#246 – Peter Woit: Theories of Everything and Why String Theory is Not Even Wrong

[0] The following is a conversation with Peter Waite, a theoretical physicist, the Columbia, outspoken critical string theory, and the author of the popular physics and mathematics blog called Not Even Wrong.

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[77] This is the Lex Friedman podcast, and here is my conversation with Peter White.

[78] You're both a physicist and a mathematician.

[79] So let me ask, what is the difference between physics and mathematics?

[80] Well, there's kind of a conventional understanding of the subject that they're two, you know, quite different things, so that mathematics is about, you know, making rigorous statements about these abstract, you know, abstract things, things of mathematics and proving them rigorously, and physics is about, you know, doing experiments and testing various models and that.

[81] But I think the more interesting thing is, that there's a wide variety of what people do as mathematics, what they do is physics, and there's a significant overlap, and that I think is actually a much, much, very, very interesting area.

[82] 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, you know, was Newton a physicist or a mathematician?

[83] The mathematicians will tell you as a mathematician, the physicist will tell you as a physicist.

[84] But he will say he's a philosopher.

[85] yeah that's that's interesting but uh yeah anyway there there was kind of no such distinction than it'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 in 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 and 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.

[86] 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.

[87] But there's just, you kind of see this, this, really, really everywhere at this point.

[88] Which particular overlap are you looking at group theory?

[89] yeah so the um at least what the way it seems to me that if you look at physics and look at the our most successful um 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 spinners the derog equation and uh that these this very deep mathematics provides kind of a unifying set of math of ways that of thinking that allow you to make a unified theory of physics.

[90] But the interesting thing is that if you go to mathematics and look at what's been going on in mathematics the last 50 hundred 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.

[91] And there's a book, for instance, by Edward Frankel about love and math.

[92] Oh, yeah, that book's great.

[93] I recommend it highly.

[94] It's partially accessible.

[95] There's a nice audiobook that I listened to while running an exceptionally long distance, like across the San Francisco Bridge.

[96] And there's something magic about the way he writes about it.

[97] But some of the group theory in there is a little bit difficult.

[98] Yeah.

[99] It's a problem with any of these things, to kind of really say what's going on and make accessible is very hard.

[100] He, in this book and elsewhere, I think, you know, 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.

[101] They bring together geometry and number theory and representation theory, a lot of different ideas in a really unexpected way.

[102] 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's kind of ideas about unification, it's more or less the same mathematical objects are appearing in both.

[103] So it's this, I think there's a really, we're seeing a really strong indication that, you know, the deepest ideas that we're discovering about physics and some of the deepest ideas that mathematicians are learning about are really, are, you know, intimately connected.

[104] 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?

[105] 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 what are we supposed to imagine our minds is this natural number what 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.

[106] I mean, what I find kind of remarkable about this is the way in which we've discovered these ideas, but they're actually quite alien to our everyday understanding.

[107] You know, we grow up in this three -spatial -dimensional world and we have intimate understanding of certain kinds of geometry and certain kinds of things.

[108] 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.

[109] They're really quite different.

[110] 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.

[111] 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.

[112] There's actually evidence that this actually works.

[113] So I'm a little bit wary of trying to give people that kind of thing, because I think it's mostly misleading.

[114] But one thing to say is that, you know, that geometry is a large part of it.

[115] And maybe one interesting thing to say very, that's about more recent.

[116] 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.

[117] It's a physics is in some sense about something that's kind of four -dimensional in a way.

[118] And a really interesting thing about some of the recent developments and 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.

[119] So geometry is a big part of this, and we know a lot and feel a lot about, you know, two, one, two, three -dimensional geometry.

[120] So wait a minute.

[121] So we can at least rely on the four dimensions of space and time and say that we can get pretty far by working that in those four dimensions.

[122] I thought you were going to scare me that we're going to have to go to many, many, many, many more dimensions than that.

[123] 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, and 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 kind of, it's in some sense I would claim has been a really, has been kind of 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 of how do you get rid of all these extra dimensions that you've created, because we only ever see anything in four dimensions.

[124] That kind of thing leads us astray, you think?

[125] So creating all these extra dimensions just to give yourself extra degrees of freedom.

[126] Yeah.

[127] Isn't that the process of mathematics, is to create all these trajectories for yourself, but eventually you have to end up at a final place, but it's okay to, it's okay to sort of create abstract objects on your path to proving something.

[128] Yeah, certainly, but from the mathematicians' point of view, I mean, the kinds of, mathematicians also are very different than physicists, and that we like to develop very general theories.

[129] We like to, if we have an idea, we want to see what's the greatest generality in which you can talk about it.

[130] So from the point of view of most of the ways geometry is formulated by mathematicians, it really doesn't matter.

[131] It works in any dimension.

[132] We can do one, two, three, four, any number.

[133] There's no particular, for most of geometry, there's no particular special thing about four.

[134] 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 it um typically this this attempt kind of founders because you just don't know you end up not being able to explain why we only see four and it is nice in the space of physics that uh like if you look at from ozla's theorem that's much easier to prove that there's no solution for n equals 3 than it is for the general case.

[135] 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 4 in this case.

[136] Yeah, physicists are very interested in saying something about specific examples.

[137] And I find that interesting.

[138] Even when I'm trying to do things in mathematics, and I'm trying, even teaching courses into mathematics students.

[139] 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.

[140] And I'm less interested in kind of proving a precise theorem about exactly when it's going to work and when it's not going to work.

[141] Do you usually think about really simple examples, like both for teaching and when you try to solve a difficult problem?

[142] Do you construct the simplest possible examples that captures the fundamentals of the problem and try to solve it?

[143] Yeah, yeah, exactly.

[144] That's often a really fruitful way to, if you've got some idea, just kind of try to boil it down to what's the simplest situation in which this kind of thing is going to happen and then try to really understand that and understand that.

[145] And that is almost always a really good way to get insight into.

[146] Do you work with paper and pen?

[147] 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.

[148] I just visualize different parts of it.

[149] Visualize however I can.

[150] So most of the work is like when neural networks, for example, is you try to play with the simplest possible example and just to build up intuition by any kind of object has a bunch of variables in it and you start to mess around with them in different ways and visualize in different ways to start to build intuition or do you go to 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?

[151] 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 can kind of you can kind of see what's going on by looking at something happening in three dimensions.

[152] 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 where you could manipulate them and some kind of geometrical way, it's going to be a much higher dimensional space.

[153] So even simple examples, embedding them into three -dimensional space, you're losing a lot.

[154] Yeah, but to capture what you're trying to understand about them, you have to go to four or more dimension, so it starts to get to be hard.

[155] I mean, you can train yourself to try it as much as to kind of think about things in your mind.

[156] And, you know, I often use pad and paper, and often if in my office I 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 understand.

[157] 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?

[158] I mean, what do we make of that?

[159] I mean, to me that makes you quite sad.

[160] It makes it seem like there's a giant mystery out there that will never truly get to experience directly.

[161] It is kind of sad, you know, how difficult this is.

[162] 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.

[163] But the problem is one more of time.

[164] It's like, yes, you know, I could explain to you how this works.

[165] but you'd have to be willing to sit down with me and, you know, work at this repeatedly leave for, you know, for hours and days and weeks.

[166] And, I mean, it's just going to take that long for your mind to really wrap itself around what's going on.

[167] And that does make things inaccessible, which is sad.

[168] But, again, 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 going to spend our time doing.

[169] Speaking of a limited amount of time, we only have a few hours, maybe a few days together here on this podcast.

[170] Let me ask you the question of amongst many of the ideas that you work on in mathematics and physics, what is the most beautiful idea?

[171] Or one of the most beautiful ideas, maybe a surprising idea.

[172] And once again, unfortunately, the way life works, we'll only have a limited time together to try to convey such an idea.

[173] Okay.

[174] 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 to quantum mechanics.

[175] 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.

[176] Well, can I actually, on a small tangent, you did write a paper towards a grant unified theory of mathematics and physics.

[177] 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 in unification in physics over the last 50 years or so and what's been happening in mathematics and the kind of thing that Frankl'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 going to be in the same direction of getting deeper into mathematics and looking for more inspiration in mathematics from these successful ideas about fundamental physics.

[178] Could you put words to sort of the disciplines we're trying to unify?

[179] So you said number theory, are we literally talking about all the major fields of mathematics.

[180] So it's like the number theory, geometry, so the differential geometry, topology.

[181] Yeah.

[182] So the, I mean, one name for this, that this is acquired in mathematics is the so -called Langland's program.

[183] And so this started out in mathematics.

[184] It's that, you know, 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.

[185] And so that this actually was, anyway, that this could be 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.

[186] And then more later on in the 80s and 90s, there were something called geometric Langlands that people realize that you could take what people have been doing in number theory in Langlands.

[187] and get written, just forget about the number theory and ask, what is this telling you about geometry?

[188] And you get a whole, some new insights into certain kinds of geometry that way.

[189] So it's, anyway, that's kind of the name for this area, is Langlands and Geometric Langlands.

[190] And just recently in the last few months, there's been, um, there's kind of really major paper that appeared by Peter Schulza and Laurent Farg, where they, you know, made, you know, some, some, a serious advance and trying 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.

[191] One of the things that makes me sad is, you know I'm a pretty knowledgeable person and then what is it at least I'm in the neighborhood of 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 is I think even most mathematicians have no really don't actually understand what this is about them in the the group of people who really understand all these ideas and so for instance this paper of Schultz and Farag that I was talking about the number of people who really actually understand how that works is anyway one very very small and so it's so I think even you find if you talk to mathematicians and physicists even they will often feel that you know 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 it's 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 this space of mathematics or physics there's an idea that you know 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 and kind of learned it when I actually started teaching math classes, which is maybe that there's a simple way to explain kind of a fundamental way in which algebra and geometry are connected.

[192] 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.

[193] But it's completely abstract.

[194] It is nothing geometric about it.

[195] 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.

[196] 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.

[197] So you can multiply them and add them.

[198] It's an algebra.

[199] But it seems to have nothing to do with geometry.

[200] But if you ask yourself this question and ask, you know, is our integers, can you think, if somebody gives you an integer, can you think of it as a function on some space, on some geometry?

[201] And it turns out that, yes, you can, and the space is the space of prime numbers.

[202] 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, you know, at each prime number, taking that integer, modula, that prime.

[203] So if you say, I don't know, if you give it 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 one.

[204] What is, what is its value at three?

[205] Well, it's nine plus one, so it's one, mod three.

[206] So it's, it's zero at two, it's one at three, and you can kind of keep going.

[207] And so this is really kind of a truly fundamental idea.

[208] It's at the basis of what's called algebraic geometry, and it just links these two parts of mathematics that look completely different.

[209] And it's just an incredibly powerful idea and so much of mathematics emerges from this kind of simple relation.

[210] So you're talking about mapping from one discrete space to another.

[211] For a second, I thought perhaps mapping like a continuous space to a discrete space, like functions over a continuous space.

[212] Well, yeah.

[213] Well, 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.

[214] 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 say, wait a minute, maybe I should be trying to solve this using algebra.

[215] 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.

[216] Okay.

[217] So for each point in the space, I associate a number.

[218] I can take different kinds of functions and different kinds of values, but basically functions on a space.

[219] 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.

[220] 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?

[221] What would that space be?

[222] and what kind of functions would they be?

[223] And that going back and forth really brings these two completely different -looking areas of mathematics together.

[224] Do you have particular examples where it allowed to prove some difficult things by jumping from one to the other?

[225] Is that something that's a part of modern mathematics where such jumps are made?

[226] Oh, yes, this is kind of all the time.

[227] Much of modern number theory is kind of based on this idea.

[228] And when you start doing this, you start to realize that you need, you know, what simple things, simple things on one side, the algebra start to require you to think about the other side, about geometry in a new way.

[229] You have to kind of get a more sophisticated idea about geometry.

[230] Or if you start thinking about the functions on a space, you may need a more sophisticated kind of algebra.

[231] But in some sense, I mean, much or most of modern number theory is based upon this move to to geometry and there's also a lot of geometry and topology is also based upon change if you want to understand the topology of something, you look at the functions, you do dromchomology and you get the topology.

[232] Anyway.

[233] Well, let me ask you then the ridiculous question.

[234] You said that this idea is beautiful.

[235] Can you formalize the definition of the word beautiful and why is this beautiful?

[236] First, why is this beautiful and second, what is beautiful?

[237] Well, and I think there are many different things you can find beautiful for different reasons.

[238] 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.

[239] So in some sense, you can almost kind of try and measure it in the sense of what's the, What are the implications of this idea?

[240] What non -trivial things does it tell you versus, you know, how simply can you express the idea?

[241] So the level of compression, what is it, correlates with beauty?

[242] Yeah, that's one aspect of it.

[243] And so you can start to tell that an idea is becoming uglier and uglier as you start kind of having to, you know, 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.

[244] 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.

[245] Okay, so let's put some philosophical words on the table and trying to make some sense of them.

[246] One word is beauty, another one is simplicity, as you mentioned.

[247] Another one is truth.

[248] So do you have a sense?

[249] if I give you two theories, one is simpler, one is more complicated.

[250] Do you have a sense which one is more likely to be true to capture deeply the fabric of reality?

[251] The simple one or the more complicated one?

[252] Yeah, I think all of our evidence and what we see in the history of the subject is the simpler one, though.

[253] often it's a surprise it's simpler in a surprising way but um yeah that that we just don't we just anyway the kind of best theories have been coming coming up with are ultimately when not properly understood relatively simple and much much simpler than they 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 are we just like ultra -biased then we we we just kind of convince ourselves that simple is better good we find simplicity beautiful, or is there something about our actual universe that at the core is simple?

[254] My own belief is that there is something about a universe that's simple, and as I was trying to say that, you know, there is some kind of fundamental thing about math, physics, and physics and all this picture, which is, which is in some sense simple.

[255] It's true that, you know, it's of course true that, you know, our minds have certain, are very limited and can certainly do certain things and not others.

[256] So it's in principle possible that there's some great insight.

[257] 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.

[258] We don't.

[259] And that what we're seeing this kind of simplicity is just because that's all we ever have any hope of seeing.

[260] So there's a brilliant physicist by the name of Sabine Hassanfelder, who both agrees and disagrees with you, I suppose, agrees that the final answer will be simple.

[261] Yeah.

[262] But simplicity and beauty leads us astray in the local pockets of scientific progress.

[263] Do you agree with her disagreement?

[264] Do you disagree with her agreement?

[265] And I agree with the agreement and so on.

[266] Anyway, yes, I found it was really fascinating reading your book.

[267] and anyway, I was finding disagreeing with a lot, but then at the end when she says, yes, when we find there, when we actually figure this out, it will, it will be simple.

[268] And, okay, so we agree in the end.

[269] But does beauty lead us astray, which is the, the core thesis of her work in that book?

[270] I actually, I guess I do disagree with her on, on that so much, I don't think, and especially, and I actually fairly strongly disagree with her about sometimes, sometimes the way she'll refer to math.

[271] So the problem is, you know, physicists and people in general just refer to 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.

[272] 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 easy to fool yourself.

[273] And, you know, it's very easy to decide, you know, to fall in love with an idea, you have an idea, you think, oh, this is great and you fall in love with it.

[274] And it's like any kind of love affair, it's very easy to believe that, you know, the object of your affections is much more beautiful than the others might think and that they really are.

[275] And that's very, very easy to do.

[276] So if you say, I'm just going to pursue ideas about beauty and this, and mathematics and this, it's extremely easy to.

[277] to just fool yourself, I think.

[278] And I think that's a lot of what the story as she was thinking of about where people have gone astray of that, I think it's, I would argue that it's more people.

[279] 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 and more beautiful than it really was, is a lot of the story.

[280] I see, so it's not that the simplicity to be leases as a strays that it's just people or people and they fall in love with whatever idea they have and then they weave narratives around that idea or they present that such a way that emphasizes the simplicity and the beauty.

[281] Yeah, that's part of it.

[282] But the thing about physics that you have is that you, you know, what really can tell, 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.

[283] And it's certainly true that if you, you know, if you thought you had a simple idea and that doesn't work and you got into an experiment and what actually does work is some more, maybe some more complicated version of it, that can certainly happen.

[284] And that can be true.

[285] 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, you know, is this idea beautiful?

[286] But, you know, is there something about theory which is not quite consistent and use that as a guide, that there's something wrong there, which needs fixing?

[287] And so I think that part of her argument, I think we're on the same page about what's what is consistency and inconsistencies what what exactly um do you have examples in mind well it can be just simple inconsistency between theory and an experiment that if you so we have this great fundamental theory but there are some things we see out there which don't seem to fit in it like like dark energy and dark matter for instance but if there's something which you can't test experimentally i think you know she would argue and i would agree that for And since if you're trying to think about gravity and how are you going to have a quantum theory of gravity, you should kind of be, you know, test any of your ideas with kind of a thought experiment, you know, is, does this actually give a consistent picture of what's going to happen of what happens in this particular situation or not?

[288] So this is a good example.

[289] You've written about this, you know, since quantum gravitational effects are really small, super small, arguably unobes.

[290] observably small.

[291] Should we have hope to arrive at a theory of quantum gravity somehow?

[292] What are the different ways we can get there?

[293] You've mentioned that you're not as interested in that effort because basically, yes, you cannot have ways to scientifically validated given the tools of today.

[294] Yeah.

[295] I've actually, you know, over the years, certainly it's spent a lot of time learning about gravity and about attempts to quantize it, but it hasn't been that much.

[296] in the past the focus of what I've been thinking about.

[297] But, I mean, my feeling was always, you know, as I think Spina would agree, that the, you know, one way you can pursue this, if you can't do experiments, is just this kind of search for consistency.

[298] You know, it can be remarkably hard to come up with a completely consistent model of this in a way that brings together quantum mechanics and general relativity.

[299] 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.

[300] And string theorists will tell you this.

[301] Other people will tell you it.

[302] It's kind of what people argue about.

[303] 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.

[304] everybody's program for how to find a theory of quantum gravity, you know, ends up with something that is consistent.

[305] And so, in some sense, you could argue this is what happened to the strength there is.

[306] They solved their problem of finding a consistent theory of quantum gravity, but they found 10 to the 500 solutions.

[307] 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's, it has, of 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.

[308] And so this is just a depressing situation.

[309] But I do think 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.

[310] 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 make sense and hopefully i mean we'll sneak up onto this question a bunch of times because you kind of said uh 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 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.

[311] So, okay, let's talk a little bit about string theory.

[312] You've been a bit of an outspoken critic of strength theory.

[313] Maybe one question first to ask is, what is string theory?

[314] And beyond that, why is it wrong?

[315] Or rather, as the title of your blog says, not even wrong.

[316] Okay.

[317] Well, one interesting thing about the current state of string theory, theory.

[318] I think I'd argue it's actually very, very difficult to, at this point, to say what string theory means.

[319] If people say they're a string theorist, what they mean and what they're doing is, it's kind of hard to pin down the meaning of the term.

[320] 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, 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 a quantum theory of kind of one -dimensional loops moving around in space time, so -called strings.

[321] And so instead of one degree of freedom, these have an infinite number of degrees of freedom.

[322] It's a much more complicated theory.

[323] But you can imagine, okay, we're going to quantize this theory of loops moving around in space time.

[324] And what they found is that they, is that you could make, 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 ten dimensional.

[325] And so then you had this problem, again, the problem I refer to at the beginning of, okay, now once you make that move, you've got to get rid of six dimensions.

[326] 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 Kalabiao manifold and that we knew very, very few examples of this.

[327] So what got a lot of people very excited back in 84, 85 was the hope that you could just take this ten -dimensional string theory and find.

[328] 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 um you know that this this ultimately was a failure that you ended up that this idea just didn't um there ended up being just too many ways of doing this and you didn't know how to do this consistently um that it was kind of not even wrong in the sense that you couldn't even 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 um it was kind of in the in the realm of ideas which initially look good but the more you look at them they just um they don't work out the way the way you want and they don't actually end up carrying the power or the that you originally had this vision of and yes the 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 uh like they branched out you mentioned ten dimensions you mentioned loops with infinite degrees of freedom, what are there interesting ideas to you that kind of emerged from this world?

[329] Well, yeah, I mean, the problem in talking about the whole subject, and part of the only reason I wrote the book is that, you know, it gets very, very complicated.

[330] 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.

[331] And so people, I think, ended up wandering around in a very, very rich space of ideas about mathematics and physics and discovering all sorts of really interesting things.

[332] 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.

[333] So there's a lot of beautiful mathematics came out of it.

[334] I think one of the most spectacular is what the physicist called two -dimensional conformal field theory.

[335] And so these are basically quantum field theories and kind of think of it as one space and one time dimension, which have just this huge amount of symmetry and a huge amount of structure, which is some totally fantastic mathematics behind it.

[336] And again, and some of that mathematics is exactly also what appears in the Langlands program.

[337] So a lot of the first interaction between math and physics around the Langley's program has been around these two -dimensional conformal field theories.

[338] Is there something you could say about what are the major problems are with string theory?

[339] So besides that there's no experimental validation, you've written that a big hole in string theory has been its perturbative definition.

[340] yeah perhaps that's one can you explain what that means well maybe to begin with i mean i think i mean the simplest thing to say is you know the the initial idea really was that okay we're we have this instead of what's great is we have this thing it only works that's very structured and has to work in a certain way for it to make sense and um but but then you ended up 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.

[341] Six of dimensions.

[342] 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.

[343] There's an infinite number of ways of doing it, and you can get whatever you want, depending on how you do it.

[344] So you end up, 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.

[345] 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 a quantum theory and working with it, which 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.

[346] So actual perturter with string theory by itself really only works in ten dimensions.

[347] So you have to start making some kinds of assumptions about how I'm going to go beyond this formulation that we really understand of string theory and get rid of these six dimensions.

[348] So kind of the simplest one was the Klaviao postulate.

[349] but um when that didn't really work out people have tried more and more different things and and the hope has always been that the solution that this problem would be that you would find a a deeper and better understanding of what string theory is that would actually go beyond this perturbative expansion and which would um which would generalize this and that once you had that it would um it would solve this problem of it would pick out what to do with the six dimensions.

[350] How difficult is this problem?

[351] So if I could restate the problem, it seems like there's a very consistent physical world operating in four dimensions.

[352] And how do you map a consistent physical world in 10 dimensions to a consistent physical world in four dimensions?

[353] Right.

[354] And how difficult is this problem?

[355] Is that something you can even answer?

[356] Just, in terms of physics, intuition, in terms of mathematics, mapping from 10 dimensions to 4 dimensions.

[357] Well, basically, I mean, you have to get rid of six of the dimensions.

[358] So there's kind of two ways of doing it.

[359] One is what we call it compactification.

[360] You say that there really are 10 dimensions, but for whatever reason, six of them are really so, so small, we can't see them.

[361] So you basically start out with 10 dimensions and what we call it, you know, 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.

[362] That's a math trick.

[363] So can you also help me build an intuition about how rich and interesting the world in those six dimensions is?

[364] So compactification seems to imply that it's not very interesting.

[365] Well, no, but the problem is that what you learn if you start doing mathematics and 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?

[366] It's just a, it's kind of an unanswerable question.

[367] It's just, I mean, it's even kind of technically undecidable in some way.

[368] There's just, you're too, there are too many things you can do with all these, if you start trying to make, 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.

[369] And so it, unless you have some very, very strong principle, which is going to 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.

[370] So if you have ten dimensions, the kind of things that happen know, say that's actually the way, that's actually the fabric of our reality's 10 dimensions.

[371] There's a limited set of behaviors of objects.

[372] I don't know, even know what the right terminology to use that can occur within those dimensions, like in reality.

[373] And so, like, what I'm getting at is, like, is there some consistent constraints?

[374] So if you have some constraints that map to reality, then you can start saying, like, Dimension number seven is kind of boring.

[375] All the excitement happens in the spatial dimensions, one, two, three.

[376] And time is also kind of boring.

[377] And like some are more exciting than others.

[378] Or we can use our metric of beauty.

[379] Some dimensions are more beautiful than others.

[380] 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.

[381] In some sense, just the basic fact that you need to get rid of them.

[382] see them.

[383] So you need to somehow explain them.

[384] The main thing you're trying to do is to explain why we're not seeing them.

[385] And so you have to come up with some theory of these extra dimensions and how they're going to behave.

[386] And string theory gives you some ideas about how to do that.

[387] 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.

[388] So it's a, it's not a really, it's an inherently kind of dubious and worrisome thing that you're trying to do there.

[389] Why are you just adding in all the stuff and then trying to explain why we don't see it?

[390] 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?

[391] Or do you leave a little door open to saying the current tools of physics, and obviously our brains are unable to observe them.

[392] But we may need to come up with methodologies for observing that.

[393] So as opposed to collapsing your mathematical theory into four dimensions, 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.

[394] Yes, I mean, you can certainly ask, you know, assume that we've got model, look at models with more dimensions and ask, you know, what would the observable effects, how would we know this?

[395] And you go out and do experiments.

[396] So, for instance, you have a, like, gravitationally, you have an inverse square law of forces.

[397] Okay, if you had more dimensions, that inverse square law would change in something else.

[398] So you can go and start measuring the inverse square law and say, okay, inverse square law is working, but maybe if I get, get, and it turns out to be actually kind of very, very hard to measure gravitational effects, and even kind of, you know, somewhat macroscopic, distances because they're so small.

[399] So you can start looking at the inverse square law and 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.

[400] And so people look for that.

[401] And again, you don't see it.

[402] But you can, I mean, there's all sorts of experiments of this kind.

[403] You can imagine which test for effects of extra dimensions at different distance scales.

[404] but none of them, I mean, they all just don't work.

[405] Nothing yet.

[406] But you can say, ah, but it's just much, much smaller.

[407] You can say that.

[408] Which, by the way, makes LIGO.

[409] And the detection of gravitational waves is quite an incredible project.

[410] Ed Witten is often brought up as one of the most brilliant mathematicians and physicists ever.

[411] What do you make of him and his work on string theory?

[412] Well, I think he's a truly remarkable figure.

[413] I've had the pleasure of meeting him first when he was a postdoc.

[414] And, I mean, he's just completely amazing mathematician and physicist.

[415] And, you know, he's quite a bit smarter than just about any of the rest of us and also more hardworking.

[416] And it's a kind of frightening combination to see how much he's been able to do.

[417] and um but i would actually argue that you know his his greatest work the things that he's done that have been of just this mind -blowing significance of giving us and 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 um you know he so he was actually one the very strange thing about him in some sense is that he um 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 you were as it would have been very hard to come up with a new idea that was going they'd work physically and get you a Nobel Prize.

[418] But he got a field's medal for a certain work he did in mathematics, and that's just completely unheard of, you know, for mathematicians to give a field's medal to someone outside their field, and physics is really, you know, you wouldn't have before he came around.

[419] I don't think anybody would have thought that was even conceivable.

[420] 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.

[421] A specific problem of trying to do better than the standard model is just this insanely successful thing and it kind of came together in 1973 pretty much.

[422] And all of the people who kind of were involved in that coming together, many of them ended up with Nobel Prizes for that.

[423] 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 -ide theory, it really hasn't, it's been too hard a problem, it hasn't worked, the theory's too good.

[424] So it's not that other people went out there and did it and not him, and that they got no more prizes for doing it.

[425] It's like no one really, the kind of thing he's been trying to do with string theory is not, that no one has been able to do since 1973.

[426] 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, so on, why?

[427] What's wrong, what's broken about the standard model?

[428] Why does it need to be improved?

[429] I mean, the thing that's gets most attention is gravity that we have trouble.

[430] 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.

[431] So that's the big problem everybody talks about.

[432] 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, let's just say that they're not beautiful.

[433] They're not, you have to make the thing work, you have to throw in lots and lots of extra parameters at various points.

[434] And a lot of this has to do with the so -called, you know, the so -called Higgs mechanism in the Higgs field.

[435] 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.

[436] There's a very small number of parameters and a few integers which tell you what the theory is.

[437] To make this work as a theory of the real world, you need a Higgs field, and it needs to do something.

[438] And once you introduce that Higgs field, all sorts of parameters make an appearance.

[439] So now we've got 20 or 30 or whatever parameters that are going to tell you what all the masses of things are and what's going to happen.

[440] So you've gone from a very tightly constrained thing with a couple parameters.

[441] to this thing which the minute you put it in, you had to add all these extra parameters to make things work.

[442] 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.

[443] Maybe we live in a multiverse and those numbers are just different in every universe.

[444] 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.

[445] 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.

[446] And that that's what we should look for.

[447] 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 I mean the most positive argument for it is all the you know all sorts of new ideas about mathematics and about parts of physics really emerged from it so it was a very a fruitful source of ideas and I think you know this is actually one argument you'll definitely which I kind of agree with, they'll hear from Witten and from other string theorists.

[448] I said that, you know, this is just such a fruitful and inspiring idea, and it's led to so many other different things coming out of it that, you know, there must be something right about this.

[449] And that's, yeah, okay, that, anyway, I think that that's probably the strong, the strongest thing that they've got.

[450] 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.

[451] Like, it could, it may not be exactly, um, uh, exactly the theory, but, uh, sticking on it longer might get us closer to the theory of everything.

[452] Well, the problem that now really is that you really don't know what it is now.

[453] You've never, nobody has ever kind of come up with this non -perturbitive theory.

[454] So there, it's, it's become more and more frustrating and an odd activity to try to argue with the string theorists about string theory, because it's become less and less well -defined what it is.

[455] 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.

[456] So what has actually happened kind of sociologically is that you started out with this fairly well -defined proposal.

[457] And then I would argue because that didn't work.

[458] branched out in all sorts of directions doing all sorts of things that 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 theorist and um and but but it's becoming almost more kind of a tribal denominator than a um well it's very hard to know what you're arguing about when your argument at string theory these days.

[459] Well, to push back on that a little bit, I mean, string theory, it's just a term, right?

[460] It doesn't, like, you could, like, this is the way language evolves.

[461] Is it could start to represent something more than just the theory that involves strings.

[462] It could represent the effort to unify the laws of physics, right?

[463] Yeah.

[464] At high dimensions, with these super tiny objects, right?

[465] Or something like that.

[466] 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.

[467] 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.

[468] And then once again, neural networks became all the rage about 10, 15 years ago.

[469] And as it goes up and down, and a lot of people would argue that using terminology like machine learning and deep learning is, is you know often misused over general you know everything that works is deep learning everything that doesn't isn't something like that you know that's just the way uh human again we're back to sociological things but i guess what i'm trying to get at is if if we leave the sociological mess aside uh do we throw out the the baby with the bath water is there's some besides the side effects of nice ideas from the 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 strength theory, that people call strength theory?

[470] You're right, it is kind of a common problem that, you know, how what you're, 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.

[471] We're talking about a specific idea, 10 -dimensional super strings, compactified to six dimensions.

[472] To my mind, the really bad thing has 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.

[473] 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 has comes from.

[474] And so the problem with this is that having as your initial name and what everything points back to something which really, which really, didn't work out, it kind of makes everybody, makes everything, you've created this potentially very, very interesting field with interesting things happening, but, you know, people in graduate school take courses on string theory and everything kind of, and this is what you tell the public in which you continually pointing back, so you're continually pointing back to this idea, which never worked out as your guiding inspiration.

[475] And it really kind of deforms the whole, your whole way of your hopes of making progress.

[476] And that's, to me, I think, you know, the kind of worst thing has happened in this field.

[477] Okay, sure.

[478] So there's a lack of transparency, sort of authenticity about communicating the things that failed in the past.

[479] And so you don't have a clear picture of, like, firm ground that you're standing on.

[480] But again, those are sociological things.

[481] And I, I, there's a bunch of questions I want to ask you.

[482] So one, what's you, intuition about why the original idea failed.

[483] So what can you say about why you're pretty sure it has failed?

[484] And the initial idea was, as I try to explain it, it was quite seductive and that you could see why Witten and others got excited by it.

[485] It was, you know, at the time it looked like there were only a few possible clobias that would work.

[486] And it looked like, okay, we just have to understand this very specific model and these very specific six -dimensional spaces and we're going to get everything.

[487] And so it was a very subjective idea.

[488] But it just, you know, as people worked 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 these six dimensions and you can't, and this is just not going to work.

[489] Meaning like it's, I mean, what was the failure mode here is you could just have an infant number of possibilities that you could do so it's you can come up with any theory you want you can fit quantum mechanics you can 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 kind of being essentially empty that it just didn't doesn't end up not telling you anything because it's consistent with just about just about anything.

[490] And so, I mean, there's a complex, if you try and talk with string theories about this now, I mean, there's a, there's an argument, there's a long argument over this about whether, you know, oh, no, no, no, maybe there's still our constraints coming out of this idea or not.

[491] Or maybe we live in a multiverse and, you know, everything is true anyway.

[492] So you can, there are various ways you can kind of, that string theories have kind of react to this kind of argument that I'm making.

[493] But I try to hold on to it.

[494] What about experiment to validation?

[495] Is that a fair standard to hold before a theory of everything that's trying to unify quantum mechanics and gravity?

[496] Yeah, I mean, ultimately, to be really convinced that on some new idea of that unification really works, you need some kind of, you need to look at the real world and see that this is telling you something true about it.

[497] 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.

[498] I mean, it can be various kinds of experimental validation, but that's certainly ideally what you're looking for.

[499] How tough is this, do you think, for a theory of everything, not just string theory?

[500] for something that unifies gravity and quantum mechanics.

[501] So they're very big and the very small.

[502] Let me ask it one way.

[503] Is it a physics problem, a math problem, or an engineering problem?

[504] My guess is it's a combination of a physics and a math problem that you really need.

[505] It's not really enjoying.

[506] 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.

[507] That's not the kind of problem.

[508] It is at all.

[509] But the question is, you know, what mathematical tools you need to properly formulate the problem is unclear.

[510] 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 there are some combination of them, which would, which we need to kind of properly formulate the problem and see that it has a solution that looks like the real world.

[511] 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.

[512] 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.

[513] phenomena?

[514] Or can you do that as long as the theory is consistent and doesn't have special cases for each of the phenomena?

[515] Well, your theory should, I mean, if your theory is going to 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.

[516] And just one aspect that people have concentrated 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 that's been a huge focus of quantum gravity work work has been just those paradoxes but so stepping outside of string theory uh can you just say first at a high level what is a theory of everything what is the theory of everything 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 going to explain to you you know anything, it doesn't really, this kind of theory of theory of everything we're talking about doesn't say anything interesting, particularly about like macroscopic objects about what the weather is going to be tomorrow or, you know, things are happening at this scale.

[517] But just what we've discovered is that as you look at the universe, it kind of, you know, if you kind of start, 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.

[518] And it's, um, it's good.

[519] So what we mean by the theory of everything is a theory that describes all, 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.

[520] How you get from that theory to describing some macroscopic, incredibly complicated thing is there that becomes, again, more, an engineering problem and you may need machine learning or you may, you know, a lot of very different things to do it.

[521] Well, I don't even think it's just engineering.

[522] It's also science.

[523] One thing that I find kind of interesting talking to physicists is a little bit, there's a little bit of hubris.

[524] Some of the most brilliant people I know are physicists, both philosophy and just in terms of mathematics, in terms of understanding.

[525] world but there's a kind of uh either a hubris or what would i call it uh 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 the old rutherford thing uh 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 yeah like at every level level from biology, like how life originates, that itself, like complex systems.

[526] Like that in itself is like this gigantic thing that requires a theory of everything.

[527] And then there's the, in the space of humans, psychology, like intelligence, collective intelligence, the way it emerges among species, that feels like a complex system that requires its own theory of everything.

[528] 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 the theory of everything it explains the basic laws of physics that gave us the universe even stuff that's super complex like how 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.

[529] Still, we won't be able to have a strong explanation of why food tastes delicious.

[530] Oh, yeah, yeah, no. No, anyway, yeah, I agree completely.

[531] I mean, there is something kind of completely wrong with this terminology of theory or everything.

[532] It's not, it's really, in some sense, very bad term, very eubristic and bad terminology, because it's not, um, this is explaining, this is a purely kind of reductionist point of view that you're trying to understand certain very specific kind of things which you know in principle other things you know emerge from but to actually understand how anything emerges from this is it's hope it can't be understood in terms of this this underlying fundamental theory is going to be hopeless in terms of kind of you what about this um this various emergent behavior and as you go to different levels of explanation you're going to need to develop new you know different completely different ideas completely different ways of thinking and i guess there's a famous kind of um phil anderson's slogan is that you know more is different and so and it's just it's just yeah even once you understand how what a couple of things well if you have a collection of stuff and you understand perfectly well how each thing is interacting with it we're with the others, what the whole thing is going to do is just a completely different problem.

[533] And it's just not, and you need completely different ways of thinking about it.

[534] What do you think about this?

[535] I got to ask you at a few different attempts at a theory of everything, especially recently.

[536] 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.

[537] But he's recently been talking about a theory of everything through his physics project, essentially.

[538] What do you think about this kind of discrete theory of everything, like from simple rules and simple objects on the hypergraphs emerges all of our reality, where time and space are emergent, basically everything we see around us is emerging.

[539] Yeah, I have to say, unfortunately, I've kind of pretty much zero sympathy for that.

[540] I mean, I don't, I spend a little time looking at it, and I just don't see, it doesn't seem to me to get anywhere.

[541] And it really is, just really, really doesn't agree at all with what I'm seeing, this kind of unification of mathematics that I'm kind of talking about around certain kinds of very deep ideas about geometry and stuff.

[542] This, if you want to 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 is kind of randomly is emerging from these more basic, very, very simple -minded things.

[543] And you have to give me some serious evidence for that, and I'm saying nothing.

[544] So, Mirage, you don't think there could be a consistency where things that quantum mechanics could emerge from much, much, much smaller, discrete, like computational -type systems.

[545] Well, I think from the point of view of certain mathematical point of view, quantum mechanics is already mathematically as simple as it gets.

[546] It really is a story about really the fundamental objects that you work with 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.

[547] They're exactly the same.

[548] And cellular automata are something completely different which don't fit into these structures.

[549] And so I just don't see why.

[550] Anyway, I don't see.

[551] it is a promising thing to do.

[552] And then just looking at it and saying, does this go anywhere?

[553] Does this solve any problem that I've ever that I didn't, does this solve any problem of any kind?

[554] I just don't see it.

[555] Yeah, to me, cellular automata and these hypergraphs, I'm not sure if solving a problem is even the standard to apply here at this moment.

[556] To me, the fascinating thing is that the question it asks have no good answers.

[557] So there's not good math explaining, forget the physics of it, math explaining the behavior of complex systems.

[558] And that to me is both exciting and paralyzing.

[559] Like we're at the very early days of understanding, you know, how complicated and fascinating things emerge from simple rules.

[560] Yeah.

[561] You know, I agree.

[562] I think that is a truly great problem.

[563] 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.

[564] It's 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.

[565] And I mean, again, we're back to this original problem that, you know, your time in life is limited.

[566] You have to figure out what you're going to spend your time thinking, about, and that's something I've just never seen enough to convince me to spend more time thinking about.

[567] Well, also timing.

[568] 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.

[569] And so it's like you have to pick the problems that are solvable today.

[570] 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.

[571] It feels like, well, like, it feels like something post -human that will solve that problem.

[572] Or like significantly enhanced humans, meaning like using computational tools, very powerful computational tools to us, to crack these problems open.

[573] That's if our, approach to science, our ability to understand science, our ability to understand physics, will become more and more computational.

[574] Or there'll be a whole field that's computational nature, which currently is not the case.

[575] Currently, computation is the thing that sort of assists us in understanding science the way we've been doing it all along.

[576] But if there's a whole new, I mean, that we're from new kind of science, right?

[577] It's a little bit dramatic.

[578] But, you know, if computers do science on their own computational systems, perhaps that's the way they would do the science.

[579] They would try to understand the cellular automata, and that feels like we're decades away.

[580] So perhaps they'll crack open some interesting facets of this physics problem, but it's very far away.

[581] So timing is everything.

[582] That's perfectly possible, yeah.

[583] Well, let me ask you then in the space of geometry.

[584] I don't know how well you know Eric Weinstein.

[585] quite well yeah what are your thoughts about his geometric community and the space of ideas that he's playing with on uh in his proposal for a theory of everything well i 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 various they're they're really versions of the same problem that you try to um you try to get unity by putting everything into some bigger structure So he has some other ones that are not so conventional that he's trying to work with.

[586] But he has the same problem that even 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, the many dimensions, many kinds.

[587] And I just don't see any way he's going to have the same problem the string there is have.

[588] How do you get back down to the structures of the standard model?

[589] And how do you, yeah, so I just, anyway, it's the same, and there's another interesting example of a similar kind of thing is Garrett Lise's theory of everything.

[590] Again, you know, there it's a little bit more specific than Eric's.

[591] He's working with this E8, but it, And 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 going to get back to the actual, to the objects we've seen, how are you going to, you create these big symmetries, how are you going to break them?

[592] And, because we don't see those symmetries in the real world.

[593] And so ultimately there would need to be a simple process.

[594] for collapsing it to four dimensions.

[595] You'd have to explain it.

[596] Well, yeah, I forget in his case, but it's not just four dimensions, it's also these structures you see in the standard model.

[597] There's a, you know, there's certain very small dimensional groups of symmetry, so called U1, SU2, and SU3, and the problem with, and this has been the problem since the beginning, almost immediately after 1973, about a year later, two years later, people started talking about grand unified theories.

[598] So you take the U -1, the S -U -2, and the S -U -3, and you put them together into this bigger structure called the S -U -5 or S -O -10.

[599] 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 S -U -5 symmetries in the world?

[600] I only see these.

[601] And so, and I think, you know, the kind of thing that Eric and all of a sudden, Garrett and lots of people who try to do it, They all kind of found her in that same way that they don't have a good answer to that.

[602] Are there lessons, ideas to be learned from theories like that, from Gary Lise's, from Erick's?

[603] I don't know, it depends.

[604] I have to confess, I haven't looked that closely at Erick's.

[605] I mean, he explained to this to me personally a few times, and I've looked a bit at his paper.

[606] But it's, again, we're back to the problem of a limited amount of time in life.

[607] Yeah, I mean, it's an interesting effect, right?

[608] Why don't more physicists look at it?

[609] I mean, I'm in this position that somehow, you know, people write me emails for whatever reason.

[610] And I worked 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.

[611] And so a lot of people write to me with different theories about what they have or how to create general intelligence.

[612] 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.

[613] 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, because I'm dismissing them because they're outside of the sort of the usual process of academic research.

[614] Yeah, well, I mean, the same thing.

[615] Pretty much every day in my email, there's somebody's got a theory or everything about why all of what physicists are doing.

[616] Perhaps the most disturbing thing I should say about my, being a critic of string theory is that when you realize who your fans are, that every day I hear from somebody 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.

[617] Oh, no, oh, no. And, you know, most of these are, you know, you quickly can see this person doesn't know very much and doesn't know what they're doing.

[618] You know, but there's a whole continuum to, you know, people who are quite serious physicists and mathematicians who are making a fairly serious attempt to try to do something like Garrett and Eric.

[619] And then your problem is, you know, you spent you.

[620] you do try to spend more time looking at it and try to figure out what they're really doing.

[621] But at some point you just realize, wait a minute, for me to really, really understand exactly what's going on here would just take time I just don't have.

[622] Yeah, it takes a long time.

[623] 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 the system that's intelligent.

[624] So you don't need to get approval from somebody that's saying you have a good idea here.

[625] You can just utilize that idea and engineer a system.

[626] Like naturally leads to engineering.

[627] With physics here, if you have a perfect theory that explains everything, that still doesn't obviously lead, one, to scientific experiments that can validate that theory, and two, to, like, trinkets you can build and sell.

[628] at a store for $5.

[629] I can't make money off of it.

[630] So that makes it much more challenging.

[631] Well, let me also ask you about something that you found, especially recently appealing, which is Roger Penrose's Twister Theory.

[632] What is it?

[633] What kind of questions might it allow us to answer?

[634] What will the answers look like?

[635] It's only in the last couple years I really, really kind of come to really, I think, to appreciate it and to see how to really, what I believe to say I don't really do something with it, and I've gotten very excited about that the last year or two.

[636] I mean, one way of saying, one idea of twister theory is that what 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.

[637] So four dimensions behaves very, very specially, unlike other dimensions.

[638] And in four dimensions, there is a way of thinking about space, and time geometry where, you know, as well as just thinking about points in space and time, you can also think about different objects, these all called twisters.

[639] And then when you do that, you end up with a kind of a really interesting insight that the, 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.

[640] And you can reformulate in this twister language.

[641] And in this twister language, it's be, the fundamental objects are actually are more kind of the, are actually spheres in some sense, kind of the light cone.

[642] So maybe one way to say it, which actually I think is really, is quite amazing, is if you ask yourself, you know, what do we know about the world?

[643] We have this idea that the world out there is all these different points and these points of time.

[644] Well, that's kind of a derived quantity.

[645] What really know about the world is when we open, our eyes, what do you see?

[646] You see a sphere.

[647] And that what you're looking at is you're looking at, you know, a sphere is worth of light rays coming into your eyes.

[648] 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.

[649] 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 are living on light rays, not on points.

[650] And it's a very different way of thinking about physics.

[651] And, you know, he and others working with him developed a, you know, a beautiful mathematical, this beautiful mathematical formalism and a way to go back from forth between our kind of some aspects of our standard way we write these things down.

[652] and work in the so -called twister space.

[653] And, you know, they, certain things worked out very well, but they ended up, you know, I think kind of stuck by the 80s or 90s, that they weren't, it's a little bit like string theory.

[654] 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.

[655] 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.

[656] And I can go on about that endlessly or talk a little bit about it.

[657] But that's the, I think that that's the one kind of easy to explain insight about twister theory.

[658] There are some more technical ones.

[659] I think it's also very convincing what it tells you about spinners, for instance.

[660] but that's a more technical.

[661] Well, first, let's, like, linger on the spheres and the light cones.

[662] You're saying Twisted Theory allows you to make that the fundamental object with which you're operating.

[663] Yeah.

[664] How, I mean, first of all, like, philosophically, that's weird and beautiful.

[665] Maybe because it maps, it feels like it moves us so much closer to the way human brains perceive reality.

[666] 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 can you say a little bit more about what the heck that even means uh for because it's much easier to think about mathematically, like a point in space time?

[667] What does it mean to be operating on the light cone?

[668] It uses a kind of mathematics that's relative, that, you know, what was, kind of goes back to the 19th century among mathematicians.

[669] It's not, um, anyway, it's a bit of a long story, but one problem is that you have to start, it's crucial that you think in terms of complex numbers and not just real numbers.

[670] And this, for most people, that makes it harder to, for mathematicians, that's fine.

[671] We love doing that, but for most people, that makes it hard.

[672] order to think about, but I think perhaps the most, the way that there is something you can say very specifically about it, you know, in terms of spinners, which I don't know if you want to, I think at some point you want to talk.

[673] So maybe, what are spinners?

[674] Let's start with spinner.

[675] Because I think that if we can introduce that, then I can.

[676] By the way, Twister is spelled with an O and spinner is spelled with an O as well.

[677] Yes.

[678] Okay.

[679] So in case you want to Google it and look it up.

[680] That's very nice Wikipedia pages.

[681] As a starting point.

[682] I don't know what is a good starting point for Twister theory.

[683] Well, one thing you say about Penrose, I mean, Penrose is actually a very good writer and also a very good draftsman.

[684] He's on drafts.

[685] To the extent this is visualizable, he actually has done some very nice drawing.

[686] So, I mean, almost any kind of expository thing you can find him writing is a very good place to start.

[687] He's a remarkable person.

[688] But the, um, so spinners are something that independently came out of mathematics and out of physics.

[689] 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, there seemed to be some kind of doubling of the degrees of freedom going on.

[690] If you counted what was there in some sense in the way you would expect it.

[691] And when you started doing quantum mechanics and started looking at elementary particles, there were seen to be two degrees of freedom.

[692] They're not one.

[693] And one way of seeing it was that if you put your electron in a strong magnetic field and asked what was the energy of it.

[694] Instead of it having one energy, it would have two energies.

[695] It would be two energy levels.

[696] And as you increase magnetic field, the splitting would increase.

[697] So physicists kind of realized that, wait a minute.

[698] 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.

[699] Well, if we actually look at particles, that that's not right.

[700] they're pairs of complex numbers.

[701] There's pairs of complex numbers.

[702] So, you know, why, 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?

[703] Just weird.

[704] And then, but if you go, and then you can ask, you know, well, what happens if you, like, take an electron and rotate it?

[705] So how, how do things move in this pair of complex numbers?

[706] 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?

[707] So if you've taken any mathematics classes, you probably see vectors at some point.

[708] They're just triplets of numbers tell you what a direction is or how far you're going in three -dimensional space.

[709] And most of everything we teach in most standard courses in mathematics is about vectors and things you build out of vectors.

[710] 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.

[711] But what had been realized that Rion is that if you ask very, very generally, what are the, if you have, what are the things that you can kind of consistently think about rotating?

[712] And you can, so you ask a technical question, what are the representations of the rotation group?

[713] Well, you find that their one answer is they're vectors and everything you build out of vectors.

[714] But then people found, but wait a minute, there's also these other things which you can't build up.

[715] 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 spinners also.

[716] And to make a lot, and to make, and you can think of spinners in some sense as more fundamental than vectors, because you can build vectors out of spinners.

[717] You can take two spinners and make a vector, but you can't, you can't, if you only have vectors, you can't get spinners.

[718] So there in some sense, there's some kind of level of lower level of geometry beyond what we thought it was, which was kind of spinner geometry.

[719] 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, it's a bit hard, hard to do correctly.

[720] If you start, if you start with your whole setup is in terms of vectors, getting, describing things in terms of spinners is a whole different ball game.

[721] But the, but anyway, It was just this amazing fact that this kind of more fundamental piece of geometry of spinners and what we were actually seeing, if you look at electron, are one and the same.

[722] So it's a, I think it's kind of a mind -blowing thing, but it's very counterintuitive.

[723] What are some weird properties of spinners that are counterintuitive?

[724] There are some things that they do.

[725] For instance, if you rotate a spinner around 360 degrees, it doesn't come back.

[726] to where it's, it becomes minus what it was.

[727] 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.

[728] So they're kind of too valued in another weird way.

[729] 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 terms of vectors that will ever give you a spinner.

[730] It just is not going to ever work.

[731] As you were saying that, I was visualizing a vector walking along a Mobius strip and it ends up being upside down.

[732] But you're saying that doesn't really capture.

[733] So, I mean, what really captures it?

[734] The problem is that it's really the simplest way to describe it is in terms of two complex numbers.

[735] And your problem with two complex numbers is that's four real numbers.

[736] So your spinner kind of lies in a four -dimensional space, so that makes it hard to visualize.

[737] And it's crucial that it's not just any four -dimensional it's actually complex numbers.

[738] You're really going to use the fact that these are complex numbers.

[739] So it's very hard to visualize.

[740] But to get back to what I think is mind -blowing about twisters is that another way of saying 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 complex, is a two -complex -dimensional space so that every, and that it lives inside, the space that it lies inside is twister space.

[741] 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.

[742] And as you move around in space -time, you're just moving, your planes are just moving around.

[743] Okay.

[744] And that, but then the...

[745] So it's a plane and a four -dimensional, space.

[746] It's a plane.

[747] Complex.

[748] So it's two complex dimensions and four complex.

[749] But then, to me, the mind -blowing thing about this is this then kind of tautologically answers the question is what is a spinner?

[750] Well, a spinner is a point.

[751] I mean, the space of spinners at a point is the point.

[752] In Twister theory, the points are the complex two planes.

[753] And you want me to, and you're asking what a spinner is, well, a spinner and the space of spinners is that two -plane.

[754] So it's, you know, just your whole definition of what a point in space -time was just told you what a spinner was.

[755] It's just, it's the same thing.

[756] Yeah, well, we're trying to project that into a three -dimensional space and trying to intuit, but you can't.

[757] Yeah, so the intuition becomes very difficult.

[758] But from, if you don't, 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.

[759] They're just what you want to describe the electron is fundamentally the way you're describing the point in space time already.

[760] It's just there.

[761] Do you have a hope?

[762] You mentioned that you found it appealing recently.

[763] 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?

[764] Yeah, I mean, it certainly do have.

[765] 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, it has to do with this question of how do you treat time in your quantum theory.

[766] 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.

[767] but to make this the short version of it is that what people have found when you try and write down a quantum theory that it's often it's often a good idea to take your time coordinate whatever you're using to your time coordinate and then multiply it by the square of minus one and to make it purely imaginary and so you all these formulas which you have um in your standard theory if you do that to those I mean those those formulas have some very strange behavior and they're kind of singular.

[768] If you ask even some simple questions, you have to take very delicate singular limits in order to get the correct answer.

[769] And you have to take them from the right direction.

[770] Otherwise, it doesn't work.

[771] 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 behave mathematically.

[772] And what I hadn't really appreciated until fairly recently is also how dramatically that changes the whole structure of the theory.

[773] 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.

[774] And in particular, the way symmetries act on it is not at all what I originally had expected.

[775] And so that's the new thing that I've, where I think gives you something is to to do this move, which people often think of as just 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.

[776] And it turns out in twister theory, allows you to simultaneously talk about your usual time and the time times the square to minus one.

[777] They both fit very nicely into twister theory.

[778] And you end up with some structures which look a lot like the standard model.

[779] holds.

[780] Let me ask you about some Nobel Prizes.

[781] Okay.

[782] Do you think there will be, there was a bet between Michoacu and somebody else about, John Hogan.

[783] John Hogan, about, by the way, maybe discover a cool website, longbets .com or dot org.

[784] Yeah, yeah.

[785] It's cool.

[786] It's cool that you can make a bet with people and then check in 20 years later.

[787] I really love it.

[788] There's a lot of interesting bets on there.

[789] I would love to participate.

[790] But it's interesting to see, you know, time flies.

[791] Yeah.

[792] And you make a bet about what's going to happen in 20 years.

[793] You don't realize 20 years just goes like this.

[794] Yeah.

[795] And then you get to face and you get to wonder, like, what was that person, what was I thinking?

[796] That person, 20 years ago was almost like a different person.

[797] What was I thinking back then to think that is interesting?

[798] So let me ask you this on record.

[799] you know 20 years from now or some number of years from now do you think there will 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 uh string theory um string theory is definitely not that uh things have gone yeah so fine if you were giving financial advice you would say not to bet on it.

[800] No, do not, but I actually suspect if you ask strength here as that question, these days you're going to get a few of them saying.

[801] I mean, if you'd ask them that question 20 years ago, again, when Kaku was making this a bed, whatever, I think some of them would have taken you up on it.

[802] And certainly back in 1984, a bunch of them would have said, oh, sure, yeah.

[803] But now I get the impression that even they realize that things are not looking good for that particular idea.

[804] Again, it depends what you mean by string theory, whether maybe the term will evolve to mean something else, which will work out.

[805] But, yeah, I don't think that's not going to like you to work out.

[806] Whether something else, I mean, I still think it's relatively unlikely that you'll have any really successful theory of anything.

[807] 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 from experiment and and you can you know while it's maybe hard to figure out what people's thinking is going to be 20 years from now looking at um you know energy particle energy colliders and their technology it's actually pretty easy to make a pretty accurate guess what it's going to what except what you're going to be doing 20 years from now and um i think actually i would actually claim that it's pretty clear what where you're going to be 20 years from now and what it's going to be is you're going to have the, you're going to have the LHC, you're going to have a lot more data, an order of magnitude or more or more data from the LHC, but at the same energy, you're not going to, you're not going to see a higher energy accelerator operating successfully in the next 20 years.

[808] And like maybe machine learning or great sort of data science methodologies that process that data will not reveal any major, shift the understanding of the underlying physics, you think?

[809] I don't think so.

[810] I mean, I think 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.

[811] What do you think about the potential quantum computers simulating quantum mechanical systems and through that sneak up to sort of simulate, through simulation?

[812] sneak up to a deep understanding of the fundamental physics.

[813] The problem there is that that's promising more for this, for Phil Anderson's problem, that if you want to, there's lots and lots of, you know, you start pointing together lots and lots of things and we think we know that are pair by pair interactions, but what this thing is going to do, we don't have any good calculational techniques, you know, quantum computers may very well give you those.

[814] And so they may, what we think of as kind of strong coupling behavior, we have no good way to calculate.

[815] You know, even though we can write down the theory, we don't know how to calculate anything with any accuracy in it.

[816] The quantum computers may solve that problem.

[817] But the problem is that they, I don't think that they're going to solve the problem, that they help you with a problem of not having the, of knowing what the right underlying theory is.

[818] as somebody who likes experimental validation let me ask you the perhaps ridiculous sounding but i don't think 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 not really i don't uh it just doesn't uh yeah 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.

[819] To me, it's super interesting from an engineering perspective.

[820] 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.

[821] One is you won't know our human perception systems, and maybe even the tools of physics won't know the difference between the simulated world and the real world.

[822] That's sort of more of a physics question.

[823] The most interesting question to me has more to do with why food tastes delicious, which is 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 want to stay there anyway.

[824] And over time, you don't, even remember.

[825] 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.

[826] So for a physics perspective, it's not useful to you to think, taking a computational perspective to our universe, thinking of as an information processing system, and then think if it as doing computation, and then you think about the resources required to do that kind of computation, and all that kind of stuff.

[827] You could just look at the basic physics and who cares what the computer it's running on is.

[828] Yeah, it just, I mean, the kinds of, 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 found interesting.

[829] And I just, again, I just have to kind of go back to life is too short.

[830] And I'm very glad other people are thinking about this, but I just don't see anything I can do with it.

[831] What about space?

[832] self.

[833] So I have to ask you about aliens.

[834] 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?

[835] I have no idea, but 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's no there seems to be 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 yeah well actually i originally got interested in physics i actually started out as a kid interested in astronomy exactly that and a telescope and whatever that and certainly read a lot of science fiction and thought about that.

[836] I find over the years, I've found myself kind of less, anyway, less and less interested in that, well, just because I don't really know what to do with, I also kind of at some point kind of stopped reading science fiction that much, kind of feeling out that there's just too, that the actual science I was kind of learning about was perfectly kind of weird and fascinating and unusual enough, but better than any of the stuff in Isaac Asimov.

[837] And you can mess with the science, much more than the distant science fiction, the one that's exists in our imagination or the one that exists out there among the stars.

[838] Well, you mentioned science fiction.

[839] You've written quite a few book reviews.

[840] I've got to ask you about some books, perhaps, if you don't mind.

[841] Is there one or two books that you would recommend to others, and maybe if you can, what ideas you drew from them.

[842] Either negative recommendations, a positive recommendation.

[843] Do not read this book for sure.

[844] Well, I must say that, I mean, unfortunately, yeah, you can go to my website and you can click on book reviews and you can see I've written, 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?

[845] And, yeah, so I'm not a fan of a lot of things.

[846] of that kind.

[847] Can I ask you a quick question on this, a small tangent?

[848] 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 awe about the full range of mysteries in our universe.

[849] That's a complicated issue.

[850] 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.

[851] I mean, certainly one, the books that, 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.

[852] It's just kind of a totally fascinating, romantic, great story.

[853] And those were very inspirational to me. And I would think maybe other people might also find them that.

[854] And that's almost like the human story of the development of the ideas.

[855] Yeah, the human story.

[856] But yeah, just also how, you know, they have 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.

[857] In 1905, plank and Einstein, and ending up with the war, when these things get used to, you know, make passively destructive weapons, it's just that truly amazing.

[858] So many new ideas.

[859] Let me, on another, a tangent on top of a tangent, ask, if we didn't have Einstein, so how does science progress?

[860] Is it the lone geniuses?

[861] 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?

[862] Without Einstein, would we have special relativity, general relativity?

[863] I mean, it's an interesting case -to -case basis.

[864] I mean, special relativity, I think we would have had, I mean, there are other people.

[865] Anyway, you could even argue that it was already there in some form and some ways.

[866] I think special relativity you would have had without Einstein fairly quickly.

[867] General relativity, that was a much, much harder thing to do and required a much more effort, much more sophisticated.

[868] I think he would have had sooner or later, but it would have taken quite a bit longer.

[869] That took a bunch of years to validate scientifically, the general relativity.

[870] But even for Einstein, from the point which 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.

[871] That was, you know, I don't forget the number.

[872] The order of magnitude 10 years of very serious work.

[873] And if he hadn't been around to do that, it would have taken a while before anyone else got around to it.

[874] 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, but two different, approaches to it, you know, within months of each other.

[875] And, you know, so if Heisenberg had been there, you already would have had Schrodinger or whatever.

[876] And if neither have been there had been somebody else a few months later.

[877] So there are times when the, you know, just the, a lot, often is 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's going to find it.

[878] maybe to go back to your aliens, I guess the one thing I often wonder about aliens is would they have the same fundamental physics ideas as we, if we have in mathematics, would their math, you know, would they, you know, how much is this really intrinsic to our minds?

[879] If you start out with a different kind of mind, when you end up with the different ideas of what fundamental physics is or what the structure of mathematics is.

[880] So this is why, 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.

[881] 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.

[882] 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 um 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 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 uh what is it several hundred million years to come up with calculus I would just like keep Noting how long it took and 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.

[883] If I was playing a video game and ran the thing, I got a chance to run this whole thing.

[884] Yeah.

[885] But we're talking about books before I distracted us horribly.

[886] Yeah, to go back, books.

[887] 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.

[888] And there's also a very, very good kind of history of, of the kind of what happened during this 20th century in physics.

[889] And, you know, up to the time of the standard model in 1973, it's called the, the second creation by Bob Creus and man. That's one of the best ones.

[890] 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.

[891] 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.

[892] And it's really, the argument people sometimes make in favor of these books as well, oh, you know, they're really a great.

[893] because you want to do something that will get kids excited.

[894] And then, you know, so they're getting excited about things, something that's not really quite working.

[895] It doesn't really matter.

[896] The main thing is get them excited.

[897] The other argument is, you know, wait a minute.

[898] 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.

[899] So there's these problems.

[900] 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.

[901] 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.

[902] You obviously have a much better intuition about physics.

[903] I tend to, in the space of AI, for example, you could use certain kinds of language, like calling things intelligent, that I 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 Alpha Zero does to play chess.

[904] To me, that may not be intelligence, but it's sure that as heck seems like, a few steps down the path towards intelligence.

[905] Yeah.

[906] And so, like, I think that's a very peculiar property of systems that can be engineered.

[907] 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.

[908] In physics, because you're not engineering anything, you're just now swimming in the space directly when you do theoretical physics.

[909] It could be more dangerous.

[910] You could be out too far away from shore.

[911] Yeah.

[912] Well, the problem, I think physics is it 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.

[913] I mean, I spent half my life among mathematicians and half on the physicists.

[914] And, you know, mathematics is kind of doing fine.

[915] People are making progress and it has all the usual problems, but also so you could have a, but you just, I don't know, I've never seen anything at all happening in mathematics like what's happened in the specific area in physics.

[916] It's just the kind of sociology of this, the way this field works banging up against this hard a problem without, anything from experiment to help it, it's really, it's led to some really kind of problematic things.

[917] And those, so it's one thing to kind of, you know, over -simplify or to slightly misrepresent, to try to explain things in a way that's not quite right.

[918] But it's another thing to start promoting the people as a success, as ideas, which really completely failed.

[919] And so, I mean, I'm kind of very, very specific.

[920] Like, if you start 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.

[921] 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, they, you know, the loss of credibility of science is a real.

[922] real, real problem for our society.

[923] And you don't want, you don't want people to have an all too good reason to, to think that what they're being, what they're being told by kind of some of the best institutions or country or authority is, is, is not true.

[924] You know, it's not true.

[925] It's a problem.

[926] That's, it's obviously characteristic of not just physics.

[927] It's, it's sociology.

[928] Yeah.

[929] And it's, I mean, obviously, in the space of politics, it's, it's, it's, I mean, obviously, in the That's the history of politics is you sell ideas to people, even when you don't have any proof that those ideas actually work.

[930] You speak as if they've worked, and that seems to be the case throughout history.

[931] And just like you said, it's human beings running up against a really hard problem.

[932] I'm not sure if this is like a particular, uh like trajectory through the progress of physics that we're dealing with now or is just a natural progress of science you run up against a really difficult stage of a field and uh different people that behave differently in the face of that some sell books and sort of uh tell narratives that are beautiful and so on they're not necessarily grounded in um 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 yeah ants scattering and then you have fields like machine learning which is there's a few folks mostly scattered away from machine learning in the 90s in the winter of AI 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 I want to, they'll just probably keep working on it anyway, sort of like loyal ants to a particular thing.

[933] So it's interesting, but you're sort of saying that we should be careful overhyping things that have not proven themselves because people will lose trust in the scientific process.

[934] 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 behavior as 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 um this particular field is kind of fun mostly it's a it's a it's always a strange one i mean i think it in the sense that there's a lot of public fascination with it that it seems to speak to kind of our deepest questions about you know what is this physical reality where we come from and what and these kind of deep issues so there's this unusual fascination with it mathematics is versus very different nobody 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 so so it's a very unusual it draws this kind of unusual amount of attention and 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 too.

[935] But to push back a little bit, there's power to inspiring people.

[936] And if I just empirically look, physicists are really good at combining science and philosophy and communicating it.

[937] There's something about physics, often that forces you to build a strong intuition about the way reality works.

[938] And that allows you to think through and communicate about all kinds of questions.

[939] If you see physicists, it's always fascinating to take on problems that have nothing to do with their particular discipline.

[940] They think in interesting ways and they're able to communicate their thinking in interesting ways.

[941] And so in some sense, they have a responsibility not just to do science, but to inspire.

[942] and not responsibility but the opportunity and thereby I would say a little bit of a responsibility yeah yeah and something 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, you know, what a high school student think about string theory and not that doesn't matter that 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 and what story you're telling them and what textbooks you're making them read and what they're hearing.

[943] And so a lot of what's motivated me is more to try to speak to a specific population of people to make sure that, look, you know, people, it doesn't matter so much what the average person on the street thinks about string theory, but, you know, what the best students at Columbia or Harvard or Princeton or whatever who really want to change work in this field and want to 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've got to 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.

[944] And is getting into this local pocket of ideas that people hold on to for several decades is not good, no matter what the idea.

[945] I would say, no matter if the idea is right or wrong.

[946] Because there's no such thing as right in the long term.

[947] like it's right for now until somebody builds on something much bigger on top of it.

[948] It might end up being right but being a tiny subset of a much bigger thing.

[949] So you always should question sort of the ways of the past.

[950] Yeah, yeah.

[951] So how to kind of achieve that kind of diversity of thought and within kind of the sociology of how we organize scientific researches.

[952] I know this is one thing that I think it's very interesting that Sabina Hasenfelders very interesting things to say about it.

[953] I think also Lee Smolin in his book, which is also about that, I mean, very much an agreement with them that there's, anyway, there's a really kind of important questions about, you know, how, how research in this field is organized and how people, you know, what can you do to kind of get and get more diversity of thought and get more and get people thinking about, about a wider range of ideas.

[954] At the bottom, I think humility always helps.

[955] Well, the problem is that it's also 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 going to make progress on some of these problems.

[956] I think you have to have like both modes and switch between them when needed.

[957] Let me ask you a question.

[958] You're probably not going to want to answer because you're focused on the mathematics.

[959] 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 i don't know yeah i was thinking about this so the um it did occur me what one interesting thing about that question is that you don't yes i have this life in mathematics and this life in physics and and i see some of my physicist colleagues, you know, 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.

[960] But then I realized that no one ever asked my mathematician colleagues.

[961] Nobody ever asked mathematicians.

[962] Yeah, that's funny.

[963] Everybody just kind of assumes, okay, well, you people are studying about that.

[964] I see, whatever you're doing, it's maybe very interesting, but it's clearly not going to tell me anything useful about the meaning of my life.

[965] 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 might understand that it's a bit misguided to look for deep insight into the meaning of life from many theoretical physicists.

[966] It's not a, they, you know, they're people and they may have interesting things to say about this.

[967] you're right they have they know a lot about physical reality and about about about in some sense about metaphysics about what is is real of this kind but um you're also to my mind i think you're also making a bit of a mistake that you're 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 who are looking for to try to understand in some sense of the meaning of life in 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 yeah 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 but 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 but the unfortunately i think you know people do have a somewhat correct perception that what these people are doing every day, whatever, is pretty far removed from anything, yeah, from what's kind of close to what I'm, what I do every day and what my typical concerns are.

[968] So you may learn something very interesting by talking to mathematicians, but it's, it's probably not going to be, you're probably not going to get what you were hoping.

[969] So when you put the pen and paper down, 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.

[970] Do you think about that?

[971] Your ideas will live on, but you, the human.

[972] Not especially much.

[973] Certainly I've been getting older.

[974] I'm now 64 years old.

[975] You start to realize, well, there's probably less ahead than there was behind.

[976] And so you start to, that starts to become, you know, what do I think about that?

[977] Maybe I should actually get serious about getting something is done, which I, which I may not have, which I may otherwise not have time to do, which I didn't see, and this didn't see to be a problem when I was younger, but that's the main, I think the main way in which that thought occurred.

[978] But it doesn't, you know, the stoics are big on this, meditating on mortality, helps you more intensely appreciate the beauty when you do experience it.

[979] I suppose that's true, but it's not, yeah, it's not something I've spent a lot of lot of time trying but um but yeah day to day you just enjoy the puzzles the mathematics just enjoy yeah our life in general life is have a perfectly pleasant life and enjoy enjoy it and often think wow this is things are i'm really enjoying this things are going well yeah life is pretty amazing yeah i think uh you and i are pretty lucky we get to uh live on this nice little earth yeah with a nice little comfortable climate and we get to have this nice nice little comfortable climate and we'll get to have this little podcast conversation, thank you so much for spending your valuable time with me today and having this conversation.

[980] Thank you.

[981] Thank you.

[982] Thanks for listening to this conversation with Peter White.

[983] To support this podcast, please check out our sponsors in the description.

[984] And now, let me leave you some words from Richard Feynman.

[985] The first principle is that you must not fool yourself, and you are the easiest person to fool.

[986] Thank you for listening, and hope to see you next time.