwin’s singular notionin the late summer or early autumn of 1859, whitwell elwin, editor of the respectedbritish journal the quarterly review, was sent an advance copy of a new book by thenaturalist charles darwin. elwin read the book with interest and agreed that it had merit, butfeared that the subject matter was too narrow to attract a wide audience. he urged darwin towrite a book about pigeons instead. “everyone is interested in pigeons,” he observedhelpfully. elwin’s sage advice was ignored, and on the origin of species by means of naturalselection, or the preservation of favoured races in the struggle for life was published in latenovember 1859, priced at fifteen shillings. the first edition of 1,250 copies sold out on thefirst day. it has never been out of print, and scarcely out of controversy, in all the time since not bad going for a man whose principal other interest was earthworms and who, but for asingle impetuous decision to sail around the world, would very probably have passed his lifeas an anonymous country parson known for, well, for an interest in earthworms. charles robert darwin was born on february 12, 1809,1 in shrewsbury, a sedate markettown in the west midlands of england. his father was a prosperous and well regardedphysician. his mother, who died when charles was only eight, was the daughter of josiahwedgwood, of pottery fame. darwin enjoyed every advantage of upbringing, but continually pained his widowed fatherwith his lackluster academic performance. “you care for nothing but shooting, dogs, and rat catching, and you will be a disgrace to yourself and all your family,” his father wrote in a linethat nearly always appears just about here in any review of darwin’s early life. although hisinclination was to natural history, for his father’s sake he tried to study medicine at edinburghuniversity but couldn’t bear the blood and suffering. the experience of witnessing anoperation on an understandably distressed child this was in the days before anesthetics, ofcourse left him permanently traumatized. he tried law instead, but found that insupportablydull and finally managed, more or less by default, to acquire a degree in divinity fromcambridge. a life in a rural vicarage seemed to await him when from out of the blue there came a moretempting offer. darwin was invited to sail on the naval survey ship hms beagle, essentiallyas dinner company for the captain, robert fitzroy, whose rank precluded his socializing withanyone other than a gentleman. fitzroy, who was very odd, chose darwin in part because heliked the shape of darwin’s nose. (it betokened depth of character, he believed.) darwin wasnot fitzroy’s first choice, but got the nod when fitzroy’s preferred companion dropped out.from a twenty first century perspective the two men’s most striking joint feature was their1 an auspicious date in history: on the same day in kentucky, abraham lincoln was born. extreme youthfulness. at the time of sailing, fitzroy was only twenty three, darwin justtwenty two. fitzroy’s formal assignment was to chart coastal waters, but his hobby passion really was to seek out evidence for a literal, biblical interpretation of creation. that darwin wastrained for the ministry was central to fitzroy’s decision to have him aboard. that darwinsubsequently proved to be not only liberal of view but less than wholeheartedly devoted tochristian fundamentals became a source of lasting friction between them. darwin’s time aboard hms beagle, from 1831 to 1836, was obviously the formativeexperience of his life, but also one of the most trying. he and his captain shared a small cabin,which can’t have been easy as fitzroy was subject to fits of fury followed by spells ofsimmering resentment. he and darwin constantly engaged in quarrels, some “bordering oninsanity,” as darwin later recalled. ocean voyages tended to become melancholyundertakings at the best of times the previous captain of the beagle had put a bullet throughhis brain during a moment of lonely gloom and fitzroy came from a family well known fora depressive instinct. his uncle, viscount castlereagh, had slit his throat the previous decadewhile serving as chancellor of the exchequer. (fitzroy would himself commit suicide by thesame method in 1865.) even in his calmer moods, fitzroy proved strangely unknowable.darwin was astounded to learn upon the conclusion of their voyage that almost at oncefitzroy married a young woman to whom he had long been betrothed. in five years indarwin’s company, he had not once hinted at an attachment or even mentioned her name. in every other respect, however, the beagle voyage was a triumph. darwin experiencedadventure enough to last a lifetime and accumulated a hoard of specimens sufficient to makehis reputation and keep him occupied for years. he found a magnificent trove of giant ancientfossils, including the finest megatherium known to date; survived a lethal earthquake inchile; discovered a new species of dolphin (which he dutifully named delphinus fitzroyi);conducted diligent and useful geological investigations throughout the andes; and developeda new and much admired theory for the formation of coral atolls, which suggested, notcoincidentally, that atolls could not form in less than a million years the first hint of hislong standing attachment to the extreme antiquity of earthly processes. in 1836, aged twenty seven, he returned home after being away for five years and two days. he never left englandagain. one thing darwin didn’t do on the voyage was propound the theory (or even a theory) ofevolution. for a start, evolution as a concept was already decades old by the 1830s. darwin’sown grandfather, erasmus, had paid tribute to evolutionary principles in a poem of inspiredmediocrity called “the temple of nature” years before charles was even born. it wasn’t untilthe younger darwin was back in england and read thomas malthus’s essay on the principleof population (which proposed that increases in food supply could never keep up withpopulation growth for mathematical reasons) that the idea began to percolate through his mindthat life is a perpetual struggle and that natural selection was the means by which somespecies prospered while others failed. specifically what darwin saw was that all organismscompeted for resources, and those that had some innate advantage would prosper and pass onthat advantage to their offspring. by such means would species continuously improve. it seems an awfully simple idea it is an awfully simple idea but it explained a great deal,and darwin was prepared to devote his life to it. “how stupid of me not to have thought ofit!” t. h. huxley cried upon reading on the origin of species. it is a view that has beenechoed ever since. interestingly, darwin didn’t use the phrase “survival of the fittest” in any of his work(though he did express his admiration for it). the expression was coined five years after thepublication of on the origin of species by herbert spencer in principles of biology in 1864.nor did he employ the word evolution in print until the sixth edition of origin (by which timeits use had become too widespread to resist), preferring instead “descent with modification.”nor, above all, were his conclusions in any way inspired by his noticing, during his time inthe galápagos islands, an interesting diversity in the beaks of finches. the story asconventionally told (or at least as frequently remembered by many of us) is that darwin,while traveling from island to island, noticed that the finches’ beaks on each island weremarvelously adapted for exploiting local resources that on one island beaks were sturdy andshort and good for cracking nuts, while on the next island beaks were perhaps long and thinand well suited for winkling food out of crevices and it was this that set him to thinking thatperhaps the birds had not been created this way, but had in a sense created themselves. in fact, the birds had created themselves, but it wasn’t darwin who noticed it. at the timeof the beagle voyage, darwin was fresh out of college and not yet an accomplished naturalistand so failed to see that the galápagos birds were all of a type. it was his friend theornithologist john gould who realized that what darwin had found was lots of finches withdifferent talents. unfortunately, in his inexperience darwin had not noted which birds camefrom which islands. (he had made a similar error with tortoises.) it took years to sort themuddles out. because of these oversights, and the need to sort through crates and crates of other beaglespecimens, it wasn’t until 1842, six years after his return to england, that darwin finallybegan to sketch out the rudiments of his new theory. these he expanded into a 230 page“sketch” two years later. and then he did an extraordinary thing: he put his notes away andfor the next decade and a half busied himself with other matters. he fathered ten children,devoted nearly eight years to writing an exhaustive opus on barnacles (“i hate a barnacle as noman ever did before,” he sighed, understandably, upon the work’s conclusion), and fell preyto strange disorders that left him chronically listless, faint, and “flurried,” as he put it. thesymptoms nearly always included a terrible nausea and generally also incorporatedpalpitations, migraines, exhaustion, trembling, spots before the eyes, shortness of breath,“swimming of the head,” and, not surprisingly, depression. the cause of the illness has never been established, but the most romantic and perhapslikely of the many suggested possibilities is that he suffered from chagas’s disease, alingering tropical malady that he could have acquired from the bite of a benchuga bug insouth america. a more prosaic explanation is that his condition was psychosomatic. in eithercase, the misery was not. often he could work for no more than twenty minutes at a stretch,sometimes not that. much of the rest of his time was devoted to a series of increasingly desperate treatments icy plunge baths, dousings in vinegar, draping himself with “electric chains” that subjectedhim to small jolts of current. he became something of a hermit, seldom leaving his home inkent, down house. one of his first acts upon moving to the house was to erect a mirroroutside his study window so that he could identify, and if necessary avoid, callers. darwin kept his theory to himself because he well knew the storm it would cause. in 1844,the year he locked his notes away, a book called vestiges of the natural history of creationroused much of the thinking world to fury by suggesting that humans might have evolvedfrom lesser primates without the assistance of a divine creator. anticipating the outcry, the author had taken careful steps to conceal his identity, which he kept a secret from even hisclosest friends for the next forty years. some wondered if darwin himself might be the author.others suspected prince albert. in fact, the author was a successful and generally unassumingscottish publisher named robert chambers whose reluctance to reveal himself had a practicaldimension as well as a personal one: his firm was a leading publisher of bibles. vestiges waswarmly blasted from pulpits throughout britain and far beyond, but also attracted a good dealof more scholarly ire. the edinburgh review devoted nearly an entire issue eighty fivepages to pulling it to pieces. even t. h. huxley, a believer in evolution, attacked the bookwith some venom, unaware that the author was a friend.2 darwin’s manuscript might have remained locked away till his death but for an alarmingblow that arrived from the far east in the early summer of 1858 in the form of a packetcontaining a friendly letter from a young naturalist named alfred russel wallace and the draftof a paper, on the tendency of varieties to depart indefinitely from the original type,outlining a theory of natural selection that was uncannily similar to darwin’s secret jottings.even some of the phrasing echoed darwin’s own. “i never saw a more striking coincidence,”darwin reflected in dismay. “if wallace had my manuscript sketch written out in 1842, hecould not have made a better short abstract.” wallace didn’t drop into darwin’s life quite as unexpectedly as is sometimes suggested.the two were already corresponding, and wallace had more than once generously sentdarwin specimens that he thought might be of interest. in the process of these exchangesdarwin had discreetly warned wallace that he regarded the subject of species creation as hisown territory. “this summer will make the 20th year (!) since i opened my first note book, onthe question of how & in what way do species & varieties differ from each other,” he hadwritten to wallace some time earlier. “i am now preparing my work for publication,” headded, even though he wasn’t really.in any case, wallace failed to grasp what darwin was trying to tell him, and of course hecould have no idea that his own theory was so nearly identical to one that darwin had beenevolving, as it were, for two decades.darwin was placed in an agonizing quandary. if he rushed into print to preserve his priority,he would be taking advantage of an innocent tip off from a distant admirer. but if he steppedaside, as gentlemanly conduct arguably required, he would lose credit for a theory that he hadindependently propounded. wallace’s theory was, by wallace’s own admission, the result of aflash of insight; darwin’s was the product of years of careful, plodding, methodical thought. itwas all crushingly unfair.to compound his misery, darwin’s youngest son, also named charles, had contracted scarletfever and was critically ill. at the height of the crisis, on june 28, the child died. despite thedistraction of his son’s illness, darwin found time to dash off letters to his friends charleslyell and joseph hooker, offering to step aside but noting that to do so would mean that allhis work, “whatever it may amount to, will be smashed.” lyell and hooker came up with thecompromise solution of presenting a summary of darwin’s and wallace’s ideas together. thevenue they settled on was a meeting of the linnaean society, which at the time was strugglingto find its way back into fashion as a seat of scientific eminence. on july 1, 1858, darwin’s2 darwin was one of the few to guess correctly. he happened to be visiting chambers one day when an advancecopy of the sixth edition of vestiges was delivered. the keenness with which chambers checked the revisionswas something of a giveaway, though it appears the two men did not discuss it. and wallace’s theory was unveiled to the world. darwin himself was not present. on the dayof the meeting, he and his wife were burying their son. the darwin wallace presentation was one of seven that evening one of the others was onthe flora of angola and if the thirty or so people in the audience had any idea that they werewitnessing the scientific highlight of the century, they showed no sign of it. no discussionfollowed. nor did the event attract much notice elsewhere. darwin cheerfully later noted thatonly one person, a professor haughton of dublin, mentioned the two papers in print and hisconclusion was “that all that was new in them was false, and what was true was old.” wallace, still in the distant east, learned of these maneuverings long after the event, butwas remarkably equable and seemed pleased to have been included at all. he even referred tothe theory forever after as “darwinism.” much less amenable to darwin’s claim of prioritywas a scottish gardener named patrick matthew who had, rather remarkably, also come upwith the principles of natural selection in fact, in the very year that darwin had set sail inthebeagle. unfortunately, matthew had published these views in a book called naval timberand arboriculture, which had been missed not just by darwin, but by the entire world.matthew kicked up in a lively manner, with a letter to gardener’s chronicle, when he sawdarwin gaining credit everywhere for an idea that really was his. darwin apologized withouthesitation, though he did note for the record: “i think that no one will feel surprised thatneither i, nor apparently any other naturalist, has heard of mr. matthew’s views, consideringhow briefly they are given, and they appeared in the appendix to a work on naval timberand arboriculture.” wallace continued for another fifty years as a naturalist and thinker, occasionally a verygood one, but increasingly fell from scientific favor by taking up dubious interests such asspiritualism and the possibility of life existing elsewhere in the universe. so the theorybecame, essentially by default, darwin’s alone. darwin never ceased being tormented by his ideas. he referred to himself as “the devil’schaplain” and said that revealing the theory felt “like confessing a murder.” apart from allelse, he knew it deeply pained his beloved and pious wife. even so, he set to work at onceexpanding his manuscript into a book length work. provisionally he called it an abstract ofan essay on the origin of species and varieties through natural selection  a title so tepidand tentative that his publisher, john murray, decided to issue just five hundred copies. butonce presented with the manuscript, and a slightly more arresting title, murray reconsideredand increased the initial print run to 1,250. on the origin of species was an immediate commercial success, but rather less of a criticalone. darwin’s theory presented two intractable difficulties. it needed far more time than lordkelvin was willing to concede, and it was scarcely supported by fossil evidence. where,asked darwin’s more thoughtful critics, were the transitional forms that his theory so clearlycalled for? if new species were continuously evolving, then there ought to be lots ofintermediate forms scattered across the fossil record, but there were not.3 in fact, the record asit existed then (and for a long time afterward) showed no life at all right up to the moment ofthe famous cambrian explosion.3 by coincidence, in 1861, at the height of the controversy, just such evidence turned up when workers inbavaria found the bones of an ancient archaeopteryx, a creature halfway between a bird and a dinosaur. (it hadfeathers, but it also had teeth.) it was an impressive and helpful find, and its significance much debated, but asingle discovery could hardly be considered conclusive. but now here was darwin, without any evidence, insisting that the earlier seas must havehad abundant life and that we just hadn’t found it yet because, for whatever reason, it hadn’tbeen preserved. it simply could not be otherwise, darwin maintained. “the case at presentmust remain inexplicable; and may be truly urged as a valid argument against the views hereentertained,” he allowed most candidly, but he refused to entertain an alternative possibility.by way of explanation he speculated inventively but incorrectly that perhaps theprecambrian seas had been too clear to lay down sediments and thus had preserved no fossils. even darwin’s closest friends were troubled by the blitheness of some of his assertions.adam sedgwick, who had taught darwin at cambridge and taken him on a geological tour ofwales in 1831, said the book gave him “more pain than pleasure.” louis agassiz dismissed itas poor conjecture. even lyell concluded gloomily: “darwin goes too far.” t. h. huxley disliked darwin’s insistence on huge amounts of geological time because hewas a saltationist, which is to say a believer in the idea that evolutionary changes happen notgradually but suddenly. saltationists (the word comes from the latin for “leap”) couldn’taccept that complicated organs could ever emerge in slow stages. what good, after all, is one tenth of a wing or half an eye? such organs, they thought, only made sense if they appeared ina finished state. the belief was surprising in as radical a spirit as huxley because it closely recalled a veryconservative religious notion first put forward by the english theologian william paley in1802 and known as argument from design. paley contended that if you found a pocket watchon the ground, even if you had never seen such a thing before, you would instantly perceivethat it had been made by an intelligent entity. so it was, he believed, with nature: itscomplexity was proof of its design. the notion was a powerful one in the nineteenth century,and it gave darwin trouble too. “the eye to this day gives me a cold shudder,” heacknowledged in a letter to a friend. in the origin he conceded that it “seems, i freely confess,absurd in the highest possible degree” that natural selection could produce such an instrumentin gradual steps. even so, and to the unending exasperation of his supporters, darwin not only insisted thatall change was gradual, but in nearly every edition of origin he stepped up the amount of timehe supposed necessary to allow evolution to progress, which pushed his ideas increasingly outof favor. “eventually,” according to the scientist and historian jeffrey schwartz, “darwin lostvirtually all the support that still remained among the ranks of fellow natural historians andgeologists.” ironically, considering that darwin called his book on the origin of species, the one thinghe couldn’t explain was how species originated. darwin’s theory suggested a mechanism forhow a species might become stronger or better or faster in a word, fitter but gave noindication of how it might throw up a new species. a scottish engineer, fleeming jenkin,considered the problem and noted an important flaw in darwin’s argument. darwin believedthat any beneficial trait that arose in one generation would be passed on to subsequentgenerations, thus strengthening the species. jenkin pointed out that a favorable trait in one parent wouldn’t become dominant insucceeding generations, but in fact would be diluted through blending. if you pour whiskeyinto a tumbler of water, you don’t make the whiskey stronger, you make it weaker. and if youpour that dilute solution into another glass of water, it becomes weaker still. in the same way,any favorable trait introduced by one parent would be successively watered down by subsequent matings until it ceased to be apparent at all. thus darwin’s theory was not a recipefor change, but for constancy. lucky flukes might arise from time to time, but they wouldsoon vanish under the general impulse to bring everything back to a stable mediocrity. ifnatural selection were to work, some alternative, unconsidered mechanism was required. unknown to darwin and everyone else, eight hundred miles away in a tranquil corner ofmiddle europe a retiring monk named gregor mendel was coming up with the solution. mendel was born in 1822 to a humble farming family in a backwater of the austrianempire in what is now the czech republic. schoolbooks once portrayed him as a simple butobservant provincial monk whose discoveries were largely serendipitous the result ofnoticing some interesting traits of inheritance while pottering about with pea plants in themonastery’s kitchen garden. in fact, mendel was a trained scientist he had studied physicsand mathematics at the olmütz philosophical institute and the university of vienna and hebrought scientific discipline to all he did. moreover, the monastery at brno where he livedfrom 1843 was known as a learned institution. it had a library of twenty thousand books and atradition of careful scientific investigation. before embarking on his experiments, mendel spent two years preparing his controlspecimens, seven varieties of pea, to make sure they bred true. then, helped by two full timeassistants, he repeatedly bred and crossbred hybrids from thirty thousand pea plants. it wasdelicate work, requiring them to take the most exacting pains to avoid accidental cross fertilization and to note every slight variation in the growth and appearance of seeds, pods,leaves, stems, and flowers. mendel knew what he was doing. he never used the word gene  it wasn’t coined until 1913, in an english medicaldictionary though he did invent the terms dominant and recessive. what he established wasthat every seed contained two “factors” or “elemente,” as he called them a dominant oneand a recessive one and these factors, when combined, produced predictable patterns ofinheritance. the results he converted into precise mathematical formulae. altogether mendel spenteight years on the experiments, then confirmed his results with similar experiments onflowers, corn, and other plants. if anything, mendel was too scientific in his approach, forwhen he presented his findings at the february and march meetings of the natural historysociety of brno in 1865, the audience of about forty listened politely but was conspicuouslyunmoved, even though the breeding of plants was a matter of great practical interest to manyof the members. when mendel’s report was published, he eagerly sent a copy to the great swiss botanistkarl wilhelm von nägeli, whose support was more or less vital for the theory’s prospects.unfortunately, nägeli failed to perceive the importance of what mendel had found. hesuggested that mendel try breeding hawkweed. mendel obediently did as nägeli suggested,but quickly realized that hawkweed had none of the requisite features for studying heritability.it was evident to him that nägeli had not read the paper closely, or possibly at all. frustrated,mendel retired from investigating heritability and spent the rest of his life growingoutstanding vegetables and studying bees, mice, and sunspots, among much else. eventuallyhe was made abbot. mendel’s findings weren’t quite as widely ignored as is sometimes suggested. his studyreceived a glowing entry in the encyclopaedia britannica  then a more leading record of scientific thought than now and was cited repeatedly in an important paper by the germanwilhelm olbers focke. indeed, it was because mendel’s ideas never entirely sank below thewaterline of scientific thought that they were so easily recovered when the world was readyfor them. together, without realizing it, darwin and mendel laid the groundwork for all of lifesciences in the twentieth century. darwin saw that all living things are connected, thatultimately they “trace their ancestry to a single, common source,” while mendel’s workprovided the mechanism to explain how that could happen. the two men could easily havehelped each other. mendel owned a german edition of the origin of species, which he isknown to have read, so he must have realized the applicability of his work to darwin’s, yet heappears to have made no effort to get in touch. and darwin for his part is known to havestudied focke’s influential paper with its repeated references to mendel’s work, but didn’tconnect them to his own studies. the one thing everyone thinks featured in darwin’s argument, that humans are descendedfrom apes, didn’t feature at all except as one passing allusion. even so, it took no great leap ofimagination to see the implications for human development in darwin’s theories, and itbecame an immediate talking point. the showdown came on saturday, june 30, 1860, at a meeting of the british associationfor the advancement of science in oxford. huxley had been urged to attend by robertchambers, author of vestiges of the natural history of creation, though he was still unawareof chambers’s connection to that contentious tome. darwin, as ever, was absent. the meetingwas held at the oxford zoological museum. more than a thousand people crowded into thechamber; hundreds more were turned away. people knew that something big was going tohappen, though they had first to wait while a slumber inducing speaker named john williamdraper of new york university bravely slogged his way through two hours of introductoryremarks on “the intellectual development of europe considered with reference to the viewsof mr. darwin.” finally, the bishop of oxford, samuel wilberforce, rose to speak. wilberforce had beenbriefed (or so it is generally assumed) by the ardent anti darwinian richard owen, who hadbeen a guest in his home the night before. as nearly always with events that end in uproar,accounts vary widely on what exactly transpired. in the most popular version, wilberforce,when properly in flow, turned to huxley with a dry smile and demanded of him whether heclaimed attachment to the apes by way of his grandmother or grandfather. the remark wasdoubtless intended as a quip, but it came across as an icy challenge. according to his ownaccount, huxley turned to his neighbor and whispered, “the lord hath delivered him into myhands,” then rose with a certain relish. others, however, recalled a huxley trembling with fury and indignation. at all events,huxley declared that he would rather claim kinship to an ape than to someone who used hiseminence to propound uninformed twaddle in what was supposed to be a serious scientificforum. such a riposte was a scandalous impertinence, as well as an insult to wilberforce’soffice, and the proceedings instantly collapsed in tumult. a lady brewster fainted. robertfitzroy, darwin’s companion on the beagle twenty five years before, wandered through thehall with a bible held aloft, shouting, “the book, the book.” (he was at the conference topresent a paper on storms in his capacity as head of the newly created meteorologicaldepartment.) interestingly, each side afterward claimed to have routed the other. darwin did eventually make his belief in our kinship with the apes explicit in the descentof man in 1871. the conclusion was a bold one since nothing in the fossil record supportedsuch a notion. the only known early human remains of that time were the famous neandertalbones from germany and a few uncertain fragments of jawbones, and many respectedauthorities refused to believe even in their antiquity. the descent of man was altogether amore controversial book, but by the time of its appearance the world had grown less excitableand its arguments caused much less of a stir. for the most part, however, darwin passed his twilight years with other projects, most ofwhich touched only tangentially on questions of natural selection. he spent amazingly longperiods picking through bird droppings, scrutinizing the contents in an attempt to understandhow seeds spread between continents, and spent years more studying the behavior of worms.one of his experiments was to play the piano to them, not to amuse them but to study theeffects on them of sound and vibration. he was the first to realize how vitally importantworms are to soil fertility. “it may be doubted whether there are many other animals whichhave played so important a part in the history of the world,” he wrote in his masterwork on thesubject, the formation of vegetable mould through the action of worms (1881), which wasactually more popular thanon the origin of species had ever been. among his other bookswere on the various contrivances by which british and foreign orchids are fertilised byinsects (1862), expressions of the emotions in man and animals (1872), which sold almost5,300 copies on its first day, the effects of cross and self fertilization in the vegetablekingdom (1876) a subject that came improbably close to mendel’s own work, withoutattaining anything like the same insights and his last book, the power of movement inplants. finally, but not least, he devoted much effort to studying the consequences ofinbreeding a matter of private interest to him. having married his own cousin, darwinglumly suspected that certain physical and mental frailties among his children arose from alack of diversity in his family tree. darwin was often honored in his lifetime, but never for on the origin of species ordescentof man. when the royal society bestowed on him the prestigious copley medal it was for hisgeology, zoology, and botany, not evolutionary theories, and the linnaean society wassimilarly pleased to honor darwin without embracing his radical notions. he was neverknighted, though he was buried in westminster abbey next to newton. he died at down inapril 1882. mendel died two years later. darwin’s theory didn’t really gain widespread acceptance until the 1930s and 1940s, withthe advance of a refined theory called, with a certain hauteur, the modern synthesis,combining darwin’s ideas with those of mendel and others. for mendel, appreciation wasalso posthumous, though it came somewhat sooner. in 1900, three scientists workingseparately in europe rediscovered mendel’s work more or less simultaneously. it was onlybecause one of them, a dutchman named hugo de vries, seemed set to claim mendel’sinsights as his own that a rival made it noisily clear that the credit really lay with the forgottenmonk. the world was almost ready, but not quite, to begin to understand how we got here howwe made each other. it is fairly amazing to reflect that at the beginning of the twentiethcentury, and for some years beyond, the best scientific minds in the world couldn’t actuallytell you where babies came from. and these, you may recall, were men who thought science was nearly at an end. 26 the stuff of lifeif your two parents hadn’t bonded just when they did possibly to the second, possiblyto the nanosecond you wouldn’t be here. and if their parents hadn’t bonded in a preciselytimely manner, you wouldn’t be here either. and if their parents hadn’t done likewise, andtheir parents before them, and so on, obviously and indefinitely, you wouldn’t be here. push backwards through time and these ancestral debts begin to add up. go back just eightgenerations to about the time that charles darwin and abraham lincoln were born, andalready there are over 250 people on whose timely couplings your existence depends.continue further, to the time of shakespeare and the mayflower pilgrims, and you have nofewer than 16,384 ancestors earnestly exchanging genetic material in a way that would,eventually and miraculously, result in you. at twenty generations ago, the number of people procreating on your behalf has risen to1,048,576. five generations before that, and there are no fewer than 33,554,432 men andwomen on whose devoted couplings your existence depends. by thirty generations ago, yourtotal number of forebears remember, these aren’t cousins and aunts and other incidentalrelatives, but only parents and parents of parents in a line leading ineluctably to you is overone billion (1,073,741,824, to be precise). if you go back sixty four generations, to the time ofthe romans, the number of people on whose cooperative efforts your eventual existencedepends has risen to approximately 1,000,000,000,000,000,000, which is several thousandtimes the total number of people who have ever lived. clearly something has gone wrong with our math here. the answer, it may interest you tolearn, is that your line is not pure. you couldn’t be here without a little incest actually quitea lot of incest albeit at a genetically discreet remove. with so many millions of ancestors inyour background, there will have been many occasions when a relative from your mother’sside of the family procreated with some distant cousin from your father’s side of the ledger. infact, if you are in a partnership now with someone from your own race and country, thechances are excellent that you are at some level related. indeed, if you look around you on abus or in a park or café or any crowded place, most of the people you see are very probablyrelatives. when someone boasts to you that he is descended from william the conqueror orthe mayflower pilgrims, you should answer at once: “me, too!” in the most literal andfundamental sense we are all family. we are also uncannily alike. compare your genes with any other human being’s and onaverage they will be about 99.9 percent the same. that is what makes us a species. the tinydifferences in that remaining 0.1 percent “roughly one nucleotide base in every thousand,”to quote the british geneticist and recent nobel laureate john sulston are what endow uswith our individuality. much has been made in recent years of the unraveling of the human genome. in fact, there is no such thing as “the” human genome. every human genome isdifferent. otherwise we would all be identical. it is the endless recombinations of ourgenomes each nearly identical, but not quite that make us what we are, both as individualsand as a species. but what exactly is this thing we call the genome? and what, come to that, are genes?well, start with a cell again. inside the cell is a nucleus, and inside each nucleus are thechromosomes forty six little bundles of complexity, of which twenty three come from yourmother and twenty three from your father. with a very few exceptions, every cell in yourbody 99.999 percent of them, say carries the same complement of chromosomes. (theexceptions are red blood cells, some immune system cells, and egg and sperm cells, which forvarious organizational reasons don’t carry the full genetic package.) chromosomes constitutethe complete set of instructions necessary to make and maintain you and are made of longstrands of the little wonder chemical called deoxyribonucleic acid or dna “the mostextraordinary molecule on earth,” as it has been called. dna exists for just one reason to create more dna and you have a lot of it inside you:about six feet of it squeezed into almost every cell. each length of dna comprises some 3.2billion letters of coding, enough to provide 103,480,000,000possible combinations, “guaranteed tobe unique against all conceivable odds,” in the words of christian de duve. that’s a lot ofpossibility a one followed by more than three billion zeroes. “it would take more than fivethousand average size books just to print that figure,” notes de duve. look at yourself in themirror and reflect upon the fact that you are beholding ten thousand trillion cells, and thatalmost every one of them holds two yards of densely compacted dna, and you begin toappreciate just how much of this stuff you carry around with you. if all your dna werewoven into a single fine strand, there would be enough of it to stretch from the earth to themoon and back not once or twice but again and again. altogether, according to onecalculation, you may have as much as twenty million kilometers of dna bundled up insideyou. your body, in short, loves to make dna and without it you couldn’t live. yet dna is notitself alive. no molecule is, but dna is, as it were, especially unalive. it is “among the mostnonreactive, chemically inert molecules in the living world,” in the words of the geneticistrichard lewontin. that is why it can be recovered from patches of long dried blood or semenin murder investigations and coaxed from the bones of ancient neandertals. it also explainswhy it took scientists so long to work out how a substance so mystifyingly low key so, in aword, lifeless could be at the very heart of life itself. as a known entity, dna has been around longer than you might think. it was discoveredas far back as 1869 by johann friedrich miescher, a swiss scientist working at the universityof tübingen in germany. while delving microscopically through the pus in surgicalbandages, miescher found a substance he didn’t recognize and called it nuclein (because itresided in the nuclei of cells). at the time, miescher did little more than note its existence, butnuclein clearly remained on his mind, for twenty three years later in a letter to his uncle heraised the possibility that such molecules could be the agents behind heredity. this was anextraordinary insight, but one so far in advance of the day’s scientific requirements that itattracted no attention at all. for most of the next half century the common assumption was that the material nowcalled deoxyribonucleic acid, or dna had at most a subsidiary role in matters of heredity. itwas too simple. it had just four basic components, called nucleotides, which was like having an alphabet of just four letters. how could you possibly write the story of life with such arudimentary alphabet? (the answer is that you do it in much the way that you create complexmessages with the simple dots and dashes of morse code by combining them.) dna didn’tdo anything at all, as far as anyone could tell. it just sat there in the nucleus, possibly bindingthe chromosome in some way or adding a splash of acidity on command or fulfilling someother trivial task that no one had yet thought of. the necessary complexity, it was thought,had to exist in proteins in the nucleus. there were, however, two problems with dismissing dna. first, there was so much of it:two yards in nearly every nucleus, so clearly the cells esteemed it in some important way. ontop of this, it kept turning up, like the suspect in a murder mystery, in experiments. in twostudies in particular, one involving the pneumonococcus bacterium and another involvingbacteriophages (viruses that infect bacteria), dna betrayed an importance that could only beexplained if its role were more central than prevailing thought allowed. the evidencesuggested that dna was somehow involved in the making of proteins, a process vital to life,yet it was also clear that proteins were being made outside the nucleus, well away from thedna that was supposedly directing their assembly. no one could understand how dna could possibly be getting messages to the proteins. theanswer, we now know, was rna, or ribonucleic acid, which acts as an interpreter betweenthe two. it is a notable oddity of biology that dna and proteins don’t speak the samelanguage. for almost four billion years they have been the living world’s great double act, andyet they answer to mutually incompatible codes, as if one spoke spanish and the other hindi.to communicate they need a mediator in the form of rna. working with a kind of chemicalclerk called a ribosome, rna translates information from a cell’s dna into terms proteinscan understand and act upon. however, by the early 1900s, where we resume our story, we were still a very long wayfrom understanding that, or indeed almost anything else to do with the confused business ofheredity. clearly there was a need for some inspired and clever experimentation, and happily the ageproduced a young person with the diligence and aptitude to undertake it. his name wasthomas hunt morgan, and in 1904, just four years after the timely rediscovery of mendel’sexperiments with pea plants and still almost a decade before gene would even become a word,he began to do remarkably dedicated things with chromosomes. chromosomes had been discovered by chance in 1888 and were so called because theyreadily absorbed dye and thus were easy to see under the microscope. by the turn of thetwentieth century it was strongly suspected that they were involved in the passing on of traits,but no one knew how, or even really whether, they did this. morgan chose as his subject of study a tiny, delicate fly formally called drosophilamelanogaster, but more commonly known as the fruit fly (or vinegar fly, banana fly, orgarbage fly). drosophila is familiar to most of us as that frail, colorless insect that seems tohave a compulsive urge to drown in our drinks. as laboratory specimens fruit flies had certainvery attractive advantages: they cost almost nothing to house and feed, could be bred by themillions in milk bottles, went from egg to productive parenthood in ten days or less, and hadjust four chromosomes, which kept things conveniently simple. working out of a small lab (which became known inevitably as the fly room) inschermerhorn hall at columbia university in new york, morgan and his team embarked ona program of meticulous breeding and crossbreeding involving millions of flies (onebiographer says billions, though that is probably an exaggeration), each of which had to becaptured with tweezers and examined under a jeweler’s glass for any tiny variations ininheritance. for six years they tried to produce mutations by any means they could think of zapping the flies with radiation and x rays, rearing them in bright light and darkness, bakingthem gently in ovens, spinning them crazily in centrifuges but nothing worked. morgan wason the brink of giving up when there occurred a sudden and repeatable mutation a fly thathad white eyes rather than the usual red ones. with this breakthrough, morgan and hisassistants were able to generate useful deformities, allowing them to track a trait throughsuccessive generations. by such means they could work out the correlations betweenparticular characteristics and individual chromosomes, eventually proving to more or lesseveryone’s satisfaction that chromosomes were at the heart of inheritance. the problem, however, remained the next level of biological intricacy: the enigmatic genesand the dna that composed them. these were much trickier to isolate and understand. aslate as 1933, when morgan was awarded a nobel prize for his work, many researchers stillweren’t convinced that genes even existed. as morgan noted at the time, there was noconsensus “as to what the genes are whether they are real or purely fictitious.” it may seemsurprising that scientists could struggle to accept the physical reality of something sofundamental to cellular activity, but as wallace, king, and sanders point out in biology: thescience of life (that rarest thing: a readable college text), we are in much the same positiontoday with mental processes such as thought and memory. we know that we have them, ofcourse, but we don’t know what, if any, physical form they take. so it was for the longest timewith genes. the idea that you could pluck one from your body and take it away for study wasas absurd to many of morgan’s peers as the idea that scientists today might capture a straythought and examine it under a microscope. what was certainly true was that something associated with chromosomes was directingcell replication. finally, in 1944, after fifteen years of effort, a team at the rockefellerinstitute in manhattan, led by a brilliant but diffident canadian named oswald avery,succeeded with an exceedingly tricky experiment in which an innocuous strain of bacteria wasmade permanently infectious by crossing it with alien dna, proving that dna was far morethan a passive molecule and almost certainly was the active agent in heredity. the austrian born biochemist erwin chargaff later suggested quite seriously that avery’s discovery wasworth two nobel prizes. unfortunately, avery was opposed by one of his own colleagues at the institute, a strong willed and disagreeable protein enthusiast named alfred mirsky, who did everything in hispower to discredit avery’s work including, it has been said, lobbying the authorities at thekarolinska institute in stockholm not to give avery a nobel prize. avery by this time wassixty six years old and tired. unable to deal with the stress and controversy, he resigned hisposition and never went near a lab again. but other experiments elsewhere overwhelminglysupported his conclusions, and soon the race was on to find the structure of dna. had you been a betting person in the early 1950s, your money would almost certainly havebeen on linus pauling of caltech, america’s leading chemist, to crack the structure of dna.pauling was unrivaled in determining the architecture of molecules and had been a pioneer inthe field of x ray crystallography, a technique that would prove crucial to peering into theheart of dna. in an exceedingly distinguished career, he would win two nobel prizes (for chemistry in 1954 and peace in 1962), but with dna he became convinced that the structurewas a triple helix, not a double one, and never quite got on the right track. instead, victory fellto an unlikely quartet of scientists in england who didn’t work as a team, often weren’t onspeaking terms, and were for the most part novices in the field. of the four, the nearest to a conventional boffin was maurice wilkins, who had spent muchof the second world war helping to design the atomic bomb. two of the others, rosalindfranklin and francis crick, had passed their war years working on mines for the britishgovernment crick of the type that blow up, franklin of the type that produce coal. the most unconventional of the foursome was james watson, an american prodigy whohad distinguished himself as a boy as a member of a highly popular radio program called thequiz kids (and thus could claim to be at least part of the inspiration for some of the membersof the glass family in franny and zooey and other works by j. d. salinger) and who hadentered the university of chicago aged just fifteen. he had earned his ph.d. by the age oftwenty two and was now attached to the famous cavendish laboratory in cambridge. in1951, he was a gawky twenty three year old with a strikingly lively head of hair that appearsin photographs to be straining to attach itself to some powerful magnet just out of frame. crick, twelve years older and still without a doctorate, was less memorably hirsute andslightly more tweedy. in watson’s account he is presented as blustery, nosy, cheerfullyargumentative, impatient with anyone slow to share a notion, and constantly in danger ofbeing asked to go elsewhere. neither was formally trained in biochemistry. their assumption was that if you could determine the shape of a dna molecule you wouldbe able to see correctly, as it turned out how it did what it did. they hoped to achieve this,it would appear, by doing as little work as possible beyond thinking, and no more of that thanwas absolutely necessary. as watson cheerfully (if a touch disingenuously) remarked in hisautobiographical book the double helix, “it was my hope that the gene might be solvedwithout my learning any chemistry.” they weren’t actually assigned to work on dna, and atone point were ordered to stop it. watson was ostensibly mastering the art of crystallography;crick was supposed to be completing a thesis on the x ray diffraction of large molecules. although crick and watson enjoy nearly all the credit in popular accounts for solving themystery of dna, their breakthrough was crucially dependent on experimental work done bytheir competitors, the results of which were obtained “fortuitously,” in the tactful words of thehistorian lisa jardine. far ahead of them, at least at the beginning, were two academics atking’s college in london, wilkins and franklin. the new zealand born wilkins was a retiring figure, almost to the point of invisibility. a1998 pbs documentary on the discovery of the structure of dna a feat for which he sharedthe 1962 nobel prize with crick and watson managed to overlook him entirely. the most enigmatic character of all was franklin. in a severely unflattering portrait,watson in the double helix depicted franklin as a woman who was unreasonable, secretive,chronically uncooperative, and this seemed especially to irritate him almost willfullyunsexy. he allowed that she “was not unattractive and might have been quite stunning had shetaken even a mild interest in clothes,” but in this she disappointed all expectations. she didn’t even use lipstick, he noted in wonder, while her dress sense “showed all the imagination ofenglish blue stocking adolescents.”1 however, she did have the best images in existence of the possible structure of dna,achieved by means of x ray crystallography, the technique perfected by linus pauling.crystallography had been used successfully to map atoms in crystals (hence“crystallography”), but dna molecules were a much more finicky proposition. only franklinwas managing to get good results from the process, but to wilkins’s perennial exasperationshe refused to share her findings. if franklin was not warmly forthcoming with her findings, she cannot be altogetherblamed. female academics at king’s in the 1950s were treated with a formalized disdain thatdazzles modern sensibilities (actually any sensibilities). however senior or accomplished,they were not allowed into the college’s senior common room but instead had to take theirmeals in a more utilitarian chamber that even watson conceded was “dingily pokey.” on topof this she was being constantly pressed at times actively harassed to share her results witha trio of men whose desperation to get a peek at them was seldom matched by more engagingqualities, like respect. “i’m afraid we always used to adopt let’s say a patronizing attitudetoward her,” crick later recalled. two of these men were from a competing institution and thethird was more or less openly siding with them. it should hardly come as a surprise that shekept her results locked away. that wilkins and franklin did not get along was a fact that watson and crick seem to haveexploited to their benefit. although crick and watson were trespassing rather unashamedlyon wilkins’s territory, it was with them that he increasingly sided not altogether surprisinglysince franklin herself was beginning to act in a decidedly queer way. although her resultsshowed that dna definitely was helical in shape, she insisted to all that it was not. towilkins’s presumed dismay and embarrassment, in the summer of 1952 she posted a mocknotice around the king’s physics department that said: “it is with great regret that we have toannounce the death, on friday 18th july 1952 of d.n.a. helix. . . . it is hoped that dr. m.h.f.wilkins will speak in memory of the late helix.” the outcome of all this was that in january 1953, wilkins showed watson franklin’simages, “apparently without her knowledge or consent.” it would be an understatement to callit a significant help. years later watson conceded that it “was the key event . . . it mobilizedus.” armed with the knowledge of the dna molecule’s basic shape and some importantelements of its dimensions, watson and crick redoubled their efforts. everything now seemedto go their way. at one point pauling was en route to a conference in england at which hewould in all likelihood have met with wilkins and learned enough to correct themisconceptions that had put him on the wrong line of inquiry, but this was the mccarthy eraand pauling found himself detained at idlewild airport in new york, his passport confiscated,on the grounds that he was too liberal of temperament to be allowed to travel abroad. crickand watson also had the no less convenient good fortune that pauling’s son was working atthe cavendish and innocently kept them abreast of any news of developments and setbacks athome. still facing the possibility of being trumped at any moment, watson and crick appliedthemselves feverishly to the problem. it was known that dna had four chemical1 in 1968, harvard university press canceled publication of the double helix after crick and wilkinscomplained about its characterizations, which the science historian lisa jardine has described as \"gratuitouslyhurtful.\" the descriptions quoted above are after watson softened his comments. components called adenine, guanine, cytosine, and thiamine and that these paired up inparticular ways. by playing with pieces of cardboard cut into the shapes of molecules, watsonand crick were able to work out how the pieces fit together. from this they made a meccano like model perhaps the most famous in modern science consisting of metal plates boltedtogether in a spiral, and invited wilkins, franklin, and the rest of the world to have a look.any informed person could see at once that they had solved the problem. it was withoutquestion a brilliant piece of detective work, with or without the boost of franklin’s picture. the april 25, 1953, edition of nature carried a 900 word article by watson and crick titled“a structure for deoxyribose nucleic acid.” accompanying it were separate articles bywilkins and franklin. it was an eventful time in the world edmund hillary was just about toclamber to the top of everest while elizabeth ii was imminently to be crowned queen ofengland so the discovery of the secret of life was mostly overlooked. it received a smallmention in the news chronicle and was ignored elsewhere. rosalind franklin did not share in the nobel prize. she died of ovarian cancer at the age ofjust thirty seven in 1958, four years before the award was granted. nobel prizes are notawarded posthumously. the cancer almost certainly arose as a result of chronic overexposureto x rays through her work and needn’t have happened. in her much praised 2002 biographyof franklin, brenda maddox noted that franklin rarely wore a lead apron and often steppedcarelessly in front of a beam. oswald avery never won a nobel prize either and was alsolargely overlooked by posterity, though he did at least have the satisfaction of living just longenough to see his findings vindicated. he died in 1955. watson and crick’s discovery wasn’t actually confirmed until the 1980s. as crick said inone of his books: “it took over twenty five years for our model of dna to go from being onlyrather plausible, to being very plausible . . . and from there to being virtually certainlycorrect.” even so, with the structure of dna understood progress in genetics was swift, and by 1968the journal science could run an article titled “that was the molecular biology that was,”suggesting it hardly seems possible, but it is so that the work of genetics was nearly at anend. in fact, of course, it was only just beginning. even now there is a great deal about dna thatwe scarcely understand, not least why so much of it doesn’t actually seem to do anything.ninety seven percent of your dna consists of nothing but long stretches of meaninglessgarble “junk,” or “non coding dna,” as biochemists prefer to put it. only here and therealong each strand do you find sections that control and organize vital functions. these are thecurious and long elusive genes. genes are nothing more (nor less) than instructions to make proteins. this they do with acertain dull fidelity. in this sense, they are rather like the keys of a piano, each playing asingle note and nothing else, which is obviously a trifle monotonous. but combine the genes,as you would combine piano keys, and you can create chords and melodies of infinite variety.put all these genes together, and you have (to continue the metaphor) the great symphony ofexistence known as the human genome. an alternative and more common way to regard the genome is as a kind of instructionmanual for the body. viewed this way, the chromosomes can be imagined as the book’schapters and the genes as individual instructions for making proteins. the words in which the instructions are written are called codons, and the letters are known as bases. the bases theletters of the genetic alphabet consist of the four nucleotides mentioned a page or two back:adenine, thiamine, guanine, and cytosine. despite the importance of what they do, thesesubstances are not made of anything exotic. guanine, for instance, is the same stuff thatabounds in, and gives its name to, guano. the shape of a dna molecule, as everyone knows, is rather like a spiral staircase ortwisted rope ladder: the famous double helix. the uprights of this structure are made of a typeof sugar called deoxyribose, and the whole of the helix is a nucleic acid hence the name“deoxyribonucleic acid.” the rungs (or steps) are formed by two bases joining across thespace between, and they can combine in only two ways: guanine is always paired withcytosine and thiamine always with adenine. the order in which these letters appear as youmove up or down the ladder constitutes the dna code; logging it has been the job of thehuman genome project. now the particular brilliance of dna lies in its manner of replication. when it is time toproduce a new dna molecule, the two strands part down the middle, like the zipper on ajacket, and each half goes off to form a new partnership. because each nucleotide along astrand pairs up with a specific other nucleotide, each strand serves as a template for thecreation of a new matching strand. if you possessed just one strand of your own dna, youcould easily enough reconstruct the matching side by working out the necessary partnerships:if the topmost rung on one strand was made of guanine, then you would know that thetopmost rung on the matching strand must be cytosine. work your way down the ladderthrough all the nucleotide pairings, and eventually you would have the code for a newmolecule. that is just what happens in nature, except that nature does it really quickly inonly a matter of seconds, which is quite a feat. most of the time our dna replicates with dutiful accuracy, but just occasionally aboutone time in a million a letter gets into the wrong place. this is known as a single nucleotidepolymorphism, or snp, familiarly known to biochemists as a “snip.” generally these snipsare buried in stretches of noncoding dna and have no detectable consequence for the body.but occasionally they make a difference. they might leave you predisposed to some disease,but equally they might confer some slight advantage more protective pigmentation, forinstance, or increased production of red blood cells for someone living at altitude. over time,these slight modifications accumulate in both individuals and in populations, contributing tothe distinctiveness of both. the balance between accuracy and errors in replication is a fine one. too many errors andthe organism can’t function, but too few and it sacrifices adaptability. a similar balance mustexist between stability in an organism and innovation. an increase in red blood cells can helpa person or group living at high elevations to move and breathe more easily because more redcells can carry more oxygen. but additional red cells also thicken the blood. add too many,and “it’s like pumping oil,” in the words of temple university anthropologist charles weitz.that’s hard on the heart. thus those designed to live at high altitude get increased breathingefficiency, but pay for it with higher risk hearts. by such means does darwinian naturalselection look after us. it also helps to explain why we are all so similar. evolution simplywon’t let you become too different not without becoming a new species anyway. the 0.1 percent difference between your genes and mine is accounted for by our snips.now if you compared your dna with a third person’s, there would also be 99.9 percentcorrespondence, but the snips would, for the most part, be in different places. add more people to the comparison and you will get yet more snips in yet more places. for every one ofyour 3.2 billion bases, somewhere on the planet there will be a person, or group of persons,with different coding in that position. so not only is it wrong to refer to “the” human genome,but in a sense we don’t even have “a” human genome. we have six billion of them. we are all99.9 percent the same, but equally, in the words of the biochemist david cox, “you could sayall humans share nothing, and that would be correct, too.” but we have still to explain why so little of that dna has any discernible purpose. it startsto get a little unnerving, but it does really seem that the purpose of life is to perpetuate dna.the 97 percent of our dna commonly called junk is largely made up of clumps of lettersthat, in ridley’s words, “exist for the pure and simple reason that they are good at gettingthemselves duplicated.”2 most of your dna, in other words, is not devoted to you but toitself: you are a machine for reproducing it, not it for you. life, you will recall, just wants tobe, and dna is what makes it so. even when dna includes instructions for making genes when it codes for them, asscientists put it it is not necessarily with the smooth functioning of the organism in mind.one of the commonest genes we have is for a protein called reverse transcriptase, which hasno known beneficial function in human beings at all. the one thing itdoes do is make itpossible for retroviruses, such as the aids virus, to slip unnoticed into the human system. in other words, our bodies devote considerable energies to producing a protein that doesnothing that is beneficial and sometimes clobbers us. our bodies have no choice but to do sobecause the genes order it. we are vessels for their whims. altogether, almost half of humangenes the largest proportion yet found in any organism don’t do anything at all, as far aswe can tell, except reproduce themselves. all organisms are in some sense slaves to their genes. that’s why salmon and spiders andother types of creatures more or less beyond counting are prepared to die in the process ofmating. the desire to breed, to disperse one’s genes, is the most powerful impulse in nature.as sherwin b. nuland has put it: “empires fall, ids explode, great symphonies are written,and behind all of it is a single instinct that demands satisfaction.” from an evolutionary pointof view, sex is really just a reward mechanism to encourage us to pass on our genetic material. scientists had only barely absorbed the surprising news that most of our dna doesn’t doanything when even more unexpected findings began to turn up. first in germany and then inswitzerland researchers performed some rather bizarre experiments that produced curiouslyunbizarre outcomes. in one they took the gene that controlled the development of a mouse’seye and inserted it into the larva of a fruit fly. the thought was that it might producesomething interestingly grotesque. in fact, the mouse eye gene not only made a viable eye inthe fruit fly, it made a fly’s eye. here were two creatures that hadn’t shared a commonancestor for 500 million years, yet could swap genetic material as if they were sisters. the story was the same wherever researchers looked. they found that they could inserthuman dna into certain cells of flies, and the flies would accept it as if it were their own.2 junk dna does have a use. it is the portion employed in dna fingerprinting. its practicality for this purposewas discovered accidentally by alec jeffreys, a scientist at the university of leicester in england. in 1986jeffreys was studying dna sequences for genetic markers associated with heritable diseases when he wasapproached by the police and asked if he could help connect a suspect to two murders. he realized his techniqueought to work perfectly for solving criminal cases and so it proved. a young baker with the improbable name ofcolin pitchfork was sentenced to two life terms in prison for the murders. over 60 percent of human genes, it turns out, are fundamentally the same as those found infruit flies. at least 90 percent correlate at some level to those found in mice. (we even havethe same genes for making a tail, if only they would switch on.) in field after field,researchers found that whatever organism they were working on whether nematode wormsor human beings they were often studying essentially the same genes. life, it appeared, wasdrawn up from a single set of blueprints. further probings revealed the existence of a clutch of master control genes, each directingthe development of a section of the body, which were dubbed homeotic (from a greek wordmeaning “similar”) or hox genes. hox genes answered the long bewildering question of howbillions of embryonic cells, all arising from a single fertilized egg and carrying identicaldna, know where to go and what to do that this one should become a liver cell, this one astretchy neuron, this one a bubble of blood, this one part of the shimmer on a beating wing. itis the hox genes that instruct them, and they do it for all organisms in much the same way. interestingly, the amount of genetic material and how it is organized doesn’t necessarily, oreven generally, reflect the level of sophistication of the creature that contains it. we haveforty six chromosomes, but some ferns have more than six hundred. the lungfish, one of theleast evolved of all complex animals, has forty times as much dna as we have. even thecommon newt is more genetically splendorous than we are, by a factor of five. clearly it is not the number of genes you have, but what you do with them. this is a verygood thing because the number of genes in humans has taken a big hit lately. until recently itwas thought that humans had at least 100,000 genes, possibly a good many more, but thatnumber was drastically reduced by the first results of the human genome project, whichsuggested a figure more like 35,000 or 40,000 genes about the same number as are found ingrass. that came as both a surprise and a disappointment. it won’t have escaped your attention that genes have been commonly implicated in anynumber of human frailties. exultant scientists have at various times declared themselves tohave found the genes responsible for obesity, schizophrenia, homosexuality, criminality,violence, alcoholism, even shoplifting and homelessness. perhaps the apogee (or nadir) of thisfaith in biodeterminism was a study published in the journal science in 1980 contending thatwomen are genetically inferior at mathematics. in fact, we now know, almost nothing aboutyou is so accommodatingly simple. this is clearly a pity in one important sense, for if you had individual genes that determinedheight or propensity to diabetes or to baldness or any other distinguishing trait, then it wouldbe easy comparatively easy anyway to isolate and tinker with them. unfortunately, thirty five thousand genes functioning independently is not nearly enough to produce the kind ofphysical complexity that makes a satisfactory human being. genes clearly therefore mustcooperate. a few disorders hemophilia, parkinson’s disease, huntington’s disease, andcystic fibrosis, for example are caused by lone dysfunctional genes, but as a rule disruptivegenes are weeded out by natural selection long before they can become permanentlytroublesome to a species or population. for the most part our fate and comfort and even oureye color are determined not by individual genes but by complexes of genes working inalliance. that’s why it is so hard to work out how it all fits together and why we won’t beproducing designer babies anytime soon. in fact, the more we have learned in recent years the more complicated matters have tendedto become. even thinking, it turns out, affects the ways genes work. how fast a man’s beard grows, for instance, is partly a function of how much he thinks about sex (because thinkingabout sex produces a testosterone surge). in the early 1990s, scientists made an even moreprofound discovery when they found they could knock out supposedly vital genes fromembryonic mice, and the mice were not only often born healthy, but sometimes were actuallyfitter than their brothers and sisters who had not been tampered with. when certain importantgenes were destroyed, it turned out, others were stepping in to fill the breach. this wasexcellent news for us as organisms, but not so good for our understanding of how cells worksince it introduced an extra layer of complexity to something that we had barely begun tounderstand anyway. it is largely because of these complicating factors that cracking the human genome becameseen almost at once as only a beginning. the genome, as eric lander of mit has put it, is likea parts list for the human body: it tells us what we are made of, but says nothing about howwe work. what’s needed now is the operating manual instructions for how to make it go.we are not close to that point yet. so now the quest is to crack the human proteome a concept so novel that the termproteome didn’t even exist a decade ago. the proteome is the library of information thatcreates proteins. “unfortunately,” observed scientific american in the spring of 2002, “theproteome is much more complicated than the genome.” that’s putting it mildly. proteins, you will remember, are the workhorses of all livingsystems; as many as a hundred million of them may be busy in any cell at any moment. that’sa lot of activity to try to figure out. worse, proteins’ behavior and functions are based notsimply on their chemistry, as with genes, but also on their shapes. to function, a protein mustnot only have the necessary chemical components, properly assembled, but then must also befolded into an extremely specific shape. “folding” is the term that’s used, but it’s amisleading one as it suggests a geometrical tidiness that doesn’t in fact apply. proteins loopand coil and crinkle into shapes that are at once extravagant and complex. they are more likefuriously mangled coat hangers than folded towels. moreover, proteins are (if i may be permitted to use a handy archaism) the swingers of thebiological world. depending on mood and metabolic circumstance, they will allowthemselves to be phosphorylated, glycosylated, acetylated, ubiquitinated, farneysylated,sulfated, and linked to glycophosphatidylinositol anchors, among rather a lot else. often ittakes relatively little to get them going, it appears. drink a glass of wine, as scientificamerican notes, and you materially alter the number and types of proteins at large in yoursystem. this is a pleasant feature for drinkers, but not nearly so helpful for geneticists who aretrying to understand what is going on. it can all begin to seem impossibly complicated, and in some ways itis impossiblycomplicated. but there is an underlying simplicity in all this, too, owing to an equallyelemental underlying unity in the way life works. all the tiny, deft chemical processes thatanimate cells the cooperative efforts of nucleotides, the transcription of dna into rna evolved just once and have stayed pretty well fixed ever since across the whole of nature. asthe late french geneticist jacques monod put it, only half in jest: “anything that is true of e.coli must be true of elephants, except more so.” every living thing is an elaboration on a single original plan. as humans we are mereincrements each of us a musty archive of adjustments, adaptations, modifications, andprovidential tinkerings stretching back 3.8 billion years. remarkably, we are even quite closely related to fruit and vegetables. about half the chemical functions that take place in abanana are fundamentally the same as the chemical functions that take place in you. it cannot be said too often: all life is one. that is, and i suspect will forever prove to be, themost profound true statement there is. part vi the road to us descended from the apes! my dear, let us hope that it is not true, but if it is, let us pray that it will not become generally known.  remark attributed to the wife of the bishop of worcester after darwin’s theory of evolution was explained to her 27 ice timei had a dream, which was not all a dream.the bright sun was extinguish’d, and the starsdid wander . . . byron, “darkness”in 1815 on the island of sumbawa in indonesia, a handsome and long quiescent mountainnamed tambora exploded spectacularly, killing a hundred thousand people with its blast andassociated tsunamis. it was the biggest volcanic explosion in ten thousand years 150 timesthe size of mount st. helens, equivalent to sixty thousand hiroshima sized atom bombs. news didn’t travel terribly fast in those days. in london, the times ran a small story actually a letter from a merchant seven months after the event. but by this time tambora’seffects were already being felt. thirty six cubic miles of smoky ash, dust, and grit haddiffused through the atmosphere, obscuring the sun’s rays and causing the earth to cool.sunsets were unusually but blearily colorful, an effect memorably captured by the artist j. m.w. turner, who could not have been happier, but mostly the world existed under anoppressive, dusky pall. it was this deathly dimness that inspired the byron lines above. spring never came and summer never warmed: 1816 became known as the year withoutsummer. crops everywhere failed to grow. in ireland a famine and associated typhoidepidemic killed sixty five thousand people. in new england, the year became popularlyknown as eighteen hundred and froze to death. morning frosts continued until june andalmost no planted seed would grow. short of fodder, livestock died or had to be prematurelyslaughtered. in every way it was a dreadful year almost certainly the worst for farmers inmodern times. yet globally the temperature fell by only about 1.5 degrees fahrenheit. earth’snatural thermostat, as scientists would learn, is an exceedingly delicate instrument. the nineteenth century was already a chilly time. for two hundred years europe and northamerica in particular had experienced a little ice age, as it has become known, whichpermitted all kinds of wintry events frost fairs on the thames, ice skating races along dutchcanals that are mostly impossible now. it was a period, in other words, when frigidity wasmuch on people’s minds. so we may perhaps excuse nineteenth century geologists for beingslow to realize that the world they lived in was in fact balmy compared with former epochs,and that much of the land around them had been shaped by crushing glaciers and cold thatwould wreck even a frost fair. they knew there was something odd about the past. the european landscape was litteredwith inexplicable anomalies the bones of arctic reindeer in the warm south of france, hugerocks stranded in improbable places and they often came up with inventive but not terribly plausible explanations. one french naturalist named de luc, trying to explain how graniteboulders had come to rest high up on the limestone flanks of the jura mountains, suggestedthat perhaps they had been shot there by compressed air in caverns, like corks out of apopgun. the term for a displaced boulder is an erratic, but in the nineteenth century theexpression seemed to apply more often to the theories than to the rocks. the great british geologist arthur hallam has suggested that if james hutton, the father ofgeology, had visited switzerland, he would have seen at once the significance of the carvedvalleys, the polished striations, the telltale strand lines where rocks had been dumped, and theother abundant clues that point to passing ice sheets. unfortunately, hutton was not a traveler.but even with nothing better at his disposal than secondhand accounts, hutton rejected out ofhand the idea that huge boulders had been carried three thousand feet up mountainsides byfloods all the water in the world won’t make a boulder float, he pointed out and becameone of the first to argue for widespread glaciation. unfortunately his ideas escaped notice, andfor another half century most naturalists continued to insist that the gouges on rocks could beattributed to passing carts or even the scrape of hobnailed boots. local peasants, uncontaminated by scientific orthodoxy, knew better, however. thenaturalist jean de charpentier told the story of how in 1834 he was walking along a countrylane with a swiss woodcutter when they got to talking about the rocks along the roadside. thewoodcutter matter of factly told him that the boulders had come from the grimsel, a zone ofgranite some distance away. “when i asked him how he thought that these stones had reachedtheir location, he answered without hesitation: ‘the grimsel glacier transported them on bothsides of the valley, because that glacier extended in the past as far as the town of bern.’ ” charpentier was delighted. he had come to such a view himself, but when he raised thenotion at scientific gatherings, it was dismissed. one of charpentier’s closest friends wasanother swiss naturalist, louis agassiz, who after some initial skepticism came to embrace,and eventually all but appropriate, the theory. agassiz had studied under cuvier in paris and now held the post of professor of naturalhistory at the college of neuchâtel in switzerland. another friend of agassiz’s, a botanistnamed karl schimper, was actually the first to coin the term ice age (in german eiszeit ), in1837, and to propose that there was good evidence to show that ice had once lain heavilyacross not just the swiss alps, but over much of europe, asia, and north america. it was aradical notion. he lent agassiz his notes then came very much to regret it as agassizincreasingly got the credit for what schimper felt, with some legitimacy, was his theory.charpentier likewise ended up a bitter enemy of his old friend. alexander von humboldt, yetanother friend, may have had agassiz at least partly in mind when he observed that there arethree stages in scientific discovery: first, people deny that it is true; then they deny that it isimportant; finally they credit the wrong person. at all events, agassiz made the field his own. in his quest to understand the dynamics ofglaciation, he went everywhere deep into dangerous crevasses and up to the summits of thecraggiest alpine peaks, often apparently unaware that he and his team were the first to climbthem. nearly everywhere agassiz encountered an unyielding reluctance to accept his theories.humboldt urged him to return to his area of real expertise, fossil fish, and give up this madobsession with ice, but agassiz was a man possessed by an idea. agassiz’s theory found even less support in britain, where most naturalists had never seena glacier and often couldn’t grasp the crushing forces that ice in bulk exerts. “could scratches and polish just be due to ice ?” asked roderick murchison in a mocking tone at one meeting,evidently imagining the rocks as covered in a kind of light and glassy rime. to his dying day,he expressed the frankest incredulity at those “ice mad” geologists who believed that glacierscould account for so much. william hopkins, a cambridge professor and leading member ofthe geological society, endorsed this view, arguing that the notion that ice could transportboulders presented “such obvious mechanical absurdities” as to make it unworthy of thesociety’s attention. undaunted, agassiz traveled tirelessly to promote his theory. in 1840 he read a paper to ameeting of the british association for the advancement of science in glasgow at which hewas openly criticized by the great charles lyell. the following year the geological society ofedinburgh passed a resolution conceding that there might be some general merit in the theorybut that certainly none of it applied to scotland. lyell did eventually come round. his moment of epiphany came when he realized that amoraine, or line of rocks, near his family estate in scotland, which he had passed hundreds oftimes, could only be understood if one accepted that a glacier had dropped them there. buthaving become converted, lyell then lost his nerve and backed off from public support of theice age idea. it was a frustrating time for agassiz. his marriage was breaking up, schimperwas hotly accusing him of the theft of his ideas, charpentier wouldn’t speak to him, and thegreatest living geologist offered support of only the most tepid and vacillating kind. in 1846, agassiz traveled to america to give a series of lectures and there at last found theesteem he craved. harvard gave him a professorship and built him a first rate museum, themuseum of comparative zoology. doubtless it helped that he had settled in new england,where the long winters encouraged a certain sympathy for the idea of interminable periods ofcold. it also helped that six years after his arrival the first scientific expedition to greenlandreported that nearly the whole of that semicontinent was covered in an ice sheet just like theancient one imagined in agassiz’s theory. at long last, his ideas began to find a realfollowing. the one central defect of agassiz’s theory was that his ice ages had no cause. butassistance was about to come from an unlikely quarter. in the 1860s, journals and other learned publications in britain began to receive papers onhydrostatics, electricity, and other scientific subjects from a james croll of anderson’suniversity in glasgow. one of the papers, on how variations in earth’s orbit might haveprecipitated ice ages, was published in the philosophical magazine in 1864 and wasrecognized at once as a work of the highest standard. so there was some surprise, and perhapsjust a touch of embarrassment, when it turned out that croll was not an academic at theuniversity, but a janitor. born in 1821, croll grew up poor, and his formal education lasted only to the age ofthirteen. he worked at a variety of jobs as a carpenter, insurance salesman, keeper of atemperance hotel before taking a position as a janitor at anderson’s (now the university ofstrathclyde) in glasgow. by somehow inducing his brother to do much of his work, he wasable to pass many quiet evenings in the university library teaching himself physics,mechanics, astronomy, hydrostatics, and the other fashionable sciences of the day, andgradually began to produce a string of papers, with a particular emphasis on the motions ofearth and their effect on climate. croll was the first to suggest that cyclical changes in the shape of earth’s orbit, fromelliptical (which is to say slightly oval) to nearly circular to elliptical again, might explain the onset and retreat of ice ages. no one had ever thought before to consider an astronomicalexplanation for variations in earth’s weather. thanks almost entirely to croll’s persuasivetheory, people in britain began to become more responsive to the notion that at some formertime parts of the earth had been in the grip of ice. when his ingenuity and aptitude wererecognized, croll was given a job at the geological survey of scotland and widely honored:he was made a fellow of the royal society in london and of the new york academy ofscience and given an honorary degree from the university of st. andrews, among much else. unfortunately, just as agassiz’s theory was at last beginning to find converts in europe, hewas busy taking it into ever more exotic territory in america. he began to find evidence forglaciers practically everywhere he looked, including near the equator. eventually he becameconvinced that ice had once covered the whole earth, extinguishing all life, which god hadthen re created. none of the evidence agassiz cited supported such a view. nonetheless, inhis adopted country his stature grew and grew until he was regarded as only slightly below adeity. when he died in 1873 harvard felt it necessary to appoint three professors to take hisplace. yet, as sometimes happens, his theories fell swiftly out of fashion. less than a decade afterhis death his successor in the chair of geology at harvard wrote that the “so called glacialepoch . . . so popular a few years ago among glacial geologists may now be rejected withouthesitation.” part of the problem was that croll’s computations suggested that the most recent ice ageoccurred eighty thousand years ago, whereas the geological evidence increasingly indicatedthat earth had undergone some sort of dramatic perturbation much more recently than that.without a plausible explanation for what might have provoked an ice age, the whole theoryfell into abeyance. there it might have remained for some time except that in the early 1900sa serbian academic named milutin milankovitch, who had no background in celestial motionsat all he was a mechanical engineer by training developed an unexpected interest in thematter. milankovitch realized that the problem with croll’s theory was not that it wasincorrect but that it was too simple. as earth moves through space, it is subject not just to variations in the length and shape ofits orbit, but also to rhythmic shifts in its angle of orientation to the sun its tilt and pitch andwobble all affecting the length and intensity of sunlight falling on any patch of land. inparticular it is subject to three changes in position, known formally as its obliquity,precession, and eccentricity, over long periods of time. milankovitch wondered if there mightbe a relationship between these complex cycles and the comings and goings of ice ages. thedifficulty was that the cycles were of widely different lengths of approximately 20,000,40,000, and 100,000 years, but varying in each case by up to a few thousand years whichmeant that determining their points of intersection over long spans of time involved a nearlyendless amount of devoted computation. essentially milankovitch had to work out the angleand duration of incoming solar radiation at every latitude on earth, in every season, for amillion years, adjusted for three ever changing variables. happily this was precisely the sort of repetitive toil that suited milankovitch’stemperament. for the next twenty years, even while on vacation, he worked ceaselessly withpencil and slide rule computing the tables of his cycles work that now could be completed ina day or two with a computer. the calculations all had to be made in his spare time, but in1914 milankovitch suddenly got a great deal of that when world war i broke out and he wasarrested owing to his position as a reservist in the serbian army. he spent most of the next four years under loose house arrest in budapest, required only to report to the police once aweek. the rest of his time was spent working in the library of the hungarian academy ofsciences. he was possibly the happiest prisoner of war in history. the eventual outcome of his diligent scribblings was the 1930 book mathematicalclimatology and the astronomical theory of climatic changes. milankovitch was right thatthere was a relationship between ice ages and planetary wobble, though like most people heassumed that it was a gradual increase in harsh winters that led to these long spells ofcoldness. it was a russian german meteorologist, wladimir köppen father in law of ourtectonic friend alfred wegener who saw that the process was more subtle, and rather moreunnerving, than that. the cause of ice ages, köppen decided, is to be found in cool summers, not brutal winters.if summers are too cool to melt all the snow that falls on a given area, more incoming sunlightis bounced back by the reflective surface, exacerbating the cooling effect and encouraging yetmore snow to fall. the consequence would tend to be self perpetuating. as snow accumulatedinto an ice sheet, the region would grow cooler, prompting more ice to accumulate. as theglaciologist gwen schultz has noted: “it is not necessarily the amount of snow that causes icesheets but the fact that snow, however little, lasts.” it is thought that an ice age could startfrom a single unseasonal summer. the leftover snow reflects heat and exacerbates the chillingeffect. “the process is self enlarging, unstoppable, and once the ice is really growing itmoves,” says mcphee. you have advancing glaciers and an ice age. in the 1950s, because of imperfect dating technology, scientists were unable to correlatemilankovitch’s carefully worked out cycles with the supposed dates of ice ages as thenperceived, and so milankovitch and his calculations increasingly fell out of favor. he died in1958, unable to prove that his cycles were correct. by this time, write john and mary gribbin,“you would have been hard pressed to find a geologist or meteorologist who regarded themodel as being anything more than an historical curiosity.” not until the 1970s and therefinement of a potassium argon method for dating ancient seafloor sediments were histheories finally vindicated. the milankovitch cycles alone are not enough to explain cycles of ice ages. many otherfactors are involved not least the disposition of the continents, in particular the presence oflandmasses over the poles but the specifics of these are imperfectly understood. it has beensuggested, however, that if you hauled north america, eurasia, and greenland just threehundred miles north we would have permanent and inescapable ice ages. we are very lucky, itappears, to get any good weather at all. even less well understood are the cycles ofcomparative balminess within ice ages, known as interglacials. it is mildly unnerving toreflect that the whole of meaningful human history the development of farming, the creationof towns, the rise of mathematics and writing and science and all the rest has taken placewithin an atypical patch of fair weather. previous interglacials have lasted as little as eightthousand years. our own has already passed its ten thousandth anniversary. the fact is, we are still very much in an ice age; it’s just a somewhat shrunken one thoughless shrunken than many people realize. at the height of the last period of glaciation, aroundtwenty thousand years ago, about 30 percent of the earth’s land surface was under ice. tenpercent still is and a further 14 percent is in a state of permafrost. three quarters of all thefresh water on earth is locked up in ice even now, and we have ice caps at both poles asituation that may be unique in earth’s history. that there are snowy winters through much of the world and permanent glaciers even in temperate places such as new zealand may seemquite natural, but in fact it is a most unusual situation for the planet. for most of its history until fairly recent times the general pattern for earth was to be hotwith no permanent ice anywhere. the current ice age ice epoch really started about fortymillion years ago, and has ranged from murderously bad to not bad at all. ice ages tend towipe out evidence of earlier ice ages, so the further back you go the more sketchy the picturegrows, but it appears that we have had at least seventeen severe glacial episodes in the last 2.5million years or so the period that coincides with the rise of homo erectus in africafollowed by modern humans. two commonly cited culprits for the present epoch are the riseof the himalayas and the formation of the isthmus of panama, the first disrupting air flows,the second ocean currents. india, once an island, has pushed two thousand kilometers into theasian landmass over the last forty five million years, raising not only the himalayas, but alsothe vast tibetan plateau behind them. the hypothesis is that the higher landscape was notonly cooler, but diverted winds in a way that made them flow north and toward northamerica, making it more susceptible to long term chills. then, beginning about five millionyears ago, panama rose from the sea, closing the gap between north and south america,disrupting the flows of warming currents between the pacific and atlantic, and changingpatterns of precipitation across at least half the world. one consequence was a drying out ofafrica, which caused apes to climb down out of trees and go looking for a new way of livingon the emerging savannas. at all events, with the oceans and continents arranged as they are now, it appears that icewill be a long term part of our future. according to john mcphee, about fifty more glacialepisodes can be expected, each lasting a hundred thousand years or so, before we can hope fora really long thaw. before fifty million years ago, earth had no regular ice ages, but when we did have themthey tended to be colossal. a massive freezing occurred about 2.2 billion years ago, followedby a billion years or so of warmth. then there was another ice age even larger than the first so large that some scientists are now referring to the age in which it occurred as thecryogenian, or super ice age. the condition is more popularly known as snowball earth. “snowball,” however, barely captures the murderousness of conditions. the theory is thatbecause of a fall in solar radiation of about 6 percent and a dropoff in the production (orretention) of greenhouse gases, earth essentially lost its ability to hold on to its heat. itbecame a kind of all over antarctica. temperatures plunged by as much as 80 degreesfahrenheit. the entire surface of the planet may have frozen solid, with ocean ice up to half amile thick at higher latitudes and tens of yards thick even in the tropics. there is a serious problem in all this in that the geological evidence indicates iceeverywhere, including around the equator, while the biological evidence suggests just asfirmly that there must have been open water somewhere. for one thing, cyanobacteriasurvived the experience, and they photosynthesize. for that they needed sunlight, but as youwill know if you have ever tried to peer through it, ice quickly becomes opaque and after onlya few yards would pass on no light at all. two possibilities have been suggested. one is that alittle ocean water did remain exposed (perhaps because of some kind of localized warming ata hot spot); the other is that maybe the ice formed in such a way that it remained translucent a condition that does sometimes happen in nature. if earth did freeze over, then there is the very difficult question of how it ever got warmagain. an icy planet should reflect so much heat that it would stay frozen forever. it appearsthat rescue may have come from our molten interior. once again, we may be indebted totectonics for allowing us to be here. the idea is that we were saved by volcanoes, whichpushed through the buried surface, pumping out lots of heat and gases that melted the snowsand re formed the atmosphere. interestingly, the end of this hyper frigid episode is marked bythe cambrian outburst the springtime event of life’s history. in fact, it may not have been astranquil as all that. as earth warmed, it probably had the wildest weather it has everexperienced, with hurricanes powerful enough to raise waves to the heights of skyscrapersand rainfalls of indescribable intensity. throughout all this the tubeworms and clams and other life forms adhering to deep oceanvents undoubtedly went on as if nothing were amiss, but all other life on earth probably cameas close as it ever has to checking out entirely. it was all a long time ago and at this stage wejust don’t know. compared with a cryogenian outburst, the ice ages of more recent times seem pretty smallscale, but of course they were immensely grand by the standards of anything to be found onearth today. the wisconsian ice sheet, which covered much of europe and north america,was two miles thick in places and marched forward at a rate of about four hundred feet a year.what a thing it must have been to behold. even at their leading edge, the ice sheets could benearly half a mile thick. imagine standing at the base of a wall of ice two thousand feet high.behind this edge, over an area measuring in the millions of square miles, would be nothingbut more ice, with only a few of the tallest mountain summits poking through. wholecontinents sagged under the weight of so much ice and even now, twelve thousand years afterthe glaciers’ withdrawal, are still rising back into place. the ice sheets didn’t just dribble outboulders and long lines of gravelly moraines, but dumped entire landmasses long islandand cape cod and nantucket, among others as they slowly swept along. it’s little wonderthat geologists before agassiz had trouble grasping their monumental capacity to reworklandscapes. if ice sheets advanced again, we have nothing in our armory that could deflect them. in1964, at prince william sound in alaska, one of the largest glacial fields in north americawas hit by the strongest earthquake ever recorded on the continent. it measured 9.2 on therichter scale. along the fault line, the land rose by as much as twenty feet. the quake was soviolent, in fact, that it made water slosh out of pools in texas. and what effect did thisunparalleled outburst have on the glaciers of prince william sound? none at all. they justsoaked it up and kept on moving. for a long time it was thought that we moved into and out of ice ages gradually, overhundreds of thousands of years, but we now know that that has not been the case. thanks toice cores from greenland we have a detailed record of climate for something over a hundredthousand years, and what is found there is not comforting. it shows that for most of its recenthistory earth has been nothing like the stable and tranquil place that civilization has known,but rather has lurched violently between periods of warmth and brutal chill. toward the end of the last big glaciation, some twelve thousand years ago, earth began towarm, and quite rapidly, but then abruptly plunged back into bitter cold for a thousand yearsor so in an event known to science as the younger dryas. (the name comes from the arcticplant the dryas, which is one of the first to recolonize land after an ice sheet withdraws. therewas also an older dryas period, but it wasn’t so sharp.) at the end of this thousand year onslaught average temperatures leapt again, by as much as seven degrees in twenty years,which doesn’t sound terribly dramatic but is equivalent to exchanging the climate ofscandinavia for that of the mediterranean in just two decades. locally, changes have beeneven more dramatic. greenland ice cores show the temperatures there changing by as much asfifteen degrees in ten years, drastically altering rainfall patterns and growing conditions. thismust have been unsettling enough on a thinly populated planet. today the consequenceswould be pretty well unimaginable. what is most alarming is that we have no idea none what natural phenomena could soswiftly rattle earth’s thermometer. as elizabeth kolbert, writing in the new yorker, hasobserved: “no known external force, or even any that has been hypothesized, seems capableof yanking the temperature back and forth as violently, and as often, as these cores haveshown to be the case.” there seems to be, she adds, “some vast and terrible feedback loop,”probably involving the oceans and disruptions of the normal patterns of ocean circulation, butall this is a long way from being understood. one theory is that the heavy inflow of meltwater to the seas at the beginning of theyounger dryas reduced the saltiness (and thus density) of northern oceans, causing the gulfstream to swerve to the south, like a driver trying to avoid a collision. deprived of the gulfstream’s warmth, the northern latitudes returned to chilly conditions. but this doesn’t begin toexplain why a thousand years later when the earth warmed once again the gulf stream didn’tveer as before. instead, we were given the period of unusual tranquility known as theholocene, the time in which we live now. there is no reason to suppose that this stretch of climatic stability should last much longer.in fact, some authorities believe that we are in for even worse than what went before. it isnatural to suppose that global warming would act as a useful counterweight to the earth’stendency to plunge back into glacial conditions. however, as kolbert has pointed out, whenyou are confronted with a fluctuating and unpredictable climate “the last thing you’d want todo is conduct a vast unsupervised experiment on it.” it has even been suggested, with moreplausibility than would at first seem evident, that an ice age might actually be induced by arise in temperatures. the idea is that a slight warming would enhance evaporation rates andincrease cloud cover, leading in the higher latitudes to more persistent accumulations of snow.in fact, global warming could plausibly, if paradoxically, lead to powerful localized cooling innorth america and northern europe. climate is the product of so many variables rising and falling carbon dioxide levels, theshifts of continents, solar activity, the stately wobbles of the milankovitch cycles that it is asdifficult to comprehend the events of the past as it is to predict those of the future. much issimply beyond us. take antarctica. for at least twenty million years after it settled over thesouth pole antarctica remained covered in plants and free of ice. that simply shouldn’t havebeen possible. no less intriguing are the known ranges of some late dinosaurs. the british geologiststephen drury notes that forests within 10 degrees latitude of the north pole were home togreat beasts, including tyrannosaurus rex. “that is bizarre,” he writes, “for such a highlatitude is continually dark for three months of the year.” moreover, there is now evidencethat these high latitudes suffered severe winters. oxygen isotope studies suggest that theclimate around fairbanks, alaska, was about the same in the late cretaceous period as it isnow. so what was tyrannosaurus doing there? either it migrated seasonally over enormousdistances or it spent much of the year in snowdrifts in the dark. in australia which at that time was more polar in its orientation a retreat to warmer climes wasn’t possible. howdinosaurs managed to survive in such conditions can only be guessed. one thought to bear in mind is that if the ice sheets did start to form again for whateverreason, there is a lot more water for them to draw on this time. the great lakes, hudson bay,the countless lakes of canada these weren’t there to fuel the last ice age. they were createdby it. on the other hand, the next phase of our history could see us melting a lot of ice rather thanmaking it. if all the ice sheets melted, sea levels would rise by two hundred feet the heightof a twenty story building and every coastal city in the world would be inundated. morelikely, at least in the short term, is the collapse of the west antarctic ice sheet. in the past fiftyyears the waters around it have warmed by 2.5 degrees centigrade, and collapses haveincreased dramatically. because of the underlying geology of the area, a large scale collapseis all the more possible. if so, sea levels globally would rise and pretty quickly by betweenfifteen and twenty feet on average. the extraordinary fact is that we don’t know which is more likely, a future offering us eonsof perishing frigidity or one giving us equal expanses of steamy heat. only one thing iscertain: we live on a knife edge. in the long run, incidentally, ice ages are by no means bad news for the planet. they grindup rocks and leave behind new soils of sumptuous richness, and gouge out fresh water lakesthat provide abundant nutritive possibilities for hundreds of species of being. they act as aspur to migration and keep the planet dynamic. as tim flannery has remarked: “there is onlyone question you need ask of a continent in order to determine the fate of its people: ‘did youhave a good ice age?’ ” and with that in mind, it’s time to look at a species of ape that trulydid. 28 the mysterious bipedjust before christmas 1887, a young dutch doctor with an un dutch name, marieeugène françois thomas dubois, arrived in sumatra, in the dutch east indies, with theintention of finding the earliest human remains on earth.1 several things were extraordinary about this. to begin with, no one had ever gone lookingfor ancient human bones before. everything that had been found to this point had been foundaccidentally, and nothing in dubois’s background suggested that he was the ideal candidate tomake the process intentional. he was an anatomist by training with no background inpaleontology. nor was there any special reason to suppose that the east indies would holdearly human remains. logic dictated that if ancient people were to be found at all, it would beon a large and long populated landmass, not in the comparative fastness of an archipelago.dubois was driven to the east indies on nothing stronger than a hunch, the availability ofemployment, and the knowledge that sumatra was full of caves, the environment in whichmost of the important hominid fossils had so far been found. what is most extraordinary in allthis nearly miraculous, really is that he found what he was looking for. at the time dubois conceived his plan to search for a missing link, the human fossil recordconsisted of very little: five incomplete neandertal skeletons, one partial jawbone of uncertainprovenance, and a half dozen ice age humans recently found by railway workers in a cave at acliff called cro magnon near les eyzies, france. of the neandertal specimens, the bestpreserved was sitting unremarked on a shelf in london. it had been found by workers blastingrock from a quarry in gibraltar in 1848, so its preservation was a wonder, but unfortunatelyno one yet appreciated what it was. after being briefly described at a meeting of the gibraltarscientific society, it had been sent to the hunterian museum in london, where it remainedundisturbed but for an occasional light dusting for over half a century. the first formaldescription of it wasn’t written until 1907, and then by a geologist named william sollas“with only a passing competency in anatomy.” so instead the name and credit for the discovery of the first early humans went to theneander valley in germany not unfittingly, as it happens, for by uncanny coincidenceneander in greek means “new man.” there in 1856 workmen at another quarry, in a cliff faceoverlooking the düssel river, found some curious looking bones, which they passed to alocal schoolteacher, knowing he had an interest in all things natural. to his great credit theteacher, johann karl fuhlrott, saw that he had some new type of human, though quite what itwas, and how special, would be matters of dispute for some time. many people refused to accept that the neandertal bones were ancient at all. august mayer,a professor at the university of bonn and a man of influence, insisted that the bones were1 though dutch, dubois was from eijsden, a town bordering the french speaking part of belgium. merely those of a mongolian cossack soldier who had been wounded while fighting ingermany in 1814 and had crawled into the cave to die. hearing of this, t. h. huxley inengland drily observed how remarkable it was that the soldier, though mortally wounded, hadclimbed sixty feet up a cliff, divested himself of his clothing and personal effects, sealed thecave opening, and buried himself under two feet of soil. another anthropologist, puzzlingover the neandertal’s heavy brow ridge, suggested that it was the result of long term frowningarising from a poorly healed forearm fracture. (in their eagerness to reject the idea of earlierhumans, authorities were often willing to embrace the most singular possibilities. at about thetime that dubois was setting out for sumatra, a skeleton found in périgueux was confidentlydeclared to be that of an eskimo. quite what an ancient eskimo was doing in southwestfrance was never comfortably explained. it was actually an early cro magnon.) it was against this background that dubois began his search for ancient human bones. hedid no digging himself, but instead used fifty convicts lent by the dutch authorities. for a yearthey worked on sumatra, then transferred to java. and there in 1891, dubois or rather histeam, for dubois himself seldom visited the sites found a section of ancient human craniumnow known as the trinil skullcap. though only part of a skull, it showed that the owner hadhad distinctly nonhuman features but a much larger brain than any ape. dubois called itanthropithecus erectus (later changed for technical reasons to pithecanthropus erectus) anddeclared it the missing link between apes and humans. it quickly became popularized as “javaman.” today we know it as homo erectus. the next year dubois’s workers found a virtually complete thighbone that lookedsurprisingly modern. in fact, many anthropologists think itis modern, and has nothing to dowith java man. if it is an erectus bone, it is unlike any other found since. nonetheless duboisused the thighbone to deduce correctly, as it turned out that pithecanthropus walkedupright. he also produced, with nothing but a scrap of cranium and one tooth, a model of thecomplete skull, which also proved uncannily accurate. in 1895, dubois returned to europe, expecting a triumphal reception. in fact, he met nearlythe opposite reaction. most scientists disliked both his conclusions and the arrogant manner inwhich he presented them. the skullcap, they said, was that of an ape, probably a gibbon, andnot of any early human. hoping to bolster his case, in 1897 dubois allowed a respectedanatomist from the university of strasbourg, gustav schwalbe, to make a cast of the skullcap.to dubois’s dismay, schwalbe thereupon produced a monograph that received far moresympathetic attention than anything dubois had written and followed with a lecture tour inwhich he was celebrated nearly as warmly as if he had dug up the skull himself. appalled andembittered, dubois withdrew into an undistinguished position as a professor of geology at theuniversity of amsterdam and for the next two decades refused to let anyone examine hisprecious fossils again. he died in 1940 an unhappy man. meanwhile, and half a world away, in late 1924 raymond dart, the australian born head ofanatomy at the university of the witwatersrand in johannesburg, was sent a small butremarkably complete skull of a child, with an intact face, a lower jaw, and what is known asan endocast a natural cast of the brain from a limestone quarry on the edge of the kalaharidesert at a dusty spot called taung. dart could see at once that the taung skull was not of ahomo erectus like dubois’s java man, but from an earlier, more apelike creature. he placedits age at two million years and dubbed it australopithecus africanus, or “southern ape man ofafrica.” in a report to nature, dart called the taung remains “amazingly human” and suggested the need for an entirely new family, homo simiadae (“the man apes”), toaccommodate the find. the authorities were even less favorably disposed to dart than they had been to dubois.nearly everything about his theory indeed, nearly everything about dart, it appears annoyed them. first he had proved himself lamentably presumptuous by conducting theanalysis himself rather than calling on the help of more worldly experts in europe. even hischosen name, australopithecus, showed a lack of scholarly application, combining as it didgreek and latin roots. above all, his conclusions flew in the face of accepted wisdom.humans and apes, it was agreed, had split apart at least fifteen million years ago in asia. ifhumans had arisen in africa, why, that would make us negroid, for goodness sake. it wasrather as if someone working today were to announce that he had found the ancestral bones ofhumans in, say, missouri. it just didn’t fit with what was known. dart’s sole supporter of note was robert broom, a scottish born physician andpaleontologist of considerable intellect and cherishably eccentric nature. it was broom’shabit, for instance, to do his fieldwork naked when the weather was warm, which was often.he was also known for conducting dubious anatomical experiments on his poorer and moretractable patients. when the patients died, which was also often, he would sometimes burytheir bodies in his back garden to dig up for study later. broom was an accomplished paleontologist, and since he was also resident in south africahe was able to examine the taung skull at first hand. he could see at once that it was asimportant as dart supposed and spoke out vigorously on dart’s behalf, but to no effect. forthe next fifty years the received wisdom was that the taung child was an ape and nothingmore. most textbooks didn’t even mention it. dart spent five years working up a monograph,but could find no one to publish it. eventually he gave up the quest to publish altogether(though he did continue hunting for fossils). for years, the skull today recognized as one ofthe supreme treasures of anthropology sat as a paperweight on a colleague’s desk. at the time dart made his announcement in 1924, only four categories of ancient hominidwere known homo heidelbergensis, homo rhodesiensis, neandertals, and dubois’s javaman but all that was about to change in a very big way. first, in china, a gifted canadian amateur named davidson black began to poke around ata place, dragon bone hill, that was locally famous as a hunting ground for old bones.unfortunately, rather than preserving the bones for study, the chinese ground them up tomake medicines. we can only guess how many priceless homo erectus bones ended up as asort of chinese equivalent of bicarbonate of soda. the site had been much denuded by thetime black arrived, but he found a single fossilized molar and on the basis of that alone quitebrilliantly announced the discovery of sinanthropus pekinensis, which quickly became knownas peking man. at black’s urging, more determined excavations were undertaken and many other bonesfound. unfortunately all were lost the day after the japanese attack on pearl harbor in 1941when a contingent of u.s. marines, trying to spirit the bones (and themselves) out of thecountry, was intercepted by the japanese and imprisoned. seeing that their crates held nothingbut bones, the japanese soldiers left them at the roadside. it was the last that was ever seen ofthem. in the meantime, back on dubois’s old turf of java, a team led by ralph von koenigswaldhad found another group of early humans, which became known as the solo people from thesite of their discovery on the solo river at ngandong. koenigswald’s discoveries might havebeen more impressive still but for a tactical error that was realized too late. he had offeredlocals ten cents for every piece of hominid bone they could come up with, then discovered tohis horror that they had been enthusiastically smashing large pieces into small ones tomaximize their income. in the following years as more bones were found and identified there came a flood of newnames homo aurignacensis, australopithecus transvaalensis, paranthropus crassidens,zinjanthropus boisei,and scores of others, nearly all involving a new genus type as well as anew species. by the 1950s, the number of named hominid types had risen to comfortably overa hundred. to add to the confusion, individual forms often went by a succession of differentnames as paleoanthropologists refined, reworked, and squabbled over classifications. solopeople were known variously as homo soloensis, homo primigenius asiaticus, homoneanderthalensis soloensis, homo sapiens soloensis, homo erectus erectus, and, finally, plainhomo erectus . in an attempt to introduce some order, in 1960 f. clark howell of the university ofchicago, following the suggestions of ernst mayr and others the previous decade, proposedcutting the number of genera to just two australopithecus and homo  and rationalizingmany of the species. the java and peking men both became homo erectus. for a time orderprevailed in the world of the hominids.2 it didn’t last. after about a decade of comparative calm, paleoanthropology embarked on another periodof swift and prolific discovery, which hasn’t abated yet. the 1960s produced homo habilis,thought by some to be the missing link between apes and humans, but thought by others not tobe a separate species at all. then came (among many others) homo ergaster, homolouisleakeyi, homo rudolfensis, homo microcranus, and homo antecessor, as well as a raft ofaustralopithecines: a.afarensis, a. praegens, a. ramidus, a. walkeri, a. anamensis, and stillothers. altogether, some twenty types of hominid are recognized in the literature today.unfortunately, almost no two experts recognize the same twenty. some continue to observe the two hominid genera suggested by howell in 1960, but othersplace some of the australopithecines in a separate genus called paranthropus , and still othersadd an earlier group called ardipithecus. some put praegens into australopithecus and someinto a new classification, homo antiquus, but most don’t recognize praegens as a separatespecies at all. there is no central authority that rules on these things. the only way a namebecomes accepted is by consensus, and there is often very little of that. a big part of the problem, paradoxically, is a shortage of evidence. since the dawn of time,several billion human (or humanlike) beings have lived, each contributing a little geneticvariability to the total human stock. out of this vast number, the whole of our understandingof human prehistory is based on the remains, often exceedingly fragmentary, of perhaps fivethousand individuals. “you could fit it all into the back of a pickup truck if you didn’t mind2 humans are put in the lamely homimdae. its members, traditionally called hominids, include any creatures(including extinct ones) that are more closely related to us than to any surviving chimpanzees. the apes,meanwhile, are lumped together in a family called pongidae. many authorities believe that chimps, gorillas, andorangutans should also be included in this family, with humans and chimps in a subfamily called homininae.the upshot is that the creatures traditionally called hominids become, under this arrangement, hominins. (leakeyand others insist on that designation.) hominoidea is the name of the aue sunerfamily which includes us. how much you jumbled everything up,” ian tattersall, the bearded and friendly curator ofanthropology at the american museum of natural history in new york, replied when i askedhim the size of the total world archive of hominid and early human bones. the shortage wouldn’t be so bad if the bones were distributed evenly through time andspace, but of course they are not. they appear randomly, often in the most tantalizing fashion.homo erectus walked the earth for well over a million years and inhabited territory from theatlantic edge of europe to the pacific side of china, yet if you brought back to life everyhomo erectus individual whose existence we can vouch for, they wouldn’t fill a school bus.homo habilis consists of even less: just two partial skeletons and a number of isolated limbbones. something as short lived as our own civilization would almost certainly not be knownfrom the fossil record at all. “in europe,” tattersall offers by way of illustration, “you’ve got hominid skulls in georgiadated to about 1.7 million years ago, but then you have a gap of almost a million years beforethe next remains turn up in spain, right on the other side of the continent, and then you’ve gotanother 300,000 year gap before you get a homo heidelbergensis in germany and none ofthem looks terribly much like any of the others.” he smiled. “it’s from these kinds offragmentary pieces that you’re trying to work out the histories of entire species. it’s quite atall order. we really have very little idea of the relationships between many ancient species which led to us and which were evolutionary dead ends. some probably don’t deserve to beregarded as separate species at all.” it is the patchiness of the record that makes each new find look so sudden and distinct fromall the others. if we had tens of thousands of skeletons distributed at regular intervals throughthe historical record, there would be appreciably more degrees of shading. whole new speciesdon’t emerge instantaneously, as the fossil record implies, but gradually out of other, existingspecies. the closer you go back to a point of divergence, the closer the similarities are, so thatit becomes exceedingly difficult, and sometimes impossible, to distinguish a late homoerectus from an early homo sapiens, since it is likely to be both and neither. similardisagreements can often arise over questions of identification from fragmentary remains deciding, for instance, whether a particular bone represents a female australopithecus boiseior a male homo habilis.with so little to be certain about, scientists often have to make assumptions based on otherobjects found nearby, and these may be little more than valiant guesses. as alan walker andpat shipman have drily observed, if you correlate tool discovery with the species of creaturemost often found nearby, you would have to conclude that early hand tools were mostly madeby antelopes. perhaps nothing better typifies the confusion than the fragmentary bundle of contradictionsthat was homo habilis. simply put, habilis bones make no sense. when arranged in sequence,they show males and females evolving at different rates and in different directions the malesbecoming less apelike and more human with time, while females from the same period appearto be moving away from humanness toward greater apeness. some authorities don’t believehabilis is a valid category at all. tattersall and his colleague jeffrey schwartz dismiss it as amere “wastebasket species” one into which unrelated fossils “could be conveniently swept.”even those who see habilis as an independent species don’t agree on whether it is of the samegenus as us or is from a side branch that never came to anything. finally, but perhaps above all, human nature is a factor in all this. scientists have a naturaltendency to interpret finds in the way that most flatters their stature. it is a rare paleontologistindeed who announces that he has found a cache of bones but that they are nothing to getexcited about. or as john reader understatedly observes in the book missing links, “it isremarkable how often the first interpretations of new evidence have confirmed thepreconceptions of its discoverer.” all this leaves ample room for arguments, of course, and nobody likes to argue more thanpaleoanthropologists. “and of all the disciplines in science, paleoanthropology boasts perhapsthe largest share of egos,” say the authors of the recent java man  a book, it may be noted,that itself devotes long, wonderfully unselfconscious passages to attacks on the inadequaciesof others, in particular the authors’ former close colleague donald johanson. here is a smallsampling: in our years of collaboration at the institute he [johanson] developed a well  deserved, if unfortunate, reputation for unpredictable and high decibel personal verbal assaults, sometimes accompanied by the tossing around of books or whatever else came conveniently to hand. so, bearing in mind that there is little you can say about human prehistory that won’t bedisputed by someone somewhere, other than that we most certainly had one, what we thinkwe know about who we are and where we come from is roughly this: for the first 99.99999 percent of our history as organisms, we were in the same ancestralline as chimpanzees. virtually nothing is known about the prehistory of chimpanzees, butwhatever they were, we were. then about seven million years ago something major happened.a group of new beings emerged from the tropical forests of africa and began to move abouton the open savanna. these were the australopithecines, and for the next five million years they would be theworld’s dominant hominid species. (austral is from the latin for “southern” and has noconnection in this context to australia.) australopithecines came in several varieties, someslender and gracile, like raymond dart’s taung child, others more sturdy and robust, but allwere capable of walking upright. some of these species existed for well over a million years,others for a more modest few hundred thousand, but it is worth bearing in mind that even theleast successful had histories many times longer than we have yet achieved. the most famous hominid remains in the world are those of a 3.18 million year oldaustralopithecine found at hadar in ethiopia in 1974 by a team led by donald johanson.formally known as a.l. (for “afar locality”) 288 1, the skeleton became more familiarlyknown as lucy, after the beatles song “lucy in the sky with diamonds.” johanson has neverdoubted her importance. “she is our earliest ancestor, the missing link between ape andhuman,” he has said. lucy was tiny just three and a half feet tall. she could walk, though how well is a matterof some dispute. she was evidently a good climber, too. much else is unknown. her skull wasalmost entirely missing, so little could be said with confidence about her brain size, thoughskull fragments suggested it was small. most books describe lucy’s skeleton as being 40percent complete, though some put it closer to half, and one produced by the americanmuseum of natural history describes lucy as two thirds complete. the bbc television series ape man actually called it “a complete skeleton,” even while showing that it was anythingbut. a human body has 206 bones, but many of these are repeated. if you have the left femurfrom a specimen, you don’t need the right to know its dimensions. strip out all the redundantbones, and the total you are left with is 120 what is called a half skeleton. even by this fairlyaccommodating standard, and even counting the slightest fragment as a full bone, lucyconstituted only 28 percent of a half skeleton (and only about 20 percent of a full one). in the wisdom of the bones, alan walker recounts how he once asked johanson how hehad come up with a figure of 40 percent. johanson breezily replied that he had discounted the106 bones of the hands and feet more than half the body’s total, and a fairly important half,too, one would have thought, since lucy’s principal defining attribute was the use of thosehands and feet to deal with a changing world. at all events, rather less is known about lucythan is generally supposed. it isn’t even actually known that she was a female. her sex ismerely presumed from her diminutive size. two years after lucy’s discovery, at laetoli in tanzania mary leakey found footprints leftby two individuals from it is thought the same family of hominids. the prints had beenmade when two australopithecines had walked through muddy ash following a volcaniceruption. the ash had later hardened, preserving the impressions of their feet for a distance ofover twenty three meters. the american museum of natural history in new york has an absorbing diorama thatrecords the moment of their passing. it depicts life sized re creations of a male and a femalewalking side by side across the ancient african plain. they are hairy and chimplike indimensions, but have a bearing and gait that suggest humanness. the most striking feature ofthe display is that the male holds his left arm protectively around the female’s shoulder. it is atender and affecting gesture, suggestive of close bonding. the tableau is done with such conviction that it is easy to overlook the consideration thatvirtually everything above the footprints is imaginary. almost every external aspect of thetwo figures degree of hairiness, facial appendages (whether they had human noses or chimpnoses), expressions, skin color, size and shape of the female’s breasts is necessarilysuppositional. we can’t even say that they were a couple. the female figure may in fact havebeen a child. nor can we be certain that they were australopithecines. they are assumed to beaustralopithecines because there are no other known candidates. i had been told that they were posed like that because during the building of the dioramathe female figure kept toppling over, but ian tattersall insists with a laugh that the story isuntrue. “obviously we don’t know whether the male had his arm around the female or not,but we do know from the stride measurements that they were walking side by side and closetogether close enough to be touching. it was quite an exposed area, so they were probablyfeeling vulnerable. that’s why we tried to give them slightly worried expressions.” i asked him if he was troubled about the amount of license that was taken in reconstructingthe figures. “it’s always a problem in making re creations,” he agreed readily enough. “youwouldn’t believe how much discussion can go into deciding details like whether neandertalshad eyebrows or not. it was just the same for the laetoli figures. we simply can’t know thedetails of what they looked like, but we can convey their size and posture and make somereasonable assumptions about their probable appearance. if i had it to do again, i think i might have made them just slightly more apelike and less human. these creatures weren’t humans.they were bipedal apes.” until very recently it was assumed that we were descended from lucy and the laetolicreatures, but now many authorities aren’t so sure. although certain physical features (theteeth, for instance) suggest a possible link between us, other parts of the australopithecineanatomy are more troubling. in their book extinct humans, tattersall and schwartz point outthat the upper portion of the human femur is very like that of the apes but not of theaustralopithecines; so if lucy is in a direct line between apes and modern humans, it meanswe must have adopted an australopithecine femur for a million years or so, then gone back toan ape femur when we moved on to the next phase of our development. they believe, in fact,that not only was lucy not our ancestor, she wasn’t even much of a walker. “lucy and her kind did not locomote in anything like the modern human fashion,” insiststattersall. “only when these hominids had to travel between arboreal habitats would they findthemselves walking bipedally, ‘forced’ to do so by their own anatomies.” johanson doesn’taccept this. “lucy’s hips and the muscular arrangement of her pelvis,” he has written, “wouldhave made it as hard for her to climb trees as it is for modern humans.” matters grew murkier still in 2001 and 2002 when four exceptional new specimens werefound. one, discovered by meave leakey of the famous fossil hunting family at laketurkana in kenya and called kenyanthropus platyops (“kenyan flat face”), is from about thesame time as lucy and raises the possibility that it was our ancestor and lucy was anunsuccessful side branch. also found in 2001 were ardipithecus ramidus kadabba, dated atbetween 5.2 million and 5.8 million years old, and orrorin tugenensis, thought to be 6 millionyears old, making it the oldest hominid yet found but only for a brief while. in the summerof 2002 a french team working in the djurab desert of chad (an area that had never beforeyielded ancient bones) found a hominid almost 7 million years old, which they labeledsahelanthropus tchadensis. (some critics believe that it was not human, but an early ape andtherefore should be called sahelpithecus.) all these were early creatures and quite primitivebut they walked upright, and they were doing so far earlier than previously thought. bipedalism is a demanding and risky strategy. it means refashioning the pelvis into a fullload bearing instrument. to preserve the required strength, the birth canal must becomparatively narrow. this has two very significant immediate consequences and one longer term one. first, it means a lot of pain for any birthing mother and a greatly increased dangerof fatality to mother and baby both. moreover to get the baby’s head through such a tightspace it must be born while its brain is still small and while the baby, therefore, is stillhelpless. this means long term infant care, which in turn implies solid male female bonding. all this is problematic enough when you are the intellectual master of the planet, but whenyou are a small, vulnerable australopithecine, with a brain about the size of an orange,3 therisk must have been enormous.3 absolute brain size does not tell you everything or possibly sometimes even much. elephants and whales bothhave brains larger than ours, but you wouldn't have much trouble outwitting them in contract negotiations. it isrelative size that matters, a point that is often overlooked. as gould notes, a. africanus had a brain of only 450cubic centimeters, smaller than that of a gorilla. but a typical africanus male weighed less than a hundredpounds, and a female much less still, whereas gorillas can easily top out at 600 pounds (gould pp. 181 83). so why did lucy and her kind come down from the trees and out of the forests? probablythey had no choice. the slow rise of the isthmus of panama had cut the flow of waters fromthe pacific into the atlantic, diverting warming currents away from the arctic and leading tothe onset of an exceedingly sharp ice age in northern latitudes. in africa, this would haveproduced seasonal drying and cooling, gradually turning jungle into savanna. “it was not somuch that lucy and her like left the forests,” john gribbin has written, “but that the forestsleft them.” but stepping out onto the open savanna also clearly left the early hominids much moreexposed. an upright hominid could see better, but could also be seen better. even now as aspecies, we are almost preposterously vulnerable in the wild. nearly every large animal youcan care to name is stronger, faster, and toothier than us. faced with attack, modern humanshave only two advantages. we have a good brain, with which we can devise strategies, andwe have hands with which we can fling or brandish hurtful objects. we are the only creaturethat can harm at a distance. we can thus afford to be physically vulnerable. all the elements would appear to have been in place for the rapid evolution of a potentbrain, and yet that seems not to have happened. for over three million years, lucy and herfellow australopithecines scarcely changed at all. their brain didn’t grow and there is no signthat they used even the simplest tools. what is stranger still is that we now know that forabout a million years they lived alongside other early hominids who did use tools, yet theaustralopithecines never took advantage of this useful technology that was all around them. at one point between three and two million years ago, it appears there may have been asmany as six hominid types coexisting in africa. only one, however, was fated to last: homo,which emerged from the mists beginning about two million years ago. no one knows quitewhat the relationship was between australopithecines and homo, but what is known is thatthey coexisted for something over a million years before all the australopithecines, robust andgracile alike, vanished mysteriously, and possibly abruptly, over a million years ago. no oneknows why they disappeared. “perhaps,” suggests matt ridley, “we ate them.” conventionally, the homo line begins with homo habilis, a creature about whom we knowalmost nothing, and concludes with us, homo sapiens (literally “man the thinker”). inbetween, and depending on which opinions you value, there have been half a dozen otherhomo species: homo ergaster, homo neanderthalensis, homo rudolfensis, homoheidelbergensis, homo erectus, and homo antecessor. homo habilis (“handy man”) was named by louis leakey and colleagues in 1964 and wasso called because it was the first hominid to use tools, albeit very simple ones. it was a fairlyprimitive creature, much more chimpanzee than human, but its brain was about 50 percentlarger than that of lucy in gross terms and not much less large proportionally, so it was theeinstein of its day. no persuasive reason has ever been adduced for why hominid brainssuddenly began to grow two million years ago. for a long time it was assumed that big brainsand upright walking were directly related that the movement out of the forests necessitatedcunning new strategies that fed off of or promoted braininess so it was something of asurprise, after the repeated discoveries of so many bipedal dullards, to realize that there wasno apparent connection between them at all. “there is simply no compelling reason we know of to explain why human brains gotlarge,” says tattersall. huge brains are demanding organs: they make up only 2 percent of thebody’s mass, but devour 20 percent of its energy. they are also comparatively picky in what they use as fuel. if you never ate another morsel of fat, your brain would not complainbecause it won’t touch the stuff. it wants glucose instead, and lots of it, even if it means short changing other organs. as guy brown notes: “the body is in constant danger of beingdepleted by a greedy brain, but cannot afford to let the brain go hungry as that would rapidlylead to death.” a big brain needs more food and more food means increased risk. tattersall thinks the rise of a big brain may simply have been an evolutionary accident. hebelieves with stephen jay gould that if you replayed the tape of life even if you ran it backonly a relatively short way to the dawn of hominids the chances are “quite unlikely” thatmodern humans or anything like them would be here now. “one of the hardest ideas for humans to accept,” he says, “is that we are not theculmination of anything. there is nothing inevitable about our being here. it is part of ourvanity as humans that we tend to think of evolution as a process that, in effect, wasprogrammed to produce us. even anthropologists tended to think this way right up until the1970s.” indeed, as recently as 1991, in the popular textbook the stages of evolution, c.loring brace stuck doggedly to the linear concept, acknowledging just one evolutionary deadend, the robust australopithecines. everything else represented a straightforwardprogression each species of hominid carrying the baton of development so far, then handingit on to a younger, fresher runner. now, however, it seems certain that many of these earlyforms followed side trails that didn’t come to anything. luckily for us, one did a group of tool users, which seemed to arise from out of nowhereand overlapped with the shadowy and much disputed homo habilis. this is homo erectus, thespecies discovered by eugène dubois in java in 1891. depending on which sources youconsult, it existed from about 1.8 million years ago to possibly as recently as twenty thousandor so years ago. according to the java man authors, homo erectus is the dividing line: everything thatcame before him was apelike in character; everything that came after was humanlike. homoerectus was the first to hunt, the first to use fire, the first to fashion complex tools, the first toleave evidence of campsites, the first to look after the weak and frail. compared with all thathad gone before, homo erectus was extremely human in form as well as behavior, itsmembers long limbed and lean, very strong (much stronger than modern humans), and withthe drive and intelligence to spread successfully over huge areas. to other hominids, homoerectus must have seemed terrifyingly powerful, fleet, and gifted. erectus was “the velociraptor of its day,” according to alan walker of penn stateuniversity and one of the world’s leading authorities. if you were to look one in the eyes, itmight appear superficially to be human, but “you wouldn’t connect. you’d be prey.”according to walker, it had the body of an adult human but the brain of a baby. although erectus had been known about for almost a century it was known only fromscattered fragments not enough to come even close to making one full skeleton. so it wasn’tuntil an extraordinary discovery in africa in the 1980s that its importance or, at the veryleast, possible importance as a precursor species for modern humans was fully appreciated.the remote valley of lake turkana (formerly lake rudolf) in kenya is now one of theworld’s most productive sites for early human remains, but for a very long time no one hadthought to look there. it was only because richard leakey was on a flight that was divertedover the valley that he realized it might be more promising than had been thought. a teamwas dispatched to investigate, but at first found nothing. then late one afternoon kamoya kimeu, leakey’s most renowned fossil hunter, found a small piece of hominid brow on a hillwell away from the lake. such a site was unlikely to yield much, but they dug anyway out ofrespect for kimeu’s instincts and to their astonishment found a nearly complete homo erectusskeleton. it was from a boy aged between about nine and twelve who had died 1.54 millionyears ago. the skeleton had “an entirely modern body structure,” says tattersall, in a way thatwas without precedent. the turkana boy was “very emphatically one of us.” also found at lake turkana by kimeu was knm er 1808, a female 1.7 million years old,which gave scientists their first clue that homo erectus was more interesting and complexthan previously thought. the woman’s bones were deformed and covered in coarse growths,the result of an agonizing condition called hypervitaminosis a, which can come only fromeating the liver of a carnivore. this told us first of all that homo erectus was eating meat.even more surprising was that the amount of growth showed that she had lived weeks or evenmonths with the disease. someone had looked after her. it was the first sign of tenderness inhominid evolution. it was also discovered that homo erectus skulls contained (or, in the view of some, possiblycontained) a broca’s area, a region of the frontal lobe of the brain associated with speech.chimps don’t have such a feature. alan walker thinks the spinal canal didn’t have the sizeand complexity to enable speech, that they probably would have communicated about as wellas modern chimps. others, notably richard leakey, are convinced they could speak. for a time, it appears, homo erectus was the only hominid species on earth. it was hugelyadventurous and spread across the globe with what seems to have been breathtaking rapidity.the fossil evidence, if taken literally, suggests that some members of the species reached javaat about the same time as, or even slightly before, they left africa. this has led some hopefulscientists to suggest that perhaps modern people arose not in africa at all, but in asia whichwould be remarkable, not to say miraculous, as no possible precursor species have ever beenfound anywhere outside africa. the asian hominids would have had to appear, as it were,spontaneously. and anyway an asian beginning would merely reverse the problem of theirspread; you would still have to explain how the java people then got to africa so quickly. there are several more plausible alternative explanations for how homo erectus managedto turn up in asia so soon after its first appearance in africa. first, a lot of plus or minusinggoes into the dating of early human remains. if the actual age of the african bones is at thehigher end of the range of estimates or the javan ones at the lower end, or both, then there isplenty of time for african erects to find their way to asia. it is also entirely possible that oldererectus bones await discovery in africa. in addition, the javan dates could be wrongaltogether. now for the doubts. some authorities don’t believe that the turkana finds are homoerectus at all. the snag, ironically, was that although the turkana skeletons were admirablyextensive, all othererectus fossils are inconclusively fragmentary. as tattersall and jeffreyschwartz note in extinct humans, most of the turkana skeleton “couldn’t be compared withanything else closely related to it because the comparable parts weren’t known!” the turkanaskeletons, they say, look nothing like any asian homo erectus and would never have beenconsidered the same species except that they were contemporaries. some authorities insist oncalling the turkana specimens (and any others from the same period) homo ergaster.tattersall and schwartz don’t believe that goes nearly far enough. they believe it wasergaster“or a reasonably close relative” that spread to asia from africa, evolved intohomo erectus,and then died out. what is certain is that sometime well over a million years ago, some new, comparativelymodern, upright beings left africa and boldly spread out across much of the globe. theypossibly did so quite rapidly, increasing their range by as much as twenty five miles a year onaverage, all while dealing with mountain ranges, rivers, deserts, and other impediments andadapting to differences in climate and food sources. a particular mystery is how they passedalong the west side of the red sea, an area of famously punishing aridity now, but even drierin the past. it is a curious irony that the conditions that prompted them to leave africa wouldhave made it much more difficult to do so. yet somehow they managed to find their wayaround every barrier and to thrive in the lands beyond. and that, i’m afraid, is where all agreement ends. what happened next in the history ofhuman development is a matter of long and rancorous debate, as we shall see in the nextchapter. but it is worth remembering, before we move on, that all of these evolutionary jostlingsover five million years, from distant, puzzled australopithecine to fully modern human,produced a creature that is still 98.4 percent genetically indistinguishable from the modernchimpanzee. there is more difference between a zebra and a horse, or between a dolphin anda porpoise, than there is between you and the furry creatures your distant ancestors left behindwhen they set out to take over the world. 29 the restless apesometime about a million and a half years ago, some forgotten genius of the hominidworld did an unexpected thing. he (or very possibly she) took one stone and carefully used itto shape another. the result was a simple teardrop shaped hand axe, but it was the world’sfirst piece of advanced technology. it was so superior to existing tools that soon others were following the inventor’s lead andmaking hand axes of their own. eventually whole societies existed that seemed to do littleelse. “they made them in the thousands,” says ian tattersall. “there are some places inafrica where you literally can’t move without stepping on them. it’s strange because they arequite intensive objects to make. it was as if they made them for the sheer pleasure of it.” from a shelf in his sunny workroom tattersall took down an enormous cast, perhaps a footand a half long and eight inches wide at its widest point, and handed it to me. it was shapedlike a spearhead, but one the size of a stepping stone. as a fiberglass cast it weighed only afew ounces, but the original, which was found in tanzania, weighed twenty five pounds. “itwas completely useless as a tool,” tattersall said. “it would have taken two people to lift itadequately, and even then it would have been exhausting to try to pound anything with it.” “what was it used for then?” tattersall gave a genial shrug, pleased at the mystery of it. “no idea. it must have had somesymbolic importance, but we can only guess what.” the axes became known as acheulean tools, after st. acheul, a suburb of amiens innorthern france, where the first examples were found in the nineteenth century, and contrastwith the older, simpler tools known as oldowan, originally found at olduvai gorge intanzania. in older textbooks, oldowan tools are usually shown as blunt, rounded, hand sizedstones. in fact, paleoanthropologists now tend to believe that the tool part of oldowan rockswere the pieces flaked off these larger stones, which could then be used for cutting. now here’s the mystery. when early modern humans the ones who would eventuallybecome us started to move out of africa something over a hundred thousand years ago,acheulean tools were the technology of choice. these early homo sapiens loved theiracheulean tools, too. they carried them vast distances. sometimes they even took unshapedrocks with them to make into tools later on. they were, in a word, devoted to the technology.but although acheulean tools have been found throughout africa, europe, and western andcentral asia, they have almost never been found in the far east. this is deeply puzzling. in the 1940s a harvard paleontologist named hallum movius drew something called themovius line, dividing the side with acheulean tools from the one without. the line runs in asoutheasterly direction across europe and the middle east to the vicinity of modern daycalcutta and bangladesh. beyond the movius line, across the whole of southeast asia andinto china, only the older, simpler oldowan tools have been found. we know that homosapiens went far beyond this point, so why would they carry an advanced and treasured stonetechnology to the edge of the far east and then just abandon it? “that troubled me for a long time,” recalls alan thorne of the australian nationaluniversity in canberra. “the whole of modern anthropology was built round the idea thathumans came out of africa in two waves a first wave of homo erectus, which became javaman and peking man and the like, and a later, more advanced wave of homo sapiens, whichdisplaced the first lot. yet to accept that you must believe thathomo sapiens got so far withtheir more modern technology and then, for whatever reason, gave it up. it was all verypuzzling, to say the least.” as it turned out, there would be a great deal else to be puzzled about, and one of the mostpuzzling findings of all would come from thorne’s own part of the world, in the outback ofaustralia. in 1968, a geologist named jim bowler was poking around on a long dried lakebedcalled mungo in a parched and lonely corner of western new south wales when somethingvery unexpected caught his eye. sticking out of a crescent shaped sand ridge of a type knownas a lunette were some human bones. at the time, it was believed that humans had been inaustralia for no more than 8,000 years, but mungo had been dry for 12,000 years. so whatwas anyone doing in such an inhospitable place? the answer, provided by carbon dating, was that the bones’ owner had lived there whenlake mungo was a much more agreeable habitat, a dozen miles long, full of water and fish,fringed by pleasant groves of casuarina trees. to everyone’s astonishment, the bones turnedout to be 23,000 years old. other bones found nearby were dated to as much as 60,000 years.this was unexpected to the point of seeming practically impossible. at no time sincehominids first arose on earth has australia not been an island. any human beings who arrivedthere must have come by sea, in large enough numbers to start a breeding population, aftercrossing sixty miles or more of open water without having any way of knowing that aconvenient landfall awaited them. having landed, the mungo people had then found their waymore than two thousand miles inland from australia’s north coast the presumed point ofentry which suggests, according to a report in the proceedings of the national academy ofsciences, “that people may have first arrived substantially earlier than 60,000 years ago.” how they got there and why they came are questions that can’t be answered. according tomost anthropology texts, there’s no evidence that people could even speak 60,000 years ago,much less engage in the sorts of cooperative efforts necessary to build ocean worthy craft andcolonize island continents. “there’s just a whole lot we don’t know about the movements of people before recordedhistory,” alan thorne told me when i met him in canberra. “do you know that whennineteenth century anthropologists first got to papua new guinea, they found people in thehighlands of the interior, in some of the most inaccessible terrain on earth, growing sweetpotatoes. sweet potatoes are native to south america. so how did they get to papua newguinea? we don’t know. don’t have the faintest idea. but what is certain is that people havebeen moving around with considerable assuredness for longer than traditionally thought, andalmost certainly sharing genes as well as information.” the problem, as ever, is the fossil record. “very few parts of the world are even vaguelyamenable to the long term preservation of human remains,” says thorne, a sharp eyed manwith a white goatee and an intent but friendly manner. “if it weren’t for a few productiveareas like hadar and olduvai in east africa we’d know frighteningly little. and when youlook elsewhere, often wedo know frighteningly little. the whole of india has yielded just oneancient human fossil, from about 300,000 years ago. between iraq and vietnam that’s adistance of some 5,000 kilometers there have been just two: the one in india and aneandertal in uzbekistan.” he grinned. “that’s not a whole hell of a lot to work with. you’releft with the position that you’ve got a few productive areas for human fossils, like the greatrift valley in africa and mungo here in australia, and very little in between. it’s notsurprising that paleontologists have trouble connecting the dots.” the traditional theory to explain human movements and the one still accepted by themajority of people in the field is that humans dispersed across eurasia in two waves. thefirst wave consisted of homo erectus, who left africa remarkably quickly almost as soon asthey emerged as a species beginning nearly two million years ago. over time, as they settledin different regions, these early erects further evolved into distinctive types into java manand peking man in asia, and homo heidelbergensis and finally homo neanderthalensis ineurope. then, something over a hundred thousand years ago, a smarter, lither species of creature the ancestors of every one of us alive today arose on the african plains and began radiatingoutward in a second wave. wherever they went, according to this theory, these new homosapiens displaced their duller, less adept predecessors. quite how they did this has alwaysbeen a matter of disputation. no signs of slaughter have ever been found, so most authoritiesbelieve the newer hominids simply outcompeted the older ones, though other factors may alsohave contributed. “perhaps we gave them smallpox,” suggests tattersall. “there’s no real wayof telling. the one certainty is that we are here now and they aren’t.” these first modern humans are surprisingly shadowy. we know less about ourselves,curiously enough, than about almost any other line of hominids. it is odd indeed, as tattersallnotes, “that the most recent major event in human evolution the emergence of our ownspecies is perhaps the most obscure of all.” nobody can even quite agree where trulymodern humans first appear in the fossil record. many books place their debut at about120,000 years ago in the form of remains found at the klasies river mouth in south africa,but not everyone accepts that these were fully modern people. tattersall and schwartzmaintain that “whether any or all of them actually represent our species still awaits definitiveclarification.” the first undisputed appearance of homo sapiens is in the eastern mediterranean, aroundmodern day israel, where they begin to show up about 100,000 years ago but even therethey are described (by trinkaus and shipman) as “odd, difficult to classify and poorlyknown.” neandertals were already well established in the region and had a type of tool kitknown as mousterian, which the modern humans evidently found worthy enough to borrow.no neandertal remains have ever been found in north africa, but their tool kits turn up allover the place. somebody must have taken them there: modern humans are the onlycandidate. it is also known that neandertals and modern humans coexisted in some fashionfor tens of thousands of years in the middle east. “we don’t know if they time shared thesame space or actually lived side by side,” tattersall says, but the moderns continued happilyto use neandertal tools hardly convincing evidence of overwhelming superiority. no lesscuriously, acheulean tools are found in the middle east well over a million years ago, but scarcely exist in europe until just 300,000 years ago. again, why people who had thetechnology didn’t take the tools with them is a mystery. for a long time, it was believed that the cro magnons, as modern humans in europebecame known, drove the neandertals before them as they advanced across the continent,eventually forcing them to its western margins, where essentially they had no choice but tofall in the sea or go extinct. in fact, it is now known that cro magnons were in the far west ofeurope at about the same time they were also coming in from the east. “europe was a prettyempty place in those days,” tattersall says. “they may not have encountered each other allthat often, even with all their comings and goings.” one curiosity of the cro magnons’ arrivalis that it came at a time known to paleoclimatology as the boutellier interval, when europewas plunging from a period of relative mildness into yet another long spell of punishing cold.whatever it was that drew them to europe, it wasn’t the glorious weather. in any case, the idea that neandertals crumpled in the face of competition from newlyarrived cro magnons strains against the evidence at least a little. neandertals were nothing ifnot tough. for tens of thousands of years they lived through conditions that no modern humanoutside a few polar scientists and explorers has experienced. during the worst of the ice ages,blizzards with hurricane force winds were common. temperatures routinely fell to 50 degreesbelow zero fahrenheit. polar bears padded across the snowy vales of southern england.neandertals naturally retreated from the worst of it, but even so they will have experiencedweather that was at least as bad as a modern siberian winter. they suffered, to be sure aneandertal who lived much past thirty was lucky indeed but as a species they weremagnificently resilient and practically indestructible. they survived for at least a hundredthousand years, and perhaps twice that, over an area stretching from gibraltar to uzbekistan,which is a pretty successful run for any species of being. quite who they were and what they were like remain matters of disagreement anduncertainty. right up until the middle of the twentieth century the accepted anthropologicalview of the neandertal was that he was dim, stooped, shuffling, and simian thequintessential caveman. it was only a painful accident that prodded scientists to reconsiderthis view. in 1947, while doing fieldwork in the sahara, a franco algerian paleontologistnamed camille arambourg took refuge from the midday sun under the wing of his lightairplane. as he sat there, a tire burst from the heat, and the plane tipped suddenly, striking hima painful blow on the upper body. later in paris he went for an x ray of his neck, and noticedthat his own vertebrae were aligned exactly like those of the stooped and hulking neandertal.either he was physiologically primitive or neandertal’s posture had been misdescribed. infact, it was the latter. neandertal vertebrae were not simian at all. it changed utterly how weviewed neandertals but only some of the time, it appears. it is still commonly held that neandertals lacked the intelligence or fiber to compete onequal terms with the continent’s slender and more cerebrally nimble newcomers, homosapiens. here is a typical comment from a recent book: “modern humans neutralized thisadvantage [the neandertal’s considerably heartier physique] with better clothing, better firesand better shelter; meanwhile the neandertals were stuck with an oversize body that requiredmore food to sustain.” in other words, the very factors that had allowed them to survivesuccessfully for a hundred thousand years suddenly became an insuperable handicap. above all the issue that is almost never addressed is that neandertals had brains that weresignificantly larger than those of modern people 1.8 liters for neandertals versus 1.4 formodern people, according to one calculation. this is more than the difference between modern homo sapiens and late homo erectus , a species we are happy to regard as barelyhuman. the argument put forward is that although our brains were smaller, they weresomehow more efficient. i believe i speak the truth when i observe that nowhere else inhuman evolution is such an argument made. so why then, you may well ask, if the neandertals were so stout and adaptable andcerebrally well endowed, are they no longer with us? one possible (but much disputed)answer is that perhaps they are. alan thorne is one of the leading proponents of an alternativetheory, known as the multiregional hypothesis, which holds that human evolution has beencontinuous that just as australopithecines evolved into homo habilis and homoheidelbergensis became over time homo neanderthalensis, so modernhomo sapiens simplyemerged from more ancient homo forms.homo erectus is, on this view, not a separate speciesbut just a transitional phase. thus modern chinese are descended from ancient homo erectusforebears in china, modern europeans from ancient european homo erectus, and so on.“except that for me there are no homo erectus,” says thorne. “i think it’s a term which hasoutlived its usefulness. for me, homo erectus is simply an earlier part of us. i believe onlyone species of humans has ever left africa, and that species ishomo sapiens.” opponents of the multiregional theory reject it, in the first instance, on the grounds that itrequires an improbable amount of parallel evolution by hominids throughout the old world in africa, china, europe, the most distant islands of indonesia, wherever they appeared. somealso believe that multiregionalism encourages a racist view that anthropology took a very longtime to rid itself of. in the early 1960s, a famous anthropologist named carleton coon of theuniversity of pennsylvania suggested that some modern races have different sources oforigin, implying that some of us come from more superior stock than others. this hearkenedback uncomfortably to earlier beliefs that some modern races such as the african “bushmen”(properly the kalahari san) and australian aborigines were more primitive than others. whatever coon may personally have felt, the implication for many people was that someraces are inherently more advanced, and that some humans could essentially constitutedifferent species. the view, so instinctively offensive now, was widely popularized in manyrespectable places until fairly recent times. i have before me a popular book published bytime life publications in 1961 called the epic of man based on a series of articles in lifemagazine. in it you can find such comments as “rhodesian man . . . lived as recently as25,000 years ago and may have been an ancestor of the african negroes. his brain size wasclose to that of homo sapiens.” in other words black africans were recently descended fromcreatures that were only “close” to homo sapiens. thorne emphatically (and i believe sincerely) dismisses the idea that his theory is in anymeasure racist and accounts for the uniformity of human evolution by suggesting that therewas a lot of movement back and forth between cultures and regions. “there’s no reason tosuppose that people only went in one direction,” he says. “people were moving all over theplace, and where they met they almost certainly shared genetic material throughinterbreeding. new arrivals didn’t replace the indigenous populations, they joined them. theybecame them.” he likens the situation to when explorers like cook or magellan encounteredremote peoples for the first time. “they weren’t meetings of different species, but of the samespecies with some physical differences.” what you actually see in the fossil record, thorne insists, is a smooth, continuoustransition. “there’s a famous skull from petralona in greece, dating from about 300,000 yearsago, that has been a matter of contention among traditionalists because it seems in some ways homo erectus but in other ways homo sapiens. well, what we say is that this is just what youwould expect to find in species that were evolving rather than being displaced.” one thing that would help to resolve matters would be evidence of interbreeding, but that isnot at all easy to prove, or disprove, from fossils. in 1999, archeologists in portugal found theskeleton of a child about four years old that died 24,500 years ago. the skeleton was modernoverall, but with certain archaic, possibly neandertal, characteristics: unusually sturdy legbones, teeth bearing a distinctive “shoveling” pattern, and (though not everyone agrees on it)an indentation at the back of the skull called a suprainiac fossa, a feature exclusive toneandertals. erik trinkaus of washington university in st. louis, the leading authority onneandertals, announced the child to be a hybrid: proof that modern humans and neandertalsinterbred. others, however, were troubled that the neandertal and modern features weren’tmore blended. as one critic put it: “if you look at a mule, you don’t have the front endlooking like a donkey and the back end looking like a horse.” ian tattersall declared it to be nothing more than “a chunky modern child.” he accepts thatthere may well have been some “hanky panky” between neandertals and moderns, butdoesn’t believe it could have resulted in reproductively successful offspring.1 “i don’t knowof any two organisms from any realm of biology that are that different and still in the samespecies,” he says. with the fossil record so unhelpful, scientists have turned increasingly to genetic studies,in particular the part known as mitochondrial dna. mitochondrial dna was only discoveredin 1964, but by the 1980s some ingenious souls at the university of california at berkeley hadrealized that it has two features that lend it a particular convenience as a kind of molecularclock: it is passed on only through the female line, so it doesn’t become scrambled withpaternal dna with each new generation, and it mutates about twenty times faster than normalnuclear dna, making it easier to detect and follow genetic patterns over time. by tracking therates of mutation they could work out the genetic history and relationships of whole groups ofpeople. in 1987, the berkeley team, led by the late allan wilson, did an analysis of mitochondrialdna from 147 individuals and declared that the rise of anatomically modern humansoccurred in africa within the last 140,000 years and that “all present day humans aredescended from that population.” it was a serious blow to the multiregionalists. but thenpeople began to look a little more closely at the data. one of the most extraordinary points almost too extraordinary to credit really was that the “africans” used in the study wereactually african americans, whose genes had obviously been subjected to considerablemediation in the past few hundred years. doubts also soon emerged about the assumed ratesof mutations. by 1992, the study was largely discredited. but the techniques of genetic analysiscontinued to be refined, and in 1997 scientists from the university of munich managed toextract and analyze some dna from the arm bone of the original neandertal man, and thistime the evidence stood up. the munich study found that the neandertal dna was unlike anydna found on earth now, strongly indicating that there was no genetic connection betweenneandertals and modern humans. now this really was a blow to multiregionalism.1 one possibility is that neandertals and cro magnons had different numbers of chromosomes, a complicationthat commonly arises when species that are close but not quite identical conjoin. in the equine world, forexample, horses have 64 chromosomes and donkeys 62. mate the two and you get an offspring with areproductively useless number of chromosomes, 63. you have, in short, a sterile mule. then in late 2000 nature and other publications reported on a swedish study of themitochondrial dna of fifty three people, which suggested that all modern humans emergedfrom africa within the past 100,000 years and came from a breeding stock of no more than10,000 individuals. soon afterward, eric lander, director of the whiteheadinstitute/massachusetts institute of technology center for genome research, announced thatmodern europeans, and perhaps people farther afield, are descended from “no more than afew hundred africans who left their homeland as recently as 25,000 years ago.” as we have noted elsewhere in the book, modern human beings show remarkably littlegenetic variability “there’s more diversity in one social group of fifty five chimps than inthe entire human population,” as one authority has put it and this would explain why.because we are recently descended from a small founding population, there hasn’t been timeenough or people enough to provide a source of great variability. it seemed a pretty severeblow to multiregionalism. “after this,” a penn state academic told the washington post,“people won’t be too concerned about the multiregional theory, which has very littleevidence.” but all of this overlooked the more or less infinite capacity for surprise offered by theancient mungo people of western new south wales. in early 2001, thorne and his colleaguesat the australian national university reported that they had recovered dna from the oldest ofthe mungo specimens now dated at 62,000 years and that this dna proved to be“genetically distinct.” the mungo man, according to these findings, was anatomically modern just like you andme but carried an extinct genetic lineage. his mitochondrial dna is no longer found inliving humans, as it should be if, like all other modern people, he was descended from peoplewho left africa in the recent past. “it turned everything upside down again,” says thorne with undisguised delight. then other even more curious anomalies began to turn up. rosalind harding, a populationgeneticist at the institute of biological anthropology in oxford, while studying betaglobingenes in modern people, found two variants that are common among asians and theindigenous people of australia, but hardly exist in africa. the variant genes, she is certain,arose more than 200,000 years ago not in africa, but in east asia long before modern homosapiens reached the region. the only way to account for them is to say that ancestors ofpeople now living in asia included archaic hominids java man and the like. interestingly,this same variant gene the java man gene, so to speak turns up in modern populations inoxfordshire. confused, i went to see harding at the institute, which inhabits an old brick villa onbanbury road in oxford, in more or less the neighborhood where bill clinton spent hisstudent days. harding is a small and chirpy australian, from brisbane originally, with the rareknack for being amused and earnest at the same time. “don’t know,” she said at once, grinning, when i asked her how people in oxfordshireharbored sequences of betaglobin that shouldn’t be there. “on the whole,” she went on moresomberly, “the genetic record supports the out of africa hypothesis. but then you find theseanomalous clusters, which most geneticists prefer not to talk about. there’s huge amounts ofinformation that would be available to us if only we could understand it, but we don’t yet.we’ve barely begun.” she refused to be drawn out on what the existence of asian origin genes in oxfordshire tells us other than that the situation is clearly complicated. “all we cansay at this stage is that it is very untidy and we don’t really know why.” at the time of our meeting, in early 2002, another oxford scientist named bryan sykes hadjust produced a popular book called the seven daughters of eve in which, using studies ofmitochondrial dna, he had claimed to be able to trace nearly all living europeans back to afounding population of just seven women the daughters of eve of the title who livedbetween 10,000 and 45,000 years ago in the time known to science as the paleolithic. to eachof these women sykes had given a name ursula, xenia, jasmine, and so on and even adetailed personal history. (“ursula was her mother’s second child. the first had been taken bya leopard when he was only two. . . .”) when i asked harding about the book, she smiled broadly but carefully, as if not quitecertain where to go with her answer. “well, i suppose you must give him some credit forhelping to popularize a difficult subject,” she said and paused thoughtfully. “and thereremains the remote possibility that he’s right.” she laughed, then went on more intently:“data from any single gene cannot really tell you anything so definitive. if you follow themitochondrial dna backwards, it will take you to a certain place to an ursula or tara orwhatever. but if you take any other bit of dna, any gene at all, and traceit back, it will takeyou someplace else altogether.” it was a little, i gathered, like following a road randomly out of london and finding thateventually it ends at john o’groats, and concluding from this that anyone in london musttherefore have come from the north of scotland. they might have come from there, of course,but equally they could have arrived from any of hundreds of other places. in this sense,according to harding, every gene is a different highway, and we have only barely begun tomap the routes. “no single gene is ever going to tell you the whole story,” she said. so genetic studies aren’t to be trusted? “oh you can trust the studies well enough, generally speaking. what you can’t trust are thesweeping conclusions that people often attach to them.” she thinks out of africa is “probably 95 percent correct,” but adds: “i think both sides havedone a bit of a disservice to science by insisting that it must be one thing or the other. thingsare likely to turn out to be not so straightforward as either camp would have you believe. theevidence is clearly starting to suggest that there were multiple migrations and dispersals indifferent parts of the world going in all kinds of directions and generally mixing up the genepool. that’s never going to be easy to sort out.” just at this time, there were also a number of reports questioning the reliability of claimsconcerning the recovery of very ancient dna. an academic writing in nature had noted howa paleontologist, asked by a colleague whether he thought an old skull was varnished or not,had licked its top and announced that it was. “in the process,” noted the nature article, “largeamounts of modern human dna would have been transferred to the skull,” rendering ituseless for future study. i asked harding about this. “oh, it would almost certainly have beencontaminated already,” she said. “just handling a bone will contaminate it. breathing on itwill contaminate it. most of the water in our labs will contaminate it. we are all swimming inforeign dna. in order to get a reliably clean specimen you have to excavate it in sterileconditions and do the tests on it at the site. it is the trickiest thing in the world not tocontaminate a specimen.” so should such claims be treated dubiously? i asked. harding nodded solemnly. “very,” she said. if you wish to understand at once why we know as little as we do about human origins, ihave the place for you. it is to be found a little beyond the edge of the blue ngong hills inkenya, to the south and west of nairobi. drive out of the city on the main highway touganda, and there comes a moment of startling glory when the ground falls away and you arepresented with a hang glider’s view of boundless, pale green african plain. this is the great rift valley, which arcs across three thousand miles of east africa,marking the tectonic rupture that is setting africa adrift from asia. here, perhaps forty milesout of nairobi, along the baking valley floor, is an ancient site called olorgesailie, which oncestood beside a large and pleasant lake. in 1919, long after the lake had vanished, a geologistnamed j. w. gregory was scouting the area for mineral prospects when he came across astretch of open ground littered with anomalous dark stones that had clearly been shaped byhuman hand. he had found one of the great sites of acheulean tool manufacture that iantattersall had told me about. unexpectedly in the autumn of 2002 i found myself a visitor to this extraordinary site. iwas in kenya for another purpose altogether, visiting some projects run by the charity careinternational, but my hosts, knowing of my interest in humans for the present volume, hadinserted a visit to olorgesailie into the schedule. after its discovery by gregory, olorgesailie lay undisturbed for over two decades beforethe famed husband and wife team of louis and mary leakey began an excavation that isn’tcompleted yet. what the leakeys found was a site stretching to ten acres or so, where toolswere made in incalculable numbers for roughly a million years, from about 1.2 million yearsago to 200,000 years ago. today the tool beds are sheltered from the worst of the elementsbeneath large tin lean tos and fenced off with chicken wire to discourage opportunisticscavenging by visitors, but otherwise the tools are left just where their creators dropped themand where the leakeys found them. jillani ngalli, a keen young man from the kenyan national museum who had beendispatched to act as guide, told me that the quartz and obsidian rocks from which the axeswere made were never found on the valley floor. “they had to carry the stones from there,” hesaid, nodding at a pair of mountains in the hazy middle distance, in opposite directions fromthe site: olorgesailie and ol esakut. each was about ten kilometers, or six miles, away along way to carry an armload of stone. why the early olorgesailie people went to such trouble we can only guess, of course. notonly did they lug hefty stones considerable distances to the lakeside, but, perhaps even moreremarkably, they then organized the site. the leakeys’ excavations revealed that there wereareas where axes were fashioned and others where blunt axes were brought to be resharpened.olorgesailie was, in short, a kind of factory; one that stayed in business for a million years. various replications have shown that the axes were tricky and labor intensive objects tomake even with practice, an axe would take hours to fashion and yet, curiously, they werenot particularly good for cutting or chopping or scraping or any of the other tasks to whichthey were presumably put. so we are left with the position that for a million years far, farlonger than our own species has even been in existence, much less engaged in continuous cooperative efforts early people came in considerable numbers to this particular site to makeextravagantly large numbers of tools that appear to have been rather curiously pointless. and who were these people? we have no idea actually. we assume they were homoerectus because there are no other known candidates, which means that at their peak theirpeak  the olorgesailie workers would have had the brains of a modern infant. but there is nophysical evidence on which to base a conclusion. despite over sixty years of searching, nohuman bone has ever been found in or around the vicinity of olorgesailie. however muchtime they spent there shaping rocks, it appears they went elsewhere to die. “it’s all a mystery,” jillani ngalli told me, beaming happily. the olorgesailie people disappeared from the scene about 200,000 years ago when the lakedried up and the rift valley started to become the hot and challenging place it is today. butby this time their days as a species were already numbered. the world was about to get itsfirst real master race, homo sapiens . things would never be the same again. 30 good byein the early 1680s, at just about the time that edmond halley and his friends christopherwren and robert hooke were settling down in a london coffeehouse and embarking on thecasual wager that would result eventually in isaac newton’s principia , henry cavendish’sweighing of the earth, and many of the other inspired and commendable undertakings thathave occupied us for much of the past four hundred pages, a rather less desirable milestonewas being passed on the island of mauritius, far out in the indian ocean some eight hundredmiles off the east coast of madagascar. there, some forgotten sailor or sailor’s pet was harrying to death the last of the dodos, thefamously flightless bird whose dim but trusting nature and lack of leggy zip made it a ratherirresistible target for bored young tars on shore leave. millions of years of peaceful isolationhad not prepared it for the erratic and deeply unnerving behavior of human beings. we don’t know precisely the circumstances, or even year, attending the last moments of thelast dodo, so we don’t know which arrived first, a world that contained a principia or one thathad no dodos, but we do know that they happened at more or less the same time. you wouldbe hard pressed, i would submit, to find a better pairing of occurrences to illustrate the divineand felonious nature of the human being a species of organism that is capable of unpickingthe deepest secrets of the heavens while at the same time pounding into extinction, for nopurpose at all, a creature that never did us any harm and wasn’t even remotely capable ofunderstanding what we were doing to it as we did it. indeed, dodos were so spectacularlyshort on insight, it is reported, that if you wished to find all the dodos in a vicinity you hadonly to catch one and set it to squawking, and all the others would waddle along to see whatwas up. the indignities to the poor dodo didn’t end quite there. in 1755, some seventy years afterthe last dodo’s death, the director of the ashmolean museum in oxford decided that theinstitution’s stuffed dodo was becoming unpleasantly musty and ordered it tossed on abonfire. this was a surprising decision as it was by this time the only dodo in existence,stuffed or otherwise. a passing employee, aghast, tried to rescue the bird but could save onlyits head and part of one limb. as a result of this and other departures from common sense, we are not now entirely surewhat a living dodo was like. we possess much less information than most people suppose ahandful of crude descriptions by “unscientific voyagers, three or four oil paintings, and a fewscattered osseous fragments,” in the somewhat aggrieved words of the nineteenth centurynaturalist h. e. strickland. as strickland wistfully observed, we have more physical evidenceof some ancient sea monsters and lumbering saurapods than we do of a bird that lived intomodern times and required nothing of us to survive except our absence. so what is known of the dodo is this: it lived on mauritius, was plump but not tasty, andwas the biggest ever member of the pigeon family, though by quite what margin is unknownas its weight was never accurately recorded. extrapolations from strickland’s “osseous fragments” and the ashmolean’s modest remains show that it was a little over two and a halffeet tall and about the same distance from beak tip to backside. being flightless, it nested onthe ground, leaving its eggs and chicks tragically easy prey for pigs, dogs, and monkeysbrought to the island by outsiders. it was probably extinct by 1683 and was most certainlygone by 1693. beyond that we know almost nothing except of course that we will not see itslike again. we know nothing of its reproductive habits and diet, where it ranged, what soundsit made in tranquility or alarm. we don’t possess a single dodo egg. from beginning to end our acquaintance with animate dodos lasted just seventy years. thatis a breathtakingly scanty period though it must be said that by this point in our history wedid have thousands of years of practice behind us in the matter of irreversible eliminations.nobody knows quite how destructive human beings are, but it is a fact that over the last fiftythousand years or so wherever we have gone animals have tended to vanish, in oftenastonishingly large numbers. in america, thirty genera of large animals some very large indeed disappearedpractically at a stroke after the arrival of modern humans on the continent between ten andtwenty thousand years ago. altogether north and south america between them lost aboutthree quarters of their big animals once man the hunter arrived with his flint headed spearsand keen organizational capabilities. europe and asia, where the animals had had longer toevolve a useful wariness of humans, lost between a third and a half of their big creatures.australia, for exactly the opposite reasons, lost no less than 95 percent. because the early hunter populations were comparatively small and the animal populationstruly monumental as many as ten million mammoth carcasses are thought to lie frozen in thetundra of northern siberia alone some authorities think there must be other explanations,possibly involving climate change or some kind of pandemic. as ross macphee of theamerican museum of natural history put it: “there’s no material benefit to huntingdangerous animals more often than you need to there are only so many mammoth steaksyou can eat.” others believe it may have been almost criminally easy to catch and clobberprey. “in australia and the americas,” says tim flannery, “the animals probably didn’t knowenough to run away.” some of the creatures that were lost were singularly spectacular and would take a littlemanaging if they were still around. imagine ground sloths that could look into an upstairswindow, tortoises nearly the size of a small fiat, monitor lizards twenty feet long baskingbeside desert highways in western australia. alas, they are gone and we live on a muchdiminished planet. today, across the whole world, only four types of really hefty (a metric tonor more) land animals survive: elephants, rhinos, hippos, and giraffes. not for tens of millionsof years has life on earth been so diminutive and tame. the question that arises is whether the disappearances of the stone age and disappearancesof more recent times are in effect part of a single extinction event whether, in short, humansare inherently bad news for other living things. the sad likelihood is that we may well be.according to the university of chicago paleontologist david raup, the background rate ofextinction on earth throughout biological history has been one species lost every four yearson average. according to one recent calculation, human caused extinction now may berunning as much as 120,000 times that level. in the mid 1990s, the australian naturalist tim flannery, now head of the south australianmuseum in adelaide, became struck by how little we seemed to know about many extinctions, including relatively recent ones. “wherever you looked, there seemed to be gapsin the records pieces missing, as with the dodo, or not recorded at all,” he told me when imet him in melbourne a year or so ago. flannery recruited his friend peter schouten, an artist and fellow australian, and togetherthey embarked on a slightly obsessive quest to scour the world’s major collections to find outwhat was lost, what was left, and what had never been known at all. they spent four yearspicking through old skins, musty specimens, old drawings, and written descriptions whatever was available. schouten made life sized paintings of every animal they couldreasonably re create, and flannery wrote the words. the result was an extraordinary bookcalled a gap in nature, constituting the most complete and, it must be said, moving catalog of animal extinctions from the last three hundred years. for some animals, records were good, but nobody had done anything much with them,sometimes for years, sometimes forever. steller’s sea cow, a walrus like creature related tothe dugong, was one of the last really big animals to go extinct. it was truly enormous anadult could reach lengths of nearly thirty feet and weigh ten tons but we are acquainted withit only because in 1741 a russian expedition happened to be shipwrecked on the only placewhere the creatures still survived in any numbers, the remote and foggy commander islandsin the bering sea. happily, the expedition had a naturalist, georg steller, who was fascinated by the animal.“he took the most copious notes,” says flannery. “he even measured the diameter of itswhiskers. the only thing he wouldn’t describe was the male genitals though, for somereason, he was happy enough to do the female’s. he even saved a piece of skin, so we had agood idea of its texture. we weren’t always so lucky.” the one thing steller couldn’t do was save the sea cow itself. already hunted to the brinkof extinction, it would be gone altogether within twenty seven years of steller’s discovery ofit. many other animals, however, couldn’t be included because too little is known about them.the darling downs hopping mouse, chatham islands swan, ascension island flightless crake,at least five types of large turtle, and many others are forever lost to us except as names. a great deal of extinction, flannery and schouten discovered, hasn’t been cruel or wanton,but just kind of majestically foolish. in 1894, when a lighthouse was built on a lonely rockcalled stephens island, in the tempestuous strait between the north and south islands of newzealand, the lighthouse keeper’s cat kept bringing him strange little birds that it had caught.the keeper dutifully sent some specimens to the museum in wellington. there a curator grewvery excited because the bird was a relic species of flightless wrens the only example of aflightless perching bird ever found anywhere. he set off at once for the island, but by the timehe got there the cat had killed them all. twelve stuffed museum species of the stephens islandflightless wren are all that now exist. at least we have those. all too often, it turns out, we are not much better at looking afterspecies after they have gone than we were before they went. take the case of the lovelycarolina parakeet. emerald green, with a golden head, it was arguably the most striking andbeautiful bird ever to live in north america parrots don’t usually venture so far north, asyou may have noticed and at its peak it existed in vast numbers, exceeded only by thepassenger pigeon. but the carolina parakeet was also considered a pest by farmers and easilyhunted because it flocked tightly and had a peculiar habit of flying up at the sound of gunfire(as you would expect), but then returning almost at once to check on fallen comrades. in his classic american omithology, written in the early nineteenth century, charleswillson peale describes an occasion in which he repeatedly empties a shotgun into a tree inwhich they roost: at each successive discharge, though showers of them fell, yet the affection of thesurvivors seemed rather to increase; for, after a few circuits around the place, they againalighted near me, looking down on their slaughtered companions with such manifestsymptoms of sympathy and concern, as entirely disarmed me. by the second decade of the twentieth century, the birds had been so relentlessly huntedthat only a few remained alive in captivity. the last one, named inca, died in the cincinnatizoo in 1918 (not quite four years after the last passenger pigeon died in the same zoo) andwas reverently stuffed. and where would you go to see poor inca now? nobody knows. thezoo lost it. what is both most intriguing and puzzling about the story above is that peale was a lover ofbirds, and yet did not hesitate to kill them in large numbers for no better reason than that itinterested him to do so. it is a truly astounding fact that for the longest time the people whowere most intensely interested in the world’s living things were the ones most likely toextinguish them. no one represented this position on a larger scale (in every sense) than lionel walterrothschild, the second baron rothschild. scion of the great banking family, rothschild was astrange and reclusive fellow. he lived his entire life in the nursery wing of his home at tring,in buckinghamshire, using the furniture of his childhood even sleeping in his childhoodbed, though eventually he weighed three hundred pounds. his passion was natural history and he became a devoted accumulator of objects. he senthordes of trained men as many as four hundred at a time to every quarter of the globe toclamber over mountains and hack their way through jungles in the pursuit of newspecimens particularly things that flew. these were crated or boxed up and sent back torothschild’s estate at tring, where he and a battalion of assistants exhaustively logged andanalyzed everything that came before them, producing a constant stream of books, papers, andmonographs some twelve hundred in all. altogether, rothschild’s natural history factoryprocessed well over two million specimens and added five thousand species of creature to thescientific archive. remarkably, rothschild’s collecting efforts were neither the most extensive nor the mostgenerously funded of the nineteenth century. that title almost certainly belongs to a slightlyearlier but also very wealthy british collector named hugh cuming, who became sopreoccupied with accumulating objects that he built a large oceangoing ship and employed acrew to sail the world full time, picking up whatever they could find birds, plants, animalsof all types, and especially shells. it was his unrivaled collection of barnacles that passed todarwin and served as the basis for his seminal study. however, rothschild was easily the most scientific collector of his age, though also themost regrettably lethal, for in the 1890s he became interested in hawaii, perhaps the mosttemptingly vulnerable environment earth has yet produced. millions of years of isolation hadallowed hawaii to evolve 8,800 unique species of animals and plants. of particular interest torothschild were the islands’ colorful and distinctive birds, often consisting of very smallpopulations inhabiting extremely specific ranges. the tragedy for many hawaiian birds was that they were not only distinctive, desirable, andrare a dangerous combination in the best of circumstances but also often heartbreakinglyeasy to take. the greater koa finch, an innocuous member of the honeycreeper family, lurkedshyly in the canopies of koa trees, but if someone imitated its song it would abandon its coverat once and fly down in a show of welcome. the last of the species vanished in 1896, killedby rothschild’s ace collector harry palmer, five years after the disappearance of its cousin thelesser koa finch, a bird so sublimely rare that only one has ever been seen: the one shot forrothschild’s collection. altogether during the decade or so of rothschild’s most intensivecollecting, at least nine species of hawaiian birds vanished, but it may have been more. rothschild was by no means alone in his zeal to capture birds at more or less any cost.others in fact were more ruthless. in 1907 when a well known collector named alansonbryan realized that he had shot the last three specimens of black mamos, a species of forestbird that had only been discovered the previous decade, he noted that the news filled him with“joy.” it was, in short, a difficult age to fathom a time when almost any animal was persecuted ifit was deemed the least bit intrusive. in 1890, new york state paid out over one hundredbounties for eastern mountain lions even though it was clear that the much harassed creatureswere on the brink of extinction. right up until the 1940s many states continued to paybounties for almost any kind of predatory creature. west virginia gave out an annual collegescholarship to whoever brought in the most dead pests and “pests” was liberally interpretedto mean almost anything that wasn’t grown on farms or kept as pets. perhaps nothing speaks more vividly for the strangeness of the times than the fate of thelovely little bachman’s warbler. a native of the southern united states, the warbler wasfamous for its unusually thrilling song, but its population numbers, never robust, graduallydwindled until by the 1930s the warbler vanished altogether and went unseen for many years.then in 1939, by happy coincidence two separate birding enthusiasts, in widely separatedlocations, came across lone survivors just two days apart. they both shot the birds, and thatwas the last that was ever seen of bachman’s warblers. the impulse to exterminate was by no means exclusively american. in australia, bountieswere paid on the tasmanian tiger (properly the thylacine), a doglike creature with distinctive“tiger” stripes across its back, until shortly before the last one died, forlorn and nameless, in aprivate hobart zoo in 1936. go to the tasmanian museum today and ask to see the last of thisspecies the only large carnivorous marsupial to live into modern times and all they canshow you are photographs. the last surviving thylacine was thrown out with the weekly trash. i mention all this to make the point that if you were designing an organism to look after lifein our lonely cosmos, to monitor where it is going and keep a record of where it has been, youwouldn’t choose human beings for the job. but here’s an extremely salient point: we have been chosen, by fate or providence orwhatever you wish to call it. as far as we can tell, we are the best there is. we may be allthere is. it’s an unnerving thought that we may be the living universe’s supreme achievementand its worst nightmare simultaneously. because we are so remarkably careless about looking after things, both when alive andwhen not, we have no idea really none at all about how many things have died offpermanently, or may soon, or may never, and what role we have played in any part of theprocess. in 1979, in the book the sinking ark, the author norman myers suggested thathuman activities were causing about two extinctions a week on the planet. by the early 1990she had raised the figure to some six hundred per week. (that’s extinctions of all types plants, insects, and so on as well as animals.) others have put the figure even higher to wellover a thousand a week. a united nations report of 1995, on the other hand, put the totalnumber of known extinctions in the last four hundred years at slightly under 500 for animalsand slightly over 650 for plants while allowing that this was “almost certainly anunderestimate,” particularly with regard to tropical species. a few interpreters think mostextinction figures are grossly inflated. the fact is, we don’t know. don’t have any idea. we don’t know when we started doingmany of the things we’ve done. we don’t know what we are doing right now or how ourpresent actions will affect the future. what we do know is that there is only one planet to do iton, and only one species of being capable of making a considered difference. edward o.wilson expressed it with unimprovable brevity in the diversity of life: “one planet, oneexperiment.” if this book has a lesson, it is that we are awfully lucky to be here and by “we” i meanevery living thing. to attain any kind of life in this universe of ours appears to be quite anachievement. as humans we are doubly lucky, of course: we enjoy not only the privilege ofexistence but also the singular ability to appreciate it and even, in a multitude of ways, tomake it better. it is a talent we have only barely begun to grasp. we have arrived at this position of eminence in a stunningly short time. behaviorallymodern human beings that is, people who can speak and make art and organize complexactivities have existed for only about 0.0001 percent of earth’s history. but surviving foreven that little while has required a nearly endless string of good fortune. we really are at the beginning of it all. the trick, of course, is to make sure we never findthe end. and that, almost certainly, will require a good deal more than lucky breaks.

i focus on the luminaries of music, film, art, photography and related fields, but i have also found great satisfaction in writing about contemporary philosophers, explorers, rodeo stars, chefs and 1960s activists, along with many athletes (another favorite topic). for the first 25 years of my career, i often joked with friends about how ironic it was that i specialized in lifestyle journalism and popular culture, perpetually focused on the next, the hot, the new, when my real secret love was history. no wonder i was thrilled to join the obituaries desk in the summer of 2022. it has been a great joy to channel my fascination with 20th century history   in particular, the culture and the arts of the postwar era   into a regular stream of mini biographies of fascinating people from that era. i still focus on the vibrant and dynamic figures who shape society and culture   just at the other end of their lives. i joined the times in 2004 as a reporter on the styles desk and spent 18 years writing profiles of celebrities, tastemakers, entrepreneurs and other notables, as well as articles on men’s style. i grew up in the san francisco bay area and, later, the los angeles region. after graduating from the university of california, berkeley, with a degree in rhetoric, i worked as a reporter for two newspapers in orange county, calif., before moving to new york, where i took a job as a fact checker at new york magazine and ended up spending more than a dozen years there as a writer. i have always been committed to the core principles of the times, to report as objectively as possible on all topics, free from political or philosophical bias. by the nature of my job with obituaries, i write about people from a vast array of backgrounds and cultures, and i do everything in my power to understand my subjects in the context of their upbringing, worldview and historical period. email: alexwill@nytimes.com anonymous tips: nytimes.com/tips with a daring avant garde approach, she pushed the frontiers of an instrument best known for speaking with a down home accent. by alex williams a founder of murder inc. records, he helped launch the careers of ja rule and ashanti and was credited as a producer on 28 records that made the billboard hot 100. by alex williams and john yoon he played keyboards with a host of rock luminaries, but perhaps his most memorable performance was as part of the band that shocked the 1965 newport folk festival. by alex williams after chronicling the crack boom of the 1980s as an investigative reporter, he had a high profile but brief second career in hollywood. by alex williams the hit 1966 surfing documentary immortalized the maverick california wave rider as an archetype of the footloose rebel surfer. by alex williams striving to widen the audience of dance, she brought vitality to broadway musicals like “swing!” as well as ballets and hollywood films. by alex williams undersized but speedy and known as the wizard for his acrobatics, he was a high scorer who in 1979 starred in a series that brought the supersonics their only crown. by alex williams a cuban born minimalist painter who spent much of her life in puerto rico, she was in her 90s when her erotically charged work first appeared at the venice biennale. by alex williams she became a photographer the same year she came out, chronicling the lives of women in same sex relationships   something most people had never seen. by alex williams the duo brewer & shipley reached the top 10 in 1971 with “one toke over the line,” a ditty about marijuana that ran afoul of nixon era censors. by alex williams an esteemed spanish actress, she was best known for her work in pedro almodóvar’s movies like “all about my mother.” but their relationship was stormy. by alex williams a top selling pop singer as a teenager in the 1980s, she also had an award winning career as a dramatic actress. by alex williams she found outsize success in her native land and gained international recognition for her work with the acclaimed spanish surrealist director luis buñuel. by alex williams while never a big star, he was a recognizable one, with roles in “the twilight zone,” “giant,” “forbidden planet” and the 1970s series “police woman.” by alex williams musician, singer, songwriter, producer and more, he collaborated with madonna and a raft of other artists and helped resuscitate the career of the beach boys’ brian wilson. by alex williams his dozens of songs included “non, je ne regrette rien,” a powerful anthem of redemptive love that became one of piaf’s signature songs. by alex williams his swirls of imagery helped define progressive rock in the 1970s. he later turned his focus to pop acts like celine dion. by alex williams though he was american, he helped define the sound of the british invasion after settling in london in the early 1960s. by alex williams credited with designing the first eco friendly office building, he never forgot the lessons he learned observing communes in the 1960s. by alex williams jumping from the high school ranks to lead one of the most storied programs in college football, he lost games but rarely lost hope. by alex williams with her husband, david laflamme, she founded the rock band it’s a beautiful day and wrote a soaring paean to a generation’s dreams of escape. by alex williams best known for his star turn in the cult film about a flesh eating plant, he was a go to member of the low budget auteur roger corman’s repertory company. by alex williams out from under an imposing shadow, she recorded four albums as a singer and had two r&b hits before turning her focus to her brother’s legacy. by alex williams a groundbreaking environmental artist, she transformed water treatment plants and fetid ponds into enticing natural artworks. by alex williams he overcame a dip in velocity to find pitching success with four teams, including the yankees and orioles, and had a dominant season in 1980. by alex williams she was best known as half of a comedy team with her husband, phil ford, until her hall filling voice earned her raves in a role made famous by barbra streisand. by alex williams she was highly regarded as a folk, blues and jazz singer. she was also ardently left wing and prioritized social change over commercial success. by alex williams her “love has no pride” was widely recorded, and she had high profile relationships with levon helm and donald fagen. but she was uneasy with life in the spotlight. by alex williams arriving at the luxury house two years after karl lagerfeld, he helped guide a boom in both products and revenues as president of the company’s american arm, chanel inc. by alex williams he was the only inductee to play his entire career in the american football league, where he helped the buffalo bills win two championships in the 1960s. by alex williams known for his legs as well as for his arm, he was the last detroit lions quarterback to make the pro bowl for more than 40 years. by alex williams she often took time away from the tour for her family. but she tallied 11 championships, including three in the u.s. women’s open. by alex williams he drew from his black and native american heritage, as well as his own memory, to find an emotional resonance behind the beauty of nature. by alex williams her work often drew from her upbringing in california amid world war ii, such as her intricate novel about the nazi leader hermann goering. by alex williams a blues devotee from chicago, he tasted fame in the late 1960s with the electric flag, a band that made its debut at monterey but proved short lived. by alex williams starting in the early 1960s, he set himself apart from his contemporaries with paintings that critiqued the cultural dominance of the united states. by alex williams a celebrated session musician who appeared on a host of classic rock albums, he made his most lasting mark with his contribution to lou reed’s most famous song. by alex williams a new yorker of puerto rican descent, he helped start a collective that brought recognition to hispanic photographers and illuminated life in the city’s barrios. by alex williams celebrity chefs and politicians paid tribute to the man behind the extra thick shake known as the concrete, an intrinsic part of st. louis summers. by alex williams he tracked the rise of grunge as the editor of the seattle music magazine the rocket. he also wrote acclaimed books about two of the city’s most celebrated rock luminaries. by alex williams a chart topper in 1960 for his doo wop group the zodiacs, it inspired popular cover versions and was heard in the 1987 film “dirty dancing.” by alex williams he carved out a place for no nonsense power pop at the height of the mtv 1980s. by alex williams and alexandra e. petri in his posts atop the governing bodies for african and global soccer, he fought to establish the continent as an equal to europe and south america. by alex williams with her smoky voice and her high fashion look, the self proclaimed “punk of fado” found stardom by shaking up a venerable portuguese genre. by alex williams as an outfielder, he hid his sexual identity from his teammates for nearly a decade before retiring and becoming a force for inclusion in the organization. by alex williams an oxford graduate who spoke five languages, she had an early career as a siren before finding critical acclaim in masterworks by federico fellini and roman polanski. by alex williams he drew praise for his blues inflected fretwork as his critically acclaimed band rode high, if briefly, during san francisco’s summer of love. by alex williams she was, she said, unable to cook a basic meal into her mid 20s. but she went on to a successful career as a restaurateur and an authority on asian cuisine. by alex williams a noted guitarist and banjo player, he emerged from the same greenwich village folk revival scene as his friend and sometime collaborator bob dylan. by alex williams he used his platforms on cnn and fox business to share baseless conspiracy theories. his tenure at fox ended after the network was sued for defamation over claims of voting machine fraud. by alex williams and michael levenson after tasting fame with “please come to boston” in 1974, he became a major nashville songwriter. he also wrote the theme to the masters golf tournament. by alex williams a promising player for a storied norwegian soccer club, he instead found infamy for stealing one of the world’s most famous artworks. by alex williams a founder of the influential music magazine the fader, he also bridged the worlds of hip hop and the fortune 500 with his innovative marketing agency. by alex williams a former hippie who chafed at wealth, she married a chicago real estate titan and, after his death, donated hundreds of millions in her adopted city and beyond. by alex williams hailed as a pioneer of d.i.y. programming, he oversaw groundbreaking how to shows on public television in the days before hgtv and youtube. by alex williams he overcame segregation at home and in the military to serve three tours in vietnam as a member of the storied special operations unit. by alex williams starting in the late 1970s, she scored multiple hit singles, including “this time i’ll be sweeter” and “i try,” but a pair of strokes in the 2000s ended her career. by alex williams a core member of the anti art movement fluxus, he died by suicide hours after the death of his wife of 60 years. by alex williams the concertmaster and first chair violinist with the philadelphia orchestra for decades, he took part in a diplomatic breakthrough in 1973 with concerts in mao zedong’s beijing. by alex williams a rare supercentenarian, he remained remarkably lucid after 11 decades, even maintaining a blog. his brain has been donated for research on what’s known as super aging. by alex williams even on the star studded dallas cowboys roster of the 1990s, he stood out with his head turning strength and bone rattling pancake blocks. by alex williams the “mighty atom” enjoyed a glittering professional career in britain before gaining more acclaim for his charity efforts after a diagnosis of motor neuron disease. by alex williams she made only two films, but her “araya,” a rumination on the daily rituals of salt mine laborers, became an enduring work of latin american cinema. by alex williams his biggest hit, “in a gadda da vida,” was a 17 minute psychedelic journey that epitomized 1960s rock indulgence. but after just a few years in the limelight, he walked away. by alex williams best known for movies like “romancing the stone,” he also made a mark as a producer, a real estate developer and the butt of a generation x friendly television gag. by alex williams with her collaborator, elaine mazlish, she wrote “how to talk so kids will listen & listen so kids will talk” and other books that have endured as parenting bibles. by alex williams arising from the free form san francisco radio scene of the 1960s, he became an influential voice on the powerhouse wplj in new york. by alex williams he challenged racial barriers in hollywood, was a producer of “the fresh prince of bel air” and earned a tony nomination for “home,” a paean to his southern roots. by alex williams for 366 days, he captured intimate images of the singer songwriter as he changed the look and sound of the 1960s. by alex williams he was best known as a jazz musician, but his shimmering sound was also heard on classic albums by david bowie, stevie wonder and bruce springsteen. by alex williams a renowned member of the new york school of poets, he also found accidental notoriety when he was photographed during the 1968 uprising at columbia university. by alex williams a founding dancer with the groundbreaking company, she served not only as a principal dancer but also as its first ballet mistress. by alex williams an influential arts administrator and educator, he was a trusted confidant to countless writers, notably philip roth. by alex williams with critically lauded works like “the new york trilogy,” the charismatic author drew inspiration from his adopted borough and won worldwide acclaim. by alex williams a groundbreaking audio engineer, he provided the large scale systems that brought tours by the who and the grateful dead to life. by alex williams he traded licks with duane allman and proved to be a worthy sparring partner. he also wrote, and sang, the band’s biggest hit, “ramblin’ man.” by alex williams in her 60s, she set off on a hulking harley davidson and found a new area of anthropological research: bikers, and in particular, female bikers. by alex williams michael lindsay hogg’s unloved   or misinterpreted?   1970 documentary, the source for peter jackson’s “get back,” will stream on disney+. by alex williams he brought worldwide attention to a radical yet elemental form of contemporary dance that emerged in the wake of wartime destruction. by alex williams a musical voyager who wouldn’t be limited by genre, style or even instrument, he brought exuberance to the robert glasper experiment and other groups. by alex williams

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supported by the “mighty atom” enjoyed a glittering professional career in britain before gaining more acclaim for his charity efforts after a diagnosis of motor neuron disease. by alex williams rob burrow, a rugby standout who overcame his diminutive stature with fleetness and ferocity to become an eight time champion of britain’s super league and who was later hailed for raising awareness of motor neuron disease after being diagnosed with it in 2019, died on sunday. he was 41. his death   from m.n.d., a group of neurological disorders that includes amyotrophic lateral sclerosis, or a.l.s., also known as lou gehrig’s disease   was announced by the leeds rhinos, the british rugby league club with which he spent his entire 17 year professional career. it did not say where he died. doubted at every turn for his small stature   he was about 5 foot 5 and 150 pounds   burrow nevertheless became a star, earning nicknames like mighty atom and pocket rocket in the british tabloids. he was sapped of his physical gifts, however, when he was diagnosed with his neurological disorder at 37, just two years after his retirement in 2017. despite enduring an incurable illness in which muscles waste away, making even eating and breathing an ordeal, burrow banded with his close friend and former teammate kevin sinfield to raise millions for research on m.n.d. and to support people with it, including establishing a care center in leeds, in northern england. in a much publicized fund raising challenge last december, sinfield ran seven marathons in seven days in seven cities, each with a 27th mile tacked on to inspire people to go the “extra mile” for friends in need.

 academia.edu no longer supports internet explorer. to browse academia.edu and the wider internet faster and more securely, please take a few seconds to upgrade your browser. enter the email address you signed up with and we'll email you a reset link. download free pdf … 212 pages 1 file perhaps you're reading this while browsing in a bookstore. if so, glance over at the guy down the aisle when he's not looking, the one pretending to be engrossed in the stephen hawking book. take a good look at him. he's probably not missing fingers from leprosy, or covered with smallpox scars, or shivering with malaria. instead, he probably appears perfectly healthy, which is to say he has the same diseases that most of us have cholesterol levels that are high for an ape, hearing that has become far less acute than in a hunter gatherer of his age, a tendency to dampen his tension with valium. we in our western society now tend to get different diseases than we used to. but what's more important, we tend to get different kinds of diseases now, with very different causes and consequences.