Difference between revisions of "20: Sir Roger Penrose - Plotting the Twist of Einstein’s Legacy"

[[Sir Roger Penrose]] is arguably the most important living descendant of [[Albert Einstein]]’s school of geometric physics. In this episode of [[The Portal Podcast|The Portal]], we avoid the usual questions put to Roger about quantum foundations and quantum consciousness. Instead we go back to ask about the current status of his thinking on what would have been called “Unified Field Theory” before it fell out of fashion a couple of generations ago. In particular, Roger is the dean of one of the only rival schools of thought to have survived the “String Theory wars” of the 1980s-2000s. We discuss his view of this [https://en.wikipedia.org/wiki/Twistor_theory Twistor Theory] and its prospects for unification. Instead of spoon feeding the audience, however, the material is presented as it might occur between colleagues in neighboring fields so that the Portal audience might glimpse something closer to scientific communication rather than made for TV performance pedagogy. We hope you enjoy our conversation with Professor Penrose.

The second piece of housekeeping surrounds today's episode with Roger Penrose. Now, I know what I'm supposed to do. I'm supposed to talk about quantum consciousness and The Emperor's New Mind, maybe ask Roger about the many-worlds interpretation of Quantum Mechanics, or the weirdness of quantum entanglement. I'm actually not that interested. I also don't want to go back to his earliest work on singularities and General Relativity with Stephen Hawking.

What I instead want to do is to remind you of what Roger is in fact famous for. He is one of the greatest geometric physicists now living. He's perhaps the best descendant of Albert Einstein currently still working in Theoretical Physics in this particular line of thought. I also think he's a great example of what the UK does well: he has a very idiosyncratic approach to trying to solve the deepest problems in Theoretical Physics called Twistor Theory. I'm not expert in it, and I can't always follow it, so if you're not following everything in today's episode, instead of deciding that the episode has somehow failed you, try to remember that people who are working in Mathematics and Theoretical Physics spend most of their time listening to colleagues completely lost as to what their colleagues are saying. So, if you start to feel that you're being left behind by some line of thinking, what we do is, in general, wait to see if another line of thinking opens up that we can try to catch. You're not going to get all of the waves, and in fact the same thing is happening to me while I'm interviewing Roger. He's not understanding everything I'm saying. I'm not understanding everything he's saying. And in fact, this is normal.  

You know, there's a Leonard Cohen quote, from a song called The Future where he says, "You don't know me from the wind, you never will, you never did. But I'm the little Jew that wrote the Bible." And I have what I consider to be the bible right here, which is a book you wrote called The Road to Reality which, there's no getting away from, may be, in my opinion, the most important modern book of our time, because what it tries to do is to summarize what we know about the nature of all of this at the deepest level. And I think what I want to do is to introduce you to our audience, which has been habituated, over perhaps 16 or so interviews, not to expect to understand everything. They want to work, they want to hear conversations unlike any they've heard, and so we'll do some combination of explaining things, but [also] some combination of allowing them to look up things in their own free time, if you're game. Should we talk about The Road to Reality?

'''Sir Roger Penrose:''' You see, I have a proposal, which I didn't have—I mean, it's new since the book. It's not all that new because it's about 15 years old, but it's new since I wrote that book.

'''Eric Weinstein:''' Okay, you got a chance to live through, if not the original General Relativistic and Quantum revolutions, their consequences. In particular, you were able to take classes from people like Paul Dirac, who scarcely seems like a human being, sometimes more like a god.

'''Sir Roger Penrose:''' Oh yeah, that was an experience. Yes. When I was at Cambridge as a graduate student—You see I did my undergraduate work at London University, University College. And then I went to Cambridge as [a] graduate student, and I went to do Algebraic Geometry, so I wasn't trying to do Physics at all. And I, I'd encountered a friend of my brother's, Dennis Sciama, when I think I was at University College as an undergraduate. And he had given a series of talks on Cosmology—well it started with the Earth, and then he sort of worked his way out, and then talked about what was then referred to as the Steady-state Theory. Where the galaxies—the universe expands and expands and expands, but it doesn't change, because all the time there is new matter created—hydrogen—and the universe expands and then you get new material, and it keeps replenishing what gets lost.  

And I thought it was quite an intriguing, I mean, Dennis was a great fan of this model, and so I was really taken by it. So that, well the story was that I was in Cambridge visiting my brother, my older brother Oliver, who did Statistical Mechanics. And he was actually much more precocious than I was, he was two years ahead. And he was, I think, finishing his research there. But I had been listening to these talks by Fred Hoyle, and he was talking, I think in his last talk, about how in the Steady-state Model, the galaxies expanded away, expanded away, and then when they reach the speed of light, they disappear. And I thought that can't be quite right, and I started drawing pictures with light cones and things like this. And I thought, well, they would fade, gradually fade, but they wouldn't just disappear.  

'''Eric Weinstein:''' So you were simultaneously under the great geometer Hodge, as well as Dennis Sciama?

'''Sir Roger Penrose:''' Hodge was my supervisor, originally, until he threw me out, and Todd became my supervisor. That's another little story. But Dennis just wanted to get me interested, and do working Cosmology. This was it. I never, he wanted me to change my subject. I learned an awful lot from Dennis about Physics, because Dennis sort of knew everything and everybody. And he had a real knack of getting, if he thought two people should meet each other, he got, made sure they did meet each other. In one case, it was Stephen Hawking. But, Dennis was actually—well you mentioned Dirac—Dennis was actually the last graduate, at the time he was the only graduate student of Dirac's.  

'''Eric Weinstein:''' Dirac was famously sort of difficult. I think that, you know, in recent years, this book came out of Graham Farmelo, The Strangest Man, that puts Dirac's bizarreness, in line with—  

'''Eric Weinstein:''' Well his, and this gets to a very odd issue, which is that you have wielded taste and beauty as a weapon your entire life. Your drawings are among the most compelling—I remember the first time—one of the things I've done, using our friend Joe Rogan's program, is to push out discussion of the Hopf fibration, because it's the only non-trivial principal bundle that can be visually seen. And since the world seems to be about principal bundles, it's a bit odd that the general population doesn't know that stuff of which we are.

'''Sir Roger Penrose:''' Yes. Well the, the Hopf fibration, or the Clifford parallels, was instrumental in the subject of Twistor Theory.

'''Sir Roger Penrose:''' Well, when I went to the... you see Dirac gave a course of lectures in Quantum Mechanics, and the first course was sort of basic Quantum Mechanics. And the second course was on Quantum Field Theory, but also spinors. And there's an interesting story about that, which I don't know the answer to. In the second course, he deviated from his normal course of lectures. Now, I understood when I talked to Graham Farmelo, who wrote this biography of Dirac, I understood from Graham Farmelo that, when I described that Dirac deviated from his normal course to give two or three lectures on two-component spinors, which for me were absolutely what I needed. You see, I'd learned from my work on Algebraic Geometry, which ended up by trying to understand tensor systems as abstract systems, and things which you can't represent in terms of components.

'''Eric Weinstein:''' Spinors in general. I mean, he brought them into Physics, they'd been previously found inside of Mathematics, I think by people like Killing and Lie, I'm not sure who.

'''Sir Roger Penrose:''' Cartan is the one.

'''Eric Weinstein:''' But that, you know, I asked you before about your favorite film, you said 2001. You could make an argument that spinors are, in Mathematics and Physics, like the monolith. It's always encountered, nobody ever understands exactly what it means, but it always grabs your attention, because it seems so absolutely bizarre and highly conserved.

'''Eric Weinstein:''' Well that won't make any sense to anyone. But if—I mean one way of looking at that is if you have a Klein bottle—

'''Eric Weinstein:''' And for those of—some people will be listening to this on audio, some watching it in video. A Klein bottle, in a certain sense that can be made precise, has a square root that would be a torus: that is a double cover. So it seems like a very weird thing to take a square root of a strange topological mobius-like object, but there you are.  

'''Sir Roger Penrose:''' Well I think this was a mystery. I mean, I understood that a spinor was the square root of a vector, you see, and I couldn't make head or tail of that idea. And it was when I went to Dirac's course it did become clear. And he made, he gave this very impressive illustration, which I thought was due to Dirac, I learned later it was due to Hermann Weyl, that you imagine a cone, circular cone—  

'''Eric Weinstein:''' Well, I think with a, with a pulley system and a wheel, we don't have any trouble imagining a wheel that rotates twice as fast, half as fast, not at all hooked up to one particular crank wheel, right?  

'''Eric Weinstein:''' Have you seen this video called Air on the Dirac String, which illustrates this in video format?

'''Eric Weinstein:''' I would highly recommend it because it shows this off as the similarity to the belt trick, to the Philippine wineglass dance—  

'''Sir Roger Penrose:''' Yeah, I suppose the difference between the fermions and bosons, so the particles which have a spin which is half an odd number—

'''Sir Roger Penrose:''' Yeah, yeah. I mean, these ideas come back again in a different form, but certainly in the, I guess the 19th century, people were playing with, well, I guess you can go back further than that... Phlogiston.

'''Sir Roger Penrose:''' Well some people do. But the general public don't know about Maxwell. But Maxwell's equations completely change our way of looking at the world. And we live off it without thinking, you know, you've got these lights here. Well, these are visible lights, so we, we know, you knew about visible light, but we didn't know anything about x-rays. X-rays, radio waves, they're all part of the same scheme. Electromagnetism, dynam—well, some of this goes back to Faraday just before Maxwell.

'''Eric Weinstein:''' But even Max, you know, I'm very partial to this book on orchids that followed Darwin's Origin of Species.

'''Eric Weinstein:''' That was the book he wrote—the title is, and I always, I love reciting it, it's On the Various Contrivances by which British and Foreign Orchids are Fertilized by Insects. And so you think, well, why would you write a damn fool book like that after Origin of Species? And the answer is he wanted to test whether he understood his own theory. And in fact, it's revealed that he didn't understand the full implications. I would say that the same thing is true of Maxwell's equations, which is, this is perhaps the best dress rehearsal for unification we've ever seen, you know, full unification, and on the other hand, it's not until the late 50s that we actually unpack the last trivial consequence of the theory with this bizarre effect of passing an electron beam around an insulated wire.

'''Eric Weinstein:''' Yeah, in fact we had dinner last night, we asked Yakir Aharonov if he wanted to come but he's in Israel, and he sends his regards.  

'''Eric Weinstein:''' Well, you know, this etching called Ascending and Descending.

'''Sir Roger Penrose:''' You see when I was a graduate student in Cambridge, I think it was in my second year, when the International Congress of Mathematicians took place in Amsterdam. And so I and a few friends decided we would go to this meeting, and I remember... I think I was just about to get on the bus or tram or something, and Sean Wiley—who is a lecturer in in Algebraic Topology—he's just about to get off the bus, I was getting on, and he had this catalog in his hand of an exhibition in the Van Gogh Museum. And this was a picture... The one called Night and Day with birds flying off into the day and the night, and the birds changed into the spaces between the birds [unintelligible], and I just look at this and I think 'Oh that's amazing what is that? Where on earth did that come from?'  

So I played around with this. And then I sort of whittled it down to the triangle, which people refer to as a tribar. So it's a triangle which is locally a completely consistent picture, but as a whole, it's impossible. And I showed this to my father. And then he started drawing impossible buildings, and then he came up with this staircase. So we decided we'd like to write a paper together on this. And we had no idea what the subject was, I mean, what, who do you send a paper like this to, what journal? So he decided since he knew the editor of the British Journal of Psychology, and he thought he'd be able to get it through, we decided the subject was Psychology.  

'''Eric Weinstein:''' So you saw the movie Inception, of course, where they, they realized this actually?

'''Eric Weinstein:''' But that effect is the soul of the Aharonov-Bohm effect, which surprised the world in the late 50s because it was discovered so late into the game.

'''Sir Roger Penrose:''' It is a comm—same sort of thing. That's right. Well, of course like so many things, people point out that this Oscar Reutersvärd, who is a Swedish artist who'd drawn things like this before. I think roundabout the year I was born, he had a picture which is all, with cubes going around. It wasn't exactly the same, but it was.

'''Eric Weinstein:''' So, what I want to get at is, I think also that we have this very funny thing that happened, recently, starting from the early 70s, where we started mis-telling our own Physics history, because of the needs of the community to look like we were succeeding when we weren't, or we were succeeding at something different than we were trying to succeed at. And, in part, one of the reasons that I want to use this podcast to discuss science is to give alternate versions of what's happened. And I want to explore one or two of them with you. Now, you and I have a very funny relationship which, we don't really know each other. But you were quite close to Michael Atiyah at various points. And I was—

'''Eric Weinstein:''' In Geometry more generally, and Analysis, I mean, just incredible, and Algebra. I mean, he wrote a book on on Commutative Algebra. Now he had a partner for much of his career, Isadore Singer, who I was quite close to for a period of time. And Is was, again, another one of these figures that if I'd never met one, I wouldn't know that the human mind was capable of that level of repeated insight. And they came up with something called the Atiyah-Singer Index Theorem, which governs worlds in which there are no time dimensions, but only space dimensions, or no space dimensions and only time dimensions, but there's no—