Episode 28: Roger Penrose on Spacetime, Consciousness, and the Universe

0:00:01 Sean Carroll: Hello everyone and welcome to the Mindscape Podcast. I'm your host, Sean Carroll. I don't want to mess around a lot at the very beginning of this one, because you've probably heard of today's guest, who is Sir Roger Penrose. One of the most important and interesting thinkers and scientists of recent years of my lifetime. That's for sure. If you don't know Sir Roger Penrose as a physicist, you might know him as a writer of popular level books, The Road to Reality, The Emperor's New Mind and so forth. But he made his bones, as it were, in the field of General Relativity, Einstein's theory of gravity. Along with Stephen Hawking, he helped invent the singularity theorems. The idea that if you get enough stuff in a region of space, general relativity says you can't help but collapse into a point of infinite spacetime curvature. Sir Roger Penrose has done many other things in addition to that. Just as one example, early on in the podcast, he mentions doing some early work on the nature of infinity in spacetime and what he's really referring to is the idea of a Penrose diagram, which general relativists used to make a little picture of an entire spacetime. Roughly speaking, Penrose diagrams are as important for people in general relativity as Feynman diagrams are for people doing particle physics.

0:01:14 SC: And not only that, Roger Penrose has come up with the Penrose triangle, the Penrose process for extracting energy from black holes, Penrose tilings, Twistor Theory, the cosmic censorship hypothesis, many other extraordinarily influential ideas in general relativity. And he doesn't stop there with general relativity. As you do know, if you're a fan of Penrose, he's been working in recent years with ideas in quantum mechanics. He has his own, basically, idea about how wave functions collapse in quantum theory and the implications of those ideas for consciousness, and how that relates to Gödel's theorem and artificial intelligence, and all of these big picture of ideas. Now, in my mind, the thing about Roger Penrose is that he understands four-dimensional curved spacetime better than any person alive. So that's what I chose to talk about in our conversation mostly in this particular podcast. We do go on to other things. We talk about consciousness and quantum mechanics for the last half hour or so. We could have talked about those for hours more but we both had schedules to meet. Sorry about that.

0:02:19 SC: One thing I got to note is that we both got stuck on the names of the three people who were the authors on the papers on black hole, the Laws of Black Hole Mechanics. It's Jim Bardeen, whose name we forgot, sorry, Jim, who wrote papers with Stephen Hawking and Brandon Carter about that topic. Now, talking to Roger Penrose, the great thing about him is he's fearless. He has enormously creative deep ideas. Many of them have been incredibly successful and influential, many of them are idiosyncratic, many of them I don't agree with. I didn't agree with his ideas about entropy back when I was first learning cosmology. I later realized he was completely correct in his picture of entropy in the early universe and that had a huge impact on my career. So I'm always happy and respectful talking to Roger Penrose whether or not I agree with his ideas. You can decide whether or not you agree or disagree with any of them in particular. What the point of the podcast is, is to give you information about what the ideas are. You're the one who's gotta make the decision about what to think at the end of the day. So this is an extremely fun conversation. It's a great way to start off the year 2019.

0:03:23 SC: Let me just do two quick podcast announcements, of course. You can always support Mindscape on either Patreon or just directly through PayPal. Go to the webpage to find information about that. And like any podcaster, we love getting good reviews on iTunes and elsewhere. So, we have a wonderful list of guests coming up for the rest of 2019, but I can't think of a better place to start it off than talking with Sir Roger Penrose about the nature of spacetime, black holes, and cosmology. So, let's go.

[music]

0:04:13 SC: Roger Penrose, welcome to the Mindscape Podcast.

0:04:16 Roger Penrose: Hello, quite pleasant.

0:04:17 SC: Now you've not only done a lot of amazingly important scientific intellectual work, but on an amazing variety topics. And so, usually for the podcast, often for the podcast, I'd like to focus in on one. I have the feeling that my people will be upset if we don't hit all the various high points of cosmology, quantum mechanics, consciousness. So, we can spend three hours if you want, but I'm gonna try to get the main things in there. But I thought starting with spacetime would be a good thing to do. I mean, this is where you sort of made your bones early on. Is it safe to say the first big thing you published, the first major result, was the singularity theorem for black holes?

0:05:00 RP: I think that's true. I'm trying to remember the order of which things were done. I had two Phys. Rev. Letter articles and one was on conformal infinity, how one represents gravitational radiation by squashing infinity down to a place where you can see it more or less. And this is a nice way of talking about things like gravitational radiation and electromagnetic radiation, and so on. But then I wrote this article in 1965, written in '64, I think, which was about black holes, except we didn't call them that at that time. This was gravitational collapse. Going way back to work done by Chandrasekhar in the 1930s when he was on the boat coming to England. [chuckle] So, I think 19 or something, I can't remember and he worked hard. A white dwarf star would have a certain maximum mass and if it was more of than that then it would collapse basically.

0:06:09 SC: Right, the Chandrasekhar Limit.

0:06:11 RP: The Chandrasekhar Limit is what has worked out at that time. The white dwarf stars being very, very concentrated, so that the mass of the sun might be concentrated in something about the size of the Earth. But these stars are certainly known the companion of Sirius, another such stars. These are the things that were well-established. But what Chandrasekhar showed was if the mass was above a certain amount, which was a bit more than the mass of the sun, one and a half times the mass of the sun, then there was nothing would hold it apart, and it would collapse down. And the question is, what happens to it? And Chandra was very modest about this and less speculating on what happens. Whereas Eddington at the time was thinking, "This is ridiculous. That can't happen."

0:07:04 SC: Chandrasekhar got a lot of pushback, for this idea that there will be gravitational collapse?

0:07:08 RP: Yes, indeed. He got into a lot of trouble, 'cause, well, it's a wild idea. So I'm not surprised actually.

[laughter]

0:07:13 SC: Yeah, he should get a little pushback.

0:07:14 RP: Yes. But of course that didn't get down to a black hole. He just said, "One is left speculating." I suppose he had some sort of idea that it might. Well, a lot of early work which people say, there was this, I forget people's names right on the spur of the moment. Anyway, this early work when people wondered what happened to a very massive object. But until general relativity came along, it wasn't really an issue which was problematic. And it was in the 1939 when Oppenheimer, of atom bomb fame, and a student of his, Snyder, and they worked out an exact model according to Einstein's general theory of relativity of a collapsing dust cloud, and it was the picture of a black hole that we have now. But a lot of people were a bit suspicious of whether that was really what you'd expect because, well, there were two things. One is, the dust cloud was a material that had no pressure and so it wouldn't push itself apart at all and it would fall into the middle, and it wouldn't stop itself from pressure. The other point was, the model was exactly spherically symmetrical. It's exactly the same all the way around and so that the matter as it collapse inwards would be aimed right at the central point. And so, the fact that you got infinite density there was not perhaps surprising and people thought, "Well, maybe if it was irregular it would fall in and maybe swish around a bit, and then come swelling out."

0:08:53 SC: Right. So they thought this was an artifact, that it is maybe some special thing but it's not usually what you'd expect?

0:08:57 RP: That's right. Well, I think there was an argument about it. Now, I know John Wheeler was very worried about these things and the worry came particularly to a head when Maarten Schmidt, Dutch astronomer, well, Dutch-American astronomy and he concluded that this was the first quasar. And he noticed that the signals from this object, well, first of all, they were red shifted so that meant probably it was receding from us at a very great speed, and secondly, it was extremely bright. And thirdly, it had variations in its brightness of the order for a week or so, which suggested that it couldn't be much bigger than the solar system. And therefore, you had this huge amount of energy coming out which is something like more than the whole galaxy. And it was a real problem and the picture which was presented was that you had something which was down at the level that the, well, Oppenheimer and Snyder model would say, you have a horizon as a certain point and this would be where this energy would be released at that sort of scale.

0:10:12 SC: Sorry, this point about the variability is an important one. It's sort of not obvious to people, but it's a very simple fun argument.

0:10:17 RP: Yes. That's right.

0:10:19 SC: If something varies rapidly then it's probably not any bigger than it takes light to travel across the object?

0:10:27 RP: Exactly. That's right, yes.

0:10:27 SC: And so, week timescales, that's the size of the solar system, which is small by massive extragalactic object standards.

0:10:34 RP: That's right, yes. So it's a great puzzle and I know Wheeler was very worried about this. And he talked to me about it and he said, "Well, look this means we've got something down at what's called the Schwarzschild radius." This was a very early solution of Einstein's equation. It's called the Schwarzschild solution and Schwarzschild discovered it soon after general relativity. Unfortunately, he died not long after that, but it was the first solution of a represented body. He was thinking more in terms of a star or something, where there was something inside which was matter, and the equations changed when you get into the matter. And so, that there was no singularity there. But if you imagine squashing the matter down to this radius, which is called the Schwarzschild radius, then you get into a very curious situation, which was described by the Oppenheimer-Snyder collapse model.

0:11:32 SC: And then, so it took a long time, decades for people to really appreciate what the Schwarzschild solution was trying to tell them all along.

0:11:42 RP: Yes.

0:11:43 SC: It's a tricky little general relativity question.

0:11:45 RP: That's right, well usually people thought there was body inside. And so you didn't explore what happened when you extended the solution inwards. It was the first clear... I think the Oppenheimer-Snyder model just before the second World War was a first clear model of what could be happening.

0:12:02 SC: Right. And then the quasars that you mentioned, I mean, so there's a bright object in the sky, very far away, very small, seemingly this could be a candidate for an ultra compact object that might be what we now call a black hole. So is it really accurate to say that that experimental data, nudge us theorist towards trying to understand this.

0:12:22 RP: Oh absolutely true. Yes, it certainly nudged me into [chuckle] thinking about this.

0:12:25 SC: Yeah.

0:12:26 RP: I thought about the Schwarzschild Horizon and so on, and didn't think much of it as thing that might be out there. Usually one thought that if you squash the earth down or the sun down to that size, well it would be pretty unrealistic.

0:12:41 SC: Right.

0:12:41 RP: But if the thing is big enough and it collapses itself inwards, and I should say that the Schwarzschild Horizon, the size of it, the diameter of it is proportional to the mass of the object so that if the object is much, much bigger than the volume which goes as the mass cubed is something which you wouldn't, the density wouldn't be so, necessarily very large.

0:13:04 SC: And what is the Schwarzschild radius for the earth? I feel like it's some very small number.

0:13:07 RP: It's, yeah, tiny.

[laughter]

0:13:11 RP: I forget what it is something like a centimeter.

0:13:13 SC: Centimeter or something like that.

0:13:14 RP: I can't remember exactly.

0:13:15 SC: A neutron star with the mass of the Earth would be the size of Los Angeles, or something.

0:13:19 RP: Something like that yeah.

0:13:20 SC: A black hole is a centimeter across. That's a lot of mass in a very tiny area.

0:13:23 RP: Oh, absolutely, yes.

[laughter]

0:13:25 RP: But you see, I know Wheeler was very worried about this. He said, "What happens? Do you get the singularity or does it swish around and come out again?" And it was a big question. Should you trust the Oppenheimer model, Oppenheimer-Snyder model or is that unrealistic because of irregularities? And at that time, I should say, the craziest time was around about 1962, I think. And around about that time there was an argument by two Russians, Lifshitz and Khalatnikov and they had produced a paper which seemed to say that singularities did not happen in general circumstances.

0:14:01 SC: Right.

0:14:02 RP: So that when the thing collapsed if it was a general irregular collapsing body, it would swish around, it wouldn't reach these infinite densities, infinite curvatures. It would swish around and maybe come swirling out again or something like that. So that's the picture that a lot of people had.

0:14:19 SC: But you were able to prove otherwise. And what I love about it is, in some sense, maybe this is exaggerating 'cause I don't know the history very well, but in some sense, what you did represented a shift in technique in general relativity from finding exact solutions that were simple to making an absolutely general statement that just relied on the sort of intuitive powers of the theory, but made very rigorously mathematical.

0:14:44 RP: No, you're absolutely right. You see other people had found models, which required a lot of ingenuity but they had usually had some special symmetry or something like that. And these solutions, very beautiful solutions often, but whether they were realistic, or very special.

0:15:03 SC: Right.

0:15:03 RP: The only other way you could was to use high power computers and work out. But then in those days, people didn't have the kind of computers we have now.

0:15:13 SC: Right.

0:15:13 RP: And it was pretty hard to get any impression as to what happened in the general case. So I started thinking about this, I'd been thinking about other problems a little bit like this. One of them which I never published anywhere was worrying about the old Steady State model.

0:15:31 SC: Okay.

0:15:32 RP: See this was a cosmological model that was sort of in vogue when I was becoming a graduate student and becoming interested in general relativity in a serious way. And in Cambridge, where I was, it was a popular view.

0:15:47 SC: It was a hot-bed yeah.

0:15:48 RP: Yes, that the universe, although it was expanding and the mass sort of got less and less by the expansion. This would be mass replenished by hydrogen gas appearing spontaneously and it was a very beautiful model in a way because as the expansion took place, the matter was replenished and you had a universe which was sort of stable and it remained forever in this way. And some curious properties, but the question that I was interested in is, could you, in any way, make this consistent with Einstein's general relativity without having to introduce negative energies and things like that. And you could see pretty well that that couldn't be the case if it was very symmetrical, but then I started wondering well suppose it's irregular in some you quite serious way. Does this still cause a problem with general relativity? And I came to the conclusion, using sort of topological types of arguments, that you couldn't save it.

0:16:50 SC: Is it even possible to give us, I know this is a very intricate differential topology question, but is it possible you give a flavor of the argument? It's something like gravity is always attractive. And that's the basic principle.

0:17:01 RP: Yes. That certainly... But it was mainly how it behaved on light rays. That was the real argument. You look at how light rays behave, and it's a bit like a lens. You see, you have a parallel beam of light rays, and the way that mass acts on that, is to give a... It focuses like a positive lens. So, convex lens would cause these parallel rays to focus. Now, if you have an astigmatic lens, suppose you imagine a lens which in both, one direction is positive, and in the other direction is negative, I mean, you don't normally find these lenses, but that's the way gravitation behaves. So if you just go through empty space, then it focuses one way, in one direction, and expands out in the other direction.

0:17:45 SC: And this is what leads to spaghettification if you fall into the black hole.

0:17:48 RP: Yes, it squashes you on the one hand and stretches you in the other, exactly, that's right. So, that's what empty space curvature does. But the thing is, if you have combinations of lenses. It's quite interesting. You can do this just with ordinary optics. You have lenses, and you put them on an optical bench, and if you had these astigmatic lenses, what you find is that if you... Suppose you had one and an another sitting right next to it, an astigmatic lens which is at right angles, I mean their planes are parallel, but the direction of the astigmatism is at right angles. Then one cancels out the other, and so it's just like a flat piece of glass. But now suppose you pull them apart. Then you find there is a residual effect which is a focusing effect.

0:18:33 SC: Interesting.

0:18:34 RP: And this is connected with the energy in gravitational waves, so the gravity acts like an astigmatic lens. But when you have a lot of them, one after the other, there's a net effect, which is focusing as though there was matter, and this is the effect that gravitational energy has, it's focusing. So I knew about these things by thinking about these focusing effects and so on, and it was using this kind of argument, together with topological arguments, that you could see if you reached a point of no return, and that was a critical point as knowing what that meant...

0:19:08 SC: Right.

0:19:08 RP: Then you would find that this focusing property would be irreversible, and you could show that there had to be some singular place inside the object it was collapsing. Really, it gets to a point where you don't know what happens. It sort of stops, space time [chuckle] gives up.

0:19:25 SC: Yeah. But singular doesn't just mean special. It means the curvature is getting infinitely big in some sense.

0:19:31 RP: That's the expectation, although the argument that I had didn't directly show that. It just showed that there's something stopping this. The space time comes to an end, then it stops.

0:19:40 SC: Right.

0:19:41 RP: And the normal expectation is that it gets... These focusing effects become infinite, and so things just crumble up and you can't get any further.

0:19:51 SC: And you don't necessarily, it doesn't immediately follow logically that it's a black hole. But you had ideas about that? [chuckle]

0:19:56 RP: Yes, that's true. But the argument that I had didn't prove it, what we call a black hole. It just showed that you had the singularity. You had to make a further assumption, which is what I call "cosmic censorship", which is if the singularities, in general, are of the kinds that you, roughly speaking, can't see them [chuckle], then you do get what we, I think we now call a black hole. But it did depend on this cosmic censorship hypothesis.

0:20:24 SC: Right. Which is still not completely proven, is that correct?

0:20:27 RP: I think that's correct, yes. There's a lot of evidence that it's true, I think in general. Well, the argument is that it has to be. You look at general situations.

0:20:35 SC: Yeah.

0:20:36 RP: Then you can cook up special examples which disagree with it, but they're not realistic.

0:20:41 SC: So the astronomers with their data prodded you to think about this problem, and then...

0:20:46 RP: Absolutely, yes.

0:20:47 SC: You proved something. Did your proof prod the astronomers to take black holes more seriously?

0:20:52 RP: It did eventually [chuckle] It was quite interesting because you could see somehow a huge amount of skepticism about black holes, and I used to be asked to give lectures at these Texas symposium, which happened every, I think every year, at first. And usually, I was asked to give a talk, something about black holes and you could see gradually people beginning to take it seriously and more of more, of me. But there's a oomph, it sort of went over to the other side. It sort of happened very rapidly once enough people got used to the idea.

0:21:30 SC: And then, I mean on the theoretical side, black holes became a whole area of study, and Stephen Hawking and Brandon Carter and other people...

0:21:37 RP: Yes, indeed. Yes, that's right. And Hawking's remarkable result about the fact that they do a very tiny amount of radiation, and so if you imagine in the very remote future of the universe, and these huge black holes. Well you see now, we see huge ones. Initially, there were just the odd double star system, where you would see one star and other one, it seems to be going around something else that you couldn't see.

0:22:03 SC: Right.

0:22:03 RP: But maybe there was some plain where material was coming out if. You couldn't see the object itself, and so people speculated that that was a black hole. The evidence was pretty indirect for a while, but now the evidence is, well, indirect in a sense that you don't actually see directly into the hole, but you see things... Like in our galaxy, we have a... What we call a super-massive black hole, which is about four million times the mass of the sun, and it's really remarkable. You can see these pictures over... So you have to speed a little bit [chuckle]

0:22:40 SC: Yeah.

0:22:41 SC: But not that much, and you can see stars going around in these sort of elliptical orbits, and there's nothing in the middle. [chuckle]

0:22:47 SC: Yeah, we're going around a big heavy thing that you can't see.

[chuckle]

0:22:49 RP: Yes. That's right.

0:22:49 SC: Although you see, except it's not that big, it's a small, compact heavy thing you can't see.

0:22:53 RP: That's right, it's pretty small, by the... Yeah, that's right. Well, four million solar mass, I'm not sure quite how big that is, but it's not huge.

0:23:00 SC: It's less than a light year. Right, yeah. It's very tiny.

0:23:02 RP: Yes, yes.

0:23:02 SC: But so, when Hawking, circa 1974, argued that black holes are not completely black given if you take quantum mechanics into account, they radiate. How did that strike you? Was that a controversial, at the time?

0:23:14 RP: I can tell you exactly what happened. You see, I think I was away from Cambridge... Sorry, I was working in Cambridge at the time. No. Yes, it was in... No it's not... When was this? That was 70's, wasn't it?

0:23:26 RP: '74, early 70's, yeah.

0:23:27 RP: I must have been in Oxford by then.

0:23:30 SC: But you and Hawking had become close and work collaborators?

0:23:32 RP: Oh yes. No, I knew him well, but the point was I'd come back from somewhere. [chuckle] Exactly where, I can't remember, I have to work that out. But Dennis Sharma, you see, who is a great friend of mine, and I learn a lot of cosmology from, and he was Stephen Hawking's supervisor. And Dennis was a great person for getting the right people to meet each other, and so on. People who might benefit from encounters with other people, and he knew all the physics that was ground around. So I learned an awful lot of physics from Dennis. But anyway, I come back and Dennis told me, "Oh, have you heard the latest? Stephen Hawking has showed that black holes radiate." And I said, "What?"

[laughter]

0:24:13 RP: So I got hold... I phoned him up, you see, I phoned up Stephen and I said, "What's this all about?" And he said, "Well, it's tied in with the ideas about thermodynamics." and I said, "That makes a lot of sense." So no, it didn't take me long to come to the conclusion it was probably right, what he said.

0:24:32 SC: Well, to be fair to the audience, you had previously shown that you could extract some energy from a rotating black hole, but a limited amount, and you had to do it intentionally.

0:24:42 RP: Yes.

0:24:42 SC: I wouldn't be automatic, but that kind of pushed people on the road to think about these questions.

0:24:46 RP: Yes, that's right. That you could get stuff out, in a sense, you could get energy out of it. But this was going a little further. It was curious because... Now, I must have been in Oxford, because I remember how this came about. We used to have these meetings every Friday in my office in Oxford with my graduate students, post docs and people interested. And if somebody was visiting, we'd had have them dig up a nice little talk, and Stephen was visiting at the time, and he was telling us about... He was imagining little black holes, which be might be created in the Big Bang. And the idea was if they were rotating, would they lose their energy in the rotation? And he showed some calculation about this, and it was actually not very long after that, you see. I must have been visiting... I can't remember exactly how it was I saw Dennis at that point, but I phoned Stephen up, and it was really following up on this calculation he had done previously, about the rotating ones. And I think that he found that they didn't need to be rotating.

0:25:49 SC: Right.

0:25:49 RP: Which rather surprised him.

0:25:49 SC: Yeah. Every black hole does it, right.

0:25:50 SC: Yes, that's right.

0:25:51 SC: And I think that in the famous textbook by Kip Thorne and also Misner and Wheeler, there's this picture of an advanced civilization that has built an energy extraction device around the super-massive black hole, at the center of their galaxies. A lot of energy we could, in principle, get out.

0:26:06 RP: Absolutely.

0:26:08 SC: Free from our dependence on foreign oil sources if we could really harness black holes this way.

0:26:09 RP: That was the idea. Well you see, this was the argument. I wrote a paper in an Italian journal, there as a conference in Italy, somewhere, I forget where now. [chuckle] And there were people talking about very massive stars, and so on, and I asked to give a talk on black holes. Which I did. But I had come to this conclusion that you could extract energy, and I imagined that you could do this by having particles which would split up into two, and so on. But when it came to the talk... Actually, which way round was it? I think I did give it that way around, but I thought about also about the civilizations rotating around the whole and extracting energy out. And there this simple argument, you can see they could do this from quite general principles, they just lower you know fill buckets full of rubbish and lower them into the whole and tip the rubbish in and they would extract more energy than the mass of the rubbish so it goes there.

0:27:08 SC: And when Hawking did explain that black holes give off radiation, this all came as part of this, as you mentioned Thermodynamics.

0:27:15 RP: Yes, that's right.

0:27:15 SC: Like this package that black holes have entropy.

0:27:18 RP: Yes.

0:27:18 SC: And there was this sort of analogy between what black holes do in the laws of thermodynamics and this really said, "It's not analogy, it's true". Black holes have entropy.

0:27:26 RP: That's right. Well, it was curious because, you see the entropy of a black hole, it was really Bekenstein had had a fairly rough argument, but I was quite happy with that because it seemed to be very consistent that the area of the black hole should, should have an entropy and that Bekenstein's argument looked pretty convincing to me but Stephen then had a much more exact argument, and which was more impressive mathematically. But this came after a lot of discussions between Stephen and Brandon Carter and, who was the other one?

0:28:04 SC: I know the paper you're talking about, "The Laws of Black Hole Mechanics", but I'll tell the audience afterward.

[laughter]

0:28:12 RP: Yes tell the right people I'll give you a set. I think there were only three people maybe there were four.

0:28:15 SC: Yeah.

0:28:15 RP: But they were exploring the analogy between thermodynamics and black holes. But Stephen definitely just thought it was an analogy. I remember talking to him about this and I was sort of thinking it was real you see.

0:28:29 SC: Mm-hmm.

0:28:29 RP: But you see, in a way, he'd been looking more deeply into it than I had because he realized if it was really thermodynamic then the black holes had to have a temperature and that...

0:28:38 SC: And we all know that's not true.

0:28:38 SC: It's not the case. Yeah 'cause they just swallow things, there's no way it can have a temperature you see.

0:28:43 SC: Right.

0:28:44 RP: But then he found that they did.

0:28:45 SC: I think that in "A Brief History of Time" he mentioned that he was literally annoyed at Bekenstein for suggesting the entropy was real and that motivated him to do this.

[laughter]

0:28:54 RP: That's interesting, I hadn't quite realized it was that argument but that's right.

0:28:58 SC: Did that help get you interested in entropy? Because it was just a few years after that, that you started talking about the entropy of the early universe.

0:29:06 RP: It must have done. I'd have to try and put it together but to be able to assign a value to this entropy that that was crucial for that you see. I can't quite remember the order of my thinking here. But a big... Suddenly something which I had played around with a lot was thinking about... Well, I thought about it in the Steady State model you see and issue of entropy balance troubled me, you see. But there you see you had this creation of the hydrogen which the fact that it was condensed you see and formed objects could be a source of the entropy and so... Source of low entropy I should say. A reservoir of low entropy. So that's how it's sort of squared itself in my mind with the Second Law issue. I'd been worrying about it then already. But when that had to be given up and one was looking at models which expanded and didn't have creation of matter, at some point I was worrying about this question, but it didn't really have substance to it until the Hawking entropy, well Bekenstein and Hawking entropy value for black holes and how huge it was.

0:30:18 SC: Yeah, so just... I need to be very fair to all of the audience listeners. Entropy they've heard the word before, but it's roughly speaking, a measure of how random disorganized a certain system is.

0:30:31 RP: Sure.

0:30:32 SC: And in some sense, intuitively, you might have thought that a black hole has zero entropy. There's not a lot of different ways a black hole can be right. It's not like a cup of coffee, where there is a lot of arrangements of the atoms inside. But Hawking and Bekenstein show that there's actually a huge number. And that inspired you in some sense to start writing about... The Second Law of Thermodynamics says that entropy tends to increase in closed systems, and therefore, it's not surprising that entropy used to be lower in the past.

0:30:57 RP: That's right.

0:30:57 SC: But cosmologists have a long history of being confused about this issue.

[laughter]

0:31:01 RP: Yes they have.

0:31:01 SC: And I think that... Let's just be honest that this is the most profound, there has been quite a profound effect that you have had on my career because it was your papers emphasizing this problem of why the early universe had such a low entropy, which I thought were completely convincing, and puzzled by why my fellow cosmologists don't take this seriously. So why don't you explain how you think about this?

0:31:23 RP: You were one of the few people who really latched on to it immediately. But I was just as puzzled why people didn't take it seriously. But the basic argument is this, as you say, I mean the entropy or the randomness if you like, increases with time. And that's the second law. Another way of saying exactly the same thing is as you go back in time, it decreases. So as you go back and back and back in time you should find the entropy very small. Now, what's the earliest evidence that we directly see of the universe? In states that's the cosmic microwave background. So this is radiation coming from all directions, electromagnetic radiation, and this radiation has a lot of entropy in it. But the main point that I'm gonna sort of concentrate on here is if you look at the, curve which represents the intensity for different frequencies. You have this thing, the curve goes up and then comes down again and it has... It's what's called the Planck curve.

0:32:23 SC: The amount of light at different wavelengths.

0:32:25 RP: That's right. So there's a certain temperature where its maximum, and then, the radiation at higher frequencies, it goes down. And this Planck curve is observed. The COBE satellite, when it went up, you'll have to tell me the dates, I don't remember. [chuckle]

0:32:43 SC: 1991, '92, yeah.

0:32:44 RP: Okay. The COBE satellite measured this curve, the intensity for different frequencies of this radiation. They found an extremely good fit, an almost perfect fit to the Planck spectrum. What does the Planck spectrum tell us? It tells us what we're looking at is maximum entropy. I mean, that's the whole point of it, it's what they call the black body radiation, which meant maximum entropy. So here, this is what I call the mammoth in the room, [chuckle] and you go back, and back in time where the entropy is supposed to be going down, and down, and down, until it reaches a maximum.

[chuckle]

0:33:18 RP: Which is sort of the wrong way around.

0:33:20 SC: Right.

[chuckle]

0:33:22 RP: And I don't know why people didn't worry about that more. But the point is, the answer... I think partly because it's muddled up with the expansion of the universe. That people sort of think, "Oh well, the universe is expanding, and so maybe there's not much room for entropy down there". Or something like that.

0:33:37 SC: I think it's partly that and partly that when we're taught thermodynamics gravity is not a part of it, right?

0:33:42 RP: Yes. I think that's right yes.

0:33:42 SC: We don't think about black holes, and so forth.

0:33:43 RP: I mean, there were people like Tolman, one of the early mathematical physicists who studied cosmology, and he understood pretty well about the entropy issue. So, people certainly did understand it, the right people at that time. But anyway, yeah, you got this huge amount of entropy in the radiation, which was a lot actually. And then why does that second law hold when it starts off at the top, and it's got no where to go, if you like. [chuckle] And you can have to convince yourself that the expanding... Expansion of universe doesn't help.

0:34:15 SC: Right.

0:34:16 RP: Which is the point Tolman did understand. But the other issue, you see you've got this radiation coming from all directions, in which it has this thermal character, but the other point about it is it's also very uniform, so it's almost completely uniform over the whole sky. If you take account of the Earth's motion through the radiation, it is uniform over the sky to about one part in 100,000. So, it's really pretty uniform. Now you see, what does that indicate? You say, "Well, okay". Suppose you have a gas in the box, then the temperature would be pretty uniform, if it's at a maximum entropy stage. Just leave it in the box, and the temperature, apart from gravity and all that stuff, it would be uniform temperature. So that also finds, represents high entropy. So where is it low? Well, it's low, if you think of not a gas in the box, but suppose you you think of a huge box, of galactic scale, and it's got stars running around in it.

0:35:18 RP: Now those stars will tend to clump because of their gravitation attraction, and eventually become black holes and as they do this, the entropy goes shooting up. Particularly with the black holes, because as we know from Bekenstein and Hawking, the entropy is absolutely enormous. So that represents an increase in entropy. So you have these two things about the early universe, one is the Planck spectrum, which tells you that the matter and radiation, you see the Planck spectrum was telling you that the early stage of the universe, photons and matter were a kind of, at maximum and randomized as much as they could be. And so, that radiation comes to us, and you see this Planck spectrum. But the other feature about it is that it's uniform, and that as far as gravity is concerned, is very low entropy. Because as things start to clump, and a good example of this is our sun. You see, our sun used to be a... Well a long time ago [chuckle], a distribution of gas all over the place and it went through various stages, but it, it clumped together and produced this hot body. It would be hot, even if there were no thermonuclear reactions, at all.

0:36:34 RP: So it gets that heat, which is... When compared, the darkness of this background sky is a very low entropy situation. You can get energy out of it by simply...

0:36:47 SC: And we do. [laughter]

0:36:48 RP: We do, absolutely, that's why we're here. The plants do by photosynthesis and we live off plants and animals that eat plants and so on. And so that's where it all comes from. So it comes from the fact that the sun's a hot spot in a cold background sky. And this is why we are interested in the second law of thermodynamics, because it's low and it's creeping up, and is what we get our structure from and all that stuff.

0:37:12 SC: So ultimately, the cosmic microwave background, it looks like it's a maximum entropy but that's only 'cause you forgot, that there could've been all these lumpinesses which would've made the entropy much lower. I think it's true, the entropy of the black hole at the center of our galaxy is larger than the entire entropy of the cosmic microwave background.

0:37:30 RP: That could well be, yes. And if you look at it, I'm thinking, all the stars, all the galaxies that are around, it's absolutely enormous, the entropy in the black holes is absolutely stupendous by comparison with anything else.

0:37:45 SC: So this is very good news for the second law of thermodynamics, it explains that the early universe had a low entropy actually, not a maximum entropy.

0:37:51 RP: That's right.

0:37:52 SC: It's bad news for cosmology 'cause we're stuck with this question of why the early universe is like that?

0:37:56 RP: Exactly.

0:37:57 SC: A lot of cosmologists like the theory of inflation proposed by Alan Guthe around 1980, and you were one of the first gadflies there saying the inflation is a bit of a cheat, I think.

0:38:08 RP: Yes. Well you see, I thought this is a crazy idea, it won't last a week and how wrong I was.

[laughter]

0:38:12 RP: Now I was completely wrong. It just seemed to me such an artificial theory. You had to invent a special field and... Well, you see, in the old days they called it a Higgs field because they hoped that the Higgs field would be the same as the... But that didn't work.

0:38:26 SC: We should explain the basic idea is that the universe underwent in very, very early times a period of super fast accelerated expansion, which I think you would agree, it's true that if that happened and if the energy driving that expansion turned into matter and radiation, it would give you a universe looking like our universe, but it doesn't help explain the initial conditions.

0:38:47 RP: Yes, it doesn't because you've gotta have a pretty uniform already, otherwise it doesn't even work.

0:38:52 SC: Right.

0:38:52 RP: So, you're gonna have quite general arguments to show that it can't really be the explanation of the low... Just not just the low entropy in the early universe, this particular form that it's low namely in gravitational degrees of freedom. And it's just strongly strange why cosmologists... You can see a list of what are the problems of cosmology, and you look down the list and say, "Where is this?" [chuckle]

0:39:16 SC: Yeah, I am totally on your side there, but so both of us are in the small band of people who've been trying to invent models of the universe which naturally explain this early entropy but that's where we diverge. So I think that Inflation... I would honestly give it a 50% chance of being part of the final answer.

0:39:35 RP: That's a lot more than I'm giving it. [laughter]

0:39:37 SC: Exactly, but a lot lower than all my friends give it, who are professional cosmologists.

0:39:39 RP: Oh absolutely, yes, you're right.

0:39:42 SC: And you've been working very recently on a new model of the universe on its super larger scales.

0:39:47 RP: That's right. Or recently isn't even all that recently, It's... I forget now, it's over 10 years anyway.

0:39:53 SC: Okay.

0:39:54 RP: But nobody paid. Well, you see it took me a long time to... I used to lecture about... Let me explain the model first.

0:40:01 SC: Please.

0:40:03 RP: The argument is that, think of the two ends of the universe. We have this future which seems to be dominated by this exponential expansion. So this is observations of supernova stars and other things together, which persuaded cosmologists enough to give the two groups the Nobel prize, [chuckle] which was very deserved to see that the universe is having this, what's called an exponential expansion. It's a sort of self-simulated... The range of expansion is proportional to the size and so on. So it's something which used to be taking place. Now, those of us who were brought up on cosmology and read the cosmology books would have seen that these kinds of models of that exponential expansion are perfectly well described in the books. These are models in which there is a thing called the cosmological constant, which is positive, and it's usually referred to as a Lambda, a capital Lambda, so it's like a V upside down.

0:41:12 SC: Right. Basically, the energy of empty space.

0:41:14 RP: Well, you can think of it as energy, people call it dark energy, yes, yes. I'm not sure I'm happy with that term but nevermind that's... [chuckle] It's certainly well explained by this, excuse me, by this Einstein cosmological constant. Einstein introduced this term in 19... When was it? '17.

0:41:40 SC: 17.

0:41:41 RP: 1917, for what was the wrong reason. He wanted a model which was static. He hoped that the universe was static. I thin it's a sort of appealing idea, the steady state model, as again, the same sort of appeal that... Philosophically appealing in some way.

0:41:56 SC: To be fair, I think it was also the observations at the time, the universe looked static to astronomers in 1917.

0:42:01 RP: I guess Hubble hadn't quite.

0:42:04 SC: Right, that was 1920's.

0:42:05 RP: But it was after... I can't remember, it was after the Vesto Slipher, wasn't it? 'Cause Vesto Slipher had already seen the expansion. Maybe it wasn't as a convincing argument that...

0:42:16 SC: Well, you saw that there were distant... You saw that there were objects that were moving away from us.

0:42:20 RP: Yes, I guess.

0:42:21 SC: We didn't know if they were far a way.

0:42:22 RP: Yes, that's true. It probably wasn't terribly persuasive, but there was some indication, but not enough to rule out a model rule out a model like Einstein and the one he produced then. Before that model, he needed this term, and it's the only thing you can really do to Einstein's equations, without wrecking them, in my view. You just add this term, and he didn't like to do this at first, but then after, I guess he thought, "Well let's put it in, and then they get a static model." Which we refer to as the Einstein cosmology. But then not long after that, Hubble showed pretty convincingly that there was this expansion in proportion to the distance, so the whole universe seemed to be taking part in this expansion. And so Einstein, I guess, kicking himself for not having stuck to his original equations which seemed to indicate he would have predicted it.

[chuckle]

0:43:15 SC: He could have become famous, yeah.

0:43:16 RP: He could of become famous, yes. Well, he considered this to his greatest blunder and I think that's true. It's on record, Gamow has recorded Einstein having said this. So, okay this is... But it's all in the cosmology books despite Einstein retracting it. And yeah, people studied... I studied it, I studied and looked to see what the infinity looked like in this model, and so on. So I was familiar with it, although I was a bit slow on the uptake to taking it seriously. I think it was Jerry Ostriker who told me. I said, "Well maybe these distant supernovae look red because of dust, and so on. Which people thought maybe it was the case, and he said, "Oh, no. There are all sorts of other things it's got. You... It's not just that."

[chuckle]

0:44:07 RP: "You have to take it seriously." So I thought, Okay, I'll take it seriously." [chuckle] And it wasn't, I don't know how long after that conversation, that I began to think about the remote future. Now, you see the remote future, and I mean the very remote future, we have the universe expands, and expands, and expands, and it gets more and more rarified. And nothing much happens, you get dead stars and it gets pretty boring, and the most exciting things that are around are these black holes. But they're pretty boring, too. You sit around waiting for it to evaporate according to Hawking's evaporation, and for the big ones, it takes about a google year, something like that. So you're thinking about 10 to the 100 years, one with a hundred zeros. [chuckle]

0:44:48 SC: Yeah.

0:44:48 RP: That number of years.

0:44:49 SC: A long way.

0:44:50 RP: Yes. And that's an awful long time, so I regard that as a pretty boring area, we'll wait for that. But then you see after it's gone off pop by Hawking evaporation, now that's the very boring era.

[chuckle]

0:45:01 SC: Not even black holes, yes.

0:45:02 RP: That's right. I mean, I couldn't think of anything more boring than that. And I admit, this is an emotional argument, but it just seemed to me, for our universe, that's it you see.

0:45:12 SC: Right.

0:45:13 RP: It's forever, and ever. It's just an eternal tedium, you see? [chuckle]

0:45:17 SC: Well, it is weird and I think that cosmologists under-emphasize how weird it is. We always talk about the last 14 billion years of the history of the universe, 'cause that's the past, that's what we've observed. And we say it's a long time, and so forth, but our best current models say we have infinity years toward the future...

0:45:34 RP: That's right.

0:45:34 SC: Which is a rather big imbalance.

0:45:36 RP: And yes, in terminal bore... In terminal boredom.

0:45:39 SC: Yeah.

0:45:40 RP: Well, you see, then I began to think, "Well, who's gonna be around to be bored by this?" And then I thought, "Well, pretty well photons." and it's damn hard to bore a photon.

[chuckle]

0:45:51 RP: That's actually, I don't expect you to have actual experiences, so boring is perhaps not an appropriate term.

0:45:58 SC: Again, to be fair, I did interview David Chalmers on the podcast, and he thinks that photons can have actual experiences...

[laughter]

0:46:04 SC: Just a little bit, so maybe let's think about the photon's feelings here. Let's take those into account.

0:46:08 RP: Okay, well that helps me a little.

[laughter]

0:46:11 RP: Because they still don't get bored. They don't get bored because if you take relativity, now this is just ordinary old-fashioned special relativity without the curved space time and all that. It doesn't matter, curved or not, the photon, because it travels at the speed of light, the time is just stretched out, and it's nothing. So right from its creation in some particle decay or something, this photon goes out to infinity and it experiences zero time. So it's not bored in the sense of, forget about whether it actually has feelings or not.

[laughter]

0:46:52 RP: It doesn't experience the passage of time. Now, this is the sort of thing I used to play around with when thinking about gravitational radiation, and how you put boundaries on space times and so on, and it was a useful way to think that this boundary is something you could imagine going through and if you were a massless thing, when you hit that boundary you say, "Well, where the hell am I?" you see. [chuckle] There's got to be something on the other side, you might think. I mean, it's only a way of thinking. I didn't think it very seriously that way.

0:47:17 SC: So okay... Just to get this correct in people's minds, this is a boundary that we're talking about that is literally infinitely far away but you're saying the photon experiences zero time? So...

0:47:30 RP: Yes.

0:47:30 SC: It gets there. [chuckle]

0:47:31 RP: That's exactly right. But I think it's very useful if you have seen these pictures by the Dutch artist MC Escher. There's a very famous one with angels and devils and they, in the middle you can see the angels and devils interlocking and then you go out, there's a circular boundary and they seem to get smaller and smaller and smaller and they crowd in on that boundary. Now, this is a representation of a kind of geometry, which is called a hyperbolic geometry, and if you think of those angels as really all being the same size as each other, and the devils all the same size, then although it looks to us as though they get smaller and smaller, to them, they're all the same size.

0:48:09 SC: And did you have something to do with inspiring that Escher?

0:48:13 RP: No, that was... My relation to Escher was something, [chuckle] somehow a little different, but that was Coxeter. It was the same meeting, yes. This was in the International Congress of Mathematicians in, whenever it was, early 50s I think.

0:48:27 SC: Okay.

0:48:28 RP: And yeah, the mathematician Coxeter who wrote to Escher and said, "Well, you might find this interesting to explore" you see.

[laughter]

0:48:38 RP: So no, that was amazing.

0:48:38 SC: So it's a representation, it's in the spirit of what you did for space-time in general relativity where you can express infinitely far away things in a finite piece of paper.

0:48:47 RP: Exactly, that's what it is. And the thing about the Escher picture is it's what's called conformal. So that means that small shapes are accurately just... They're squashed down. You look at the eye of the devil, if you like, it's got a certain shape and no matter how close to the edge you get, it retains that shape. It's smaller, so it's squashed in one direction and equally well in all other directions. So it's what's called a conformal representation. So, it's a conformal picture of an infinite universe but where you see infinity as a finite, at a finite place. Now you can use the same trick in cosmology, but then you're thinking of space-time and not space. And what conformal means is that you preserve the speed of light, if you like. The thing's called the light cones which tell you how the speed of light goes or how light goes. And so, this squashing down of infinity, if you are light, you don't notice the difference. In fact, it's a more general thing. If you don't have any mass, you don't notice the difference.

0:49:52 SC: If you move at the speed of light.

0:49:54 RP: At the speed of light. And it's also a factor, not thinking of particles, but of fields and the electromagnetic field which light is a feature of electromagnetic fields. This is Maxwell's famous equations and these equations of Maxwell again are insensitive to the scale, so you can squash it and stretch as long as you do it equally in both directions. In the space-time that means you squash the time and the space equally. Then that kind of transformation is not noticed by light or not noticed by the Maxwell equations.

0:50:28 SC: Right.

0:50:28 RP: And that's true also of the Yang-Mills equations of particle physics, nuclear physics.

0:50:37 SC: So these are the nuclear forces, the strong and nuclear force, etcetera.

0:50:39 RP: That's right, they all have all this... Except for mass, so you've gotta be careful, you've gotta get rid of things which may disturb the conformal... But the equations themselves, as classical equations are completely insensitive to the scale. So anything which doesn't have mass, that boundary which we've just drawn, it's just like anywhere else. Now that's infinity, you see. Well, it's not quite, because we have to worry about the black holes, but the black holes eventually decayed away, so we got rid of that too. [chuckle] But the other end, you say, "Well what's the excuse for stretching out the big bang to make it look similar?" Now the excuse there is not an excuse because most big bangs don't work.

0:51:21 SC: Wait, sorry, I think maybe we skipped a step, or I just wasn't paying close attention, but you've been explaining the future, and it has a certain nice remarkable mathematical properties.

0:51:31 RP: Yeah.

0:51:31 SC: And your move is to relate it to the past, right? To say like, "Actually, the very past of the universe kind of looks similar. Maybe we can make some money off of that."

0:51:41 RP: Exactly, that's right. Now you can use a similar trick, but the opposite way around. So in the future, you have to squash it down, like the Escher picture. In the past... I was trying to find an Escher picture which did it for the... It isn't quite.

[chuckle]

0:51:54 RP: There are some which almost do it. But if you go into the past, you can stretch it out. Now, all the standard cosmologists, the ones that... What Friedmann, and Lemaitre, and Robertson-Walker, the cosmologists. The models that most most cosmologists play with do have the property that you can stretch out the big bang in those models, to make it nice and smooth. But almost all models, if you think of what possible things they could be in Einstein's equations, they're a great mess at the beginning, and they don't have a nice, smooth big bang. But those ones which do have a nice, smooth big bang are ones that you can stretch out and make it a nice conformal boundary. And those are the ones which you could say that the gravitation degrees of freedom are killed off, right at the beginning. So you have a nice picture with entropy low in gravity, but not low in anything else, and so that's being able to do that trick is seems consistent with what we seem to see of the universe.

0:52:58 RP: And my former student and colleague, Paul Todd used this as a criterion for the kinds of big bangs that one might be interested in. But you can stretch them out in this conformal way. Now you see the... Look at what's the argument here? You want to say in the future, it's because you've got some masses, things around. In the past... Well, you see, the argument is sort of similar, but not quite the same. There you have very, very large temperatures. Get hotter and hotter the closer you get into the big bang. That means the more and more energetic the particles are, and when they get very energetic in the sense of their motions, kinetic energy, and that completely swamps their masses.

0:53:41 SC: They're effectively massless.

0:53:42 RP: Yeah, so they're effectively massless. So really, around the big bang, everything is pretty well massless. So it's sort of reasonable physically to do these tricks at both ends.

0:53:52 SC: So what you're suggesting, what you've called it is a conformal cyclic cosmology.

0:53:57 RP: Yeah.

0:53:57 SC: You think our universe has an infinite number, presumably, of cycles?

0:54:01 RP: Yeah, might as well. [chuckle]

0:54:01 SC: Where you go from big bang to stuff like us, to the future, and then repeats.

0:54:05 RP: Yes, well the idea is that our big bang was the conformal infinity of a previous aeon. I call it an aeon, I like not to call our universe, because we're all entangled with each other, and it's a part of one big thing. So our aeon, A-E-O-N I like to think of it as, began with a big bang and ends, in a sense, with it squashed off infinity. But if you apply the stretching at the beginning, and the squashing in the future, you get a thing which looks a bit like a cylinder, and you can imagine that joining on to another tube, which was the previous aeon. So its most remote future, conformally, smoothly fits on to our big bang.

0:54:48 SC: And one of the exciting aspects is it might be observationally testable.

0:54:52 RP: Absolutely. Well, there are some new features on this. At first, I used to give lectures about this and said, "This is fun, and I can go on talking about this, and nobody will ever prove me wrong."

[chuckle]

0:55:03 RP: Because we don't have any way of seeing whether it's right or not. But then, I started having an idea. Maybe one could see a test, and so the first thing I thought of was what about black hole collisions? You see, our galaxy has a super-massive black hole in its center. So that's four million times the mass of the Sun. I think the Andromeda galaxy is what? About 20 times bigger, or something like that, and we are in a collision course with it. Not very near in the future, but you have to...

[chuckle]

0:55:32 SC: We're thinking big, here.

0:55:32 RP: Yes, that's right.

0:55:33 SC: It's professional cosmology.

[chuckle]

0:55:34 RP: But eventually, these black holes will... Galaxies collide, and the black holes will feel each other out. It'll take a while, finally spiral into each other and there will be one whacking explosion, which will carry away a significant proportion of the rest mass of the combined black holes. And that will be gravitational radiation, primarily likely LIGO detection of the black holes that we've seen, and very proud of. And now it's this is a far, far bigger explosion.

0:56:08 RP: Right.

0:56:10 RP: We might be lucky to see such a thing in a very distant future. I just... Well, just in the future, I don't know.

0:56:17 RP: Anyway, this explosion would carry out to the crossover between one aeon and the next, and you have to look at the equations now. You see, you need equations to do the gluing job from one to the next. And okay, you can produce equations which have nice behavior and they indeed kill off the gravitational degrees of freedom, but they don't kill it off... I mean, the degrees of freedom survive, but not as gravitational waves. They come through as disturbances in the newly created dark matter. So, you have to have... To make the equations work you have to have... We talked about dark energy, but this is dark matter and that seems to be some real substance out there. But in this theory, it's got to be there, it's got to be where the degrees of freedom of gravitational waves get picked up and translated into this form on the other side. And these would produce signals that could be seen, they will look like circular features, maybe concentric ones. Because in a cluster of galaxy, there'll be a lot of battles between black holes swallowing each other up and then end up with one big whacking one in the middle of the cluster. And that's the one that finally you get.

0:57:29 SC: That eventually evaporates.

0:57:30 RP: That's right. But there are claims and arguments about, whether we see these rings? I think the most persuasive argument was from my Polish colleagues, they had a first looking at the WMAP satellite and then the later satellite, which is Planck satellite, which did some very, very precise measurements of cosmic microwave background with radiation, and they claim to see signals of this nature with the confidence level... This is looking at the Planck data, with a confidence level of 99.4%. Nevertheless, people don't pay any attention.

[laughter]

0:58:11 SC: I mean, have they argued against it or are they just asking about it excited?

0:58:14 RP: I don't know, it's very strange. Because they... I mean, they had a lot of trouble with referees who said, "Look, you better this and then if we don't believe you, you've got do this test, that test." They did them all. The polls were absolutely... This is Krzysztof Meissner and Pawel Nurowski and... Well, it's Daniel An who is a Korean who did the analysis in that case. And they... In the Planck data command. They came to this conclusion of 99.4% confidence, using all the tests but the editor said, more or less, "Well, I'm afraid we're gonna have to accept your paper."

[laughter]

0:58:47 RP: "Despite all the complaints people had."

0:58:49 SC: Right.

0:58:50 RP: "But you should say in the initial part of the paper, this might be a chance effect."

0:58:55 SC: It's always possible, yeah.

0:58:56 RP: It could be a chance effect.

0:58:57 SC: But this is... But the good news is, it's in the data, data hopefully will improve, you've made a prediction, people will figure out one way or the other.

0:59:03 RP: Yes. But what's more exciting is what's happened more recently.

0:59:07 SC: Okay.

0:59:08 RP: You see, this is the same, more or less the same team, the Polish team with Daniel An, and they were doing a slightly more sophisticated analysis, which came from a discussion I had with Krzysztof Meissner. You know, maybe you could refine the signals and see what the shapes of them are and so on. And they then found a particularly strong signal for some very small ring-like structures. And this was puzzling to me at first, because it should be... I mean, they saw some evidence for the bigger ones, but it didn't seem nearly so impressive as the small ones. But then it occurred to me that I had thought about this before, but I'd not really dared to think about it seriously. Which is the question of what happens to these super massive black holes. See, any cluster will end up with a big whopping great black hole in its center, this will gradually, gradually decay over something like a 10th of a hundred years, google years.

1:00:10 SC: I mean, sorry, in fact, any cluster turns into a whopping big black hole, right?

1:00:14 RP: Pretty well. Yes, I think pretty well all the matter gets swallowed. I don't know exactly what proportion it is, but you would expect, I would guess, pretty well, most pretty well all the matter gets swallowed up. So you've got this black hole sitting there, and it sits there and eventually it decays away by Hawking evaporation. Now you see, Hawking evaporation is a very cold, most of it and you know, you could pretty well ignore it, [chuckle] enormously long wave length and you can ignore it. But as a total it carried away the entire mass of that super massive black hole and where does that mass go? Well, you think... Go think about the Escher picture again, you see, you have an event which is taking place right up near the edge of that boundary and that means all the radiation which comes out is concentrated right at one little point. So you would have, according to this cyclic theory, what I refer to as a Hawking point. You see the Hawking evaporation and these Hawking points would be a release of an enormous amount of energy right at that point and then it will spread out through about 380,000 years, which is the time between the Big Bang and the last scattering surface where you see the microwave background.

1:01:31 RP: And the amount it spreads out is to well, four degrees, which is about eight times the diameter of the moon. So, it looks quite a sizeable thing, but pretty small on the basis of looking at the whole sky. So you'd imagine spots of that size. Now, we wouldn't see them quite that size because our past light cone cuts through a bit of it, so that's a little technical point. But they're comprable at that size, they maybe say five times the diameter of the moon or something like that. But this is just the scale in which the latest analysis you seem to see an effect. And this would be regions where... I mean, they look at rings and you imagine this ring surrounding the Hawking point and in the middle it's heart and then it cools down as you get towards the edge of the ring, as the energy gets dispersed through this period of time from the Big Bang to the 380,000 years. And that spread, you can see it's concentrating in the middle and spreads out and it's completely consistent with that.

1:02:36 RP: And now the latest thing which is just about, I think now on the archive, the latest version of this article, is we're given a confidence level from the looking at simulations and things of 99.98% confidence. Now, this is just clearly out there on the data. Anybody else can look, and if they see something else when... We will have to see why, why we all see a different thing. But the evidence seems to be out there, and it has this confidence level is complete, clearly calculated at 99.98%. Now, one of the real problems for inflation of this, is that the point you would be seeing, not the big bang inflation, would be what's called the graceful exit moment. So inflation in the inflationary model... Okay, started very close to the big bang and then this huge expansion took place, and most things which happen in that region of this huge inflationary expansion would be spread out to an enormous size.

1:03:45 RP: So only at the very end would you get something which is restricted to this four degrees across the sky, and we don't see the signal bigger than that. That's the size of it. So if people come around and say, yes, they see the same signal we do, and I don't see why they can't do that. Then they would say, "Well how is this an inflationary effect?" If it's due to inflation, it would be how something was just happened at the last minute. Just as inflation turned off at this point, where they have a lot of trouble with anyway, call it graceful exit. That was one of the reasons I had trouble believing in it, how you turned the blasted thing off uniformly over the whole universe, which seems a great problem. And more of a problem now, because it's not just uniform, you've got odd, little points where there's a huge amount of energy spewing out, and I'm waiting to see what the inflationary explanation will be for these things.

1:04:38 SC: But the good news is... We're talking about data now, we're talking about observations. Other people can repeat the analysis.

1:04:43 RP: Absolutely.

1:04:44 SC: And we'll see what comes out of that. Good, and you've written a book about the conformal cyclic cosmology?

1:04:49 RP: I did. I wrote a book, yes. It was... I talked a little about the black hole collision, but nobody had seen them at that point. I didn't make any particular point of... About observation. Just that it potentially was possible.

1:05:05 SC: I do want to plug the books, this is a part of that.

[chuckle]

1:05:08 SC: An important part of appearing on... That's your reward for appearing on the podcast.

1:05:12 RP: Oh, yeah. But, Cycles of Time, is the title.

1:05:14 SC: Cycles of Time. Excellent, good.

1:05:15 RP: Yes.

1:05:15 SC: Available wherever books are available.

1:05:17 RP: Yes.

1:05:18 SC: But it's not the only book you've written. You've been very happy to go and write books about all sorts of topics. I think the people are gonna wanna hear about quantum mechanics.

1:05:27 RP: Oh, yeah.

1:05:27 SC: If that's okay. I think we've talked about quantum mechanics on the podcast, before. Certainly we will, going forward. There's the measurement problem.

1:05:36 RP: Absolutely, yeah.

1:05:37 SC: Quantum mechanics has this weird feature that there seems to be a thing that we need to include in the description that is, what happens when you look at something? Unlike any other theory ever in physics.

1:05:49 RP: Yes.

1:05:50 SC: And so like many people, you've been dissatisfied by the standard approaches to this problem. So how do you like to think about it?

1:05:57 RP: Well, I see... I take the view that quantum mechanics is not finished. I mean, I don't like to quote authority, but actually I do, [chuckle] because.

1:06:06 SC: When they're right.

1:06:06 RP: When they're right. I mean, Einstein was always... He was doubtful about the theory being a complete description of what goes on, and Schrodinger, who put forward the equation which quantum theory is supposed to satisfy. Well, he was troubled with it, you can see because he put forward this ridiculous situation of the cat, which is the superposition of alive and dead, as an example of the absurdity of following his own equation.

1:06:32 SC: Exactly, yeah.

1:06:32 RP: So he was not saying, "Look, this is what happens." He's saying, "This is an absurd thing. We don't understand what's going on."

1:06:38 SC: And that doesn't mean that they're right, but if those people were worried, then we have a license to be worried, a little bit at least.

1:06:43 RP: That's right. Well Dirac, also... You have to find the right quote there because he didn't express himself very much, but if you find the right place, he was also just as skeptical.

1:06:51 SC: I didn't know that, I knew about Einstein and Schrodinger.

1:06:53 RP: Yeah, that's less well known, but he... No, he regarded quantum mechanics as a provisional theory. Where it works, very well, but we need something better. I'm not sure how explicit he was about what it is that's worrying him, and maybe it was divergences, as well. But it was probably the measurement issue.

1:07:10 SC: There's a wonderful book by Adam Becker called, What is Real, that just came out. Which makes the case that we tell ourselves this false story about Einstein and Bohr, where Einstein just couldn't keep up.

[chuckle]

1:07:22 SC: And Bohr got it right, but in fact, Einstein... You know, his arguments were better but he lost the PR battle, back in the day.

1:07:28 RP: Yes, it seemed to be that. Yes, well it's quite curious because in my view, he was thinking along the right lines, because he was bringing in gravitational effects, and Bohr, at this particular case who saw a way of resolving the issue in favor of the conventional view. But that was because they never really considered the effect of gravity on things, it was the effect in gravity, and it's when you think of the effect of gravity, that's where things change. At least that's my view, and you can make a... I believe, a good argument, that there is a basic contradiction between the basic principles of both theories. Now when I say, "the basic principles", in GR, general relativity, this is the principle of equivalence. That is to say a gravitational field is like an acceleration. So if you fall freely in a uniform field, the gravitational field is gone as far as the physics is concerned.

1:08:24 RP: And the principle in quantum mechanics which I'm concerned with here is the principle of superposition, which as it says if you have an object which can be in one place, and if it can be in another place, then there are perfectly good states where it's in both places at once. And you can see this with neutrons and things, that's the way many things behave, and when it comes to cricket balls or baseballs that's not what you see. And the question is why, what's the difference? And I was... It's curious, 'cause I went to lectures when I was in Cambridge, I was just working on pure mathematics, but I went to lectures on various things that interested me, like cosmology and general relativity by Bondi, a course on mathematical logic by a man called Steen, about Gödel's theorem, material, machines and things, and then was a lecture by Dirac, and it was his first lecture where he talked about the superposition principle.

1:09:18 RP: And he had a piece of chalk and he, I think he broke it in two as an image of where it could be in two places at once. And he talked about it and my mind wandered for a bit. I don't know what I was thinking about and when it came back to the subject, he'd moved on and I remember him say something about energy, it wasn't quite sure what. I think it's just as well I didn't hear his explanation, because it might have calmed me down, but instead I've worried about this for ever since. So, how is it that big, massive bodies don't appear in two places at once. But then, you see, if you look at the principle of... I have an example about this. You think of an experiment done on the table top, which involves the earth's gravitational field and you can see treat it two different ways, either the sort of Newtonian way, which is the standard quantum mechanics procedure, putting what's called a term in the Hamiltonian, don't worry about what that means, but it's what they do, and the Einsteinian way, which we now know you pretend, you take a freely falling frame and there isn't a gravitational field.

1:10:22 RP: And then you compare the answers, you have a thing called the wave function in each case, and the two calculations are almost the same. But if you look at them carefully, whether they differ by what's called the phase factor, which you usually don't care about, and so if you stuck to one... Well, if you look at them carefully, you see that this thing called the phase factor actually has a little awkward thing with the time cubed in it, which tells you that actually what's called the vacuum... See, when you do quantum field theory, you have to... There's a thing you have to do, is you have to settle on what the vacuum is and then...

1:10:58 SC: A vacuum is an interesting place in quantum field theory.

1:11:00 RP: Yes, exactly, and what you find is that the vacuum is different in these two approaches. Now, this is might not matter because you say stick to one and you're fine. But now think of a different situation, where you've got an experiment where it's not the earth's field, you can forget about that, because it sort of cancels out, but the main point is that the Einsteinian point of view, when you have a superposition, if you look at what a little bug would feel near these superposed lumps, it's got one vacuum from one position and the other vacuum from the other, and you're stuck. Because in standard quantum mechanics you can't form these superpositions when it's different vacua. So what I do is to sort of say, "Okay, well, let's go through as best we can and see if there's a kind of error that you could attribute. It's not quite right, but how far off are you?"

1:11:51 SC: And so, sorry, just to conceptualize this, it's because the gravitational field of the thing is different that you can't sort of have a consistent quantum description of both fields at once?

1:12:02 RP: Yes, it's when the lump is in two places here and here, then its gravitational field... If you take the Einstein point of view of free fall, which gets rid of the gravity and then you have a different vacuum. So for each of these two locations, you have a different quantum field theory. And that doesn't make any sense, you can't go ahead with your standard procedures if you've got two different quantum field theories for the two lump positions, so you're in trouble. So, actually, technically, you are in trouble. So what I try to do is say, "Well, how do you estimate the error or the uncertainty, or whatever it is," and you do a little calculation and you come to a measure of what this trouble is, how big is it, and it's like an uncertainty in the energy of the system.

1:12:52 RP: And then I say, "Well, it's a bit like an unstable particle." And what you find is that for an unstable nucleus, say, there is an energy uncertainty, which is inversely related to its lifetime, and this is standard physics, and this inverse relationship is part of the Heisenberg uncertainty relationship with a... You have time, energy, uncertainty. Okay. You might... It's sort of using it the other way round. So people say if you know the lifetime of the system, what is the uncertainty in the energy. Now, I'm saying that you have an uncertainty in the energy, what's the lifetime? What do I mean by lifetime? Well, the lifetime...

1:13:29 SC: Yeah, what do you mean by lifetime?

1:13:30 RP: Yes, is that it decays into one location or the other.

1:13:34 SC: Now, that's your proposal.

1:13:38 RP: That's my proposal.

1:13:38 SC: That's not what...

1:13:38 RP: I should say that there is a Hungarian physicist called Diósi who had a very similar model before me. He didn't have this particular motivation, so it was more... Or he has a suggestion that you might have for how a superposed state might become one or the other by itself spontaneously, nobody... The point is that it's not somebody coming and looking at it, you see...

1:14:00 SC: Nothing to do with observers.

1:14:01 RP: That's right, nothing to do with observers, or if it's anything, it's observing itself, or something.

1:14:07 SC: But do you think of this as a modification of conventional quantum mechanics or a completion of it? It's not there in the textbooks, right?

1:14:13 RP: It's not in the textbooks, I think it's a modification.

1:14:17 SC: Yeah, okay.

1:14:17 RP: It's going to need a theory. I don't have a theory. It's going to need a revolution in... You see, I think of it something like this. Newton's gravitational theory survived a long time, it worked beautifully and, well, people have started to see things like the motion of Mercury, which didn't quite agree with the theory and maybe there was a little extra planet called Vulcan or maybe there's some other exploration or so on. And then Einstein explained it, by not modifying Newton's theory, by putting another term in it or something, by looking at it completely differently.

1:14:52 SC: Right? So I'm a partisan of Everettian quantum mechanics, of many worlds. I've wondered a little bit, although I haven't sat down and gone through the equations, but in Everett, we talk about wave functions branching because of de-coherence, because a system interacts with an environment, and one way... And there's a big challenge in quantum computing to prevent systems from acting and reacting with the environment so that you can maintain quantum coherence. But one thing you can never escape is gravity, right? So everything has a gravitational field. If you're in a superposition of two different places where the gravitational field would be different, I can at least imagine that there are virtual gravitons that are, that in the particle physics language, that in the classical language, we would say slightly different gravitational fields that could interact with the world and cause de-coherence and maybe, just because gravity is mediated by massless particles, there's sort of an inevitable branching of the wave function that leads to collapse in a way that is at least morally similar to what you're talking about.

1:16:00 RP: I think if you do take an Everettian view, you've got to have something else like this to tell you what a world is in a sense, because you want to be able to say it's this world or that world, and then you have to know what a world is, because it's so some quantum mechanical mess, everything entangled with everything else, or is it sort of singled out by having a well-defined geometric spacetime structure? In other words, a well-defined gravitational field.

1:16:25 SC: No, I very much agree. And people who do foundations of quantum mechanics generally don't think too much about general relativity and spacetime, or if they are experts in it, they don't think that the two problems are related, but I do think that that's something people should take more seriously.

1:16:38 RP: Yes, well, you see, there's a lot of talk about quantum gravity. People say, "Well, we want to bring the two subjects together, these two great 20th century revolutions." That's fine, but they usually concentrate on how quantum mechanics might affect spacetime structure or gravity. And this is where you're looking at things on a tiny scale of 10 to the minus 33 cm and 10 to the minus 43 seconds and things like that, which are way off the range of experimental tests. So you might have to build an accelerator of the size of the solar system or something like that, in order to get the energies needed to explore this kind of level. But this is much more optimistic. This is the effect of gravity on quantum mechanics, not of quantum mechanics on gravity, or you could call it gravitized quantum mechanics, you see. [chuckle] And here it's not bad at all. You're just looking at experiments which are on the verge of being done or being tried even now and other experiments coming up, which could well give maybe direct evidence of this.

1:17:44 RP: One of the latest ideas is using Bose-Einstein condensates. These are very, very quantum mechanical states. Very, very cold, almost an absolute zero. And you can play around with them in interesting ways and you could put them in superpositions of two places at once and... Maybe see what happens. It's experimentally just about at the level that can be done.

1:18:09 SC: And you've gone further than that, you've suggested it happens in our brains...

[laughter]

1:18:15 RP: Yeah. Yes. Well, that's...

1:18:18 SC: For the audience we should mention that in part you've done this in collaboration with Stuart Hameroff, who is in the room right now.

[chuckle]

1:18:26 SC: You can say hi, Stuart.

1:18:26 RP: Yes, hi Stuart.

1:18:26 Stuart Hameroff: Hello, everybody.

1:18:27 SC: He is there. So which came first? Your consciousness thoughts, as it were, or your quantum mechanics thoughts? Or when did they get together?

1:18:37 RP: Well, you see, the quantum mechanics thoughts came first. But not that long before, because I mentioned these lecture courses I went to and the Dirac issue about where there is... Seems to be a gap in our present understanding of quantum... He didn't put it like that but that was what I felt. But then I also went to this course on mathematical logic and I had been struck by... I'd had long conversations as an undergraduate with Ian Percival, who we used to discuss these things a lot, and this issue of mathematical logic, we had played around with logical systems and formal logic and so on. And then I had vaguely heard about Gödel's theorem, which seemed to tell us that there are things in mathematics you couldn't prove and I didn't like that idea.

[chuckle]

1:19:27 RP: So I went to the lecture course, which was very revealing. First of all, I learned about Turing machines. What modern computers are based on, if you like. So I knew what the notion of computation was, basically what a Turing machine can do, which is a very beautiful mathematical idea and that there are certain things that are outside computation. So I was aware of this, both the things that you can compute and things which are outside computation or beyond universal computation. And then I learned about the Gödel theorem, and it was not that you... Things you can't see are true or false or something, he said that if you have any logical system, let's say it's something you... The steps, you could put them on a computer. So, let's say they are computational... Computationally checkable.

1:20:21 RP: So you have a line of argument which is meant to be a proof of some mathematical statement. It could be like the Fermat's Last Theorem that Andrew Wiles famously proved, or it could be the Goldbach conjecture, which nobody has proved yet, if it's true. Or it could be simple statements like if you add any two even numbers, you get another even number. So these are statements about an infinite number of things which is rather a critical point. And how do you prove things like that? Now, is it according to following some specific logical system?

1:20:52 RP: Well, what Gödel shows, and Turing had a very... Much nicer way of doing it, but what Gödel showed is that given your system of proof procedures and if you, by understanding what the system does, if you trust the results that it says are true... If you test it on a theorem, say is Goldbach's conjecture or whatever is, suggest a thing. And if it comes out and says yes, done. Then you believe it. And you believe it because you've gone through all the proof procedures and the axioms involved and you still pick the first one and say, "Yeah, that's okay, I trust that one". And the next one you say, "Hmm, I'm not so... Ah, yeah, that's okay, yes, I see that one". And so on, until you're totally convinced that anything using those methods, if it says, "Yes, that's true", you believe it.

1:21:42 RP: Then what Gödel does is he shows a statement which absolutely clearly constructed from this set of rules which is the statement of the same kind about numbers and this statement, you can see if you trust your systems, you're prepared to use your system to get truths, then you must trust this as being true as well.

1:22:04 SC: Right.

1:22:05 RP: So this statement is true on the basis of your same belief system as following the rules and things you come out with. So if you trust the system is giving you only truths, then you must believe the statement. Yet, at the same time, you demonstrate that it's not derivable by the rules. Now, how the hell do we know it's true?

[chuckle]

1:22:26 SC: If you can't prove it eventually by the rules.

1:22:28 RP: If you can't prove it that way.

1:22:29 SC: That way. Yeah.

1:22:30 RP: Yet, you can see it's true by means of the same understandings that you have, that the procedures that you're accepting as giving you proofs. So that... I just... I was blown over by this when I saw it and I thought, "Gosh, this means, as far as I can make out, that our abilities to understand things are not a computation, no matter what it is". Now...

1:22:56 SC: Because we can see truths that... Our minds... You get the result that our minds are not going through a proof procedure within some formal system.

1:23:03 RP: That's right, yes. I mean, you can add that thing to the other one if you like and say, "Okay, here's my new proof procedure," but that's sort of cheating because that wasn't what you started with. And how did you know that other one was true when that... Your things you're supposed to know are true are the things that comes from some algorithm in your head. And so what algorithm can that be if you can supercede it? Now, then I started thinking about, "Well, I don't like to think there's some mysterious... Goodness knows what, comes from the fairies or something, which gives us insights". I think that our brains are constructed according to the same physical laws as everything else in the world. Maybe there's something subtle about the way it's organized. But then I thought, "What about... " Well, I suppose it's Newtonian mechanics. Well, you could put it on a computer, there's a little bit of an issue here, because strictly speaking, the laws that we know are based on the continuum not discreetness.

1:23:57 SC: Right.

1:23:57 RP: But the sort of feeling is that if you had enough precision you're not... You're gonna get close enough. That needs a bit more exploration but I think I'm not going to argue for that. I think that's... The fact that it's continuum as opposed to discreetness I don't think is a big point. It was worth exploring that but that's not what I thought. Okay, what about special relativity? Well, it's still calculations like Newton's things. What about Maxwell's equations? These continuous things, waves and so on? Well, yeah, same issue about their discreteness but that's not probably the real point. You could put it on a computer. And what about general relativity? Again, you could put it on the computer... And we have a really good demonstration of this now with the LIGOs and these calculations...

1:24:42 SC: You need to put it on the computer now, yeah.

1:24:44 RP: Absolutely. I mean, these calculations have come from really delicate understandings and calculations which have produced the signals that you expect to see from blackhole encounters. So we can certainly apply these procedures to Einstein's general relativity. Now, what about Quantum mechanics? Well, you can evolve the Schrodinger equation. Okay, it's difficult 'cause you get all these degrees of freedom, which you have to keep track of and it's... Yeah, but you could still put that on a computer. But then I remember Dirac's piece of chalk, you see, and think well, yeah... There's a gap. And if what we act upon when we're thinking and understanding things, that's the main thing I concentrate on. Our understanding, I would argue, is something which is not a computable process. And the only place I could see where there's a relevant gap in our physical understanding is in this measurement process or the collapse of the wave function, yeah.

1:25:41 SC: The collapse of the wave function? The random part of Quantum Mechanics.

1:25:45 RP: The random part of Quantum Mechanics, that's right. So that's where we don't have a proper theory. So the argument is that whatever is going on in our heads, [chuckle] when it's producing conscious understandings, conscious feelings, conscious whatever, then that's involving this kind of gap in our understanding.

1:26:04 SC: I mean, is... This is probably too much to ask in a brief period of time, but so how do we go from the randomness to some kind of understanding that goes beyond the merely algorithmic?

1:26:16 RP: Well, the argument would be it's not really random.

1:26:18 SC: Oh, okay.

1:26:19 RP: It looks random, but that's because we... That's the level we're at at Quantum Mechanics, there's something deeper going on.

1:26:26 SC: So there's a thumb on the scale of the collapse of the wave function to give us some kind of insight into things that computers can't get?

1:26:33 RP: Yes, as it were... You see, it's the sort of opposite of some view that people have that the collapse of the wave function takes place when some conscious observer sees it.

1:26:44 SC: Right.

1:26:44 RP: So this is the opposite of that. It's not that our consciousness creates the collapse, it's the collapse that creates our consciousness. So the idea was that... Then I wrote this book, "The Emperor's New Mind" where I didn't know much about neurobiology and so on. And I thought, well, I'll learn about it and by the time I get to the end of the book, I'll see where there's a place that you could have Quantum coherence at the level needed. I didn't.

[laughter]

1:27:07 RP: I wrote the book and in the publisher's points, I just made up something at the end which I didn't really believe in and sent the book out hoping that it would maybe stimulate some young people to do Physics or Maths or something. Most of the letters I got were from old retired people.

[laughter]

1:27:22 RP: But then I got one letter which was a little different from both of these, from our friend, Stuart here. Stuart Hameroff told me, "Look, I think you might find these structures more relevant to your concerns than just neuron nerve propagations". Which I thought wasn't that... Didn't have a hope in hell of producing... Preserving coherence 'cause it disturbs the environment and you get these electric fields and stuff which churn everything around and sure, how do you keep that quiet? And so, Stuart, in his letter, described to me these little tubes...

1:28:00 SC: Microtubules.

1:28:00 RP: Nano sized... Nano scale tubes and I thought, "What are these?" I mean, I get lots of crazy letters from people and is this another one? [laughter] And I said, "They look pretty real in the pictures". So I check-up and see, yeah, they're real... Just my ignorance was I didn't know about them. And so, Stuart came over to Oxford, where I was at the time and we got together and tried to make sense of what each other was talking about. And...

1:28:25 SC: I mean, one thing that is a lurking question here, I did have David Chalmers on the podcast, and we talked about the hard problem versus the easy problem of consciousness.

1:28:34 RP: Yeah.

1:28:35 SC: From everything you just said it sounds to me like what you're pointing at are what Chalmers would call the easy problems of consciousness and admittedly no one thinks the easy problems are easy. [chuckle] Some people think the hard problem is impossible, some people think it's easy but everyone thinks the easy problems are hard. Do you think that this way of thinking about Quantum wave function collapse in the brain would help us understand the process of experience? The first person subjective view?

1:29:01 RP: Well, you see... Yeah, I mean, I had a short discussion with David Chalmers, I think after a talk I had given, it was only about 10 seconds discussion. But see, he was complaining 'cause I was saying, basically, the view that Stuart and I have is that whenever one of these collapsed processes takes place, that's where the state decides to be one or the other. I mean, I say, "It decides". You see, that's sort of...

1:29:28 SC: It gets decided, yes.

[chuckle]

1:29:29 RP: What is it, you see? But we call... That is always accompanied by a moment of protoconsciousness. Now you see, protoconsciousness, you think of that as the building blocks out of which consciousness is finally constructed. It doesn't have any purpose at that level but it's the thing out of which consciousness is built. Now, David, I think... Didn't like this, he thought it was still not a solution of the hard problem. Well, whether it is or not just depends on your point of view. But it's saying, "Okay, here is something which goes on in the physical world, out of which consciousness is built". And so it's a point of view, that experience... So you say, there's a sort of... There are many, many element of experience every time these reductions take place. But it's only protoconscious, it doesn't relate it to anything else and doesn't have any purpose, it's... It just does it.

1:30:21 SC: And part of why you're here in Southern California and I get to talk to you is because you have a new institute, is that right? The Penrose Institute. And consciousness is gonna be one of the things they're looking at.

1:30:30 RP: That was certainly one of the big topics, absolutely. No, I think... When I was approached by James Tagg originally, he said "I mean, the idea of it was a little bit scary and I wasn't sure about it". But it seems to me, here is an opportunity to explore things where the mainstream is going in another direction. And one of the obvious places is with the consciousness issue. And Stuart and a few people take this point of view seriously and here is a way of looking at it. It's not the mainstream but it's a serious way of looking at the problem which does have a chance, it seems to me, of yielding some real insights into what consciousness is.

1:31:09 SC: So just tell us a little bit about the Penrose Institute. It's in San Diego, is that right?

1:31:12 RP: Well, it's not anywhere.

1:31:13 SC: It's a state of mind right now?

1:31:15 RP: It's sort of spread out in various places, but San Diego is certainly... Well, that was the place it was initially supposed to be based... Maybe it is, it's not really based anywhere at the moment. It's kind of... More of a concept, rather than having a clear location. Which you know in quantum mechanics, you can have things like that... [chuckle]

1:31:32 SC: Perfectly compatible, yes, exactly. So what's the mission statement of the institute?

1:31:36 RP: Well, let's see, I more or less made it up, but I can't remember it at the moment.

[chuckle]

1:31:41 RP: But the idea is to explore ideas which are not mainstream. But they have to be things where they are experimentally testable. I wanted to make sure about that.

1:31:52 SC: It's not a philosophy institute.

1:31:53 RP: Well, that's right. And it's in danger of people who might say, "Well, that's flaky. This is just some ideas of... Who knows". But the idea is they have to be things where you could think... They needn't be immediately testable but pretty soon. They've got to be really within the range of techniques. And so... But initially, these were on the consciousness thing or maybe things to do... What creativity is or something. But I thought most of my works on physics, I don't really do... I don't know much biology, so that's not really my main interest. And so, I thought we need a strong side, on the physics side but which is exploring these things which are a little offbeat in the sense of not too many people do it. So things like the collapse of the wave function, which is an important one. And I asked Ivette Fuentes, who is somebody I knew who works... She works on unconventional approaches to gravitational wave detection and that's what I knew about.

1:32:52 RP: So you use Bose-Einstein condensates, which is completely on a different scale from LIGO. But it struck me that there's a lot of promise in that idea because these Bose-Einstein condensates are very... They're the most quantum mechanical thing you can think of more or less. And they're practically absolute zero. So you're looking at things which are... Can be really isolated from disturbance from the outside. And I had long discussions with her also about how you might use these things for the collapse of the wave function. So this is actually the major project. It's being done in Nottingham in England at the moment, because that's where her post is... She was in Vienna originally when I was getting her interested in this. And she has a team of people working in Nottingham, and one of the projects... The main project they're really concerned with is looking at these Bose-Einstein condensates and whether you can see whether the collapse of the wave function takes place in a measurable way, and which is objective, not something that depends on somebody looking at it. Really, the system itself does this or that, in a time scale which is consistent with the sort of proposal that I was putting forward.

1:34:10 SC: Well, you know, as a scientist, it's always good to be correct, to say things that are true. But also... Which you certainly have done, but it's also something to be said when you're able to inspire and provoke people into doing interesting things and looking into things in slightly new ways.

1:34:24 RP: That's very much the case, yes. And the hope is, of course, yes, to get other people who might be interested in exploring some of these ideas and taking them seriously. And...

1:34:35 SC: And you've gotten a lot of things named after you along the way, which is pretty good too.

[chuckle]

1:34:41 RP: There are a few of those, yes.

[chuckle]

1:34:44 SC: Alright, Roger Penrose, it's been a great pleasure. Thanks so much for being on the podcast.

1:34:46 RP: Thank you, great pleasure.

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