Frank Wilczek: Physics of Quarks, Dark Matter, Complexity, Life & Aliens | Lex Fridman Podcast #187
the following is a conversation with frank wilceck a theoretical physicist at mit who won the nobel prize for the co-discovery of asymptotic freedom in the theory of strong interaction quick mention of our sponsors the information netsuite expressvpn blinkist and a sleep check them out in the description to support this podcast as a side note let me say a word about asymptotic freedom protons and neutrons make up the nucleus of an atom strong interaction is responsible for the strong nuclear force that binds them but strong interaction also holds together the quarks that make up the protons and neutrons frank wilcek david gross and david pulitzer came up with a theory postulating that when quarks come really close to one another the attraction abates and they behave like free particles this is called asymptotic freedom this happens at very very high energies which is also where all the fun is this is the lex friedman podcast and here is my conversation with frank wilcheck what is the most beautiful idea in physics the most beautiful idea in physics is that we can get a compact description of the world that's very precise and very full at the level of the operating system of the world um that's an extraordinary gift and we get we get worried when we uh have find discrepancies between our uh description of the world and and what's actually observed at the level even of a part in a billion you actually have this quote from einstein that the the most incomprehensible thing about the universe is it's co is that it is comprehensible something like that yes that's so that's the most beautiful surprise that i think uh that that really was the to me the most profound result of the scientific revolution of this of the 17th century with uh the shining example of newtonian physics that you could aspire to completeness precision and a concise description of the world of the operating system and it's gotten better and better over the years and that's the continuing miracle now there are a lot of beautiful sub-miracles too the form of the equations is governed by high degrees of symmetry and and they have a very surprising kind of mind-expanding structure especially in quantum mechanics but if we have to say that the single most beautiful revelation is that in fact uh the world is comprehensible would you say that's a fact or hope it's a fact we can do we you can point to things like uh the rise of uh gross pro gross national products grow you know per capita around the world as a result of the scientific revolution you can see it all around you uh uh uh in in recent developments with exponents so exponential production of wealth control of nature at uh a very profound level where we do things like sense tiny tiny tiny tiny vibrations to tell that there are black holes colliding far away or we uh test laws as i alluded to whether to part in a billion and do you know things and what appear on the surface to be entirely different conceptual universes i mean on the one hand pencil and paper or nowadays computers that that calculate abstractions and on the other hand magnets and accelerators and detectors that look at the behavior of fundamental particles and and these different universes have to agree or else we get very upset and that's uh it's an amazing thing if you think about it so and it's telling us that we do understand a lot about nature at a very profound level and uh there are still things we don't understand of course but as we get better and better answers and better and better ability to address difficult questions we can ask more and more ambitious questions well i guess the hope part of that is because we are surrounded by mystery so we've one way to say it if you look at the growth the gdp over time that we figured out quite a lot and we're able to improve the quality of life because of that and we've figured out some fundamental things about this universe but we still don't know how much mystery there is and it's also possible that there's some things that are in fact incomprehensible to both our minds and the tools of science like we the the sad thing is we may not know it because in fact they are incomprehensible and that's the open question is how much of the universe is comprehensible if we figured out the the everything uh what's inside the black hole and everything that happened at the moment of the big bang does that still give us the key to understanding the human mind and the the emergence of all the beautiful complexity we see around us that's not uh like when i when i see these objects like i don't know if you've seen them like cellular automata uh all these kinds of objects where the from simple rules emerges complexity yes it makes you wonder maybe it's not reducible to simple beautiful equations the whole thing only parts of it that's the tension i was getting at with the hope well when we say the universe is comprehensible we have to kind of draw careful distinctions about or uh definitions about what what we mean by by that uh both the university and the con and the comprehensive exactly right so uh the so in certain areas of understanding reality we've made extraordinary progress i would say in understanding fundamental physical processes and getting very precise equations that really work and allow us to do uh the profound sculpting of matter you know to make computers and iphones and everything else and they really work and they're extraordinary productions uh on the other but uh and that's all based on the laws of quantum mechanics and you know they really and they really work and then uh and they give us tremendous control of nature on the other hand uh as i said as with as we get better answers we can also ask more ambitious questions and there are certainly things that have been observed even in the in what would be usually called the realm of physics that aren't understood for instance there seems to be another source of mass in the universe the so-called dark matter that we don't know what it is and it's a very interesting question what it is then uh but also as you were alluding to there there's it's one thing to know the basic equations it's another thing to be able to solve them in in important cases so we run a we run up against the limits of that in things like chemistry where we'd like to be able to design molecules and predict their behavior from the equations we think the equations could do that in principle but but uh in practice it's very challenging to solve them in in all but very simple cases uh and then there's the other thing which is that a lot of what we're interested in is uh historically conditioned it's not uh it's not a matter of the fundamental equations but about what has evolved or come out of of the early universe and formed into people and frogs and societies and things and the laws of physic the basic laws of physics only take you so far in the in that it kind of provides a foundation but doesn't really you need entirely different concepts to deal with uh those kind of uh and all we one thing i can say about that is that the laws themselves point out their limitations that they kind of their laws for dynamical evolution so they tell you what happens if you have a certain starting point but they don't tell you what the starting point should be at least yeah and uh the other the other thing that emerges from the equations themselves is the phenomena of chaos and sensitivity to initial conditions which tells us that you have that there are intrinsic limitations on how well we can spell out the consequences of the laws if we try to apply them see all the apple pie if you want to what does it make an apple pie from scratch you have to build the universe or something like that well you're much better off starting with apples than starting with quarks let's put it that way in your uh book a beautiful question you ask does the world embody beautiful ideas so the book is centered around this very interesting question it's like shakespeare you can like dig in and read into all the different interpretations of this question but at the high level what to use the connection between beauty of the world and physics of the world in a sense we now have a lot of insight into what the the laws are the for the form they take that and allow us to understand matter in great depth and control it as we as we've discussed uh it's an extraordinary thing how mathematically ideal those equations turn out to be in the early days of greek philosophy uh plato had this model of atoms built out of the five perfectly symmetrical platonic solids so there was somehow the idea that mathematical symmetry uh should govern the world and uh we've outplated plato by far in modern physics because we have symmetries that are much more extensive much more powerful that turn out to be uh the ingredients out of which we construct our theory of the world and and it works and uh so that's certainly beautiful so the the math the idea of symmetry which is uh a driving inspiration in much of human art uh especially a decorative art or like the alhambra or in wallpaper designs or things you see around you everywhere uh also turns out to be the dominant theme in modern fundamental physics symmetry and its manifestations the laws turn out to be very to have these tremendous amounts of symmetry you can change the symbols and move them around in different ways and they still have the same consequences uh that so that's that's uh beautiful and uh that that uh these things uh these different these concepts that humans find appealing also turn out to be the concepts that govern how the world actually works and i don't think that's an accident i think the humans were evolved to be able to interact with the world in in ways that are advantageous and to learn from it and so we are naturally evolved or designed to enjoy beauty and and it's a symmetry and this and the world has it and that's no that's why we that's why we resonate with it well it's interesting that the ideas of symmetry emerge at all at many levels of the hierarchy of the universe so you're talking about particles but it also is at the level of chemistry and biology and um and the fact that our cognitive sort of our perception system and whatever our cognition is also finds it appealing or somehow our sense of what is beautiful is grounded in this idea of symmetry or the breaking of symmetry symmetry is at the core of our conception of beauty whether it's the breaking or the non-breaking of the symmetry it makes you wonder why why like uh so i come from russia in the in the question of dostoyevsky he's he has said that beauty will save the world maybe maybe as a physicist you can tell me what do you think he meant by that i don't i don't know if it saves the world but it does turn out to be a tremendous source of insight into the world when we uh investigate kind of the the most fundamental interactions things that are hard to access because they occur at very short distances between very uh special kinds of particles whose properties are only revealed at high energies we don't have much to go on from everyday life but so we have when we guess what the so we and then the experiments are difficult to do so you can't you can't really uh follow a very uh holy empirical procedure to sort of step in the baconian style figure out the laws kind of step by step just by accumulating a lot of data what we actually do is guess and the guesses are kind of aesthetic really what what would be a nice description that's consistent with what we know and then you try it out and see if it works and then and by gosh it does in in some in many profound cases uh so there's that but there's another source of symmetry which i didn't talk so much about in uh in a beautiful question but does uh relate to your comments and i think very much relates to uh the source of symmetry that we find in biology and uh in in our in our heads you know in our brain which is that uh although i'd well it is discussed a bit in in a beautiful question and and also in fundamentals is that when you have symmetry is also a very important means of construction so when you have for instance simple viruses that that need to construct their coat their protein coat the coats often take the form of platonic solids and the reason is that the viruses are really dumb and they only know how to do one thing so they make a pentagon then they make another pentagon and they make another pentagon and they all glue together in the same way and that makes a very symmetrical object sort of so the rules of development when you have simple rules and they go they work again and again you get symmetrical patterns that's it's kind of in in fact it's a recipe also for generating fractals you know really like uh the kind of broccoli that has all this internal structure and i wish i had a picture to ship that many people remember it from the from the uh uh from the supermarket and then and you say how did a vegetable get so intelligent to make such a beautiful object of all this fractal structure and the the the secret is stupidity you just do the same thing over and over again and uh in our brains also you know we've we came out we start from single cells and they reproduce and they they're each one does basically roughly the same thing they they uh the the program evolves in time of course different different modules get turned on and off genetic different regions of the genetic code get turned on and off but uh but basically a lot of the same things are going on and they're simple things and so you produce the same patterns over and over again and that's a recipe for producing symmetry because you're getting the same thing in many many places and if you look at for instance the beautiful drawings of rahman ikahal the great neuroanatomist who drew the structure of different organs like the hippocampus you see it's very regular and very intricate and it's symmetry in in this in in that sense it's because it's it's it's many repeated units that that uh you can take from one place to the other and see that they look more or less the same but what you're describing this kind of beauty that we're talking about now is a very small sample in terms of space-time in a very big world in a very short brief moment in this long history in your book fundamentals 10 keys to reality i'd really recommend people read it you uh you say that space and time are pretty big or very big how big are we talking about like what uh can you draw can you tell a brief history of space and time it's easy to tell a brief history but the details get very involved of course but uh one thing i'd like to say is that if if if you take a broad enough view the history of the universe is simpler than the history of sweden say because you don't you your standards are lower for for but just to make it a a a quantitative i'll just give a few highlights and it's it's it's a little bit easier to talk about time uh so let's start with that the big bang occurred we think the universe was much hotter and denser and more uniform about 13.8 billion years ago and that's what we call the big bang and it's been expanding and cooling the matter in it has been expanding and cooling ever since so in a real sense the universe is 13.8 billion years old that's a big number kind of hard to think about a a nice way to think about it though is to map it on to one year so if so let's say the universe just linearly map the time intervals from 13.8 billion years on to one year so the the big bang then is that on january 1st at 12 a.m and uh you wait for quite a long time before the dinosaur has emerged the dinosaurs emerge on christmas it turns out almost 12 months later getting close to the end yes and the extinction event that uh let mammals and ultimately humans inherit the earth from from the dinosaurs occurred on december 30th and all of human history is a small part of the last day and so so yes so we we're occupying only a human lifetime is a very very infinitesimal part of this uh interval of these gigantic cosmic reaches of time uh and in space we can tell a very similar story in fact a very uh it's convenient to think that the size of the universe is the distance that light can travel in 13.8 billion years that's so it's 13.8 billion light years that's that's how far you can see out that's how far things can signals can reach us from and um that is a big distance because compared to that uh the the universe that the earth is a fraction of a light second so again we it's really really big and so we have if we want to think about the universe as a whole in space and time we really need a different kind of imagination it's not it's not something you can grasp in terms of psychological time in a useful way you have to think you know you have to use exponential notation and abstract concepts to really get any uh hold on on on these vast times and spaces on the other hand let me hasten to add that that doesn't make us small or make the time that we have to us small because uh again looking at those pictures of you know what our minds are in some sense of components of our minds these beautiful drawings of the cellular patterns inside the brain you see that there are many many many processing units and if you analyze how fast they operate i try to estimate how many thoughts a person can have in a lifetime that's kind of a fuzzy question but i'm very proud that i i was able to define it pretty precisely and it turns out we can we have time for billions of meaningful thoughts you know in a lifetime so so it's a lot we shouldn't we shouldn't think of ourselves as terribly small either in space or in time because although we're small in those dimensions compared to the universe where we're large compared to meaningful units of processing information and and being able to conceptualize and understand things yeah but 99 of those thoughts are probably food sex or internet related but yeah yeah well they're not that's right only like point one is nobel prize winning ideas but that's true but uh you know there's more to life than winning nobel prizes how did you um do that calculate can you maybe break that apart a little bit just kind of for fun sort of an intuition of how we calculate the number of thoughts the number of thoughts right there they're it's necessarily imprecise because a lot of things are going on in different ways and what is a thought but there are several things that point to more or less the same [Music] uh rate of being able to have meaningful thoughts uh for instance i'm the one that i think is maybe the most penetrating is uh how fast we can we can process visual images how to how do we do that if you've ever watched old movies you can see that that when well any movie in fact that in a motion picture is really not a motion picture it's a series of snapshots that are playing one after the other and it's the because our brains also work that way we take snapshots of the world integrate over a certain time and then go on to the next one and then by post-processing create the illusion of continuity and flow we can deal with that and uh the if the flicker rate is too slow then you start to see that it's not it's a series of snapshots and you can ask what is the what is the crossover when does it change from being something that that is matched to our processing speed versus too fast and and it turns out about 40 per second and then if you take 40 per second as as how well we how fast we can process visual images you get to several billions of thoughts uh if you similarly if you ask what what are some of the fastest things that people can do well you can they can play video games they can play the piano very fast if if they're skilled at it and again you get to similar uh units or how fast can people talk you get to sim you know within a couple of orders of magnitude you get more or less to the same idea so uh so that's how you can say that that there's there's billions of meaning there's room for billions of meaningful thoughts yeah i won't argue for exactly 2 billion versus 1.8 billion it's not that kind of question but but i think any estimate that's reasonable will come out within say a hundred billion and a hundred million so it's a lot [Laughter] it would be interesting to map out for an individual human being the landscape of thoughts that they've sort of traveled if you think of thoughts as a set of trajectories uh what what that landscape looks like i mean i've been recently really thinking about uh this richard dawkins idea of memes and just all these ideas and the evolution of ideas inside of one particular human mind and how there's there then changed and evolved by interaction with other human beings it's interesting to think about so if you think the numbers billions you you think there's also social interaction so these aren't uh like there's interaction in the same way you have interaction with particles there's interaction between human thoughts uh that are perhaps that's that interaction in itself is fundamental to the process of thinking like without social interaction we would be like stuck like walking in a circle we need we need the perturbation of other humans to create change in evolution once you bring in concepts of uh interactions and correlations and relations then you have what's called a combinatorial explosion that the number of possibilities rap expands exponentially technically with the number of the number of things you're considering and uh it can easily rapidly outstrip these these billions of thoughts that we're talking about so we we definitely uh cannot by brute force master complex situations and or think about think of all the possibilities in complex situations i mean you know even even something as relatively simple as chess is still something that human beings can't comprehend completely even the best players lose still sometimes lose and they consistently lose to computers these days uh and in computer science there's a concept of np complete so large classes of problems when you scale them up beyond a few individuals become intractable and so that in that sense uh the world is inexhaustible but and that makes it beautiful that we can make uh any laws that generalize efficiently and well can compress all of that combinatorial complexity just like a simple rule that that itself is beautiful it's a happy situation and i i think that that we can find general principles of sort of of the operating system that are comprehensible simple extremely powerful and let us control things uh very well and and ask profound questions and on the other hand that the world is going to be inexhaustible that once we start asking about relationships and how they evolve and social interactions and the the the we'll never have a theory of everything in any meaningful sense because of everything everything truly everything is uh can i ask you about the big bang uh so we talked about the space and time are really big but then and we humans give a lot of meaning to the word space and time in our in our like daily lives but then can we talk about this moment of beginning and how we're supposed to think about it that at the moment the big bang everything was uh what like infinitely small and then it just blew up we have to be careful here because there's a there's a common misconception that the big that the big bang is like the explosion of a bomb in empty space that that uh fills up the surrounding place it is space it is yeah as we understand it it's the fact it's the the fact or the hypothesis but well supported up to a point that that that everywhere in the whole universe early in the history uh matter came together into a very hot very dense if you run it backwards in time matter comes together into a very hot very dense and yet very homogeneous plasma of all the different kinds of elementary particles and quarks and anti-quarks and gluons and photons and electrons and anti-electrons everything you know all of that stuff like really hot really really really hot we're talking about uh way way hotter than the surface of the sun uh you know well in fact if you take the equations as we as they come the the prediction is that the temperature just goes to infinity but then the equations uh break down we don't you know we don't don't really with their various the equations become infinity equals infinity so they don't feel that it's called a singularity we don't really know uh this is running the equations backwards so you can't really get a sensible idea of what happened before the big bang we don't you know so we need different equations to address the very earliest moments uh that uh but so things were hotter and denser we don't really know why things started out that way we do we have a lot of evidence that they did start out that way uh but since most of the uh you know we don't get to visit there and do controlled experiments most most of the most of the record is is very very processed and we have to we have to use uh very uh subtle techniques and powerful instruments to to get information that has survived get closer and closer to the get closer and closer to the the beginning of things and what's revealed there is that uh as i said there what there undoubtedly was a period when everything in the universe that we have been able to look at and understand and that's consistent with everything is uh um the was in a condition where it was much much hotter and much much denser but still obeying the laws of physics as we know them today and and then you start with that so all the matter is in equilibrium uh and then with small quantum fluctuations and run it forward and then it produces in at least in broad strokes the universe we see around us today do you think we'll ever be able to with the tools of physics with the way sciences with the way the human mind is we'll ever be able to get to the moment of the big bang in our understanding or even the moment before the big bang can we understand what happened before the big bang i'm i'm optimistic both that we'll be able to uh measure more so observe more and that we'll be able to figure out more so uh they're very very tangible prospects for uh observing the extremely early universe so much even much earlier than we can observe now uh through looking at gravitational waves gravitational waves since they interact so weakly with ordinary matter uh sort of send an un a minimally processed signal from the big bang it's a very weak signal because it's traveled a long way and diffused over long spaces but uh but people are gearing up to try to detect gravitational waves that could have come from the early universe yeah ligo's incredible engineering project is the most sensitive precise yes devices on earth the fact that humans can build something like that is uh truly awe-inspiring from an engineering perspective right and but these gravitational waves from the early universe would probably be of a much longer wavelength than lyco is capable of sensing so there's a beautiful project uh that's contemplated to put lasers in different parts different locations in the solar system you know we really really separated by uh solar system scale differences like artificial planets or moons in different places and and see the tiny motions of those relative to one another as a signal of of radiation from the big bang we can also maybe indirectly see the imprint of gravitational waves from the early universe on uh the photons the the microwave background radiation that that is our present way of of seeing into the earliest universe but those those photons interact much more strongly with matter they're much more strongly processed so they don't give us directly such an unprocessed view of the early universe of the very early universe but if gravitational waves leave some imprint on that as they move through uh we could detect that too and people are trying our as we speak working very hard towards uh towards that goal it's so exciting to think about a sensor the size of a solar system like uh that would be a fantastic i mean that would be a pinnacle artifact of human endeavor to me it would be such uh such an inspiring thing that just we want to know and we go to these extraordinary lengths of making gigantic things that are also very sophisticated because what you're trying to do you you have to understand how they move you have to understand uh the properties of light that that are being used interference between light and you have to be able to make the light with lasers and understand the quantum theory and get the timing exactly right you know it's an extraordinary endeavor involving all kinds of knowledge from the very strong very small to the very large and all in the service of uh curiosity and built on a grand scale so yeah if we did that i love that you're inspired both by by the power of theory and the power of experiments so this is the both both i think are exceptionally impressive that the human mind can come up with theories that give us a peek into how the universe works but also construct tools that are way bigger than uh the the evolutionary origins we came from right and by the way you know the fact that we can design those things and they work yeah is an extraordinary demonstration that we really do understand a lot and then in some ways and it's our ability to answer questions that also leads us to be able to address more ambitious questions so you mentioned that at the at the big bang in the early days things are pretty homogeneous yes but uh here we are sitting on earth to uh hairless apes you could say with microphones in talking about the brief history of things you said it's much harder to describe sweden than it is um the universe so there's a lot of complexity there's a lot of interesting details here so how does this complexity come to be do you think it seems like there's these pockets yeah we don't know how rare of like uh we're hairless apes just emerge yeah and then they came from the initial soup that was homogeneous was that uh yeah accident well we understand there we understand in broad outlines how it could happen we certainly don't understand why it happened exactly and the way it did or but but uh or you know there are certainly open questions about the origins of life and how inevitable the emergence of intelligence was and and how that happened but uh in the very broadest terms uh the universe early on was quite homogeneous but not completely homogeneous there are there were part in 10 000 fluctuations in density within this primordial plasma and uh as time goes on there's an instability which causes those density contrasts to increase there's a gravitational instability where it's denser the gravitational attractions are stronger and so that brings in more matter and it gets even denser and so on and so on so so there's a natural tendency of matter to clump because of gravitational interactions and then the equations get complicated when you have lots of things clumping together uh then you know then then we know what the laws are but we have to to a certain extent wave our hands about what what what happens but uh the basic understanding of chemistry says that if things and and the physics of radiation tells us that if as things start to clump together they can radiate give off some energy so they don't just they slow down they as a result they lose energy they conglomerate together cool down form things like stars form things like planets and so in broad terms there's no mystery there's that that's what the scenario that's what the equations tell you should happen but because it's a process involving many many fundament individual units uh the the the application of the laws that govern individual units to these things is is very delicate uh you know computationally very difficult and more profoundly uh the equations have this probability of chaos or sensitivity to initial conditions which tells you tiny differences in the initial state can lead to enormous differences in the subsequent behavior so so physics fundamental physics at some point says okay chemists biologists this is your problem and and uh and then again in broad terms we know how uh it's conceivable that that the humans and things like that can can uh that how complex structure can emerge it's a matter of uh having the right kind of temperature and the right kind of stuff so you need you need to be able to make chemical bonds that are reasonably stable and be able to make complex structures and we're very fortunate that carbon has this ability to make uh backbones and elaborate branchings and things so you can get complex things that we call biochemistry and and yet the bonds can be broken a little bit with the help of energetic injections from the sun so you have to have both the possibility of changing but also the possible useful degree of stability and we know at that very very broad level physics can tell you that it's conceivable yeah if you want to know what actually what what's what what really happened what really can happen then you have to work a bit to go to chemistry if you have if you want to know what actually happened then you really have to consult the fossil record in biologists and so so uh but but it's it so these these ways of addressing the issue are complementary in a sense they but they uh they uh they use different kinds of concepts they use different uh languages and they address different kinds of questions but they're they're not inconsistent they're just complimentary it's kind of interesting to think about those early fluctuations as our earliest ancestors yes that's right so it's far it's amazing to think that uh you know this is the modern answer to the uh or the modern version of uh the what the hindu philosophers had that art thou if you ask what okay that those those little quantum fluctuations in the early universe are the seeds out of which uh complexity including uh plausibly humans really evolve you don't need anything else that brings up the question of uh asking for a friend here if there's uh you know other pockets of complexity commonly called as uh alien intelligent civilizations out there well we don't know for sure but i i have a strong suspicion that the answer is yes because the uh the one case we do have at hand to study here on earth uh we sort of know what the conditions were that were helpful to life the right kind of temperature the right kind of star that that keeps maintains that temperature for a long time the liquid environment of water and once those conditions emerged on earth which was roughly four and a half billion years ago it wasn't very long before what we call life started to leave relics so we can find the forms of life primitive forms of life that are almost as old as the earth itself in the sense that once the earth became reason was was returned from a a a very hot boiling thing and cooled off into a solid mass with it with water uh life emerged very very quickly so so it seems that these general conditions for life uh are enough to to make it happen uh relatively quickly now the other lesson i would i think that one can uh draw from this one example it's dangerous to the drug lessons from one example but that's all we've got uh and uh that that the emergence of intelligent life is a different issue altogether it uh that took a long time and seems to have been pretty contingent uh the you know the the for a long time well for most most of the history of life it was single-celled things you know uh yes even multicellular life only rose about 600 million years ago so much after you know so and the the uh and then intelligence is kind of a luxury you know if you think uh many more kinds of creatures have uh big stomachs than big brains and in fact uh most most most have no brains at all in any reasonable sense that that then uh and the dinosaurs ruled for a long long time and some of them were pretty smart but they they were at best bird brains because you know birds came from the dinosaurs uh and uh and it could have stayed that way you know and and then human and the emergence of humans was very contingent and kind of a very very recent development on evolutionary time scales and uh you can argue about the level of human intelligence but it's you know i think it's that that's what we're talking about and it's very it's very impressive and can ask these kinds of questions and discuss them intelligently uh the uh so i guess my my so this is a long-winded answer or justification of my feeling is that uh the conditions for life in some form are probably con satisfied many many places around the universe even and even within our galaxy uh i'm not so sure about the emergence of intelligent life or the emergence of technological uh civilizations that that that seems uh much more much more contingent and special and we might it's conceivable to me that we're the only example in the galaxy or although yeah i don't know one way or the other i i have different opinions on different days of the week well one of the things that worries me in in uh in the spirit of being humble that our particular kind of intelligence is not very special so there's all kinds of different intelligences and even more broadly there could be many different kinds of life yes so the basic definition and i just had i think somebody that you know sarah walker i just had a very long conversation with her about even just the very basic question of trying to define what is life from a physics perspective yeah even that question within itself i think one of the most fundamental questions in science and physics and everything is just trying to get a hold trying to get some universal laws around the ideas of what is life because that kind of unlocks a bunch of things around life intelligence consciousness all those kinds of things i agree with you in a sense but i think that's a dangerous question because the the answer can't be any more precise than the question and the uh the the question what is life kind of assumes that we have a definition of life and that it's a natural phenomena that that can be distinguished but that really there are edge cases like viruses and uh some people would like to say that uh electrons have consciousness and they you know so you can't if you really have fuzzy concepts it's uh it's very hard to to reach precise kinds of scientific answers but i think there's a very fruitful question that's adjacent to it which is has been pursued in different forms for quite a while and is now becoming very sophisticated in reaching in new directions and that is what are the states of matter that are possible you know so in high school or grade school you learn about solid solids liquids and gases but that really just scratches the surface of different ways that are distinguishable that matter can form into uh macroscopically different meaningful patterns that we call phases and then there are precise definitions of what we mean by phases of matter but then uh and that have been worked out fruitful over the decades and we're discovering new states of matter all the time and kind of having to work at what we mean by matter we're discovering the capabilities of matter to organize in interesting ways and uh some of them like liquid crystals are important ingredients of life our cell membranes are liquid crystals and that's very important to the way they work recently there's been a development in where we're talking about uh states of matter that not only not that are not static but that have dynamics that have that uh have characteristic patterns not only in space but in time these are called time crystals and that's that's been a development that's just in the last decade or so it's really really flourishing uh and so uh is there a state of matter that cause or group of states of matter that corresponds to life uh maybe but but the answer can't be any more definite than the question so i mean i i got to push back on the the the quite those are just words i mean i i i disagree with you the the the question points to a direction the answer might be able to be to be more precise than the question because because uh just as you're saying there there's uh that we could be discovering certain characteristics and patterns that are associated with a certain type of matter macroscopically speaking and that that we can then uh be able to post facto say this is let's sign the word life well kind of matter i agree with that completely that that's that's uh but that's so it's not a disagreement it's very frequent in physics that where in science that uh words that are in common use gets get refined and reprocessed into scientific terms that's happened for things like force and energy uh and so we've in a way we we find out what the useful definition is uh or symmetry for instance and the common usage may be quite different from the scientific usage but the scientific usage is special and takes on a life of its own and we find out what the the useful version of it is uh what the the fruitful version of it is so i do think so in that spirit i think if we uh can identify states of matter that or linked states of matter that can carry on processes of uh self-reproduction and development and information processing we should say we we might be tempted to classify those as like things as life yeah well can i ask you about the craziest one which is uh the one we know maybe least about which is consciousness is it possible that there are certain kinds of matter would be able to classify as um conscious meaning like the so there's uh the pan cyclists right with the philosophers who kind of try to imply that uh all matter has some degree of consciousness and yeah you can almost construct like a physics of consciousness yes do you um again we're in such early days of this but nevertheless it seems useful to talk about is is there some sense from a physical perspective to make sense of consciousness again consciousness is uh imprecise a very imprecise word and loaded with uh connotations that i think we should we don't want to start a scientific analysis with that i don't think uh it's often been important in science to start with simple cases and work up uh consciousness i think what most people think of when you talk about consciousness is okay i'm what am i doing in the in the world this is my experience i have a rich experience rich inner life and experience of and uh where is that in the equations and i think that's a great question a great great question and actually i think i'm gearing up to spend part of the i mean to try to address that in coming years one version of asking that question just as you said now is what is the simplest yeah formulation of that to study i think i think i'm much more comfortable with the idea of studying self-awareness as opposed to consciousness because that that sort of gets rid of the mystical aura of the thing and self-awareness is uh in simple you know the i think uh contiguous at least with ideas about feedback so if you have a system that looks at its own state and responds to it that's a kind of self-awareness and more sophisticated versions could be like in information processing things computers that look into their own internal state and do something about it and i think that could also be done in neural nets this is called recurrent neural nets which are hard to understand and kind of a frontier of the the uh uh so i think understanding those and gradually building up a kind of uh profound ability to un to uh conceptualize different levels of self-awareness what do you have to not know and what do you have to know and when do you know that you don't know it or when do you know what do you think you know that you don't really know the the these uh i think uh clarifying those issues when we clarify those issues and get a rich theory around uh self-awareness i think the that will illuminate the questions about consciousness in a way that you know scratching your chin and talking about qualia and blah blah blah blah is never going to do well i also have a different approach to the whole thing so there's from a robotics perspective you can engineer things that exhibit yes qualities of consciousness without understanding well well the how things work and from that perspective you uh it's like a back door like enter through the psychology door precisely the car yeah i think we're on we're on the same wavelength here i think that and let me just add one comment which is uh i think we should try to understand consciousness as we experience it uh in in as in evolutionary terms and ask ourselves why why does it happen this thing seems useful why is it useful why is it useful i think we've got a conscious eye watch here interesting quest thank you siri okay yeah get back i'll get back to you later uh yeah uh um and i think what we're gonna i'm i'm morally certain that what's going to emerge from analyzing recurrent neural nets and robotic design and advanced computer design is that having this kind of looking at the internal state in a structured way that that doesn't look at everything as guys has it's encapsulated looks at highly processed information and very selective and makes choices without knowing how they're made there's so there'll also be an unconscious i think that that is going to be turn out to be really essential to doing efficient information processing and that's why it evolved because it's it's it's it's helpful in uh because brains come at a high cost yeah so there has to be there has to be a good why and there's a reason yeah they're rare in evolution uh you and uh big brains are rare in evolution and they they come at a big cost you mean if you you they they they have high metabolic demands uh they require you know very active lifestyle warm bloodedness and take away from the ability to support metabolism of digestion and so so it's it's uh it comes at a high cost it has to it has to pay back yeah i think it has a lot of value in social interaction so i actually i'm spending the rest of the day today and uh with uh our friends uh that are our legged friends in robotic form at boston dynamics and i think so my probably biggest passion is human robot interaction and it seems that consciousness from the perspective of the robot is very useful to improve the human robot interaction experience the first the display of consciousness but then to me there's a gray area between the display of consciousness and consciousness itself if you think of consciousness from an evolutionary perspective it seems like a useful tool in human communication so yes um it's certainly well whatever consciousness it will turn out to be i think uh addressing it through its use yes and working up from simple cases and also working up from engineering experience in trying to do efficient computation including efficient management of social interactions is going to really shed light on these questions as i said in a way that sort of musing abstractly about consciousness never would so as i mentioned i talked to sarah walker and first of all she says hi spoke very highly of you one of her concerns about physics and physicists and humans is that we may not fully understand the system that we're inside of meaning like there may be limits to the kind of physics we do in trying to understand the system of which we're part of so like the the observer is also the observed in in that sense it seems like the the um our tools of understanding the world i mean this is mostly centered around the questions of what is life trying to understand the patterns that uh that are characteristic of life and intelligence all those kinds of things um we we're not we're not using the right tools because we're in the system is there is there something that resonates with you there almost well yeah yes we do have we we have limitations of course uh in the amount of information we can process uh on the other hand we can get help from our silicon friends and we uh we can get help from all kinds of instruments that make up for for our perceptual deficits and uh we have to and we can use at a conceptual level we can use different kinds of concepts to address different kinds of questions so i'm not sure exactly what problem she's talking about it's a problem akin to an organism living on a in a 2g plane trying to understand a three-dimensional world well we can do that i mean you know we in fact we you know for practical purposes most of our experience is two-dimensional it's hard to move vertically and yet we've produced conceptually a three-dimensional symmetry and in fact four-dimensional space-time uh so you know by thinking in appropriate ways and using instruments and demand and getting consistent accounts and rich accounts we find out what concepts are uh uh uh necessary and uh i don't see any end in sight of the process or any uh show stoppers because let me give you an example i mean for instance uh uh qcd our theory of the strong interaction has nice equations which i helped to discover what's qcd quantum chromodynamics so it's our theory of the strong interaction the interaction that is responsible for nuclear physics so it's the interaction that governs how quarks and gluons interact with each other and make make protons and neutrons and all the strong the related particles and among many things in physics it's one of the four basic forces of nature as we presently understand it uh and uh so we have beautiful equations which we can test in very special circumstances uh uh using at high high energies at accelerator so we're certain that these equations are correct you know prizes are given for it and so people try to knock it down and they can't and yeah they they the they uh uh but uh but the situations in which you can calculate the consequences of these equations are very limited so for instance no one has been able to demonstrate that this theory which is built on quarks and gluons which no one that which you don't observe actually produces protons and neutrons and the things you do observe this is called the problem of confinement so no one's been able to prove that analytically in a way that a human can understand on the other hand we can take these equations to a computer to gigantic computers and compute and by god you get the world from it the so these equations in a way that we don't understand in terms of human concepts we cut we we can't do the calculations but our machines can do them so with the help of what i like to call our silicon friends and their their descendants in the future we can understand in a different way that allows us to understand more but i don't think we'll ever no no human is ever going to be able to calculus solve those equations in the same way so so but but i think that's you know when we find limitations to our natural abilities we can try to find works or workarounds and sometimes that's appropriate concepts sometimes it's appropriate instruments sometimes it's a combination of the two but i think uh it's premature to get defeatist about it i don't see anything i don't see any uh any logical contradiction or paradox or limitation that that will bring this process to a halt well i think the idea is to continue thinking outside the box in different directions meaning just like how the math allows us to think of multiple dimensions outside of our perception system uh sort of thinking uh um you know coming up with new tools of mathematics or computation or all those kinds of things to to to to take different perspectives on our universe well i'm all for that you know and i i kind of have even elevated it into a principle which is of complementarity following boar that you need different ways of thinking even about the same things in order to do justice to their reality and answer different kinds of questions about them i mean we've several times alluded to the fact that human beings are hard to understand and the concepts that you use to understand human beings if you want to prescribe drugs for them or see what's going to happen if if they move very fast or get ex or are exposed to radiation and so that requires one kind of thinking that's very physical uh based based on the fact that the materials that we're made out of on the other hand if you want to understand how a person's going to behave in a different kind of situation you need entirely different concepts from psychology and there's nothing wrong with that you can have different ways of addressing the same material that are useful for different purposes right can you describe this idea which is fascinating of complementarity a little bit sort of uh first of all what uh state is the principle what is it and second of all what are good examples starting from quantum mechanics you used to mention psychology let's talk about this more it's like one in your new book one of the most fascinating ideas actually i think it's a wonderful yeah it's it's sort of to me it's it's well it's the culminating chapter of the book and i think uh since the whole book is about the big lessons or big takeaways from profound understanding of the physical world that we've understood that we've achieved uh including that it's mysterious in some ways the uh this was the the the final overarching uh lesson complementarity and uh it's a approach it's so unlike some of these other things which are just facts about the world like the world is both big and small and different sessions is this and is is big but we're not small think the things we talked about earlier uh and the fact that the universe is comprehensible and how complexity could emerge from simplicity and those things are uh in some in the broad sense facts about the world complementarity is more an attitude towards the world encouraged by the facts about the world and uh it's the idea the concept of the approach that or the realization that uh it can be appropriate and useful and inevitable and unavoidable to use very different descriptions of the same object or the same system or the same situation to answer different kinds of questions that may be very different and even uh mutually uninterpretable immutably uh incomprehensible uh but both correct somehow but both correct and sources of different kinds of insight which is so weird yeah well but it seems to work in so many cases it works in many cases and i think it's uh it's a deep fact about the world and how we should approach it its most rigorous form where it's actually a theorem if quantum mechanics is correct occurs in quantum mechanics where the primary description of the world is in terms of wave functions but let's not talk about the world let's just talk about a a particle an electron okay it's it's it's the primary description of that electron is its wave function and the wave function can be used to predict where it's going to be with different if you observe with it'll be in different places with different probabilities or how fast it's moving and it will also be moving in different ways with different probabilities that's what quantum mechanics says and you can predict either set of probabilities if you what's going to happen if i make an observation of the position or the velocity but so the wave function gives you ways of doing both of those but to do it to get those predictions you have to process the wave function in different ways you process it one way for position and in a different way for momentum and those ways are mathematically incompatible it's like you know it's like you have a stone and you can sculpt it into a venus de milo or you can sculpt it into david but you can't do both you can uh and uh and that's an example of complementarity but to answer different kinds of questions you have to analyze the system in different ways that are mutually incompatible but both valid to answer different kinds of questions so in that case it's a theorem but i think it's a much more widespread phenomena that applies to many cases where we can't prove it as a theorem but uh it's a piece of wisdom if you like and then appears to be a a very important insight do you uh and if you ignore it you can get very confused and uh misguided do you think this is um a useful hack for ideas that we don't fully understand or is this somehow a fundamental property of all or many ideas that you can take multiple perspectives and they're both true well i think it's both those both the answer to all questions yes that's right it's not either or it's both it's paralyzing to think that that we live in a world that's fundamentally like surrounded by complementary ideas like uh because it uh we want universe we somehow want to attach ourselves to absolute truths and absolute truths certainly don't like the idea of complementarity yes einstein was very uncomfortable with complementarity and in a broad sense the famous poor einstein debates revolves around this question of whether the complementarity that is a foundational feature of quantum mechanics as we have it was is uh a permanent feature of of the universe and that's our description of nature and so far quantum mechanics wins and it's gone from triumph to triumph whether complementarity is rock bottom i guess we're you know you can never be sure i mean but but uh it looks awfully good and it's been very successful and certainly its complementarity has been extremely useful and fruitful in in that domain uh including you know one of some of einstein's attempts to challenge it with like the famous einstein podolsky rosen experiment turned out to be confirmations of that that uh have have been uh useful in themselves but so thinking about these things was fruitful but not in the way that einstein hoped the the uh yeah so so as i said in in the case of uh quantum mechanics and this dilemma or dichotomy between processing the wave function in different ways it's a theorem they're mutually incompatible and that the physical correlate of that is the heisenberg certainty principle that you can't have position and momentum determined at once uh but uh in other cases like one that i like to talk like to think about is or like to point out as an example is is free will and determinism it's much less of a theorem and more more a uh more a a kind of uh way of thinking about things that i think is uh reassuring and avoids a lot of unnecessary quarreling and confusion the quarreling i'm okay with and the confusion i'm okay with i mean people debate about difficult ideas but the the question is whether it could be almost a fundamental truth i think it is a fundamental truth free will is both an illusion and not yes i think that's correct and i loaded the reason why people say quantum mechanics is weird and complementarity is is is a big part of that you know to say that the our actual whole world is weird the whole hierarchy of the universe is weird in this kind of particular way and it's it's quite profound but it's also um humbling because it's like we're we're never going to be on sturdy ground in the way that humans like to be it's like you have to embrace that uh well this this this whole thing is is uh like unsteady mess it's one of it's one of many lessons in humility that that we uh run into in profound understanding of the world i mean uh the copernican revolution was one that's that the earth is not the center of the universe uh darwinian evolution is another that uh humans are not the pinnacle of uh of uh you know of of god's creation uh the the uh uh and the uh apparent result of uh uh deep understanding of physical reality that the mind emerges from matter and human there's you know there's there's no uh no call on special life forces or souls uh these are all lessons in humility and i actually find complementarity a uh a liberating concept it's it's a okay you know yeah it is in a way uh that is what i remember there's a there's a story about dr johnson and he's talking with boswell and boswell was they were discussing a sermon that they both both heard and the the sort of culmination of of the sermon was the the the speaker saying i accept the universe and dr johnson said well he damn well better and and there's a certain uh there's a certain joy in accepting the universe because it's mind expanding and uh you know it and to me complementarity also suggests tolerance suggests opportunities for understanding different different understanding things in different ways that add add to rather than detract from uh understanding so uh i think it's it's an up it's an opportunity for mind expansion and demanding that there's only one way to think about things can be very limiting and the free will one that's a trippy one though i think to think like i am the decider of my own actions and at the same time i'm not is uh is tricky to think about but it's there does seem to be some kind of profound truth in that i get well i think it is tied up it will turn out to be tied up when we understand things better with these issues of self-awareness and i think so and where we get what what we perceive as making choices what does that really mean and what's going on under the hood and but i'm i'm speculating about a future understanding that's not in place at present your sense there will always be uh like as you dig into the self-awareness thing there'll always be some places where complementarity is going to show up oh definitely yeah i mean it will be uh how should i say there'll be kind of a god's eye view which sees everything that's going on in the computer or the the brain and then there's the brain's own view or the or the central processor or whatever it is that's the what we call the the the the self the consciousness that's all only aware of a very small part of it and those are very different those are the the so uh the god's eye view can be deterministic while the the the the self view sees free will and that's i i'm pretty sure that's how it's going to work out actually and but as it as it stands free will is a concept that we definitely at least i feel i definitely experience i can choose to do one thing than another and other people i think are sufficiently similar to me that i i trust that they feel the same way and it's an essential concept in psychology and law and so forth but uh at the same time i think that mind emerges from matter and that there's an alternative description of matter that's you know up to subtleties about quantum mechanics which i don't think are relevant here uh really is deterministic let me ask you about some particles okay first the absurd question almost like a question that like plato would ask what is the smallest thing in the universe as far as we know the the fundamental particles out of which we build our most successful description of nature are points they have zero they have don't have any internal structure that's they uh so that's as small as can be to uh so what does that mean operationally that means if you that they obey equations that describe entities that are singular concentrations of energy momentum angular momentum the things that particles have but localized at individual points now uh that mathematical structure is only revealed partially in the world because to to process the wave function in a way that that that accesses information about the precise position of things you have to apply a lot of energy and that's not you know we that's an idealization that you can apply infinite amount of energy to determine a precise position but at the mathematical level uh we build the world out of particles that are points so do they actually exist and what are we talking about so like oh they exist so let me ask sort of uh do quarks exist yes two electrons exist yes two photons exist yes but what does it mean for them to exist okay so well the hard answer to that the precise answer is that uh we construct the world out of equations that contain entities that uh are reproducible that exist in vast numbers throughout the universe that have definite properties of mass spin and a few others that we call electrons and the what what an electron is is defined by the equations that it satisfies theoretically and we find that there are many many exemplars of that of that entity in in the physical world so intellect in the case of electrons we can you know isolate them and study them in individual ones in great detail and we can check that they all actually are identical and that's why chemistry works and yes so so so that in that case uh it's very tangible similarly with photons you can study them individually they're the units of light uh and uh nowadays it's very practical to study individual photons and determine their uh their spin and their other basic properties and uh uh and check out the equations in great detail for quarks and gluons which are the other two main ingredients of uh our model of matter that's so successful uh it's a little more complicated because the quarks and gluons that appear in our equations don't appear directly as particles you can isolate and study individually they always occur within bound to what are called bound states or structures like protons a proton roughly speaking is composed of three quarks and a lot of gluons but we can detect them in a remarkably direct way actually nowadays whereas at relatively low energies uh the behavior of quarks is complicated at high energies they can prop they can propagate through space relatively freely for a while and we can see their tracks so ultimately they get recaptured into protons and other mesons and funny things but for a short time they propagate freely and while that happens we can take snapshots and see see their manifestations uh this is the actually this kind of thing is exactly what i got the nobel prize for predicting that this would work and similarly for gluons although you can't uh you can't isolate them as individual particles and study them in the same way we study electrons say uh you can use them to as use them theoretically as entities out of which you build tangible description tangible things that we actually do observe uh but also you can uh at accelerators at high energy you can liberate them for brief periods of time and study wow and and get convincing evidence that they they they leave tracks and then you can get convincing evidence that they were there and and have the properties that that we wanted them to have can we talk about asymptotic freedom this very idea that you won the nobel prize for yeah so it describes a very weird effect to me uh the the weird in the following way so the the the you know the way i think of most forces or interactions the closer you are the stronger the effect the the stronger the force yeah right with with quarks uh the closer they are the the less so the strong interaction and in fact they basically act like free particles when they're very close that's right yes well but this requires a huge amount of energy like can you describe me um why how does this even work how weird it is proper description must bring in uh quantum mechanics and relativity and it's uh so a proper description and equations so a proper description really is is probably uh more more more than we have time for and then uh we require quite a bit of patience on your part but uh how does relativity come into play wait wait relativity is important because when when we talk about trying to think about short distances we have to think about very large momenta and very large moment are connected to very large energy in relativity and so the connection between how things behave at short distances and how things behave at high energy uh really is connected through relativity in sort of a slightly backhanded way quantum mechanics indicates that short to get to analyze short distances uh you need to bring in probes that carry a lot of momentum this again is related to uncertainty because uh it's the fact that you have to bring in a lot of momentum that interferes with the possibility of determining position and momentum at the same time if you want to determine position you have to use instruments that bring in a lot of momentum and because of that those same instruments can't also measure momentum because they're disturbing the momentum and then the momentum brings in energy and yeah so so that there's also the effect that asymptotic freedom comes from uh the possibility of spontaneously making uh quarks and gluons for short amounts of time that that fluctuate into existence and out of existence uh and uh the fact that that can be done with a very little amount of energy and and uncertainty and energy translates into uncertainty in time so if you do that for a short time you can do that uh well it's all it comes in a package and you can you can so uh i told you it would take a while to really uh to really explain but the uh but but the results can be understood i mean we can state the results uh pretty simply i think so uh in everyday life we do encounter some forces that increase with distance and kind of turn off at short distances that's the way rubber bands work if you think about it or you if you pull them hard they they resist and but but they get flabby if if if the rubber band is not not pulled uh and so there are that can happen uh in the physical world but what's what's really difficult is to see how that could be a fundamental force that's consistent with everything else we know and that that's what asymptotic freedom is it says that uh there are particular there's a very particular kind of fundamental force that involves special particles called gluons with very special properties that uh enables that kind of behavior so ex there were experiments at the time we did our work there were experimental indications that quarks and gluons did have this kind of property but uh there were no equations that were capable of capturing it and we found the equations and showed how they work and showed how they that they were basically unique and this led to a complete theory of how the strong interaction works which is the quantum chromodynamics uh we mentioned earlier and so uh so that's the phenomenon that that quarks and gluons interact very very weakly when they're close together that's connected through relativity with the fact that they also interact very very weakly at high energies so if you have so at high energies the simplicity of the fundamental interaction gets revealed you know at the time we did our work the clues were very subtle but nowadays at hot at what are now high energy accelerators it's all obvious so we would have had a much well somebody would have had a much easier time 20 years later looking at the data you can sort of see the quarks and gluons as i mentioned they leave these short tracks that uh it would have been much much easier but but we from fundamental from indirect clues we were able to piece together enough to make that behavior a prediction rather than a post-diction right so it becomes obvious at high energies it becomes very obvious when when we first did this work it was uh frontiers of high energy physics and at big international conferences there would always be sessions on testing qcd and whether these whether this proposed description of the strong interaction was in fact correct and so forth and it was very exciting they were big but nowadays the same kind of work but much more precise with calculations to more accuracy and experiments that are much more uh precise and comparisons that are very precise uh now it's called calculating backgrounds because it's because people take this for granted and one of you and want to see deviations from the theory which would be which would be the new discoveries yeah the cutting edge becomes the foundation of foundation becomes boring yes uh uh is is there some for basic explanation purposes is there something to be said about uh strong interactions in the context of the the strong nuclear force for the for the attraction between protons yeah well the neutrons versus the the interaction between quarks within protons well quarks and gluons have the same relation basically to nuclear physics as electrons and photons have to atomic and molecular physics so atoms and photons are the dynamic entities that really come into play in chemistry and atomic physics of course you have to add the atomic nuclei but those are small and relatively inert really the dynamical part and you know for for most purposes of chemistry you just say you have this tiny little nucleus which this which qcd gives you don't worry about it it just it's there the real the real action is the electrons moving around and exchanging and things like that uh the uh but okay but we wanted to understand the nucleus too and uh so atoms base are sort of quantum mechanical clouds of electrons held together by electrical forces which is photons and then this radiation which is also another aspect of photons that's where all the fun happens is the electrons and the photons yeah that's right and the nuclei the nucleus are kind of the the uh well they're necessary they give the positive charge and most of the mass of matter but they don't since since they're so heavy they don't move very much in chemistry and uh uh i'm oversimplifying drastically they're not contributing much of the interaction and for most purposes in chemistry you can just idealize them as concentrations of positive mass and charge that that are uh you don't have to look inside but people are curious what what's inside what really and and uh that and that was a big thing on the agenda of 20th century physics starting in the 19 well starting with the 20th century and unfolding throughout of trying to understand what forces held the atomic nucleus together what it was and so uh anyway the the emerge the story that emerges from qcd is that very similar to the way that well broadly similar to the way that uh uh clouds of electrons held together by electrical forces uh give you atoms and ultimately molecules uh protons and neutrons are like atoms made now out of quarks quark clouds held together by gluons which are like like like the photons that that will give the electric forces but this is giving a different force the strong force and uh and the residual forces between protons and neutrons that uh are left over from their basic binding are like the residual forces between atoms that give molecules but in the case of protons and neutrons it gives you atomic nuclei so again for definitional purposes uh qcd quantum chromodynamics is basically the physics of strong interaction yeah we understand we now would unders which i think most physicists would would say it's the theory of quarks and gluons and how they interact but it's a very precise and i think it's fair to say very beautiful theory based on mathematical symmetry of a high order uh and another thing that's beautiful about it is that it's kind of in the same family as electrodynamics the conceptual structure of this of the equations are very similar they're based on having particles that respond to charge in a very symmetric way in the case of electrodynamics it's photons that respond to electric charge in the case of quantum chromodynamics there are three kinds of charge that we call colors but they're nothing like colors they really are like different kinds of charge but they rhyme with the same kind of uh like it's similar kind of dynamics similar kind of dynamics i call i say i like to say that qcd is like qed on steroids and instead of one photon you have eight gluons instead of one charge you have three color charges but there's a strong family resemblance but the context in which uh qcd does its thing is it's it's much higher energies like that's where it comes to wealth it's a stronger force so that to access how it's works and kind of pry things apart you have to inject more energy and so that that gives us um in some sense a hint of uh how things were in the earlier universe yeah well in that regard asymptotic freedom is a tremendous blessing because it means things get simpler at high energy and the universe was born free born free that's very very good yes chris was born so so in atomic physics i mean a similar thing happens in the theory of stars stars are hot enough that uh the interactions between electrons and photons are they're they're liberated they don't form atoms anymore they make a plasma which in some ways is simpler to understand you don't have complicated chemistry and in the early universe according to qcd similarly atomic nuclei dissolved into the constituent quarks and gluons which are moving around very fast and interacting in relatively simple ways and so this uh this opened up the early universe to scientific calculation can i ask you about some other weird particles that make up our universe what are axions and what is the strong cp problem okay so uh let me start with what the strong cp problem is uh first of all well charge con c is charge conjugation which is the transformation uh the notional transformation if you like that changes all particles into their anti-particles and the concept of seek symmetry charge conjugation symmetry is that if you do that you find the same laws would work so the laws are symmetric if the behavior that particles exhibit is the same as the part as the behavior you get with all their anti-particles uh then p is parity which is uh also called spatial inversion it's basically looking at a mirror universe and saying that the laws that are obeyed in a mirror universe when you look the the mirror images obey the same laws as the as the sources of their images there's no way of telling left right for instance that the laws don't distinguish between left and right uh now in the mid 20th century people discovered that both of those are not quite true that really the the equation that the mirror universe this the universe that's that you see in a mirror is not going to obey the same laws as the as the the universe that that that we actually exhib uh and interpret you could you would be able to tell if you did the right kind of experiments which was the mirror and which was the real thing uh anyway that that's the parody and they show that doesn't necessarily hold it doesn't quite hold and that that oh that and examining uh what the exceptions are turned out to be to lead to all kinds of insight about the nature of fundamental interactions especially properties of neutrinos and the weak interaction it's a long story but it's a very it's a so you just define the c and the p the conjugation the charge conjugation now that i've done that i want to what's the problem shove them off okay great because it's easier to talk about t which is time reversal symmetry we have very good reasons to think uh cpt is a an accurate symmetry of nature it's on the same level as relativity and quantum mechanics basically so that better be true uh so it's symmetric when you when you do conjugation parity in time and time and space reversal if you do all three then you get the same physical consequences now so but that means that cp is equivalent to t but but what's observed in the world is that t is not quite an accurate symmetry of nature either so most phenomena uh of at the fundamental level so interactions among elementary particles and the basic gravitational interaction uh if you ran them backwards in time you'd get the same laws so if ag again going unless this time we don't talk about a a mirror but we talk about a movie if you take a movie and then run it backwards that's the time reversal uh it's good to think about a mirror in time yeah it's like a mirror in time if you uh if you run run the movie backwards it would look very strange if you were looking at complicated objects and uh you know a charlie chaplin movie or whatever they it would look very strange if you ran it backwards in time but at the level of basic interactions if you were able to look at the atoms and the and the quarks involved they would obey the same laws they do a very good approximation but not exactly so you this is not exactly that means you could tell you could tell but you'd have to do very very subtle experiments with at high energy accelerators to take a movie that looked different when you ran it backwards this was a discovery by uh two great physicists named cronin and jim cronin and val fitch in the uh in the mid-1960s previous to that over all the centuries of development of physics with all this precise laws they did seem to have this gratuitous property that they look the same if you run the equations backwards it's kind of an embarrassing property actually because life isn't like that so empirical reality does not have this imagery in any obvious way and yet the laws did it's almost like the laws of physics are missing something fundamental about life if if if it holds that property right well i mean that's that's the embarrassing nature it's it's yeah it's well people worked hard and at what's this was a problem that's thought to belong to the foundations of statistical mechanics or the foundations of thermodynamics to understand how behavior which is grossly not symmetric with respect to reversing the direction of time in large objects how that can emerge from equations which are symmetric with respect to changing the direction of time to a very good approximation and that's that's still an interesting endeavor that's that's that's interesting and uh actually it's an exciting frontier of physics now to sort of explore the boundary between when that's true and when it's not true when you get to smaller objects uh and exceptions like time crystals or uh i definitely have to ask if i'll time crystals in a second here but so the cp problem and t so there's lost all of these we're in danger of infinite regress but we'll convert soon so can't possibly be turtles all the way down we're going to get to the bottom turtle so so so it became so it it got to be a real i mean it's a really puzzling thing uh why the laws should have this very odd property that we don't need and in fact it's kind of an embarrassment in addressing empirical reality but it seemed to be almost it seemed to be exactly true for a long time and then uh almost true and and in way almost true was even is more disturbing than exactly true because exactly true it could have been just a fundamental feature of the world and you know at some level you just have to take it as it is and if it's if it's a beautiful easily articulatable regularity you could say that okay that's a that's fine as a fundamental law of nature but to say that it's approximately true but not exactly that's that's that's right that's weird so uh and then so there was great progress in uh the late part of the 20th century uh in getting to an understanding of fundamental interactions in general that shed light on this issue uh it turns out that the prince basic principles of relativity and quantum mechanics plus the kind of high degree of symmetry that we found the so-called gage symmetry that characterizes the fundamental interactions when you put all that together it's a very very constraining framework and it has some indirect consequences because the possible interactions are so constrained and one of the indirect consequences is that the possibilities for violating the symmetry between forwards and backwards in time are very limited there are basically only two and one of them occurs and leads to a very rich theory that explains the cronin fish experiment and a lot of things that have been done subsequently has been used to make all kinds of successful predictions so that's that's turned out to be a very rich interaction it's esoteric and the effects are only show up at accelerators and are small and so on but they might have been very important in the early universe and lead to them be connected to the asymmetry between matter and anti-matter in the present universe and so but that's a that's another digression the the point is that uh that was fine that was a triumph to say that there was one possible kind of interaction that would violate time reversal symmetry and sure enough there it is and but the other kind doesn't occur so we still got a problem why doesn't it occur uh so but we're so we're close to really finally understanding this profound gratuitous feature of the world that is almost but not quite symmetric under reversing the direction of time but but not quite there and to get to understand that last bit is a challenging frontier of physics today and we have a promising proposal for how it works which is a kind of theory of evolution so there's this possible interaction which we call a coupling and there's a numerical quantity that tells us how strong that is and traditionally in physics we think of these kinds of numerical quantities as constants of nature that you just have to put them in right from experiment uh they have a certain value and that that's it and you know who am i to question what god do they just can't well they seem to be just constantly uh but in this case it's been fruitful to think and work out a theory where that strength of interaction [Music] is actually not a constant it's a fun it's a field it's a uh it's a fields are the fundamental ingredients of modern physics like there's an electron field there's a photon field which is also called the electromagnetic field and so every all of these particles are manifestations of different fields and uh there could be a field something that depends on space and time so a dynamical entity instead of just a constant here and if you do things in a nice way that's very symmetric very much suggested aesthetically by the theory uh but but the theory we do have then you find that you get a field which as it evolves from the early universe settles down to a value that's just right to make the laws very nearly exact invariant or symmetric with respect to reversal of time it might appear as a constant but it's actually a field that evolved over time it evolved over time okay but when you examine this proposal in detail you find that it hasn't quite settled down to exactly zero there it's still the the field is still moving around a little bit and because the motion is so uh the motion is so difficult the the material is so rigid and this material that fills all the field that fills those spaces so rich even small amounts of motion can involve lots of energy and that and that energy takes the form of uh particles fields of fields that are in motion are always associated with particles and those are the axions and if you calculate how much energy is in these residual oscillations these this axion gas that fills all the universe if this fundamental theory is correct you get just the right amount to make the dark matter that astronomers want and it has just the right properties so i'd love to believe that so that might be a thing that unlocks uh might be the key to understanding dark matter yeah i'd like to think so and many many physicists are coming around to this point of view which i've been a voice in the wilderness i was a voice in the wilderness for a long time but now now it's become very popular maybe even dominant so almost like so this axion particle slash field would be the thing that explains dark matter it explained yeah would solve this fundamental question of finally of why the laws are almost but not quite exactly the same if you run them backwards in time and and then seemingly in a totally different conceptual universe it would also uh provide unders give us an understanding of of the dark matter that's not what it was designed for and the theory wasn't wasn't proposed with that in mind but when you work out the equations that's what you get that's always a good sign yeah actually uh i i think i vaguely read uh somewhere that there may be early experimental validation of uh uh of axion is that uh am i am i reading the wrong well there have been quite a few false alarms and i think there are some of them still i mean people desperately want to find this thing and uh but i don't think i i i don't think any of them are convincing at this point but there are very ambitious experiments and kind of new you have to design new kinds of antennas that are capable of detecting these predicted particles and it's it's very difficult they interact very very weakly if it were easy it would have been done already but but i think there's good hope that we can get down to the required sensitivity and actually test whether these ideas are right [Music] in coming years or maybe decades and then understand one of the big mysteries like literally big in terms of uh its fraction of the universe is dark matter yes let me ask you about you mentioned a few times time crystals yeah um what are they these things are it's a very beautiful idea when we start to um treat space and time as a similar frameworks yes right physical phenomena right that's what motivated it what are first of all what are crystals yeah and what time crystals okay so crystals are orderly arrangements of uh atoms in space and many materials if you cool them down gently will form crystals and so we say that that's uh a spun a state of matter that forms spontaneously and uh an important feature of that state of matter is that the end result the crystal uh has less symmetry than the equations that give rise to the crystal so the equations the basic equations of physics are the same if you uh move a little bit so you can move they're homogeneous but crystals aren't the atoms are in particular place so though they have less symmetry uh and time crystals are the same thing in time basically you but of course it's not so it's not positions of atoms but it's ordering uh orderly behavior uh that certain states of matter uh will arrange themselves into spontaneously if you do them if you if you treat them gently and let them do what they want to do but indeed repeat in that same way indefinitely that's the crystalline form you can also have uh time liquids or you can have all kinds of other states of matter you don't have space-time crystals where the pattern only repeats if uh with each step of time you also move at a certain a certain direction in space so so yeah so but it's so it's basically it's states of matter that uh oh base that display structure in time spontaneously so here's here's the difference when it happens in time uh it sure looks a lot like it's motion and if it repeats indefinitely it sure looks a lot like perpetual motion yeah like uh looks like free lunch i was told that there's no such thing as free lunch does does this violate laws of thermodynamics uh no but it requires a critical examination of the laws of thermodynamics i mean let me let me say on background that the laws of thermodynamics are not the not fundamental laws of physics there are things we prove under certain circumstances emerge from the fundamental laws of physics right they're not we don't posit them separately they're meant to be deduced and they can be deduced under limited circumstances but not necessarily universally and we found finding some of the subtleties and sort of accept edge cases uh where they don't apply in a straightforward way and this is one uh so time crystals do obey do have this structure in time but it's not a free lunch because although in a sense things are moving uh they're they're already doing what they want to do they're in there so if if you want to extract energy from it you're going to be foiled because there's no spare energy there you uh it's or so you you can add energy to it and kind of disturb it but but you can't extract energy from this motion because it's gonna it wants to do that's the lowest energy configuration that there is so you can you can't get further energy out of it so in theory i guess perpetual motion uh you would be able to extract energy from it yeah if such a thing was to be created you could then milk it for energy well what's usually meant in the literature of perpetual motion is a kind of macroscopic motion that you could extract energy from and and somehow it would crank back up right that's that's not the case here if you want to extract energy uh this motion is is not something you can extract energy from if you intervene in the behavior you can uh change it but only by injecting energy not not by taking away energy you mentioned that a theory of everything may be quite difficult to come by a theory of everything broadly defined meaning like truly a theory of everything but let's look at a more narrow theory of everything which is that what the way it's used in often in physics is a a theory that unifies our current uh laws of physics general relativity quantum field theory df thoughts on this dream of a of a theory of everything in physics how close are we is there any promising ideas out there in your view well it would be nice to have it would be aesthetically pleasing uh will be useful no probably not well i'm i shouldn't no it's dangerous to say that but uh probably not i think we not not in certainly not in the uh foreseeable future uh maybe to understand black holes yeah but that's that's yes maybe to understand black holes but that's not useful and and well not only i mean only to understand it's it's it's worse of course you know it's not useful in the sense that we're not going to be basing any technology any time soon on black holes but it's it's more severe than that i would say it's that the kinds of questions about black holes that we can't answer within the framework of existing theory are ones that are not going to be susceptible to astronomical observation in the foreseeable future they're questions about very very small black holes when when quantum effects come into play or uh so that black holes are you know not not black holes they're they're they're they're emitting hawk this discovery of hawking called hawking radiation which for astronomical black holes is a tiny tiny effect that's no one have no one has ever observed it's a prediction that's never been changed like supermassive black holes that doesn't apply no no the the predicted rate of radiation from those black holes is so tiny that it's absolutely unobservable and is overwhelmed by all kinds of other effects uh so uh so it's not practical in the sense of technology it's not even practical in the sense of uh application to astronomy we our existing theory of uh general relativity and quantum theory and our theory of the the different fundamental forces is perfectly adequate to all prep all problems of technology for sure and almost all problems of astrophysics and cosmology that appear except with the with the notable exception of the extremely early universe if you want to ask what happened before the big bang or what happened right at the big bang which would be a great thing to understand of course uh yes we don't but but what about the engineering question so if we look at space travel so uh i think you've spoken with him uh eric weinstein really um uh you know he says things like we want to get off this planet his intuition is almost a motivator for the engineering project of space exploration in order for us to crack this problem of becoming a multi-planetary species we have to solve the physics problem his intuition is like if we figure out this what he calls the source code which is like like like like a theory of everything might give us clues on how to start hacking the fabric of reality like getting shortcuts right it might i can't say that you know i can't say that it won't but i can say that in the 1970s and early 1980s we achieved huge steps in understanding matter qcd much better understanding of the weak interaction much under better understanding of quantum mechanics in general and it's had minimal uh minimal impact on time on rocket design unprecedented on rocket design on anything any technology whatsoever and now we're talking about much more esoteric things and since i don't know what they are i can't say for sure that they won't affect technology but i'm very very skeptical that they would affect technology the uh uh the because you know to access them you need to very exotic circumstances to make new kinds of particles with high energy you need accelerators that are you know it's very expensive and you don't produce many many of them and so forth you know it's just uh it's a pipe dream i think yeah about space exploration yes i'm not sure exactly what he has in mind and but uh to me uh it's more a problem of of something between biology and i think human bodies are not well adapted to space even mars or even you know which is the closest thing to a kind of human environment that we're going to find anywhere close by uh very very difficult to maintain humans on mars uh and gonna be you know very expensive and very you know very unstable and but i think the pros however uh if we take a broader view of what it means to bring human civilization outside of the earth if we're satisfied with you know sending minds out there that we can converse with and actuators and that that we can in uh uh manipulate and sensors that we can get feedback from i think that's that's where it's at and for sure i think that's so much so much more realistic and uh and i think that that's the long-term future of uh the space exploration it's not hauling human bodies all over the place and that's that's that's just silly but it's possible that it's human bodies um so like you said it's a biology problem what's possible is that um we extend human lifespan in some way just we have to look at a bigger picture it could be just like you're saying by sending robots with actuators and kind of extending the the our limbs but it could also be extending some aspect of our minds of information and it could be cyborgs it could be uh it could be no we're talking it could be you know it could it could be uh human brains or cells that realize something like human brain architecture uh within uh within artificial environments you know shells if you like that that are more adapted to the conditions of space and uh that yeah so that that's entirely man machine hybrids as well as sort of remote uh uh outposts that we can communicate with i think yeah i think those those will happen and uh yeah yeah to me there's some sense in which as opposed to understanding the physics of the the the the fundamental fabric of the universe i think getting to the physics of life the physics of intelligence the physics of consciousness will the physics of information uh that that that brings from which life emerges that will allow us to do space exploration yeah well i think physics in the larger sense has a lot to contribute here not the physics of finding fundamental new laws in the sense of uh you know another quark or axions even physics in the sense of you know physics has a lot of experience in analyzing complex situations and analyzing new states of matter and devising new kinds of instruments that do clever things we you know the the physics in that sense has enormous amounts to contribute to uh this kind of endeavor but i don't think that looking for a so-called theory of any everything has much to do with it at all what advice would you give to a young person today with a bit of fire in their eyes high school student college student thinking about what to do with their life maybe advice about career or bigger advice about life in general well first read fundamentals because there i've tried i've tried to to uh give some coherent uh deep advice that's the fundamentals ten keys to reality by train cool check so that's a good place available everywhere if you want to learn but i can tell you uh the uh is there an audiobook yes there is an audio book that's awesome yeah i think it's like i can give three pieces of wise advice that i think are generally applicable one is to cast a wide net to really look around and see what looks promising what catches your imagination uh and and promise yeah and those you have to balance those two things you can have things that catch your imagination but don't look promising in the sense that the questions aren't ripe or uh but and and things that you in part of what makes things uh attractive is that whether you thought you liked them or not is this if you can see that there's ferment and new ideas coming up that become that's attractive in itself so uh when i started out i thought i was and when i was an undergraduate i intended to study philosophy or questions of how mind emerges from matter but i thought that wasn't really right timing isn't right yeah the ripe was the timing wasn't right for the kind of mathematical thinking and conceptualization that i really enjoy and good at but uh so that that's one thing cast a wide net look around uh and that's that's a pretty easy thing to do today because because of the internet you can look you can look at all kinds of things you have to be careful though because there's a lot of crap also but uh you you know you you can sort of tell the difference if you if you do a little digging uh the the uh so don't don't don't settle on just you know what your thesis advisor tells you to do or what your teacher tells you to do look for yourself and and and get a sense of what what what seems promising uh not what seemed promising 10 years ago or the uh so that's one uh another thing is to is kind of complementary to that well they're all complimentary complementary to that uh is to read history and read the masters of the history of ideas and masters of ideas i benefited enormously from as as in early in my career from reading in physics einstein in the original and feynman's lectures as they were coming out and darwin you know these you can you can learn what it in galileo you can learn what it is to wrestle with difficult ideas and how great minds did that you can learn a lot about uh style how how to ex write your ideas up and express them in in clear ways and also just just a couple that with uh i also enjoy reading biographies and biographies yes similarly right like so it gives you the context the context of the human being that created those right and brings it down to earth in the sense that you know it was really human beings who did this it's not uh and and they made mistakes and yeah uh i also you know i also got inspiration from bertrand russell who's a big hero and h.g wells and yeah so uh read read the masters make contact with great minds and when you are sort of narrowing down on a subject learn about the history of the subject because that really puts in context what you're trying to do and and also gives a sense of community and grandeur to the whole enterprise uh and then the third piece of advice is complementary to both those which is sort of to uh to get the basics under control as soon as possible so if you want to do theoretical work in science you know you you you have to learn calculus multivariable calculus complex variables group theory nowadays you have to be highly computer literate uh if you want to do experimental work you also have to be computer literate then you have to learn about electronics and optics and instruments and so so get that under control as soon as possible because it's like learning a language uh to do to to produce great works and express yourself fluently and with confidence uh it should be your native language these things should be like your native language so you're not you're not wondering um what is a derivative this is just part of your you know part it's it's uh it's in your bones so to speak you know and the sooner that you can do that then the the better so those all those things can be done in parallel and should be you've accomplished some incredible things in your life but uh the sad thing about this thing we have is it ends uh do you um do you think about your mortality are you afraid of death uh well well afraid is the wrong way i mean uh let's define things i wish it weren't gonna happen and i'd like to but uh uh do you think about it i say occasionally i think about well i think about it very operationally in the sense that uh there's always a trade-off between exploration and exploitation this is a classic subject in computer science actually in machine learning uh that when you're in an unusual circumstance you you want to explore to see what what the landscape is and what the gathered data but then at some point you want to use that make decide make choices and say this is what i'm going to do and exploit the knowledge you've accumulated and uh the longer the period of exploitation you anticipate the more exploration you should do in new directions and so for me i've had to sort of adjust the balance of exploration and uh uh exploitation and that said you've explored quite a lot yeah well i i'm still i haven't shut off the exploitation at all i'm still hoping the exploration right i'm still hoping for 10 or 15 years of top flight performance but the uh several years ago now when i was 50 years old i i was at the institute for advanced study and my office was right under freeman dyson's office and we were kind of friendly and uh and you know he found out it was my my 50th birthday and said congratulations and uh you should feel liberated because no one expects much of a 50 year old theoretical physicist and he and he obviously had felt liberated by uh by by reaching a certain age and yeah there is something to that uh i fee you know i feel i don't have to catch i don't have to keep in touch with the latest hypertechnical developments in particle physics or string theory or so like uh because i'm not gonna i'm really not gonna be exploiting that i but i but but where i am exploring uh in these directions of machine learning and and things like that and and but then but i'm also concentrating within physics on exploiting directions that i've already established and the laws that we already have and doing things like uh i'm very actively involved in trying to design helping people experimentalists and uh engineers even to design antennas that are capable of detecting axions so there and that's there we're deep in the exploitation stage it's not a matter of finding the new laws but of really you know using the laws we have to to to kind of finish the story off so so it's complicated but but but but i'm you know i'm very happy with my life right now and uh i'm enjoying it and i don't want to cloud that by thinking too much that that it's uh going to come to an end you know it's a gift i didn't earn is there a good thing to say about why this gift that you've gotten and didn't deserve is so damn enjoyable so like what's the meaning of this thing of life to me interacting with people i love my family and i have a very wide circle of friends now and i'm trying to produce some institutions that will survive me as well as my as the work and and it's just it's how should i say it's a positive feedback work loop when you do something and if people appreciate it and and then you want to do more and they get rewarded and it's just uh how should i say this is another gift that i didn't earn and don't understand but i i have a dopamine system and uh yeah i'm happy to use it and it seems to get energized by uh by the creative process but yeah process inspiration very much so and all of that started from the little fluctuations [Laughter] shortly after the big bang frank well whatever the those initial conditions and fluctuation did that created you i'm glad they did this is uh thank you for all the work you've done for the many people you've inspired for the many of the billion most of your ideas were pretty useless of the bill several billions as it is for all humans but uh you had quite a few truly special ideas and uh thank you for bringing those to the world and thank you for wasting your valuable time with me today it's truly enough it's been a joy and i hope people uh enjoy it and and and i think you know the kind of mind expansion that i've enjoyed by interacting with physical reality at this deep level i think can be conveyed to and enjoyed by many many people and that's i that's one of my missions in life thanks for listening to this conversation with frank wilcheck and thank you to the information netsuite expressvpn blinkist and eight sleep check them out in the description to support this podcast and now let me leave you with some words from albert einstein nothing happens until something moves thanks for listening and hope to see you next time