Lex Fridman PodcastRoger Penrose: Physics of Consciousness and the Infinite Universe | Lex Fridman Podcast #85
EVERY SPOKEN WORD
150 min read · 30,064 words- 0:00 – 3:51
Introduction
- LFLex Fridman
The following is a conversation with Roger Penrose, physicist, mathematician, and philosopher at University of Oxford. He has made fundamental contributions in many disciplines from the mathematical physics of general relativity and cosmology to the limitations of a computational view of consciousness. In his book, The Emperor's New Mind, Roger writes that, quote, "Children are not afraid to pose basic questions that may embarrass us as adults to ask." In many ways, my goal with this podcast is to embrace the inner child that is not constrained by how one should behave, speak, and think in the adult world. Roger is one of the most important minds of our time, so it's truly a pleasure and an honor to talk with him. This conversation was recorded before the outbreak of the pandemic. For everyone feeling the medical, psychological, and financial burden of the crisis, I'm sending love your way. Stay strong. We're in this together. We'll beat this thing. This is the Artificial Intelligence Podcast. If you enjoy it, subscribe on YouTube, review it with five stars on Apple Podcast, support it on Patreon, or simply connect with me on Twitter, @lexfridman, spelled F-R-I-D-M-A-N. As usual, I'll do a few minutes of ads now and never any ads in the middle that can break the flow of the conversation. I hope that works for you and doesn't hurt the listening experience. Quick summary of the ads. Two sponsors: ExpressVPN and Cash App. Please consider supporting the podcast by getting ExpressVPN at expressvpn.com/lexpod and downloading Cash App and using code LEXPODCAST. This show is presented by Cash App, the number one finance app in the App Store. When you get it, use code LEXPODCAST. Cash App lets you send money to friends, buy Bitcoin, and invest in the stock market with as little as $1. Since Cash App does fractional share trading, let me mention that the order execution algorithm that works behind the scenes to create the abstraction of the fractional orders is an algorithmic marvel, so big props to the Cash App engineers for solving a hard problem that, in the end, provides an easy interface that takes a step up to the next layer of abstraction over the stock market, making trading more accessible for new investors and diversification much easier. So again, if you get Cash App from the App Store or Google Play and use the code LEXPODCAST, you get $10 and Cash App will also donate $10 to FIRST, an organization that is helping to advance robotics and STEM education for young people around the world. This show is sponsored by ExpressVPN. Get it at expressvpn.com/lexpod to get a discount and to support this podcast. I've been using ExpressVPN for many years. I love it. It's easy to use. Press the big power on button and your privacy is protected. And, if you like, you can make it look like your location's anywhere else in the world. I might be in Boston now, but I can make it look like I'm in New York, London, Paris, or anywhere else. This has a large number of obvious benefits. Certainly, it allows you to access international versions of streaming websites like the Japanese Netflix or the UK Hulu. ExpressVPN works on any device you can imagine. I use it on Linux, shout out to Ubuntu, Windows, Android. But it's available everywhere else too. Once again, get it at expressvpn.com/lexpod to get a discount and to support this podcast. And now here's my conversation with Roger Penrose.
- 3:51 – 9:43
2001: A Space Odyssey
- LFLex Fridman
You mentioned in conversation with Eric Weinstein on the Portal podcast that 2001: Space Odyssey is your favorite movie.
- RPRoger Penrose
(laughs)
- LFLex Fridman
Which aspect, if you could mention, of its representation of artificial intelligence, science, engineering connected with you?
- RPRoger Penrose
There are all sorts of scenes there which are so am- amazing. And how the science was so well done, I mean people say, "Oh, no, Interstellar it's the- this amazing mo- which is the most scientific movie," but I thought it's another patch on 2001. I mean, 2001, they- they really went into all sorts of details regarding, you know, getting the free fall well done and everything. I thought it was extremely well done.
- LFLex Fridman
So just the details were-
- RPRoger Penrose
Yeah.
- LFLex Fridman
... me- mesmerizing in terms of just-
- RPRoger Penrose
And also things like the scene where at the beginning they have these ance- sort of human ancestors which are sort of-
- LFLex Fridman
Right.
- RPRoger Penrose
Um, or sort of apes.
- LFLex Fridman
The m- the monolith.
- RPRoger Penrose
Apes becoming humans. Yes. And, uh, well it's the one where he throws the bone up into the air and then it becomes this... I mean there's, that's an amazing sequence there.
- LFLex Fridman
What do you make of the monolith? Does it ha- have any scientific or philosophical meaning to you? This kind of thing that sparks innovation?
- RPRoger Penrose
The monolith? Not really. (laughs)
- LFLex Fridman
(laughs)
- RPRoger Penrose
That comes from Arthur C. Clarke.
- LFLex Fridman
This-
- RPRoger Penrose
I was always a great fan of Arthur C. Clarke.
- LFLex Fridman
So it's just a nice plot device?
- RPRoger Penrose
Yeah. Oh, the plot is excellent. Yes, yeah.
- LFLex Fridman
So HAL 9000 decides to get rid of the astronauts because he, it, she believes that they will interfere with the mission.
- RPRoger Penrose
That's right.
- LFLex Fridman
Do you s-
- RPRoger Penrose
Yeah, well, there you are. It's this view... I don't know whether I disagree with it, 'cause in a certain sense it was telling you it's wrong. See, the, the machine seemed to think it was, uh, superior to the human, and so it was entitled to get rid of the human beings and run the show itself.
- LFLex Fridman
Well, do you think HAL did the right thing? Do you think HAL's flawed, evil? Or if we think about systems like HAL, would we want HAL to do the same thing in the future? What was the flaw there?
- RPRoger Penrose
Well, you're basically ques- touching on questions, you see. Is one supposed to believe that HAL was actually conscious?I mean, it was played rather that way, as though HAL was a, a conscious being.
- LFLex Fridman
Because HAL showed some pain, uh, uh, some cogni- HAL appeared to be cognizant of its, of what it means to die.
- RPRoger Penrose
Yes. Yes, I think that's-
- LFLex Fridman
And therefore, had that-
- RPRoger Penrose
... true, yes.
- 9:43 – 23:45
Consciousness and computation
- LFLex Fridman
the thing you mentioned about HAL is the intuition that a lot of the people, at least in the artificial intelligence world, had and have, I think... they don't make it explicit, but that if you increase the power of computation, naturally, consciousness will emerge.
- RPRoger Penrose
Yes, I think that's what they think. But basically, that's 'cause they can't think of anything else.
- LFLex Fridman
Well, that's right.
- RPRoger Penrose
And so it's a reasonable thing. I mean, you think what does the brain do? Well, it does do a lot of computation. I think most of what you actually call computation is, is done by the cerebellum. I mean, this is one of the things that people don't much mention. I mean, I come to this subject from the outside, and certain things strike me which you hardly ever hear mentioned. I mean, you hear it mentioned about the left/right business, the-
- LFLex Fridman
(laughs)
- RPRoger Penrose
... how you move your right arm, that's your-
- LFLex Fridman
Yes.
- RPRoger Penrose
... the left side of the brain and-
- LFLex Fridman
Yeah.
- RPRoger Penrose
... and so on and all that sort of stuff. And it's more than that. If you... you have these plots of different parts of the brain. Th- there are two of these. These things are called the homunculi, which you see these pictures of a distorted human figure-
- LFLex Fridman
(laughs)
- RPRoger Penrose
... and, uh, showing different parts of the brain controlling different parts of the body. And it's not simply things like, okay, the right hand is controlled and sense- both sensory and motor on the left side, left hand on the right side. It's more than that. Vision is at the back, basically. Your feet at the top. And it's as though it's about the worst organization you can imagine.
- LFLex Fridman
(laughs) Right. Yeah.
- RPRoger Penrose
So it can't just be a mistake in nature. There's something going on there. And this is made more pr- pronounced when you think of the cerebellum. The cerebellum has... When I first, first thinking about these things, I w- was told that it had half as many neurons or something like that, comparable. But now they tell me it's got far more neurons than the ce- cerebrum. The cerebrum is this sort of convoluted thing at the top people always talk about. Cerebellum is this thing just looks a bit like a ball of wool right at the back underneath.
- LFLex Fridman
(laughs) Yep.
- RPRoger Penrose
It's got more neurons. It's got more connections. Computationally, it's got much more going on than this from the cerebrum. But as far as we know, although it's slightly controversial, the cerebellum is entirely unconscious. So the actions... You have a pianist who plays incredible piece of music, and you think of... and he moves his little finger into this little key to get it, hit it just the right moment.... does he or she consciously will that movement? No. Okay, the consciousness that's coming in has probably to do with the feeling of, uh, the piece of music that's being performed, and that sort of thing which is going on. But the details of what's going on are controlled, I would think, almost entirely by the cerebellum. That's where you have this precision and the, the really detailed ... Once you get... I mean, you think of a tennis player or something. Does that tennis player think exactly how to, which, which muscle should be moved in what direction and so on? No, of course not. But he or she will maybe think, "Well, if the ball is angled in such a way in that corner, that will be tricky for the opponent." And ex- the details of that are all done largely with the cerebellum because that's where all the precise motions ... But it's unconscious.
- LFLex Fridman
So why is it interesting to you that so much computation is done in the cerebellum and yet is unconscious?
- RPRoger Penrose
Because it doesn't, it's- it's the view that somehow it's computation-
- LFLex Fridman
Ah.
- RPRoger Penrose
... which is producing the consciousness. And it's here you have an incredible amount of computation going on, and as far as we know, it's completely unconscious. So why, what's the difference? And I think it's an important thing. What's the difference? Why has the cerebrum got all this very peculiar stuff that ... very hard to see on a computational perspective, like having the, everything have to cross over onto the other side and do something which looks completely inefficient. And you've got funny things like the frontal lobe and the preta- whatever you call the lobes. And the place where they come together-
- LFLex Fridman
Mm-hmm.
- RPRoger Penrose
... you have the different parts. The control, you see, one to do with motor and the other to do with sensory. And they're sort of opposite each other rather than being connected by ne- by ... It's not as though you've got electrical circuits. There's something else going on there. So it's, i- i- it just the idea that it's like a complicated computer just seems to me to be completely missing the point. There must be a lot of computation going on, but the cerebellum seems to be much better at doing that than the cerebrum is.
- LFLex Fridman
So, for sure, I, I think what explains it, it's, is a h- is like half hope and half we don't know what's going on-
- RPRoger Penrose
(laughs) Yeah.
- LFLex Fridman
... and therefore, from the computer science perspective, you hope that a Turing machine can be perfectly-
- RPRoger Penrose
Yeah.
- LFLex Fridman
... can achieve general intelligence.
- RPRoger Penrose
Well, you have this wonderful thing about Turing and, uh, Godel and Church and Curry and various people, particularly Turing, and I guess Post was the other one. These people who developed the idea of what a computation is. And there were different i- ideas of what a computa- it developed differently. I mean, Church's way of doing it was very different from Turing's. But then they were shown to be equivalent. And so the view emerged that what we mean by a computation is a very clear concept. And one of the wonderful things that Turing did was to show that you could have what we call a universal Turing machine. It's, you just have to have a certain finite device. Okay, it has to have an unlimited storage space which is accessible to it, but the actual computation, if you like, is performed by this one universal device. And so the view comes away, well, you have this universal Turing machine, and maybe the, the brain is something like that, a universal Turing machine. And it's got maybe not an unlimited storage, but a huge storage accessible to it. And this model is one which is what's used in ordinary computation, and it's a very powerful model. And the universalness of computation is very useful. You could have some problem and you may not see immediately how to put it onto a computer, but if it is something of that nature, then, uh, there are all sorts of sub-programs and sub-routines when all the... I mean, I learned a little bit of computing when (laughs) I was, when I was a student, but not very much. But, uh, it was enough to get the general ideas.
- LFLex Fridman
And there's something really pleasant about a formal system like that-
- RPRoger Penrose
Yeah.
- 23:45 – 31:37
What does it mean to "understand"
- RPRoger Penrose
the rules.
- LFLex Fridman
So, that's where... I mean, even at that time, that's already where the thought entered your mind that the idea of understanding, or we can start calling it things like intelligence or even consciousness, is outside the rules?
- RPRoger Penrose
Yes. See, as I've always concentrated on understanding. You know, people say... people tell me ￡ point P others, "Well, we know, what about creativity? That's something a machine can't do as creative." Well, I don't know. What is creativity? And I don't know. You know, somebody can put some funny things on a piece of paper and say, "That's creative," and you could make a machine do that. Is it really creative? I don't know. You see, I, I worry about that one. I sort of agree with it in a sense, but it's so hard to do anything with that statement. But understanding, yes, you can. You can make... go...... see that understanding, whatever it is, um, it's very hard to put your finger on it. That's absolutely true.
- LFLex Fridman
Can you try to define or maybe dance around a definition of-
- RPRoger Penrose
(laughs)
- LFLex Fridman
... understanding?
- RPRoger Penrose
To some degree, but I don't... I've often wondered about this. But there is something there which is very slippery. It's something to... like standing back. And it's got to be something, you see... it's also got to be something which was of value to our remote ancestors.
- LFLex Fridman
Right. Yeah.
- RPRoger Penrose
Because I... sometimes I... there's a cartoon which I drew sometimes, showing you how all these... There's a... in the foreground you see this mathematician just doing some mathematical theorem. There's a little bit of a joke in that theorem, but let's not go into that. (laughs) He's trying to prove some theorem and, uh, he's about to be eaten by a saber-toothed tiger-
- LFLex Fridman
(laughs)
- RPRoger Penrose
... who's hiding in the, in the, in the undergrowth, you see. And in the distance, you see his he- his cousins building, uh, growing crops, building shelters, um, domesticating animals. And in the slight foreground, you see they've built a mammoth trap and this poor old mammoth is falling into a pit, you see, and all these people around him are about to grab him, you see. And, and... well, you see, those are the ones who... the quality of understanding which goes with all the... it's not just the mathematician doing his mathematics. This understanding quality is something else which has been of tremendous advantage to us. Not just to us. See, I don't think consciousness is limited to humans.
- LFLex Fridman
Yeah, that's the interesting question. At which point, if it is indeed connected to the evolutionary process-
- RPRoger Penrose
Yeah.
- LFLex Fridman
... at which point did we pick up this, uh-
- RPRoger Penrose
A very hard question. It's certainly... I, I don't think it's primates, you know. You, you see these pictures of African hunting dogs and how they, they can plan amongst themselves how to catch the antelopes, th-... some of these, um, David Attenborough films, I think this probably was one of them, and you could see the, the hunting dogs and they divide themselves into two groups and they go in two routes, two different routes. One of them goes and they sort of hide next to the river and the other group goes around and they start yelping at these... they don't bark, I guess, whatever noise hunting dogs do, the antelopes, and they sort of round them up and they chase them in the direction of the river. And there are the other ones just waiting for them, just to get... because this... when they get to the river it slows them down and so they pounce on them. So they've obviously planned this all out somehow. I've no idea how. And there is some element of conscious planning as far as I can see. I don't think it's just some kind of a... so much of AI these days is done on, what are they called? Bottom-up systems. Is it... what... yeah-
- LFLex Fridman
Right.
- RPRoger Penrose
... where you have neural networks and they, and they... you give them a zillion different things to look at and, and then they sort of ch- ch- can choose one thing over another just because it's seen so many examples and, uh, picks up on little signals which human may not even be conscious of.
- LFLex Fridman
And that doesn't feel like understanding?
- RPRoger Penrose
There's no understanding in that whatsoever.
- LFLex Fridman
(laughs)
- RPRoger Penrose
So-
- LFLex Fridman
Well, you're being a little bit human-centric, so...
- RPRoger Penrose
Well, I, I'm talking about-
- LFLex Fridman
I think I would expe-
- RPRoger Penrose
See, I'm not with the dogs, am I? 'Cause the dogs-
- LFLex Fridman
No, you're not. Sorry, sorry. Not human-centric, but, uh, I misspoke.
- RPRoger Penrose
Yeah.
- LFLex Fridman
Biol- biology-centric. Is it possible that consciousness would just look slightly different and-
- RPRoger Penrose
Well, I'm not saying it's biological 'cause we don't know.
- LFLex Fridman
Right.
- 31:37 – 40:09
What's missing in quantum mechanics?
- RPRoger Penrose
story, which in a sense I haven't finished.
- LFLex Fridman
Yeah.
- RPRoger Penrose
Because I went to these three courses, you see, when I was a graduate student.
- LFLex Fridman
Sure.
- RPRoger Penrose
And so I started to think, "Well, I'm really... I'm a pretty... what you might call a materialist in the sense of thinking that there's no kind of mystical or something or other which comes in from who knows where."
- LFLex Fridman
Are you still that? Are you still throughout your life been a mat-
- RPRoger Penrose
I don't like the word materialist because it suggests we know what material is.
- LFLex Fridman
(laughs)
- RPRoger Penrose
And that's, that is-
- LFLex Fridman
Well put.
- RPRoger Penrose
...is a bad word because-
- LFLex Fridman
But there's no mystical...
- RPRoger Penrose
It's not some mystical something which is not sci- not treatable by science.
- LFLex Fridman
That's so beautifully put, just to pause on that for a second. You're a materialist but you acknowledge that we don't really know what the material is. (laughs)
- RPRoger Penrose
That's right.
- LFLex Fridman
(laughs) That's well put.
- RPRoger Penrose
I mean, I, I like to call myself a scientist I suppose, but it means that, uh... Yes, well you see, the question goes on here. So I began thinking, "Okay, if consciousness or understanding is something which is not a computational process, what can it be?" And I knew enough from my undergraduate work, I knew about ma- Newtonian mechanics, and I knew, um, how basically you could put it on a computer. There is a fundamental issue which, is it important or not that computation depends upon discrete things, so using discrete elements, whereas the physical laws depend on the continuum. Now, is this something to do with it? Is it the fact that we use the continuum in our physics and if we model our physical system, we use discrete systems like ordinary computers? I came to the view that that's probably not it. I might have to retract on that someday, but the view was no, you, you can get close enough. Uh, it's not altogether clear, I have to say. But you can get close enough. And, you know, I went to this course on by Bondi on general relativity and I thought, "Well, you can put that on a computer." Of course, that was a long time before people... and I've sort of grown up with this, how people have done better and better calculations and they could work out black, about black holes and they can then work out how black holes can interact with each other, spiral around, and what kind of gravitational waves come out. And it's still a very impressive piece of computational work, how you can actually work out the shapes of those signals. And now we have LIGO seeing these signals and they say, "Yeah, there's those black holes spiraling into each other." This is just a vindication of the power of computation in describing Einstein's general relativity.
- LFLex Fridman
So in that case, we can get close. But we... uh, so with computation, we can get close to our understanding of the physics.
- RPRoger Penrose
You can get very close. Now, is that close enough, you see? And then I went to this course by Dirac. Now you see, I think it was the very first lecture that he gave and he was talking about the superposition principle and he said if you have a particle, you usually think of particle can be over here or over there, but in quantum mechanics, it can be over here and over there at the same time. And you have these states which involve a superposition in some sense of, at different locations for that particle. And then he got out his piece of chalk, and some people say he broke it in two as a kind of illustration of how the piece of chalk might be over here and over there at the same time. And he was talking about this, and I... my mind wandered. I don't remember who or what he said. All I can remember, he's just moved on to the next topic and something about energy he'd mentioned, which I had no idea what it had to do with anything. And so I'd been struck with this and worried about it ever since. It's probably just as well I didn't hear his explanation because it was probably one of these things to calm me down and not worry about it anymore.
- LFLex Fridman
(laughs)
- RPRoger Penrose
Whereas in my case, I've worried about it ever since. So I thought maybe that's the catch. There is something in quantum mechanics where the superpositions become one or the other, and that's not part of quantum mechanics. There's something missing in the theory. The theory is incomplete. It's not just incomplete; it's in a certain sense not quite right because if you follow the equation, the basic equation of quantum mechanics, that's the Schrodinger equation, you could put that on a computer too. There are lots of difficulties about how many parameters you have to put in, so on. That can be very tricky, but nevertheless, it is a computational process. Modulo this question about the continuum as before, but it's not clear that makes any difference.
- LFLex Fridman
So our theories of quantum mechanics may be missing the same element that, uh, the Universal Turing Machine is missing about consciousness.
- RPRoger Penrose
Yes, yes. Yeah, this is the view I held is that you need a theory, and that that, what, what people call the reduction of the state or the collapse of the wave function, which you have to have otherwise quantum mechanics doesn't relate to the world we see. To make it relate to the world we see, you've got to break the quan- you've got to break the Schrodinger equation. Schrodinger himself was absolutely (laughs) appalled by this idea. His own equ- his own equation... I mean, that's why he introduced this famous Schrodinger's cat as a thought experiment. He's really saying, "Look, this is where my equation leads you into it."
- LFLex Fridman
Mm-hmm.
- RPRoger Penrose
"There's something wrong," (laughs) something we haven't understood which is basically fundamental.... and so I was trying to put all these things together and said, "Well, it's got to be the non-compute- computability comes in there." And I also can't quite remember right when I thought this, but I said, "It's when gravity is involved in quantum mechanics." It's the combination of those two, and it's that point when the... you have good th- good reasons to believe... This, this came much later. But I have good reason to believe that the principles of general relativity and those of quantum mechanics, most particularly, it's the basic principle of equivalence, which goes back to Galileo. If you fall freely, you eliminate the gravitational field. So you imagine Galileo lay- lay- drawing, thr- uh, dropping his big rock and his little rock from the Leaning Tower. Whether he actually ever did that or not is p- pretty irrelevant. (laughs) And as the rocks fall to the ground, you li- have a little insect sitting on one of them looking at the other one, and it seems to think, "Oh, there's no gravity here." Of course, it hits the ground and then it realize something's different's going on. But when it's in free fall, the gravity has been eliminated. Galileo understood that very beautifully. You can see his won- wonderful examples of fireworks, and you see the fireworks, and explode, and you see this sphere of sparkling fireworks just remains a sphere as it falls down as though there were no gravity. So he understood that principle, but he couldn't make a theory out of it. Einstein came along, used exactly the same principle, and that's the basis of Einstein's general theory of relativity. Now, there is a conflict. This is something I did much, much later, so this wasn't, uh, those days. Much, much later. You can see there is a basic conflict between the principle of superposition, the thing that Dirac was talking about, and the principle of general covari- no, well, principle of equivalence. Gravitational field's equivalent to an acceleration.
- LFLex Fridman
Can you pause for a second? What is the principle of equivalence?
- RPRoger Penrose
It's this Galileo principle that you can eliminate... at least locally, you have to be in a, a, a small neighborhood 'cause, you see, if you had people dropping rocks all around the world somewhere, you can't get rid of it all at once. But in the local neighborhood, you can eliminate the gravitational field by falling freely with it. And we now see it with astronauts and they don't f-... you know, the earth is right there. You can see the great globe of the earth right beneath them. (laughs) But they don't care about it. They... as far as they're concerned, there's no gravity.
- LFLex Fridman
Mm-hmm.
- RPRoger Penrose
They fr- fall freely with- in the gravitational field and that gets rid of the gravitational field. And that's the principle of equivalence.
- LFLex Fridman
So what's the... what's the contradiction? What's the tension with superposition and equivalence?
- 40:09 – 44:13
Whatever consciousness is, it's not a computation
- RPRoger Penrose
it is a complicated story, so, so, you know, people think, "Oh, I'm drifting away from the point," or something.
- LFLex Fridman
No.
- RPRoger Penrose
But I think it is a complicated story. So what I'm trying to say... I mean, I tried to put it in a nutshell, and it's not so easy. I'm trying to say that whatever consciousness is, it's not a computation.
- LFLex Fridman
Yes.
- RPRoger Penrose
Or it's not a physical process which can be described by computation.
- LFLex Fridman
But it nevertheless could be... So one, one of the interesting models that you've proposed is the orchestrated objective reduction.
- RPRoger Penrose
Yes.
- LFLex Fridman
Which is st-
- RPRoger Penrose
Well, you see, that's going from there, you see? So I say I have no idea. So I wrote this book. Through my s- scientific career, I thought, "You know, when I'm retired, I'll have enough time to write a, a sort of popular-ish book which I will explain my ideas and puzzles, what I like, beautiful things about physics and mathematics, and this puzzle about computability and consciousness," and so on. And in the process of writing this book... Well, I thought I'd do it when I was retired. I didn't actually. I wa- didn't wait that long because there was a radio discussion between Edward Fredkin and Marvin Minsky.
- LFLex Fridman
Hmm.
- RPRoger Penrose
And they were talking about what computers could do, and they were entering, entering a big room. They imagined entering this big room. At the other end of the room, two computers were talking to each other. And as you walk up to the computers, they will have communicated to each other more ideas, concepts, things, than the entire human race had ever commuted... done. (laughs)
- LFLex Fridman
Yes.
- RPRoger Penrose
So I thought, "Well, I know where you're coming from," (laughs) "but I just don't believe you. There's something missing." That's... it's not com- that... so I thought, "Well, I should write my book." And so I did. It was, uh, roughly the same time Stephen Hawking was writing his, uh, Brief History of Time, and, uh-
- LFLex Fridman
In the '80s at some point. The book you're talking about is The Emperor's New Mind.
- RPRoger Penrose
Emperor's New Mind, that's right.
- LFLex Fridman
Which... and both are, are incredible books. Uh, the Brief History of Time and Emperor's New Mind.
- RPRoger Penrose
Yes. It was quite interesting 'cause he got... he told me he'd got, um, Carl Sagan, I think, to write a forward-
- LFLex Fridman
That's a good get. (laughs)
- RPRoger Penrose
... to the book, you see. So I thought, "Gosh, I... what am I gonna do? I'm gonna have to... (laughs) I'm not gonna get anywhere unless I get somebody." So I said, "Oh, I know Martin Gardner, so I wonder if he'd do it." So he did, and he did a very nice forward.
- LFLex Fridman
So that... so that's an incredible book, and some of the, uh, this is the same people you mentioned, Ed Frankin, which, uh, I guess f- of, uh, expert systems fame, and Minsky, of course, people know in the AI world. But they represent the artificial intelligence world-
- RPRoger Penrose
Absolutely, that's right.
- LFLex Fridman
... that do hope and dream that AIs, intelligences-
- RPRoger Penrose
That's right.
- LFLex Fridman
... is primarily
- RPRoger Penrose
Well, you see, it was my thinking, "Well, you know, th- I see where they're coming from," and I... from that perspective-
- LFLex Fridman
I disagree. Oh.
- RPRoger Penrose
Yeah, you're right. But I... that's not my perspective, so I thought I had to say it. And as I was writing my book, you see, I thought, "Well, I don't really know anything about neurophysiology. What am I doing writing this book?" So I started reading up about neurophysiology, and I read up and I think, and I was trying to find out, well, how it is that nerve signals could possibly preserve quantum coherence. And all I read is that the sig- um, electrical signals which go along the nerves create, um...... affects through the brain and there's no chance you can isolate it. (laughs) So I thought, "This is hopeless." So I come to the end of the book and I more or less give up. I just think of something which I didn't believe in, that maybe this is a way around it, but no. And then you say, I thought, "Well, maybe this book will at least stimulate young people to do science or something." And I got all these letters from old retired people instead. (laughs) It's the only people who could have had time to read my book. (laughs)
- LFLex Fridman
So, th- I mean, but-
- RPRoger Penrose
Except for Stuart Hameroff.
- LFLex Fridman
Ex- except for Stuart Hameroff. Yeah.
- 44:13 – 1:02:57
Source of consciousness in the human brain
- RPRoger Penrose
- LFLex Fridman
So y- I mean, fundamentally you were searching for the source of... a- a- non-computable source of consciousness within the human brain-
- RPRoger Penrose
Yeah.
- LFLex Fridman
... in the biology. And so-
- RPRoger Penrose
Yes.
- LFLex Fridman
... what are mar- (laughs) if I may ask, what are microtubules?
- RPRoger Penrose
(laughs) Well, you see, I, I was ignorant in what I'd read. I never came across them in, in, in, in the books I looked at. Perhaps I only read rather superficially, which is true. But I didn't know about microtubules. Stuart... I think one of the things he wa- that impressed him about them was when you see pictures of mitosis, that's a cell dividing, and you see all the chromosomes. And the chromosomes get... they're get... all get lined up and then they get pulled apart. And so th- as the cell divides, the... half the chromosomes go... you know, ha- they, well, they divide into the two parts and they go two different ways. And what is it that's pulling them apart? Well, those are these little things called microtubules. And so he started to get interested in them. And he formed the view, when he was... ha- his day job or night job or whatever you call it, is to put people to sleep.
- LFLex Fridman
Mm-hmm.
- RPRoger Penrose
Except he doesn't like calling it sleep because it's different. General anesthetics-
- LFLex Fridman
Mm-hmm.
- RPRoger Penrose
... in a reversible way. So you want to make s- sure that they don't experience the pain that would otherwise be something that they feel. And consciousness is turned off for a while and it can be turned back on again. So it's crucial that you can turn it off and turn it on. And what do you do when you're doing that? What do general anesthetic gases do? And see, he formed the view that it's the microtubules that they affect. And the details of, of why he formed that view is not altogether clear to me, but there... but there's an interesting story he keeps talking about. But I f- found this very exciting because I thought these structures, these little tubes which inhabit pretty well all cells, it's not just neurons, uh, apart from red blood sessil- uh, red blood cells, they inhabit pretty well all the other cells in the body. But they're not all the same kind. You get different kinds of microtubules. And the ones that excited me the most, and this is... may still not be totally clear, but the ones that excited me most were the ones that... the only ones that I knew about at the time because they were... they're very, very symmetrical structures. And I had reason to believe that these very symmetrical structures would be much better at preserving a quantum state, quantum coherence, preserving the thing without... you just need to c- preserve certain degrees of freedom without them leaking into the environment. Once they leak into the environment, you're lost. So you've got to preserve these quantum states at a level which the state reduction process comes in, and that's where I think the non-computability comes in, and it's the measurement process in quantum mechanics, what's going on.
- LFLex Fridman
So something about the, uh, th- the measurement process and what's going on, something about the structure of the microtubules.
- RPRoger Penrose
Yes.
- LFLex Fridman
Your intuition says, "May- maybe there's something here. Maybe this kind of structure allows for the, the, the mystery of the quantum mechanics."
- RPRoger Penrose
There was a much better chance, yes. It just struck me that partly it was the symmetry.
- LFLex Fridman
Right.
- RPRoger Penrose
Because there is a feature of, of symmetry you can produ- pre- preserve quantum coherence much better with symmetrical structures. And so there is a good reason for that. And that impressed me a lot. I didn't know the difference between the A lattice and B lattice at that time, which could be important. (laughs) Now, that couldn't... that's, see, which isn't talked about much.
- LFLex Fridman
But that's some... in some sense details. We've got to take a step back just to say-
- RPRoger Penrose
Yeah, yeah.
- LFLex Fridman
... in case people are not familiar.
- RPRoger Penrose
Yeah, yeah.
- LFLex Fridman
So this, this, this was, um, called the orchestrated objective reduction idea or Orch OR, which is a biological philosophy of mind that postulates that consciousness originates at the quantum level inside neurons. So that has to do with your search for where w- where is it coming from. So that's counter to the notion that consciousness might arise from the computation performed by the synapses.
- RPRoger Penrose
Yes. I think-
- LFLex Fridman
So-
- RPRoger Penrose
... the, the key point... See, sometimes people say it's qu- because it's quantum mechanical. It's not just that. You see, it's, it's more outrageous than that. You see, this is one reason I think we're so far off from it-
- LFLex Fridman
Mm-hmm.
- RPRoger Penrose
... because we don't even know the physics right. You see, it's not just quantum mechanics. People say, "Oh, you know, quantum systems and biological structures." No. Well, you're s- starting to see that some basic biological s- systems does depend on quantum s- I mean, well, y- in the first place, all of chemistry is quantum mechanics. People got used to that, so they don't count that. (laughs) So they said, "Let's not count quantum qu- que- chemistry. We sort of got the hang of that," they think. But you have quantum effects which are not just chemical in photosynthesis. And this is one of the striking things in the last several years, that photosynthesis seems to be...... a basically quantum process, which is not simply que- chemical. It's using quantum mechanics in a very basic way, so you could start saying, "Oh, well, if photosynthesis is based on quantum mechanics, why not, uh, behavior of neurons and things like that?" Maybe there's something which is a bit like photosynthesis in that respect. But what I'm saying is even more outrageous than that, because those things are talking about conventional quantum mechanics. Now, my argument says that conventional quantum mechanics, if you're just following the Schrödinger equation, that's still computable. So you've got to go beyond that. So you've got to go to where quantum mechanics goes wrong, in a certain sense. Y- you have to be a little bit careful about that, because the way people do quantum mechanics is a sort of, um, mixture of two different processes. One of them is the Schrödinger equation, which is a- an equation th- Schrödinger wrote down, and it tells you how the sys- the state of a system evolves. And it evolves according to this equation, completely deterministic, but it evolves into ridiculous situations. And this was what Schrödinger was very much pointing out with his cat. He said, "You follow my equation," that's Schrödinger's equation, "and you could say that you have to... Your cat, ca- a cat which is dead and alive at the same time."
- LFLex Fridman
Mm-hmm.
- RPRoger Penrose
That would be the evolution of the Schrödinger equation, would lead to a state which is the qu- cat being dead and alive at the same time. And he's more or less saying this is an absurdity. People now, they say, "Oh, well, Schrödinger said you can have a cat which is dead and alive." It's not that. You see, he was saying, (laughs) this is an absurdity. There's something missing, and that the reduction of the state, or the collapse of the wave function, or whatever it is, is something which is- has to be understood. It's not following the Schrödinger equation. It's not the way we conventionally do quantum mechanics. There's something more than that, and it's easy to quote authority here because Einstein, (laughs) at least three of the greatest physicists of 20th century, uh, who were very fundamental in developing quantum mechanics, Einstein one of them, Schrödinger another, Dirac another. You have to look carefully at Dirac's writing 'cause he didn't tend to s- say this out loud very much 'cause he was very cautious about what he said. You find the right place and you see he says quantum mechanics is a provisional theory. We need something which explains the collapse of the wave function. We need to go beyond the theory we have now. I happen to be one of the kinds of people, there are many, there is a whole group of people, they're all considered to be a bit, you know, a bit mavericks, who believe that quantum mechanics needs to be modified. There's a small minority of those people, which are already a minority, who think that the way in which it's modified has to be with gravity, and there is an even smaller minority of those people who think it's the particular way that I think it is, you see. (laughs) So it's-
- LFLex Fridman
So those are the quantum gravity folks, but what's, what's-
- 1:02:57 – 1:22:05
Infinite cycles of big bangs
- RPRoger Penrose
- LFLex Fridman
In your 2010 book, Cycles of Time, you suggest that another universe may have existed before the Big Bang. Can you describe this idea? First of all, what is the Big Bang? Sounds like a funny word.
- RPRoger Penrose
Yes.
- LFLex Fridman
And what, uh, may have been there before it?
- RPRoger Penrose
Yes. Just as a matter of terminology, I don't like to call it another universe, 'cause when you have another universe, you think of it kind of quite separate from us. But these things, they're not separate. Now, the Big Bang conventional theory... See, I was actually brought up (laughs) in the sense of when I started getting interested in cosmology, there was a thing called the Steady State model, which was sort of philosophically very interesting. And there wasn't a Big Bang in that theory, that somehow new material was created all the time in the form of hydrogen, and the universe kept on expanding and expanding and expanding, and there was room for more hydrogen. It was a rather philosophically nice picture. It was disproved when the Big Bang... Well, when I say the Big Bang, this was theoretically discovered by people trying to solve Einstein's equations and apply it to cosmology. Einstein didn't like the idea. He liked an i- a universe which was there all the time.
- LFLex Fridman
Okay.
- RPRoger Penrose
And he had a model which they- which there all the time. But then there was this discovery, accidental discovery, very important discovery of this microwave background. And if you, you know, there's the crackle on your television screen, which is- is already just sensing this (laughs) microwave background, which is coming at us from all directions. And you can trace it back and back and back and back. And it came from a very early stage of the universe. Well, it's part of the Big Bang theory. The Big Bang theory was when people tried to solve Einstein's equations, they really found you had to have this initial state where the universe... It was used to be called the primordial atom and things like this. Th- there's Friedmann and Lemaître. Friedmann was a Russian, Lemaître was a Belgian. And they independently... Well, basically Friedmann first. And Lemaître talked about the initial state, which is a very, very concentrated initial state which seemed to be the origin of the universe.
- LFLex Fridman
Primordial atom. That's a nice-
- RPRoger Penrose
Primordial atom is what he called it. Yes.
- LFLex Fridman
Beautiful term.
- RPRoger Penrose
And then it became... Well, Fred Hoyle used the term Big Bang in a kind of derogatory sense.
- LFLex Fridman
Yeah.
- RPRoger Penrose
He said, "Well, didn't "
- LFLex Fridman
Just like with the Schrodinger and the cats.
- RPRoger Penrose
(laughs) Yeah.
- LFLex Fridman
Right?
- RPRoger Penrose
Yes. It's like sort of, it c- pick, got picked up on, whereas it wasn't his intention originally. (laughs) But it then, the evidence piled up and piled up. And my, one of my friends that I learned a lot from when I was in Cambridge was Dennis Sharma. He was a great proponent of Steady State, and then he got converted. He said, "No, I'm sorry." I had a great respect for him. He went around lecturing, said, "I was wrong. The Steady State model doesn't work. There was this Big Bang." And this microwave background that you see... Okay, it's not actually quite the Big Bang when I say not quite. It's about 380,000 years after the Big Bang, but that's what you see. But then you have to have had this Big Bang before it in order to make the equations work. And it works beautifully, except for one little thing, which is this thing called inflation, which people had to put into it to make it work. When I first heard of it, I didn't like it at all.
- LFLex Fridman
What's inflation?
- RPRoger Penrose
Inflation is that in the first... I'm gonna give you a very tiny number. Think of a second. That's not very long. Now, I'm gonna give you a fraction of a second, one over a number. This number has 32 digits between... Well, let's say between 36 and 32 digits. Tiny, tiny time between those two tiny ridiculous seconds, fraction of a second, the universe was supposed to have expanded in this exponential way, an enormous way for no pater- patent reason. You had to invent a particular thing called the inflaton field to make it do it. And I thought, "This is completely crazy." There are reasons why people stuck with this idea. You see, the thing is that I formed my model for reasons which are very fundamental, if you like. It has to do with this very fundamental principle, which is known as the second law of thermodynamics. The second law of thermodynamics says, more or less, things get more and more random as time goes on. Now, another way of saying exactly the same thing is things get less and less random as things go back. As you go back in time, they get less and less random. So, you go back and back and back and back, and the earliest thing you can directly see is this microwave background. What's one of the most striking features of it is that it's random. It has this sp- sp- what you call this spectrum of... Which is, uh, what's called the Planck spectrum of frequencies, uh, different intensities for different frequencies. And there's this wonderful curve due to Max Planck. And what's it telling you? It's telling you that the entropy is at a maximum.... started off at a maximum, and it's going up ever since.
- LFLex Fridman
(laughs)
- RPRoger Penrose
I call that the mammoth in the room. (laughs) I mean, this is a paradox.
- LFLex Fridman
Mammoth in... Yeah, it is. It is.
- RPRoger Penrose
And so people... Why don't cosmologists worry about this? So I worried about it, and then I thought, "Well, it's not really a paradox because you're looking at matter and radiation at a maximum entropy state." What you're not seeing directly in that is the gravitation. It's gravitation which is not thermalized. The gravitation was very, very low entropy, and it's low entropy by the uniformity, and you see that in the microwave too. It's very uniform over the whole sky. I'm compressing a long story into a very short few sentences. (laughs)
- LFLex Fridman
And doing a great job. Yeah.
- RPRoger Penrose
So what I'm saying is that there's a huge puzzle. Why was gravity in this very low entropy state, very highly organized state? Everything else was all random. And that, to me, was the biggest problem in cosmology. The biggest problem, nobody seems to even worry about it. People are saying they solved all the problems, and they don't even worry about it. They think inflation solves it. It doesn't. It can't, because it's, it's just, uh...
- LFLex Fridman
Just to clarify, the- that was your problem with the inflation describing some aspect of-
- RPRoger Penrose
Yes. Well, if la- if-
- LFLex Fridman
... the moments right after the Big Bang?
- RPRoger Penrose
Inflation is supposed to stretch it out and make it all uniform, you see. It doesn't do it because it can only do it if it's uniform already at the beginning. It's- it's... You just have to look at... I can't go into the details. But it doesn't solve it, and it was completely clear to me it doesn't solve it.
- LFLex Fridman
But where does the conformal cyclic cosmology of s-
- 1:22:05 – 1:24:43
Most beautiful idea in mathematics
- LFLex Fridman
Let me ask the question-
- RPRoger Penrose
Yes.
- LFLex Fridman
... what to you is the most beautiful idea in physics or mathematics or the art at the intersection of the two?
- RPRoger Penrose
I'm gonna have to say complex analysis. I might have said infinities and th- one of the most single best beautiful idea I think was the fact that you can have in- infinities of different sizes and so on.
- LFLex Fridman
Mm-hmm.
- RPRoger Penrose
But that's, in a way, I think complex analysis. This goes... It's got so much magic in it. It's a very simple idea. You take these, okay, so if you... you take numbers, you take the integers and then you fill 'em up into the fractions and the real numbers. You imagine you're trying to measure a continuous line, and then you think of how you can solve equations. Then what about X squared equals minus one? Well, there's no real number which has, satisfies that. So you have to think of, well, there's a number called I (laughs) . You think you invent it. Well, in a certain sense, it's there already. But this number, when you add that square root of minus one to it, you have what's called the complex numbers. And they're an incredible system. If you like, you put one little thing in, you put square root of minus one in, and you get how much benefit out of it, all sorts of things that you'd never imagined before. And it's that amazing, all hiding there in putting that square root of minus one in. I think that's-
- LFLex Fridman
So in a sense-
- RPRoger Penrose
... the most magical thing I've seen in mathematics or physics, and it's in quantum mechanics.
- LFLex Fridman
And in quantum mechanics, right.
- RPRoger Penrose
You see, it's there already. You might think, "What's it doing there? Okay, just a nice beautiful piece of mathematics." And then suddenly we see, nope, it's the very crucial basis of quantum mechanics. It's there-
- LFLex Fridman
So on the-
- RPRoger Penrose
... in the way the world works.
- LFLex Fridman
So on the question of whether math is discovered or invented, it sounds like you may be suggesting that partially it's possible that math is indeed discovered.
- RPRoger Penrose
Oh, absolutely. Yes. No, it's more like archeology than you might think.
- LFLex Fridman
(laughs)
- RPRoger Penrose
Yes. Yes.
- LFLex Fridman
So let me ask the most ridiculous, but maybe the most important question. What is the meaning of life?
- RPRoger Penrose
(laughs)
- LFLex Fridman
What gives your life-
- RPRoger Penrose
Oh, God.
- LFLex Fridman
... fulfillment, purpose, happiness, and meaning? Why do you think we're here on this, given all the Big Bang and the infinities of photons that we've talked about?
- RPRoger Penrose
All I would say, I think it's not a stupid question. (laughs)
- LFLex Fridman
(laughs)
- RPRoger Penrose
I mean, there are some people, you know, many of my colleagues who are scientists and they say, "Well, that's a stupid question." Meaning, you know, well, we're just here because things came together and produced life, and so what? (laughs) I think there's more to it. But what there is that's more to it (laughs) , I haven't really much idea.
Episode duration: 1:27:56
Install uListen for AI-powered chat & search across the full episode — Get Full Transcript
Transcript of episode orMtwOz6Db0
Get more out of YouTube videos.
High quality summaries for YouTube videos. Accurate transcripts to search & find moments. Powered by ChatGPT & Claude AI.
Add to Chrome