Sean Carroll: The Nature of the Universe, Life, and Intelligence | Lex Fridman Podcast #26
the following is a conversation with Sean Carroll he's a theoretical physicist at Caltech specializing in quantum mechanics gravity and cosmology he's the author of several popular books one on the arrow of time called from eternity to here one on the Higgs boson called particle at the end of the universe and one on science of philosophy called the big picture on the origins of life meaning in the universe itself he has an upcoming book on quantum mechanics that you can pre-order now called something deeply hidden he writes one of my favorite blogs and his website preposterous universe com I recommend clicking on the greatest-hits link that lists accessible interesting posts on the arrow of time dark matter dark energy the Big Bang general relativity string theory quantum mechanics and the big meta questions about the philosophy of science God ethics politics academia and much much more finally and perhaps most famously he's the host of a podcast called mindscape that you should subscribe to and support on patreon along with the Joe Rogan experience Sam Harris is making sense and Dan Carlin's hardcore history sean's mindscape podcast is one of my favorite ways to learn new ideas or explore different perspectives and ideas that I thought I understood it was truly an honor to meet and spend a couple hours with Sean it's a bit heartbreaking to say that for the first time ever the audio recorder for this podcast died in the middle of our conversation there are technical reasons for this having to do with phantom power that I now understand and will avoid it took me one hour to notice and fix the problem so much like the universal 60 percent dark energy roughly the same amount in this conversation was lost except in the memories of the two people involved and in my notes I'm sure we'll talk again and continue this conversation on this podcast or on Shawn's and of course I look forward to it this is the artificial intelligence podcast if you enjoy it subscribe on YouTube iTunes supported on patreon or simply connect with me on Twitter at Lex Friedman and now here's my conversation with Sean Carroll what do you think is more interesting and impactful understanding how the universe works at a fundamental level or understanding how the human mind works you know of course this is a crazy meaningless unanswerable question in some sense because they're both very interesting and there's no absolute scale of interestingness that we can rate them on there's the glib answers that says the human brain is part of the universe right and therefore under saying the universe is more fundamental than understanding the human brain but do you really believe that once we understand the fundamental way the universe works at the particle level the forces we would be able to understand how the mind works no certainly not we cannot understand how ice cream works just from understanding how particles work right so a big believer in emergence I'm a big believer that there are different ways of talking about the world beyond just the most fundamental microscopic one you know when we talk about tables and chairs and planets and people we're not talking the language of particle physics and cosmology so but understanding the universe you didn't say just at the most fundamental level right so understanding the universe at all levels is part of that I do think you have to be a little bit more fair to the question there probably are general principles of complexity biology information processing memory knowledge creativity that go beyond just the human brain right and and maybe one could count understanding those as part of understanding the universe the human brain as far as we know is the most complex thing in the universe so there's it's certainly absurd to think that by understanding the fundamental laws of particle physics you get any direct insight on how the brain works but then there's this step from the fundamentals of particle physics to information processing yeah a lot of physicists and philosophers maybe a little bit carelessly take when they talk about artificial intelligence do you think of the universe as a kind of a computational device know to be like the honest answer there is no there's a sense in which the universe processes information clearly there's a sense in which the universe is like a computer clearly but in some sense I think I tried to say this once on my blog and no one agreed with me but the universe is more like a computation than a computer because the universe happens once a computer is a general-purpose machine right if you can ask it different questions even a pocket calculator right and it's set up to answer certain kinds of questions the universe isn't that so information processing happens in the universe but it's not what the universe is because I know your MIT colleagues that Lloyd feels very differently about this well you're thinking of the universe it's a closed system I am so what makes a computer more like a like a PC like a computing machine is that there's a human that everyone comes up to it and moves the mouse around yeah so input gives it input gives it input and your and that's why you're saying is just a computation a deterministic thing that's just unrolling but the immense complexity of it is nevertheless like processing there's a state and then it changes with good rule with rules and there's a sense for a lot of people that if the brain operates the human brain operates within that world then it's simply just a small subset of that and so there's no reason we can't build arbitrarily great intelligences yeah do you think of intelligence in this way intelligence is tricky I don't have a definition of it offhand so I remember this panel discussion that I saw on YouTube I wasn't there but Seth Lloyd was on the panel and so was Martin Rees the famous astrophysicist and Seth gave his shtick for why the universe is a computer and explained this and and and Martin we said so what is not a computer that's a good question I'm not sure because if you have a sufficiently broad definition of what a computer is then everything is right and the simile or the analogy gains force when it excludes some things you know is the moon going around the earth performing a computation I can come up with definitions in which the answer is yes but it's not a very useful computation I think that it's absolutely helpful to think about the universe in certain situations certain contexts as an information processing device I am even guilty of writing a paper called quantum circuit cosmology where we modeled the whole universe as a quantum circuit as a circuit as a circuit yeah and what you bits kind of with new bits basically right yeah so in cube it's becoming more and more entangled so what do you want to do want to digress a little bit this is kind of fun so here's a mystery about the universe that is so deep and profound that nobody talks about it space expands right and we talk about in a certain region of space a certain number of degrees of freedom a certain number of ways that the quantum fields and the particles in that region can arrange themselves that that number of degrees of freedom in a region of space is arguably finite we actually don't know how many there are but there's a very good argument it says it's a finite number so as the universe expands and space gets bigger are there more degrees of freedom if it's an infinite number it doesn't really matter infinity times two is still infinity but if it's a finite number then there's more space so there's more degrees of freedom so where did they come from that would mean the universe is not a closed system there's more degrees of freedom popping into existence so what we suggested was that there are more degrees of freedom and it's not that they're not there to start but they're not entangled to start so the universe that you and I know of zien over the three dimensions around us that we see we said those are the entangled degrees of freedom making up space-time and as the universe expands there's a whole bunch of qubits in their in their zero State that become entangled with the rest of space-time through the action of these quantum circuits so what does it mean that there's now more degrees of freedom as they become more integral yeah so this is the universe expands that's right so there's more and more degrees of freedom they're entangled that are playing part playing the role a part of the entangled space-time structure so the basic the underlying philosophy is that space-time itself arises from the entanglement of some fundamental quantum degrees of freedom Wow okay so at which point is most of the the the entanglement happening are we talking about close to the bing bang are we talking about throughout the the time right yeah so the idea is that at the Big Bang almost all the degrees of freedom that the universe could have were there but they were unentangled with anything else and that's a reflection of the fact that the Big Bang had a low entropy it was very simple very small place and as space expands more and more degrees of freedom become entangled with the rest of the world well I have to ask John Carroll what do you think of the thought experiment from Nick Bostrom that we're living in a simulation so I think let me contextualize that a little bit more I think people don't actually take this thought experiments I think it's quite interesting it's not very useful but it's quite interesting from the perspective of AI a lot of the learning that can be done usually happens in simulation from artificial examples and so it's a constructive question to ask how difficult is our real world to simulate right which is kind of a dual part of for living in a simulation and somebody built that simulation now how if you were to try to do it yourself how hard would it be so obviously we could be living a simulation if you just want the physical possibility then I completely agree that it's physically possible I don't think that we actually are so take this one piece of data into consideration you know we we live in a big universe okay there's two trillion galaxies in our observable universe with 200 billion stars in each galaxy etc it would seem to be a waste of resources to have a universe that big going on just to do a simulation so in other words I want to be a good Bayesian I want to ask under this hypothesis what do I expect to see so the first thing I would say is I wouldn't expect to see a universe that was that big okay the second thing is I wouldn't expect the resolution of the universe to be as good as it is so it's always possible that if they're superhuman simulators only have finite resources that they don't render the entire universe right that that the part that is out there that two trillion galaxies isn't actually being simulated fully okay but then the obvious extrapolation of that is that only I am being simulated fully like the rest of you are just part not non-player characters right I'm the only thing that is real the rest of you are just chatbots beyond this wall I see the wall but there is literally nothing on the other side of the wall that is sort of the Bayesian prediction that's what it would be like to do an efficient simulation of me so like none of that seems quite realistic there's that I don't see I hear the argument that it's just possible and easy to simulate lots of things I don't see any evidence from what we know about our universe that we look like a simulated universe now maybe you could say well we don't know what it would look like but that's just abandoning your Bayesian responsibilities like your your job is to say under this theory here's what you would expect to see yes certainly if you think about simulation is a thing that's like a video game where only a small subset is being rendered but say the entire all of the laws of physics it the entire closed system of the quote-unquote universe mm-hmm it had a creator yeah it's always possible all right so that's not useful to think about when you're thinking about physics the way Nick Bostrom phrases it if is if it's possible to simulate a universe eventually we'll do it right you could use that by the way for a lot of things well yeah but I guess the question is how hard is it to create a universe I wrote a little blog post about this and maybe maybe I'm missing something but there's an argument that says not only that it might be possible to simulate a universe but probably if you imagine that you actually attribute consciousness and agency to the little things that we're simulating to our little artificial beings there's probably a lot more of them than there are ordinary organic beings in the universe or there will be in the future right so there's an argument that not only is being a simulation possible it's probable because in the space of all living consciousness is most of them are being simulated right most of them are not at the top level I think that argument must be wrong because it follows from that argument that you know if we're simulated but we can also simulate other things well but if we can simulate other things they can simulate other things right if we give them enough power and resolution and ultimately we'll reach a bottom because the laws of physics in our universe have a bottom or made of atoms and so forth so there will be the cheapest possible simulations and if you believe the original argument you should conclude that we should be in the cheapest possible simulation because that's where most people are but we don't look like that doesn't look at all like we're at the edge of resolution you know there were 16-bit you know things but it's it seems much easier to make much lower level things that then we are so and also I questioned the whole approach to the anthropic principle that says we are typical observers in the universe I think that that's not actually I think that there's a lot of selection that we can do that we're typically in things we already know but not typical within all the universe so do you think there's intelligent life however you would like to define intelligent life out there in the universe my guess is that there is not intelligent life in the observable universe other than us simply on the basis of the the fact that the likely number of other intelligent species in the observable universe there's two likely numbers zero or billions and if there had been billions we would have noticed already - for there to be literally like a small number like you know Star Trek there's you know a dozen intelligent civilizations in our galaxy but not a billion that that's weird that that's sort of bizarre to me it's easy for me to imagine that there are zero others because there's just a big bottleneck to making multicellular life or logical life or whatever it's very hard for me to imagine that there's a whole bunch out there that have somehow remained hidden from us the question I'd like to ask is what would intelligent life look like the what I mean by that question in a war that's going is what if intelligent life is just fundamental it's in some very big ways different than our the one that has on earth that there's all kinds of intelligent life that operates in different scales of both size and temporal right that's a great possibility because I think we should be humble about what intelligence is what life is we don't even agree on what life is much less what intelligent life is right so that that's an argument for humility saying there could be intelligent life of a very different character right like you could imagine that dolphins are intelligent but never invent space travel because they live in the ocean and they don't have thumbs right so they never invent technology you never events melting maybe the universe is full of intelligent species that just don't make technology right that that's compatible with the data I think and and I think maybe maybe what you're pointing at is even more out there versions of intelligence you know intelligence in inter molecular clouds or on the surface of a neutron star or in between the galaxies and giant things where the equivalent of a heartbeat is 100 million years on the one hand yes we should be very open-minded about those things on the other hand we all all of us share the same laws of physics there might be something about the laws of physics even though we don't currently know exactly what that thing would be that makes meters and years the right length and time scales for intelligent life maybe not but you know we're made of atoms atoms have a certain size we orbit stars or stars have a certain lifetime it's not impossible to me that there's a sweet spot for intelligent life that we find ourselves in so I'm hoping mine didn't either way I won't mind either being humble and there's all sorts of different kinds of life or no there's a reason we just don't know it yet why life like ours is the kind of life that's out there yeah I'm of two minds too but I often wonder if our brains is just designed to quite obviously to operate and see the world in the unnies timescales and we're almost blind and and the tools we've created for detecting things are blind yeah to the kind of observation needed to see intelligent life or other skills well I'm totally open to that but so here's another argument I would make you know we have looked for intelligent life but we've looked at for it in the dumbest way we can rise by turning radio telescopes to the sky and why in the world would a super advanced civilization randomly beam out radio signals wastefully in all directions into the universe that just doesn't make any sense especially because in order to think that you would actually contact another civilization you would have to do it forever you have to keep doing it for millions of years that sounds like a waste of resources if you thought that there were other solar systems with planets around them where maybe intelligent life didn't yet exist but might someday you wouldn't try to talk to it with radio waves she would send a spacecraft out there and you would park it around there and it would be like from our point of view be like 2001 or there's an you know an monolith monolith so there could be an artifact in fact the other way works also right there could be artifacts in our solar system that are have been put there by other technologically advanced civilizations and that's how we will eventually contact them and we have just haven't explored the solar system well enough yet to find them the reason why we don't think about that is because we're young and impatient right like it would take more than my lifetime to actually send something to another star system and wait for it and then come back so but if if we start thinking on hundreds of thousands of years or million year timescales that's clearly the right thing to do are you excited by the thing that Elon Musk says don't pay sex in general space but the idea of space exploration even though your or your species is young and impatient ya know I do think that space travel is crucially important long term even to other star systems and I think that many people overestimate the difficulty because they say look if you travel 1% the speed of light to another star system will be dead before we get there right and I think that it's much easier and therefore when they write their science fiction stories they imagine we feel fast from the speed of light because otherwise they are too impatient right we're not gonna go faster than the speed of light but we could easily imagine that the human lifespan gets extended to thousands of years and once you do that then the stars are much closer effectively right and what's a hundred year trip right so I think that that's gonna be the future the far future not not my lifetime once again but baby steps and unless your lifetime gets extended well it's in a race against time right a friend of mine who actually thinks about these things said you know you and I are gonna die but I don't know about our grandchildren that's right that's it I don't know for predicting the future is hard but that's at least a plausible scenario and so ya know I think that as we discussed earlier there are threats to the earth known and unknown right having spread humanity and biology elsewhere is a really important long-term goal what kind of questions can science not currently answer but might soon when you think about the problems and the mysteries before us hmm that may be within reach of science I think an obvious one is the origin of life we don't know how that happened there's a difficulty in knowing how it happened historically actually you know literally on earth but starting life from non-life is something I kind of think we're close to right we really think so how like how difficult is it to start lie - well I I've talked to people including on the podcast about this you know life requires three things life as we know it so there's a difference with life which who knows what it is and life as we know it which we can talk about with some intelligence so life as we know it requires compartmentalization you need like a little membrane around your cell metabolism you take in food and eat it and let that make you do things and then replication okay so you need to have some information about you are that you passed down through to future generations in the lab compartmentalization seems pretty easy not hard to make lipid bilayers that come into a little cellular walls pretty easily metabolism and replication are hard but replication we're close to people have made RNA like molecules in the lab that I think the state of the art is they're not able to make one molecule that reproduces itself but they're able to make two molecules that reproduce each other yeah so that's okay that's pretty close metabolism is hard to believe it or not even though it's sort of the most obvious thing but you want some sort of controlled metabolism and the actual cellular machinery in our bodies is quite complicated it's hard to see it just popping into existence all by itself probably took a while but it's we're making progress and in fact I don't think we're spending nearly enough money on it if I were the NSF I would flood this area with money because it would change our view of the world if we could actually make life in the lab and understand how it was made originally here on earth and I'm sure have some ripple effects that help cure disease and so on I mean that just that ending so synthetic biology is a wonderful big frontier where we're making cells the right now the best way to do that is to borrow heavily from existing biology right where craig Venter several years ago created an artificial cell but all he did was not all he did it was a tremendous accomplishment but all he did was take out the DNA from a cell and put in an entirely new DNA and let it boot up and go hmm what about the leap to creating intelligent life on Earth yeah however again we define intelligence of course but let's just even say Homo sapiens the the modern the modern intelligence in our human brain you have a sense of what's involved in that leap and how big of a leap that is so AI would count in this or you really want life you want a really organism in some sense AI would count okay I yeah of course of course AI would come but well let's say artificial consciousness right so I do not think we are on the threshold of creating artificial consciousness I think it's possible I'm not again very educated about how close we are but my impression is not that we're really close because we understand how little how little we understand of consciousness and what it is so if we don't have any idea what it is it's hard to imagine we're on the threshold of making it ourselves but it's doable it's possible I don't see any obstacles in principle so yeah I would hold out some interest in that happening eventually I think in general consciousness I think we'll be just surprised how easy consciousness is once we create intelligence you know I think consciousness is the thing that that's just something we all fake well good no actually I like this idea that in fact consciousness is way less mysterious than we think yeah because we're all at every time at every moment less conscious than we think we are right we can fool things and I think that plus the idea that you not only have artificial intelligent systems but you put them in a body right give them a robot body that will help the faking a lot yeah I think I think creating consciousness in our artificial consciousness is as simple as asking a Roomba to say I'm conscious and refusing to be talked out of it could be it could be and I mean I'm almost being silly but that's what we do yeah that's what we do with each other this is the kind of that consciousness is also a social construct and a lot of our ideas of intelligence is a social construct and so reaching that bar involves something that's beyond that's not necessarily involve the fundamental understanding of how you go from electrons to neurons to cognition no I actually I think that is a really good point and in fact what it suggests is you know so yeah you referred to Kate Kate darling who I had on the podcast and who does these experiments with very simple robots but they look like animals and they can look like they're experiencing pain and we human beings react very negatively to these little robots looking like they're experiencing pain and what you want to say is yeah but they're just robots it's not really pain he's just some electrons going around but then you realize you know you and I are just electrons going around and that's what pain is also and so what I what I would have an easy time imagining is that there is a spectrum between these simple robots that Kate works with and a human being where there are things that sort of by some strict definition touring test level thing are not conscious but nevertheless walk and talk like they're conscious and it could be that the future is I mean Siri is close right and so it might be the future has a lot more agents like that and in fact rather than some day going aha we have consciousness will just creep up on it with more and more accurate reflections of what we expect and in the future maybe the present for example we haven't met before and you're made basically assuming that I'm human as it's a high probability at this time because the yeah but in the future there might be question marks on that right yeah no absolutely certainly videos are almost to the point where you shouldn't trust them already photos you can't trust right videos is easier to trust but we're getting worse that yeah we're getting better at faking them Yeah right getting better yeah so physical embodied people what's what's so hard about faking that so this is very depressing this conversation right so to me is excited you're doing it so exciting to you but it's a sobering thought we're very bad right yet imagining what the next 50 years are gonna be like when we're in the middle of a phase transition as who you are right now yeah and I in general I'm not blind to all the threats yeah I am excited by the power of technology to solve to protect us against the threats as they evolve I'm not as much as Steven Pinker optimistic about the world but in everything I've seen all the brilliant people in the world that I've met are good people so the army of the good in terms of the development of technology is large okay you're way more optimistic than I am I think that goodness and badness are equally distributed among intelligent and unintelligent people I don't see much of a correlation there interesting neither of us have proof yeah exactly is yeah again that pinions are freeze right nor definitions of good and evil we come without definitions or with without data opinions so what kind of questions concerns not currently answer may never be able to answer in your view well the obvious one is what is good and bad you know I know what is right and wrong I think that there are questions that you know science tells us what happens what the world is and what it does it doesn't say what the world should do or what we should do because we're part of the world but we are part of the world and we have the ability to feel like something's right something's wrong and to make a very long story very short I think that the idea of moral philosophy is systematizing our intuitions of what is right what is wrong and science might be able to predict ahead of time what we will do but it won't ever be able to judge whether we should have done it or not so you know you're kind of unique in terms of scientists listen it doesn't have to do with podcast but even just reaching out I think you referred to as sort of an doing interdisciplinary science so you reach out and talk to people that are outside of your discipline which I always hope that's what science was for in fact I was a little disillusioned when I realized that academia is very siloed yeah and so the question is how well at your own level how do you prepare for these conversations how do you think about these conversations how do you open your mind enough to have these conversations and it may be a little bit broader how can you advise other scientists to have these kinds of conversations not at the podcast so the fact that you're doing a podcast is awesome other people don't hear them yeah but it's also good to have it without mics right in general it's a good question but a tough one to answer I think about you know a guy knows a personal trainer and he was asked on a podcast how do we you know psych ourselves up to do a workout how do we make that discipline to go and work out he's like why you asking me like I can't stop working out like I don't need to psych myself up so and likewise you know he asked me like how do you get to like have inner discipline conversations and all sorts of different things all sorts of different people and like that's that's what makes me go right like that's I couldn't stop doing that I did that long before any of them were recorded in fact a lot of the motivation for starting recording it was making sure I would read all these books that I had purchased right like all these books I wanted to read not enough time to read them and now if I have motivation because I'm gonna you know interview Pat Churchland I'm gonna finally read her for her book you know and it's absolutely true that academia is extraordinarily siloed right we don't talk to people we rarely do and in fact when we do is punished you know like the people who do it successfully generally first became very successful within their little silo you have discipline and only then did they start expanding out if you're a young person you know I I have graduate students I try to be very very candid with them about this that it's you know most graduate students are to not become faculty members right it's a it's a tough road and so live the life you want to live but do it with your eyes open about what it does to your job chances and the more broad you are and the less time you spend hyper specializing in your field the lower your job chances are that's just an academic reality it's terrible I don't like it yeah but it's a reality and for some people that's fine like there's plenty of people who are wonderful scientists who have zero interest in branching out and talking to things to anyone outside their field but it is disillusioning to me some of the you know romantic notion I had the intellectual academic life is belied by the reality of it the idea that we should reach out beyond our discipline and that is a positive good is just so rare in universities that it may as well not exist at all but that said even though you're saying you're doing it like the personal trainer because you just can't help it you're also an inspiration to others like I could speak for myself you know I also have a career I'm thinking about right now and without your podcast I may not have been doing this at all right so it makes me realize that these kinds of conversations is kind of what science is about in many ways what the reason we write papers this exchange of ideas is it's much harder to do interdisciplinary papers I would say yeah that's right and conversations are easier so conversations is a beginning and in the field of AI that's in - it's it's obvious that we should think outside of pure computer vision competitions and a particular data sets which should think about the broader impact of how this can be you know you know the reaching out the physics the psychology to neuroscience and having these conversations so that you're an inspiration and so well thank you never sweet but never know how the world changes I mean the the fact that this stuff is out there and I've a huge number of people come up to me a grad students really loving the podcast inspired by it and they will probably have that there'll be ripple effects when they become faculty and so on so we can end on a balance between pessimism and optimism and Shawn thank you so much for talking it was awesome no Lex thank you very much for this conversation was great you