Peter Woit: Theories of Everything & Why String Theory is Not Even Wrong

00:00:00.000 | The following is a conversation with Peter White,

00:00:02.480 | a theoretical physicist at Columbia,

00:00:04.760 | outspoken critic of string theory,

00:00:06.640 | and the author of the popular physics

00:00:09.040 | and mathematics blog called "Not Even Wrong."

00:00:12.560 | This is the Lex Friedman Podcast.

00:00:15.600 | To support it, please check out our sponsors

00:00:17.600 | in the description.

00:00:18.760 | And now, here's my conversation with Peter White.

00:00:22.400 | You're both a physicist and a mathematician.

00:00:27.360 | So let me ask, what is the difference

00:00:29.040 | between physics and mathematics?

00:00:31.720 | - Well, there's kind of a conventional understanding

00:00:33.800 | of the subject that they're two quite different things.

00:00:37.320 | So that mathematics is about making rigorous statements

00:00:41.600 | about these abstract things, things of mathematics,

00:00:46.600 | and proving them rigorously.

00:00:48.400 | And physics is about doing experiments

00:00:51.040 | and testing various models and that.

00:00:53.960 | But I think the more interesting thing

00:00:55.920 | is that there's a wide variety

00:01:00.280 | of what people do as mathematics,

00:01:01.560 | what they do as physics,

00:01:02.560 | and there's a significant overlap.

00:01:04.080 | And that I think is actually a very interesting area.

00:01:09.040 | And if you go back kind of far enough in history

00:01:12.640 | and look at figures like Newton or something,

00:01:15.800 | at that point, you can't really tell

00:01:17.320 | was Newton a physicist or a mathematician.

00:01:19.200 | The mathematicians will tell you he was a mathematician,

00:01:21.760 | the physicists will tell you he was a physicist.

00:01:23.400 | But he would say he's a philosopher.

00:01:26.360 | (laughing)

00:01:27.200 | Yeah, that's interesting.

00:01:28.920 | But yeah, anyway, there was kind of no such distinction

00:01:32.440 | then that's more of a modern thing.

00:01:35.040 | But anyway, I think these days,

00:01:36.120 | there's a very interesting space in between the two.

00:01:38.120 | - So in the story of the 20th century

00:01:40.840 | and the early 21st century,

00:01:42.400 | what is the overlap between mathematics and physics,

00:01:44.680 | would you say?

00:01:46.000 | - Well, I think it's actually become very, very complicated.

00:01:49.840 | I think it's really interesting to see a lot

00:01:51.880 | of what my colleagues in the math department are doing.

00:01:54.760 | They, most of what they're doing,

00:01:56.920 | they're doing all sorts of different things,

00:01:58.160 | but most of them have some kind of overlap

00:02:00.400 | with physics or other.

00:02:02.400 | So, I mean, I'm personally interested

00:02:03.880 | in one particular aspect of this overlap,

00:02:06.680 | which I think has a lot to do

00:02:08.520 | with the most fundamental ideas about physics

00:02:10.320 | and about mathematics.

00:02:12.080 | But there's just, you kind of see this,

00:02:15.520 | this really, really everywhere at this point.

00:02:18.920 | - Which particular overlap are you looking at, group theory?

00:02:22.480 | - Yeah, so the, at least what the way it seems to me

00:02:26.320 | that if you look at physics and look at the,

00:02:28.160 | our most successful laws of fundamental physics,

00:02:31.880 | they're really, you know,

00:02:33.520 | they have a certain kind of mathematical structure.

00:02:35.360 | It's based upon certain kinds of mathematical objects

00:02:38.200 | and geometry connections and curvature,

00:02:40.720 | the spinners, the Dirac equation.

00:02:43.820 | And that, these, this very deep mathematics

00:02:47.400 | provides kind of a unifying set of ways of thinking

00:02:51.880 | that allow you to make a unified theory of physics.

00:02:54.800 | But the interesting thing is that if you go to mathematics

00:02:57.600 | and look at what's been going on in mathematics

00:03:00.640 | the last 1,500 years, and even especially recently,

00:03:04.780 | there's a similarly, some kind of unifying ideas

00:03:08.760 | which bring together different areas of mathematics

00:03:10.840 | and which have been especially powerful

00:03:12.520 | in number theory recently.

00:03:13.680 | And there's a book, for instance,

00:03:15.680 | by Edward Frankel about love and math.

00:03:19.040 | - Yeah, that book's great.

00:03:20.320 | I recommend it highly.

00:03:21.320 | It's partially accessible.

00:03:24.160 | But it is a nice audio book that I listened to

00:03:27.800 | while running an exceptionally long distance,

00:03:31.920 | like across the San Francisco Bridge.

00:03:35.500 | And there's something magic about the way he writes about it

00:03:38.960 | but some of the group theory in there

00:03:40.520 | is a little bit difficult.

00:03:42.240 | - Yeah, that's the problem with any of these things,

00:03:44.000 | to kind of really say what's going on

00:03:45.920 | and make it accessible is very hard.

00:03:48.880 | He, in this book and elsewhere, I think,

00:03:50.920 | takes the attitude that kinds of mathematics

00:03:53.680 | he's interested in and that he's talking about

00:03:56.000 | are provide kind of a grand unified theory of mathematics.

00:03:59.280 | They bring together geometry and number theory

00:04:03.200 | and representation theory, a lot of different ideas

00:04:06.880 | in a really unexpected way.

00:04:09.760 | But I think to me, the most fascinating thing

00:04:11.460 | is if you look at the kind of grand unified theory

00:04:13.880 | of mathematics he's talking about

00:04:15.480 | and you look at the physicist's kind of ideas

00:04:17.560 | about unification, it's more or less

00:04:19.840 | the same mathematical objects are appearing in both.

00:04:22.600 | So it's this, I think there's a really,

00:04:24.880 | we're seeing a really strong indication

00:04:26.440 | that the deepest ideas that we're discovering about physics

00:04:30.240 | and some of the deepest ideas

00:04:31.520 | that mathematicians are learning about

00:04:33.200 | are really, are intimately connected.

00:04:36.120 | - Is there something, like if I was five years old

00:04:38.840 | and you were trying to explain this to me,

00:04:40.600 | is there ways to try to sneak up

00:04:43.440 | to what this unified world of mathematics looks like?

00:04:47.360 | You said number theory, you said geometry,

00:04:50.160 | words like topology.

00:04:52.480 | What does this universe begin to look like?

00:04:54.480 | Are these, what should we imagine in our mind?

00:04:57.480 | Is it a three-dimensional surface?

00:05:00.800 | And we're trying to say something about it.

00:05:03.200 | Is it triangles and squares and cubes?

00:05:07.280 | Like what are we supposed to imagine in our minds?

00:05:09.440 | Is this natural number?

00:05:10.520 | What's a good thing to try to,

00:05:13.840 | for people that don't know any of these tools

00:05:16.760 | except maybe some basic calculus and geometry

00:05:18.960 | from high school, that they should keep in their minds

00:05:22.200 | as to the unified world of mathematics

00:05:24.840 | that also allows us to explore

00:05:28.000 | the unified world of physics?

00:05:29.560 | - I mean, what I find kind of remarkable about this

00:05:33.080 | is the way in which these, we've discovered these ideas,

00:05:38.080 | but they're actually quite alien

00:05:40.240 | to our everyday understanding.

00:05:42.240 | You know, we grow up in this three-spatial dimensional world

00:05:45.600 | and we have intimate understanding

00:05:47.480 | of certain kinds of geometry and certain kinds of things,

00:05:50.440 | but these things that we've discovered

00:05:53.520 | in both math and physics are,

00:05:56.040 | that they're not at all close,

00:05:58.280 | have any obvious connection

00:05:59.800 | to kind of human everyday experience.

00:06:01.640 | They're really quite different.

00:06:03.000 | And I can say some of my initial fascination with this

00:06:06.000 | when I was young and starting to learn about it

00:06:08.360 | was actually exactly this kind of arcane nature

00:06:13.360 | of these things.

00:06:14.960 | It's a little bit like being told,

00:06:17.400 | well, there are these kind of semi-mystical experience

00:06:21.000 | that you can acquire by a long study and whatever,

00:06:24.320 | except that it was actually true

00:06:26.720 | and there's actually evidence that this actually works.

00:06:29.520 | So, I'm a little bit wary of trying to give people

00:06:33.240 | that kind of thing, 'cause I think it's mostly misleading.

00:06:35.160 | But one thing to say is that, you know,

00:06:36.440 | that geometry is a large part of it.

00:06:39.840 | And maybe one interesting thing to say

00:06:43.240 | that's about more recent, some of the most recent ideas

00:06:45.760 | is that when we think about the geometry

00:06:48.400 | of our space and time,

00:06:50.000 | it's kind of three spatial and one time dimension.

00:06:53.360 | It's a, physics is in some sense

00:06:56.720 | about something that's kind of four dimensional in a way.

00:07:00.760 | And a really interesting thing

00:07:02.680 | about some of the recent developments in number theory

00:07:06.120 | have been to realize that these ideas

00:07:09.920 | that we were looking at naturally fit into a context

00:07:12.720 | where your theory is kind of four dimensional.

00:07:15.840 | So, I mean, geometry is a big part of this

00:07:19.800 | and we know a lot and feel a lot about, you know,

00:07:22.120 | two, one, two, three dimensional geometry.

00:07:24.600 | - So, wait a minute.

00:07:25.560 | So, we can at least rely on the four dimensions

00:07:30.280 | of space and time and say that we can get pretty far

00:07:32.920 | by working that in those four dimensions?

00:07:35.640 | I thought you were gonna scare me

00:07:36.720 | that we're gonna have to go to many, many, many, many

00:07:39.280 | more dimensions than that.

00:07:41.080 | - My point of view, which goes against a lot of these ideas

00:07:44.160 | about unification is that, no, this is really,

00:07:46.480 | everything we know about really is about four dimensions

00:07:50.600 | that, and that you can actually understand

00:07:54.320 | a lot of these structures that we've been seeing

00:07:56.000 | in fundamental physics and in number theory,

00:07:59.040 | just in terms of four dimensions,

00:08:01.480 | that it's kind of, it's in some sense,

00:08:03.560 | I would claim has been a really,

00:08:07.440 | has been kind of a mistake that physicists have made

00:08:10.800 | in, for decades and decades, to try to,

00:08:13.840 | to try to go to higher dimensions,

00:08:16.560 | to try to formulate a theory in higher dimensions,

00:08:19.040 | and then you're stuck with the problem

00:08:21.600 | of how do you get rid of all these extra dimensions

00:08:23.400 | that you've created, 'cause we only ever see anything

00:08:26.440 | in four dimensions.

00:08:27.440 | - That kind of thing leads us astray, you think?

00:08:29.960 | So, creating all these extra dimensions just to get,

00:08:32.800 | give yourself extra degrees of freedom.

00:08:34.760 | - Yeah.

00:08:36.640 | - I mean, isn't that the process of mathematics,

00:08:38.400 | is to create all these trajectories for yourself,

00:08:41.320 | but eventually you have to end up at the,

00:08:43.440 | at like a final place, but it's okay to,

00:08:47.040 | it's okay to sort of create abstract objects

00:08:52.640 | on your path to proving something.

00:08:55.920 | - Yeah, yeah, certainly, but,

00:08:57.280 | and from a mathematician's point of view,

00:08:59.640 | I mean, the kinds of,

00:09:01.360 | mathematicians are also very different than physicists

00:09:03.480 | in that we like to develop very general theories.

00:09:06.080 | We like to, if we have an idea,

00:09:07.240 | we want to see what's the greatest generality

00:09:09.720 | in which you can talk about it.

00:09:11.200 | So, from the point of view of most of the ways

00:09:13.760 | geometry is formulated by mathematicians,

00:09:17.040 | it really doesn't matter, it works in any dimension.

00:09:19.120 | We can do one, two, three, four, any number.

00:09:22.120 | There's no particular, for most of geometry,

00:09:24.840 | there's no particular special thing about four,

00:09:28.240 | but anyway, but what physicists have been trying

00:09:33.000 | to do over the years is try to understand

00:09:35.800 | these fundamental theories in a geometrical way,

00:09:38.320 | and it's very tempting to kind of just start bringing in

00:09:41.960 | extra dimensions and using them to explain the structure,

00:09:46.240 | but typically this attempt kind of founders

00:09:51.240 | because you just don't know,

00:09:53.380 | you end up not being able to explain why we only see four.

00:09:57.160 | - It is nice in the space of physics that,

00:10:02.360 | like if you look at Fermat's last theorem,

00:10:04.560 | it's much easier to prove that there's no solution

00:10:06.680 | for n equals three than it is for the general case,

00:10:10.760 | and so I guess that's the nice benefit of being a physicist

00:10:16.360 | is you don't have to worry about the general case

00:10:18.640 | 'cause we live in a universe with n equals four,

00:10:22.160 | in this case.

00:10:23.440 | - Yeah, physicists are very interested in saying something

00:10:27.880 | about specific examples, and I find that interesting.

00:10:31.440 | When I'm trying to do things in mathematics,

00:10:33.760 | when I'm trying even teaching courses

00:10:35.320 | and to mathematics students,

00:10:36.920 | I find that I'm teaching them in a different way

00:10:40.200 | than most mathematicians because I'm very often

00:10:43.880 | very focused on examples, on what's kind of

00:10:47.320 | the crucial example that shows how this powerful

00:10:51.760 | new mathematical technique, how it works,

00:10:53.480 | and why you would want to do it,

00:10:55.680 | and I'm less interested in kind of proving a precise theorem

00:11:00.040 | about exactly when it's gonna work

00:11:01.400 | and when it's not gonna work.

00:11:02.440 | - Do you usually think about really simple examples,

00:11:05.160 | like both for teaching and when you try to solve

00:11:09.080 | a difficult problem?

00:11:10.480 | Are you, do you construct the simplest possible examples

00:11:13.040 | that captures the fundamentals of the problem

00:11:14.840 | and try to solve it?

00:11:15.720 | - Yeah, yeah, exactly.

00:11:17.080 | That's often a really fruitful way to,

00:11:20.080 | if you've got some idea, to just kind of try to boil it down

00:11:23.920 | to what's the simplest situation in which this kind of thing

00:11:27.840 | is gonna happen and then try to really understand that

00:11:31.320 | and that is almost always a really good way

00:11:33.520 | to get insight into it.

00:11:34.520 | - Do you work with paper and pen or, like, for example,

00:11:37.760 | for me, coming from the programming side,

00:11:41.600 | if I look at a model, if I look at some kind

00:11:43.880 | of mathematical object, I like to mess around with it

00:11:48.120 | sort of numerically.

00:11:49.640 | I just visualize different parts of it,

00:11:51.680 | visualize however I can, so most of the work

00:11:54.200 | is like with neural networks, for example,

00:11:56.200 | is you try to play with the simplest possible example

00:11:59.400 | and just to build up intuition by, you know,

00:12:03.440 | any kind of object has a bunch of variables in it.

00:12:05.880 | You start to mess around with them in different ways

00:12:09.040 | and visualize in different ways to start to build intuition.

00:12:11.960 | Or do you go the Einstein route and just imagine, like,

00:12:16.960 | everything inside your mind and sort of build, like,

00:12:20.240 | thought experiments and then work purely on paper and pen?

00:12:24.840 | - Well, the problem with this kind of stuff

00:12:28.120 | I'm interested in is you rarely can kind of,

00:12:31.880 | it's rarely something that is really kind of,

00:12:34.800 | or even the simplest example, you know,

00:12:37.840 | you can kind of see what's going on

00:12:39.200 | by looking at something happening in three dimensions.

00:12:42.280 | There's generally the structures involved are,

00:12:44.920 | either they're more abstract or if you try to kind of

00:12:49.000 | embed them in some kind of space where you could

00:12:51.440 | manipulate them in some kind of geometrical way,

00:12:55.200 | it's gonna be a much higher dimensional space.

00:12:57.320 | - So even simple examples,

00:13:00.120 | the embedding them into three dimensional space,

00:13:02.080 | you're losing a lot.

00:13:03.040 | - Yeah, but to capture what you're trying to understand

00:13:06.960 | about them, you have to go to four or more dimensions.

00:13:09.720 | So it starts to get to be hard to,

00:13:12.040 | and you can train yourself to try it as much as to kind of

00:13:15.680 | think about things in your mind.

00:13:18.200 | And, you know, I often use pad and paper

00:13:21.000 | and I'm often, in my office I often use the blackboard.

00:13:24.440 | And you are kind of drawing things,

00:13:26.920 | but they're really kind of more abstract representations

00:13:29.600 | of how things are supposed to fit together.

00:13:32.560 | And they're not really, unfortunately,

00:13:35.240 | not just kind of really living in three dimensions

00:13:37.640 | where you can understand.

00:13:39.200 | - Are we supposed to be sad or excited

00:13:41.600 | by the fact that our human minds can't fully comprehend

00:13:44.120 | the kind of mathematics you're talking about?

00:13:46.000 | I mean, what do we make of that?

00:13:48.720 | I mean, to me, that makes me quite sad.

00:13:50.720 | It makes me, it makes it seem like

00:13:52.680 | there's a giant mystery out there

00:13:54.000 | that we'll never truly get to experience directly.

00:13:58.320 | - It is kind of sad, you know, how difficult this is.

00:14:01.720 | I mean, or I would put it a different way that,

00:14:04.040 | you know, most questions that people have about

00:14:07.440 | this kind of thing, you know, you can give them

00:14:10.680 | a really, a true answer and really understand it,

00:14:13.080 | but the problem is one more of time.

00:14:16.600 | It's like, yes, you know, I could explain to you

00:14:19.600 | how this works, but you'd have to be willing to

00:14:22.360 | sit down with me and, you know, work at this repeatedly

00:14:25.080 | for, you know, for hours and days and weeks.

00:14:28.040 | And you'd have, I mean, it's just gonna take that long

00:14:30.920 | for your mind to really wrap itself around what's going on.

00:14:34.400 | And that, so that does make things inaccessible,

00:14:38.480 | which is sad, but I mean, it's just kind of part of life

00:14:43.040 | that we all have a limited amount of time

00:14:45.040 | and we have to decide what we're gonna,

00:14:47.720 | what we're gonna spend our time doing.

00:14:49.800 | - Speaking of a limited amount of time,

00:14:52.320 | we only have a few hours, maybe a few days together

00:14:55.640 | here on this podcast.

00:14:56.880 | Let me ask you the question of amongst many of the ideas

00:15:02.320 | that you work on in mathematics and physics,

00:15:05.240 | what is the most beautiful idea,

00:15:07.560 | or one of the most beautiful ideas, maybe a surprising idea?

00:15:11.200 | And once again, unfortunately, the way life works,

00:15:13.960 | we only have a limited time together

00:15:15.680 | to try to convey such an idea.

00:15:18.440 | - Okay, well, actually, let me just tell you something,

00:15:21.760 | which I've attempted to kind of start trying to explain

00:15:25.240 | what I think is this most powerful idea

00:15:26.960 | that brings together math and physics,

00:15:28.600 | ideas about groups and representations

00:15:31.040 | and how it fits to quantum mechanics.

00:15:33.200 | But in some sense, I wrote a whole textbook about that,

00:15:35.560 | and I don't think we really have time

00:15:37.440 | to get very far into it, so.

00:15:39.080 | - Well, can I actually, on a small tangent,

00:15:41.080 | you did write a paper towards

00:15:42.520 | the Grant Unified Theory of Mathematics and Physics.

00:15:45.080 | Maybe you could step there first.

00:15:47.840 | What is the key idea in that paper?

00:15:49.520 | - Well, I think we've kind of gone over that.

00:15:51.480 | I think that the key idea

00:15:52.600 | is what we were talking about earlier,

00:15:54.040 | that just kind of a claim that if you look

00:15:58.400 | and see what's the have been successful ideas

00:16:00.480 | of unification in physics over the last 50 years or so,

00:16:05.200 | and what has been happening in mathematics

00:16:07.800 | and the kind of thing that Frankl's book is about,

00:16:10.840 | that these are very much the same kind of mathematics.

00:16:13.040 | And so it's kind of an argument that there really is,

00:16:16.460 | you shouldn't be looking to unify just math

00:16:19.760 | or just fundamental physics,

00:16:21.880 | but taking inspiration for looking for new ideas

00:16:24.640 | in fundamental physics,

00:16:25.600 | that they are gonna be in the same direction

00:16:27.400 | of getting deeper into mathematics

00:16:30.240 | and looking for more inspiration in mathematics

00:16:33.320 | from these successful ideas about fundamental physics.

00:16:37.340 | - Could you put words to sort of the disciplines

00:16:39.520 | we're trying to unify?

00:16:40.440 | So you said number theory.

00:16:41.960 | Are we literally talking about

00:16:43.160 | all the major fields of mathematics?

00:16:45.080 | So it's like the number theory, geometry,

00:16:48.320 | so like differential geometry, topology?

00:16:51.040 | - Yeah, so the, I mean, one name for this,

00:16:55.240 | that this is acquired in mathematics

00:16:57.640 | is the so-called Langlands program.

00:16:59.800 | And so this started out in mathematics.

00:17:02.000 | It's that, you know, Robert Langlands kind of realized

00:17:05.160 | that a lot of what people were doing in,

00:17:07.840 | that was starting to be really successful

00:17:10.960 | in number theory in the '60s.

00:17:13.640 | And so that this actually was,

00:17:17.820 | anyway, that this could be thought of

00:17:21.160 | in terms of these ideas about symmetry

00:17:24.120 | in groups and representations,

00:17:26.120 | and in a way that was also close

00:17:29.600 | to some ideas about geometry.

00:17:32.040 | And then more later on in the '80s and '90s,

00:17:35.200 | there was something called geometric Langlands

00:17:38.120 | that people realized that you could take

00:17:40.480 | what people have been doing in number theory in Langlands

00:17:43.120 | and get rid, just forget about the number theory

00:17:45.560 | and ask, what is this telling you about geometry?

00:17:47.960 | And you get a whole, some new insights

00:17:49.960 | into certain kinds of geometry that way.

00:17:52.360 | So it's, anyway, that's kind of the name for this area

00:17:55.560 | is Langlands and geometric Langlands.

00:17:58.080 | And just recently in the last few months,

00:17:59.680 | there's been, there's kind of a really major paper

00:18:02.760 | that appeared by Peter Schultze and Laurent Farg,

00:18:06.660 | where they, you know, made, you know,

00:18:09.560 | some serious advance and try to understand

00:18:12.920 | very much kind of a local problem

00:18:15.960 | of what happens in number theory

00:18:17.960 | near a certain prime number.

00:18:19.720 | And they turned this into a problem

00:18:22.000 | of exactly the kind that geometric Langlands people

00:18:26.000 | had been doing, this kind of pure geometry problem.

00:18:28.840 | And they found by generalizing the mathematics,

00:18:32.320 | they could actually reformulate it in that way,

00:18:34.240 | and it worked perfectly well.

00:18:36.640 | - One of the things that makes me sad is, you know,

00:18:40.600 | I'm a pretty knowledgeable person in the,

00:18:44.880 | what is it, at least I'm in the neighborhood

00:18:47.960 | of like theoretical computer science, right?

00:18:50.480 | And it's still way out of my reach.

00:18:52.320 | And so many people talk about, like Langlands, for example,

00:18:54.920 | is one of the most brilliant people in mathematics

00:18:57.640 | and just really admire his work.

00:18:59.960 | And I can't, it's like almost I can't hear the music

00:19:03.720 | that he composed, and it makes me sad.

00:19:05.800 | - Yeah, well, I mean, I think that, unfortunately,

00:19:09.000 | it's not just you, it's I think even most mathematicians

00:19:13.200 | have no, really don't actually understand

00:19:15.120 | what this is about.

00:19:15.960 | I mean, the group of people who really understand

00:19:19.400 | all these ideas, and so for instance,

00:19:21.040 | this paper of Schultz and Farag,

00:19:23.280 | that I was talking about, the number of people

00:19:24.840 | who really actually understand how that works is,

00:19:28.320 | anyway, very, very small.

00:19:30.960 | And so it's, so I think even you find,

00:19:34.080 | if you talk to mathematicians and physicists,

00:19:35.840 | even they will often feel that, you know,

00:19:37.960 | there's this really interesting sounding stuff going on,

00:19:40.280 | and which I should be able to understand.

00:19:42.840 | It's kind of in my own field I have a PhD in,

00:19:44.960 | but it still seems pretty clearly far beyond me right now.

00:19:48.340 | - Well, if we can step into the,

00:19:51.800 | back to the question of beauty,

00:19:54.040 | is there an idea that maybe is a little bit smaller

00:19:58.480 | that you find beautiful in the space

00:19:59.960 | of mathematics or physics?

00:20:01.760 | - There's an idea that, you know,

00:20:03.320 | I kind of went, got a physics PhD

00:20:05.280 | and spent a lot of time learning about mathematics.

00:20:07.080 | And I guess it was embarrassing

00:20:09.960 | that I hadn't really actually understood

00:20:11.680 | this very simple idea until,

00:20:14.480 | and kind of learned it

00:20:15.560 | when I actually started teaching math classes,

00:20:18.120 | which is maybe that there,

00:20:21.440 | maybe there's a simple way to explain

00:20:23.760 | kind of the fundamental way in which algebra

00:20:26.080 | and geometry are connected.

00:20:28.040 | So you normally think of geometry

00:20:29.960 | as about these spaces and these points,

00:20:32.560 | and you think of algebra as this very abstract thing

00:20:36.400 | about these abstract objects

00:20:38.760 | that satisfy certain kinds of relations.

00:20:40.640 | You can multiply them and add them and do stuff,

00:20:44.320 | but it's completely abstract.

00:20:45.960 | It has nothing geometric about it.

00:20:47.680 | But the kind of really fundamental idea

00:20:51.640 | is that unifies algebra and geometry

00:20:54.640 | is to realize, is to think,

00:20:57.200 | whenever anybody gives you what you call an algebra,

00:21:00.800 | some abstract thing of things that you can multiply and add,

00:21:04.280 | that you should ask yourself,

00:21:06.400 | is that algebra the space of functions on some geometry?

00:21:10.640 | So one of the most surprising examples of this,

00:21:12.600 | for instance, is a standard kind of thing

00:21:16.880 | that seems to have nothing to do with geometry

00:21:18.680 | is the integers.

00:21:22.000 | So you can multiply them and add them.

00:21:24.800 | It's an algebra,

00:21:27.440 | but it seems to have nothing to do with geometry.

00:21:31.040 | But what you can, it turns out,

00:21:32.200 | but if you ask yourself this question

00:21:33.760 | and ask, is our integers,

00:21:36.280 | can you think if somebody gives you an integer,

00:21:37.800 | can you think of it as a function on some space,

00:21:40.840 | on some geometry?

00:21:42.240 | And it turns out that yes, you can.

00:21:44.320 | And the space is the space of prime numbers.

00:21:47.280 | And so what you do is you just,

00:21:48.640 | if somebody gives you an integer,

00:21:50.440 | you can make a function on the prime numbers

00:21:53.160 | by just at each prime number,

00:21:55.360 | taking that integer modulo, that prime.

00:21:58.920 | So if, as you say, I don't know,

00:22:00.880 | if you're given 10, you know, 10,

00:22:03.840 | and you ask what is its value at two?

00:22:05.600 | Well, it's five times two.

00:22:07.920 | So mod two, it's zero.

00:22:09.680 | So it has zero one.

00:22:10.680 | What is its value at three?

00:22:13.680 | Well, it's nine plus one.

00:22:15.240 | So it's one mod three.

00:22:17.440 | So it's zero at two, it's one at three,

00:22:19.960 | and you can kind of keep going.

00:22:21.920 | And so this is really kind of a truly fundamental idea.

00:22:26.920 | It's at the basis of what's called algebraic geometry.

00:22:29.280 | And it just links these two parts of mathematics

00:22:31.400 | that look completely different.

00:22:32.920 | And it's just an incredibly powerful idea.

00:22:35.120 | And so much of mathematics emerges

00:22:37.240 | from this kind of simple relation.

00:22:39.760 | - So you're talking about mapping

00:22:41.760 | from one discrete space to another.

00:22:44.520 | For a second, I thought perhaps mapping

00:22:49.600 | like a continuous space to a discrete space,

00:22:51.600 | like functions over a continuous space.

00:22:53.600 | 'Cause, yeah.

00:22:56.320 | - Well, you can take, if somebody gives you a space,

00:23:00.000 | you can ask, you can say, well, let's,

00:23:03.200 | and this is also, this is part of the same idea.

00:23:05.240 | The part of the same idea is that

00:23:06.440 | if you try and do geometry

00:23:08.160 | and somebody tells you here's a space,

00:23:10.560 | that what you should do is you should wait.

00:23:11.920 | So say, wait a minute,

00:23:12.760 | maybe I should be trying to solve this using algebra.

00:23:15.760 | And so if I do that, the way to start is

00:23:18.280 | you give me the space,

00:23:19.680 | I start to think about the functions of the space.

00:23:22.320 | Okay, so for each point in the space,

00:23:24.240 | I associate a number.

00:23:26.160 | I can take different kinds of functions

00:23:27.640 | and different kinds of values,

00:23:29.120 | but basically functions on a space.

00:23:31.600 | So what this insight is telling you is that

00:23:36.320 | if you're a geometer,

00:23:37.320 | often the way to work is to change your problem

00:23:41.200 | into algebra by changing your space.

00:23:43.200 | Stop thinking about your space and the points in it

00:23:45.960 | and think about the functions on it.

00:23:48.240 | And if you're an algebraist

00:23:49.800 | and you've got these abstract algebraic gadgets

00:23:52.260 | that you're multiplying and adding,

00:23:54.040 | say, wait a minute, are those gadgets,

00:23:57.040 | can I think of them in some way as a function on a space?

00:23:59.720 | What would that space be?

00:24:00.800 | And what kind of functions would they be?

00:24:02.920 | And that going back and forth really brings these two

00:24:06.780 | completely different looking areas of mathematics together.

00:24:09.640 | - Do you have particular examples

00:24:12.360 | where it allowed to prove some difficult things

00:24:15.040 | by jumping from one to the other?

00:24:16.800 | Is that something that's a part of modern mathematics

00:24:19.720 | where such jumps are made?

00:24:21.720 | - Oh, yes, this is kind of all the time.

00:24:23.440 | A lot, much of modern number theory

00:24:25.400 | is kind of based on this idea.

00:24:27.220 | But, and when you start doing this,

00:24:29.940 | you start to realize that you need,

00:24:31.680 | what simple things on one side of the algebra

00:24:37.560 | start to require you to think about

00:24:40.280 | the other side about geometry in a new way.

00:24:42.400 | You have to kind of get a more sophisticated idea

00:24:44.160 | about geometry.

00:24:45.000 | Or if you start thinking about the functions on a space,

00:24:49.140 | you may need a more sophisticated kind of algebra.

00:24:52.040 | But in some sense, I mean,

00:24:53.980 | much or most of modern number theory

00:24:55.580 | is based upon this move to geometry.

00:24:58.940 | And there's also a lot of geometry

00:25:01.260 | and topology is also based upon.

00:25:03.200 | Yeah, change, change.

00:25:05.060 | If you wanna understand the topology of something,

00:25:06.820 | you look at the functions, you do Durham cohomology,

00:25:09.500 | and you get the topology.

00:25:11.400 | Anyway.

00:25:13.660 | - Well, let me ask you then the ridiculous question.

00:25:16.260 | You said that this idea is beautiful.

00:25:18.980 | Can you formalize the definition of the word beautiful?

00:25:22.700 | And why is this beautiful?

00:25:24.300 | Like, first, why is this beautiful?

00:25:26.260 | And second, what is beautiful?

00:25:29.740 | - Yeah, well, I think there are many different things

00:25:32.340 | you can find beautiful for different reasons.

00:25:34.140 | I mean, I think in this context,

00:25:36.300 | the notion of beauty, I think really is just kind of,

00:25:40.180 | an idea is beautiful if it packages a huge amount

00:25:44.220 | of kind of power and information into something very simple.

00:25:48.820 | So in some sense, you can almost kind of try and measure it

00:25:53.820 | in the sense of what are the implications of this idea?

00:25:58.340 | What non-trivial things does it tell you

00:26:00.900 | versus how simply can you express the idea?

00:26:05.900 | - So the level of compression,

00:26:08.560 | what is it, correlates with beauty?

00:26:12.420 | - Yeah, that's one aspect of it.

00:26:15.020 | And so you can start to tell that an idea

00:26:16.860 | is becoming uglier and uglier as you start kind of having to,

00:26:21.100 | you know, it doesn't quite do what you want,

00:26:22.420 | so you throw in something else to the idea

00:26:24.580 | and you keep doing that until you get what you want.

00:26:27.380 | But that's how you know you're doing something uglier

00:26:29.580 | and uglier, when you have to kind of keep adding in more,

00:26:34.580 | more into what was originally a fairly simple idea

00:26:38.540 | and making it more and more complicated

00:26:40.420 | to get what you want.

00:26:41.860 | - Okay, so let's put some philosophical words on the table

00:26:45.380 | and try to make some sense of them.

00:26:47.100 | One word is beauty, another one is simplicity,

00:26:49.780 | as you mentioned, another one is truth.

00:26:52.240 | So do you have a sense, if I give you two theories,

00:26:57.060 | one is simpler, one is more complicated.

00:27:01.400 | Do you have a sense of which one is more likely to be true

00:27:05.820 | to capture deeply the fabric of reality?

00:27:10.820 | The simple one or the more complicated one?

00:27:15.060 | - Yeah, I think all of our evidence,

00:27:18.540 | what we see in the history of the subject

00:27:20.100 | is the simpler one, though often it's a surprise,

00:27:24.460 | it's simpler in a surprising way,

00:27:26.300 | but yeah, that we just don't, we just,

00:27:29.840 | anyway, the kind of best theories we've been coming up with

00:27:34.140 | are ultimately, when properly understood,

00:27:37.500 | relatively simple and much, much simpler

00:27:40.220 | than you would expect them to be.

00:27:41.860 | - Do you have a good explanation why that is?

00:27:43.500 | Is it just 'cause humans want it to be that way?

00:27:46.020 | Are we just like ultra-biased

00:27:47.540 | and we just kinda convince ourselves

00:27:51.100 | that simple is better 'cause we find simplicity beautiful?

00:27:53.740 | Or is there something about our actual universe

00:27:57.340 | that at the core is simple?

00:28:00.060 | - My own belief is that there is something about

00:28:02.500 | a universe that's simple, and as I was trying to say,

00:28:05.260 | that there is some kind of fundamental thing

00:28:07.260 | about math, physics, and physics, and all this picture,

00:28:10.500 | which is in some sense simple.

00:28:14.460 | It's true that, it's of course true that our minds

00:28:18.580 | have certain, are very limited and can certainly do

00:28:22.340 | certain things and not others, so it's in principle possible

00:28:26.500 | that there's some great insight,

00:28:29.380 | there are a lot of insights into the way the world works,

00:28:31.300 | which just aren't accessible to us

00:28:32.700 | because that's not the way our minds work, we don't,

00:28:35.540 | and that what we're seeing, this kind of simplicity,

00:28:37.340 | is just because that's all we ever have any hope of seeing.

00:28:41.300 | - So there's a brilliant physicist

00:28:46.100 | by the name of Sabine Hasenfelder,

00:28:49.020 | who both agrees and disagrees with you,

00:28:51.020 | or I suppose agrees that the final answer will be simple.

00:28:56.020 | - Yeah.

00:28:58.300 | - But simplicity and beauty leads us astray

00:29:01.580 | in the local pockets of scientific progress.

00:29:05.900 | Do you agree with her disagreement,

00:29:08.700 | do you disagree with her agreement?

00:29:11.140 | And agree with the agreement, and so on.

00:29:14.180 | - Yes, I found it was really fascinating reading her book,

00:29:17.700 | and anyway, I was finding disagreeing with a lot,

00:29:21.420 | but then at the end when she says yes,

00:29:23.340 | when we find, when we actually figure this out,

00:29:26.580 | it will be simple, and okay, so we agree in the end.

00:29:31.220 | - But does beauty lead us astray,

00:29:32.860 | which is the core thesis of her work in that book?

00:29:37.620 | - I actually, I guess I do disagree with her on that so much.

00:29:41.140 | I don't think, and especially,

00:29:42.620 | and I actually fairly strongly disagree with her

00:29:44.580 | about sometimes the way she'll refer to math,

00:29:47.180 | and so the problem is, you know,

00:29:50.340 | physicists and people in general just refer to it as math,

00:29:52.580 | and they're often, they're often meaning

00:29:56.140 | not what I would call math,

00:29:57.220 | which is the interesting ideas of math,

00:29:59.160 | but just some complicated calculation,

00:30:02.580 | and so I guess my feeling about it is more that it's very,

00:30:07.580 | the problem with talking about simplicity

00:30:11.140 | and using simplicity as a guide is that it's very,

00:30:14.720 | it's very easy to fool yourself,

00:30:17.620 | and it's very easy to decide to fall in love with an idea,

00:30:22.620 | you have an idea, you think, oh, this is great,

00:30:26.020 | and you fall in love with it,

00:30:26.940 | and it's like any kind of love affair,

00:30:29.500 | it's very easy to believe that you're,

00:30:31.540 | the object of your affections is much more beautiful

00:30:33.700 | than the others might think, and that they really are,

00:30:36.660 | and that's very, very easy to do,

00:30:39.380 | so if you say I'm just gonna pursue ideas about beauty

00:30:43.980 | and this, and mathematics and this,

00:30:46.460 | it's extremely easy to just fool yourself, I think,

00:30:49.500 | and I think that's a lot of what,

00:30:52.380 | the story she was thinking of

00:30:54.940 | about where people have gone astray,

00:30:56.260 | that I think it's, I would argue that it's more people,

00:30:59.100 | it's not that there was some simple, powerful,

00:31:01.980 | wonderful idea which they'd found,

00:31:03.660 | and it turned out not to be,

00:31:05.400 | not to be useful, but it was more

00:31:08.900 | that they kind of fooled themselves

00:31:10.340 | that this was actually a better idea than it really was,

00:31:13.060 | and that it was simpler and more beautiful

00:31:15.180 | than it really was, is a lot of the story.

00:31:17.700 | - I see, so it's not that the simplicity

00:31:20.300 | would be, leads us astray, is it just people,

00:31:22.380 | are people and they fall in love

00:31:25.100 | with whatever idea they have,

00:31:27.180 | and then they weave narratives around that idea,

00:31:30.220 | or they present it in such a way

00:31:31.500 | that emphasizes the simplicity and the beauty?

00:31:36.500 | - Yeah, that's part of it,

00:31:37.920 | but the thing about physics that you have

00:31:39.980 | is that you, what really can tell,

00:31:44.140 | if you can do an experiment and check

00:31:46.100 | and see if nature is really doing what your idea expects,

00:31:50.820 | then you do in principle have a way of really testing it,

00:31:54.020 | and it's certainly true that if you,

00:31:57.140 | you know, if you thought you had a simple idea

00:31:59.300 | and that doesn't work and you got into an experiment

00:32:01.900 | and what actually does work is some more,

00:32:04.120 | maybe some more complicated version of it,

00:32:05.900 | that can certainly happen, and that can be true.

00:32:10.780 | I think her emphasis is more,

00:32:13.140 | that I don't really disagree with,

00:32:14.580 | is that people should be concentrating on,

00:32:19.380 | when they're trying to develop better theories,

00:32:21.980 | on more on self-consistency, not so much on beauty,

00:32:25.740 | but, you know, not is this idea beautiful,

00:32:28.300 | but is there something about the theory

00:32:30.380 | which is not quite consistent,

00:32:32.460 | and use that as a guide,

00:32:35.340 | that there's something wrong there which needs fixing.

00:32:37.980 | And so I think that part of her argument,

00:32:40.700 | I think I was, we're on the same page about.

00:32:43.380 | - What is consistency and inconsistencies?

00:32:47.460 | What exactly, do you have examples in mind?

00:32:52.460 | - Well, it can be just simple inconsistency

00:32:55.660 | between theory and experiment,

00:32:57.820 | that if you, so we have this great fundamental theory,

00:33:00.960 | but there are some things that we see out there

00:33:02.940 | which don't seem to fit in it,

00:33:04.180 | like dark energy and dark matter, for instance.

00:33:07.460 | But if there's something

00:33:08.280 | which you can't test experimentally,

00:33:09.560 | I think she would argue, and I would agree,

00:33:12.000 | that for instance, if you're trying to think about gravity

00:33:15.100 | and how are you gonna have a quantum theory of gravity,

00:33:17.380 | you should kind of be, you know,

00:33:19.940 | test any of your ideas with kind of a thought experiment.

00:33:24.580 | Is, does this actually give a consistent picture

00:33:26.780 | of what's gonna happen,

00:33:27.940 | of what happens in this particular situation or not?

00:33:31.080 | - So this is a good example, you've written about this.

00:33:35.060 | You know, since quantum gravitational effects

00:33:38.340 | are really small, super small, arguably unobservably small,

00:33:43.340 | should we have hope to arrive

00:33:46.480 | at a theory of quantum gravity somehow?

00:33:49.580 | What are the different ways we can get there?

00:33:51.540 | You've mentioned that you're not as interested

00:33:53.340 | in that effort because basically, yes,

00:33:56.940 | you cannot have ways to scientifically validate

00:34:01.940 | given the tools of today.

00:34:04.160 | - Yeah, I've actually, you know,

00:34:05.580 | I've over the years certainly spent a lot of time

00:34:07.340 | learning about gravity and about attempts to quantize it,

00:34:10.300 | but it hasn't been that much in the past

00:34:13.580 | the focus of what I've been thinking about.

00:34:16.020 | But I mean, my feeling was always, you know,

00:34:18.740 | as I think Spina would agree,

00:34:21.260 | that the, you know, one way you can pursue this

00:34:24.140 | if you can't do experiments is just

00:34:27.380 | this kind of search for consistency.

00:34:29.100 | You know, it can be remarkably hard

00:34:31.260 | to come up with a completely consistent model of this

00:34:34.980 | and a way that brings together quantum mechanics

00:34:37.420 | and general relativity.

00:34:39.540 | And that's, I think, kind of been the traditional way

00:34:42.700 | that people who have pursued quantum gravity

00:34:44.440 | have often pursued, you know,

00:34:48.020 | we have the best route to finding a consistent

00:34:52.180 | theory of quantum gravity.

00:34:53.260 | And string theorists will tell you this,

00:34:55.780 | other people will tell you that it's,

00:34:58.060 | it's kind of what people argue about.

00:35:00.300 | But the problem with all of that is that you end up,

00:35:03.340 | the danger is that you end up with,

00:35:07.180 | that everybody could be successful.

00:35:10.100 | Everybody's program for how to find

00:35:14.180 | a theory of quantum gravity, you know,

00:35:15.540 | ends up with something that is consistent.

00:35:18.500 | And so, and in some sense, you could argue

00:35:20.740 | this is what happened to the string theorists.

00:35:22.420 | They solved their problem of finding

00:35:25.380 | a consistent theory of quantum gravity,

00:35:27.020 | and they ended up, but they found 10 of the 500 solutions.

00:35:30.260 | So you, you know, if you believe that everything

00:35:34.620 | that they would like to be true is true,

00:35:35.940 | well, okay, you've got a theory,

00:35:38.340 | but it ends up being kind of useless

00:35:41.080 | because it's just one of an infinite,

00:35:43.820 | essentially infinite number of things

00:35:46.020 | which you have no way to experimentally distinguish.

00:35:48.300 | And so this is just a depressing situation.

00:35:51.280 | But I do think that there is a,

00:35:55.060 | so again, I think pursuing ideas about what,

00:35:57.740 | more about beauty and how can you integrate

00:36:01.340 | and unify these issues about gravity

00:36:04.300 | with other things we know about physics.

00:36:06.000 | And can you find a theory which,

00:36:07.380 | where these fit together in a way that makes sense

00:36:10.440 | and hopefully predicts something

00:36:12.300 | that's much more promising.

00:36:13.980 | - Well, it makes sense and hopefully,

00:36:15.580 | I mean, we'll sneak up onto this question a bunch of times

00:36:19.580 | 'cause you kind of said a few slightly

00:36:22.460 | contradictory things, which is like,

00:36:24.380 | it's nice to have a theory that's consistent,

00:36:27.180 | but then if the theory is consistent,

00:36:29.940 | it doesn't necessarily mean anything.

00:36:31.740 | (laughs)

00:36:32.820 | So like--

00:36:33.660 | - It's not enough, it's not enough.

00:36:35.180 | - It's not enough, and that's the problem.

00:36:36.760 | So it's like it keeps coming back to,

00:36:39.420 | okay, there should be some experimental validation.

00:36:42.020 | So, okay, let's talk a little bit about string theory.

00:36:46.980 | You've been a bit of an outspoken critic of string theory.

00:36:51.280 | Maybe one question first to ask is what is string theory?

00:36:56.660 | And beyond that, why is it wrong,

00:37:01.660 | or rather, as the title of your blog says,

00:37:04.500 | not even wrong?

00:37:06.500 | - Okay.

00:37:07.840 | Well, one interesting thing about the current state

00:37:09.500 | of string theory is that I think it,

00:37:11.220 | I'd argue it's actually very, very difficult to,

00:37:13.860 | at this point, to say what string theory means.

00:37:15.860 | If people say they're string theorists,

00:37:17.340 | what they mean and what they're doing is,

00:37:20.120 | it's kind of hard,

00:37:22.100 | it's hard to pin down the meaning of the term.

00:37:24.100 | But the initial meaning, I think, goes back to,

00:37:26.780 | there was kind of a series of developments

00:37:30.660 | starting in 1984 in which people felt that they

00:37:34.380 | had found a unified theory of our so-called standard model

00:37:39.380 | of all the standard, well-known kind of

00:37:42.440 | particle interactions and gravity,

00:37:44.580 | and it all fit together in a quantum theory,

00:37:46.680 | and that you could do this in a very specific way

00:37:49.920 | by, instead of thinking about having a quantum theory

00:37:54.880 | of particles moving around in space-time,

00:37:57.160 | think about a quantum theory of kind of one-dimensional

00:38:00.360 | loops moving around in space-time, so-called strings.

00:38:03.400 | And so, instead of one degree of freedom,

00:38:06.540 | these have an infinite number of degrees of freedom,

00:38:08.180 | it's a much more complicated theory.

00:38:09.940 | But you can imagine,

00:38:11.020 | okay, we're gonna quantize this theory of

00:38:14.380 | loops moving around in space-time,

00:38:16.740 | and what they found is that they,

00:38:19.300 | is that you could make, you could do this,

00:38:21.140 | and you could fairly, relatively straightforwardly

00:38:23.380 | make sense of such a quantum theory,

00:38:26.860 | but only if space and time together were 10-dimensional.

00:38:30.620 | And so then you had this problem,

00:38:32.940 | again, the problem I referred to at the beginning of,

00:38:34.800 | okay, now, once you make that move,

00:38:37.240 | you gotta get rid of six dimensions.

00:38:39.600 | And so the hope was that you could get rid of

00:38:42.320 | the six dimensions by making them very small,

00:38:44.800 | and that consistency of the theory would require

00:38:47.440 | that these six dimensions satisfy a very specific condition

00:38:52.840 | called being a Calabi-Yau manifold,

00:38:55.160 | and that we knew very, very few examples of this.

00:38:58.280 | So what got a lot of people very excited back in 84, 85,

00:39:02.280 | was the hope that you could just take this

00:39:05.720 | 10-dimensional string theory and

00:39:07.560 | find one of a limited number of possible ways

00:39:10.880 | of getting rid of six dimensions by making them small,

00:39:14.580 | and then you would end up with

00:39:16.080 | an effective four-dimensional theory

00:39:17.560 | which looked like the real world.

00:39:18.760 | This was the hope.

00:39:20.000 | So then, there's a very long story about

00:39:22.720 | what happened to that hope over the years.

00:39:24.860 | I mean, I would argue, and part of the point of the book

00:39:28.740 | and its title was that this ultimately was a failure

00:39:33.740 | that you ended up, that this idea just didn't,

00:39:36.440 | there ended up being just too many ways of doing this,

00:39:41.020 | and you didn't know how to do this consistently,

00:39:44.060 | that it was kind of not even wrong in the sense that

00:39:46.820 | you never could pin it down well enough

00:39:49.580 | to actually get a real falsifiable prediction out of it

00:39:53.920 | that would tell you it was wrong,

00:39:55.180 | but it was kind of in the realm of ideas

00:39:59.300 | which initially looked good,

00:40:00.380 | but the more you look at them,

00:40:02.080 | they just don't work out the way you want,

00:40:05.420 | and they don't actually end up carrying the power

00:40:07.740 | or that you originally had this vision of.

00:40:10.180 | - And yes, the book title is not even wrong.

00:40:14.180 | Your blog, your excellent blog title is not even wrong.

00:40:17.760 | Okay, but there's nevertheless been a lot of excitement

00:40:20.860 | about string theory through the decades, as you mentioned.

00:40:24.140 | What are the different flavors of ideas that came,

00:40:27.820 | like that branched out?

00:40:31.300 | You mentioned 10 dimensions,

00:40:32.660 | you mentioned loops with infinite degrees of freedom.

00:40:36.500 | What are the interesting ideas to you

00:40:38.740 | that kind of emerged from this world?

00:40:41.020 | - Well, yeah, I mean, the problem in talking about

00:40:42.560 | the whole subject, and part of the reason I wrote the book

00:40:45.740 | is that it gets very, very complicated.

00:40:48.740 | I mean, there's a huge amount,

00:40:52.100 | a lot of people got very interested in this,

00:40:54.460 | a lot of people worked on it,

00:40:55.740 | and in some sense, I think what happened is

00:40:58.380 | exactly because the idea didn't really work,

00:41:01.340 | that this caused people to,

00:41:03.560 | instead of focusing on this one idea

00:41:06.180 | and digging in and working on that,

00:41:08.220 | they just kind of kept trying new things.

00:41:11.060 | And so people, I think, ended up wandering around

00:41:14.040 | in a very, very rich space of ideas

00:41:15.900 | about mathematics and physics

00:41:17.700 | and discovering all sorts of really interesting things.

00:41:20.000 | It's just, the problem is there tended to be

00:41:22.220 | an inverse relationship between how interesting

00:41:24.860 | and beautiful and fruitful this new idea

00:41:27.540 | that they were trying to pursue was

00:41:28.860 | and how much it looked like the real world.

00:41:31.860 | So there's a lot of beautiful mathematics came out of it.

00:41:34.540 | I think one of the most spectacular

00:41:36.060 | is what the physicists call

00:41:38.380 | two-dimensional conformal field theory.

00:41:40.660 | And so these are basically quantum field theories

00:41:44.660 | and kind of think of it as one space and one time dimension,

00:41:47.800 | which have just this huge amount of symmetry

00:41:51.240 | and a huge amount of structure,

00:41:53.660 | which just some totally fantastic mathematics behind it.

00:41:58.060 | And again, and some of that mathematics

00:42:00.380 | is exactly also what appears in the Langlands program.

00:42:03.280 | So a lot of the first interaction between math and physics

00:42:07.760 | around the Langlands program

00:42:08.860 | has been around these two-dimensional

00:42:10.340 | conformal field theories.

00:42:11.580 | - Is there something you could say

00:42:15.220 | about what are the major problems are

00:42:17.180 | with string theory?

00:42:18.980 | So like,

00:42:20.240 | besides that there's no experimental validation,

00:42:25.800 | you've written that a big hole in string theory

00:42:30.400 | has been its perturbative definition.

00:42:33.600 | - Yeah.

00:42:34.480 | - Perhaps that's one.

00:42:35.340 | Can you explain what that means?

00:42:36.920 | - Well, maybe to begin with,

00:42:38.040 | I think the simplest thing to say is,

00:42:40.740 | the initial idea really was that,

00:42:45.200 | okay, we have this,

00:42:47.000 | instead of what's great is we have this thing

00:42:49.040 | that only works,

00:42:50.720 | that's very structured and has to work in a certain way

00:42:54.160 | for it to make sense.

00:42:55.540 | But then you ended up in 10 space-time dimensions.

00:43:01.700 | And so to get back to physics,

00:43:03.620 | you had to get rid of five of the dimensions,

00:43:05.380 | six of the dimensions.

00:43:06.880 | And the bottom line, I would say,

00:43:08.600 | in some sense, is very simple.

00:43:09.600 | That what people just discovered is just,

00:43:12.800 | there's kind of no particularly nice way of doing this.

00:43:15.640 | There's an infinite number of ways of doing it

00:43:17.480 | and you can get whatever you want

00:43:18.720 | depending on how you do it.

00:43:20.160 | So you end up,

00:43:21.840 | the whole program of starting at 10 dimensions

00:43:24.040 | and getting to four,

00:43:25.520 | just kind of collapses out of a lack of any way

00:43:28.560 | to kind of get to where you want

00:43:29.760 | 'cause you can get anything.

00:43:31.560 | The hope around that problem has always been that

00:43:34.720 | the standard formulation that we have of string theory,

00:43:38.960 | which is, you can go in by the name perturbative,

00:43:42.560 | but it's kind of,

00:43:43.580 | there's a standard way we know

00:43:46.320 | of given a classical theory of constructing

00:43:48.960 | a quantum theory and working with it,

00:43:52.880 | which is the so-called perturbation theory.

00:43:56.960 | That we know how to do.

00:43:59.240 | And that by itself just doesn't give you any hint

00:44:04.240 | as to what to do about the six dimensions.

00:44:06.660 | So actual perturbed string theory by itself

00:44:09.200 | really only works in 10 dimensions.

00:44:11.340 | So you have to start making some kinds of assumptions

00:44:14.360 | about how I'm gonna go beyond

00:44:17.360 | this formulation that we really understand

00:44:20.960 | of string theory and get rid of these six dimensions.

00:44:24.040 | So kind of the simplest one was the Clavier-Postulate.

00:44:29.040 | But when that didn't really work out,

00:44:31.820 | people have tried more and more different things.

00:44:33.920 | And the hope has always been that

00:44:35.720 | the solution to this problem would be

00:44:39.520 | that you would find a deeper and better understanding

00:44:42.640 | of what string theory is

00:44:44.220 | that would actually go beyond this perturbative expansion

00:44:47.880 | and which would generalize this.

00:44:51.820 | And that once you had that,

00:44:53.220 | it would solve this problem of,

00:44:57.220 | it would pick out what to do with the six dimensions.

00:44:59.600 | - How difficult is this problem?

00:45:01.140 | So if I could restate the problem,

00:45:05.100 | it seems like there's a very consistent physical world

00:45:09.860 | operating in four dimensions.

00:45:11.740 | And how do you map a consistent physical world

00:45:16.700 | in 10 dimensions to a consistent physical world

00:45:19.240 | in four dimensions?

00:45:21.180 | And how difficult is this problem?

00:45:23.100 | Is that something you can even answer?

00:45:25.320 | Just in terms of physics intuition,

00:45:30.340 | in terms of mathematics,

00:45:32.260 | mapping from 10 dimensions to four dimensions.

00:45:35.100 | - Well, basically, I mean, you have to get rid

00:45:36.580 | of the six of the dimensions.

00:45:38.260 | So there's kind of two ways of doing it.

00:45:41.620 | One is what we call compactification.

00:45:44.020 | You say that there really are 10 dimensions,

00:45:46.880 | but for whatever reason,

00:45:48.240 | six of them are really are so, so small, we can't see them.

00:45:51.900 | So you basically start out with 10 dimensions

00:45:54.680 | and what we call, make six of them not go out to infinity,

00:45:59.020 | but just kind of a finite extent

00:46:00.820 | and then make that size go down.

00:46:02.520 | So small, it's unobservable.

00:46:05.500 | - But that's like, that's a math trick.

00:46:08.340 | So can you also help me build an intuition

00:46:11.460 | about how rich and interesting the world

00:46:15.580 | in those six dimensions is?

00:46:17.860 | So compactification seems to imply

00:46:20.100 | that it's not very interesting.

00:46:22.660 | - Well, no, but the problem is that what you learn

00:46:24.700 | if you start doing mathematics

00:46:26.780 | and looking at geometry and topology

00:46:29.620 | and more and more dimensions is that,

00:46:31.620 | I mean, asking the question like,

00:46:34.220 | what are all possible six dimensional spaces?

00:46:36.540 | It's just, it's kind of an unanswerable question.

00:46:38.580 | It's just, I mean,

00:46:39.620 | it's even kind of technically undecidable in some way.

00:46:42.020 | There are too many things you can do with all these.

00:46:46.180 | If you start trying to make one dimensional spaces,

00:46:49.540 | it's like, well, you got a line, you can make a circle,

00:46:52.140 | you can make graphs, you can kind of see what you can do.

00:46:55.180 | But as you go to higher and higher dimensions,

00:46:58.260 | there are just so many ways you can put things together

00:47:02.140 | and get something of that dimensionality.

00:47:05.460 | And so unless you have some very, very strong principle,

00:47:09.820 | we're just gonna pick out some very specific ones

00:47:12.900 | of these six dimensional spaces.

00:47:15.400 | And there are just too many of them

00:47:17.340 | and you can get anything you want.

00:47:19.500 | - So if you have 10 dimensions,

00:47:21.620 | the kind of things that happen,

00:47:24.420 | say that's actually the way,

00:47:26.700 | that's actually the fabric of our reality is 10 dimensions.

00:47:29.740 | There's a limited set of behaviors of objects,

00:47:33.100 | I don't even know what the right terminology to use

00:47:36.060 | that can occur within those dimensions, like in reality.

00:47:40.620 | And so what I'm getting at is like,

00:47:44.500 | is there some consistent constraints?

00:47:47.260 | So if you have some constraints that map to reality,

00:47:51.060 | then you can start saying like,

00:47:53.460 | dimension number seven is kind of boring.

00:47:56.260 | All the excitement happens in the spatial dimensions,

00:47:58.900 | one, two, three.

00:48:00.380 | And time is also kind of boring.

00:48:02.220 | Some are more exciting than others,

00:48:05.380 | or we can use our metric of beauty.

00:48:08.100 | Some dimensions are more beautiful than others.

00:48:10.260 | Once you have an actual understanding

00:48:12.240 | of what actually happens in those dimensions

00:48:15.260 | in our physical world,

00:48:16.500 | as opposed to sort of all the possible things

00:48:18.620 | that could happen.

00:48:19.580 | - In some sense, I mean, just the basic fact

00:48:21.460 | is you need to get rid of them, we don't see them.

00:48:22.980 | So you need to somehow explain them.

00:48:25.580 | The main thing you're trying to do

00:48:26.580 | is to explain why we're not seeing them.

00:48:28.820 | And so you have to come up with some theory

00:48:32.540 | of these extra dimensions and how they're gonna behave.

00:48:35.420 | And string theory gives you some ideas about how to do that.

00:48:38.980 | But the bottom line is where you're trying to go

00:48:43.580 | with this whole theory you're creating

00:48:45.660 | is to just make all of its effects essentially unobservable.

00:48:49.540 | So it's not a really,

00:48:54.780 | it's an inherently kind of dubious and worrisome thing

00:48:57.300 | that you're trying to do there.

00:48:58.300 | Why are you just adding in all this stuff

00:49:00.580 | and then trying to explain why we don't see it?

00:49:02.220 | I mean, it just--

00:49:03.060 | - This may be a dumb question,

00:49:04.220 | but is this an obvious thing to state

00:49:07.740 | that those six dimensions are unobservable

00:49:11.540 | or anything beyond four dimensions is unobservable?

00:49:14.680 | Or do you leave a little door open to saying

00:49:20.900 | the current tools of physics,

00:49:23.140 | and obviously our brains are unable to observe them,

00:49:26.940 | but we may need to come up with methodologies

00:49:29.900 | for observing them.

00:49:30.740 | So as opposed to collapsing your mathematical theory

00:49:33.100 | into four dimensions,

00:49:34.980 | leaving the door open a little bit to

00:49:37.100 | maybe we need to come up with tools

00:49:38.720 | that actually allow us to directly measure those dimensions.

00:49:42.660 | - Yes, I mean, you can certainly ask,

00:49:45.180 | assume that we've got model,

00:49:48.940 | look at models with more dimensions

00:49:50.700 | and ask what would be observable effects?

00:49:52.620 | How would we know this?

00:49:54.140 | And you go out and do experiments.

00:49:55.460 | So for instance, you have a,

00:49:58.740 | like gravitationally you have an inverse square law forces.

00:50:02.460 | Okay, if you had more dimensions,

00:50:04.060 | that inverse square law would change to something else.

00:50:06.580 | So you can go and start measuring the inverse square law

00:50:09.500 | and say, okay, inverse square law is working,

00:50:12.020 | but maybe if I get,

00:50:14.620 | and it turns out to be actually kind of very, very hard

00:50:16.500 | to measure gravitational effects

00:50:18.100 | at even kind of somewhat macroscopic distances

00:50:21.900 | because they're so small.

00:50:23.260 | So you can start looking at the inverse square law

00:50:26.220 | and say, start trying to measure it

00:50:27.980 | at shorter and shorter distances

00:50:29.340 | and see if there were extra dimensions

00:50:33.140 | at those distance scales,

00:50:34.420 | you would start to see the inverse square law fail.

00:50:36.740 | And so people look for that.

00:50:38.620 | And again, you don't see it,

00:50:40.500 | but you can, I mean,

00:50:42.100 | there's all sorts of experiments of this kind.

00:50:43.580 | You can imagine which test for effects of extra dimensions

00:50:48.380 | at different distance scales,

00:50:50.740 | but none of them, I mean, they all just don't work.

00:50:55.740 | - Nothing yet.

00:50:58.100 | - Nothing yet, but you can say,

00:50:59.180 | ah, but it's just much, much smaller.

00:51:02.860 | You can say that.

00:51:03.700 | - Which by the way, makes LIGO

00:51:06.860 | and the detection of gravitational waves

00:51:09.940 | quite an incredible project.

00:51:11.620 | Ed Witten is often brought up

00:51:15.660 | as one of the most brilliant mathematicians

00:51:17.380 | and physicists ever.

00:51:19.980 | What do you make of him and his work on string theory?

00:51:24.420 | - Well, I think he's a truly remarkable figure.

00:51:26.780 | I've had the pleasure of meeting him first

00:51:30.100 | when he was a postdoc.

00:51:31.060 | And I mean, he's just completely amazing

00:51:34.740 | mathematician and physicist.

00:51:37.980 | And he's quite a bit smarter

00:51:41.420 | than just about any of the rest of us

00:51:43.340 | and also more hardworking.

00:51:44.540 | And it's a kind of frightening combination

00:51:46.740 | to see how much he's been able to do.

00:51:49.140 | But I would actually argue that his greatest work,

00:51:53.500 | the things that he's done that have been of

00:51:55.780 | just this mind blowing significance of giving us,

00:51:58.620 | I mean, he's completely revolutionized

00:52:00.060 | some areas of mathematics.

00:52:02.140 | He's totally revolutionized the way we understand

00:52:04.180 | the relations between mathematics and physics.

00:52:07.140 | And most of those, his greatest work

00:52:10.660 | is stuff that has little or nothing

00:52:13.660 | to do with string theory.

00:52:15.100 | I mean, for instance, he,

00:52:16.620 | so he was actually one of fields.

00:52:19.140 | The very strange thing about him in some sense

00:52:20.860 | is that he doesn't have a Nobel prize.

00:52:23.620 | So there's a very large number of people

00:52:25.860 | who are nowhere near as smart as he is

00:52:28.220 | and don't work anywhere near as hard

00:52:30.100 | who have Nobel prizes.

00:52:31.700 | I think he just had the misfortune of

00:52:33.900 | coming into the field at a time

00:52:35.780 | when things had gotten much, much, much tougher

00:52:37.700 | and nobody really had, no matter how smart you were,

00:52:41.380 | it was very hard to come up with a new idea

00:52:43.980 | that was gonna work physically and get you a Nobel prize.

00:52:47.700 | But he got a Fields Medal for

00:52:51.220 | a certain work he did in mathematics.

00:52:54.580 | And that's just completely unheard of

00:52:56.500 | for mathematicians to give a Fields Medal

00:52:58.340 | to someone outside their field.

00:52:59.860 | And physics is really,

00:53:01.620 | you wouldn't have before he came around.

00:53:05.580 | I don't think anybody would have thought

00:53:06.660 | that was even conceivable.

00:53:07.980 | - So you're saying he came into the field

00:53:10.980 | of theoretical physics at a time

00:53:13.180 | when, and still to today,

00:53:16.820 | is you can't get a Nobel prize for purely theoretical work.

00:53:20.180 | - The specific problem of trying to do better

00:53:22.300 | than the standard model is just

00:53:24.860 | this insanely successful thing.

00:53:26.620 | And it kind of came together in 1973, pretty much.

00:53:30.580 | And all of the people who kind of were involved

00:53:34.300 | in that coming together,

00:53:36.300 | many of them ended up with Nobel prizes for that.

00:53:39.140 | But if you look post 1973, pretty much,

00:53:43.580 | it's a little bit more,

00:53:44.860 | there's some edge cases, if you like.

00:53:47.580 | But if you look post 1973 at what people have done

00:53:51.860 | to try to do better than the standard model

00:53:54.460 | and to get a better, you know, idea,

00:53:56.140 | it really hasn't, it's been too hard a problem.

00:53:58.420 | It hasn't worked, the theory's too good.

00:53:59.940 | And so it's not that other people went out there

00:54:03.300 | and did it and not him,

00:54:06.220 | and that they got Nobel prizes for doing it.

00:54:07.780 | It's just that no one really,

00:54:08.980 | the kind of thing he's been trying to do

00:54:10.500 | with string theory is not,

00:54:12.300 | no one has been able to do since 1973.

00:54:14.740 | - Is there something you could say about the standard model?

00:54:17.420 | So the four laws of physics that seems to work very well,

00:54:20.740 | and yet people are striving to do more,

00:54:25.020 | talking about unification and so on, why?

00:54:27.620 | What's wrong, what's broken about the standard model?

00:54:30.940 | Why does it need to be improved?

00:54:33.140 | - I mean, the thing that gets most attention

00:54:34.940 | is gravity that we have trouble.

00:54:38.240 | So you wanna, in some sense,

00:54:40.820 | integrate what we know about the gravitational force

00:54:45.740 | with it and have a unified quantum field theory

00:54:48.700 | that has gravitational interactions also.

00:54:50.380 | So that's the big problem everybody talks about.

00:54:52.780 | I mean, but it's also true

00:54:55.340 | that if you look at the standard model,

00:54:57.060 | it has these very, very deep, beautiful ideas,

00:54:59.260 | but there's certain aspects of it that are very,

00:55:03.720 | let's just say that they're not beautiful.

00:55:08.240 | They're not, you have to, to make the thing work,

00:55:11.440 | you have to throw in lots and lots of extra parameters

00:55:14.240 | at various points.

00:55:15.360 | And a lot of this has to do with the so-called,

00:55:18.540 | the so-called Higgs mechanism and the Higgs field.

00:55:21.960 | That if you look at the theory, it's everything is,

00:55:25.960 | if you forget about the Higgs field and what it needs to do,

00:55:28.960 | the rest of the theory is very, very constrained

00:55:33.520 | and has very, very few free parameters,

00:55:35.320 | really a very small number.

00:55:36.400 | There's a very small number of parameters

00:55:38.040 | and a few integers which tell you what the theory is.

00:55:40.900 | To make this work as a theory of the real world,

00:55:42.940 | you need a Higgs field and you need to,

00:55:45.480 | it needs to do something.

00:55:48.080 | And once you introduce that Higgs field,

00:55:50.840 | all sorts of parameters make an appearance.

00:55:54.440 | So now when we've got 20 or 30 or whatever parameters

00:55:58.760 | that are gonna tell you what all the masses of things are

00:56:00.880 | and what's gonna happen.

00:56:02.160 | So you've gone from a very tightly constrained thing

00:56:05.520 | with a couple of parameters to this thing,

00:56:09.000 | which the minute you put it in,

00:56:11.120 | you had to add all this extra,

00:56:13.220 | all these extra parameters to make things work.

00:56:15.320 | And so that, it may be one argument as well,

00:56:19.120 | that's just the way the world is.

00:56:20.480 | And the fact that you don't find that aesthetically pleasing

00:56:24.160 | is just your problem.

00:56:25.200 | Or maybe we live in a multiverse

00:56:27.320 | and those numbers are just different in every universe.

00:56:30.080 | But another reasonable conjecture is just that,

00:56:33.600 | well, this is just telling us

00:56:35.420 | that there's something we don't understand

00:56:36.940 | about what's going on in a deeper way,

00:56:40.200 | which would explain those numbers.

00:56:41.680 | And there's some kind of deeper idea

00:56:44.240 | about where the Higgs field comes from and what's going on,

00:56:47.240 | which we haven't figured out yet.

00:56:49.040 | And that's what we should look for.

00:56:52.840 | - But to stick on string theory a little bit longer,

00:56:55.960 | could you play devil's advocate

00:56:57.520 | and try to argue for string theory,

00:57:01.880 | why it is something that deserved the effort that it got

00:57:06.880 | and still, like if you think of it as a flame,

00:57:10.420 | still should be a little flame that keeps burning?

00:57:14.160 | - Well, I think the, I mean,

00:57:16.240 | the most positive argument for it is all the,

00:57:18.820 | all sorts of new ideas about mathematics

00:57:22.120 | and about parts of physics really emerged from it.

00:57:24.800 | So it was very a fruitful source of ideas.

00:57:28.440 | And I think this is actually one argument you'll definitely,

00:57:30.760 | which I kind of agree with,

00:57:31.640 | I'll hear from Witten and from other string theorists

00:57:34.360 | say that this is just such a fruitful and inspiring idea.

00:57:39.000 | And it's led to so many other different things

00:57:41.360 | coming out of it that there must be something

00:57:43.720 | right about this.

00:57:45.200 | And that's, okay, that, anyway,

00:57:47.920 | I think that that's probably the strongest thing

00:57:50.240 | that they've got.

00:57:52.800 | But you don't think there's aspects to it

00:57:55.840 | that could be neighboring to a theory

00:58:00.480 | that does unify everything, to a theory of everything.

00:58:03.200 | Like it could, it may not be exactly,

00:58:05.760 | exactly the theory, but sticking on it longer

00:58:11.280 | might get us closer to the theory of everything.

00:58:14.400 | - Well, the problem with it now really

00:58:15.440 | is that you really don't know what it is now.

00:58:17.320 | You've never, nobody has ever kind of come up

00:58:19.920 | with this non-perturbative theory.

00:58:23.400 | So it's become more and more frustrating

00:58:27.440 | and an odd activity to try to argue

00:58:29.480 | with a string theorist about string theory,

00:58:32.200 | because it's become less and less well-defined what it is.

00:58:37.200 | And it's become actually more and more kind of a,

00:58:40.100 | whether you have this weird phenomenon

00:58:42.320 | of people calling themselves string theorists

00:58:44.800 | when they've never actually worked on any theory

00:58:47.520 | where there are any strings anywhere.

00:58:49.560 | So what has actually happened kind of sociologically

00:58:52.600 | is that you started out with this fairly

00:58:55.080 | well-defined proposal, and then I would argue

00:58:58.400 | because that didn't work, people then branched out

00:59:00.700 | in all sorts of directions doing all sorts of things

00:59:02.840 | that became farther and farther removed from that.

00:59:05.560 | And for sociological reasons, the ones who kind of

00:59:09.360 | started out or now, or were trained by the people

00:59:14.280 | who worked on that have now become the string theorists.

00:59:18.920 | And, but it's become almost more kind of a tribal denominator

00:59:23.920 | than a, so it's very hard to know what you're arguing about

00:59:29.040 | when you're arguing about string theory these days.

00:59:30.680 | - Well, to push back on that a little bit,

00:59:32.120 | I mean, string theory, it's just a term, right?

00:59:34.560 | It doesn't, like you could, like this is the way

00:59:37.720 | language evolves, is it could start to represent

00:59:41.020 | something more than just the theory that involves strings.

00:59:43.440 | It could represent the effort to unify the laws of physics.

00:59:49.160 | Right? - Yeah.

00:59:50.000 | - At high dimensions with these super tiny objects, right?

00:59:54.680 | Or something like that.

00:59:56.120 | I mean, we can sort of put string theory aside.

00:59:59.320 | So for example, neural networks in the space

01:00:01.400 | of machine learning, there was a time when they were

01:00:04.480 | extremely popular, they became much, much less popular

01:00:07.180 | to a point where if you mention neural networks

01:00:08.960 | to gain no funding, and you're not going to be respected

01:00:12.600 | at conferences, and then once again, neural networks

01:00:16.080 | became all the rage about 10, 15 years ago.

01:00:20.720 | And as it goes up and down, and a lot of people

01:00:23.040 | would argue that using terminology like machine learning

01:00:26.660 | and deep learning is often misused over general.

01:00:31.660 | Everything that works is deep learning,

01:00:35.160 | everything that doesn't isn't.

01:00:36.960 | - Yeah. - Something like that.

01:00:38.240 | That's just the way, again, we're back

01:00:40.800 | to sociological things. - Yeah.

01:00:42.920 | - But I guess what I'm trying to get at is

01:00:45.280 | if we leave the sociological mess aside,

01:00:48.600 | do we throw out the baby with the bathwater?

01:00:53.120 | Is there some, besides the side effects of nice ideas

01:00:57.120 | from the Edwittons of the world,

01:00:59.160 | is there some core truths there that we should stick by

01:01:04.160 | in the full, beautiful mess of a space

01:01:08.200 | that we call string theory, that people call string theory?

01:01:11.400 | - You're right, it is kind of a common problem

01:01:14.320 | that how what you call some field changes and evolves

01:01:19.320 | in interesting ways as the field changes.

01:01:22.720 | But I mean, I guess what I would argue

01:01:27.720 | is the initial understanding of string theory

01:01:30.440 | that was quite specific, we're talking about a specific idea,

01:01:33.160 | 10-dimensional superstrings compactified in six dimensions.

01:01:36.460 | To my mind, the really bad thing that's happened

01:01:41.240 | to the subject is that it's hard to get people to admit,

01:01:45.800 | at least publicly, that that was a failure,

01:01:48.120 | that this really didn't work.

01:01:49.760 | And so de facto, what people do is people stop doing that

01:01:53.240 | and they start doing more interesting things,

01:01:55.400 | but they keep talking to the public about string theory

01:02:00.400 | and referring back to that idea and using that

01:02:04.040 | as kind of the starting point and as kind of the place

01:02:07.840 | where the whole tribe starts and everything comes from.

01:02:12.840 | So the problem with this is that having as your initial name

01:02:17.960 | and what everything points back to,

01:02:20.480 | something which really didn't work out,

01:02:25.480 | it kind of makes everybody, it makes everything,

01:02:28.280 | you've created this potentially very, very interesting field

01:02:31.040 | with interesting things happening,

01:02:32.080 | but people in graduate school take courses on string theory

01:02:37.760 | and everything kind of, and this is what you tell the public

01:02:40.160 | in which you're continually pointing back.

01:02:41.680 | So you're continually pointing back to this idea

01:02:43.520 | which never worked out as your guiding inspiration.

01:02:48.520 | And it really kind of deforms your whole way

01:02:51.580 | of your hopes of making progress.

01:02:54.100 | And that's, to me, I think the kind of worst thing

01:02:57.360 | that's happened in this field.

01:02:59.200 | - 'Cause sure, so there's a lack of transparency

01:03:01.400 | and sort of authenticity about communicating

01:03:03.680 | the things that failed in the past.

01:03:07.120 | And so you don't have a clear picture of firm ground

01:03:10.920 | that you're standing on.

01:03:12.080 | But again, those are sociological things.

01:03:14.120 | - Yeah.

01:03:14.960 | - There's a bunch of questions I wanna ask you.

01:03:18.720 | So one, what's your intuition about

01:03:22.160 | why the original idea failed?

01:03:26.640 | So what can you say about why you're pretty sure

01:03:30.760 | it has failed?

01:03:31.740 | - And the initial idea was, as I tried to explain it,

01:03:35.360 | it was quite seductive in that you could see why Witten

01:03:39.040 | and others got excited by it.

01:03:40.600 | At the time, it looked like there were only a few

01:03:45.720 | these possible clobby hours that would work.

01:03:47.640 | And it looked like, okay, we just have to understand

01:03:50.000 | this very specific model

01:03:52.240 | and these very specific six dimensional spaces

01:03:54.100 | and we're gonna get everything.

01:03:55.760 | And so it was a very seductive idea.

01:03:57.260 | But it just, as people learned, worked more and more

01:04:02.640 | about it, it just didn't, they just kind of realized

01:04:06.840 | that there are just more and more things you can do

01:04:08.320 | with these six dimensions and you can't,

01:04:10.200 | and this is just not going to work.

01:04:12.760 | - Meaning like it's, I mean, what was the failure

01:04:17.760 | mode here?

01:04:21.280 | Is you could just have an infinite number of possibilities

01:04:24.240 | that you could do so you can come up with any theory

01:04:26.800 | you want, you can fit quantum mechanics,

01:04:28.440 | you can explain gravity, you can explain anything

01:04:31.600 | you want with it.

01:04:32.920 | Is that the basic failure mode?

01:04:34.320 | - Yeah, so it's a failure mode of kind of that this idea

01:04:37.160 | ended up being essentially empty,

01:04:39.960 | that it just didn't, doesn't, ends up not telling you

01:04:42.880 | anything because it's consistent with just about anything.

01:04:47.360 | And so I mean, there's a complex, if you try and talk

01:04:50.800 | with strength areas about this now, I mean,

01:04:52.320 | there's an argument, there's a long argument over this

01:04:54.760 | about whether, you know, oh, no, no, no, maybe there still

01:04:58.840 | are constraints coming out of this idea or not.

01:05:01.320 | And, or maybe we live in a multiverse and, you know,

01:05:05.280 | everything is true anyway.

01:05:06.680 | So you can, there are various ways you can kind of,

01:05:10.280 | that strength areas have kind of react to this kind of

01:05:12.600 | argument that I'm making, try to hold on to it.

01:05:15.580 | - What about experimental validation?

01:05:18.960 | Is that a fair standard to hold before a theory

01:05:23.960 | of everything that's trying to unify quantum mechanics

01:05:28.120 | and gravity?

01:05:29.000 | - Yeah, I mean, ultimately to be really convinced

01:05:31.400 | that, you know, that on some new idea about unification

01:05:36.160 | really works, you need some kind of, you need to look

01:05:39.080 | at the real world and see that this is telling you something,

01:05:42.080 | something true about it.

01:05:44.240 | I mean, you know, either telling you that if you do

01:05:48.980 | some experiment and go out and do it, you'll get some

01:05:51.320 | unexpected result and that's the kind of gold standard,

01:05:54.840 | or it may be just that like all those numbers that are,

01:05:58.840 | we don't know how to explain, it will show you how

01:06:01.000 | to calculate them.

01:06:02.200 | I mean, it can be various kinds of experimental validation,

01:06:05.240 | but that's certainly ideally what you're looking for.

01:06:08.640 | - How tough is this, do you think, for a theory

01:06:10.560 | of everything, not just strength theory?

01:06:12.880 | For something that unifies gravity and quantum mechanics,

01:06:15.000 | so the very big and the very small, is this,

01:06:18.180 | let me ask it one way, is it a physics problem,

01:06:24.240 | a math problem, or an engineering problem?

01:06:27.940 | - My guess is it's a combination of a physics

01:06:30.400 | and a math problem that you really need.

01:06:32.700 | It's not really engineering, it's not like there's some

01:06:36.280 | kind of well-defined thing you can write down

01:06:39.400 | and we just don't have enough computer power

01:06:41.540 | to do the calculation.

01:06:43.240 | That's not the kind of problem it is at all.

01:06:45.440 | But the question is, you know, what mathematical tools

01:06:49.040 | you need to properly formulate the problem is unclear.

01:06:53.440 | So one reasonable conjecture is the way, the reason

01:06:56.400 | that we haven't had any success yet is just that

01:06:59.460 | we're missing, either we're missing certain physical ideas

01:07:04.240 | or we're missing certain mathematical tools,

01:07:06.260 | which are some combination of them, which would,

01:07:08.940 | which we need to kind of properly formulate the problem

01:07:12.720 | and see that it has a solution

01:07:15.720 | that looks like the real world.

01:07:17.240 | - But don't you need, I guess you don't,

01:07:19.340 | but there's a sense that you need both gravity,

01:07:24.560 | like all the laws of physics to be operating

01:07:27.320 | on the same level, so it feels like you need an object

01:07:30.720 | like a black hole or something like that

01:07:32.720 | in order to make predictions about,

01:07:38.080 | otherwise you're always making predictions

01:07:40.320 | about disjoint phenomena.

01:07:42.700 | Or can you do that as long as the theory is consistent

01:07:46.920 | and doesn't have special cases for each of the phenomena?

01:07:48.800 | - Well, your theory should, I mean,

01:07:50.560 | if your theory is gonna include gravity,

01:07:52.120 | our current understanding of gravity is that you should

01:07:54.080 | have, there should be black hole states in it,

01:07:57.840 | you should be able to describe black holes in this theory.

01:08:00.000 | And just one aspect that people concentrate a lot on

01:08:04.280 | is just this kind of questions about if your theory

01:08:08.040 | includes black holes like it's supposed to

01:08:09.840 | and it includes quantum mechanics,

01:08:11.840 | then there's certain kind of paradoxes which come up.

01:08:13.880 | And so that's been a huge focus of kind of

01:08:16.120 | quantum gravity work has been just those paradoxes.

01:08:19.320 | - So stepping outside of string theory,

01:08:23.240 | can you just say first at a high level,

01:08:26.520 | what is the theory of everything?

01:08:28.560 | What does the theory of everything seek to accomplish?

01:08:31.320 | - Well, I mean, this is very much a kind of reductionist

01:08:34.760 | point of view in the sense that, so it's not a theory,

01:08:38.080 | this is not gonna explain to you anything,

01:08:42.280 | it doesn't really, this kind of theory of everything

01:08:45.600 | we're talking about doesn't say anything interesting,

01:08:48.320 | particularly about like macroscopic objects,

01:08:50.240 | about what the weather's gonna be tomorrow

01:08:52.320 | or things are happening at this scale.

01:08:54.800 | But just what we've discovered is that as you look at

01:08:58.360 | the universe, it kind of, if you kind of start,

01:09:04.400 | you can start breaking it apart into,

01:09:06.320 | and you end up with some fairly simple pieces,

01:09:08.440 | quanta if you like, and which are doing,

01:09:11.160 | which are interacting in some fairly simple way.

01:09:14.480 | And it's, so what we mean by the theory of everything

01:09:18.520 | is a theory that describes all the correct objects

01:09:23.520 | you need to describe what's happening in the world

01:09:27.840 | and describes how they're interacting with each other

01:09:30.200 | at a most fundamental level.

01:09:31.920 | How you get from that theory to describing

01:09:35.520 | some macroscopic, incredibly complicated thing

01:09:38.240 | is there that becomes, again, more of an engineering problem

01:09:41.200 | and you may need machine learning

01:09:42.680 | or you may, a lot of very different things to do it.

01:09:45.240 | - Well, I don't even think it's just engineering,

01:09:48.760 | it's also science.

01:09:50.400 | One thing that I find kind of interesting

01:09:55.200 | talking to physicists is a little bit,

01:09:59.240 | there's a little bit of hubris.

01:10:07.200 | So some of the most brilliant people I know are physicists,

01:10:09.760 | both philosophy and just in terms of mathematics,

01:10:12.340 | in terms of understanding the world.

01:10:14.280 | But there's a kind of either a hubris

01:10:16.480 | or what would I call it,

01:10:18.060 | like a confidence that if we have a theory of everything,

01:10:22.720 | we will understand everything.

01:10:24.520 | Like this is the deepest thing to understand.

01:10:26.760 | And I would say, and like the rest is details, right?

01:10:29.820 | That's the old Rutherford thing.

01:10:31.600 | But to me, there's like, this is like a cake or something.

01:10:37.960 | There's layers to this thing

01:10:39.160 | and each one has a theory of everything.

01:10:42.040 | Like at every level from biology,

01:10:46.600 | like how life originates,

01:10:48.660 | that itself, like complex systems.

01:10:52.440 | - Yeah. - Like that in itself

01:10:54.440 | is like this gigantic thing

01:10:56.840 | that requires a theory of everything.

01:10:58.840 | And then there's the, in the space of humans,

01:11:01.640 | psychology, like intelligence, collective intelligence,

01:11:04.680 | the way it emerges among species,

01:11:07.140 | that feels like a complex system

01:11:09.200 | that requires its own theory of everything.

01:11:11.520 | On top of that is things like in the computing space,

01:11:15.420 | artificial intelligence systems,

01:11:16.800 | like that feels like it needs a theory of everything.

01:11:19.440 | And it's almost like once we solve,

01:11:24.440 | once we come up with a theory of everything

01:11:26.640 | that explains the basic laws of physics

01:11:28.500 | that gave us the universe,

01:11:30.320 | even stuff that's super complex,

01:11:32.620 | like how the universe might be able to originate,

01:11:37.120 | even explaining something that you're not a big fan of,

01:11:39.440 | like multiverses or stuff

01:11:40.920 | that we don't have any evidence of yet,

01:11:42.880 | still we won't be able to have a strong explanation

01:11:47.600 | of why food tastes delicious.

01:11:52.640 | - Oh yeah, yeah, no.

01:11:53.640 | No, anyway, yeah, I agree completely.

01:11:55.560 | I mean, there is something kind of completely wrong

01:11:58.680 | with this terminology of theory of everything.

01:12:00.840 | It's not, it's really in some sense a very bad term,

01:12:04.040 | very hubristic and bad terminology because it's not,

01:12:07.780 | this is explaining, this is a purely

01:12:11.880 | kind of reductionist point of view

01:12:13.120 | that you're trying to understand

01:12:14.720 | a certain very specific kind of things,

01:12:17.880 | which in principle other things emerge from,

01:12:22.880 | but to actually understand how anything emerges from this

01:12:27.640 | is it can't be understood in terms of

01:12:30.760 | this underlying Feynman theory is gonna be hopeless

01:12:35.720 | in terms of kind of telling you what about

01:12:37.960 | this various emergent behavior.

01:12:40.940 | And as you go to different levels of explanation,

01:12:43.040 | you're gonna need to develop new,

01:12:44.460 | you know, different, completely different ideas,

01:12:46.060 | completely different ways of thinking.

01:12:47.340 | And I guess there's a famous kind of Phil Anderson's

01:12:51.960 | slogan is that, you know, more is different.

01:12:54.200 | And so it's just, you know,

01:12:57.780 | even once you understand how, what a couple of things,

01:13:00.340 | well, if you have a collection of stuff

01:13:01.900 | and you understand perfectly well

01:13:03.180 | how each thing is interacting with it,

01:13:05.240 | with the others, what the whole thing is gonna do

01:13:08.580 | is just a completely different problem.

01:13:10.140 | It's just not, and you need completely different ways

01:13:12.240 | of thinking about it.

01:13:13.500 | - What do you think about this?

01:13:15.100 | I gotta ask you, at a few different attempts

01:13:17.380 | at a theory of everything, especially recently.

01:13:20.040 | So I've been for many years a big fan

01:13:23.660 | of cellular automata of complex systems.

01:13:25.580 | And obviously because of that,

01:13:28.100 | a fan of Stephen Wolfram's work in that space.

01:13:31.460 | But he's recently been talking about a theory

01:13:34.420 | of everything through his physics project, essentially.

01:13:37.820 | What do you think about this kind of discreet

01:13:40.300 | theory of everything, like from simple rules

01:13:45.100 | and simple objects on the hypergraphs

01:13:47.620 | emerges all of our reality,

01:13:49.300 | where time and space are emergent.

01:13:51.460 | Basically everything we see around us is emergent.

01:13:53.940 | - Yeah, I have to say, unfortunately,

01:13:55.380 | I have kind of pretty much zero sympathy for that.

01:13:58.400 | I mean, I don't, I spent a little time

01:14:01.100 | looking at it and I just don't see,

01:14:03.060 | it doesn't seem to me to get anywhere.

01:14:04.900 | And it really is, just really, really doesn't agree at all

01:14:08.740 | with what I'm seeing, this kind of unification

01:14:12.300 | of math and physics that I'm kind of talking about

01:14:14.380 | around certain kinds of very deep ideas

01:14:16.660 | about geometry and stuff.

01:14:17.980 | If you wanna believe that your things

01:14:22.360 | are really coming out of cellular automata

01:14:25.100 | at the most fundamental level,

01:14:26.740 | you have to believe that everything

01:14:28.780 | that I've seen my whole career

01:14:31.140 | and as beautiful, powerful ideas,

01:14:34.300 | that that's all just kind of a mirage,

01:14:35.700 | which just kind of randomly is emerging

01:14:38.180 | from these more basic, very, very simple-minded things.

01:14:41.460 | And you have to give me some serious evidence for that

01:14:44.940 | and I'm saying nothing.

01:14:46.220 | - So a mirage, you don't think there could be a consistency

01:14:50.380 | where things like quantum mechanics

01:14:53.860 | could emerge from much, much, much smaller, discreet,

01:14:58.440 | like computational-type systems?

01:15:00.060 | - Well, I think from the point of view of,

01:15:01.720 | certain mathematical point of view,

01:15:03.260 | quantum mechanics is already mathematically

01:15:06.380 | as simple as it gets.

01:15:07.380 | It really is a story about really the fundamental objects

01:15:12.380 | that you work with when you write down a quantum theory

01:15:16.380 | are in some point of view,

01:15:18.460 | precisely the fundamental objects

01:15:20.140 | at the deepest levels of mathematics

01:15:22.860 | that you're working with, they're exactly the same.

01:15:25.060 | So, and cellular automata are something completely different

01:15:28.420 | which don't fit into these structures.

01:15:29.980 | And so, I just don't see why, anyway,

01:15:32.500 | I don't see it as a promising thing to do.

01:15:37.300 | And then just looking at it and saying,

01:15:38.540 | does this go anywhere?

01:15:39.460 | Does this solve any problem that I've ever,

01:15:42.400 | that I didn't, does this solve any problem of any kind?

01:15:45.260 | I just don't see it.

01:15:46.700 | - Yeah, to me, cellular automata and these hypergraphs,

01:15:50.560 | I'm not sure solving a problem is even the standard

01:15:55.260 | to apply here at this moment.

01:15:57.660 | To me, the fascinating thing is that the question it asks

01:16:00.540 | have no good answers.

01:16:01.980 | So, there's not good math explaining,

01:16:04.540 | forget the physics of it,

01:16:06.000 | math explaining the behavior of complex systems.

01:16:09.160 | And that to me is both exciting and paralyzing.

01:16:12.300 | Like we're at the very early days of understanding

01:16:15.380 | how complicated and fascinating things emerge

01:16:19.940 | from simple rules.

01:16:21.260 | - Yeah, I agree.

01:16:22.700 | I think that is a truly great problem.

01:16:25.420 | And depending where it goes, it may be,

01:16:28.120 | it may start to develop some kind of connections

01:16:33.600 | to the things that I've kind of found more fruitful

01:16:36.740 | and hard to know.

01:16:38.700 | It just, I think a lot of that area,

01:16:41.420 | I kind of strongly feel I best not say too much about it

01:16:45.740 | 'cause I just, I don't know too much about it.

01:16:48.200 | And I mean, again, we're back to this original problem

01:16:51.580 | that your time in life is limited.

01:16:54.340 | You have to figure out what you're gonna spend

01:16:55.740 | your time thinking about.

01:16:56.780 | And that's something I just never seen enough

01:16:59.020 | to convince me to spend more time thinking about.

01:17:01.420 | - Well, also timing.

01:17:02.340 | It's not just that our time is limited,

01:17:03.920 | but the timing of the kind of things you think about.

01:17:06.900 | There's some aspect to cellular automata,

01:17:09.740 | these kinds of objects that it feels like

01:17:12.820 | we're very many years away from having big breakthroughs on.

01:17:17.820 | And so, it's like you have to pick the problems

01:17:20.420 | that are solvable today.

01:17:21.820 | In fact, my intuition, again, perhaps biased,

01:17:26.420 | is it feels like the kind of systems that,

01:17:30.180 | complex systems that cellular automata are

01:17:32.860 | would not be solved by human brains.

01:17:35.120 | It feels like something post-human

01:17:40.300 | that will solve that problem.

01:17:41.820 | Or like significantly enhanced humans,

01:17:45.020 | meaning like using computational tools,

01:17:47.700 | very powerful computational tools to us,

01:17:50.820 | to crack these problems open.

01:17:53.140 | That's if our approach to science,

01:17:58.140 | our ability to understand science,

01:17:59.740 | our ability to understand physics

01:18:01.620 | will become more and more computational,

01:18:03.500 | or there'll be a whole field that's computational in nature,

01:18:06.300 | which currently is not the case.

01:18:07.740 | Currently, computation is the thing that sort of

01:18:10.780 | assists us in understanding science

01:18:14.660 | the way we've been doing it all along.

01:18:16.720 | But if there's a whole new,

01:18:17.980 | I mean, we're from new kind of science, right?

01:18:20.540 | It's a little bit dramatic.

01:18:22.180 | But, you know, if computers could do science

01:18:27.180 | on their own, computational systems,

01:18:30.060 | perhaps that's the way they would do the science.

01:18:35.560 | They would try to understand the cellular automata.

01:18:37.740 | And that feels like we're decades away.

01:18:39.940 | So, perhaps it'll crack open some interesting facets

01:18:43.940 | of this physics problem, but it's very far away.

01:18:46.300 | So, timing is everything.

01:18:48.180 | - That's perfectly possible, yeah.

01:18:50.060 | - Well, let me ask you then, in the space of geometry,

01:18:53.720 | I don't know how well you know Eric Weinstein.

01:18:57.260 | - Oh, quite well, yeah.

01:18:58.460 | - What are your thoughts about his geometric unity

01:19:03.560 | and the space of ideas that he's playing with

01:19:05.820 | in his proposal for a theory of everything?

01:19:09.740 | - Well, I think that he has,

01:19:12.420 | he fundamentally has, I think,

01:19:14.380 | the same problems that everybody has had trying to do this.

01:19:18.660 | And, you know, they're various,

01:19:19.860 | they're really versions of the same problem

01:19:21.620 | that you try to get unity

01:19:26.100 | by putting everything into some bigger structure.

01:19:28.780 | So, he has some other ones that are not so conventional

01:19:33.420 | that he's trying to work with.

01:19:35.020 | But he has the same problem that even if he can,

01:19:39.580 | if he can get a lot farther in terms of having

01:19:43.620 | a really well-defined, well-understood,

01:19:45.860 | clear picture of these things he's working with,

01:19:50.300 | they're really kind of large geometrical structures

01:19:53.220 | with many dimensions, many kinds.

01:19:55.180 | And I just don't see any way

01:19:57.380 | he's gonna have the same problem the string theorists have.

01:19:59.500 | How do you get back down to the structures

01:20:02.700 | of the standard model?

01:20:04.020 | And how do you, yeah, so I just,

01:20:08.440 | anyway, it's the same.

01:20:10.740 | And there's another interesting example

01:20:13.300 | of some similar kind of thing is Garrett Leasy's

01:20:16.500 | theory of everything.

01:20:17.380 | Again, it's a little bit more specific than Eric's.

01:20:20.580 | He's working with this E8, but again,

01:20:24.620 | I think all these things founder at the same point

01:20:26.900 | that you don't, you create this unity,

01:20:30.780 | but then you have no, you don't actually have a good idea

01:20:34.900 | how you're gonna get back to the actual,

01:20:37.880 | to the objects we've seen.

01:20:42.060 | How are you gonna, you create these big symmetries,

01:20:43.900 | how are you gonna break them?

01:20:45.340 | And 'cause we don't see those symmetries in the real world.

01:20:48.580 | And so ultimately there would need to be a simple process

01:20:53.580 | for collapsing it to four dimensions.

01:20:56.300 | - You'd have to explain it.

01:20:57.140 | Well, yeah, and I forget in his case,

01:20:59.460 | but it's not just four dimensions.

01:21:01.020 | It's also these structures you see in the standard model.

01:21:05.380 | There's certain very small dimensional groups of symmetries

01:21:09.180 | called U1, SU2 and SU3.

01:21:11.380 | And the problem with,

01:21:13.820 | and this has been a problem since the beginning,

01:21:15.260 | almost immediately after 1973, about a year later,

01:21:18.900 | two years later, people started talking

01:21:20.380 | about grand unified theories.

01:21:22.180 | So you take the U1, the SU2 and the SU3,

01:21:26.180 | and you put them in together into this bigger structure

01:21:28.300 | called SU5 or SO10.

01:21:31.560 | But then you're stuck with this problem that,

01:21:33.580 | wait a minute, now how, why does the world not look,

01:21:36.460 | why do I not see these SU5 symmetries in the world?

01:21:41.020 | I only see these.

01:21:42.500 | And so, and I think those,

01:21:47.240 | the kind of thing that Eric and also in Garrett

01:21:49.900 | and lots of people will try to do,

01:21:51.020 | they all kind of founder in that same way

01:21:55.220 | that they don't have a good answer to that.

01:21:57.700 | - Are there lessons, ideas to be learned

01:22:01.300 | from theories like that, from Garrett Leases, from Eric's?

01:22:04.200 | - I don't know, it depends.

01:22:06.220 | I have to confess, I haven't looked that closely at Eric's.

01:22:11.020 | I mean, he explained to this to me personally a few times

01:22:14.220 | and I've looked a bit at his paper, but it's,

01:22:16.420 | again, we're back to the problem

01:22:19.220 | of a limited amount of time in life.

01:22:21.020 | - Yeah, I mean, it's an interesting effect, right?

01:22:24.840 | Why don't more physicists look at it?

01:22:28.800 | I mean, I'm in this position that somehow

01:22:35.820 | I've, people write me emails for whatever reason

01:22:40.820 | and I worked in the space of AI

01:22:47.420 | and so there's a lot of people,

01:22:49.140 | perhaps AI is even way more accessible than physics

01:22:52.260 | in a certain sense.

01:22:53.420 | And so a lot of people write to me

01:22:54.940 | with different theories about what they have

01:22:56.680 | for how to create general intelligence.

01:22:59.980 | And it's, again, a little bit of an excuse I say to myself,

01:23:03.340 | like, well, I only have a limited amount of time,

01:23:05.380 | so that's why I'm not investigating it.

01:23:07.900 | But I wonder if there's ideas out there

01:23:11.580 | that are still powerful, they're still fascinating,

01:23:14.660 | and that I'm missing because I'm dismissing them

01:23:19.660 | because they're outside of the sort of the usual process

01:23:24.700 | of academic research.

01:23:26.740 | - Yeah, well, I mean, the same thing pretty much every day

01:23:29.340 | in my email, there's a, somebody's got a theory

01:23:32.620 | or everything about why all of what physicists are doing.

01:23:35.420 | Perhaps the most disturbing thing I should say

01:23:38.940 | about my critique, being a critic of string theory

01:23:41.740 | is that when you realize who your fans are,

01:23:44.700 | that they, every day I hear from somebody who says,

01:23:47.060 | oh, well, since you don't like string theory,

01:23:48.620 | you must of course agree with me

01:23:49.980 | that this is the right way to think about everything.

01:23:52.240 | Oh no, oh no.

01:23:53.980 | And most of these are, you quickly can see this is,

01:23:58.980 | person doesn't know very much

01:24:00.820 | and doesn't know what they're doing,

01:24:02.500 | but there's a whole continuum to people

01:24:05.380 | who are quite serious physicists and mathematicians

01:24:08.020 | who are making a fairly serious attempt

01:24:10.340 | to try to do something like Garrett and Eric.

01:24:14.580 | And then your problem is, you do try to spend more time

01:24:19.580 | looking at it and trying to figure out

01:24:22.540 | what they're really doing,

01:24:23.620 | but then at some point you just realize, wait a minute,

01:24:26.940 | for me to really, really understand exactly

01:24:28.580 | what's going on here would just take time.

01:24:32.300 | I just don't have.

01:24:33.580 | - Yeah, it takes a long time.

01:24:34.660 | Which is the nice thing about AI

01:24:36.980 | is unlike the kind of physics we're talking about,

01:24:41.140 | if your idea is good, that should quite naturally lead

01:24:46.140 | to you being able to build a system that's intelligent.

01:24:49.820 | So you don't need to get approval from somebody

01:24:52.280 | that's saying you have a good idea here.

01:24:54.480 | You can just utilize that idea in an engineer system.

01:24:56.940 | Like naturally leads to engineering.

01:24:58.860 | With physics here, if you have a perfect theory

01:25:01.940 | that explains everything,

01:25:03.220 | that still doesn't obviously lead,

01:25:06.020 | one, to scientific experiments that can validate that theory,

01:25:11.020 | and two, to trinkets you can build and sell at a store

01:25:17.780 | for $5. - You can't make money off of it.

01:25:19.820 | (laughing)

01:25:21.180 | - So that makes it much more challenging.

01:25:23.620 | Well, let me also ask you about something that you found,

01:25:28.540 | especially recently, appealing,

01:25:30.520 | which is Roger Penrose's twister theory.

01:25:32.800 | What is it?

01:25:35.140 | What kind of questions might it allow us to answer?

01:25:37.780 | What will the answers look like?

01:25:39.860 | - It's only in the last couple years

01:25:41.580 | that I really, really kind of come to really, I think,

01:25:43.960 | to appreciate it and to see how to really,

01:25:46.100 | I believe, to see how to really do something with it.

01:25:48.460 | And I've gotten very excited about that the last year or two.

01:25:51.180 | I mean, one way of saying, one idea of twister theory

01:25:54.780 | is that it's a different way of thinking

01:25:58.220 | about what space and time are

01:26:00.800 | and about what points in space and time are,

01:26:03.240 | but which is very interesting

01:26:05.100 | that it only really works in four dimensions.

01:26:07.400 | So four dimensions behaves very, very specially

01:26:09.700 | unlike other dimensions.

01:26:11.200 | And in four dimensions, there's certain,

01:26:13.420 | there is a way of thinking about space and time geometry

01:26:16.560 | where, as well as just thinking about points

01:26:19.680 | in space and time, you can also think

01:26:24.300 | about different objects, these so-called twisters.

01:26:26.240 | And then when you do that, you end up

01:26:28.600 | with a kind of a really interesting insight

01:26:30.920 | that you can formulate a theory,

01:26:35.320 | and you can formulate a very, take a standard theory

01:26:38.380 | that we formulate in terms of points of space and time,

01:26:41.680 | and you can reformulate in this twister language.

01:26:44.520 | And in this twister language, it's the,

01:26:46.760 | the fundamental objects are actually, are more kind of the,

01:26:51.340 | are actually spheres in some sense, kind of the light cone.

01:26:54.140 | So maybe one way to say it, which actually I think

01:26:58.160 | is really, is quite amazing, is if you ask yourself,

01:27:03.160 | what do we know about the world?

01:27:05.160 | We have this idea that the world out there is this,

01:27:08.720 | all these different points and these points of time.

01:27:11.360 | Well, that's kind of a derived quantity.

01:27:13.220 | What we really know about the world is when we open our eyes,

01:27:16.300 | what do you see?

01:27:17.480 | You see a sphere.

01:27:19.600 | And that what you're looking at is you're looking at,

01:27:23.120 | a sphere is worth of light rays coming into your eyes.

01:27:26.520 | And what Penrose says is that,

01:27:29.160 | well, what a point in space time is, is that sphere,

01:27:33.800 | that sphere of all the light rays coming in.

01:27:36.600 | And he says, and you should formulate your,

01:27:39.200 | instead of thinking about points,

01:27:40.720 | you should think about the space of those spheres,

01:27:43.080 | if you like, and formulate the degrees of freedom

01:27:46.840 | as physics as living on those spheres, living on,

01:27:50.020 | so you're kind of living on,

01:27:51.940 | your degrees of freedom are living on light rays,

01:27:53.640 | not on points.

01:27:55.200 | And it's a very different way of thinking about physics.

01:28:00.200 | And he and others working with him developed a,

01:28:03.740 | a beautiful mathematical,

01:28:07.120 | beautiful mathematical formalism

01:28:08.440 | and a way to go back from forth between our kind of,

01:28:10.680 | some aspects of our standard way we write these things down

01:28:14.240 | and work in the so-called twister space.

01:28:17.440 | And they, certain things worked out very well,

01:28:20.440 | but they ended up, I think kind of stuck

01:28:23.800 | by the 80s or 90s that they weren't,

01:28:25.720 | a little bit like string theory, that they,

01:28:29.680 | by using these ideas about twisters,

01:28:31.280 | they could develop them in different directions

01:28:33.120 | and find all sorts of other interesting things,

01:28:34.840 | but they were getting,

01:28:36.960 | they weren't finding any way of doing that

01:28:38.620 | that brought them back to kind of new insights into physics.

01:28:43.200 | And my own, I mean, what's kind of gotten me excited really

01:28:46.480 | is what I think I have an idea about

01:28:49.760 | that I think does actually,

01:28:51.640 | does actually work that goes more in that direction.

01:28:54.200 | And I can go on about that endlessly

01:28:56.800 | or talk a little bit about it, but that's the,

01:28:59.100 | I think that that's the one kind of easy to explain

01:29:03.200 | inside about twister theory.

01:29:05.240 | There are some more technical ones I should,

01:29:07.200 | I mean, I think it's also very convincing

01:29:09.360 | what it tells you about spinners, for instance,

01:29:11.280 | but that's a more technical.

01:29:12.960 | - Well, first let's like linger on the spheres

01:29:15.000 | and the light cones.

01:29:17.480 | You're saying twister theory allows you to make that

01:29:21.000 | the fundamental object with which you're operating.

01:29:23.760 | - Yeah.

01:29:24.600 | - I mean, first of all, like philosophically,

01:29:27.360 | that's weird and beautiful.

01:29:30.840 | Maybe because it maps,

01:29:34.520 | it feels like it moves us so much closer

01:29:37.000 | to the way human brains perceive reality.

01:29:40.760 | So it's almost like,

01:29:44.800 | our perception is,

01:29:46.440 | like the content of our perception

01:29:51.480 | is the fundamental object of reality.

01:29:54.520 | That's very appealing.

01:29:55.880 | - Yeah.

01:29:57.200 | - Is it mathematically powerful?

01:30:00.600 | Is there something you can say,

01:30:03.760 | can you say a little bit more

01:30:05.800 | about what the heck that even means for,

01:30:08.360 | 'cause it's much easier to think about mathematically

01:30:11.240 | like a point in space-time.

01:30:13.520 | Like what does it mean to be operating on the light cone?

01:30:16.880 | - It uses a kind of mathematics that's relative,

01:30:19.360 | that was, kind of goes back to the 19th century

01:30:22.040 | among mathematicians.

01:30:23.040 | It's not, anyway, it's a bit of a long story,

01:30:26.400 | but the one problem is that you have to start,

01:30:28.840 | it's crucial that you think in terms of complex numbers

01:30:31.720 | and not just real numbers.

01:30:32.880 | And this, for most people, that makes it harder to,

01:30:36.320 | for mathematicians, that's fine.

01:30:37.600 | We love doing that.

01:30:38.440 | But for most people, that makes it harder to think about.

01:30:40.840 | But I think perhaps the most,

01:30:43.080 | the way that there is something you can say

01:30:45.520 | very specifically about it, in terms of spinners,

01:30:49.080 | which I don't know if you wanna,

01:30:50.040 | I think at some point you wanna talk.

01:30:51.760 | So maybe again-- - What are spinners?

01:30:53.360 | - Let's start with spinner,

01:30:54.200 | 'cause I think that if we can introduce that,

01:30:56.000 | then I can say-- - By the way,

01:30:58.520 | twister is spelled with an O,

01:31:01.000 | and spinner is spelled with an O as well.

01:31:03.720 | - Yes, okay.

01:31:05.240 | So-- - In case you wanna Google it

01:31:06.800 | and look it up, there's very nice Wikipedia pages

01:31:09.680 | as a starting point.

01:31:10.920 | I don't know what is a good starting point

01:31:12.400 | for twister theory. (laughs)

01:31:14.520 | - Well, one thing I say about Penrose,

01:31:16.080 | I mean, Penrose is actually a very good writer

01:31:18.120 | and also a very good draftsman.

01:31:19.400 | He's a draftsman.

01:31:20.480 | To the extent this is visualizable,

01:31:22.040 | he actually has done some very nice drawings.

01:31:23.680 | So I mean, almost any kind of expository thing

01:31:26.480 | you can find him writing is a very good place to start.

01:31:29.840 | He's a remarkable person.

01:31:32.560 | But the, so spinners are something

01:31:36.040 | that independently came out of mathematics

01:31:38.360 | and out of physics.

01:31:40.080 | And to say where they came out of physics,

01:31:42.640 | I mean, what people realized when they started looking

01:31:44.640 | at elementary particles like electrons or whatever,

01:31:47.600 | that there seemed to be some kind of doubling

01:31:51.680 | of the degrees of freedom going on.

01:31:53.160 | If you counted what was there in some sense

01:31:57.120 | in the way you would expect it,

01:31:58.200 | and when you started doing quantum mechanics

01:32:00.080 | and started looking at elementary particles,

01:32:01.800 | there were seem to be two degrees of freedom.

01:32:03.760 | There are not one.

01:32:04.920 | And one way of seeing it was that if you put

01:32:08.800 | your electron in a strong magnetic field

01:32:11.920 | and asked what was the energy of it,

01:32:14.120 | instead of it having one energy,

01:32:15.520 | it would have two energies.

01:32:16.760 | There'd be two energy levels.

01:32:17.920 | And as you increase magnetic field,

01:32:20.480 | the splitting would increase.

01:32:22.080 | So physicists kind of realized that, wait a minute.

01:32:24.960 | So we thought when we were doing,

01:32:27.000 | first started doing quantum mechanics,

01:32:28.200 | that the way to describe particles

01:32:31.120 | was in terms of wave functions.

01:32:32.560 | And these wave functions were complex to complex values.

01:32:35.840 | Well, if we actually look at particles,

01:32:38.080 | that's not right.

01:32:38.920 | They're pairs of complex numbers.

01:32:42.080 | They're pairs of complex numbers.

01:32:44.120 | So one of the kind of fundamental,

01:32:46.920 | from the physics point of view,

01:32:47.840 | the fundamental question is,

01:32:49.080 | why are all our kind of fundamental particles

01:32:51.720 | described by pairs of complex numbers?

01:32:55.760 | Just weird.

01:32:56.600 | And then you can ask, well, what happens if you

01:33:01.600 | take an electron and rotate it?

01:33:03.200 | So how do things move in this pair of complex numbers?

01:33:08.520 | Well, now, if you go back to mathematics,

01:33:10.920 | what had been understood in mathematics

01:33:13.840 | some years earlier, not that many years earlier,

01:33:16.360 | was that if you ask very, very generally,

01:33:20.440 | think about geometry of three dimensions and ask,

01:33:24.240 | and if you think about things that are happening

01:33:25.800 | in three dimensions in the standard way,

01:33:28.240 | everything, the standard way of doing geometry,

01:33:30.480 | everything is about vectors, right?

01:33:32.520 | So if you take any mathematics classes,

01:33:35.160 | you probably see vectors at some point.

01:33:36.680 | They're just triplets of numbers tell you

01:33:39.400 | what a direction is or how far you're going

01:33:41.600 | in three-dimensional space.

01:33:42.960 | And most of everything we teach in most standard courses

01:33:46.240 | in mathematics is about vectors

01:33:49.680 | and things you build out of vectors.

01:33:51.400 | So you express everything about geometry

01:33:53.040 | in terms of vectors or how they're changing

01:33:55.400 | or how you put two of them together

01:33:57.600 | and get planes and whatever.

01:34:00.920 | But what had been realized early on

01:34:03.880 | is that if you ask very, very generally,

01:34:05.800 | what are the things that you can kind of consistently think

01:34:10.800 | about rotating?

01:34:13.040 | And so you ask a technical question,

01:34:16.360 | what are the representations of the rotation group?

01:34:18.640 | Well, you find that one answer is they're vectors

01:34:22.240 | and everything you build out of vectors.

01:34:24.720 | But then people found, but wait a minute,

01:34:26.440 | there's also these other things

01:34:28.400 | which you can't build out of vectors,

01:34:31.840 | but which you can consistently rotate.

01:34:34.440 | And they're described by pairs of complex numbers,

01:34:37.040 | by two complex numbers.

01:34:38.440 | And they're the spinners also.

01:34:40.360 | And you can think of spinners in some sense

01:34:45.080 | as more fundamental than vectors

01:34:46.640 | because you can build vectors out of spinners.

01:34:48.840 | You can take two spinners and make a vector,

01:34:51.160 | but if you only have vectors, you can't get spinners.

01:34:56.160 | So they're in some sense,

01:34:58.160 | there's some kind of lower level of geometry

01:35:00.980 | beyond what we thought it was,

01:35:02.160 | which was kind of spinner geometry.

01:35:04.240 | And this is something which even to this day

01:35:07.360 | when we teach graduate courses in geometry,

01:35:09.440 | we mostly don't talk about this

01:35:11.720 | because it's a bit hard to do correctly.

01:35:15.360 | If you start with your whole setup

01:35:17.560 | is in terms of vectors,

01:35:18.880 | describing things in terms of spinners

01:35:22.000 | is a whole different ball game.

01:35:24.000 | But anyway, it was just this amazing fact

01:35:28.760 | that this kind of more fundamental piece of geometry

01:35:33.000 | of spinners and what we were actually seeing,

01:35:35.440 | if you look at electron are one in the same.

01:35:37.920 | So I think it's kind of a mind blowing thing,

01:35:41.340 | but it's very counterintuitive.

01:35:44.920 | - What are some weird properties of spinners

01:35:47.080 | that are counterintuitive?

01:35:50.260 | - That there are some things that they do.

01:35:51.560 | For instance, if you rotate a spinner around 360 degrees,

01:35:56.320 | it doesn't come back towards,

01:35:58.000 | it becomes minus what it was.

01:36:01.300 | So it's, anyway, so the way rotations work,

01:36:04.700 | there's a kind of a funny sign

01:36:05.960 | you have to keep track of in some sense.

01:36:08.220 | So they're kind of too valued in another weird way.

01:36:11.080 | But the fundamental problem is that it's just not,

01:36:14.760 | if you're used to visualizing vectors,

01:36:17.620 | there's nothing you can do visualizing in terms of vectors

01:36:20.620 | that will ever give you a spinner.

01:36:21.900 | It just is not gonna ever work.

01:36:23.900 | - As you were saying that I was visualizing a vector

01:36:26.660 | walking along a Mobius strip

01:36:28.900 | and it ends up being upside down.

01:36:31.900 | But you're saying that doesn't really capture.

01:36:34.820 | - So what really captures it,

01:36:36.860 | the problem is that it's really,

01:36:39.500 | the simplest way to describe it

01:36:41.220 | is in terms of two complex numbers.

01:36:43.420 | And your problem with two complex numbers

01:36:45.060 | is that's four real numbers.

01:36:46.820 | So your spinner kind of lies in a four dimensional space.

01:36:50.540 | So that makes it hard to visualize.

01:36:53.820 | And it's crucial that it's not just any four dimensions,

01:36:57.540 | it's just, it's actually complex numbers.

01:36:59.340 | You're really gonna use the fact that

01:37:01.780 | these are two complex numbers.

01:37:03.220 | So it's very hard to visualize.

01:37:06.180 | But to get back to what I think is mind blowing

01:37:09.340 | about twisters is that the,

01:37:12.020 | another way of saying this idea about talking about spheres,

01:37:15.820 | another way of saying the fundamental idea

01:37:17.380 | of twister theory is,

01:37:19.460 | in some sense the fundamental idea of twister theory

01:37:21.580 | is that a point is a two complex dimensional space.

01:37:28.740 | So that every, and that it lives inside,

01:37:32.060 | the space that it lies inside is twister space.

01:37:34.580 | So in the simplest case, it's four,

01:37:36.740 | twister space is four dimensional.

01:37:38.500 | And a point in space time is a two complex dimensional

01:37:43.060 | subspace of all the four complex dimensions.

01:37:47.500 | And as you move around in space time,

01:37:49.020 | you're just moving, your planes are just moving around.

01:37:51.660 | Okay.

01:37:52.500 | And that, but then the--

01:37:54.820 | - So it's a plane in a four dimensional space.

01:37:57.020 | - It's a, yeah, a plane--

01:37:58.700 | - Complex.

01:37:59.540 | - Complex plane.

01:38:00.380 | So it's two complex dimensions in four complex.

01:38:03.100 | - Got it.

01:38:03.940 | - But then to me, the mind blowing thing about this

01:38:05.820 | is this then kind of tautologically answers the question

01:38:09.420 | is what is a spinner?

01:38:10.420 | Well, a spinner is a point.

01:38:14.140 | I mean, the space of spinners at a point is the point.

01:38:17.940 | In twister theory, the points are the complex two planes.

01:38:21.540 | And you want me to, and you're asking what a spinner is.

01:38:24.660 | Well, a spinner, the space of spinners is that two plane.

01:38:28.300 | So it's just your whole definition

01:38:31.820 | of what a point in space time was

01:38:33.380 | just told you what a spinner was.

01:38:35.220 | It's the same thing.

01:38:37.220 | - Yeah, well, we're trying to project that

01:38:38.500 | into a three dimensional space and trying to intuit,

01:38:41.340 | but you can't.

01:38:42.260 | - Yeah, so the intuition becomes very difficult,

01:38:44.140 | but from, if you don't, not using twister theory,

01:38:49.140 | you have to kind of go through a certain

01:38:51.340 | fairly complicated rigmarole to even describe spinners,

01:38:54.580 | to describe electrons.

01:38:55.980 | Whereas using twister theory,

01:38:57.220 | it's just completely tautological.

01:38:58.820 | They're just what you want to describe.

01:39:03.100 | The electron is fundamentally the way

01:39:05.980 | you're describing the point in space time already.

01:39:08.180 | It's just there.

01:39:09.120 | - Do you have a hope?

01:39:11.580 | You mentioned that you've been,

01:39:13.260 | you found it appealing recently.

01:39:14.940 | Is it just because of certain aspects

01:39:17.260 | of its mathematical beauty,

01:39:18.500 | or do you actually have a hope that this might lead

01:39:20.460 | to a theory of everything?

01:39:22.580 | - Yeah, I mean, I certainly do have such a hope

01:39:25.100 | 'cause what I've found,

01:39:26.500 | I think the thing which I've done,

01:39:27.980 | which I don't think, as far as I can tell,

01:39:29.740 | no one had really looked at from this point of view before,

01:39:33.380 | is, has to do with this question of how do you treat time

01:39:38.380 | in your quantum theory?

01:39:40.820 | And so there's another long story

01:39:44.420 | about how we do quantum theories

01:39:46.660 | and about how we treat time in quantum theories,

01:39:48.700 | which is a long story.

01:39:51.780 | But to me, the short version of it is that

01:39:54.500 | what people have found when you try and write down

01:39:56.620 | a quantum theory,

01:39:58.500 | that it's often a good idea to take your time coordinate,

01:40:03.500 | whatever you're using to your time coordinate,

01:40:07.140 | and multiply it by the square root of minus one

01:40:09.980 | and to make it purely imaginary.

01:40:12.020 | And so all these formulas which you have

01:40:14.500 | in your standard theory,

01:40:18.460 | if you do that to those,

01:40:19.900 | I mean, those formulas have some very strange behavior

01:40:23.660 | and they're kind of singular.

01:40:25.380 | If you ask even some simple questions,

01:40:27.800 | you have to take very delicate singular limits

01:40:31.020 | in order to get the correct answer.

01:40:33.260 | And you have to take them from the right direction,

01:40:35.060 | otherwise it doesn't work.

01:40:36.980 | Whereas if you just take time,

01:40:39.980 | and if you just put a factor of square root of minus one,

01:40:42.140 | wherever you see the time coordinate,

01:40:44.260 | you end up with much simpler formulas,

01:40:47.340 | which are much better behaved mathematically.

01:40:49.900 | And what I hadn't really appreciated until fairly recently

01:40:52.900 | is also how dramatically that changes

01:40:55.500 | the whole structure of the theory.

01:40:57.260 | You end up with a consistent way of talking

01:40:59.780 | about these quantum theories,

01:41:01.600 | but it has some very different flavor

01:41:04.300 | and very different aspects that I hadn't really appreciated.

01:41:07.380 | And in particular, the way symmetries act on it

01:41:10.900 | is not at all what I originally had expected.

01:41:15.060 | And so that's the new thing that I've,

01:41:17.660 | or I think gives you something is to do this move,

01:41:21.820 | which people often think of as just kind of a,

01:41:24.220 | kind of a mathematical trick that you're doing

01:41:27.380 | to make some formulas work out nicely,

01:41:29.780 | but to take that mathematical trick as really fundamental.

01:41:33.180 | And it turns out in twister theory,

01:41:35.940 | allows you to simultaneously talk about your usual time

01:41:39.540 | and the time times the square root of minus one.

01:41:41.900 | They both fit very nicely into twister theory.

01:41:45.500 | And you end up with some structures,

01:41:48.380 | which look a lot like the standard models.

01:41:51.480 | - Well, let me ask you about some Nobel prizes.

01:41:54.120 | - Okay.

01:41:55.280 | - Do you think there will be,

01:41:56.720 | there was a bet between Michio Kaku and somebody else.

01:42:03.360 | - John Horgan.

01:42:05.040 | - John Horgan about, by the way,

01:42:07.760 | maybe discover a cool website, longbets.com or .org.

01:42:11.160 | - Yeah, yeah.

01:42:12.120 | - It's cool.

01:42:12.960 | It's cool that you can make a bet with people

01:42:15.160 | and then check in 20 years later.

01:42:18.360 | That's, I really love it.

01:42:19.480 | There's a lot of interesting bets on there.

01:42:21.120 | - Yeah.

01:42:21.960 | - I would love to participate, but it's interesting to see,

01:42:23.840 | you know, time flies.

01:42:25.160 | - Yeah.

01:42:26.160 | - And you make a bet about what's going to happen 20 years.

01:42:28.880 | You don't realize 20 years just goes like this.

01:42:31.040 | - Yeah, yeah.

01:42:31.880 | - And then you get to face, and you get to wonder,

01:42:35.520 | like, what was that person, what was I thinking?

01:42:40.520 | That person 20 years ago is almost like a different person.

01:42:43.840 | What was I thinking back then to think that?

01:42:46.320 | It's interesting.

01:42:47.200 | But, so let me ask you this, on record,

01:42:49.600 | you know, 20 years from now or some number of years from now,

01:42:54.000 | do you think there'll be a Nobel Prize given

01:42:55.780 | for something directly connected

01:42:58.280 | to a first broadly theory of everything?

01:43:01.720 | And second, of course, one of the possibilities,

01:43:05.960 | one of them, string theory?

01:43:08.240 | - String theory, definitely not.

01:43:13.040 | The things have gone, yeah.

01:43:16.200 | - So if you were giving financial advice,

01:43:18.120 | you would say not to bet on it?

01:43:19.120 | - No, do not bet on it.

01:43:20.320 | And even, I actually suspect if you ask string theorists

01:43:23.600 | that question, these days,

01:43:24.840 | you're gonna get few of them saying,

01:43:27.480 | I mean, if you'd asked them that question 20 years ago,

01:43:29.560 | again, when Kaku was making this bet or whatever,

01:43:32.120 | I think some of them would have taken you up on it.

01:43:34.480 | But, and certainly back in 1984,

01:43:36.960 | a bunch of them would have said, oh, sure, yeah.

01:43:38.960 | But now, I get the impression that they've,

01:43:43.000 | even they realize that things are not looking good

01:43:45.640 | for that particular idea.

01:43:46.840 | Again, it depends what you mean by string theory,

01:43:48.580 | whether maybe the term will evolve to mean something else,

01:43:51.880 | which will work out.

01:43:53.760 | But yeah, I don't think that's not gonna like it to work out

01:43:57.360 | whether something else, I mean,

01:43:59.200 | I still think it's relatively unlikely

01:44:01.200 | that you'll have any really successful theory of everything.

01:44:04.920 | And the main problem is just the,

01:44:07.460 | it's become so difficult to do experiments

01:44:11.080 | at higher energy that we've really lost this ability

01:44:13.560 | to kind of get unexpected input from experiment.

01:44:18.560 | And you can, while it may be hard to figure out

01:44:22.220 | what people's thinking is gonna be 20 years from now,

01:44:24.860 | looking at high energy particle,

01:44:28.760 | high energy colliders and their technology,

01:44:30.920 | it's actually pretty easy to make a pretty accurate guess

01:44:33.560 | what it's gonna look,

01:44:34.400 | what you're gonna be doing 20 years from now.

01:44:37.280 | And I think actually, I would actually claim that

01:44:42.400 | it's pretty clear where you're gonna be 20 years from now.

01:44:44.560 | And what it's gonna be is you're gonna have the,

01:44:46.960 | you're gonna have the LHC,

01:44:50.080 | you're gonna have a lot more data,

01:44:51.520 | an order of magnitude or more data from the LHC,

01:44:56.120 | but at the same energy.

01:44:57.600 | You're not gonna see a higher energy accelerator

01:45:01.960 | operating successfully in the next 20 years.

01:45:05.360 | - And like maybe machine learning

01:45:08.160 | or great sort of data science methodologies

01:45:10.280 | that process that data will not reveal any major

01:45:14.800 | like shift in our understanding

01:45:17.400 | of the underlying physics, you think?

01:45:19.200 | - I don't think so.

01:45:20.040 | I mean, I think that field,

01:45:22.480 | my understanding is that they're starting

01:45:25.280 | to make a great use of those techniques,

01:45:26.960 | but it seems to look like it will help them

01:45:29.560 | solve certain technical problems

01:45:31.040 | and be able to do things somewhat better,

01:45:32.560 | but not completely change

01:45:35.480 | the way they're looking at things.

01:45:36.640 | - What do you think about the potential quantum computers

01:45:39.600 | simulating quantum mechanical systems

01:45:41.280 | and through that sneak up to sort of,

01:45:44.760 | through simulation sneak up to a deep understanding

01:45:48.280 | of the fundamental physics?

01:45:51.560 | - The problem there is that's promising more for this,

01:45:55.360 | for Phil Anderson's problem that if you wanna,

01:46:01.520 | there's lots and lots of,

01:46:03.080 | you start putting together lots and lots of things

01:46:08.600 | and we think we know that are pair by pair interactions,

01:46:11.080 | but what this thing is gonna do,

01:46:13.360 | we don't have any good calculational techniques.

01:46:16.320 | You know, quantum computers may very well give you those.

01:46:19.520 | And so they may, what we think of

01:46:21.640 | as kind of a strong coupling behavior,

01:46:23.240 | we have no good way to calculate.

01:46:25.240 | You know, even though we can write down the theory,

01:46:28.280 | we don't know how to calculate anything

01:46:30.640 | with any accuracy in it.

01:46:32.080 | The quantum computers may solve that problem.

01:46:34.640 | But the problem is that they,

01:46:35.800 | I don't think that they're gonna solve the problem

01:46:38.160 | that they help you with the problem of not having the,

01:46:41.080 | of knowing what the right underlying theory is.

01:46:44.200 | - As somebody who likes experimental validation,

01:46:48.520 | let me ask you the perhaps ridiculous sounding,

01:46:51.280 | but I don't think it's actually a ridiculous question of,

01:46:54.520 | do you think we live in a simulation?

01:46:56.680 | Do you find that thought experiment

01:46:58.320 | at all useful or interesting?

01:47:00.200 | - Not really, I don't, it just doesn't,

01:47:05.760 | yeah, anyway, to me, it doesn't actually lead

01:47:08.680 | to any kind of interesting, lead anywhere interesting.

01:47:11.960 | - Yeah, to me, so maybe I'll throw a wrench into your thing.

01:47:15.540 | To me, it's super interesting

01:47:17.880 | from an engineering perspective.

01:47:19.620 | So if you look at virtual reality systems,

01:47:21.860 | the actual question is, how much computation

01:47:28.160 | and how difficult is it to construct a world

01:47:32.960 | that, like there are several levels here.

01:47:35.760 | One is you won't know the difference,

01:47:39.720 | our human perception systems,

01:47:41.360 | and maybe even the tools of physics won't know

01:47:43.040 | the difference between the simulated world

01:47:44.920 | and the real world.

01:47:45.880 | That's sort of more of a physics question.

01:47:51.000 | The most interesting question to me has more to do

01:47:53.780 | with why food tastes delicious,

01:47:55.720 | which is create how difficult and how much computation

01:47:59.920 | is required to construct a simulation

01:48:02.840 | where you kind of know it's a simulation at first,

01:48:06.080 | but you wanna stay there anyway.

01:48:07.840 | And over time, you don't even remember.

01:48:12.840 | - Yeah, well, anyway, I agree,

01:48:15.840 | these are kind of fascinating questions

01:48:18.320 | and they may be very, very relevant

01:48:20.000 | to our future as a species,

01:48:21.880 | but yeah, they're just very far from anything.

01:48:24.760 | - But so from a physics perspective,

01:48:27.560 | it's not useful to you to think,

01:48:29.360 | taking a computational perspective to our universe,

01:48:32.320 | thinking of it as an information processing system,

01:48:35.120 | and then think of it as doing computation,

01:48:37.400 | and then you think about the resources required

01:48:39.400 | to do that kind of computation and all that kind of stuff.

01:48:42.240 | You could just look at the basic physics

01:48:43.760 | and who cares what the computer it's running on is.

01:48:46.680 | - Yeah, it just, I mean, the kinds of,

01:48:47.960 | I mean, I'm willing to agree that you can get

01:48:50.560 | into interesting kinds of questions going down that road,

01:48:52.760 | but they're just so different from anything,

01:48:55.200 | from what I've found interesting.

01:48:56.280 | And I just, again, I just have to kind of go back to,

01:49:00.320 | life is too short and I'm very glad

01:49:02.320 | other people are thinking about this,

01:49:03.680 | but I just don't see anything I can do with it.

01:49:07.500 | - What about space itself?

01:49:11.440 | So I have to ask you about aliens.

01:49:13.140 | Again, something, since you emphasize evidence,

01:49:17.640 | do you think there is, how many,

01:49:20.800 | do you think there are and how many

01:49:22.960 | intelligent alien civilizations are out there?

01:49:25.880 | - Yeah, I have no idea, but I've certainly,

01:49:28.520 | as far as I know, unless the government's covering it up

01:49:30.680 | or something, we haven't heard from,

01:49:32.960 | we don't have any evidence for such things yet,

01:49:35.720 | but there seems to be no,

01:49:37.520 | there's no particular obstruction why there shouldn't be.

01:49:42.040 | - I mean, do you, you work on some fundamental questions

01:49:47.440 | about the physics of reality.

01:49:49.120 | When you look up to the stars,

01:49:51.600 | do you think about whether somebody's looking back at us?

01:49:55.200 | - Yes, yeah, well, actually,

01:49:56.120 | I originally got interested in physics.

01:49:58.080 | I actually started out as a kid interested in astronomy,

01:50:00.160 | exactly that, and telescope and whatever that,

01:50:02.280 | and certainly read a lot of science fiction

01:50:05.600 | and thought about that.

01:50:08.320 | I find over the years, I find myself kind of less,

01:50:12.000 | anyway, less and less interested in that,

01:50:15.080 | just because I don't really know what to do with them.

01:50:18.080 | I also kind of at some point kind of stopped

01:50:21.400 | reading science fiction that much,

01:50:23.040 | kind of feeling that there was just too,

01:50:25.080 | that the actual science I was kind of learning about

01:50:27.080 | was perfectly kind of weird and fascinating

01:50:29.880 | and unusual enough and better than any of the stuff

01:50:33.120 | that Isaac Asimov, so why shouldn't I?

01:50:36.600 | - Yeah, and you can mess with the science

01:50:39.720 | much more than the distant science fiction,

01:50:42.300 | the one that exists in our imagination

01:50:45.400 | or the one that exists out there among the stars.

01:50:48.320 | Well, you mentioned science fiction.

01:50:51.200 | You've written quite a few book reviews.

01:50:54.080 | I gotta ask you about some books, perhaps,

01:50:56.440 | if you don't mind.

01:50:57.540 | Is there one or two books that you would recommend

01:51:02.920 | to others, and maybe if you can,

01:51:05.260 | what ideas you drew from them?

01:51:07.020 | Either negative recommendations or positive recommendations.

01:51:12.680 | Do not read this book for sure.

01:51:15.200 | - Well, I must say, I mean, unfortunately,

01:51:17.480 | yeah, well, you can go to my website

01:51:19.880 | and you can click on book reviews

01:51:21.680 | and you can see I've written, read a lot of,

01:51:24.080 | I mean, as you can tell from my views about string theory,

01:51:27.880 | I'm not a fan of a lot of the kind of popular books

01:51:31.000 | about, oh, isn't string theory great?

01:51:32.720 | And yes, I'm not a fan of a lot of things of that kind.

01:51:37.720 | - Can I ask you a quick question on this, a small tangent?

01:51:40.520 | Are you a fan, can you explore the pros and cons

01:51:46.400 | of, forget string theory, sort of science communication,

01:51:51.600 | sort of cosmos style communication of concepts

01:51:56.600 | to people that are outside of physics,

01:51:59.040 | outside of mathematics, outside of even the sciences,

01:52:02.240 | and helping people to sort of dream

01:52:04.800 | and fill them with awe about the full range of mysteries

01:52:08.160 | in our universe?

01:52:09.080 | - That's a complicated issue.

01:52:11.260 | You know, I think, you know, I certainly go back

01:52:13.680 | and go back to like what inspired me

01:52:15.680 | and maybe to connect it a little bit

01:52:18.440 | to this question about books.

01:52:19.340 | I mean, certainly when the books that,

01:52:21.560 | some books that I remember reading when I was a kid

01:52:24.000 | were about the early history of quantum mechanics,

01:52:26.300 | like Heisenberg's books that he wrote about, you know,

01:52:29.060 | kind of looking back at telling the history

01:52:31.100 | of what happened when he developed quantum mechanics.

01:52:32.940 | It's just kind of a totally fascinating, romantic,

01:52:36.620 | great story, and those were very inspirational to me.

01:52:40.020 | And I would think maybe that other people

01:52:41.820 | might also find them.

01:52:44.240 | But the--

01:52:45.080 | - And that's almost like the human story

01:52:47.220 | of the development of the ideas.

01:52:49.100 | - Yeah, the human story.

01:52:50.100 | But yeah, just also how, you know,

01:52:51.820 | they have these very, very weird ideas

01:52:53.780 | that didn't seem to make sense,

01:52:54.980 | how they were struggling with them,

01:52:56.300 | and how, you know, they actually, anyway.

01:52:58.860 | It's, I think it's the period of physics kind of beginning,

01:53:03.700 | you know, in 1905, with Planck and Einstein,

01:53:06.060 | and ending up with the war when these things are,

01:53:09.900 | get used to, you know, make massively destructive weapons.

01:53:14.060 | It's just that totally amazing.

01:53:15.740 | - So many, so many new ideas.

01:53:17.580 | Let me, on another, a tangent on top of a tangent

01:53:19.780 | on top of a tangent, ask, if we didn't have Einstein,

01:53:24.780 | so how does science progress?

01:53:26.700 | Is it the lone geniuses, or is it some kind of weird

01:53:31.700 | network of ideas swimming in the air,

01:53:33.820 | and just kind of the geniuses pop up to catch them,

01:53:37.740 | and others would anyway?

01:53:39.220 | Without Einstein, would we have special relativity,

01:53:42.540 | general relativity?

01:53:43.700 | - I mean, it's an interesting, on a case-to-case basis,

01:53:47.220 | I mean, special relativity, I think we would have had,

01:53:51.820 | I mean, there are other people, anyway,

01:53:54.820 | you could even argue that it was already there

01:53:56.700 | in some form, in some ways, but I think special relativity

01:53:59.420 | you would have had without Einstein fairly quickly.

01:54:03.300 | General relativity, that was a much, much harder thing

01:54:07.180 | to do, and required much more effort,

01:54:10.900 | and much more sophisticated.

01:54:11.740 | That, I think you would have had sooner or later,

01:54:13.960 | but it would have taken quite a bit longer.

01:54:16.820 | - Other thing-- - That took a bunch

01:54:17.940 | of years to validate scientifically, the general relativity.

01:54:21.700 | - But even for Einstein, from the point where he had

01:54:24.540 | kind of a general idea of what he was trying to do,

01:54:26.820 | to the point where he actually had a well-defined theory

01:54:29.900 | that you could actually compare to the real world,

01:54:31.820 | that was, I forget the number, but the order of magnitude,

01:54:35.340 | 10 years of very serious work, and if he hadn't been around

01:54:39.180 | to do that, it would have taken a while

01:54:40.580 | before anyone else got around to it.

01:54:43.060 | On the other hand, there are things like,

01:54:45.020 | with quantum mechanics, you have Heisenberg

01:54:48.820 | and Schrodinger came up with two,

01:54:52.560 | which ultimately equivalent, but two different approaches

01:54:57.240 | to it within months of each other.

01:54:59.620 | And so if Heisenberg hadn't been there,

01:55:02.380 | you already would have had Schrodinger or whatever,

01:55:03.980 | and if neither of them had been there,

01:55:05.180 | it would have been somebody else a few months later.

01:55:07.580 | So there are times when the, just the,

01:55:12.420 | a lot often is the combination of the right ideas

01:55:16.520 | are in place and the right experimental data is in place

01:55:19.580 | to point in the right direction,

01:55:20.740 | and it's just waiting for somebody who's gonna find it.

01:55:24.100 | Maybe to go back to your aliens,

01:55:28.340 | I guess the one thing I often wonder about aliens is,

01:55:30.740 | would they have the same fundamental physics ideas

01:55:33.620 | as we have in mathematics?

01:55:35.580 | Would their math, would they,

01:55:37.500 | how much is this really intrinsic to our minds?

01:55:42.100 | If you start out with a different kind of mind,

01:55:43.780 | wouldn't you end up with a different ideas

01:55:46.140 | of what fundamental physics is

01:55:47.340 | or what the structure of mathematics is?

01:55:49.860 | - So this is why, if I was,

01:55:52.400 | I like video games.

01:55:55.260 | The way I would do it as a curious being,

01:55:57.740 | so first experiment I'd like to do is run Earth

01:56:00.380 | over many thousands of times and see if our particular,

01:56:04.440 | no, you know what?

01:56:06.700 | I wouldn't do the full evolution.

01:56:08.140 | I would start at Homo sapiens first

01:56:10.260 | and then see the evolution of Homo sapiens millions of times

01:56:13.860 | and see how the ideas of science would evolve.

01:56:16.540 | Like, would you get, like how would physics evolve?

01:56:19.740 | How would math evolve?

01:56:21.380 | I would particularly just be curious

01:56:22.740 | about the notation they come up with.

01:56:24.800 | Every once in a while, I would like throw miracles at them

01:56:28.820 | to mess with them and stuff.

01:56:31.220 | And then I would also like to run Earth

01:56:33.300 | from the very beginning to see if evolution

01:56:35.500 | will produce different kinds of brains

01:56:37.260 | that would then produce different kinds

01:56:38.840 | of mathematics and physics.

01:56:40.180 | And then finally, I would probably millions of times

01:56:43.500 | run the universe over to see what kind of,

01:56:47.000 | what kind of environments and what kind of life

01:56:52.300 | would be created to then lead to intelligent life,

01:56:55.420 | to then lead to theories of mathematics and physics

01:56:59.140 | and to see the full range.

01:57:00.880 | And like sort of like Darwin kind of mark,

01:57:04.080 | okay, it took them, what is it?

01:57:08.900 | Several hundred million years to come up with calculus.

01:57:13.900 | I would just like keep noting how long it took

01:57:16.060 | and get an average and see which ideas are difficult,

01:57:19.060 | which are not, and then conclusively sort of figure out

01:57:23.460 | if it's more collective intelligence

01:57:27.380 | or singular intelligence that's responsible for shifts

01:57:30.220 | and for big phase shifts and breakthroughs in science.

01:57:33.860 | If I was playing a video game and ran the thing,

01:57:36.340 | I got a chance to run this whole thing.

01:57:38.280 | - Yeah, but--

01:57:40.160 | - We're talking about books before I distract us.

01:57:42.520 | - Books, okay, so books, yeah, go back, books.

01:57:44.440 | Yeah, so, and then, yeah, so that's one thing I'd recommend

01:57:47.200 | is the books about the, from the original people,

01:57:50.700 | especially Heisenberg about the, how that happened.

01:57:53.680 | And there's also a very, very good kind of history

01:57:55.760 | of the kind of what happened during this 20th century

01:58:00.520 | in physics and up to the time of the Standard Model in 1973,

01:58:05.320 | it's called "The Second Creation" by Bob Crease and Mann.

01:58:10.320 | That's one of the best ones, I know that's,

01:58:12.900 | but the one thing that I can say is that,

01:58:14.760 | so that book, I think, forget when it was,

01:58:17.060 | late '80s, '90s, the problem is that there just hasn't been

01:58:21.840 | much that's actually worked out since then.

01:58:24.060 | So most of the books that are kind of trying to tell you

01:58:26.680 | about all the glorious things that have happened since 1973

01:58:30.300 | are, they're mostly telling you about how glorious things

01:58:33.720 | are, which actually don't really work.

01:58:35.260 | And it's really, the argument people sometimes make

01:58:38.600 | in favor of these books as well, oh, you know,

01:58:40.640 | they're really great because you want to do something

01:58:42.440 | that will get kids excited.

01:58:43.780 | And then, you know, so they're getting excited

01:58:45.360 | about things, something that's not really quite working.

01:58:47.680 | It's, doesn't really matter.

01:58:48.720 | The main thing is get them excited.

01:58:50.720 | The other argument is, you know, wait a minute,

01:58:53.600 | if you're getting people excited about ideas that are wrong,

01:58:56.720 | you're really kind of, you're actually kind of discrediting

01:58:59.000 | the whole scientific enterprise in a not really good way.

01:59:02.200 | So there's, there's problems.

01:59:04.640 | So my general feeling about expository stuff is, yeah,

01:59:07.920 | it's to the extent you can do it kind of honestly

01:59:10.680 | and well, that's great.

01:59:12.760 | There are a lot of people doing that now,

01:59:14.720 | but to the extent that you're just trying to get people

01:59:19.040 | excited and enthusiastic by kind of telling them stuff,

01:59:22.920 | which isn't really true, this is,

01:59:24.400 | you really shouldn't be doing that.

01:59:26.520 | - You obviously have a much better intuition about physics.

01:59:28.920 | I tend to, in the space of AI, for example,

01:59:32.640 | you could use certain kinds of language,

01:59:37.600 | like calling things intelligent,

01:59:41.280 | that could rub people the wrong way.

01:59:43.320 | But I never had a problem with that kind of thing.

01:59:45.680 | You know, saying that a program can learn its way

01:59:48.320 | without any human supervision as AlphaZero does

01:59:52.160 | to play chess.

01:59:53.680 | To me, that may not be intelligence,

01:59:57.800 | but it sure as heck seems like a few steps down the path

02:00:02.760 | towards intelligence.

02:00:04.480 | And so like, I think that's a very peculiar property

02:00:09.080 | of systems that can be engineered.

02:00:10.840 | So even if the idea is fuzzy,

02:00:12.480 | even if you're not really sure what intelligence is,

02:00:15.160 | or like if you don't have a deep fundamental understanding

02:00:19.500 | or even a model of what intelligence is,

02:00:21.600 | if you build a system that sure as heck is impressive

02:00:24.520 | and showing some of the signs

02:00:26.760 | of what previously thought impossible

02:00:29.720 | for a non-intelligent system,

02:00:32.960 | then that's impressive and that's inspiring

02:00:34.880 | and that's okay to celebrate.

02:00:36.680 | In physics, because you're not engineering anything,

02:00:39.880 | you're just now swimming in the space,

02:00:41.800 | directly when you do theoretical physics,

02:00:43.960 | that it could be more dangerous.

02:00:45.440 | You could be out too far away from shore.

02:00:48.720 | - Yeah, well the problem, I think physics is,

02:00:52.840 | I think it's actually hard for people,

02:00:54.400 | even to believe or really understand

02:00:57.080 | how that this particular kind of physics

02:01:00.560 | has gotten itself into a really unusual and strange

02:01:03.640 | and historically unusual state, which is not really,

02:01:06.680 | I mean, I spent half my life among mathematicians

02:01:09.480 | and half among physicists,

02:01:10.640 | and you know, mathematics is kind of doing fine.

02:01:12.880 | People are making progress

02:01:14.160 | and it has all the usual problems,

02:01:16.120 | but also so you could have a,

02:01:19.360 | but I just, I don't know,

02:01:21.080 | I've never seen anything at all happening in mathematics

02:01:23.800 | like what's happened in this specific area in physics.

02:01:26.360 | It's just the kind of sociology of this,

02:01:29.840 | the way this field works,

02:01:32.920 | banging up against this hard a problem

02:01:35.360 | without anything from experiment to help it.

02:01:38.560 | It's really, it's led to some really

02:01:41.640 | kind of problematic things.

02:01:43.320 | And those, so it's one thing to kind of, you know,

02:01:47.080 | oversimplify or to slightly misrepresent,

02:01:49.720 | to try to explain things in a way that's not quite right.

02:01:52.400 | But it's another thing to start promoting to people

02:01:55.800 | as a success as ideas, which really completely failed.

02:02:00.280 | And so, I mean, I've kind of a very, very specific,

02:02:03.600 | if you start to have people,

02:02:05.160 | won't name any names, for instance,

02:02:07.880 | coming on certain podcasts like yours,

02:02:09.480 | telling the world, you know, this is a huge success

02:02:12.560 | and this is really wonderful, and it's just not true.

02:02:16.520 | And this is really problematic

02:02:19.640 | and it carries a serious danger of, you know,

02:02:22.920 | once when people realize that this is what's going on,

02:02:27.040 | you know, the loss of credibility of science

02:02:32.040 | is a real, real problem for our society.

02:02:34.760 | And you don't want people to have an all too good reason

02:02:39.760 | to think that what they're being told

02:02:44.440 | by kind of some of the best institutions

02:02:46.880 | in our country and our authorities is not true.

02:02:49.160 | It's a problem.

02:02:52.320 | - That's obviously a characteristic of not just physics,

02:02:55.880 | it's sociology.

02:02:58.960 | And it's, I mean, obviously in the space of politics,

02:03:02.960 | it's the history of politics is you sell ideas to people

02:03:07.960 | even when you don't have any proof

02:03:14.080 | that those ideas actually work.

02:03:15.600 | You speak as if they've worked

02:03:17.760 | and that that seems to be the case throughout history.

02:03:20.560 | And just like you said, it's human beings

02:03:26.080 | running up against a really hard problem.

02:03:28.520 | I'm not sure if this is like a particular, like,

02:03:34.440 | trajectory through the progress of physics

02:03:37.040 | that we're dealing with now

02:03:38.400 | or is this just a natural progress of science?

02:03:40.240 | You run up against a really difficult stage of a field

02:03:44.800 | and different people behave differently

02:03:49.800 | in the face of that.

02:03:53.080 | Some sell books and sort of tell narratives

02:03:56.160 | that are beautiful and so on.

02:03:57.840 | They're not necessarily grounded in solutions

02:04:01.000 | that have proven themselves.

02:04:02.720 | Others kind of put their head down quietly,

02:04:05.480 | keep doing the work.

02:04:06.320 | Others sort of pivot to different fields.

02:04:08.200 | And that's kind of like, yeah, ants scattering.

02:04:11.600 | And then you have fields like machine learning,

02:04:14.520 | which there's a few folks mostly scattered away

02:04:17.080 | from machine learning in the '90s

02:04:19.560 | in the winter of AI, AI winter, as they call it.

02:04:23.000 | But a few people kept their head down

02:04:24.760 | and now they're called the fathers of deep learning.

02:04:27.320 | - Yeah, yeah.

02:04:28.160 | - And they didn't think of it that way.

02:04:30.240 | And in fact, if there's another AI winter,

02:04:33.320 | they'll just probably keep working on it anyway,

02:04:35.560 | sort of like loyal ants to a particular--

02:04:39.280 | - Sure, yeah, yeah.

02:04:40.400 | - So it's interesting, but you're sort of saying

02:04:43.120 | that we should be careful over hyping things

02:04:46.640 | that have not proven themselves

02:04:48.360 | because people will lose trust in the scientific process.

02:04:53.360 | But unfortunately, there's been other ways

02:04:57.800 | in which people have lost trust in the scientific process.

02:05:00.760 | That ultimately has to do actually

02:05:02.200 | with all the same kind of behaviors you're highlighting,

02:05:05.100 | which is not being honest and transparent

02:05:08.360 | about the flaws of mistakes of the past.

02:05:11.600 | - Yeah, I mean, that's always a problem.

02:05:13.120 | But this particular field is kind of fun.

02:05:15.720 | It's always a strange one.

02:05:18.840 | I mean, I think in the sense that

02:05:20.520 | there's a lot of public fascination with it

02:05:23.280 | that it seems to speak to kind of our deepest questions

02:05:25.840 | about what is this physical reality,

02:05:28.520 | where do we come from, and these kind of deep issues.

02:05:31.320 | So there's this unusual fascination with it.

02:05:33.960 | Mathematics, for instance, is very different.

02:05:35.880 | Nobody's that interested in mathematics.

02:05:37.560 | Nobody really kind of expects to learn really great,

02:05:41.560 | deep things about the world from mathematics that much.

02:05:43.600 | They don't ask mathematicians that.

02:05:45.400 | So it's a very unusual,

02:05:47.720 | it draws this kind of unusual amount of attention.

02:05:51.160 | And it really is historically in a really unusual state.

02:05:54.920 | It's kind of, it's gotten itself way kind of down

02:05:58.680 | a blind alley in a way which,

02:06:03.640 | it's hard to find other historical parallels to.

02:06:06.560 | - But sort of to push back a little bit,

02:06:08.480 | there's power to inspiring people.

02:06:10.720 | And if I just empirically look,

02:06:13.240 | physicists are really good

02:06:18.000 | at combining science and philosophy and communicating it.

02:06:23.000 | Like there's something about physics often

02:06:26.240 | that forces you to build a strong intuition

02:06:28.960 | about the way reality works, right?

02:06:31.320 | And that allows you to think through

02:06:33.920 | sort of and communicate about all kinds of questions.

02:06:37.360 | Like if you see physicists, it's always fascinating

02:06:40.000 | to take on problems that have nothing to do

02:06:42.080 | with their particular discipline.

02:06:43.520 | They think in interesting ways

02:06:45.960 | and are able to communicate their thinking

02:06:47.680 | in interesting ways.

02:06:48.680 | And so in some sense, they have a responsibility

02:06:52.200 | not just to do science, but to inspire.

02:06:54.800 | And not responsibility, but the opportunity.

02:06:58.080 | And thereby I would say a little bit of a responsibility.

02:07:02.680 | - Yeah, yeah, and sometimes, but I don't know.

02:07:05.000 | Anyway, it's hard to say 'cause different,

02:07:07.920 | there's many, many people doing this kind of thing

02:07:10.680 | with different degrees of success and whatever.

02:07:15.600 | I guess one thing,

02:07:16.520 | but I mean, what's kind of front and center for me

02:07:21.200 | is kind of a more parochial interest,

02:07:22.920 | is just kind of what damage do you do to the subject itself?

02:07:27.920 | Ignoring, misrepresenting,

02:07:32.360 | what high school students think about string theory

02:07:34.320 | and not that it doesn't matter much,

02:07:36.560 | but what the smartest undergraduates

02:07:40.280 | or the smartest graduate students in the world

02:07:42.160 | think about it and what paths you're leading them down

02:07:45.200 | and what story you're telling them

02:07:47.120 | and what textbooks you're making them read

02:07:49.680 | and what they're hearing.

02:07:50.880 | And so a lot of what's motivated me

02:07:53.080 | is more to try to speak to kind of a specific population

02:07:57.440 | of people to make sure that, look, people,

02:08:01.720 | it doesn't matter so much what the rest,

02:08:04.160 | what the average person on the street

02:08:06.040 | thinks about string theory,

02:08:07.040 | but what the best students at Columbia or Harvard

02:08:12.040 | or Princeton or whatever who really wanna change,

02:08:14.960 | work in this field and wanna work that way,

02:08:16.720 | what they know about it, what they think about it,

02:08:19.400 | and that they not be going to the field being misled

02:08:22.120 | and believing that a certain story,

02:08:23.880 | this is where this is all going, this is what I gotta do,

02:08:27.160 | is what's important to me.

02:08:29.120 | - Well, in general, for graduate students,

02:08:31.480 | for people who seek to be experts in the field,

02:08:34.280 | diversity of ideas is really powerful.

02:08:36.560 | And is getting into this local pocket of ideas

02:08:40.760 | that people hold onto for several decades is not good,

02:08:43.920 | no matter what the idea.

02:08:44.940 | I would say no matter if the idea is right or wrong,

02:08:47.920 | because there's no such thing as right in the long-term.

02:08:51.600 | Like it's right for now until somebody builds on

02:08:56.440 | something much bigger on top of it.

02:08:58.160 | It might end up being right,

02:09:00.120 | but being a tiny subset of a much bigger thing.

02:09:03.600 | So you always should question sort of the ways of the past.

02:09:07.520 | - Yeah, yeah.

02:09:08.440 | So how to kind of achieve that kind of diversity of thought

02:09:12.760 | and within kind of the sociology

02:09:15.120 | of how we organize scientific research is,

02:09:17.720 | I know this is one thing that I think it's very interesting

02:09:19.560 | that Sabina Hassenfelder has very interesting things

02:09:22.760 | to say about it.

02:09:23.600 | And I think also at least Smolin in his book,

02:09:25.600 | which is also about that,

02:09:27.040 | very much in agreement with them that there's,

02:09:30.800 | anyway, there's a really kind of important questions

02:09:36.800 | about how research in this field is organized

02:09:41.480 | and how people, what can you do to kind of get

02:09:45.240 | and get more diversity of thought and get more,

02:09:47.200 | and get people thinking about a wider range of ideas.

02:09:53.160 | At the bottom, I think humility always helps.

02:09:56.040 | (Lex laughing)

02:09:57.280 | - Well, the problem is that it's also,

02:09:59.880 | it's a combination of humility to know when you're wrong

02:10:02.760 | and also, but also you have to have a,

02:10:05.600 | you have to have a certain, very serious lack of humility

02:10:08.160 | to believe that you're gonna make progress

02:10:09.680 | on some of these problems.

02:10:11.160 | - I think you have to have like both modes

02:10:13.240 | and switch between them when needed.

02:10:15.600 | Let me ask you a question

02:10:19.440 | you're probably not gonna wanna answer

02:10:21.240 | because you're focused on the mathematics of things

02:10:25.480 | and mathematics can't answer the why questions,

02:10:27.720 | but let me ask you anyway,

02:10:30.640 | do you think there's meaning to this whole thing?

02:10:33.400 | What do you think is the meaning of life?

02:10:35.000 | Why are we here?

02:10:36.880 | - I don't know.

02:10:37.720 | Yeah, I was thinking about this.

02:10:39.600 | So the, it did occur to me,

02:10:42.280 | one interesting thing about that question

02:10:45.640 | is that you don't,

02:10:47.200 | yes, I have this life in mathematics

02:10:51.040 | and this life in physics

02:10:52.040 | and I see some of my physicist colleagues,

02:10:55.880 | kind of seem to be,

02:10:58.640 | people are often asking them,

02:10:59.760 | what's the meaning of life?

02:11:00.600 | And they're writing books about the meaning of life

02:11:02.280 | and teaching courses about the meaning of life.

02:11:04.600 | But then I realized that no one ever asked

02:11:06.480 | my mathematician colleagues.

02:11:07.920 | (both laughing)

02:11:08.960 | Nobody ever asked mathematicians.

02:11:10.640 | - Yeah, that's funny.

02:11:11.480 | - So I, yeah.

02:11:13.760 | Everybody just kind of assumes,

02:11:15.040 | okay, well, you people are studying mathematics.

02:11:16.640 | Whatever you're doing, it's maybe very interesting,

02:11:19.360 | but it's clearly not gonna tell you anything useful

02:11:21.160 | about the meaning of my life.

02:11:22.480 | And I'm afraid a lot of my point of view

02:11:24.840 | is that if people realized how little difference there was

02:11:28.160 | between what the mathematicians are doing

02:11:29.680 | and what a lot of these theoretical physicists are doing,

02:11:31.480 | they would, they might understand that

02:11:34.120 | it's a bit misguided to look for deep insight

02:11:38.160 | into the meaning of life from many theoretical physicists.

02:11:42.520 | It's not a, they, you know,

02:11:44.320 | there are people and they may have interesting things

02:11:46.520 | to say about this.

02:11:47.360 | You're right.

02:11:48.200 | They know a lot about physical reality

02:11:50.160 | and about, in some sense, about metaphysics,

02:11:53.920 | about what is real of this kind.

02:11:56.760 | But you're also, to my mind,

02:12:01.760 | I think you're also making a bit of a mistake

02:12:03.760 | that you're looking to, I mean, I'm very, very aware

02:12:07.920 | that I've led a very pleasant

02:12:10.600 | and fairly privileged existence

02:12:12.000 | and were fairly without many challenges of different kinds

02:12:15.240 | and of a certain kind.

02:12:16.680 | And I'm really not, in no way, the kind of person

02:12:21.440 | that a lot of people who are looking for,

02:12:24.200 | to try to understand, in some sense, the meaning of life

02:12:27.400 | in the sense of the challenges that they're facing in life.

02:12:30.280 | I can't really, I'm really the wrong person

02:12:32.640 | for you to be asking about this.

02:12:33.960 | - Well, if struggle is somehow a thing

02:12:37.860 | that's core to meaning,

02:12:39.640 | perhaps mathematicians are just quietly the ones

02:12:42.440 | who are most equipped to answer that question

02:12:45.100 | if, in fact, the creation, or at least experiencing beauty,

02:12:50.040 | is at the core of the meaning of life.

02:12:55.800 | Because it seems like mathematics is the methodology

02:12:59.360 | by which you can most purely explore beautiful things, right?

02:13:04.040 | - Yeah, mm-hmm.

02:13:05.240 | - So in some sense,

02:13:06.200 | maybe we should talk to mathematicians more.

02:13:08.880 | - Yeah, yeah, maybe.

02:13:10.560 | But unfortunately, I think people do have

02:13:13.440 | a somewhat correct perception

02:13:14.860 | that what these people are doing every day,

02:13:17.040 | or whatever, is pretty far removed from anything.

02:13:19.680 | Yeah, from what's kind of close to what I do every day

02:13:26.080 | and what my typical concerns are.

02:13:28.000 | So you may learn something very interesting

02:13:29.720 | by talking to mathematicians,

02:13:31.020 | but it's probably not gonna be,

02:13:33.840 | you're probably not gonna get what you were hoping.

02:13:37.080 | - So when you put the pen and paper down,

02:13:39.520 | and you're not thinking about physics,

02:13:41.440 | and you're not thinking about mathematics,

02:13:43.320 | and you just get to breathe in the air,

02:13:45.480 | and look around you,

02:13:46.840 | and realize that you're going to die one day.

02:13:49.240 | - Yeah, mm-hmm. - Do you think about that?

02:13:51.440 | Your ideas will live on, but you, the human.

02:13:56.960 | - Not especially much,

02:13:58.320 | but certainly I've been getting older.

02:14:00.160 | I'm now 64 years old.

02:14:01.900 | You start to realize, well,

02:14:02.740 | there's probably less ahead than there was behind.

02:14:05.680 | And so you start to, that starts to become,

02:14:09.480 | "Wait a minute, what do I think about that?

02:14:10.440 | Maybe I should actually get serious

02:14:13.400 | about getting some things done,

02:14:14.720 | which I may not have,

02:14:17.000 | which I may otherwise not have time to do,

02:14:18.720 | which I didn't see,

02:14:20.320 | and this didn't seem to be a problem when I was younger."

02:14:22.200 | But that's the main,

02:14:24.080 | I think the main way in which that thought occurred.

02:14:26.840 | - But it doesn't, you know,

02:14:28.640 | the Stoics are big on this, meditating on mortality.

02:14:32.080 | Helps you more intensely appreciate the beauty

02:14:36.560 | when you do experience it.

02:14:39.720 | - I suppose that's true, but it's not, yeah,

02:14:41.600 | it's not something I spend a lot of time trying,

02:14:45.920 | but yeah.

02:14:47.200 | - Day to day, you just enjoy the puzzles, the mathematics.

02:14:49.840 | - Just enjoy, yeah, or life in general.

02:14:52.480 | Life is, I have a perfectly pleasant life

02:14:55.760 | and enjoy it and often think,

02:14:59.080 | "Wow, this is, I think things are,

02:15:01.680 | I'm really enjoying this, things are going well."

02:15:04.360 | - Yeah, life is pretty amazing.

02:15:06.560 | I think you and I are pretty lucky.

02:15:08.200 | We get to live on this nice little earth

02:15:10.760 | with a nice little comfortable climate

02:15:13.360 | and we get to have this nice little podcast conversation.

02:15:17.160 | Thank you so much for spending your valuable time

02:15:19.120 | with me today and having this conversation.

02:15:21.200 | Thank you.

02:15:22.040 | - Thank you.

02:15:22.880 | - Thank you.

02:15:23.700 | - Thanks for listening to this conversation

02:15:26.680 | with Peter White.

02:15:27.960 | To support this podcast,

02:15:29.240 | please check out our sponsors in the description.

02:15:32.080 | And now let me leave you with some words

02:15:34.080 | from Richard Feynman.

02:15:36.120 | The first principle is that you must not fool yourself

02:15:40.200 | and you are the easiest person to fool.

02:15:43.080 | Thank you for listening and hope to see you next time.

02:15:47.160 | (upbeat music)

02:15:49.740 | (upbeat music)

02:15:52.320 | [BLANK_AUDIO]

Peter Woit: Theories of Everything & Why String Theory is Not Even Wrong | Lex Fridman Podcast #246

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