Peter Woit: Theories of Everything & Why String Theory is Not Even Wrong | Lex Fridman Podcast #246
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Peter Woit is a theoretical physicist, mathematician, critic of string theory, and author of the popular science blog Not Even Wrong. Please support this podcast by checking out our sponsors:
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EPISODE LINKS:
Peter's website: http://www.math.columbia.edu/~woit/
Peter's blog: https://bit.ly/3xCwm9F
Not Even Wrong (book): https://amzn.to/3peDzZs
Quantum Theory, Groups, and Representations (book): https://amzn.to/316iAjf
Love and Math (book): https://amzn.to/3If7B8m
The Second Creation (book): https://amzn.to/3rlWzIu

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OUTLINE:
0:00 - Introduction
0:23 - Physics vs mathematics
14:52 - Beauty of mathematics
36:43 - String theory
1:05:16 - Theory of everything
1:25:24 - Twistor theory and spinors
1:41:51 - Nobel Prize likelihood for theory of everything
1:45:37 - Simulating physics
1:49:08 - Sci-Fi, aliens and space
1:58:20 - Responsibility of scientists

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 The following is a conversation with Peter White, a theoretical physicist at Columbia, outspoken critical string theory, and the author of the popular physics and mathematics blog called Not Even Wrong. This is the Lex Friedman podcast. To support it, please check out our sponsors in the description. And now, here's my conversation with Peter White. You're both a physicist and a mathematician. So let me ask, what is the difference between physics and mathematics? Well, there's kind of a conventional understanding of the subject that they're two quite different things. So that mathematics is about making rigorous statements about these abstract things, things of mathematics and proving them rigorously. And physics is about doing experiments and testing various models and that. But I think the more interesting thing is that there's a wide variety of what people do as mathematics, what they do as physics, and there's a significant overlap. And that I think is actually a much, much very, very interesting area. And if you go back kind of far enough in history and look at figures like Newton or something, I mean, at that point, you can't really tell it was Newton, a physicist or a mathematician. The mathematicians will tell you he was a mathematician, the physicists will tell you he was a physicist. But he was a, he's a philosopher. Yeah, that's interesting. But yeah, anyway, there was kind of no such distinction then that's more of a modern thing. And but anyway, I think these days there's a very interesting space in between the two. So in the story of the 20th century and the early 21st century, what is the overlap between mathematics and physics, would you say? Well, I think it's actually become very, very complicated. I think it's really interesting to see a lot of what my colleagues in the math department are doing. They, most of what they're doing, they're doing all sorts of different things, but most of them have some kind of overlap with physics or other. So, I mean, I'm personally interested in one particular aspect of this overlap, which I think has a lot to do with the most fundamental ideas about physics and about mathematics. But there's just, you kind of see this, this really, really everywhere at this point. Which particular overlap are you looking at, group theory? Yeah, so the, at least what the way it seems to me that if you look at physics and look at the, our most successful laws of fundamental physics, they're really, you know, they have a certain kind of mathematical structure. It's based upon certain kind of mathematical objects and geometry connections and curvature, the spinors, the Dirac equation. And that these, this very deep mathematics provides kind of a unifying set of math, of ways of thinking that allow you to make a unified theory of physics. But the interesting thing is that if you go to mathematics and look at what's been going on in mathematics the last 1500 years, and even especially recently, there's a, similarly, some kind of unifying ideas which bring together different areas of mathematics which have been especially powerful in number theory recently. And there's a book, for instance, by Edward Frankel about love and math. And yeah, that book's great. I recommend it highly. It's partially accessible. But there's a nice audio book that I listened to while running an exceptionally long distance, like across the San Francisco Bridge. And there's something magic about the way he writes about it. But some of the group theory in there is a little bit difficult. Yeah, it's a problem with any of these things to kind of really say what's going on and make it accessible is very hard. He, in this book and elsewhere, I think, takes the attitude that kinds of mathematics he's interested in and that he's talking about are provide kind of a grand unified theory of mathematics. They bring together geometry and number theory and representation theory, a lot of different ideas in a really unexpected way. But I think to me, the most fascinating thing is if you look at the kind of grand unified theory of mathematics he's talking about and you look at the physicist kind of ideas about unification, it's more or less the same mathematical objects are appearing in both. So it's this, I think there's a really, we're seeing a really strong indication that the deepest ideas that we're discovering about physics and some of the deepest ideas that mathematicians are learning about are really, are intimately connected. Is there something, like if I was five years old and you were trying to explain this to me, is there ways to try to sneak up to what this unified world of mathematics looks like? You said number theory, you said geometry, words like topology. What does this universe begin to look like? Are these, what should we imagine in our mind? Is it a three dimensional surface and we're trying to say something about it? Is it triangles and squares and cubes? Like what are we supposed to imagine in our minds? Is this natural number? What's a good thing to try to, for people that don't know any of these tools except maybe some basic calculus and geometry from high school that they should keep in their minds as to the unified world of mathematics that also allows us to explore the unified world of physics? I mean, what I find kind of remarkable about this is the way in which these, we've discovered these ideas, but they're actually quite alien to our everyday understanding. We grow up in this three spatial dimensional world and we have intimate understanding of certain kinds of geometry and certain kinds of things. But these things that we've discovered in both math and physics are, that they're not at all close, have any obvious connection to kind of human everyday experience. They're really quite different. And I can say some of my initial fascination with this when I was young and starting to learn about it was actually exactly this kind of arcane nature of these things. It was a little bit like being told, well, there are these kind of semi-mystical experience that you can acquire by a long study and whatever, except that it was actually true. There's actually evidence that this actually works. So I'm a little bit wary of trying to give people that kind of thing, because I think it's mostly misleading. But one thing to say is that, geometry is a large part of it. And maybe one interesting thing to say very, that's about more recent, some of the most recent ideas is that when we think about the geometry of our space and time, it's kind of three spatial and one time dimension. It's a physics is in some sense about something that's kind of four dimensional in a way. And a really interesting thing about some of the recent developments in number theory have been to realize that these ideas that we were looking at naturally fit into a context where your theory is kind of four dimensional. Geometry is a big part of this, and we know a lot and feel a lot about two, one, two, three dimensional geometry. So wait a minute. So we can at least rely on the four dimensions of space and time and say that we can get pretty far by working in those four dimensions. I thought you were gonna scare me that we're gonna have to go to many, many, many, many more dimensions than that. My point of view, which goes against a lot of these ideas about unification is that no, this is really, everything we know about really is about four dimensions that you can actually understand a lot of these structures that we've been seeing in fundamental physics and in number theory, just in terms of four dimensions, that it's in some sense, I would claim, has been a mistake that physicists have made for decades and decades to try to go to higher dimensions, to try to formulate a theory in higher dimensions. And then you're stuck with the problem, how do you get rid of all these extra dimensions that you've created? And because we only ever see anything in four dimensions. That kind of thing leads us astray, you think? So creating all these extra dimensions just to give yourself extra degrees of freedom. Isn't that the process of mathematics is to create all of these trajectories for yourself, but eventually you have to end up at a final place. But it's okay to sort of create abstract objects on your path to proving something. Yeah, certainly. And from a mathematician's point of view, I mean, the kinds of, mathematicians also are very different than physicists in that we like to develop very general theories. If we have an idea, we want to see what's the greatest generality in which you can talk about it. So from the point of view of most of the ways geometry is formulated by mathematicians, it really doesn't matter, it works in any dimension. We can do one, two, three, four, any number. There's no particular, for most of geometry, there's no particular special thing but four. But anyway, but what physicists have been trying to do over the years is try to understand these fundamental theories in a geometrical way. And it's very tempting to kind of just start bringing in extra dimensions and using them to explain the structure. But typically this attempt kind of founders because you just don't know, you end up not being able to explain why we only see four. It is nice in the space of physics that like if you look at Fermat's last theorem, it's much easier to prove that there's no solution for n equals three than it is for the general case. And so I guess that's the nice benefit of being a physicist is you don't have to worry about the general case because we live in a universe with n equals four in this case. Yeah, physicists are very interested in saying something about specific examples. And I find that interesting when I'm trying to do things in mathematics and I'm trying even teaching courses and to mathematics students, I find that I'm teaching them in a different way than most mathematicians because I'm very often very focused on examples on what's kind of the crucial example that shows how this powerful new mathematical technique, how it works and why you would want to do it. And I'm less interested in kind of proving a precise theorem about exactly when it's gonna work and when it's not gonna work. Do you usually think about really simple examples, like both for teaching and when you try to solve a difficult problem, do you construct like the simplest possible examples that captures the fundamentals of the problem and try to solve it? Yeah, exactly, that's often a really fruitful way to if you've got some idea to just kind of try to boil it down to what's the simplest situation in which this kind of thing is gonna happen and then try to really understand that and understand that and that is almost always a really good way to get insight into. Do you work with paper and pen or like for example, for me, coming from the programming side, if I look at a model, if I look at some kind of mathematical object, I like to mess around with it sort of numerically, I just visualize different parts of it, visualize however I can so most of the work is like neural networks for example, is you try to play with the simplest possible example and just to build up intuition by, you know, any kind of object has a bunch of variables in it. You start to mess around with them in different ways and visualize in different ways to start to build intuition. Or do you go the Einstein route and just imagine like everything inside your mind and sort of build like thought experiments and then work purely on paper and pen? Well, the problem with this kind of stuff I'm interested in is you rarely can kind of, it's rarely something that is really kind of, or even the simplest example, you know, you can kind of see what's going on by looking at something happening in three dimensions. There's generally the structures involved are, either they're more abstract or if you try to kind of embed them in some kind of space and where you could manipulate them in some kind of geometrical way, it's gonna be a much higher dimensional space. So even simple examples, embedding them into three dimensional space, you're losing a lot. Yeah, but to capture what you're trying to understand about them, you have to go to four or more dimensions. So it starts to get to be hard to, and you can train yourself to try it as much as to kind of think about things in your mind. And, you know, I often use pad and paper and I'm often in my office, I often use the blackboard and you are kind of drawing things, but they're really kind of more abstract representations of how things are supposed to fit together. And they're not really, unfortunately, not just kind of really living in three dimensions where you can... Are we supposed to be sad or excited by the fact that our human minds can't fully comprehend the kind of mathematics you're talking about? I mean, what do we make of that? I mean, to me, that makes me quite sad. It makes it seem like there's a giant mystery out there that we'll never truly get to experience directly. It is kind of sad how difficult this is. I mean, or I would put it a different way that, you know, most questions that people have about this kind of thing, you know, you can give them a really true answer and really understand it, but the problem is one more of time. It's like, yes, you know, I could explain to you how this works, but you'd have to be willing to sit down with me and, you know, work at this repeatedly for, you know, for hours and days and weeks. And, I mean, it's just gonna take that long for your mind to really wrap itself around what's going on. And so that does make things inaccessible, which is sad, but I mean, it's just kind of part of life that we all have a limited amount of time and we have to decide what we're gonna spend our time doing. Speaking of a limited amount of time, we only have a few hours, maybe a few days together here on this podcast. Let me ask you the question of amongst many of the ideas that you work on in mathematics and physics, what's used the most beautiful idea or one of the most beautiful ideas, maybe a surprising idea. And once again, unfortunately, the way life works, we only have a limited time together to try to convey such an idea. Okay, well, actually, let me just tell you something, which I'm tempted to kind of start trying to explain what I think is this most powerful idea that brings together math and physics, ideas about groups and representations and how it fits quantum mechanics. But in some sense, I wrote a whole textbook about that and I don't think we really have time to get very far into it. Well, can I actually, on a small tangent, you did write a paper towards a grant unified theory, mathematics and physics. Maybe you could step there first, what is the key idea in that paper? Well, I think we've kind of gone over that. I think that the key idea is what we were talking about earlier, that just kind of a claim that if you look and see what's the have been successful ideas of unification in physics over the last 50 years or so, and what has been happening in mathematics and the kind of thing that Frankel's book is about, that these are very much the same kind of mathematics. And so it's kind of an argument that there really is, you shouldn't be looking to unify just math or just fundamental physics, but taking inspiration for looking for new ideas in fundamental physics, that they are gonna be in the same direction of getting deeper into mathematics and looking for more inspiration in mathematics from these successful ideas about fundamental physics. Could you put words to sort of the disciplines we're trying to unify? So you said number theory, are we literally talking about all the major fields of mathematics? So it's like the number theory, geometry, so the differential geometry, topology. Yeah, so the, I mean, one name for this, that this is acquired in mathematics is the so-called Langlands program. And so this started out in mathematics, it's that Robert Langlands kind of realized that a lot of what people were doing and that was starting to be really successful in number theory in the 60s. And so that this actually was, anyway, that this could be a thought of in terms of these ideas about symmetry in groups and representations and in a way that was also close to some ideas about geometry. And then more later on in the 80s and 90s, there was something called geometric Langlands that people realized that you could take what people have been doing in number theory in Langlands and just forget about the number theory and ask what is this telling you about geometry? And you get a whole, some new insights into certain kinds of geometry that way. So it's, anyway, that's kind of the name for this area is Langlands and geometric Langlands. And just recently in the last few months, there's been, there's kind of really major paper that appeared by Peter Schultz and Laurent Farg, where they made some serious advance and try to understand a very much kind of a local problem of what happens in number theory near a certain prime number. And they turned this into a problem of exactly the kind of geometric Langlands people had been doing, these kind of pure geometry problem. And they found by generalizing the mathematics, they could actually reformulate it in that way and it worked perfectly well. One of the things that makes me sad is, I'm a pretty knowledgeable person and then, what is it? At least I'm in the neighborhood like theoretical computer science, right? And it's still way out of my reach. And so many people talk about like Langlands, for example, is one of the most brilliant people in mathematics and just really admire his work. And I can't, it's like almost I can't hear the music that he composed and it makes me sad. Yeah, well, I mean, I think that unfortunately, it's not just you, it's I think even most mathematicians have no, really don't actually understand what this is about them in the group of people who really understand all these ideas. And so for instance, this paper of Shultz and Farag that I was talking about, the number of people who really actually understand how that works is anyway, who is very, very small. And so I think even you find if you talk to mathematicians and physicists, even they will often feel that, there's this really interesting sounding stuff going on and which I should be able to understand. It's kind of in my own field. I have a PhD in, but it still seems pretty clearly far beyond me right now. Well, if we can step into the back to the question of beauty, is there an idea that maybe is a little bit smaller that you find beautiful in the space of mathematics or physics? There's an idea that, I kind of went, got a physics PhD and spent a lot of time learning about mathematics. And I guess it was embarrassing that I hadn't really actually understand this very simple idea until I kind of learned it when I actually started teaching math classes, which is maybe that there's a simple way to explain kind of the fundamental way in which algebra and geometry are connected. So you normally think of geometry is about these spaces and these points and you think of algebra is this very abstract thing about these abstract objects that satisfy certain kinds of relations. You can multiply them and add them and do stuff, but it's completely abstract. It is nothing geometric about it. But the kind of really fundamental idea is that unifies algebra and geometry is to think whenever anybody gives you what you call an algebra, some abstract thing of things that you can multiply and add, that you should ask yourself, is that algebra the space of functions on some geometry? So one of the most surprising examples of this, for instance, is a standard kind of thing that seems to have nothing to do with geometry is the integers. So you can multiply them and add them. It's an algebra, but it seems to have nothing to do with geometry. But if you ask yourself this question and ask, is our integers, if somebody gives you an integer, can you think of it as a function on some space, on some geometry? And it turns out that yes, you can. And the space is the space of prime numbers. And so what you do is you just, if somebody gives you an integer, you can make a function on the prime numbers by just at each prime number, taking that integer modulo, that prime. So if you say, I don't know, if you get given 10, you know, 10, and you ask, what is its value at two? Well, it's five times two, so mod two, it's zero. So it has zero at one. What is its value at three? Well, it's nine plus one, so it's one mod three. So it's zero at two, it's one at three, and you can kind of keep going. And so this is really kind of a truly fundamental idea. It's at the basis of what's called algebraic geometry, and it just links these two parts of mathematics that look completely different. And it's just an incredibly powerful idea. And so much of mathematics emerges from this kind of simple relation. So you're talking about mapping from one discrete space to another. So for a second, I thought perhaps mapping like a continuous space to a discrete space, like functions over a continuous space. Yeah. Well, I mean, you can take, if somebody gives you a space, you can ask, you can say, well, let's, and this is also, this is part of the same idea. The part of the same idea is that if you try and do geometry and somebody tells you, here's a space, that what you should do is you should wait to say, wait a minute, maybe I should be trying to solve this using algebra. And so if I do that, the way to start is you give me the space, I start to think about the functions on the space. Okay, so for each point in the space, I associate a number. I can take different kinds of functions and different kinds of values, but basically functions on a space. So what this insight is telling you is that if you're a geometer, often the way to work is to change your problem into algebra by changing your space, stop thinking about your space and the points in it and think about the functions on it. Got it. And if you're an algebraist and you've got these abstract algebraic gadgets that you're multiplying and adding, say, wait a minute, are those gadgets, can I think of them in some way as a function on a space? What would that space be? And what kind of functions would they be? And that going back and forth really brings these two completely different looking areas of mathematics together. Do you have particular examples where it allowed to prove some difficult things by jumping from one to the other? Is that something that's a part of modern mathematics where such jumps are made? Oh yeah, this is kind of all the time. Much of modern number theory is kind of based on this idea. But, and when you start doing this, you start to realize that you need, what simple things on one side of the algebra start to require you to think about the other side about geometry in a new way. You have to kind of get a more sophisticated idea about geometry. Or if you start thinking about the functions on a space, you may need a more sophisticated kind of algebra. But in some sense, I mean, much or most of modern number theory is based upon this move to geometry. And there's also a lot of geometry and topology is also based upon. Yeah, if you wanna understand the topology of something, you look at the functions, you do Durham cohomology and you get the topology. Anyway. Well, let me ask you then the ridiculous question. You said that this idea is beautiful. Can you formalize the definition of the word beautiful? And why is this beautiful? Like first, why is this beautiful? And second, what is beautiful? Well, and I think there are many different things you can find beautiful for different reasons. I mean, I think in this context, the notion of beauty, I think really is just kind of, an idea is beautiful if it's packages a huge amount of kind of power and information into something very simple. So in some sense, I mean, you can almost kind of try and measure it in the sense of what are the implications of this idea? What non-trivial things does it tell you versus how simply can you express the idea? So the level of compression, what is it, correlates with beauty? Yeah, that's one aspect of it. And so you can start to tell that an idea is becoming uglier and uglier as you start kind of having to, it doesn't quite do what you want. So you throw in something else to the idea and you keep doing that until you get what you want. But that's how you know you're doing something uglier and uglier when you have to kind of keep adding in more into what was originally a fairly simple idea and making it more and more complicated to get what you want. Okay, so let's put some philosophical words on the table and try to make some sense of them. One word is beauty. Another one is simplicity, as you mentioned. Another one is truth. So do you have a sense, if I give you two theories, one is simpler, one is more complicated. Do you have a sense of which one is more likely to be true to capture deeply the fabric of reality? The simple one or the more complicated one? Yeah, I think all of our evidence, what we see in the history of the subject is the simpler one, no. Often it's simpler in a surprising way, but yeah, that we just don't, we just, I think the kind of best theories we've been coming up with are ultimately, when properly understood, relatively simple and much, much simpler than you would expect them to be. Do you have a good explanation why that is? Is it just because humans want it to be that way? Or are we just like ultra biased and we just kind of convince ourselves that simple is better because we find simplicity beautiful? Or is there something about our actual universe that at the core is simple? My own belief is that there is something about a universe that's simple, and as I was trying to say that, there is some kind of fundamental thing about math, physics, and physics, and all this picture, which is in some sense simple. It's true that, it's of course true that our minds have certain, are very limited and can certainly do certain things and not others. So it's in principle possible that there's some great insight, there are a lot of insights into the way the world works, which just aren't accessible to us because that's not the way our minds work. We don't, and that what we're seeing, this kind of simplicity is just because that's all we ever have any hope of seeing, but. So there's a brilliant physicist by the name of Sabine Hassenfelder, who both agrees and disagrees with you, or I suppose agrees that the final answer will be simple. But simplicity and beauty leads us astray in the local pockets of scientific progress. Do you agree with her disagreement, do you disagree with her agreement? And agree with the agreement, and so on? I, yes, I find it was really fascinating reading her book and anyway, I was finding disagreeing with a lot, but then at the end when she says, yes, when we find, when we actually figure this out, it will be simple. And okay, so we agree in the end. Does beauty lead us astray, which is the core thesis of her work in that book? I actually, I guess I do disagree with her on that so much. I don't think, and especially, and I actually fairly strongly disagree with her about sometimes the way she'll refer to math. And so the problem is, you know, physicists and people in general just refer to it as math, and they're often meaning not what I would call math, which is the interesting ideas of math, but just some complicated calculation. And so I guess my feeling about it is more that it's very, the problem with talking about simplicity and using simplicity as a guide is that it's very, it's very easy to fool yourself. And it's very easy to decide to fall in love with an idea. You have an idea, you think, oh, this is great, and you fall in love with it. And like any kind of love affair, it's very easy to believe that the object of your affections is much more beautiful than the others might think that they really are. And that's very, very easy to do. So if you say, I'm just gonna pursue ideas about beauty and mathematics and this, it's extremely easy to just fool yourself, I think. And I think that's a lot of what the story she was thinking of about where people have gone astray. That I think it's, I would argue that as more people, it's not that there was some simple, powerful, wonderful idea which they'd found, and it turned out not to be useful, but it was more that they kind of fooled themselves that this was actually a better idea than it really was, and that it was simpler, more beautiful than it really was, is a lot of the story. I see, so it's not that the simplicity would be Lisa's astray, it's just people are people and they fall in love with whatever idea they have. And then they weave narratives around that idea, or they present in such a way that emphasizes the simplicity and the beauty. Yeah, that's part of it. But the thing about physics that you have is that you, what really can tell it, if you can do an experiment and check and see if nature is really doing what your idea expects, that you do in principle have a way of really testing it. And it's certainly true that if you thought you had a simple idea and that doesn't work, and you go out and do an experiment, and what actually does work is some more, maybe some more complicated version of it, that can certainly happen and that can be true. I think her emphasis is more that I don't really disagree with is that people should be concentrating on when they're trying to develop better theories on more on self-consistency, not so much on beauty, but not is this idea beautiful, but is there something about the theory which is not quite consistent and use that as a guide, that there's something wrong there which needs fixing. And so I think that part of her argument, I think I was, we're on the same page about. What is consistency and inconsistencies? What exactly, do you have examples in mind? Well, it can be just simple inconsistency between theory and experiment that if you, so we have this great fundamental theory, but there are some things that we see out there which don't seem to fit in it like dark energy and dark matter for instance. But if there's something which you can't test experimentally, I think she would argue and I would agree that for instance, if you're trying to think about gravity and how are you gonna have a quantum theory of gravity, you should kind of be, test any of your ideas with kind of a thought experiment, does this actually give a consistent picture of what's gonna happen, of what happens in this particular situation or not. So this is a good example you've written about this. Since quantum gravitational effects are really small, super small, arguably unobservably small, should we have hope to arrive at a theory of quantum gravity somehow? What are the different ways we can get there? You've mentioned that you're not as interested in that effort because basically, yes, you cannot have ways to scientifically validate it given the tools of today. Yeah, I've actually, I've over the years certainly spent a lot of time learning about gravity and about attempts to quantize it, but it hasn't been that much in the past, the focus of what I've been thinking about. But my feeling was always, as I think, and Spina would agree that the, one way you can pursue this if you can't do experiments is just this kind of search for consistency. It can be remarkably hard to come up with a completely consistent model of this and a way that brings together quantum mechanics and general relativity. And that's, I think, kind of been the traditional way that people who have pursued quantum gravity have often pursued, you know, we have the best route to finding a consistent theory of quantum gravity. And string theorists will tell you this, other people will tell you it, it's kind of what people argue about. But the problem with all of that is that you end up, the danger is that you end up with, that everybody could be successful. Everybody's program for how to find a theory of quantum gravity, you know, ends up with something that is consistent. And so, in some sense, you could argue this is what happened to the string theorists. They solved their problem of finding a consistent theory of quantum gravity, but they found 10 of the 500 solutions. So, you know, if you believe that everything that they would like to be true is true, well, okay, you've got a theory, but it ends up being kind of useless because it's just one of an infinite, essentially infinite number of things which you have no way to experimentally distinguish. And so this is just a depressing situation. But I do think that there is a, so again, I think pursuing ideas about what, more about beauty and how can you integrate and unify these issues about gravity with other things we know about physics and can you find a theory where these fit together in a way that makes sense and hopefully predict something that's much more promising. Well, it makes sense and hopefully, I mean, we'll sneak up onto this question a bunch of times because you kind of said a few slightly contradictory things which is like, it's nice to have a theory that's consistent, but then if the theory is consistent, it doesn't necessarily mean anything. So like- It's not enough, it's not enough. It's not enough and that's the problem. So it's like, it keeps coming back to, okay, there should be some experimental validation. So, okay, let's talk a little bit about string theory. You've been a bit of an outspoken critic of string theory. Maybe one question first to ask is what is string theory? And beyond that, why is it wrong? Or rather, as the title of your blog says, not even wrong. Okay, well, one interesting thing about the current state of string theory is that I think, I'd argue, it's actually very, very difficult to, at this point, to say what string theory means. If people say they're a string theorist, what they mean and what they're doing is kind of hard, it's hard to pin down the meaning of the term. But the initial meaning, I think, goes back to, there was kind of a series of developments starting in 1984 in which people felt that they had found a unified theory of our so-called standard model of all the standard, well-known kind of particle interactions and gravity and it all fit together in a quantum theory. And that you could do this in a very specific way by instead of thinking about having a quantum theory of particles moving around in space-time, think about quantum theory of kind of one-dimensional loops moving around in space-time, so-called strings. And so instead of one degree of freedom, these have an infinite number of degrees of freedom, it's a much more complicated theory. But you can imagine, okay, we're gonna quantize this theory of loops moving around in space-time. And what they found is that you could do this and you could fairly, relatively straightforwardly make sense of such a quantum theory, but only if space and time together were 10-dimensional. And so then you had this problem, again, the problem I referred to at the beginning of, okay, now once you make that move, you've got to get rid of six dimensions. And so the hope was that you could get rid of the six dimensions by making them very small and that consistency of the theory would require that these six dimensions satisfy a very specific condition called being a Calabi-Ao manifold, and that we knew very, very few examples of this. So what got a lot of people very excited back in 84, 85 was the hope that you could just take this 10-dimensional string theory and find one of a limited number of possible ways of getting rid of six dimensions by making them small, and then you would end up with an effective four-dimensional theory, which looked like the real world. This was the hope. So then there's then a very long story about what happened to that hope over the years. I mean, I would argue, and part of the point of the book and its title was that this ultimately was a failure, that you ended up, that this idea just didn't, there ended up being just too many ways of doing this, and you didn't know how to do this consistently, that it was kind of not even wrong in the sense that you never could pin it down well enough to actually get a real falsifiable prediction out of it that would tell you it was wrong, but it was kind of in the realm of ideas which initially look good, but the more you look at them, they just, they don't work out the way you want, and they don't actually end up carrying the power or that you originally had this vision of. And yes, the book title is not even wrong. Your blog, your excellent blog title is not even wrong. Okay, but there's nevertheless been a lot of excitement about string theory through the decades, as you mentioned. What are the different flavors of ideas that came, like that branched out? You mentioned 10 dimensions, you mentioned loops with infinite degrees of freedom. What other interesting ideas to you that kind of emerged from this world? Well, yeah, I mean, the problem in talking about the whole subject, and part of the reason I wrote the book is that it gets very, very complicated. I mean, there's a huge amount, you know, a lot of people got very interested in this, a lot of people worked on it, and in some sense, I think what happened is exactly because the idea didn't really work, that this caused people to, you know, instead of focusing on this one idea and digging in and working on that, they just kind of kept trying new things. And so people, I think, ended up wandering around in a very, very rich space of ideas about mathematics and physics and discovering, you know, all sorts of really interesting things. It's just, the problem is there tended to be an inverse relationship between how interesting and beautiful and fruitful this new idea that they were trying to pursue was, and how much it looked like the real world. So there's a lot of beautiful mathematics came out of it. I think one of the most spectacular is what the physicists call two-dimensional conformal field theory. And so these are basically quantum field theories and kind of think of it as one space and one time dimension, which, you know, have just this huge amount of symmetry and a huge amount of structure, which just some totally fantastic mathematics behind it. And again, and some of that mathematics is exactly also what appears in the Langlands program. So a lot of the first interaction between math and physics around the Langlands program has been around these two-dimensional conformal field theories. Is there something you could say about what are the major problems are with string theory? So like, besides that there's no experimental validation, you've written that a big hole in string theory has been its perturbative definition. Yeah. Perhaps that's one, can you explain what that means? Well, maybe to begin with, I think the simplest thing to say is, you know, the initial idea really was that, okay, we have this, instead of what's great is we have this thing that only works, that's very structured and has to work in a certain way, for it to make sense. And, but then you ended up in 10 space-time dimensions. And so to get back to physics, you had to get rid of five of the dimensions, six of the dimensions. And the bottom line I would say, in some sense, it's very simple, that what people just discovered is just, there's kind of no particularly nice way of doing this, there's an infinite number of ways of doing it, and you can get whatever you want, depending on how you do it. So you end up, the whole program of string theory and the whole program of starting at 10 dimensions and getting to four, just kind of collapses out of a lack of any way to kind of get to where you want, because you can get anything. There'll be the hope around that problem, has always been that the standard formulation that we have of string theory, which is, you can go by the name perturbative, but it's kind of, there's a standard way we know of given a classical theory of constructing quantum theory and working with it, which is, this is the so-called perturbation theory, that we know how to do, and that by itself just doesn't give you any hint as to what to do about the six dimensions. So actual perturbative string theory by itself really only works in 10 dimensions. So you have to start making some kinds of assumptions about how I'm gonna go beyond this formulation that we really understand of string theory and get rid of these six dimensions. So kind of the simplest one was the Claveau postulate, but when that didn't really work out, people tried more and more different things, and the hope has always been that the solution to this problem would be that you would find a deeper and better understanding of what string theory is that would actually go beyond this perturbative expansion and which would generalize this, and that once you had that, it would solve this problem of, it would pick out what to do with the six dimensions. How difficult is this problem? So if I could restate the problem, it seems like there's a very consistent physical world operating in four dimensions, and how do you map a consistent physical world in 10 dimensions to a consistent physical world in four dimensions? And how difficult is this problem? Is that something you can even answer? Just in terms of physics intuition, in terms of mathematics, mapping from 10 dimensions to four dimensions. Well, basically, I mean, you have to get rid of the six dimensions. So there's kind of two ways of doing it. One is what we call compactification. You say that there really are 10 dimensions, but for whatever reason, six of them are really, are so, so small, we can't see them. So you basically start out with 10 dimensions and what we call, make six of them not go out to infinity, but just kind of a finite extent, and then make that size go down so small, it's unobservable. But that's a math trick. So can you also help me build an intuition about how rich and interesting the world in those six dimensions is? So compactification seems to imply that. Well, it's not very interesting. Well, no, but the problem is that what you learn if you start doing mathematics, looking at geometry and topology and more and more dimensions is that, I mean, asking the question, like what are all possible six dimensional spaces is just, it's kind of an unanswerable question. It's just, I mean, it's even kind of technically undecidable in some way. There are just too many things you can do with all these. If you start trying to make one dimensional spaces, it's like, well, you've got a line, you can make a circle, you can make graphs, you can kind of see what you can do. But as you go to higher and higher dimensions, there are just so many ways you can put things together and get something of that dimensionality. And so unless you have some very, very strong principle, we're just gonna pick out some very specific ones of these six dimensional spaces. And there are just too many of them and you can get anything you want. So if you have 10 dimensions, the kind of things that happen, say that's actually the way, that's actually the fabric of our realities, 10 dimensions. There's a limited set of behaviors of objects. I don't even know what the right terminology to use that can occur within those dimensions, like in reality. So what I'm getting at is like, is there some consistent constraints? So if you have some constraints that map to reality, then you can start saying like, dimension number seven is kind of boring. All the excitement happens in the spatial dimensions, one, two, three. And time is also kind of boring. Some are more exciting than others, or we can use our metric of beauty. Some dimensions are more beautiful than others. Once you have an actual understanding of what actually happens in those dimensions in our physical world, as opposed to sort of all the possible things that could happen. In some sense, I mean, just the basic fact is you need to get rid of them. We don't see them. So you need to somehow explain them. The main thing you're trying to do is to explain why we're not seeing them. And so you have to come up with some theory of these extra dimensions and how they're gonna behave. And string theory gives you some ideas about how to do that. But the bottom line is where you're trying to go with this whole theory you're creating is to just make all of its effects essentially unobservable. So it's not a really, it's an inherently kind of dubious and worrisome thing that you're trying to do there. Why are you just adding in all this stuff and then trying to explain why we don't see it? I mean, it just- This may be a dumb question, but is this an obvious thing to state that those six dimensions are unobservable or anything beyond four dimensions is unobservable? Or do you leave a little door open to saying the current tools of physics, and obviously our brains aren't unable to observe them, but we may need to come up with methodologies for observing them. So as opposed to collapsing your mathematical theory into four dimensions, or leaving the door open a little bit too, maybe we need to come up with tools that actually allow us to directly measure those dimensions. Yes, I mean, you can certainly assume that we've got model, look at models with more dimensions and ask what would be observable effects? How would we know this? And then you go out and do experiments. So for instance, you have a, like gravitationally you have an inverse square law of forces. Okay, if you had more dimensions, that inverse square law would change to something else. So you can go and start measuring the inverse square law and say, okay, inverse square law is working, but maybe if I get, and it turns out to be actually kind of very, very hard to measure gravitational effects at even kind of somewhat macroscopic distances because they're so small. So you can start looking at the inverse square law and say, start trying to measure it at shorter and shorter distances and see if there were extra dimensions at those distance scales, you would start to see the inverse square law fail. And so people look for that. And again, you don't see it, but you can, I mean, there's all sorts of experiments of this kind you can imagine which test for effects of extra dimensions at different distance scales. But none of them, I mean, they all just don't work. Nothing yet. Nothing yet, but you can say, ah, but it's just much, much smaller. You can say that. Which by the way makes LIGO and the detection of gravitational waves quite an incredible project. Ed Whitten is often brought up as one of the most brilliant mathematicians and physicists ever. What do you make of him and his work on string theory? Well, I think he's a truly remarkable figure. I've had the pleasure of meeting him first when he was a postdoc. And I mean, he's a just completely amazing mathematician and physicist. And he's quite a bit smarter than just about any of us and also more hardworking. And it's a kind of frightening combination to see how much he's been able to do. But I would actually argue that his greatest work, the things that he's done that have been of just this mind blowing significance of giving us, I mean, he's completely revolutionized some areas of mathematics. He's totally revolutionized the way we understand the relations between mathematics and physics. And most of those, his greatest work is stuff that doesn't have, has little or nothing to do with string theory. I mean, for instance, he, so he was actually one of fields. The very strange thing about him in some sense is that he doesn't have a Nobel Prize. So there's a very large number of people who are nowhere near as smart as he is and don't work anywhere near as hard who have Nobel prizes. I think he just had the misfortune of coming into the field at a time when things had gotten much, much, much tougher and nobody really had, no matter how smart he was, it would have been very hard to come up with a new idea that was gonna work physically and get you a Nobel Prize. But he, you know, he got a Fields Medal for a certain work he did in mathematics. And that's just completely unheard of, you know, for mathematicians to give a Fields Medal to someone outside their field in physics is really, you know, you wouldn't have before he came around. I don't think anybody would have thought that was even conceivable. So you're saying he came into the field of theoretical physics at a time when and still to today is you can't get a Nobel Prize for purely theoretical work. The specific problem of trying to do better than the standard, the standard model is just this insanely successful thing. And it kind of came together in 1973 pretty much. And post, and so, and all of the people who kind of were involved in that coming together, you know, many of them ended up with Nobel prizes for that. But if you look post 1973, pretty much, it's a little bit more, there's some edge cases if you like, but if you look post 1973 at what people have done to try to do better than the standard model and to get a better, you know, idea, it really hasn't, it's been too hard a problem. It hasn't worked, the theory's too good. And so it's not that other people went out there and did it and not him, and that they got no prizes for doing it. It's like no one really, the kind of thing he's been trying to do with string theory is not, no one has been able to do since 1973. Is there something you can say about the standard model? So the four laws of physics that seems to work very well, and yet people are striving to do more, talking about unification and so on, why? What's wrong, what's broken about the standard model? Why does it need to be improved? I mean, the thing that's gets most attention is gravity, that we have trouble. So you want to, in some sense, integrate what we know about the gravitational force with it and have a unified quantum field theory that has gravitational interactions also. So that's the big problem everybody talks about. I mean, but it's also true that if you look at the standard model, it has these very, very deep, beautiful ideas, but there's certain aspects of it that are very, that are, let's just say that they're not beautiful. They're not, you have to, to make the thing work, you have to throw in lots and lots of extra parameters at various points. And a lot of this has to do with the so-called, you know, the so-called Higgs mechanism in the Higgs field, that if you look at the theory, it's, everything is, if you forget about the Higgs field and what it needs to do, the rest of the theory is very, very constrained and has very, very few free parameters, really, a very small number. There's a very small number of parameters and a few integers which tell you what the theory is. To make this work as a theory of the real world, you need a Higgs field and you need to, it needs to do something. And once you introduce that Higgs field, all sorts of parameters make an appearance. So now we've got 20 or 30 or whatever parameters that are gonna tell you what all the masses of things are and what's gonna happen. So you've gone from a very tightly constrained thing with a couple of parameters to this thing, which the minute you put it in, you had to add all this extra, all these extra parameters to make things work. And so that, it may be one argument as well, that's just the way the world is. And the fact that you don't find that aesthetically pleasing is just your problem. Maybe we live in a multiverse and those numbers are just different in every universe. But another reasonable conjecture is just that, well, this is just telling us that there's something we don't understand about what's going on in a deeper way which would explain those numbers. And there's some kind of deeper idea about where the Higgs field comes from and what's going on, which we haven't figured out yet. And that's what we should look for. But to stick on string theory a little bit longer, could you play devil's advocate and try to argue for string theory, why it is something that deserved the effort that it got and still, like if you think of it as a flame, still should be a little flame that keeps burning. Well, I think the most positive argument for it is all sorts of new ideas about mathematics and about parts of physics really emerged from it. So it was very a fruitful source of ideas. And I think this is actually one argument you'll definitely, which I kind of agree with, you'll hear from Witten and from other string theorists that this is just such a fruitful and inspiring idea and it's led to so many other different things coming out of it that there must be something right about this. Anyway, I think that's probably the strongest thing that they've got. But you don't think there's aspects to it that could be neighboring to a theory that does unify everything, to a theory of everything. Like it could, it may not be exactly the theory, but sticking on it longer might get us closer to the theory of everything. Well, the problem with it now really is that you really don't know what it is now. You never, nobody has ever kind of come up with this non-perturbative theory. So it's become more and more frustrating and an odd activity to try to argue with a string theorist about string theory because it's become less and less well-defined what it is. And it's become actually more and more kind of a, whether you have this weird phenomenon of people calling themselves string theorists when they've never actually worked on any theory were there any strings anywhere. So what has actually happened kind of sociologically is that you started out with this fairly well-defined proposal and then I would argue because that didn't work, people branched out in all sorts of directions doing all sorts of things. It became farther and farther removed from that. And for sociological reasons, the ones who kind of started out or now or were trained by the people who worked on that have now become this string theorists and but it's becoming almost more kind of a tribal denominator than a, I think it's very hard to know what you're arguing about when you're arguing about string theory these days. Well, to push back on that a little bit, I mean, string theory is just a term, right? It doesn't like you could, like this is the way language evolves, is it could start to represent something more than just the theory that involves strings. It could represent the effort to unify the laws of physics, right? At high dimensions with these super tiny objects, right? Or something like that. I mean, we can sort of put string theory aside. So for example, neural networks in the space of machine learning, there was a time when they were extremely popular, they became much, much less popular to a point where if you mentioned neural networks, you're getting no funding and you're not going to be respected at conferences. And then once again, neural networks became all the rage about 10, 15 years ago, and it goes up and down. And a lot of people would argue that using terminology like machine learning and deep learning is often misused over general. Everything that works is deep learning, everything that doesn't isn't, something like that. That's just the way, again, we're back to sociological things. But I guess what I'm trying to get at is if we leave the sociological mess aside, do we throw out the baby with the bath water? Is there some, besides the side effects of nice ideas from the Ed Wittons of the world, is there some core truths there that we should stick by in the full beautiful mess of a space that we call string theory, that people call string theory? You're right, it is kind of a common problem that how what you call some field changes and evolves and in interesting ways as the field changes. But I mean, I guess what I would argue is the initial understanding of string theory that was quite specific, we're talking about a specific idea, 10 dimensional superstrings compactified in six dimensions. That, to my mind, the really bad thing that's happened to the subject is that it's hard to get people to admit, at least publicly, that that was a failure, that this really didn't work. And so de facto, what people do is people stop doing that and they start doing more interesting things, but they keep talking to the public about string theory and referring back to that idea and using that as kind of the starting point and as kind of the place where the whole tribe starts and everything else comes from. So the problem with this is that having as your initial name and what everything points back to, something which really didn't work out, it kind of makes everybody, it makes everything, you've created this potentially very, very interesting field with interesting things happening, but people in graduate school take courses on string theory and everything kind of, and this is what you tell the public in which you're continually pointing back. So you're continually pointing back to this idea which never worked out as your guiding inspiration. And it really kind of deforms your whole way of your hopes of making progress. And that's, to me, I think the kind of worst thing has happened in this field. Okay, sure, so there's a lack of transparency and sort of authenticity about communicating the things that failed in the past. And so you don't have a clear picture of like firm ground that you're standing on. But again, those are sociological things. And there's a bunch of questions I wanna ask you. So one, what's your intuition about why the original idea failed? So what can you say about why you're pretty sure it has failed? I mean, the initial idea was, as I tried to explain it, it was quite seductive in that you could see why Witten and others got excited by it. It was, at the time it looked like there were only a few of these possible clobby-ows that would work. And it looked like, okay, we just have to understand this very specific model and these very specific six dimensional spaces, and we're gonna get everything. And so it was a very seductive idea. But it just, as people work more and more about it, it just didn't, they just kind of realized that there are just more and more things you can do with your six dimensions and you can't, and this is just not going to work. Meaning like it's, I mean, what was the failure mode here? Is you could just have an infinite number of possibilities that you could do so you can come up with any theory you want. You can fit quantum mechanics. You can explain gravity. You can explain anything you want with it. Is that the basic failure mode? Yeah, so it's a failure mode of kind of that this idea ended up being essentially empty. That it just doesn't, ends up not telling you anything because it's consistent with just about anything. And so, I mean, there's a complex, if you try and talk with strength theories about this now, I mean, there's an argument, there's a long argument over this about whether, oh no, no, no, maybe there still are constraints coming out of this idea or not. Or maybe we live in a multiverse and everything is true anyway. So you can, there are various ways you can kind of, that strength theories have kind of react to this kind of argument that I'm making. Try to hold onto it. What about experimental validation? Is that a fair standard to hold before a theory of everything that's trying to unify quantum mechanics and gravity? Yeah, I mean, ultimately to be really convinced that, you know, that on some new idea that invocation really works, you need some kind of, you need to look at the real world and see that this is telling you something, something true about it. I mean, you know, either telling you that if you do some experiment and go out and do it, you'll get some unexpected result and that's the kind of gold standard, or it may be just that like all those numbers that are, we don't know how to explain, it will show you how to calculate them. I mean, it can be various kinds of experimental validation, but that's certainly ideally what you're looking for. How tough is this, do you think, for a theory of everything, not just string theory, for something that unifies gravity and quantum mechanics? So the very big and the very small, is this, let me ask it one way, is it a physics problem, a math problem, or an engineering problem? My guess is it's a combination of a physics and a math problem that you really need. It's not really engineering. It's not like there's some kind of well-defined thing you can write down and we just don't have enough computer power to do the calculation. That's not the kind of problem it is at all. But the question is, you know, what mathematical tools you need to properly formulate the problem is unclear. So one reasonable conjecture is the way, the reason that we haven't had any success yet is just that we're missing, either we're missing certain physical ideas or we're missing certain mathematical tools, which are some combination of them, which we need to kind of properly formulate the problem and see that it has a solution that looks like the real world. But those you need, I guess you don't, but there's a sense that you need both gravity, like all the laws of physics to be operating on the same level. So it feels like you need an object like a black hole or something like that in order to make predictions about, otherwise you're always making predictions about this joint phenomena. Or can you do that as long as the theory is consistent and doesn't have special cases for each of the phenomena? Well, your theory should, I mean, if your theory is gonna include gravity, our current understanding of gravity is that you should have, there should be black hole states in it, you should be able to describe black holes in this theory. And just one aspect that people concentrate a lot on is just this kind of questions about if your theory includes black holes like it's supposed to, and it includes quantum mechanics, then there's certain kind of paradoxes which come up. And so that's been a huge focus of kind of quantum gravity where it has been just those paradoxes. So stepping outside of string theory, can you just say first at a high level, what is a theory of everything? What is a theory of everything? What do we seek to accomplish? Well, I mean, this is very much a kind of reductionist point of view in the sense that, so it's not a theory, this is not gonna explain to you anything, it doesn't really, this kind of theory of everything we're talking about doesn't say anything interesting, particularly about like macroscopic objects about what the weather is gonna be tomorrow or things are happening at this scale. But just what we've discovered is that as you look at the universe, it kind of, you know, if you kind of start breaking, you can start breaking it apart into, and you end up with some fairly simple pieces, quanta if you like, and which are doing, which are interacting in some fairly simple way. And it's, so what we mean by the theory of everything is a theory that describes all the object, all the correct objects you need to describe what's happening in the world and describes how they're interacting with each other at a most fundamental level. How you get from that theory to describing some macroscopic, incredibly complicated thing is there that becomes, again, more of an engineering problem and you may need machine learning or you may, you know, a lot of very different things to do it. Well, I don't even think it's just engineering, it's also science. One thing that I find kind of interesting talking to physicists is a little bit, there's a little bit of hubris. So some of the most brilliant people I know are physicists, both philosophy and just in terms of mathematics, in terms of understanding the world. But there's a kind of either a hubris or what would I call it, like a confidence that if we have a theory of everything, we will understand everything. Like this is the deepest thing to understand. And I would say, and like the rest is details, right? That's the old Rutherford thing. But to me, there's like, this is like a cake or something. There's layers to this thing and each one has a theory of everything. Like at every level from biology, like how life originates, that itself, like complex systems. That in itself is like this gigantic thing that requires a theory of everything. And then there's the, in the space of humans, psychology, like collective intelligence, the way it emerges among species, that feels like a complex system that requires its own theory of everything. On top of that is things like in the computing space, artificial intelligence systems, like that feels like it needs a theory of everything. And it's almost like once we solve, once we come up with a theory of everything that explains the basic laws of physics that gave us the universe, even stuff that's super complex, like how the universe might be able to originate, even explaining something that you're not a big fan of, like multiverses or stuff that we don't have any evidence of yet, still we won't be able to have a strong explanation of why food tastes delicious. Oh yeah, yeah, I know. No, anyway, yeah, I agree completely. I mean, there is something kind of completely wrong with this terminology of theory of everything. It's not, it's really in some sense, very bad term, very hubristic and bad terminology, because it's not, this is explaining, this is a purely kind of reductionist point of view that you're trying to understand a certain very specific kind of things, which in principle, other things emerge from, but to actually understand how anything emerges from this, it can't be understood in terms of this underlying fund wealth theory is gonna be hopeless in terms of kind of telling you what about this, this various emergent behavior. And as you go to different levels of explanation, you're gonna need to develop different, completely different ideas, completely different ways of thinking. And I guess there's a famous kind of Phil Anderson's slogan is that, you know, more is different. It's just, you know, even once you understand how, what a couple of things, if you have a collection of stuff and you understand perfectly well how each thing is interacting with it, with the others, what the whole thing is gonna do is just a completely different problem. And it's just not, and you need completely different ways of thinking about it. What do you think about this? I gotta ask you at a few different attempts at a theory of everything, especially recently. So I've been for many years, a big fan of cellular automata of complex systems. And obviously, because of that, a fan of Stephen Wolfram's work in that space, but he's recently been talking about a theory of everything through his physics project, essentially. What do you think about this kind of discrete theory of everything, like from simple rules and simple objects on the hypographs emerges all of our reality, where time and space are emergent. Basically everything we see around us is emergent. Yeah, I have to say, unfortunately, I've kind of pretty much zero sympathy for that. I mean, I don't, I spent a little time looking at it and I just don't see, it doesn't seem to me to get anywhere. And it really is, just really, really doesn't agree at all with what I'm seeing, this kind of unification of math and physics that I'm kind of talking about around certain kinds of very deep ideas about geometry and stuff. This, if you wanna believe that your things are really coming out of cellular automata at the most fundamental level, you have to believe that everything that I've seen my whole career and as beautiful, powerful ideas, that that's all just kind of a mirage, which just kind of randomly is emerging from these more basic, very, very simple minded things. And you have to give me some serious evidence for that. And I'm saying nothing. So mirage, you don't think there could be a consistency where things like quantum mechanics could emerge from much, much, much smaller, discrete, like computational type systems. I think from the point of view of certain mathematical point of view, quantum mechanics is already mathematically as simple as it gets. It really is a story about really the fundamental objects that you work with. And when you write down a quantum theory are in some form point of view, precisely the fundamental objects at the deepest levels of mathematics that you're working with, they're exactly the same. So, and cellular automata are something completely different which don't fit into these structures. And so I just don't see why. Anyway, I don't see it as a promising thing to do. And then just looking at it and seeing, does this go anywhere? Does this solve any problem that I've ever, that I didn't, does this solve any problem of any kind? I just don't see it. Yeah, to me, cellular automata and these hypergraphs, I'm not sure solving a problem is even the standard to apply here at this moment. To me, the fascinating thing is that the question it asks have no good answers. So there's not good math explaining, forget the physics of it, math explaining the behavior of complex systems. And that to me is both exciting and paralyzing. Like we're at the very early days of understanding, you know, how complicated and fascinating things emerge from simple rules. Yeah, you know, I agree. I think that is a truly great problem. And depending where it goes, it may be, you know, it may start to develop some kind of connections to the things that I've kind of found more fruitful and hard to know. It just, I think a lot of that area, I kind of strongly feel I best not say too much about it because I just, I don't know too much about it. And again, we're back to this original problem that, you know, your time in life is limited. You have to figure out what you're gonna spend your time thinking about. And that's something I just never seen enough to convince me to spend more time thinking about. Well, also timing, it's not just that our time is limited, but the timing of the kind of things you think about, there's some aspect to cellular automata, these kinds of objects that it feels like we're very many years away from having big breakthroughs on. And so it's like, you have to pick the problems that are solvable today. In fact, my intuition, again, perhaps biased, is it feels like the kind of systems that, complex systems that cellular automata are would not be solved by human brains. It feels like, well, like, it feels like something post-human that will solve that problem. Or like significantly enhanced humans, meaning like using computational tools, very powerful computational tools to us, to crack these problems open. That's if our approach to science, our ability to understand science, our ability to understand physics will become more and more computational, or there'll be a whole field that's computational in nature, which currently is not the case. Currently, computation is the thing that sort of assists us in understanding science the way we've been doing it all along. But if there's a whole new, I mean, we're from new kind of science, right? It's a little bit dramatic. But, you know, this, if computers could do science on their own computational systems, perhaps that's the way they would do the science. They would try to understand the cellular automata. And that feels like we're decades away. So perhaps it'll crack open some interesting facets of this physics problem, but it's very far away. So timing is everything. That's perfectly possible. Well, let me ask you then in the space of geometry, I don't know how well you know Eric Weinstein. Quite well, yeah. What are your thoughts about his geometric community and the space of ideas that he's playing with in his proposal for theory or everything? Well, I think that he has, he fundamentally has, I think, the same problems that everybody has had trying to do this. And, you know, they're really versions of the same problem that you try to get unity by putting everything into some bigger structure. So he has to have some other ones that are not so conventional that he's trying to work with. But he has the same problem that even if he can, if he can get a lot farther in terms of having a really well-defined, well-understood, clear picture of these things he's working with, they're really kind of large geometrical structures with many dimensions, many kinds. And I just don't see any way he's gonna have the same problem the string theorists have. How do you get back down to the structures of the standard model and how do you, yeah. So I just, anyway, it's the same. And there's another interesting example of some similar kind of thing is Garrett Leesey's theory of everything. Again, you know, there it's a little bit more specific than Erich's, he's working with this E8. But again, I think all these things found are at the same point that you don't, you know, you create this unity, but then you have no, you don't actually have a good idea how you're gonna get back to the actual, to the objects we've seen. How are you gonna, you create these big symmetries, how are you gonna break them? And, and, and, cause, cause we don't see those symmetries and in the real world and- So ultimately there would need to be a simple process for collapsing it to four dimensions. You'd have to explain, well, yeah. And I forget in his case, but it's not just four dimensions. It's also these, these structures you see in the standard model, there's a, you know, there's certain very small dimensional groups of symmetry. It's all called U1, SU2 and SU3. And the problem with, and this has been a problem since the beginning, almost immediately after 1973, about a year later, two years later, people started talking about grand unified theories. So you take the U1, the SU2 and the SU3, and you put them in together into this bigger structure called the SU5 or SO10. But then you're stuck with this problem that, wait a minute, now how, why does the world not look, why do I not see these SU5 symmetries in the world? I only see these. And so, and I think, you know, those, the kind of thing that Eric and also Garrett and lots of people would try to do, they all kind of found her in that same, in that same way that they don't have, they don't have a good answer to that. Are there lessons, ideas to be learned from theories like that from Garrett Leasey's, from Eric's? I don't know, it depends. I have to confess, I haven't looked that closely at Eric's, I mean, he explained to this to me personally a few times and I've looked a bit at his paper, but it's, again, we're back to the problem of a limited amount of time in life. Yeah, I mean, it's an interesting effect, right? Why don't more physicists look at it? I mean, I'm in this position that somehow, you know, people write me emails for whatever reason, and I work in the space of AI, and so there's a lot of people, perhaps AI is even way more accessible than physics in a certain sense, and so a lot of people write to me with different theories about they have for how to create general intelligence. And it's, again, a little bit of an excuse I say to myself, like, well, I only have a limited amount of time, so that's why I'm not investigating it, but I wonder if there's ideas out there that are still powerful, they're still fascinating, and that I'm missing because I'm dismissing them because they're outside of the sort of the usual process of academic research. Yeah, well, I mean, the same thing pretty much every day in my email, there's somebody who's got a theory or everything about why all of what physicists are doing. Perhaps the most disturbing thing I should say about my being a critic of string theory is when you realize who your fans are, that every day I hear from somebody who says, oh, well, since you don't like string theory, you must, of course, agree with me that this is the right way to think about everything. Oh no, oh no. And, you know, most of these are, you quickly can see, this person doesn't know very much and doesn't know what they're doing, but there's a whole continuum to people who are quite serious physicists and mathematicians who are making a fairly serious attempt to try to do something like Garrett and Eric. And then your problem is, you know, you spend, you do want to try to spend more time looking at it and try to figure out what they're really doing, but then at some point you just realize, wait a minute, you know, for me to really, really understand exactly what's going on here would just take time I just don't have. Yeah, it takes a long time, which is the nice thing about AI is, unlike the kind of physics we're talking about, if your idea is good, that should quite naturally lead to you being able to build a system that's intelligent. So you don't need to get approval from somebody that's saying you have a good idea here. You can just utilize that idea and engineer a system, like naturally leads to engineering. With physics here, if you have a perfect theory that explains everything, that still doesn't obviously lead one to to scientific experiments that can validate that theory and two to like trinkets you can build and sell at a store for $5. You can't make money off of it. So that makes it much more challenging. Well, let me also ask you about something that you found, especially recently appealing, which is Roger Penrose's Twister Theory. What is it? What kind of questions might it allow us to answer? What will the answers look like? It's only in the last couple of years that I really, really kind of come to really, I think to appreciate it and to see how to really, I believe to see how to really do something with it. And I've gotten very excited about that the last year or two. I mean, one way of saying, one idea of Twister Theory is that it's a different way of thinking about what space and time are and about what points in space and time are, but which is very interesting that it only really works in four dimensions. So four dimensions behaves very, very specially unlike other dimensions. And in four dimensions, there is a way of thinking about space and time geometry, as well as just thinking about points in space and time. You can also think about different objects, these so-called twisters. And then when you do that, you end up with a kind of a really interesting insight that you can formulate a theory and you can formulate a very, take a standard theory that we formulate in terms of points of space and time. And you can reformulate in this twister language. And in this twister language, it's the fundamental objects are actually are more kind of the, are actually spheres in some sense, kind of the light cone. So maybe one way to say it, which actually I think is really, is quite amazing is if you ask yourself, what do we know about the world? We have this idea that the world out there is this, all these different points and these points are same. Well, that's kind of a derived quantity. What we really know about the world is when we open our eyes, what do you see? You see a sphere. And that what you're looking at is you're looking at, a sphere is worth a light rays coming into your eyes. And what Penrose says is that, well, what a point in space time is, is that sphere, that sphere of all the light rays coming in. And he says, and you should formulate your, instead of thinking about points, you should think about the space of those spheres, if you like, and formulate the degrees of freedom as physics as living on those spheres, living on. So you're kind of living on your degrees of freedom by living on light ray is not on points. And it's a very different way of thinking about physics. And he and others working with him developed a beautiful mathematical, this beautiful mathematical formalism and a way to go back and forth between our kind of, some aspects of our standard way we write these things down and work in the so-called twister space. And certain things worked out very well, but they ended up, I think kind of stuck by the 80s or 90s that they weren't, it's a little bit like string theory that they, by using these ideas about twisters, they could develop them in different directions and find all sorts of other interesting things, but they were getting, they weren't finding any way of doing that that brought them back to kind of new insights into physics. And my own, I mean, what's kind of gotten me excited really is what I think I have an idea about that I think does actually work that goes more in that direction. And I can go on about that endlessly or tell you a little bit about it, but that's the, I think that that's the one kind of easy to explain insight about twister theory. There are some more technical ones I should, I think it's also very convincing what it tells you about spinners for instance, but that's a more technical. Well, first let's like linger on the spheres and the light cones. You're saying twisted theory allows you to make that the fundamental object with which you're operating. Yeah. How, I mean, first of all, like philosophically that's weird and beautiful. Maybe because it maps, it feels like it moves us so much closer to the way human brains perceive reality. So it's almost like our perception is like, the content of our perception is the fundamental object of reality. That's very appealing. Yeah. Is it mathematically powerful? Is there something you can say, can you say a little bit more about what the heck that even means for, because it's much easier to think about mathematically like a point in space time. Like what does it mean to be operating on the light cone? It uses a kind of mathematics that's relative, that was kind of goes back to the 19th century among mathematicians. It's not, anyway, it's a bit of a long story, but the one problem is that you have to start, it's crucial that you think in terms of complex numbers and not just real numbers. And this, for most people, that makes it harder to, for mathematicians, that's fine. We love doing that. But for most people, that makes it harder to think about. But I think perhaps the most, the way that there is something you can say very specifically about it, in terms of spinners, which I don't know if you wanna, I think at some point you wanna talk. So maybe- What are spinners? Let's start with spinner, because I think that if we can introduce that, then I can say- By the way, twister is spelled with an O, and spinner is spelled with an O as well. Yes, okay. So- In case you wanna Google it and look it up, that's very nice Wikipedia pages as a starting point. I don't know what is a good starting point for twister theory. Well, one thing you say about Penrose, I mean, Penrose is actually a very good writer and also a very good draftsman. He's a draftsman. To the extent this is visualizable, he actually has done some very nice drawings. So, I mean, almost any kind of expository thing you can find him writing is a very good place to start. He's a remarkable person. But the, so spinners are something that independently came out of mathematics and out of physics. And to say where they came out of physics, I mean, what people realized when they started looking at elementary particles like electrons or whatever, that there seemed to be some kind of doubling of the degrees of freedom going on. If you counted what was there in some sense in the way you would expect it. And when you started doing quantum mechanics and started looking at elementary particles, there were seem to be two degrees of freedom. They're not one. And one way of seeing it was that if you put your electron in a strong magnetic field and ask what was the energy of it instead of it having one energy, it would have two energies. There'd be two energy levels. And as you increase magnetic field, the splitting would increase. So, physicists kind of realized that, wait a minute. So we thought when we were doing it, first started doing quantum mechanics, that the way to describe particles was in terms of wave functions. And these wave functions were complex to complex values. Well, if we actually look at particles, that that's not right. They're pairs of complex numbers. They're pairs of complex numbers. So, one of the kind of fundamental, from the physics point of view, the fundamental question is, why are all our kind of fundamental particles described by pairs of complex numbers? It's weird. And then you can ask, well, what happens if you like take an electron and rotate it? So how do things move in this pair of complex numbers? Well, now, if you go back to mathematics, what had been understood in mathematics, some years earlier, not that many years earlier, was that if you ask very, very generally, think about geometry of three dimensions and ask. And if you think about things that are happening in three dimensions in the standard way, everything, the standard way of doing geometry, everything is about vectors, right? So if you've taken any mathematics classes, you probably see vectors at some point. They're just triplets of numbers tell you what a direction is or how far you're going in three dimensional space. And most of everything we teach in most standard courses in mathematics is about vectors and things you build out of vectors. So you express everything about geometry in terms of vectors or how they're changing or how you put two of them together and get planes and whatever. But what had been realized early on is that if you ask very, very generally, what are the things that you can kind of get and consistently think about rotating? And so you ask a technical question, what are the representations of the rotation group? Well, you find that there, one answer is there vectors and everything you build out of vectors. But then people found, but wait a minute, there's also these other things which you can't build out of vectors, but which you can consistently rotate. And they're described by pairs of complex numbers, by two complex numbers, and they're the spinors also. And you can think of spinors in some sense as more fundamental than vectors because you can build vectors out of spinors. You can take two spinors and make a vector, but you can't, if you only have vectors, you can't get spinors. So there in some sense, there's some kind of lower level of geometry beyond what we thought it was, which was kind of spinner geometry. And this is something which even to this day, when we teach graduate courses in geometry, we mostly don't talk about this because it's a bit hard to do correctly. If you start with your whole setup as in terms of vectors, describing things in terms of spinors is a whole different ball game. So, but anyway, it was just this amazing fact that this kind of more fundamental piece of geometry, spinors and what we were actually seeing, if you look at electron are one in the same. So it's, I think it's kind of a mind blowing thing, but it's very uncounterintuitive. What are some weird properties of spinors that are counterintuitive? That there are some things that they do, for instance, if you rotate a spinner around 360 degrees, it doesn't come back towards, it becomes minus what it was. Or so it's anyway, so the way rotations work, there's a kind of a funny sign you have to keep track of in some sense. So they're kind of too valued in another weird way. But there's a, but the fundamental problem is that it's just not, if you're used to visualizing vectors, you just, there's nothing you can do visualizing in terms of vectors that will ever give you a spinner. It just is not gonna ever work. As you were saying that I was visualizing a vector walking along a Mobius strip. And it ends up being upside down. But you're saying that doesn't really capture. So what really captures it, the problem is that it's really, the simplest way to describe it is in terms of two complex numbers. And your problem with two complex numbers is that's four real numbers. So your spinner kind of lies in a four dimensional space. So you, that makes it hard to visualize. And it's crucial that it's not just any four dimensions. It's just, it's actually complex numbers. You're really gonna use the fact that these are two complex numbers. So it is very hard to visualize. But to get back to what I think is mind blowing about twisters is that the, another way of saying this, this idea about talking about spheres, another way of saying the fundamental idea of twister theory is in some sense, the fundamental idea of twister theory is that a point is a two, is a two complex dimensional space. So that every, and that it lives inside, the space that it lies inside is twister space. So in the simplest case, it's four, twister space is four dimensional. And a point in space time is a two complex dimensional subspace of all the four complex dimensions. And as you move around in space time, you're just moving, your planes are just moving around. Okay. And that, and, but then the- It's a plane and a four dimensional space. It's a plane- Complex. Complex plane. So it's two complex dimensions and four complex dimensions. Okay. But then to me, the mind blowing thing about this is this then kind of tautologically answers the question is what is a spinner? Well, a spinner is a point. I mean, the space of spinners at a point is the point. In twister theory, the points are the complex two planes. And you want me to, and you're asking what a spinner is. Well, a spinner, the space of spinners is that two plane. So it's, you know, just your whole definition of what a point in space time was just told you what a spinner was. It's, they're just, it's the same thing. Yeah. Well, we're trying to project that into a three dimensional space and trying to intuit. But you can't. Yeah. So the intuition becomes very difficult, but, but from, if you don't, you not using twister theory, you have to kind of go through a certain fairly complicated rigmarole to even describe spinners to describe electrons. Whereas using twister theory, it's just completely tautological. They're just what you want to describe. The electron is fundamentally the way that you're describing the point in space time already. It's just there. So. Do you have a hope, you mentioned that you've been, you found it appealing recently. Is it just because of certain aspects of its mathematical beauty, or do you actually have a hope that this might lead to a theory of everything? Yeah, I mean, I certainly do have such a hope because what I've found, I think the thing which I've done, which I don't think as far as I can tell, no one had really looked at from this point of view before is, has to do with this question of how do you treat time in your quantum theory? And so there's another long story about how we do quantum theories and about how we treat time in quantum theories, which is a long story. But the short version of it is that what people have found when you try and write down a quantum theory, that it's often a good idea to take your time coordinate, whatever you're using to your time coordinate and multiply it by the square root of minus one and to make it purely imaginary. And so all these formulas which you have in your standard theory, if you do that to those, I mean, those formulas have some very strange behavior and they're kind of singular. If you ask even some simple questions, you have to take very delicate singular limits in order to get the correct answer and you have to take them from the right direction, otherwise it doesn't work. Whereas if you just take time and if you just put a factor of square root of minus one wherever you see the time coordinate, you end up with much simpler formulas which are much better behaved mathematically. And what I hadn't really appreciated until fairly recently is also how dramatically that changes the whole structure of the theory. You end up with a consistent way of talking about these quantum theories, but it has some very different flavor and very different aspects that I hadn't really appreciated. And in particular, the way symmetries act on it is not at all what I originally had expected. And so that's the new thing that I have, or I think gives you something is to do this move which people often think of as just kind of a, kind of a mathematical trick that you're doing to make some formulas work out nicely, but to take that mathematical trick as really fundamental. And it turns out in twister theory allows you to simultaneously talk about your usual time and the time times the square root of minus one, they both fit very nicely into twister theory. And you end up with some structures which look a lot like the standard models. Well, let me ask you about some Nobel prizes. Okay. Do you think there will be, there was a bet between Michio Kaku and somebody else about- John Horgan. John Horgan about, by the way, maybe discover a cool website, longbets.com or.org. Yeah, yeah. Yeah, it's cool. It's cool that you can make a bet with people and then check in 20 years later. That's, I really love it. There's a lot of interesting bets on there. I would love to participate, but it's interesting to see, you know, time flies. Yeah. And you make a bet about what's going to happen 20 years. You don't realize 20 years just goes like this. Yeah. And then you get to face, and you get to wonder like, what was that person, what was I thinking? That person 20 years ago was almost like a different person. What was I thinking back then to think that is interesting? But, so let me ask you this on record. You know, 20 years from now or some number of years from now, do you think there'll be a Nobel prize given for something directly connected to a, first broadly theory of everything? And second, of course, one of the possibilities, one of them, string theory. String theory is definitely not that things have gone. Yeah. So if you were giving financial advice, you would say not to bet on it. No, do not. And even, I actually suspect if you ask string theory as that question, you're going to get few of them saying, I mean, if you'd asked them that question 20 years ago, again, when Kaku was making this bet or whatever, I think some of them would have taken you up on it. But, and certainly back in 1984, a bunch of them would have said, oh, sure, yeah. But now I get the impression that they've, even they realize that things are not looking good for that particular idea. Again, it depends what you mean by string theory, whether maybe the term will evolve to mean something else, which will work out. But yeah, I don't think that's not gonna like it to work out whether something else, I mean, I still think it's relatively unlikely that you'll have any really successful theory or anything. And the main problem is just the, it's become so difficult to do experiments at higher energy that we've really lost this ability to kind of get unexpected input from experiment. And you can, while it may be hard to figure out what people's thinking is gonna be 20 years from now, looking at high energy particle, high energy colliders and their technology, it's actually pretty easy to make a pretty accurate guess what it's gonna look, what you're gonna be doing 20 years from now. And I think actually, I would actually claim that it's pretty clear where you're gonna be 20 years from now and what it's gonna be is you're gonna have the, you're gonna have the LHC, you're gonna have a lot more data and order of magnitude or more data from the LHC, but at the same energy, you're not gonna see a higher energy accelerator operating successfully in the next 20 years. And like maybe machine learning or great sort of data science methodologies that process that data will not reveal any major like shifts in our understanding of the underlying physics, you think? I don't think so. I mean, I think that that field, my understanding is that they're starting to make a great use of those techniques, but it seems to look like it will help them solve certain technical problems and be able to do things somewhat better, but not completely change the way they're looking at things. What do you think about the potential quantum computers simulating quantum mechanical systems and through that, sneak up to sort of through simulation, sneak up to a deep understanding of the fundamental physics? The problem there is that that's promising more for this, for Phil Anderson's problem that if you wanna, there's lots and lots of, if you take, you start putting together lots and lots of things and we think we know they're pair by pair interactions, but what this thing is gonna do, we don't have any good calculational techniques. Quantum computers may very well give you those. And so they may, what we think of as kind of a strong coupling behavior, we have no good way to calculate, even though we can write down the theory, we don't know how to calculate anything with any accuracy and that the quantum computer may solve that problem. But the problem is that they, I don't think that they're gonna solve the problem, that they help you with the problem of not having the, of knowing what the right underlying theory is. As somebody who likes experimental validation, let me ask you the perhaps ridiculous sounding, but I don't think it's actually ridiculous sounding. It's actually a ridiculous question of, do you think we live in a simulation? Do you find that thought experiment at all useful or interesting? Not really, I don't, it just doesn't, yeah, and anyway, to me, it doesn't actually lead to any kind of interesting, lead anywhere interesting. Yeah, to me, so maybe I'll throw a wrench into your thing. To me, it's super interesting from an engineering perspective, so if you look at virtual reality systems, the actual question is, how much computation and how difficult is it to construct a world that, like there are several levels here. One is you won't know the difference, our human perception systems and maybe even the tools of physics won't know the difference between the simulated world and the real world. That's sort of more of a physics question. The most interesting question to me has more to do with why food tastes delicious, which is create how difficult and how much computation is required to construct a simulation where you kind of know it's a simulation at first, but you wanna stay there anyway and over time, you don't even remember. Yeah, well, anyway, I agree these are kind of fascinating questions and they may be very, very relevant to our future as a species, but yeah, they're just very far from anything I think. So from a physics perspective, it's not useful to you to think taking a computational perspective to our universe, thinking of it as an information processing system and then to give it as doing computation and then you think about the resources required to do that kind of computation and all that kind of stuff. You could just look at the basic physics and who cares what the computer it's running on is. Yeah, it just, I mean, the kinds of it, I mean, I'm willing to agree that you can get into interesting kinds of questions going down that road, but they're just so different from anything from what I've found interesting that I just, again, I just have to kind of go back to life is too short and I'm very glad other people are thinking about this, but I just don't see anything I can do with it. What about space itself? So I have to ask you about aliens. Again, something since you emphasize evidence, do you think there is how many, do you think there are and how many intelligent alien civilizations are out there? I have no idea, but I have certainly as far as I know, unless the government's covering it up or something, we haven't heard from, we don't have any evidence for such things yet, but there seems to be no, there's no particular obstruction, why there shouldn't be, so. I mean, do you, you work on some fundamental questions about the physics of reality when you look up to the stars, do you think about whether somebody's looking back at us? Yes, actually, I originally got interested in physics. I actually started out as a kid interested in astronomy, exactly that, telescope and whatever that, and certainly read a lot of science fiction and thought about that. I find over the years, I find myself kind of less and less interested in that one, just because I don't really know what to do with them. I also kind of at some point kind of stopped reading science fiction that much, kind of feeling that there was just too, that the actual science I was kind of learning about was perfectly kind of weird and fascinating and unusual enough and better than any of the stuff that Isaac Asimov, so why should I? Yeah, and you can mess with the science much more than the distant science fiction, the one that exists in our imagination or the one that exists out there among the stars. Well, you mentioned science fiction, you've written quite a few book reviews. I gotta ask you about some books perhaps, if you don't mind. Is there one or two books that you would recommend to others and maybe if you can, what ideas you drew from them? Either negative recommendations or positive recommendations. Do not read this book for sure. Well, I must say, I mean, unfortunately, yeah, well, you can go to my website and you can click on book reviews and you can see I've written, read a lot of, a lot of, I mean, as you can tell from my views about string theory, I'm not a fan of a lot of the kind of popular books about, oh, isn't string theory great? And yes, I'm not a fan of a lot of things that I've written, but I'm not a fan of a lot of things of that kind. Can I ask you a quick question on this, a small tangent? Are you a fan, can you explore the pros and cons of, if I get string theory, sort of science communication, sort of Cosmos style communication of concepts to people that are outside of physics, outside of mathematics, outside of even the sciences and helping people to sort of dream and fill them with all about the full range of mysteries in our universe? That's a complicated issue. You know, I think, you know, I certainly go back and go back to like what inspired me and maybe to connect it a little bit to this question about books. I mean, certainly when the books, some books that I remember reading when I was a kid were about the early history of quantum mechanics, like Heisenberg's books that he wrote about, you know, kind of looking back at telling the history of what happened when he developed quantum mechanics. It's just kind of a totally fascinating, romantic, great story. And those were very inspirational to me. And I would think maybe other people might also find them that, but the- And that's almost like the human story of the development of the ideas. Yeah, the human story. But yeah, just also how, you know, they are these very, very weird ideas that didn't seem to make sense, how they were struggling with them and how, you know, they actually, anyway, it's, I think it's the period of physics kind of beginning, you know, 1905, planning Einstein and ending up with the war when these things are, get used to, you know, make massively destructive weapons. It's just the truly amazing. And so many, so many new ideas. Let me, on another, a tangent on top of a tangent on top of a tangent, ask, if we didn't have Einstein, so how does science progress? Is it the lone geniuses or is it some kind of weird network of ideas swimming in the air and just kind of the geniuses pop up to catch them and others would anyway? Without Einstein, would we have special relativity, general relativity? I mean, it's an interesting case to case base. I mean, special relativity, I think we would have had, I mean, there are other people, anyway, you could even argue that it was already there in some form and some ways, but I think special relativity we would have had without Einstein fairly quickly. General relativity, that was much, much harder thing to do and required a much more effort, much more sophisticated. That I think he would have had sooner or later, but it would have taken quite a bit longer. Other thing- That took a bunch of years to validate scientifically the general relativity. But even for Einstein, from, you know, the point where he had kind of a general idea of what he was trying to do to the point where he actually had a well-defined theory that you could actually compare to the real world, that was, you know, I don't forget the number of, other order of magnitude, 10 years of very serious work. And if he hadn't been around to do that, it would have taken a while before anyone else got around to it. On the other hand, there are things like, with quantum mechanics, you have, you know, Heisenberg and Schrodinger came up with two, which ultimately equivalent, the two different approaches to it, you know, within months of each other. And, you know, so if Heisenberg hadn't been there, he already would have had Schrodinger or whatever. And if neither of them had been there, it would have been somebody else a few months later. So there are times when the, you know, just the, a lot, often it's the combination of, the right ideas are in place and the right experimental data is in place to point in the right direction. And it's just waiting for somebody who's gonna find it. Maybe to go back to your aliens, I guess the one thing that I often wonder about aliens is, would they have the same fundamental physics ideas as we have in mathematics? Would their math, you know, would they, you know, how much is this really intrinsic to our minds? If you start out with a different kind of mind, wouldn't you end up with a different ideas of what fundamental physics is or what the structure of mathematics is? So this is why, like if I was, you know, I like video games, the way I would do it as a curious being, so first experiment I'd like to do is run earth over many thousands of times and see if our particular, no, you know what? I wouldn't do the full evolution. I would start at homo sapiens first and then see the evolution of homo sapiens millions of times and see how the ideas of science would evolve. Like, would you get, like how would physics evolve? How would math evolves? I would particularly just be curious about the notation they come up with. Every once in a while I would like throw miracles at them to like, to mess with them and stuff. And then I would also like to run earth from the very beginning to see if evolution will produce different kinds of brains that would then produce different kinds of mathematics and physics. And then finally, I would probably millions of times run the universe over to see what kind of, what kind of environments and what kind of life would be created to then lead to intelligent life, to then lead to theories of mathematics and physics and to see the full range. And like sort of like Darwin kind of Mark, okay, it took them, what is it? Several hundred million years to come up with calculus. I would just like keep noting how long it took to get an average and see which ideas are difficult, which are not. And then conclusively sort of figure out if it's more collective intelligence or singular intelligence that's responsible for shifts and for big phase shifts and breakthroughs in science. If I was playing a video game and ran, I got a chance to run this whole thing. Yeah, but- We're talking about books before I distract you. That's horrible. Yeah, I'd go back to books and yeah, so, and then, yeah, so that's one thing I'd recommend is the books about the, from the original people, especially Heisenberg about the, how that happened. And there's also a very, very good kind of history of, of the kind of what happened during this 20th century in physics and up to the time of the Standard Model in 1973. It's called the Second Creation by Bob Crease and Mann. That's one of the best ones. I know that's, but the one thing that I can say is that, so that book, I think, forget when it was late 80s, 90s, the problem is that there just hasn't been much that's actually worked out since then. So most of the books that are kind of trying to tell you about all the glorious things that have happened since 1973 are, they're mostly telling you about how glorious things are, which actually don't really work. And it's really, the argument people sometimes make in terms, in favor of these books as well, oh, you know, they're really great because you want to do something that will get kids excited. And then, you know, so they're getting excited about things, something that's not really quite working. It doesn't really matter. The main thing is get them excited. The other argument is, you know, wait a minute. If you're getting people excited about ideas that are wrong, you're really kind of, you're actually kind of discrediting the whole scientific enterprise in a not really good way. So there's these problems. So my general feeling about expository stuff is, yeah, it's to the extent you can do it kind of honestly and well, that's great. There are a lot of people doing that now, but to the extent that you're just trying to get people excited and enthusiastic by kind of telling them stuff which isn't really true, you really shouldn't be doing that. You obviously have a much better intuition about physics. I tend to, in the space of AI, for example, you could use certain kinds of language like calling things intelligent that could rub people the wrong way, but I never had a problem with that kind of thing, you know, saying that a program can learn its way without any human supervision as AlphaZero does to play chess. To me that may not be intelligence, but it sure as heck seems like a few steps down the path towards intelligence. And so like, I think that's a very peculiar property of systems that can be engineered. So even if the idea is fuzzy, even if you're not really sure what intelligence is, or like if you don't have a deep fundamental understanding or even a model what intelligence is, if you build a system that sure as heck is impressive and showing some of the signs of what previously thought impossible for a non-intelligent system, then that's impressive and that's inspiring and that's okay to celebrate. In physics, because you're not engineering anything, you're just now swimming in the space directly when you do theoretical physics, that it could be more dangerous. You could be out too far away from shore. Yeah, well the problem, I think physics is in a, I think it's actually hard for people even to believe or really understand how that this particular kind of physics has gotten itself into a really unusual and strange and historically unusual state, which is not really, I mean, I spent half my life among mathematicians and half of physicists and you know, mathematics is kind of doing fine. People are making progress and it has all the usual problems but also, so you could have a, but I just, I don't know, I've never seen anything at all happening in mathematics like what's happened in this specific area in physics. It's just the kind of sociology of this, the way this field works banging up against this harder problem without anything from experiment to help it. It's really, it's led to some really kind of problematic things and those, so it's one thing to kind of, you know, oversimplify or to slightly misrepresent to try to explain things in a way that's not quite right, but it's another thing to start promoting to people as a success as ideas, which really completely failed. And so, I mean, I've kind of a very, very specific, if you start to have people, I won't name any names, for instance, coming on certain podcasts like yours telling the world, you know, this is a huge success and this is really wonderful and it's just not true. And this is really problematic and it carries a serious danger of, you know, once when people realize that this is what's going on, you know, the loss of credibility of science is a real, real problem for our society. And you don't want people to have an all too good reason to think that what they're being told by kind of some of the best institutions or a country or authorities is not true, you know, it's not true, it's a problem. It's obviously characteristic of not just physics, it's sociology. And it's, I mean, obviously in the space of politics, it's the history of politics is you sell ideas to people even when you don't have any proof that those ideas actually work, you speak as if they've worked and that seems to be the case throughout history. And just like you said, it's human beings running up against a really hard problem. I'm not sure if this is like a particular like trajectory through the progress of physics that we're dealing with now or is it just a natural progress of science. You run up against a really difficult stage of a field and different people that behave differently in the face of that. Some sell books and sort of tell narratives that are beautiful and so on. They're not necessarily grounded in solutions that have proven themselves. Others kind of put their head down quietly, keep doing the work, others sort of pivot to different fields and that's kind of like ants scattering. And then you have fields like machine learning, which there's a few folks mostly scattered away from machine learning in the 90s in the winter of AI, AI winter as they call it. But a few people kept their head down and now they're called the fathers of deep learning. And they didn't think of it that way. And in fact, if there's another AI winter, they'll just probably keep working on it anyway, sort of like loyal ants sticking to a particular thing. So it's interesting, but you're sort of saying that we should be careful over hyping things that have not proven themselves because people will lose trust in the scientific process. But unfortunately, there's been other ways in which people have lost trust in the scientific process that ultimately has to do actually with all the same kind of behaviors you're highlighting, which is not being honest and transparent about the flaws of mistakes of the past. Yeah, I mean, that's always a problem, but this particular field is kind of, it's always a strange one. I mean, I think in the sense that there's a lot of public fascination with it that it's not always a good thing. But there's a lot of fascination with it that it seems to speak to kind of our deepest questions about what is this physical reality, where do we come from and these kind of deep issues. So there's this unusual fascination with it. Mathematics is very different. Nobody's that interested in mathematics. Nobody really kind of expects to learn really great deep things about the world from mathematics that much. They don't ask mathematicians that. So it's a very unusual, it draws this kind of unusual amount of attention. It really is historically in a really unusual state. It's kind of, it's gotten itself way kind of down a blind alley in a way which it's hard to find other historical parallels. But sort of to push back a little bit, there's power to inspiring people. And if I just empirically look, physicists are really good at combining science and philosophy and communicating it. Like there's something about physics often that forces you to build a strong intuition about the way reality works, right? And that allows you to think through sort of and communicate about all kinds of questions. Like if you see physicists, it's always fascinating to take on problems that have nothing to do with their particular discipline. They think in interesting ways and they're able to communicate or think in interesting ways. And so in some sense, they have a responsibility not just to do science, but to inspire. And not responsibility, but the opportunity. And thereby I would say a little bit of a responsibility. Yeah, yeah, and sometimes, but I don't know, anyway, it's hard to say because different, there's many, many people doing this kind of thing with different degrees of success and whatever. I guess one thing, but I mean, what's kind of front and center for me is kind of a more parochial interest is just kind of what damage do you do to the subject itself, ignoring, misrepresenting what high school students think about string theory. And not that it doesn't matter much, but what the smartest undergraduates or the smartest graduate students in the world think about it and what paths you're leading them down or what story you're telling them and what textbooks you're making them read and what they're hearing. And so a lot of what's motivated me is more to try to speak to kind of a specific population of people to make sure that, look, people, it doesn't matter so much what the average person on the street thinks about string theory, but what the best students at Columbia or Harvard or Princeton or whatever who really wanna change work in this field and wanna work that way, what they know about it, what they think about it and that they not be go into the field being misled and believing that a certain story, this is where this is all going, this is what I gotta do, that's important to me. Well, in general, for graduate students, for people who seek to be experts in the field, diversity of ideas is really powerful and is getting into this local pocket of ideas that people hold onto for several decades is not good, no matter what the idea. I would say no matter if the idea is right or wrong, because there's no such thing as right in the longterm, like it's right for now until somebody builds on something much bigger on top of it. It might end up being right, but being a tiny subset of a much bigger thing. So you always should question sort of the ways of the past. Yeah, so how to kind of achieve that kind of diversity of thought and within kind of the sociology of how we organize scientific research is, I know this is one thing that I think it's very interesting that Sabina Hassenfelder is very, it's interesting things to say about it. And I think also Lee Smolin in his book, which is also about that, very much in agreement with them that there's, anyway, there's a really kind of important questions about how research in this field is organized and how people, what can you do to kind of get and get more diversity of thought and get people thinking about a wider range of ideas. At the bottom, I think humility always helps. Well, but the problem is that it's also, it's a combination of humility to know when you're wrong and also, but also you have to have a certain very serious lack of humility to believe that you're gonna make progress on some of these problems. I think you have to have like both modes and switch between them when needed. Let me ask you a question you probably not gonna wanna answer because you're focused on the mathematics of things and mathematics can't answer the why questions, but let me ask you anyway, do you think there's meaning to this whole thing? What do you think is the meaning of life? Why are we here? I don't know, yeah, I was thinking about this. So the, and it did occur to me, what interesting thing about that question is that you don't, yes, I have this life in mathematics and this life in physics and I see some of my physicist colleagues, kind of seem to be, people are often asking them, what's the meaning of life? And they're writing books about the meaning of life and teaching courses about the meaning of life. But then I realized that no one ever asked my mathematician colleagues. Nobody ever asked mathematicians. Yeah, that's funny. So, yeah, everybody just kind of assumes, okay, well, you people are studying about that, I see whatever you're doing, it's maybe very interesting, but it's clearly not gonna tell me anything useful about the meaning of my life. And I'm afraid a lot of my point of view is that if people realized how little difference there was between what the mathematicians are doing and what a lot of these theoretical physicists are doing, they would, they might understand that it's a bit misguided to look for deep insight into the meaning of life from many theoretical physicists. It's not, they, you know, they're people and they may have interesting things to say about this. You're right, they know a lot about physical reality and about, in some sense about metaphysics, about what is real of this kind. But you're also, to my mind, I think you're also making a bit of a mistake that you're looking to, I mean, I'm very, very aware that, you know, I've led a very pleasant and fairly privileged existence of a fairly, without many challenges of different kinds and of a certain kind. And I'm really not, in no way the kind of person that a lot of people were looking for, to try to understand in some sense the meaning of life and the sense of the challenges that they're facing in life. I can't really, I'm really the wrong person for you to be asking about this. Well, if struggle is somehow a thing that's core to meaning, perhaps mathematicians are just quietly the ones who are most equipped to answer that question. If in fact, the creation or at least experiencing beauty is at the core of the meaning of life, because it seems like mathematics is the methodology for which you can most purely explore beautiful things, right? Yeah. So in some sense, maybe we should talk to mathematicians more. Yeah, yeah, maybe, but the, unfortunately, I think people do have a somewhat correct perception that what these people are doing every day or whatever is pretty far removed from anything. Yeah, from what's kind of close to what I do every day and what my typical concerns are. So you may learn something very interesting by talking to mathematicians, but it's probably not gonna be, you're probably not gonna get what you were hoping. So when you put the pen and paper down and you're not thinking about physics and you're not thinking about mathematics and you just get to breathe in the air and look around you and realize that you're going to die one day. Yeah. Do you think about that? Your ideas will live on, but you, the human. Not especially much. Well, certainly I've been getting older. I'm now 64 years old. You start to realize, well, there's probably less ahead than there was behind. And so you start to, that starts to become, what do I think about that? Maybe I should actually get serious about getting some things done, which I may not have, which I may otherwise not have time to do, which I didn't see. This didn't seem to be a problem when I was younger, but that's the main, I think the main way in which that thought occurred. But it doesn't, the stoics are big on this, meditating on mortality helps you more intensely appreciate the beauty when you do experience it. I suppose that's true, but it's not, yeah, it's not something I spend a lot of time trying, but yeah. Day to day, you just enjoy the puzzles and mathematics. Just enjoy, yeah, our life in general, life is, have a perfectly pleasant life and enjoy it. And often think, wow, this is, things are, I'm really enjoying this, things are going well. Yeah, life is pretty amazing. I think you and I are pretty lucky. We get to live on this nice little earth with a nice little comfortable climate. And we get to have this nice little podcast conversation. Thank you so much for spending your valuable time with me today and having this conversation. Thank you. And thank you, thank you. Thank you.
 The following is a conversation with Peter White,
 a theoretical physicist at Columbia,
 outspoken critical string theory,
 and the author of the popular physics and mathematics blog
 called Not Even Wrong.
 This is the Lex Friedman podcast.
 To support it, please check out our sponsors
 in the description.
 And now, here's my conversation with Peter White.
 You're both a physicist and a mathematician.
 So let me ask, what is the difference
 between physics and mathematics?
 Well, there's kind of a conventional understanding
 of the subject that they're two quite different things.
 So that mathematics is about making rigorous statements
 about these abstract things, things of mathematics
 and proving them rigorously.
 And physics is about doing experiments
 and testing various models and that.
 But I think the more interesting thing is that
 there's a wide variety of what people do as mathematics,
 what they do as physics, and there's a significant overlap.
 And that I think is actually a much,
 much very, very interesting area.
 And if you go back kind of far enough in history
 and look at figures like Newton or something,
 I mean, at that point, you can't really tell
 it was Newton, a physicist or a mathematician.
 The mathematicians will tell you he was a mathematician,
 the physicists will tell you he was a physicist.
 But he was a, he's a philosopher.
 Yeah, that's interesting.
 But yeah, anyway, there was kind of no such distinction
 then that's more of a modern thing.
 And but anyway, I think these days
 there's a very interesting space in between the two.
 So in the story of the 20th century
 and the early 21st century, what is the overlap
 between mathematics and physics, would you say?
 Well, I think it's actually become very, very complicated.
 I think it's really interesting to see a lot
 of what my colleagues in the math department are doing.
 They, most of what they're doing,
 they're doing all sorts of different things,
 but most of them have some kind of overlap
 with physics or other.
 So, I mean, I'm personally interested
 in one particular aspect of this overlap,
 which I think has a lot to do with the most fundamental ideas
 about physics and about mathematics.
 But there's just, you kind of see this,
 this really, really everywhere at this point.
 Which particular overlap are you looking at, group theory?
 Yeah, so the, at least what the way it seems to me
 that if you look at physics and look at the,
 our most successful laws of fundamental physics,
 they're really, you know, they have a certain kind
 of mathematical structure.
 It's based upon certain kind of mathematical objects
 and geometry connections and curvature,
 the spinors, the Dirac equation.
 And that these, this very deep mathematics
 provides kind of a unifying set of math,
 of ways of thinking that allow you
 to make a unified theory of physics.
 But the interesting thing is that if you go to mathematics
 and look at what's been going on in mathematics
 the last 1500 years, and even especially recently,
 there's a, similarly, some kind of unifying ideas
 which bring together different areas of mathematics
 which have been especially powerful
 in number theory recently.
 And there's a book, for instance,
 by Edward Frankel about love and math.
 And yeah, that book's great.
 I recommend it highly.
 It's partially accessible.
 But there's a nice audio book that I listened to
 while running an exceptionally long distance,
 like across the San Francisco Bridge.
 And there's something magic about the way he writes about it.
 But some of the group theory in there
 is a little bit difficult.
 Yeah, it's a problem with any of these things
 to kind of really say what's going on
 and make it accessible is very hard.
 He, in this book and elsewhere, I think,
 takes the attitude that kinds of mathematics
 he's interested in and that he's talking about
 are provide kind of a grand unified theory of mathematics.
 They bring together geometry and number theory
 and representation theory, a lot of different ideas
 in a really unexpected way.
 But I think to me, the most fascinating thing
 is if you look at the kind of grand unified theory
 of mathematics he's talking about
 and you look at the physicist kind of ideas
 about unification, it's more or less
 the same mathematical objects are appearing in both.
 So it's this, I think there's a really,
 we're seeing a really strong indication
 that the deepest ideas that we're discovering
 about physics and some of the deepest ideas
 that mathematicians are learning about
 are really, are intimately connected.
 Is there something, like if I was five years old
 and you were trying to explain this to me,
 is there ways to try to sneak up to what this unified world
 of mathematics looks like?
 You said number theory, you said geometry,
 words like topology.
 What does this universe begin to look like?
 Are these, what should we imagine in our mind?
 Is it a three dimensional surface
 and we're trying to say something about it?
 Is it triangles and squares and cubes?
 Like what are we supposed to imagine in our minds?
 Is this natural number?
 What's a good thing to try to,
 for people that don't know any of these tools
 except maybe some basic calculus and geometry
 from high school that they should keep in their minds
 as to the unified world of mathematics
 that also allows us to explore the unified world of physics?
 I mean, what I find kind of remarkable about this
 is the way in which these, we've discovered these ideas,
 but they're actually quite alien
 to our everyday understanding.
 We grow up in this three spatial dimensional world
 and we have intimate understanding
 of certain kinds of geometry and certain kinds of things.
 But these things that we've discovered
 in both math and physics are,
 that they're not at all close,
 have any obvious connection
 to kind of human everyday experience.
 They're really quite different.
 And I can say some of my initial fascination with this
 when I was young and starting to learn about it
 was actually exactly this kind of arcane nature of these things.
 It was a little bit like being told,
 well, there are these kind of semi-mystical experience
 that you can acquire by a long study and whatever,
 except that it was actually true.
 There's actually evidence that this actually works.
 So I'm a little bit wary of trying to give people
 that kind of thing, because I think it's mostly misleading.
 But one thing to say is that,
 geometry is a large part of it.
 And maybe one interesting thing to say very,
 that's about more recent, some of the most recent ideas
 is that when we think about the geometry
 of our space and time, it's kind of three spatial
 and one time dimension.
 It's a physics is in some sense about something
 that's kind of four dimensional in a way.
 And a really interesting thing
 about some of the recent developments
 in number theory have been to realize
 that these ideas that we were looking at
 naturally fit into a context where your theory
 is kind of four dimensional.
 Geometry is a big part of this,
 and we know a lot and feel a lot about
 two, one, two, three dimensional geometry.
 So wait a minute.
 So we can at least rely on the four dimensions
 of space and time and say that we can get pretty far
 by working in those four dimensions.
 I thought you were gonna scare me
 that we're gonna have to go to many, many, many,
 many more dimensions than that.
 My point of view, which goes against a lot of these ideas
 about unification is that no, this is really,
 everything we know about really is about four dimensions
 that you can actually understand a lot of these structures
 that we've been seeing in fundamental physics
 and in number theory, just in terms of four dimensions,
 that it's in some sense, I would claim,
 has been a mistake that physicists have made
 for decades and decades to try to go to higher dimensions,
 to try to formulate a theory in higher dimensions.
 And then you're stuck with the problem,
 how do you get rid of all these extra dimensions
 that you've created?
 And because we only ever see anything in four dimensions.
 That kind of thing leads us astray, you think?
 So creating all these extra dimensions
 just to give yourself extra degrees of freedom.
 Isn't that the process of mathematics
 is to create all of these trajectories for yourself,
 but eventually you have to end up at a final place.
 But it's okay to sort of create abstract objects
 on your path to proving something.
 Yeah, certainly.
 And from a mathematician's point of view,
 I mean, the kinds of,
 mathematicians also are very different than physicists
 in that we like to develop very general theories.
 If we have an idea, we want to see
 what's the greatest generality in which
 you can talk about it.
 So from the point of view of most of the ways
 geometry is formulated by mathematicians,
 it really doesn't matter, it works in any dimension.
 We can do one, two, three, four, any number.
 There's no particular, for most of geometry,
 there's no particular special thing but four.
 But anyway, but what physicists have been trying to do
 over the years is try to understand
 these fundamental theories in a geometrical way.
 And it's very tempting to kind of just start bringing in
 extra dimensions and using them to explain the structure.
 But typically this attempt kind of founders
 because you just don't know,
 you end up not being able to explain why we only see four.
 It is nice in the space of physics
 that like if you look at Fermat's last theorem,
 it's much easier to prove that there's no solution
 for n equals three than it is for the general case.
 And so I guess that's the nice benefit of being a physicist
 is you don't have to worry about the general case
 because we live in a universe with n equals four
 in this case.
 Yeah, physicists are very interested in saying something
 about specific examples.
 And I find that interesting when I'm trying to do things
 in mathematics and I'm trying even teaching courses
 and to mathematics students,
 I find that I'm teaching them in a different way
 than most mathematicians because I'm very often
 very focused on examples on what's kind of the crucial
 example that shows how this powerful new mathematical
 technique, how it works and why you would want to do it.
 And I'm less interested in kind of proving a precise theorem
 about exactly when it's gonna work
 and when it's not gonna work.
 Do you usually think about really simple examples,
 like both for teaching and when you try to solve
 a difficult problem, do you construct like the simplest
 possible examples that captures the fundamentals
 of the problem and try to solve it?
 Yeah, exactly, that's often a really fruitful way
 to if you've got some idea to just kind of try to boil it
 down to what's the simplest situation in which this kind
 of thing is gonna happen and then try to really understand
 that and understand that and that is almost always
 a really good way to get insight into.
 Do you work with paper and pen or like for example,
 for me, coming from the programming side,
 if I look at a model, if I look at some kind
 of mathematical object, I like to mess around with it
 sort of numerically, I just visualize different parts
 of it, visualize however I can so most of the work
 is like neural networks for example,
 is you try to play with the simplest possible example
 and just to build up intuition by, you know,
 any kind of object has a bunch of variables in it.
 You start to mess around with them in different ways
 and visualize in different ways to start to build intuition.
 Or do you go the Einstein route and just imagine
 like everything inside your mind and sort of build
 like thought experiments and then work purely
 on paper and pen?
 Well, the problem with this kind of stuff
 I'm interested in is you rarely can kind of,
 it's rarely something that is really kind of,
 or even the simplest example, you know,
 you can kind of see what's going on by looking
 at something happening in three dimensions.
 There's generally the structures involved are,
 either they're more abstract or if you try to kind of embed
 them in some kind of space and where you could manipulate
 them in some kind of geometrical way,
 it's gonna be a much higher dimensional space.
 So even simple examples, embedding them
 into three dimensional space, you're losing a lot.
 Yeah, but to capture what you're trying to understand
 about them, you have to go to four or more dimensions.
 So it starts to get to be hard to,
 and you can train yourself to try it as much as to kind of
 think about things in your mind.
 And, you know, I often use pad and paper
 and I'm often in my office, I often use the blackboard
 and you are kind of drawing things,
 but they're really kind of more abstract representations
 of how things are supposed to fit together.
 And they're not really, unfortunately,
 not just kind of really living in three dimensions
 where you can...
 Are we supposed to be sad or excited by the fact
 that our human minds can't fully comprehend
 the kind of mathematics you're talking about?
 I mean, what do we make of that?
 I mean, to me, that makes me quite sad.
 It makes it seem like there's a giant mystery out there
 that we'll never truly get to experience directly.
 It is kind of sad how difficult this is.
 I mean, or I would put it a different way that,
 you know, most questions that people have
 about this kind of thing, you know,
 you can give them a really true answer
 and really understand it,
 but the problem is one more of time.
 It's like, yes, you know, I could explain to you
 how this works, but you'd have to be willing
 to sit down with me and, you know, work at this repeatedly
 for, you know, for hours and days and weeks.
 And, I mean, it's just gonna take that long
 for your mind to really wrap itself around what's going on.
 And so that does make things inaccessible,
 which is sad, but I mean, it's just kind of part of life
 that we all have a limited amount of time
 and we have to decide what we're gonna spend our time doing.
 Speaking of a limited amount of time,
 we only have a few hours, maybe a few days together
 here on this podcast.
 Let me ask you the question of amongst many of the ideas
 that you work on in mathematics and physics,
 what's used the most beautiful idea
 or one of the most beautiful ideas, maybe a surprising idea.
 And once again, unfortunately, the way life works,
 we only have a limited time together
 to try to convey such an idea.
 Okay, well, actually, let me just tell you something,
 which I'm tempted to kind of start trying to explain
 what I think is this most powerful idea
 that brings together math and physics,
 ideas about groups and representations
 and how it fits quantum mechanics.
 But in some sense, I wrote a whole textbook about that
 and I don't think we really have time
 to get very far into it.
 Well, can I actually, on a small tangent,
 you did write a paper
 towards a grant unified theory, mathematics and physics.
 Maybe you could step there first,
 what is the key idea in that paper?
 Well, I think we've kind of gone over that.
 I think that the key idea
 is what we were talking about earlier,
 that just kind of a claim that if you look and see
 what's the have been successful ideas of unification
 in physics over the last 50 years or so,
 and what has been happening in mathematics
 and the kind of thing that Frankel's book is about,
 that these are very much the same kind of mathematics.
 And so it's kind of an argument that there really is,
 you shouldn't be looking to unify just math
 or just fundamental physics,
 but taking inspiration for looking for new ideas
 in fundamental physics,
 that they are gonna be in the same direction
 of getting deeper into mathematics
 and looking for more inspiration in mathematics
 from these successful ideas about fundamental physics.
 Could you put words to sort of the disciplines
 we're trying to unify?
 So you said number theory,
 are we literally talking about
 all the major fields of mathematics?
 So it's like the number theory, geometry,
 so the differential geometry, topology.
 Yeah, so the, I mean, one name for this,
 that this is acquired in mathematics
 is the so-called Langlands program.
 And so this started out in mathematics,
 it's that Robert Langlands kind of realized
 that a lot of what people were doing
 and that was starting to be really successful
 in number theory in the 60s.
 And so that this actually was,
 anyway, that this could be a thought of
 in terms of these ideas about symmetry in groups
 and representations and in a way that was also close
 to some ideas about geometry.
 And then more later on in the 80s and 90s,
 there was something called geometric Langlands
 that people realized that you could take
 what people have been doing in number theory in Langlands
 and just forget about the number theory
 and ask what is this telling you about geometry?
 And you get a whole, some new insights
 into certain kinds of geometry that way.
 So it's, anyway, that's kind of the name for this area
 is Langlands and geometric Langlands.
 And just recently in the last few months,
 there's been, there's kind of really major paper
 that appeared by Peter Schultz and Laurent Farg,
 where they made some serious advance
 and try to understand a very much kind of a local problem
 of what happens in number theory near a certain prime number.
 And they turned this into a problem of exactly
 the kind of geometric Langlands people had been doing,
 these kind of pure geometry problem.
 And they found by generalizing the mathematics,
 they could actually reformulate it in that way
 and it worked perfectly well.
 One of the things that makes me sad is,
 I'm a pretty knowledgeable person and then, what is it?
 At least I'm in the neighborhood
 like theoretical computer science, right?
 And it's still way out of my reach.
 And so many people talk about like Langlands, for example,
 is one of the most brilliant people in mathematics
 and just really admire his work.
 And I can't, it's like almost I can't hear the music
 that he composed and it makes me sad.
 Yeah, well, I mean, I think that unfortunately,
 it's not just you, it's I think even most mathematicians
 have no, really don't actually understand
 what this is about them in the group of people
 who really understand all these ideas.
 And so for instance, this paper of Shultz and Farag
 that I was talking about, the number of people
 who really actually understand how that works is anyway,
 who is very, very small.
 And so I think even you find if you talk to mathematicians
 and physicists, even they will often feel that,
 there's this really interesting sounding stuff going on
 and which I should be able to understand.
 It's kind of in my own field.
 I have a PhD in,
 but it still seems pretty clearly far beyond me right now.
 Well, if we can step into the back
 to the question of beauty,
 is there an idea that maybe is a little bit smaller
 that you find beautiful in the space
 of mathematics or physics?
 There's an idea that, I kind of went, got a physics PhD
 and spent a lot of time learning about mathematics.
 And I guess it was embarrassing
 that I hadn't really actually understand
 this very simple idea until I kind of learned it
 when I actually started teaching math classes,
 which is maybe that there's a simple way to explain
 kind of the fundamental way in which algebra
 and geometry are connected.
 So you normally think of geometry is about these spaces
 and these points and you think of algebra
 is this very abstract thing about these abstract objects
 that satisfy certain kinds of relations.
 You can multiply them and add them and do stuff,
 but it's completely abstract.
 It is nothing geometric about it.
 But the kind of really fundamental idea
 is that unifies algebra and geometry
 is to think whenever anybody gives you
 what you call an algebra, some abstract thing
 of things that you can multiply and add,
 that you should ask yourself,
 is that algebra the space of functions on some geometry?
 So one of the most surprising examples of this,
 for instance, is a standard kind of thing
 that seems to have nothing to do with geometry
 is the integers.
 So you can multiply them and add them.
 It's an algebra,
 but it seems to have nothing to do with geometry.
 But if you ask yourself this question and ask,
 is our integers, if somebody gives you an integer,
 can you think of it as a function on some space,
 on some geometry?
 And it turns out that yes, you can.
 And the space is the space of prime numbers.
 And so what you do is you just,
 if somebody gives you an integer,
 you can make a function on the prime numbers
 by just at each prime number,
 taking that integer modulo, that prime.
 So if you say, I don't know, if you get given 10,
 you know, 10, and you ask, what is its value at two?
 Well, it's five times two, so mod two, it's zero.
 So it has zero at one.
 What is its value at three?
 Well, it's nine plus one, so it's one mod three.
 So it's zero at two, it's one at three,
 and you can kind of keep going.
 And so this is really kind of a truly fundamental idea.
 It's at the basis of what's called algebraic geometry,
 and it just links these two parts of mathematics
 that look completely different.
 And it's just an incredibly powerful idea.
 And so much of mathematics emerges
 from this kind of simple relation.
 So you're talking about mapping
 from one discrete space to another.
 So for a second, I thought perhaps mapping
 like a continuous space to a discrete space,
 like functions over a continuous space.
 Yeah.
 Well, I mean, you can take, if somebody gives you a space,
 you can ask, you can say, well, let's,
 and this is also, this is part of the same idea.
 The part of the same idea is that if you try
 and do geometry and somebody tells you, here's a space,
 that what you should do is you should wait to say,
 wait a minute, maybe I should be trying
 to solve this using algebra.
 And so if I do that, the way to start is
 you give me the space, I start to think
 about the functions on the space.
 Okay, so for each point in the space,
 I associate a number.
 I can take different kinds of functions
 and different kinds of values,
 but basically functions on a space.
 So what this insight is telling you is that
 if you're a geometer, often the way to work
 is to change your problem into algebra
 by changing your space, stop thinking about your space
 and the points in it and think about the functions on it.
 Got it.
 And if you're an algebraist
 and you've got these abstract algebraic gadgets
 that you're multiplying and adding, say, wait a minute,
 are those gadgets, can I think of them in some way
 as a function on a space?
 What would that space be?
 And what kind of functions would they be?
 And that going back and forth really brings
 these two completely different looking areas
 of mathematics together.
 Do you have particular examples where it allowed
 to prove some difficult things
 by jumping from one to the other?
 Is that something that's a part of modern mathematics
 where such jumps are made?
 Oh yeah, this is kind of all the time.
 Much of modern number theory is kind of based on this idea.
 But, and when you start doing this,
 you start to realize that you need,
 what simple things on one side of the algebra
 start to require you to think about the other side
 about geometry in a new way.
 You have to kind of get a more sophisticated idea
 about geometry.
 Or if you start thinking about the functions on a space,
 you may need a more sophisticated kind of algebra.
 But in some sense, I mean,
 much or most of modern number theory
 is based upon this move to geometry.
 And there's also a lot of geometry
 and topology is also based upon.
 Yeah, if you wanna understand the topology of something,
 you look at the functions, you do Durham cohomology
 and you get the topology.
 Anyway.
 Well, let me ask you then the ridiculous question.
 You said that this idea is beautiful.
 Can you formalize the definition of the word beautiful?
 And why is this beautiful?
 Like first, why is this beautiful?
 And second, what is beautiful?
 Well, and I think there are many different things
 you can find beautiful for different reasons.
 I mean, I think in this context, the notion of beauty,
 I think really is just kind of,
 an idea is beautiful if it's packages
 a huge amount of kind of power and information
 into something very simple.
 So in some sense, I mean,
 you can almost kind of try and measure it
 in the sense of what are the implications of this idea?
 What non-trivial things does it tell you
 versus how simply can you express the idea?
 So the level of compression,
 what is it, correlates with beauty?
 Yeah, that's one aspect of it.
 And so you can start to tell that an idea
 is becoming uglier and uglier as you start kind of having to,
 it doesn't quite do what you want.
 So you throw in something else to the idea
 and you keep doing that until you get what you want.
 But that's how you know you're doing something uglier
 and uglier when you have to kind of keep adding in
 more into what was originally a fairly simple idea
 and making it more and more complicated
 to get what you want.
 Okay, so let's put some philosophical words on the table
 and try to make some sense of them.
 One word is beauty.
 Another one is simplicity, as you mentioned.
 Another one is truth.
 So do you have a sense, if I give you two theories,
 one is simpler, one is more complicated.
 Do you have a sense of which one is more likely to be true
 to capture deeply the fabric of reality?
 The simple one or the more complicated one?
 Yeah, I think all of our evidence,
 what we see in the history of the subject
 is the simpler one, no.
 Often it's simpler in a surprising way,
 but yeah, that we just don't, we just,
 I think the kind of best theories we've been coming up with
 are ultimately, when properly understood,
 relatively simple and much, much simpler
 than you would expect them to be.
 Do you have a good explanation why that is?
 Is it just because humans want it to be that way?
 Or are we just like ultra biased
 and we just kind of convince ourselves
 that simple is better because we find simplicity beautiful?
 Or is there something about our actual universe
 that at the core is simple?
 My own belief is that there is something about a universe
 that's simple, and as I was trying to say that,
 there is some kind of fundamental thing about math,
 physics, and physics, and all this picture,
 which is in some sense simple.
 It's true that, it's of course true that our minds
 have certain, are very limited and can certainly do
 certain things and not others.
 So it's in principle possible that there's some
 great insight, there are a lot of insights
 into the way the world works,
 which just aren't accessible to us
 because that's not the way our minds work.
 We don't, and that what we're seeing,
 this kind of simplicity is just because that's
 all we ever have any hope of seeing, but.
 So there's a brilliant physicist
 by the name of Sabine Hassenfelder,
 who both agrees and disagrees with you,
 or I suppose agrees that the final answer will be simple.
 But simplicity and beauty leads us astray
 in the local pockets of scientific progress.
 Do you agree with her disagreement,
 do you disagree with her agreement?
 And agree with the agreement, and so on?
 I, yes, I find it was really fascinating reading her book
 and anyway, I was finding disagreeing with a lot,
 but then at the end when she says, yes, when we find,
 when we actually figure this out, it will be simple.
 And okay, so we agree in the end.
 Does beauty lead us astray, which is the core thesis
 of her work in that book?
 I actually, I guess I do disagree with her on that so much.
 I don't think, and especially,
 and I actually fairly strongly disagree with her
 about sometimes the way she'll refer to math.
 And so the problem is, you know,
 physicists and people in general just refer to it as math,
 and they're often meaning not what I would call math,
 which is the interesting ideas of math,
 but just some complicated calculation.
 And so I guess my feeling about it is more that it's very,
 the problem with talking about simplicity
 and using simplicity as a guide is that it's very,
 it's very easy to fool yourself.
 And it's very easy to decide to fall in love with an idea.
 You have an idea, you think, oh, this is great,
 and you fall in love with it.
 And like any kind of love affair,
 it's very easy to believe that the object
 of your affections is much more beautiful
 than the others might think that they really are.
 And that's very, very easy to do.
 So if you say, I'm just gonna pursue ideas
 about beauty and mathematics and this,
 it's extremely easy to just fool yourself, I think.
 And I think that's a lot of what the story
 she was thinking of about where people have gone astray.
 That I think it's, I would argue that as more people,
 it's not that there was some simple, powerful,
 wonderful idea which they'd found,
 and it turned out not to be useful,
 but it was more that they kind of fooled themselves
 that this was actually a better idea than it really was,
 and that it was simpler, more beautiful than it really was,
 is a lot of the story.
 I see, so it's not that the simplicity
 would be Lisa's astray, it's just people are people
 and they fall in love with whatever idea they have.
 And then they weave narratives around that idea,
 or they present in such a way that emphasizes
 the simplicity and the beauty.
 Yeah, that's part of it.
 But the thing about physics that you have
 is that you, what really can tell it,
 if you can do an experiment and check and see
 if nature is really doing what your idea expects,
 that you do in principle have a way of really testing it.
 And it's certainly true that if you thought
 you had a simple idea and that doesn't work,
 and you go out and do an experiment,
 and what actually does work is some more,
 maybe some more complicated version of it,
 that can certainly happen and that can be true.
 I think her emphasis is more that I don't really disagree
 with is that people should be concentrating
 on when they're trying to develop better theories
 on more on self-consistency, not so much on beauty,
 but not is this idea beautiful,
 but is there something about the theory
 which is not quite consistent and use that as a guide,
 that there's something wrong there which needs fixing.
 And so I think that part of her argument,
 I think I was, we're on the same page about.
 What is consistency and inconsistencies?
 What exactly, do you have examples in mind?
 Well, it can be just simple inconsistency
 between theory and experiment that if you,
 so we have this great fundamental theory,
 but there are some things that we see out there
 which don't seem to fit in it like dark energy
 and dark matter for instance.
 But if there's something which you can't test experimentally,
 I think she would argue and I would agree that for instance,
 if you're trying to think about gravity
 and how are you gonna have a quantum theory of gravity,
 you should kind of be, test any of your ideas
 with kind of a thought experiment,
 does this actually give a consistent picture
 of what's gonna happen, of what happens
 in this particular situation or not.
 So this is a good example you've written about this.
 Since quantum gravitational effects are really small,
 super small, arguably unobservably small,
 should we have hope to arrive at a theory
 of quantum gravity somehow?
 What are the different ways we can get there?
 You've mentioned that you're not as interested
 in that effort because basically, yes,
 you cannot have ways to scientifically validate it
 given the tools of today.
 Yeah, I've actually, I've over the years
 certainly spent a lot of time learning about gravity
 and about attempts to quantize it,
 but it hasn't been that much in the past,
 the focus of what I've been thinking about.
 But my feeling was always, as I think,
 and Spina would agree that the,
 one way you can pursue this if you can't do experiments
 is just this kind of search for consistency.
 It can be remarkably hard to come up
 with a completely consistent model of this
 and a way that brings together quantum mechanics
 and general relativity.
 And that's, I think, kind of been the traditional way
 that people who have pursued quantum gravity
 have often pursued, you know,
 we have the best route to finding a consistent theory
 of quantum gravity.
 And string theorists will tell you this,
 other people will tell you it,
 it's kind of what people argue about.
 But the problem with all of that is that you end up,
 the danger is that you end up with,
 that everybody could be successful.
 Everybody's program for how to find
 a theory of quantum gravity, you know,
 ends up with something that is consistent.
 And so, in some sense, you could argue
 this is what happened to the string theorists.
 They solved their problem of finding
 a consistent theory of quantum gravity,
 but they found 10 of the 500 solutions.
 So, you know, if you believe that everything
 that they would like to be true is true, well,
 okay, you've got a theory, but it ends up being
 kind of useless because it's just one of an infinite,
 essentially infinite number of things which you have no way
 to experimentally distinguish.
 And so this is just a depressing situation.
 But I do think that there is a, so again,
 I think pursuing ideas about what, more about beauty
 and how can you integrate and unify these issues
 about gravity with other things we know about physics
 and can you find a theory where these fit together
 in a way that makes sense and hopefully predict something
 that's much more promising.
 Well, it makes sense and hopefully, I mean,
 we'll sneak up onto this question a bunch of times
 because you kind of said a few slightly contradictory
 things which is like, it's nice to have a theory
 that's consistent, but then if the theory is consistent,
 it doesn't necessarily mean anything.
 So like-
 It's not enough, it's not enough.
 It's not enough and that's the problem.
 So it's like, it keeps coming back to, okay,
 there should be some experimental validation.
 So, okay, let's talk a little bit about string theory.
 You've been a bit of an outspoken critic of string theory.
 Maybe one question first to ask is what is string theory?
 And beyond that, why is it wrong?
 Or rather, as the title of your blog says, not even wrong.
 Okay, well, one interesting thing about the current state
 of string theory is that I think, I'd argue,
 it's actually very, very difficult to, at this point,
 to say what string theory means.
 If people say they're a string theorist,
 what they mean and what they're doing is kind of hard,
 it's hard to pin down the meaning of the term.
 But the initial meaning, I think, goes back to,
 there was kind of a series of developments starting in 1984
 in which people felt that they had found a unified theory
 of our so-called standard model of all the standard,
 well-known kind of particle interactions and gravity
 and it all fit together in a quantum theory.
 And that you could do this in a very specific way
 by instead of thinking about having a quantum theory
 of particles moving around in space-time,
 think about quantum theory of kind of one-dimensional loops
 moving around in space-time, so-called strings.
 And so instead of one degree of freedom,
 these have an infinite number of degrees of freedom,
 it's a much more complicated theory.
 But you can imagine, okay, we're gonna quantize this theory
 of loops moving around in space-time.
 And what they found is that you could do this
 and you could fairly, relatively straightforwardly
 make sense of such a quantum theory,
 but only if space and time together were 10-dimensional.
 And so then you had this problem,
 again, the problem I referred to at the beginning of,
 okay, now once you make that move,
 you've got to get rid of six dimensions.
 And so the hope was that you could get rid
 of the six dimensions by making them very small
 and that consistency of the theory would require
 that these six dimensions satisfy
 a very specific condition called being a Calabi-Ao manifold,
 and that we knew very, very few examples of this.
 So what got a lot of people very excited back in 84, 85
 was the hope that you could just take
 this 10-dimensional string theory
 and find one of a limited number of possible ways
 of getting rid of six dimensions by making them small,
 and then you would end up with an effective
 four-dimensional theory, which looked like the real world.
 This was the hope.
 So then there's then a very long story
 about what happened to that hope over the years.
 I mean, I would argue, and part of the point of the book
 and its title was that this ultimately was a failure,
 that you ended up, that this idea just didn't,
 there ended up being just too many ways of doing this,
 and you didn't know how to do this consistently,
 that it was kind of not even wrong in the sense
 that you never could pin it down well enough
 to actually get a real falsifiable prediction out of it
 that would tell you it was wrong,
 but it was kind of in the realm of ideas
 which initially look good, but the more you look at them,
 they just, they don't work out the way you want,
 and they don't actually end up carrying the power
 or that you originally had this vision of.
 And yes, the book title is not even wrong.
 Your blog, your excellent blog title is not even wrong.
 Okay, but there's nevertheless been a lot of excitement
 about string theory through the decades, as you mentioned.
 What are the different flavors of ideas that came,
 like that branched out?
 You mentioned 10 dimensions, you mentioned loops
 with infinite degrees of freedom.
 What other interesting ideas to you
 that kind of emerged from this world?
 Well, yeah, I mean, the problem in talking
 about the whole subject, and part of the reason
 I wrote the book is that it gets very, very complicated.
 I mean, there's a huge amount, you know,
 a lot of people got very interested in this,
 a lot of people worked on it, and in some sense,
 I think what happened is exactly because the idea
 didn't really work, that this caused people
 to, you know, instead of focusing on this one idea
 and digging in and working on that,
 they just kind of kept trying new things.
 And so people, I think, ended up wandering around
 in a very, very rich space of ideas about mathematics
 and physics and discovering, you know,
 all sorts of really interesting things.
 It's just, the problem is there tended
 to be an inverse relationship between how interesting
 and beautiful and fruitful this new idea
 that they were trying to pursue was,
 and how much it looked like the real world.
 So there's a lot of beautiful mathematics came out of it.
 I think one of the most spectacular is what the physicists
 call two-dimensional conformal field theory.
 And so these are basically quantum field theories
 and kind of think of it as one space and one time dimension,
 which, you know, have just this huge amount of symmetry
 and a huge amount of structure,
 which just some totally fantastic mathematics behind it.
 And again, and some of that mathematics
 is exactly also what appears in the Langlands program.
 So a lot of the first interaction between math and physics
 around the Langlands program has been around
 these two-dimensional conformal field theories.
 Is there something you could say
 about what are the major problems are with string theory?
 So like, besides that there's no experimental validation,
 you've written that a big hole in string theory
 has been its perturbative definition.
 Yeah.
 Perhaps that's one, can you explain what that means?
 Well, maybe to begin with, I think the simplest thing
 to say is, you know, the initial idea really was that,
 okay, we have this, instead of what's great
 is we have this thing that only works,
 that's very structured and has to work in a certain way,
 for it to make sense.
 And, but then you ended up in 10 space-time dimensions.
 And so to get back to physics,
 you had to get rid of five of the dimensions,
 six of the dimensions.
 And the bottom line I would say,
 in some sense, it's very simple,
 that what people just discovered is just,
 there's kind of no particularly nice way of doing this,
 there's an infinite number of ways of doing it,
 and you can get whatever you want,
 depending on how you do it.
 So you end up, the whole program of string theory
 and the whole program of starting at 10 dimensions
 and getting to four, just kind of collapses
 out of a lack of any way to kind of get to where you want,
 because you can get anything.
 There'll be the hope around that problem,
 has always been that the standard formulation
 that we have of string theory, which is,
 you can go by the name perturbative,
 but it's kind of, there's a standard way we know
 of given a classical theory of constructing
 quantum theory and working with it, which is,
 this is the so-called perturbation theory,
 that we know how to do, and that by itself
 just doesn't give you any hint as to what to do
 about the six dimensions.
 So actual perturbative string theory by itself
 really only works in 10 dimensions.
 So you have to start making some kinds of assumptions
 about how I'm gonna go beyond this formulation
 that we really understand of string theory
 and get rid of these six dimensions.
 So kind of the simplest one was the Claveau postulate,
 but when that didn't really work out,
 people tried more and more different things,
 and the hope has always been that the solution
 to this problem would be that you would find
 a deeper and better understanding of what string theory is
 that would actually go beyond this perturbative expansion
 and which would generalize this,
 and that once you had that, it would solve this problem of,
 it would pick out what to do with the six dimensions.
 How difficult is this problem?
 So if I could restate the problem,
 it seems like there's a very consistent physical world
 operating in four dimensions,
 and how do you map a consistent physical world
 in 10 dimensions to a consistent physical world
 in four dimensions?
 And how difficult is this problem?
 Is that something you can even answer?
 Just in terms of physics intuition,
 in terms of mathematics,
 mapping from 10 dimensions to four dimensions.
 Well, basically, I mean, you have to get rid
 of the six dimensions.
 So there's kind of two ways of doing it.
 One is what we call compactification.
 You say that there really are 10 dimensions,
 but for whatever reason, six of them are really,
 are so, so small, we can't see them.
 So you basically start out with 10 dimensions
 and what we call, make six of them not go out to infinity,
 but just kind of a finite extent,
 and then make that size go down so small, it's unobservable.
 But that's a math trick.
 So can you also help me build an intuition about
 how rich and interesting the world
 in those six dimensions is?
 So compactification seems to imply that.
 Well, it's not very interesting.
 Well, no, but the problem is that what you learn
 if you start doing mathematics,
 looking at geometry and topology
 and more and more dimensions is that,
 I mean, asking the question,
 like what are all possible six dimensional spaces
 is just, it's kind of an unanswerable question.
 It's just, I mean, it's even kind of technically
 undecidable in some way.
 There are just too many things you can do with all these.
 If you start trying to make one dimensional spaces,
 it's like, well, you've got a line, you can make a circle,
 you can make graphs, you can kind of see what you can do.
 But as you go to higher and higher dimensions,
 there are just so many ways you can put things together
 and get something of that dimensionality.
 And so unless you have some very, very strong principle,
 we're just gonna pick out some very specific ones
 of these six dimensional spaces.
 And there are just too many of them
 and you can get anything you want.
 So if you have 10 dimensions,
 the kind of things that happen,
 say that's actually the way,
 that's actually the fabric of our realities, 10 dimensions.
 There's a limited set of behaviors of objects.
 I don't even know what the right terminology to use
 that can occur within those dimensions, like in reality.
 So what I'm getting at is like,
 is there some consistent constraints?
 So if you have some constraints that map to reality,
 then you can start saying like,
 dimension number seven is kind of boring.
 All the excitement happens in the spatial dimensions,
 one, two, three.
 And time is also kind of boring.
 Some are more exciting than others,
 or we can use our metric of beauty.
 Some dimensions are more beautiful than others.
 Once you have an actual understanding
 of what actually happens in those dimensions
 in our physical world,
 as opposed to sort of all the possible things
 that could happen.
 In some sense, I mean, just the basic fact
 is you need to get rid of them.
 We don't see them.
 So you need to somehow explain them.
 The main thing you're trying to do
 is to explain why we're not seeing them.
 And so you have to come up with some theory
 of these extra dimensions and how they're gonna behave.
 And string theory gives you some ideas about how to do that.
 But the bottom line is where you're trying to go
 with this whole theory you're creating
 is to just make all of its effects essentially unobservable.
 So it's not a really,
 it's an inherently kind of dubious and worrisome thing
 that you're trying to do there.
 Why are you just adding in all this stuff
 and then trying to explain why we don't see it?
 I mean, it just-
 This may be a dumb question,
 but is this an obvious thing to state
 that those six dimensions are unobservable
 or anything beyond four dimensions is unobservable?
 Or do you leave a little door open
 to saying the current tools of physics,
 and obviously our brains aren't unable to observe them,
 but we may need to come up with methodologies
 for observing them.
 So as opposed to collapsing your mathematical theory
 into four dimensions,
 or leaving the door open a little bit too,
 maybe we need to come up with tools
 that actually allow us to directly measure those dimensions.
 Yes, I mean, you can certainly assume
 that we've got model,
 look at models with more dimensions
 and ask what would be observable effects?
 How would we know this?
 And then you go out and do experiments.
 So for instance, you have a,
 like gravitationally you have an inverse square law of forces.
 Okay, if you had more dimensions,
 that inverse square law would change to something else.
 So you can go and start measuring the inverse square law
 and say, okay, inverse square law is working,
 but maybe if I get,
 and it turns out to be actually kind of very, very hard
 to measure gravitational effects
 at even kind of somewhat macroscopic distances
 because they're so small.
 So you can start looking at the inverse square law
 and say, start trying to measure it
 at shorter and shorter distances
 and see if there were extra dimensions
 at those distance scales,
 you would start to see the inverse square law fail.
 And so people look for that.
 And again, you don't see it,
 but you can, I mean, there's all sorts of experiments
 of this kind you can imagine which test
 for effects of extra dimensions
 at different distance scales.
 But none of them, I mean, they all just don't work.
 Nothing yet.
 Nothing yet, but you can say,
 ah, but it's just much, much smaller.
 You can say that.
 Which by the way makes LIGO
 and the detection of gravitational waves
 quite an incredible project.
 Ed Whitten is often brought up
 as one of the most brilliant mathematicians
 and physicists ever.
 What do you make of him and his work on string theory?
 Well, I think he's a truly remarkable figure.
 I've had the pleasure of meeting him first
 when he was a postdoc.
 And I mean, he's a just completely amazing mathematician
 and physicist.
 And he's quite a bit smarter than just about any of us
 and also more hardworking.
 And it's a kind of frightening combination
 to see how much he's been able to do.
 But I would actually argue that his greatest work,
 the things that he's done that have been of
 just this mind blowing significance of giving us,
 I mean, he's completely revolutionized
 some areas of mathematics.
 He's totally revolutionized the way we understand
 the relations between mathematics and physics.
 And most of those, his greatest work
 is stuff that doesn't have,
 has little or nothing to do with string theory.
 I mean, for instance, he, so he was actually one of fields.
 The very strange thing about him in some sense
 is that he doesn't have a Nobel Prize.
 So there's a very large number of people
 who are nowhere near as smart as he is
 and don't work anywhere near as hard
 who have Nobel prizes.
 I think he just had the misfortune of coming into the field
 at a time when things had gotten much, much, much tougher
 and nobody really had, no matter how smart he was,
 it would have been very hard to come up with a new idea
 that was gonna work physically and get you a Nobel Prize.
 But he, you know, he got a Fields Medal
 for a certain work he did in mathematics.
 And that's just completely unheard of, you know,
 for mathematicians to give a Fields Medal
 to someone outside their field in physics is really,
 you know, you wouldn't have before he came around.
 I don't think anybody would have thought
 that was even conceivable.
 So you're saying he came into the field
 of theoretical physics at a time
 when and still to today is you can't get a Nobel Prize
 for purely theoretical work.
 The specific problem of trying to do better
 than the standard, the standard model is just
 this insanely successful thing.
 And it kind of came together in 1973 pretty much.
 And post, and so, and all of the people
 who kind of were involved in that coming together,
 you know, many of them ended up with Nobel prizes for that.
 But if you look post 1973, pretty much,
 it's a little bit more, there's some edge cases if you like,
 but if you look post 1973 at what people have done
 to try to do better than the standard model
 and to get a better, you know, idea,
 it really hasn't, it's been too hard a problem.
 It hasn't worked, the theory's too good.
 And so it's not that other people went out there
 and did it and not him,
 and that they got no prizes for doing it.
 It's like no one really, the kind of thing
 he's been trying to do with string theory
 is not, no one has been able to do since 1973.
 Is there something you can say about the standard model?
 So the four laws of physics that seems to work very well,
 and yet people are striving to do more,
 talking about unification and so on, why?
 What's wrong, what's broken about the standard model?
 Why does it need to be improved?
 I mean, the thing that's gets most attention is gravity,
 that we have trouble.
 So you want to, in some sense, integrate what we know
 about the gravitational force with it
 and have a unified quantum field theory
 that has gravitational interactions also.
 So that's the big problem everybody talks about.
 I mean, but it's also true
 that if you look at the standard model,
 it has these very, very deep, beautiful ideas,
 but there's certain aspects of it that are very,
 that are, let's just say that they're not beautiful.
 They're not, you have to, to make the thing work,
 you have to throw in lots and lots of extra parameters
 at various points.
 And a lot of this has to do with the so-called,
 you know, the so-called Higgs mechanism in the Higgs field,
 that if you look at the theory, it's, everything is,
 if you forget about the Higgs field and what it needs to do,
 the rest of the theory is very, very constrained
 and has very, very few free parameters, really,
 a very small number.
 There's a very small number of parameters
 and a few integers which tell you what the theory is.
 To make this work as a theory of the real world,
 you need a Higgs field and you need to,
 it needs to do something.
 And once you introduce that Higgs field,
 all sorts of parameters make an appearance.
 So now we've got 20 or 30 or whatever parameters
 that are gonna tell you what all the masses of things are
 and what's gonna happen.
 So you've gone from a very tightly constrained thing
 with a couple of parameters to this thing,
 which the minute you put it in,
 you had to add all this extra,
 all these extra parameters to make things work.
 And so that, it may be one argument as well,
 that's just the way the world is.
 And the fact that you don't find that aesthetically pleasing
 is just your problem.
 Maybe we live in a multiverse and those numbers
 are just different in every universe.
 But another reasonable conjecture is just that,
 well, this is just telling us
 that there's something we don't understand
 about what's going on in a deeper way
 which would explain those numbers.
 And there's some kind of deeper idea
 about where the Higgs field comes from and what's going on,
 which we haven't figured out yet.
 And that's what we should look for.
 But to stick on string theory a little bit longer,
 could you play devil's advocate
 and try to argue for string theory,
 why it is something that deserved the effort that it got
 and still, like if you think of it as a flame,
 still should be a little flame that keeps burning.
 Well, I think the most positive argument for it
 is all sorts of new ideas about mathematics
 and about parts of physics really emerged from it.
 So it was very a fruitful source of ideas.
 And I think this is actually one argument
 you'll definitely, which I kind of agree with,
 you'll hear from Witten and from other string theorists
 that this is just such a fruitful and inspiring idea
 and it's led to so many other different things
 coming out of it that there must be something right
 about this.
 Anyway, I think that's probably the strongest thing
 that they've got.
 But you don't think there's aspects to it
 that could be neighboring to a theory
 that does unify everything, to a theory of everything.
 Like it could, it may not be exactly the theory,
 but sticking on it longer might get us closer
 to the theory of everything.
 Well, the problem with it now really is that
 you really don't know what it is now.
 You never, nobody has ever kind of come up
 with this non-perturbative theory.
 So it's become more and more frustrating
 and an odd activity to try to argue with a string theorist
 about string theory because it's become less
 and less well-defined what it is.
 And it's become actually more and more kind of a,
 whether you have this weird phenomenon
 of people calling themselves string theorists
 when they've never actually worked on any theory
 were there any strings anywhere.
 So what has actually happened kind of sociologically
 is that you started out with this fairly
 well-defined proposal and then I would argue
 because that didn't work, people branched out
 in all sorts of directions doing all sorts of things.
 It became farther and farther removed from that.
 And for sociological reasons, the ones who kind of started
 out or now or were trained by the people who worked on that
 have now become this string theorists
 and but it's becoming almost more kind of
 a tribal denominator than a,
 I think it's very hard to know what you're arguing about
 when you're arguing about string theory these days.
 Well, to push back on that a little bit,
 I mean, string theory is just a term, right?
 It doesn't like you could,
 like this is the way language evolves,
 is it could start to represent something more
 than just the theory that involves strings.
 It could represent the effort
 to unify the laws of physics, right?
 At high dimensions with these super tiny objects, right?
 Or something like that.
 I mean, we can sort of put string theory aside.
 So for example, neural networks
 in the space of machine learning,
 there was a time when they were extremely popular,
 they became much, much less popular
 to a point where if you mentioned neural networks,
 you're getting no funding
 and you're not going to be respected at conferences.
 And then once again, neural networks became
 all the rage about 10, 15 years ago,
 and it goes up and down.
 And a lot of people would argue that using terminology
 like machine learning and deep learning
 is often misused over general.
 Everything that works is deep learning,
 everything that doesn't isn't, something like that.
 That's just the way, again,
 we're back to sociological things.
 But I guess what I'm trying to get at is
 if we leave the sociological mess aside,
 do we throw out the baby with the bath water?
 Is there some, besides the side effects of nice ideas
 from the Ed Wittons of the world,
 is there some core truths there that we should stick by
 in the full beautiful mess of a space
 that we call string theory, that people call string theory?
 You're right, it is kind of a common problem
 that how what you call some field changes and evolves
 and in interesting ways as the field changes.
 But I mean, I guess what I would argue
 is the initial understanding of string theory
 that was quite specific, we're talking about a specific idea,
 10 dimensional superstrings compactified in six dimensions.
 That, to my mind, the really bad thing
 that's happened to the subject is that
 it's hard to get people to admit, at least publicly,
 that that was a failure, that this really didn't work.
 And so de facto, what people do is people stop doing that
 and they start doing more interesting things,
 but they keep talking to the public about string theory
 and referring back to that idea
 and using that as kind of the starting point
 and as kind of the place where the whole tribe starts
 and everything else comes from.
 So the problem with this is that having as your initial name
 and what everything points back to,
 something which really didn't work out,
 it kind of makes everybody, it makes everything,
 you've created this potentially very, very interesting field
 with interesting things happening,
 but people in graduate school take courses
 on string theory and everything kind of,
 and this is what you tell the public
 in which you're continually pointing back.
 So you're continually pointing back to this idea
 which never worked out as your guiding inspiration.
 And it really kind of deforms your whole way
 of your hopes of making progress.
 And that's, to me, I think the kind of worst thing
 has happened in this field.
 Okay, sure, so there's a lack of transparency
 and sort of authenticity about communicating
 the things that failed in the past.
 And so you don't have a clear picture
 of like firm ground that you're standing on.
 But again, those are sociological things.
 And there's a bunch of questions I wanna ask you.
 So one, what's your intuition about
 why the original idea failed?
 So what can you say about why you're pretty sure
 it has failed?
 I mean, the initial idea was, as I tried to explain it,
 it was quite seductive in that you could see
 why Witten and others got excited by it.
 It was, at the time it looked like there were only
 a few of these possible clobby-ows that would work.
 And it looked like, okay, we just have to understand
 this very specific model
 and these very specific six dimensional spaces,
 and we're gonna get everything.
 And so it was a very seductive idea.
 But it just, as people work more and more about it,
 it just didn't, they just kind of realized
 that there are just more and more things
 you can do with your six dimensions and you can't,
 and this is just not going to work.
 Meaning like it's, I mean, what was the failure mode here?
 Is you could just have an infinite number of possibilities
 that you could do so you can come up
 with any theory you want.
 You can fit quantum mechanics.
 You can explain gravity.
 You can explain anything you want with it.
 Is that the basic failure mode?
 Yeah, so it's a failure mode of kind of that this idea
 ended up being essentially empty.
 That it just doesn't, ends up not telling you anything
 because it's consistent with just about anything.
 And so, I mean, there's a complex,
 if you try and talk with strength theories about this now,
 I mean, there's an argument,
 there's a long argument over this about whether,
 oh no, no, no, maybe there still are constraints
 coming out of this idea or not.
 Or maybe we live in a multiverse
 and everything is true anyway.
 So you can, there are various ways you can kind of,
 that strength theories have kind of react
 to this kind of argument that I'm making.
 Try to hold onto it.
 What about experimental validation?
 Is that a fair standard to hold before a theory
 of everything that's trying to unify
 quantum mechanics and gravity?
 Yeah, I mean, ultimately to be really convinced
 that, you know, that on some new idea
 that invocation really works, you need some kind of,
 you need to look at the real world
 and see that this is telling you something,
 something true about it.
 I mean, you know, either telling you
 that if you do some experiment and go out and do it,
 you'll get some unexpected result
 and that's the kind of gold standard,
 or it may be just that like all those numbers
 that are, we don't know how to explain,
 it will show you how to calculate them.
 I mean, it can be various kinds of experimental validation,
 but that's certainly ideally what you're looking for.
 How tough is this, do you think,
 for a theory of everything, not just string theory,
 for something that unifies gravity and quantum mechanics?
 So the very big and the very small,
 is this, let me ask it one way,
 is it a physics problem, a math problem,
 or an engineering problem?
 My guess is it's a combination of a physics
 and a math problem that you really need.
 It's not really engineering.
 It's not like there's some kind of well-defined thing
 you can write down and we just don't have enough
 computer power to do the calculation.
 That's not the kind of problem it is at all.
 But the question is, you know,
 what mathematical tools you need
 to properly formulate the problem is unclear.
 So one reasonable conjecture is the way,
 the reason that we haven't had any success yet
 is just that we're missing,
 either we're missing certain physical ideas
 or we're missing certain mathematical tools,
 which are some combination of them,
 which we need to kind of properly formulate the problem
 and see that it has a solution
 that looks like the real world.
 But those you need, I guess you don't,
 but there's a sense that you need both gravity,
 like all the laws of physics
 to be operating on the same level.
 So it feels like you need an object
 like a black hole or something like that
 in order to make predictions about,
 otherwise you're always making predictions
 about this joint phenomena.
 Or can you do that as long as the theory is consistent
 and doesn't have special cases for each of the phenomena?
 Well, your theory should, I mean,
 if your theory is gonna include gravity,
 our current understanding of gravity
 is that you should have,
 there should be black hole states in it,
 you should be able to describe black holes in this theory.
 And just one aspect that people concentrate a lot on
 is just this kind of questions about
 if your theory includes black holes like it's supposed to,
 and it includes quantum mechanics,
 then there's certain kind of paradoxes which come up.
 And so that's been a huge focus of kind of quantum gravity
 where it has been just those paradoxes.
 So stepping outside of string theory,
 can you just say first at a high level,
 what is a theory of everything?
 What is a theory of everything?
 What do we seek to accomplish?
 Well, I mean, this is very much
 a kind of reductionist point of view
 in the sense that, so it's not a theory,
 this is not gonna explain to you anything,
 it doesn't really, this kind of theory
 of everything we're talking about
 doesn't say anything interesting,
 particularly about like macroscopic objects
 about what the weather is gonna be tomorrow
 or things are happening at this scale.
 But just what we've discovered is that as you look at the universe,
 it kind of, you know, if you kind of start breaking,
 you can start breaking it apart into,
 and you end up with some fairly simple pieces,
 quanta if you like, and which are doing,
 which are interacting in some fairly simple way.
 And it's, so what we mean by the theory of everything
 is a theory that describes all the object,
 all the correct objects you need
 to describe what's happening in the world
 and describes how they're interacting with each other
 at a most fundamental level.
 How you get from that theory
 to describing some macroscopic, incredibly complicated thing
 is there that becomes, again, more of an engineering problem
 and you may need machine learning
 or you may, you know, a lot of very different things to do it.
 Well, I don't even think it's just engineering,
 it's also science.
 One thing that I find kind of interesting
 talking to physicists is a little bit,
 there's a little bit of hubris.
 So some of the most brilliant people I know are physicists,
 both philosophy and just in terms of mathematics,
 in terms of understanding the world.
 But there's a kind of either a hubris or what would I call it,
 like a confidence that if we have a theory of everything,
 we will understand everything.
 Like this is the deepest thing to understand.
 And I would say, and like the rest is details, right?
 That's the old Rutherford thing.
 But to me, there's like, this is like a cake or something.
 There's layers to this thing
 and each one has a theory of everything.
 Like at every level from biology,
 like how life originates,
 that itself, like complex systems.
 That in itself is like this gigantic thing
 that requires a theory of everything.
 And then there's the, in the space of humans, psychology,
 like collective intelligence,
 the way it emerges among species,
 that feels like a complex system
 that requires its own theory of everything.
 On top of that is things like in the computing space,
 artificial intelligence systems,
 like that feels like it needs a theory of everything.
 And it's almost like once we solve,
 once we come up with a theory of everything
 that explains the basic laws of physics
 that gave us the universe,
 even stuff that's super complex,
 like how the universe might be able to originate,
 even explaining something that you're not a big fan of,
 like multiverses or stuff
 that we don't have any evidence of yet,
 still we won't be able to have a strong explanation
 of why food tastes delicious.
 Oh yeah, yeah, I know.
 No, anyway, yeah, I agree completely.
 I mean, there is something kind of completely wrong
 with this terminology of theory of everything.
 It's not, it's really in some sense,
 very bad term, very hubristic and bad terminology,
 because it's not, this is explaining,
 this is a purely kind of reductionist point of view
 that you're trying to understand
 a certain very specific kind of things,
 which in principle, other things emerge from,
 but to actually understand how anything emerges from this,
 it can't be understood in terms of
 this underlying fund wealth theory is gonna be hopeless
 in terms of kind of telling you what about this,
 this various emergent behavior.
 And as you go to different levels of explanation,
 you're gonna need to develop different,
 completely different ideas,
 completely different ways of thinking.
 And I guess there's a famous kind of Phil Anderson's slogan
 is that, you know, more is different.
 It's just, you know, even once you understand how,
 what a couple of things,
 if you have a collection of stuff
 and you understand perfectly well
 how each thing is interacting with it, with the others,
 what the whole thing is gonna do
 is just a completely different problem.
 And it's just not,
 and you need completely different ways of thinking about it.
 What do you think about this?
 I gotta ask you at a few different attempts
 at a theory of everything, especially recently.
 So I've been for many years,
 a big fan of cellular automata of complex systems.
 And obviously, because of that,
 a fan of Stephen Wolfram's work in that space,
 but he's recently been talking about a theory of everything
 through his physics project, essentially.
 What do you think about this kind of discrete
 theory of everything,
 like from simple rules and simple objects on the hypographs
 emerges all of our reality,
 where time and space are emergent.
 Basically everything we see around us is emergent.
 Yeah, I have to say, unfortunately,
 I've kind of pretty much zero sympathy for that.
 I mean, I don't,
 I spent a little time looking at it and I just don't see,
 it doesn't seem to me to get anywhere.
 And it really is,
 just really, really doesn't agree at all
 with what I'm seeing,
 this kind of unification of math and physics
 that I'm kind of talking about around certain kinds
 of very deep ideas about geometry and stuff.
 This, if you wanna believe that your things are really
 coming out of cellular automata at the most fundamental level,
 you have to believe that everything
 that I've seen my whole career
 and as beautiful, powerful ideas,
 that that's all just kind of a mirage,
 which just kind of randomly is emerging
 from these more basic, very, very simple minded things.
 And you have to give me some serious evidence for that.
 And I'm saying nothing.
 So mirage, you don't think there could be a consistency
 where things like quantum mechanics could emerge
 from much, much, much smaller, discrete, like computational
 type systems.
 I think from the point of view
 of certain mathematical point of view,
 quantum mechanics is already mathematically
 as simple as it gets.
 It really is a story about really the fundamental objects
 that you work with.
 And when you write down a quantum theory
 are in some form point of view,
 precisely the fundamental objects at the deepest levels
 of mathematics that you're working with,
 they're exactly the same.
 So, and cellular automata are something completely different
 which don't fit into these structures.
 And so I just don't see why.
 Anyway, I don't see it as a promising thing to do.
 And then just looking at it and seeing,
 does this go anywhere?
 Does this solve any problem that I've ever,
 that I didn't, does this solve any problem of any kind?
 I just don't see it.
 Yeah, to me, cellular automata and these hypergraphs,
 I'm not sure solving a problem is even the standard
 to apply here at this moment.
 To me, the fascinating thing is that the question it asks
 have no good answers.
 So there's not good math explaining,
 forget the physics of it,
 math explaining the behavior of complex systems.
 And that to me is both exciting and paralyzing.
 Like we're at the very early days of understanding,
 you know, how complicated and fascinating things emerge
 from simple rules.
 Yeah, you know, I agree.
 I think that is a truly great problem.
 And depending where it goes, it may be,
 you know, it may start to develop some kind of connections
 to the things that I've kind of found more fruitful
 and hard to know.
 It just, I think a lot of that area,
 I kind of strongly feel I best not say too much about it
 because I just, I don't know too much about it.
 And again, we're back to this original problem
 that, you know, your time in life is limited.
 You have to figure out what you're gonna spend
 your time thinking about.
 And that's something I just never seen enough
 to convince me to spend more time thinking about.
 Well, also timing, it's not just that our time is limited,
 but the timing of the kind of things you think about,
 there's some aspect to cellular automata,
 these kinds of objects that it feels like
 we're very many years away
 from having big breakthroughs on.
 And so it's like, you have to pick the problems
 that are solvable today.
 In fact, my intuition, again, perhaps biased,
 is it feels like the kind of systems that,
 complex systems that cellular automata are
 would not be solved by human brains.
 It feels like, well, like,
 it feels like something post-human
 that will solve that problem.
 Or like significantly enhanced humans,
 meaning like using computational tools,
 very powerful computational tools to us,
 to crack these problems open.
 That's if our approach to science,
 our ability to understand science,
 our ability to understand physics
 will become more and more computational,
 or there'll be a whole field that's computational in nature,
 which currently is not the case.
 Currently, computation is the thing that sort of assists us
 in understanding science
 the way we've been doing it all along.
 But if there's a whole new,
 I mean, we're from new kind of science, right?
 It's a little bit dramatic.
 But, you know, this,
 if computers could do science
 on their own computational systems,
 perhaps that's the way they would do the science.
 They would try to understand the cellular automata.
 And that feels like we're decades away.
 So perhaps it'll crack open some interesting facets
 of this physics problem, but it's very far away.
 So timing is everything.
 That's perfectly possible.
 Well, let me ask you then in the space of geometry,
 I don't know how well you know Eric Weinstein.
 Quite well, yeah.
 What are your thoughts about his geometric community
 and the space of ideas that he's playing with
 in his proposal for theory or everything?
 Well, I think that he has,
 he fundamentally has, I think, the same problems
 that everybody has had trying to do this.
 And, you know, they're really versions of the same problem
 that you try to get unity
 by putting everything into some bigger structure.
 So he has to have some other ones
 that are not so conventional that he's trying to work with.
 But he has the same problem that even if he can,
 if he can get a lot farther in terms of having
 a really well-defined, well-understood, clear picture
 of these things he's working with,
 they're really kind of large geometrical structures
 with many dimensions, many kinds.
 And I just don't see any way he's gonna have
 the same problem the string theorists have.
 How do you get back down to the structures
 of the standard model and how do you, yeah.
 So I just, anyway, it's the same.
 And there's another interesting example
 of some similar kind of thing is Garrett Leesey's
 theory of everything.
 Again, you know, there it's a little bit more specific
 than Erich's, he's working with this E8.
 But again, I think all these things found
 are at the same point that you don't,
 you know, you create this unity, but then you have no,
 you don't actually have a good idea
 how you're gonna get back to the actual,
 to the objects we've seen.
 How are you gonna, you create these big symmetries,
 how are you gonna break them?
 And, and, and, cause, cause we don't see those symmetries
 and in the real world and-
 So ultimately there would need to be a simple process
 for collapsing it to four dimensions.
 You'd have to explain, well, yeah.
 And I forget in his case, but it's not just four dimensions.
 It's also these, these structures you see
 in the standard model, there's a, you know,
 there's certain very small dimensional groups of symmetry.
 It's all called U1, SU2 and SU3.
 And the problem with, and this has been a problem
 since the beginning, almost immediately after 1973,
 about a year later, two years later,
 people started talking about grand unified theories.
 So you take the U1, the SU2 and the SU3,
 and you put them in together into this bigger structure
 called the SU5 or SO10.
 But then you're stuck with this problem that,
 wait a minute, now how, why does the world not look,
 why do I not see these SU5 symmetries in the world?
 I only see these.
 And so, and I think, you know, those,
 the kind of thing that Eric and also Garrett
 and lots of people would try to do,
 they all kind of found her in that same,
 in that same way that they don't have,
 they don't have a good answer to that.
 Are there lessons, ideas to be learned from theories
 like that from Garrett Leasey's, from Eric's?
 I don't know, it depends.
 I have to confess, I haven't looked that closely
 at Eric's, I mean, he explained to this to me personally
 a few times and I've looked a bit at his paper,
 but it's, again, we're back to the problem
 of a limited amount of time in life.
 Yeah, I mean, it's an interesting effect, right?
 Why don't more physicists look at it?
 I mean, I'm in this position that somehow,
 you know, people write me emails for whatever reason,
 and I work in the space of AI,
 and so there's a lot of people,
 perhaps AI is even way more accessible than physics
 in a certain sense, and so a lot of people write to me
 with different theories about they have
 for how to create general intelligence.
 And it's, again, a little bit of an excuse
 I say to myself, like, well, I only have
 a limited amount of time, so that's why
 I'm not investigating it, but I wonder if there's ideas
 out there that are still powerful,
 they're still fascinating, and that I'm missing
 because I'm dismissing them because they're outside
 of the sort of the usual process of academic research.
 Yeah, well, I mean, the same thing pretty much every day
 in my email, there's somebody who's got a theory
 or everything about why all of what physicists are doing.
 Perhaps the most disturbing thing I should say
 about my being a critic of string theory
 is when you realize who your fans are,
 that every day I hear from somebody who says,
 oh, well, since you don't like string theory,
 you must, of course, agree with me
 that this is the right way to think about everything.
 Oh no, oh no.
 And, you know, most of these are, you quickly can see,
 this person doesn't know very much
 and doesn't know what they're doing,
 but there's a whole continuum to people
 who are quite serious physicists and mathematicians
 who are making a fairly serious attempt
 to try to do something like Garrett and Eric.
 And then your problem is, you know, you spend,
 you do want to try to spend more time looking at it
 and try to figure out what they're really doing,
 but then at some point you just realize, wait a minute,
 you know, for me to really, really understand
 exactly what's going on here would just take time
 I just don't have.
 Yeah, it takes a long time,
 which is the nice thing about AI is,
 unlike the kind of physics we're talking about,
 if your idea is good, that should quite naturally lead
 to you being able to build a system that's intelligent.
 So you don't need to get approval from somebody
 that's saying you have a good idea here.
 You can just utilize that idea and engineer a system,
 like naturally leads to engineering.
 With physics here, if you have a perfect theory
 that explains everything,
 that still doesn't obviously lead one to
 to scientific experiments that can validate that theory
 and two to like trinkets you can build and sell
 at a store for $5.
 You can't make money off of it.
 So that makes it much more challenging.
 Well, let me also ask you about something that you found,
 especially recently appealing,
 which is Roger Penrose's Twister Theory.
 What is it?
 What kind of questions might it allow us to answer?
 What will the answers look like?
 It's only in the last couple of years
 that I really, really kind of come to really,
 I think to appreciate it and to see how to really,
 I believe to see how to really do something with it.
 And I've gotten very excited about that the last year or two.
 I mean, one way of saying, one idea of Twister Theory
 is that it's a different way of thinking
 about what space and time are
 and about what points in space and time are,
 but which is very interesting
 that it only really works in four dimensions.
 So four dimensions behaves very, very specially
 unlike other dimensions.
 And in four dimensions, there is a way of thinking
 about space and time geometry,
 as well as just thinking about points in space and time.
 You can also think about different objects,
 these so-called twisters.
 And then when you do that,
 you end up with a kind of a really interesting insight
 that you can formulate a theory
 and you can formulate a very, take a standard theory
 that we formulate in terms of points of space and time.
 And you can reformulate in this twister language.
 And in this twister language,
 it's the fundamental objects are actually are more kind of the,
 are actually spheres in some sense, kind of the light cone.
 So maybe one way to say it,
 which actually I think is really, is quite amazing
 is if you ask yourself, what do we know about the world?
 We have this idea that the world out there is this,
 all these different points and these points are same.
 Well, that's kind of a derived quantity.
 What we really know about the world is when we open our eyes,
 what do you see?
 You see a sphere.
 And that what you're looking at is you're looking at,
 a sphere is worth a light rays coming into your eyes.
 And what Penrose says is that,
 well, what a point in space time is, is that sphere,
 that sphere of all the light rays coming in.
 And he says, and you should formulate your,
 instead of thinking about points,
 you should think about the space of those spheres,
 if you like, and formulate the degrees of freedom
 as physics as living on those spheres, living on.
 So you're kind of living on your degrees of freedom
 by living on light ray is not on points.
 And it's a very different way of thinking about physics.
 And he and others working with him developed
 a beautiful mathematical,
 this beautiful mathematical formalism
 and a way to go back and forth between our kind of,
 some aspects of our standard way we write these things down
 and work in the so-called twister space.
 And certain things worked out very well,
 but they ended up, I think kind of stuck by the 80s or 90s
 that they weren't, it's a little bit like string theory
 that they, by using these ideas about twisters,
 they could develop them in different directions
 and find all sorts of other interesting things,
 but they were getting, they weren't finding any way
 of doing that that brought them back
 to kind of new insights into physics.
 And my own, I mean, what's kind of gotten me excited really
 is what I think I have an idea about
 that I think does actually work
 that goes more in that direction.
 And I can go on about that endlessly
 or tell you a little bit about it, but that's the,
 I think that that's the one kind of easy to explain insight
 about twister theory.
 There are some more technical ones I should,
 I think it's also very convincing
 what it tells you about spinners for instance,
 but that's a more technical.
 Well, first let's like linger on the spheres
 and the light cones.
 You're saying twisted theory allows you to make that
 the fundamental object with which you're operating.
 Yeah.
 How, I mean, first of all, like philosophically
 that's weird and beautiful.
 Maybe because it maps, it feels like it moves us
 so much closer to the way human brains perceive reality.
 So it's almost like our perception is like,
 the content of our perception
 is the fundamental object of reality.
 That's very appealing.
 Yeah.
 Is it mathematically powerful?
 Is there something you can say,
 can you say a little bit more about what the heck
 that even means for,
 because it's much easier to think about mathematically
 like a point in space time.
 Like what does it mean to be operating on the light cone?
 It uses a kind of mathematics that's relative,
 that was kind of goes back to the 19th century
 among mathematicians.
 It's not, anyway, it's a bit of a long story,
 but the one problem is that you have to start,
 it's crucial that you think in terms of complex numbers
 and not just real numbers.
 And this, for most people, that makes it harder to,
 for mathematicians, that's fine.
 We love doing that.
 But for most people, that makes it harder to think about.
 But I think perhaps the most,
 the way that there is something you can say
 very specifically about it,
 in terms of spinners, which I don't know if you wanna,
 I think at some point you wanna talk.
 So maybe-
 What are spinners?
 Let's start with spinner,
 because I think that if we can introduce that,
 then I can say-
 By the way, twister is spelled with an O,
 and spinner is spelled with an O as well.
 Yes, okay.
 So-
 In case you wanna Google it and look it up,
 that's very nice Wikipedia pages as a starting point.
 I don't know what is a good starting point for twister theory.
 Well, one thing you say about Penrose,
 I mean, Penrose is actually a very good writer
 and also a very good draftsman.
 He's a draftsman.
 To the extent this is visualizable,
 he actually has done some very nice drawings.
 So, I mean, almost any kind of expository thing
 you can find him writing is a very good place to start.
 He's a remarkable person.
 But the, so spinners are something
 that independently came out of mathematics
 and out of physics.
 And to say where they came out of physics,
 I mean, what people realized when they started looking
 at elementary particles like electrons or whatever,
 that there seemed to be some kind of doubling
 of the degrees of freedom going on.
 If you counted what was there in some sense
 in the way you would expect it.
 And when you started doing quantum mechanics
 and started looking at elementary particles,
 there were seem to be two degrees of freedom.
 They're not one.
 And one way of seeing it was that if you put your electron
 in a strong magnetic field and ask what was the energy of it
 instead of it having one energy, it would have two energies.
 There'd be two energy levels.
 And as you increase magnetic field,
 the splitting would increase.
 So, physicists kind of realized that, wait a minute.
 So we thought when we were doing it,
 first started doing quantum mechanics,
 that the way to describe particles
 was in terms of wave functions.
 And these wave functions were complex to complex values.
 Well, if we actually look at particles, that that's not right.
 They're pairs of complex numbers.
 They're pairs of complex numbers.
 So, one of the kind of fundamental,
 from the physics point of view,
 the fundamental question is,
 why are all our kind of fundamental particles
 described by pairs of complex numbers?
 It's weird.
 And then you can ask, well, what happens
 if you like take an electron and rotate it?
 So how do things move in this pair of complex numbers?
 Well, now, if you go back to mathematics,
 what had been understood in mathematics,
 some years earlier, not that many years earlier,
 was that if you ask very, very generally,
 think about geometry of three dimensions and ask.
 And if you think about things that are happening
 in three dimensions in the standard way,
 everything, the standard way of doing geometry,
 everything is about vectors, right?
 So if you've taken any mathematics classes,
 you probably see vectors at some point.
 They're just triplets of numbers tell you what a direction is
 or how far you're going in three dimensional space.
 And most of everything we teach
 in most standard courses in mathematics
 is about vectors and things you build out of vectors.
 So you express everything about geometry
 in terms of vectors or how they're changing
 or how you put two of them together
 and get planes and whatever.
 But what had been realized early on
 is that if you ask very, very generally,
 what are the things that you can kind of get
 and consistently think about rotating?
 And so you ask a technical question,
 what are the representations of the rotation group?
 Well, you find that there, one answer is there vectors
 and everything you build out of vectors.
 But then people found, but wait a minute,
 there's also these other things
 which you can't build out of vectors,
 but which you can consistently rotate.
 And they're described by pairs of complex numbers,
 by two complex numbers, and they're the spinors also.
 And you can think of spinors in some sense
 as more fundamental than vectors
 because you can build vectors out of spinors.
 You can take two spinors and make a vector,
 but you can't, if you only have vectors,
 you can't get spinors.
 So there in some sense,
 there's some kind of lower level of geometry
 beyond what we thought it was,
 which was kind of spinner geometry.
 And this is something which even to this day,
 when we teach graduate courses in geometry,
 we mostly don't talk about this
 because it's a bit hard to do correctly.
 If you start with your whole setup as in terms of vectors,
 describing things in terms of spinors
 is a whole different ball game.
 So, but anyway, it was just this amazing fact
 that this kind of more fundamental piece of geometry,
 spinors and what we were actually seeing,
 if you look at electron are one in the same.
 So it's, I think it's kind of a mind blowing thing,
 but it's very uncounterintuitive.
 What are some weird properties of spinors
 that are counterintuitive?
 That there are some things that they do, for instance,
 if you rotate a spinner around 360 degrees,
 it doesn't come back towards,
 it becomes minus what it was.
 Or so it's anyway, so the way rotations work,
 there's a kind of a funny sign
 you have to keep track of in some sense.
 So they're kind of too valued in another weird way.
 But there's a, but the fundamental problem is that
 it's just not, if you're used to visualizing vectors,
 you just, there's nothing you can do visualizing
 in terms of vectors that will ever give you a spinner.
 It just is not gonna ever work.
 As you were saying that I was visualizing a vector
 walking along a Mobius strip.
 And it ends up being upside down.
 But you're saying that doesn't really capture.
 So what really captures it, the problem is that it's really,
 the simplest way to describe it
 is in terms of two complex numbers.
 And your problem with two complex numbers
 is that's four real numbers.
 So your spinner kind of lies in a four dimensional space.
 So you, that makes it hard to visualize.
 And it's crucial that it's not just any four dimensions.
 It's just, it's actually complex numbers.
 You're really gonna use the fact that
 these are two complex numbers.
 So it is very hard to visualize.
 But to get back to what I think is mind blowing
 about twisters is that the, another way of saying this,
 this idea about talking about spheres,
 another way of saying the fundamental idea of twister theory
 is in some sense, the fundamental idea of twister theory
 is that a point is a two,
 is a two complex dimensional space.
 So that every, and that it lives inside,
 the space that it lies inside is twister space.
 So in the simplest case, it's four,
 twister space is four dimensional.
 And a point in space time is a two complex dimensional
 subspace of all the four complex dimensions.
 And as you move around in space time, you're just moving,
 your planes are just moving around.
 Okay. And that, and, but then the-
 It's a plane and a four dimensional space.
 It's a plane- Complex.
 Complex plane.
 So it's two complex dimensions and four complex dimensions.
 Okay.
 But then to me, the mind blowing thing about this
 is this then kind of tautologically answers the question
 is what is a spinner?
 Well, a spinner is a point.
 I mean, the space of spinners at a point is the point.
 In twister theory, the points are the complex two planes.
 And you want me to, and you're asking what a spinner is.
 Well, a spinner, the space of spinners is that two plane.
 So it's, you know, just your whole definition
 of what a point in space time was
 just told you what a spinner was.
 It's, they're just, it's the same thing.
 Yeah. Well, we're trying to project that
 into a three dimensional space and trying to intuit.
 But you can't. Yeah.
 So the intuition becomes very difficult, but,
 but from, if you don't, you not using twister theory,
 you have to kind of go through a certain
 fairly complicated rigmarole to even describe spinners
 to describe electrons.
 Whereas using twister theory,
 it's just completely tautological.
 They're just what you want to describe.
 The electron is fundamentally the way
 that you're describing the point in space time already.
 It's just there.
 So.
 Do you have a hope, you mentioned that you've been,
 you found it appealing recently.
 Is it just because of certain aspects
 of its mathematical beauty,
 or do you actually have a hope that this might lead
 to a theory of everything?
 Yeah, I mean, I certainly do have such a hope
 because what I've found, I think the thing which I've done,
 which I don't think as far as I can tell,
 no one had really looked at from this point of view before
 is, has to do with this question of how do you treat time
 in your quantum theory?
 And so there's another long story about how we do
 quantum theories and about how we treat time
 in quantum theories, which is a long story.
 But the short version of it is that what people have found
 when you try and write down a quantum theory,
 that it's often a good idea to take your time coordinate,
 whatever you're using to your time coordinate
 and multiply it by the square root of minus one
 and to make it purely imaginary.
 And so all these formulas which you have
 in your standard theory, if you do that to those,
 I mean, those formulas have some very strange behavior
 and they're kind of singular.
 If you ask even some simple questions,
 you have to take very delicate singular limits
 in order to get the correct answer
 and you have to take them from the right direction,
 otherwise it doesn't work.
 Whereas if you just take time
 and if you just put a factor of square root of minus one
 wherever you see the time coordinate,
 you end up with much simpler formulas
 which are much better behaved mathematically.
 And what I hadn't really appreciated until fairly recently
 is also how dramatically that changes
 the whole structure of the theory.
 You end up with a consistent way of talking
 about these quantum theories,
 but it has some very different flavor
 and very different aspects that I hadn't really appreciated.
 And in particular, the way symmetries act on it
 is not at all what I originally had expected.
 And so that's the new thing that I have,
 or I think gives you something is to do this move
 which people often think of as just kind of a,
 kind of a mathematical trick that you're doing
 to make some formulas work out nicely,
 but to take that mathematical trick as really fundamental.
 And it turns out in twister theory
 allows you to simultaneously talk about your usual time
 and the time times the square root of minus one,
 they both fit very nicely into twister theory.
 And you end up with some structures
 which look a lot like the standard models.
 Well, let me ask you about some Nobel prizes.
 Okay.
 Do you think there will be,
 there was a bet between Michio Kaku and somebody else
 about- John Horgan.
 John Horgan about, by the way,
 maybe discover a cool website, longbets.com or.org.
 Yeah, yeah.
 Yeah, it's cool.
 It's cool that you can make a bet with people
 and then check in 20 years later.
 That's, I really love it.
 There's a lot of interesting bets on there.
 I would love to participate,
 but it's interesting to see, you know, time flies.
 Yeah.
 And you make a bet about what's going to happen 20 years.
 You don't realize 20 years just goes like this.
 Yeah.
 And then you get to face,
 and you get to wonder like, what was that person,
 what was I thinking?
 That person 20 years ago was almost like a different person.
 What was I thinking back then to think that is interesting?
 But, so let me ask you this on record.
 You know, 20 years from now or some number of years from now,
 do you think there'll be a Nobel prize given
 for something directly connected to a,
 first broadly theory of everything?
 And second, of course, one of the possibilities,
 one of them, string theory.
 String theory is definitely not that things have gone.
 Yeah.
 So if you were giving financial advice,
 you would say not to bet on it.
 No, do not.
 And even, I actually suspect if you ask string theory
 as that question, you're going to get few of them saying,
 I mean, if you'd asked them that question 20 years ago,
 again, when Kaku was making this bet or whatever,
 I think some of them would have taken you up on it.
 But, and certainly back in 1984,
 a bunch of them would have said, oh, sure, yeah.
 But now I get the impression that they've,
 even they realize that things are not looking good
 for that particular idea.
 Again, it depends what you mean by string theory,
 whether maybe the term will evolve to mean something else,
 which will work out.
 But yeah, I don't think that's not gonna like it to work out
 whether something else, I mean, I still think
 it's relatively unlikely that you'll have any
 really successful theory or anything.
 And the main problem is just the,
 it's become so difficult to do experiments
 at higher energy that we've really lost this ability
 to kind of get unexpected input from experiment.
 And you can, while it may be hard to figure out
 what people's thinking is gonna be 20 years from now,
 looking at high energy particle, high energy colliders
 and their technology, it's actually pretty easy
 to make a pretty accurate guess what it's gonna look,
 what you're gonna be doing 20 years from now.
 And I think actually, I would actually claim
 that it's pretty clear where you're gonna be 20 years
 from now and what it's gonna be is you're gonna have the,
 you're gonna have the LHC, you're gonna have a lot more data
 and order of magnitude or more data from the LHC,
 but at the same energy, you're not gonna see a higher energy
 accelerator operating successfully in the next 20 years.
 And like maybe machine learning or great sort of data science
 methodologies that process that data will not reveal any
 major like shifts in our understanding
 of the underlying physics, you think?
 I don't think so.
 I mean, I think that that field, my understanding is
 that they're starting to make a great use of those techniques,
 but it seems to look like it will help them
 solve certain technical problems and be able to do things
 somewhat better, but not completely change
 the way they're looking at things.
 What do you think about the potential quantum computers
 simulating quantum mechanical systems and through that,
 sneak up to sort of through simulation,
 sneak up to a deep understanding of the fundamental physics?
 The problem there is that that's promising more for this,
 for Phil Anderson's problem that if you wanna,
 there's lots and lots of, if you take,
 you start putting together lots and lots of things
 and we think we know they're pair by pair interactions,
 but what this thing is gonna do,
 we don't have any good calculational techniques.
 Quantum computers may very well give you those.
 And so they may, what we think of as kind of
 a strong coupling behavior, we have no good way
 to calculate, even though we can write down the theory,
 we don't know how to calculate anything
 with any accuracy and that the quantum computer
 may solve that problem.
 But the problem is that they, I don't think that they're
 gonna solve the problem, that they help you with the problem
 of not having the, of knowing what the right
 underlying theory is.
 As somebody who likes experimental validation,
 let me ask you the perhaps ridiculous sounding,
 but I don't think it's actually ridiculous sounding.
 It's actually a ridiculous question of,
 do you think we live in a simulation?
 Do you find that thought experiment
 at all useful or interesting?
 Not really, I don't, it just doesn't,
 yeah, and anyway, to me, it doesn't actually lead
 to any kind of interesting, lead anywhere interesting.
 Yeah, to me, so maybe I'll throw a wrench into your thing.
 To me, it's super interesting from an engineering
 perspective, so if you look at virtual reality systems,
 the actual question is, how much computation
 and how difficult is it to construct a world that,
 like there are several levels here.
 One is you won't know the difference,
 our human perception systems and maybe even the tools
 of physics won't know the difference between
 the simulated world and the real world.
 That's sort of more of a physics question.
 The most interesting question to me has more to do
 with why food tastes delicious, which is create
 how difficult and how much computation is required
 to construct a simulation where you kind of know
 it's a simulation at first, but you wanna stay there anyway
 and over time, you don't even remember.
 Yeah, well, anyway, I agree these are kind of fascinating
 questions and they may be very, very relevant
 to our future as a species, but yeah, they're just very far
 from anything I think.
 So from a physics perspective, it's not useful to you
 to think taking a computational perspective
 to our universe, thinking of it as an information
 processing system and then to give it as doing computation
 and then you think about the resources required
 to do that kind of computation and all that kind of stuff.
 You could just look at the basic physics and who cares
 what the computer it's running on is.
 Yeah, it just, I mean, the kinds of it, I mean,
 I'm willing to agree that you can get into interesting
 kinds of questions going down that road,
 but they're just so different from anything
 from what I've found interesting that I just, again,
 I just have to kind of go back to life is too short
 and I'm very glad other people are thinking about this,
 but I just don't see anything I can do with it.
 What about space itself?
 So I have to ask you about aliens.
 Again, something since you emphasize evidence,
 do you think there is how many, do you think there are
 and how many intelligent alien civilizations are out there?
 I have no idea, but I have certainly as far as I know,
 unless the government's covering it up or something,
 we haven't heard from, we don't have any evidence
 for such things yet, but there seems to be no,
 there's no particular obstruction,
 why there shouldn't be, so.
 I mean, do you, you work on some fundamental questions
 about the physics of reality when you look up to the stars,
 do you think about whether somebody's looking back at us?
 Yes, actually, I originally got interested in physics.
 I actually started out as a kid interested in astronomy,
 exactly that, telescope and whatever that,
 and certainly read a lot of science fiction
 and thought about that.
 I find over the years, I find myself kind of less
 and less interested in that one,
 just because I don't really know what to do with them.
 I also kind of at some point kind of stopped
 reading science fiction that much,
 kind of feeling that there was just too,
 that the actual science I was kind of learning about
 was perfectly kind of weird and fascinating
 and unusual enough and better than any of the stuff
 that Isaac Asimov, so why should I?
 Yeah, and you can mess with the science
 much more than the distant science fiction,
 the one that exists in our imagination
 or the one that exists out there among the stars.
 Well, you mentioned science fiction,
 you've written quite a few book reviews.
 I gotta ask you about some books perhaps,
 if you don't mind.
 Is there one or two books that you would recommend
 to others and maybe if you can,
 what ideas you drew from them?
 Either negative recommendations or positive recommendations.
 Do not read this book for sure.
 Well, I must say, I mean, unfortunately,
 yeah, well, you can go to my website
 and you can click on book reviews
 and you can see I've written,
 read a lot of, a lot of, I mean,
 as you can tell from my views about string theory,
 I'm not a fan of a lot of the kind of popular books
 about, oh, isn't string theory great?
 And yes, I'm not a fan of a lot of things
 that I've written, but I'm not a fan
 of a lot of things of that kind.
 Can I ask you a quick question on this, a small tangent?
 Are you a fan, can you explore the pros and cons
 of, if I get string theory, sort of science communication,
 sort of Cosmos style communication of concepts
 to people that are outside of physics,
 outside of mathematics, outside of even the sciences
 and helping people to sort of dream
 and fill them with all about the full range
 of mysteries in our universe?
 That's a complicated issue.
 You know, I think, you know, I certainly go back
 and go back to like what inspired me
 and maybe to connect it a little bit
 to this question about books.
 I mean, certainly when the books,
 some books that I remember reading when I was a kid
 were about the early history of quantum mechanics,
 like Heisenberg's books that he wrote about, you know,
 kind of looking back at telling the history
 of what happened when he developed quantum mechanics.
 It's just kind of a totally fascinating,
 romantic, great story.
 And those were very inspirational to me.
 And I would think maybe other people
 might also find them that, but the-
 And that's almost like the human story
 of the development of the ideas.
 Yeah, the human story.
 But yeah, just also how, you know,
 they are these very, very weird ideas
 that didn't seem to make sense,
 how they were struggling with them
 and how, you know, they actually, anyway,
 it's, I think it's the period of physics
 kind of beginning, you know, 1905,
 planning Einstein and ending up with the war
 when these things are, get used to, you know,
 make massively destructive weapons.
 It's just the truly amazing.
 And so many, so many new ideas.
 Let me, on another, a tangent on top of a tangent
 on top of a tangent, ask, if we didn't have Einstein,
 so how does science progress?
 Is it the lone geniuses or is it some kind
 of weird network of ideas swimming in the air
 and just kind of the geniuses pop up to catch them
 and others would anyway?
 Without Einstein, would we have special relativity,
 general relativity?
 I mean, it's an interesting case to case base.
 I mean, special relativity, I think we would have had,
 I mean, there are other people,
 anyway, you could even argue that it was already there
 in some form and some ways, but I think special relativity
 we would have had without Einstein fairly quickly.
 General relativity, that was much, much harder thing to do
 and required a much more effort, much more sophisticated.
 That I think he would have had sooner or later,
 but it would have taken quite a bit longer.
 Other thing-
 That took a bunch of years to validate scientifically
 the general relativity.
 But even for Einstein, from, you know, the point
 where he had kind of a general idea
 of what he was trying to do to the point
 where he actually had a well-defined theory
 that you could actually compare to the real world,
 that was, you know, I don't forget the number of,
 other order of magnitude, 10 years of very serious work.
 And if he hadn't been around to do that,
 it would have taken a while
 before anyone else got around to it.
 On the other hand, there are things like,
 with quantum mechanics, you have, you know,
 Heisenberg and Schrodinger came up with two,
 which ultimately equivalent,
 the two different approaches to it,
 you know, within months of each other.
 And, you know, so if Heisenberg hadn't been there,
 he already would have had Schrodinger or whatever.
 And if neither of them had been there,
 it would have been somebody else a few months later.
 So there are times when the, you know, just the,
 a lot, often it's the combination of,
 the right ideas are in place
 and the right experimental data is in place
 to point in the right direction.
 And it's just waiting for somebody who's gonna find it.
 Maybe to go back to your aliens,
 I guess the one thing that I often wonder about aliens is,
 would they have the same fundamental physics ideas
 as we have in mathematics?
 Would their math, you know, would they, you know,
 how much is this really intrinsic to our minds?
 If you start out with a different kind of mind,
 wouldn't you end up with a different ideas
 of what fundamental physics is
 or what the structure of mathematics is?
 So this is why, like if I was,
 you know, I like video games,
 the way I would do it as a curious being,
 so first experiment I'd like to do is run earth
 over many thousands of times and see if our particular,
 no, you know what?
 I wouldn't do the full evolution.
 I would start at homo sapiens first
 and then see the evolution of homo sapiens millions of times
 and see how the ideas of science would evolve.
 Like, would you get, like how would physics evolve?
 How would math evolves?
 I would particularly just be curious about the notation
 they come up with.
 Every once in a while I would like throw miracles at them
 to like, to mess with them and stuff.
 And then I would also like to run earth
 from the very beginning to see if evolution
 will produce different kinds of brains
 that would then produce different kinds
 of mathematics and physics.
 And then finally, I would probably millions of times
 run the universe over to see what kind of,
 what kind of environments and what kind of life
 would be created to then lead to intelligent life,
 to then lead to theories of mathematics and physics
 and to see the full range.
 And like sort of like Darwin kind of Mark,
 okay, it took them, what is it?
 Several hundred million years to come up with calculus.
 I would just like keep noting how long it took
 to get an average and see which ideas are difficult,
 which are not.
 And then conclusively sort of figure out
 if it's more collective intelligence
 or singular intelligence that's responsible for shifts
 and for big phase shifts and breakthroughs in science.
 If I was playing a video game and ran,
 I got a chance to run this whole thing.
 Yeah, but-
 We're talking about books before I distract you.
 That's horrible.
 Yeah, I'd go back to books and yeah, so,
 and then, yeah, so that's one thing I'd recommend
 is the books about the, from the original people,
 especially Heisenberg about the, how that happened.
 And there's also a very, very good kind of history of,
 of the kind of what happened during this 20th century
 in physics and up to the time of the Standard Model in 1973.
 It's called the Second Creation by Bob Crease and Mann.
 That's one of the best ones.
 I know that's, but the one thing that I can say is that,
 so that book, I think, forget when it was late 80s, 90s,
 the problem is that there just hasn't been much
 that's actually worked out since then.
 So most of the books that are kind of trying to tell you
 about all the glorious things that have happened since 1973
 are, they're mostly telling you about how glorious things
 are, which actually don't really work.
 And it's really, the argument people sometimes make
 in terms, in favor of these books as well,
 oh, you know, they're really great
 because you want to do something that will get kids excited.
 And then, you know, so they're getting excited
 about things, something that's not really quite working.
 It doesn't really matter.
 The main thing is get them excited.
 The other argument is, you know, wait a minute.
 If you're getting people excited about ideas that are wrong,
 you're really kind of, you're actually kind of discrediting
 the whole scientific enterprise in a not really good way.
 So there's these problems.
 So my general feeling about expository stuff is, yeah,
 it's to the extent you can do it kind of honestly
 and well, that's great.
 There are a lot of people doing that now,
 but to the extent that you're just trying to get people
 excited and enthusiastic by kind of telling them stuff
 which isn't really true, you really shouldn't be doing that.
 You obviously have a much better intuition about physics.
 I tend to, in the space of AI, for example,
 you could use certain kinds of language
 like calling things intelligent
 that could rub people the wrong way,
 but I never had a problem with that kind of thing, you know,
 saying that a program can learn its way
 without any human supervision as AlphaZero does
 to play chess.
 To me that may not be intelligence,
 but it sure as heck seems like a few steps down the path
 towards intelligence.
 And so like, I think that's a very peculiar property
 of systems that can be engineered.
 So even if the idea is fuzzy,
 even if you're not really sure what intelligence is,
 or like if you don't have a deep fundamental understanding
 or even a model what intelligence is,
 if you build a system that sure as heck is impressive
 and showing some of the signs
 of what previously thought impossible
 for a non-intelligent system, then that's impressive
 and that's inspiring and that's okay to celebrate.
 In physics, because you're not engineering anything,
 you're just now swimming in the space directly
 when you do theoretical physics,
 that it could be more dangerous.
 You could be out too far away from shore.
 Yeah, well the problem, I think physics is in a,
 I think it's actually hard for people even to believe
 or really understand how that this particular kind
 of physics has gotten itself into a really unusual
 and strange and historically unusual state,
 which is not really, I mean,
 I spent half my life among mathematicians
 and half of physicists and you know,
 mathematics is kind of doing fine.
 People are making progress and it has all the usual problems
 but also, so you could have a,
 but I just, I don't know,
 I've never seen anything at all happening in mathematics
 like what's happened in this specific area in physics.
 It's just the kind of sociology of this,
 the way this field works banging up against this harder
 problem without anything from experiment to help it.
 It's really, it's led to some really kind
 of problematic things and those,
 so it's one thing to kind of, you know, oversimplify
 or to slightly misrepresent to try to explain things
 in a way that's not quite right,
 but it's another thing to start promoting to people
 as a success as ideas, which really completely failed.
 And so, I mean, I've kind of a very, very specific,
 if you start to have people, I won't name any names,
 for instance, coming on certain podcasts
 like yours telling the world, you know,
 this is a huge success and this is really wonderful
 and it's just not true.
 And this is really problematic
 and it carries a serious danger of, you know,
 once when people realize that this is what's going on,
 you know, the loss of credibility of science
 is a real, real problem for our society.
 And you don't want people to have an all too good reason
 to think that what they're being told
 by kind of some of the best institutions
 or a country or authorities is not true, you know,
 it's not true, it's a problem.
 It's obviously characteristic of not just physics,
 it's sociology.
 And it's, I mean, obviously in the space of politics,
 it's the history of politics is you sell ideas to people
 even when you don't have any proof
 that those ideas actually work,
 you speak as if they've worked
 and that seems to be the case throughout history.
 And just like you said, it's human beings running up
 against a really hard problem.
 I'm not sure if this is like a particular like trajectory
 through the progress of physics
 that we're dealing with now
 or is it just a natural progress of science.
 You run up against a really difficult stage of a field
 and different people that behave differently
 in the face of that.
 Some sell books and sort of tell narratives
 that are beautiful and so on.
 They're not necessarily grounded in solutions
 that have proven themselves.
 Others kind of put their head down quietly,
 keep doing the work,
 others sort of pivot to different fields
 and that's kind of like ants scattering.
 And then you have fields like machine learning,
 which there's a few folks mostly scattered away
 from machine learning in the 90s in the winter of AI,
 AI winter as they call it.
 But a few people kept their head down
 and now they're called the fathers of deep learning.
 And they didn't think of it that way.
 And in fact, if there's another AI winter,
 they'll just probably keep working on it anyway,
 sort of like loyal ants sticking to a particular thing.
 So it's interesting, but you're sort of saying
 that we should be careful over hyping things
 that have not proven themselves
 because people will lose trust in the scientific process.
 But unfortunately,
 there's been other ways in which people have lost trust
 in the scientific process that ultimately has to do
 actually with all the same kind of behaviors
 you're highlighting, which is not being honest
 and transparent about the flaws of mistakes of the past.
 Yeah, I mean, that's always a problem,
 but this particular field is kind of,
 it's always a strange one.
 I mean, I think in the sense that
 there's a lot of public fascination with it
 that it's not always a good thing.
 But there's a lot of fascination with it
 that it seems to speak to kind of our deepest questions
 about what is this physical reality,
 where do we come from and these kind of deep issues.
 So there's this unusual fascination with it.
 Mathematics is very different.
 Nobody's that interested in mathematics.
 Nobody really kind of expects to learn really great
 deep things about the world from mathematics that much.
 They don't ask mathematicians that.
 So it's a very unusual,
 it draws this kind of unusual amount of attention.
 It really is historically in a really unusual state.
 It's kind of, it's gotten itself way kind of down
 a blind alley in a way which
 it's hard to find other historical parallels.
 But sort of to push back a little bit,
 there's power to inspiring people.
 And if I just empirically look,
 physicists are really good
 at combining science and philosophy and communicating it.
 Like there's something about physics often
 that forces you to build a strong intuition
 about the way reality works, right?
 And that allows you to think through sort of
 and communicate about all kinds of questions.
 Like if you see physicists, it's always fascinating
 to take on problems that have nothing to do
 with their particular discipline.
 They think in interesting ways
 and they're able to communicate
 or think in interesting ways.
 And so in some sense, they have a responsibility
 not just to do science, but to inspire.
 And not responsibility, but the opportunity.
 And thereby I would say a little bit of a responsibility.
 Yeah, yeah, and sometimes, but I don't know, anyway,
 it's hard to say because different,
 there's many, many people doing this kind of thing
 with different degrees of success and whatever.
 I guess one thing, but I mean,
 what's kind of front and center for me
 is kind of a more parochial interest
 is just kind of what damage do you do to the subject itself,
 ignoring, misrepresenting what high school students
 think about string theory.
 And not that it doesn't matter much,
 but what the smartest undergraduates
 or the smartest graduate students in the world
 think about it and what paths you're leading them down
 or what story you're telling them
 and what textbooks you're making them read
 and what they're hearing.
 And so a lot of what's motivated me is more to try to speak
 to kind of a specific population of people
 to make sure that, look, people,
 it doesn't matter so much what the average person
 on the street thinks about string theory,
 but what the best students at Columbia or Harvard
 or Princeton or whatever who really wanna change
 work in this field and wanna work that way,
 what they know about it, what they think about it
 and that they not be go into the field being misled
 and believing that a certain story,
 this is where this is all going,
 this is what I gotta do, that's important to me.
 Well, in general, for graduate students,
 for people who seek to be experts in the field,
 diversity of ideas is really powerful
 and is getting into this local pocket of ideas
 that people hold onto for several decades is not good,
 no matter what the idea.
 I would say no matter if the idea is right or wrong,
 because there's no such thing as right in the longterm,
 like it's right for now until somebody builds on
 something much bigger on top of it.
 It might end up being right,
 but being a tiny subset of a much bigger thing.
 So you always should question sort of the ways of the past.
 Yeah, so how to kind of achieve
 that kind of diversity of thought
 and within kind of the sociology
 of how we organize scientific research is,
 I know this is one thing that I think it's very interesting
 that Sabina Hassenfelder is very,
 it's interesting things to say about it.
 And I think also Lee Smolin in his book,
 which is also about that,
 very much in agreement with them that there's,
 anyway, there's a really kind of important questions
 about how research in this field is organized
 and how people, what can you do to kind of get
 and get more diversity of thought
 and get people thinking about a wider range of ideas.
 At the bottom, I think humility always helps.
 Well, but the problem is that it's also,
 it's a combination of humility to know when you're wrong
 and also, but also you have to have a certain
 very serious lack of humility to believe
 that you're gonna make progress on some of these problems.
 I think you have to have like both modes
 and switch between them when needed.
 Let me ask you a question
 you probably not gonna wanna answer
 because you're focused on the mathematics of things
 and mathematics can't answer the why questions,
 but let me ask you anyway,
 do you think there's meaning to this whole thing?
 What do you think is the meaning of life?
 Why are we here?
 I don't know, yeah, I was thinking about this.
 So the, and it did occur to me,
 what interesting thing about that question
 is that you don't,
 yes, I have this life in mathematics
 and this life in physics
 and I see some of my physicist colleagues,
 kind of seem to be, people are often asking them,
 what's the meaning of life?
 And they're writing books about the meaning of life
 and teaching courses about the meaning of life.
 But then I realized that no one ever asked
 my mathematician colleagues.
 Nobody ever asked mathematicians.
 Yeah, that's funny.
 So, yeah, everybody just kind of assumes,
 okay, well, you people are studying about that,
 I see whatever you're doing,
 it's maybe very interesting,
 but it's clearly not gonna tell me anything useful
 about the meaning of my life.
 And I'm afraid a lot of my point of view
 is that if people realized how little difference there was
 between what the mathematicians are doing
 and what a lot of these theoretical physicists are doing,
 they would, they might understand that it's a bit misguided
 to look for deep insight into the meaning of life
 from many theoretical physicists.
 It's not, they, you know, they're people
 and they may have interesting things to say about this.
 You're right, they know a lot about physical reality
 and about, in some sense about metaphysics,
 about what is real of this kind.
 But you're also, to my mind,
 I think you're also making a bit of a mistake
 that you're looking to, I mean, I'm very, very aware
 that, you know, I've led a very pleasant
 and fairly privileged existence of a fairly,
 without many challenges of different kinds
 and of a certain kind.
 And I'm really not, in no way the kind of person
 that a lot of people were looking for,
 to try to understand in some sense the meaning of life
 and the sense of the challenges that they're facing in life.
 I can't really, I'm really the wrong person
 for you to be asking about this.
 Well, if struggle is somehow a thing that's core to meaning,
 perhaps mathematicians are just quietly the ones
 who are most equipped to answer that question.
 If in fact, the creation or at least experiencing beauty
 is at the core of the meaning of life,
 because it seems like mathematics is the methodology
 for which you can most purely explore beautiful things,
 right? Yeah.
 So in some sense, maybe we should talk
 to mathematicians more.
 Yeah, yeah, maybe, but the, unfortunately,
 I think people do have a somewhat correct perception
 that what these people are doing every day
 or whatever is pretty far removed from anything.
 Yeah, from what's kind of close to what I do every day
 and what my typical concerns are.
 So you may learn something very interesting
 by talking to mathematicians,
 but it's probably not gonna be,
 you're probably not gonna get what you were hoping.
 So when you put the pen and paper down
 and you're not thinking about physics
 and you're not thinking about mathematics
 and you just get to breathe in the air and look around you
 and realize that you're going to die one day.
 Yeah. Do you think about that?
 Your ideas will live on, but you, the human.
 Not especially much.
 Well, certainly I've been getting older.
 I'm now 64 years old.
 You start to realize, well, there's probably less ahead
 than there was behind.
 And so you start to, that starts to become,
 what do I think about that?
 Maybe I should actually get serious
 about getting some things done,
 which I may not have, which I may otherwise
 not have time to do, which I didn't see.
 This didn't seem to be a problem when I was younger,
 but that's the main, I think the main way
 in which that thought occurred.
 But it doesn't, the stoics are big on this,
 meditating on mortality helps you more intensely
 appreciate the beauty when you do experience it.
 I suppose that's true, but it's not, yeah,
 it's not something I spend a lot of time trying, but yeah.
 Day to day, you just enjoy the puzzles and mathematics.
 Just enjoy, yeah, our life in general, life is,
 have a perfectly pleasant life and enjoy it.
 And often think, wow, this is, things are,
 I'm really enjoying this, things are going well.
 Yeah, life is pretty amazing.
 I think you and I are pretty lucky.
 We get to live on this nice little earth
 with a nice little comfortable climate.
 And we get to have this nice little podcast conversation.
 Thank you so much for spending your valuable time
 with me today and having this conversation.
 Thank you.
 And thank you, thank you.
 Thank you.