Martin Rees: Black Holes, Alien Life, Dark Matter, and the Big Bang | Lex Fridman Podcast #305

1. 0:00 – 0:52

   Introduction

   1. MRMartin Rees0:00

      ... there's no reason to think that the ocean ends just beyond your horizon. And likewise, there's no reason to think that the aftermath of our big bang, um, ends just at the bound of what we can see. Indeed, there are quite strong arguments, um, that it probably goes on about 100 times further. And it may even go on so much further that, uh, all combinatorials are replicated and, uh, there's another set of people like us sitting in a, in a room like this.

   2. LFLex Fridman0:30

      The following is a conversation with Lord Martin Rees, emeritus professor of cosmology and astrophysics at Cambridge University and co-founder of The Center For The Study of Existential Risk. This is the Lex Fridman podcast. To support it, please check out our sponsors in the description and now, dear friends, here's Martin Rees.

2. 0:52 – 9:22

   Understanding the universe

   1. LFLex Fridman0:52

      In your 2020 Scientific American article, you write that, quote, "Today, we know that the universe is far bigger and stranger than anyone suspected." So what do you think are the strangest, maybe the most beautiful or maybe even the most terrifying things lurking out there in the cosmos?

   2. MRMartin Rees1:11

      Well, of course, we're still groping for any detailed understanding of the remote parts of the universe, but of course, what we've learnt in the last few decades is really two things. First, we've understood that the universe had an origin about 13.8 billion years ago in a so-called big bang or hot dense state whose very beginnings are still shrouded in mystery. And also, we've learned more about the extreme things in it, uh, black holes, neutron stars, explosions of various kinds, and one of the most potentially exciting discoveries in the last 20 years, mainly the last 10, has been the realization that most of the stars in the sky are orbited by retinues of planets just as the sun is orbited by the Earth and the other familiar planets. And this, of course, makes the night sky far more interesting. What you see up there aren't just points of light, but they're planetary systems and that raises a question, could there be life out there? And so that is an exciting problem for the 21st century.

   3. LFLex Fridman2:16

      So when you see all those lights out there, you immediately imagine all the planetary worlds that are around them and they potentially have all kinds of different lives, living organisms, life forms or different histories.

   4. MRMartin Rees2:31

      Well, that, that we don't know at all. We know that these planets are there. We know that they have masses and, um, orbits rather like the planets of our solar system, but we don't know at all if there's any life on any of them. I mean, it's entirely logically possible that life is unique to this Earth, doesn't exist anywhere. On the other hand, uh, it could be that the origin of life is something which happens routinely given conditions like the young Earth. In which case, there could be literally billions of places in our galaxy where some sort of biosphere has evolved. And, uh, settling, um, where the truth lies between those two extremes is a challenge for the coming decades.

   5. LFLex Fridman3:12

      (inhales deeply) So certainly, we're either lucky to be here or very, very, very lucky to be here.

   6. MRMartin Rees3:19

      I guess that's so, yes.

   7. LFLex Fridman3:20

      And that's, that's the difference. (laughs) Uh, where do you fall, your own estimate, your own guess on this question, are we alone in the universe do you think?

   8. MRMartin Rees3:30

      I think it would be foolish to give any firm estimate because we just don't know and that's just a example of how, uh, we are depending on greater observations and also incidentally, in the case of life, we've got to take account of the fact that, uh, as I always say to my scientific colleagues, biology is a much harder subject than physics.

   9. LFLex Fridman3:51

      (laughs)

   10. MRMartin Rees3:51

       And most of the, um, universe that we know about could be understood by physics but, uh, we've got to remember that even the smallest living organism, an insect, is far more complicated with layer on la- layer on complexity, uh, than, uh, uh, the m- most complicated star or galaxy.

   11. LFLex Fridman4:10

       You know, that's the funny thing of, about physics and biology. The dream of physicists in the 20th century and, and maybe this century is to discover th- the theory of everything. And there's a sense by, that once you discover that theory, you will understand everything. If we unlock the mysteries of how the universe works, would you be able to understand how life emerges from that fabric of the universe that we understand?

   12. MRMartin Rees4:39

       Uh, I think the phrase theory of everything is very misleading, um, because it's, uh, used to describe a theory which unifies the, um, three laws of microphysics, electricity, magnetism, the weak interaction with gravity. So it's i- important step forward for particle physicists. But the lack of such a theory doesn't hold up any other scientists. Anyone doing biology or most of physics is not held up at all through not understanding sub-nuclear physics. They're held up because they're dealing with things that are very complicated.

   13. LFLex Fridman5:13

       Mm-hmm.

   14. MRMartin Rees5:14

       And that's especially true of anything biological. So what's holding up biologists is not a lack of a so-called theory of everything, uh, it's the inability to understand things which are very complicated.

   15. LFLex Fridman5:26

       What do you think we'll understand first, how the universe works or how the human body works deeply? Like, from a fundamental deep level?

   16. MRMartin Rees5:35

       Well, I think, um, and perhaps we can come back to it later, that there are only limited prospects of ever being able to understand with our aged human brains the most fundamental theories linking together all the forces of nature. I think that may be a limitation of the human brains. Um, but I also, uh, think that, um, we can, perhaps aided by computer simulations, um, understand a bit more of the complexity of nature.... but, uh, even understanding a simple organism from the atom up is very, very difficult. And I think extreme reductionists have a very misleading perception. They tend to think that, uh, um, in a sense, we are all solutions of Schrödinger's equation, et cetera, um, but that isn't the way we'll ever understand anything. Uh, it may be true that we are reductionists in the sense that we believe that that's the case, we don't believe in any special life force in living things, but nonetheless, no one thinks that we can understand a living thing by solving Schrödinger's equation. To take a- an example which isn't as complicated, lots of people study the flow of fluids like water, why waves break, why flows go turbulent, things like that. This is a serious branch of applied mathematics and engineering. And in doing this, you have concepts of, uh, viscosity, turbulence and things like that. Now, you can understand quite a lot about how water behaves and how waves break in terms of those concepts, but the fact that any breaking wave is a solution of Schrödinger's equation for 10 to the 30 particles, even if you could solve that, which you clearly can't, would not give you any insight. So, the important thing is that every science has its own irreducible concepts in which you get the best explanation. Uh, so it may be in chemistry as things like valence, um, in bi- bio- biology, the concepts in cell biology, um, and in, uh, ecology there are concepts like imprinting, et cetera, and in psychology there are other concepts. So, in a sense, the sciences are like a tall building where you have basic physics, the most fundamental, then the rest are physics, then chemistry, then cell biology, et cetera, all the way up to the, uh, I guess economist in the penthouse and all that.

   17. LFLex Fridman8:09

       (laughs)

   18. MRMartin Rees8:10

       Um, and we have that, um, uh, and that's true in a sense, but it's not true that it's like a building in that it's made unstable by an unstable base. Because if you're a chemist, biologist, or an economist, you're facing challenging problems, but they're not made any worse by uncertainty about subnuclear physics.

   19. LFLex Fridman8:34

       (inhales deeply) And at every level, just because you understand the rules of the game or have a-

   20. MRMartin Rees8:38

       Yeah.

   21. LFLex Fridman8:38

       ... some understanding of the rules of the game doesn't, uh, mean you know what kind of beautiful things that game creates.

   22. MRMartin Rees8:47

       Right. So, uh, if you're interested in, um, birds and how they fly, uh, the- then things like, uh, um, imprinting, the baby on the mother and all that, and, uh, things like that are what you need to understand. Um, you couldn't even in principle-

   23. LFLex Fridman9:05

       Yeah.

   24. MRMartin Rees9:05

       ... solve with Schrödinger's equation how an albatross wanders for thousands of miles in the Southern Ocean and comes back and then coughs up food for its young. Uh, that- that's something we can understand in a sense and, uh, predict the behavior, but it's not because we can solve it on the atomic scale.

3. 9:22 – 18:18

   Human limitations and AI

   1. MRMartin Rees9:22

   2. LFLex Fridman9:22

      You mentioned that there might be some fundamental limitation to the human brain...

   3. MRMartin Rees9:26

      Yes.

   4. LFLex Fridman9:26

      ... that limits our ability to understand some aspect of how the universe works. That's really interesting.

   5. MRMartin Rees9:33

      Mm-hmm.

   6. LFLex Fridman9:33

      That's sad, actually. If- if- if- to- to the degree it's true, it's sad. So, what do you mean by that?

   7. MRMartin Rees9:40

      I would simply say that just as, um, a monkey can't understand quantum theory or even Newtonian physics, um, there's no particular reason why the human brain should evolve to be well-matched to understanding the deepest aspects of reality. And I suspect that there, uh, may be aspects that we are not even aware of and couldn't really fully comprehend. Um, but as an intermediate step towards that, one thing which I think is a very interesting possibility is the extent to which AI can help us. I mean, I think, uh, if you take the example of, uh, so-called theories of everything, one of which is string theory, um, string theory involves very complicated geometry and structures in 10 dimensions. And it certainly, in my view, on the cards that the physics of 10 dimensions, the very complicated geometry, um, may be too hard for a human being to work through, but could be worked through by an AI, um, with the advantage of the huge processing power which enables them to learn world championship chess within a few hours just by watching games. So, there's every reason to expect that these, um, machines could help us to solve these problems. And of course, if that's the way we came to understand whether string theory was right, um, it would be, in a sense, frustrating because you wouldn't get the sort of aha insight which is the greatest satisfaction from doing science. But on the other hand, if, um, a machine churns away at 10-dimensional geometry figuring out all the possible, uh, uh, origamis and wound up in- in extra dimensions, if it comes out at the end, spews out the correct mass of the electron, the fact that there are three kinds of neutrinos, something like that, you would know that there was some truth in the theory. And so we may have a theory which we come to trust because it does predict things that we can observe and check, but we may never really understand the full workings of it to the extent that we do more or less understand, um, how, um, most phenomena can be explained in a fundamental way. Of course, in the case of quantum theory, many people would say, understandably, there's still some mystery. We don't quite understand why it works, but there could be deeper mysteries when we get to these unified theories where there's a big gap between, um, uh, what a computer can-... print out for us at the end, and what we can actually grasp and think through in our heads.

   8. LFLex Fridman12:18

      Yeah. It's interesting that... the idea that there could be things a computer could tell us that is true, and maybe you can even help us understand why it's true, a little bit.

   9. MRMartin Rees12:28

      Yep.

   10. LFLex Fridman12:29

       But ultimately, it's still a long journey to really deeply understand the whys of it, uh...

   11. MRMartin Rees12:35

       Yes. And that's a limitation of our brain.

   12. LFLex Fridman12:37

       We c- we can try to sneak up to it-

   13. MRMartin Rees12:39

       (laughs)

   14. LFLex Fridman12:39

       ... in different ways, given the limitations of our brain. Have you... I've gotten a chance to spend the day at DeepMind, talk to Demis Hassabis. His big dream is to apply AI to the questions of science, certainly to the questions of physics. Have you gotten a chance to interact with him?

   15. MRMartin Rees12:55

       It's... Well, I know him quite well. I've, uh... he's one of my heroes, certainly.

   16. LFLex Fridman12:59

       (laughs)

   17. MRMartin Rees12:59

       And, uh, (laughs) and I remember-

   18. LFLex Fridman13:01

       I'm sure he would say the same.

   19. MRMartin Rees13:02

       ... uh, and, and I remember the, the first time I met him. He said that, uh, he was like me, he wanted to understand the universe-

   20. LFLex Fridman13:08

       (laughs)

   21. MRMartin Rees13:08

       ... but he thought the best thing to do was to try and develop AI, and then with the help of AI, he'd stand more chance of understanding the universe.

   22. LFLex Fridman13:15

       Yeah.

   23. MRMartin Rees13:15

       And I think he's, he's right about that, so. A- and of course, uh, um, w- a- although we're f- familiar with, uh, the way his, uh, computers play Go and, uh, chess, um, uh, he's already made contributions to science through, uh, uh, understanding protein folding better than the best human chemists. And so, already, he's on the path to showing ways in which computers have the power to learn and do things by having a bit to analyze enormous samples in a short time, uh, to do better th- than humans. And so, um, I think he would resonate with what I just said, that it may be that, uh, in these other fundamental questions, the computers will play a cr- crucial role.

   24. LFLex Fridman13:58

       Yeah. And they're also doing, uh, quantum mechanical simulation of electrons. They're doing-

   25. MRMartin Rees14:03

       Yeah.

   26. LFLex Fridman14:03

       ... uh, control of, uh, high temperature plasmas, fusion reactors.

   27. MRMartin Rees14:08

       Yes. That's a new thing, which is very interesting, that they can suppress the instabilities in these tokamaks, um-

   28. LFLex Fridman14:13

       Yeah.

   29. MRMartin Rees14:13

       ... better than any other way. Yeah.

   30. LFLex Fridman14:15

       And it's just, the march of progress by AIs and science-
4. 18:18 – 25:38

   Dark matter

   1. LFLex Fridman18:18

      Uh, over 20 years ago, you hypothesized that we would solve the mystery of dark matter by now.... so, unfortunately, we didn't-

   2. MRMartin Rees18:27

      No, that's right, yeah (laughs) .

   3. LFLex Fridman18:28

      ... not yet. Um, first, what is dark matter and why has it been so tough to figure out?

   4. MRMartin Rees18:35

      Well, I mean, we- we learned that galaxies and other large-scale structures which are moving around but are, um, prevented from flying apart by ga- by gravity, um, would be flying apart if they only contained the stuff we see-

   5. LFLex Fridman18:52

      Mm-hmm.

   6. MRMartin Rees18:53

      ... if everything in them was shining. And to understand how galaxies formed and why they do remain confined the same size, uh, one has to infer that there's about five times as much stuff producing gravitational forces than the total amount of stuff in the gas and stars that we see. And that stuff is called dark matter. Um, that's its misleading name. It's not dark, it's just transparent, et cetera. Um, and the, uh, most likely interpretation is that it's a swarm of, uh, microscopic particles which have no electric charge and the very small cross sections were hitting each other and hitting anything else. So they swarm around and we- we can detect their collective effects. And when we do computer simulations of how galaxies form and evolve, and how they emerged from the Big Bang, then, uh, we get a nice consistent picture if we put in five times as much mass in the form of these mysterious dark particles. And, for instance, it works better if you think they're non-interacting particles than if you think they're a gas which would have shock waves and things. So we know something about the properties of these but we don't know what they are. And, um, the disappointment compared to my guess 20 years ago, um, is that particles answering this description have not yet been found. It was thought that the big accelerator, the Large Hadron Collider at CERN, which is the world's biggest, might have found a new class of particles which would have been the obvious candidates, and it hasn't. And, uh, um, some people say, "Well, dark matter can't be there," et cetera. But what I would argue is that there's a huge amount of parameter space that hasn't been explored. Um, there are other kinds of particles called axions which behaves largely differently which are a good candidate. Um, and, um, there's a factor of, uh, 10 powers of 10 between the heaviest particles that could be created by the Large Hadron Collider and the heaviest particles which on theoretical grounds could exist-

   7. LFLex Fridman21:04

      Mm-hmm.

   8. MRMartin Rees21:04

      ... without turning into black holes. So there's a huge amount of, uh, possible particles which could be out there as remnants of the Big Bang, um, but which we wouldn't be able to detect so easily. So, um, the fact that we've got new constraints on what the dark matter could be doesn't diminish my belief that it's there in the form of particles because we've only explored a small fraction of parameter space.

   9. LFLex Fridman21:28

      So there's this search, you're (laughs) literally, uh, pun unintended, are searching in the dark here in this giant parameter space of possible particles. You're searching for... I mean-

   10. MRMartin Rees21:41

       Yes.

   11. LFLex Fridman21:41

       ... there could be all kinds of particles that we just don't know.

   12. MRMartin Rees21:44

       The- the- there could be, and the sum is maybe very- very hard to detect. But I think we can hope for, um, some new theoretical ideas because, um, one point which perhaps you'd like to discuss more is about the, uh, very early stages of the Big Bang. Um, and, uh, the situation now is that we have a outlined picture for how the universe has evolved, um, from the time when it was expanding in just a nanosecond right up to the present. And we can do that because after nanosecond the physics of the material is in the same range that we can test in the lab. After a nanosecond, the particles are moving around like those in the Large Hadron Collider. If you wait for one second, they're rather like in the centers of the hottest stars and nuclear reactions produce hydrogen, helium, et cetera which fit the data. So we can with confidence extrapolate back to when the universe was a nanosecond old. Indeed I think we can do it with as much confidence as anything a geologist tells you about the early history of the Earth. And that's huge progress in the last 50 years. But any progress puts in sharper focus, uh, new mysteries. And of course the new mysteries in this context are why is the universe expanding the way it is? Why does it contain this mixture of atoms and dark matter and radiation? And why does it have, uh, um, the properties which allow galaxies to form, being fairly smooth but not completely smooth? And the answer to those questions, I generally believe, to lie in a much, much earlier stage of the universe when conditions were much more extreme and therefore far beyond the stage where we had the footholding experiments. Very theoretical. And so, um, we don't have a- a convincing theory, we just have ideas. Until we have something like string theory or some other clues to the ultra early universe, uh, that's going to remain speculative. So, um, there's a big gap. And to say how big the gap is, um, if we take the observable universe out to a bit more than 10 billion light years, um, then when the universe was a nanosecond old that would have been squeezed down to the size of our solar system, or compressed into that- that volume. But the times we're talking about when the key properties of the universe were first imprinted were times when that entire universe was squeezed down to the size of a tennis ball, or baseball if you prefer, and- and emerged from something microscopic. So it's a huge extrapolation and it's not surprising that since it's so far from our experimental range of detectability, uh, we are still groping for ideas.

   13. LFLex Fridman24:31

       But you think first theory will reach-... into that place, and then experiment will perhaps one day catch up-

   14. MRMartin Rees24:39

       W- well, I think-

   15. LFLex Fridman24:40

       ... or maybe simulation.

   16. MRMartin Rees24:41

       ... i- in a sense it's a combination. I think, uh, what, what we hope for is that, um, uh, there'll be a theory which applies to the early universe but which also has consequences which we can test in our present day universe-

   17. LFLex Fridman24:57

       (laughs)

   18. MRMartin Rees24:57

       ... um, uh, like, um, discovering why neutrinos exist or things like that.

   19. LFLex Fridman25:02

       Mm-hmm.

   20. MRMartin Rees25:02

       And that's the thing which, as I mentioned, w- we may perhaps need a bit of AI to help us to calculate.

   21. LFLex Fridman25:08

       Yeah.

   22. MRMartin Rees25:09

       But, but I think, um, the, the hope would be that, uh, we will have a theory which applies under the very, very extreme earliest days of the universe, but which gains credibility and gains confidence because it also manages to account for otherwise unexplained features of, um, uh, the low-energy world and what people call a standard model of particle physics where there are lots of undetermined numbers, so it may help with that.

   23. LFLex Fridman25:35

       So we're dancing between physics and philosophy a

5. 25:38 – 33:19

   Vast universe

   1. LFLex Fridman25:38

      little bit, but what do you think... What do you think happened before the Big Bang? So this seems... This feels like something that's out of the reach of science.

   2. MRMartin Rees25:48

      It's out of the reach of present science, because science develops, and as the frontiers advance, uh, then new problems come into focus that couldn't even have been postulated before. I mean, if I think of my own career, when I was a student, the evidence for the Big Bang was pretty weak, whereas now it's extremely strong, um, but we are now thinking about the reason why the universe is the way it is and all that. Um, so, uh, I- I would put all these things we've just mentioned in the category of speculative science.

   3. LFLex Fridman26:21

      Mm-hmm.

   4. MRMartin Rees26:21

      Um, and, uh, I don't see a bifurcation between that and philosophy. Um, but of course to answer your question, um, if we do want to understand the very early universe, then we've got to realize that, uh, it may involve even more counterintuitive concepts than quantum theory does, because it's a condition even further away from everyday world than quantum theory is. And remember, our lives, our brains evolved, um, and haven't changed much since our ancestors... our ancestors roamed the African savanna and looked-

   5. LFLex Fridman26:55

      Yeah.

   6. MRMartin Rees26:55

      ... at the everyday world, um, and, uh, it's rather amazing that we've been able to make some sense of the quantum microworld-

   7. LFLex Fridman27:01

      Yes.

   8. MRMartin Rees27:01

      ... and of the cosmos. But, uh, uh, there may be some things which are beyond us, and certainly as we implied there are things that we don't yet understand at all. And, uh, of course one concept we might have to jettison is the idea of three dimensions of space and time just ticking away. There are a lot of ideas. I mean, uh, I think Stephen Hawking had an idea that... talking about w- what s- what happened before the Big Bang, it's like asking what happens if you go north from the North Pole, you know? It- it somehow closes off. That's just one idea.

   9. LFLex Fridman27:35

      Mm-hmm.

   10. MRMartin Rees27:35

       Um, I don't like that idea, but that's a possible one, um, and, uh, uh, and so we just don't know, um, what happened at the very beginning of the Big Bang, were there are many big bangs rather than one, et cetera, um, and, uh, those are issues which, um, we may be able to get some, uh, foothold on from some new theory, um, but even then, um, we won't be able to directly test the theories. But I think, um, it's a heresy to think you have to be able to test every prediction of a theory. Let me give you no- another example. Um, we take seriously what Einstein's theory says about the inside of black holes even though we can't observe them because that theory has been vindicated in many other places, in cosmology, in black holes, gravitational waves, and all those things. Um, likewise, if we had a, a theory which, um, explains some things about the early history of our Big Bang in the present universe, then we would take seriously the inference if it predicted many big bangs, not one, even though we can't predict the other ones. So the example is that we can, uh, take seriously a prediction if it's the consequence of a theory that we believe on other grounds. We don't need to be able to, uh, detect another big bang in order to take it seriously.

   11. LFLex Fridman29:01

       It may not be a proof, but it's a good indication that, uh, this is the direction where the truth lies.

   12. MRMartin Rees29:10

       Yeah, if the theory is getting confidence otherwise.

   13. LFLex Fridman29:12

       Yes. What do you sense? Do you think there's other universes besides our own?

   14. MRMartin Rees29:19

       Uh, the... those sort of well-defined theories which make assumptions about the physics at the relevant time, and this time incidentally is 10 to the power of minus 36 seconds-

   15. LFLex Fridman29:29

       (laughs)

   16. MRMartin Rees29:29

       ... um, or earlier than that, so-

   17. LFLex Fridman29:31

       Yeah.

   18. MRMartin Rees29:32

       ... this tiny sliver of time. And, um, there are some theories, a famous one due to Andrei Linde, um, the Russian cosmo- cosmologist now at Stanford called eternal inflation, um, which did predict, um, an eternal production of new big bangs as it were, and, uh, uh, that's based on specific assumptions about the physics. But those assumptions, of course, are just hypotheses which aren't vindicated. But there are other theories which only predict one big bang. So I think, uh, we should be open-minded and not dogmatic about these, these options until we do understand the relevant physics. But, uh, there are th- these d- different scenarios or very different ideas about, about this. But I think all of them have the feature that physical reality is a lot more extensive than what we can see through our telescope, and I think even most conservative astronomers would say that, because, uh, uh, we can see out with our telescopes to a sort of horizon which is about, uh-... depending on how you measure it, it's maybe 15 billion light years away or something like that. But that horizon of our observations is no more physical reality than the horizon around you if you're in the ocean-

   19. LFLex Fridman30:48

       Hmm.

   20. MRMartin Rees30:49

       ... um, and look at, looking out at- at- at your horizon. There's no reason to think that the ocean ends just beyond your horizon and likewise, there's no reason to think that the aftermath of our Big Bang, um, ends just at the bound of what we can see. Indeed, there are quite strong arguments, um, that it probably goes on about 100 times further. It may even go on so much further that, uh, all common materials are replicated and, uh, there's another set of people like us sitting in a, in a room like this. Um-

   21. LFLex Fridman31:21

       Every possible combination of-

   22. MRMartin Rees31:22

       Yeah. That- that could happen.

   23. LFLex Fridman31:24

       ... oh, boy.

   24. MRMartin Rees31:24

       Uh, th- that's not logically impossible, um, but I- but I think many people would accept that it does go on, um, and contain, um, probably a million times as much stuff as what we can see within our horizon. The reason for that, incidentally, is that if we look as far as we can in one direction and then the opposite direction, then the conditions don't differ by more than one part in 100,000. So, that means if we're part of some finite structure, the gradient across the part we can see is very small.

   25. LFLex Fridman31:56

       Yeah.

   26. MRMartin Rees31:56

       And so that suggests that it probably does go on a lot further and, uh, the best estimates say it must go on at least 20 times further.

   27. LFLex Fridman32:04

       Is that exciting or terrifying to you? Just the spans of it all, the wide ... everything that lies beyond the horizon. Uh, that- that example doesn't even hold for Earth, so it goes way, way farther. And on top of that, just to take your metaphor further with the, on the ocean-

   28. MRMartin Rees32:23

       Yeah.

   29. LFLex Fridman32:24

       ... while we're on top of this ocean, not only can we not see beyond the horizon, we also don't know much about the depth of the ocean-

   30. MRMartin Rees32:32

       That's right. Mm-hmm.
6. 33:19 – 47:12

   Alien life

   1. MRMartin Rees33:19

      much difference. And, uh, uh, well, there's a more general question, of course, about, uh, um, whether, um, the human race as such is something which is of, uh, very special or if on the other hand, um, it's just one of many such species elsewhere in the universe, or indeed existing at different times in our universe.

   2. LFLex Fridman33:44

      Yeah. It- to me it feels, uh, almost obvious that the universe should be full of alien life, perhaps dead alien civilizations, but just the- the vastness of space and-

   3. MRMartin Rees33:58

      Yes.

   4. LFLex Fridman33:59

      ... it just feels wrong to think of Earth as somehow special. It sure as heck doesn't look that special. When you ... the more we learn, the less special it seems. (laughs)

   5. MRMartin Rees34:10

      Well, I- I mean, I don't agree with that as far as- as life is concerned, because, uh, remember that we don't understand how life began here on Earth.

   6. LFLex Fridman34:19

      Yes.

   7. MRMartin Rees34:19

      We don't understand, although we know there are an evolution of simple life to complex life, we don't understand, uh, what caused the transition between complex chemistry and the first, um, replicating, metabolizing entity we call alive.

   8. LFLex Fridman34:35

      Yes.

   9. MRMartin Rees34:35

      That's a mystery, um, and, uh, uh, s- serious physicists are now- and chemists are now thinking about it, but we- we don't know. So, we therefore can't say was it a rare fluke-

   10. LFLex Fridman34:47

       Yeah.

   11. MRMartin Rees34:48

       ... which would not have happened anywhere else, or was it something which, uh, involves the processes would have happened in any other planet where conditions were like they were on young Earth? Um, so w- we can't say that now. Um, I- I think what many of us would indeed bet that probably some kind of life exists elsewhere, but even if, um, you accept that, then, um, there are many contingencies going from simple life to, um, uh, present day life. And- and some biologists like Stephen Jay Gould, uh, thought that if you re-run evolution, you'd end up with something quite different, and maybe life with an intelligent species. So, the, uh, contingencies in evolution, um, may militate against the emergence of intelligence even if life gets started lots of places. Uh, so I think these are still completely open questions, and that's why it's such an exciting time now that we are starting to be able to address these. I mean, I mentioned the, uh, the fact that the origin of life is a question that we may be able to understand, um, and serious people are working on it. It's usually put in the sort of too difficult box. Everyone knew it was important, but they didn't know how to tackle it or what experiments to do. But it's not like that now, and, um, that's partly because of cleverer experiments, but I think most importantly because, um, we are aware that we can look for life in other places, other places in our solar system and of course on the exoplanets around other stars. And, uh, within 10 or 20 years, I think two things could happen which will be really, really important. We might, with the next big telescope, be able to image some of the Earth-like planets around other stars.

   12. LFLex Fridman36:34

       Image, like get a picture?

   13. MRMartin Rees36:36

       Well- well, actually, let me caveat that. It'd take 50 years to get a resolved image-

   14. LFLex Fridman36:41

       (laughs)

   15. MRMartin Rees36:41

       ... but- but- but try to detect the light-... because th- now, of course, the- these exoplanets are detected by their effect on the parent star. They either cause th- their parent star to dim slightly when they transit across in front of it, and so we see the dips, or, uh, their gravitational pull makes the star wobble a bit. So- so most of the- the 5,000-plus planets that have been found around other stars, they've been found indirectly by their effects-

   16. LFLex Fridman37:07

       Yes.

   17. MRMartin Rees37:08

       ... in one of those two ways on the parent star.

   18. LFLex Fridman37:09

       You could still do a pretty good job of estimating size-

   19. MRMartin Rees37:12

       Yeah.

   20. LFLex Fridman37:12

       ... all those kinds of things.

   21. MRMartin Rees37:13

       Size and ma- the size and the mass, you can estimate.

   22. LFLex Fridman37:16

       Oh, nice.

   23. MRMartin Rees37:16

       Um, but- but, uh, um, but- but det- detecting the- the actual light from one of these exoplanets hasn't really been done yet, exactly one or two very- ve- very bright, big planets. And, uh-

   24. LFLex Fridman37:27

       So, maybe, like, James Webb telescope would be able to-

   25. MRMartin Rees37:29

       Well, James Webb may do this, but even better will be, um, the European ground-based telescope called, unimaginatively, The Extremely Large Telescope, which has a-

   26. LFLex Fridman37:39

       (laughs)

   27. MRMartin Rees37:39

       ... 39-meter diameter mirror, 39 meters-

   28. LFLex Fridman37:43

       Yeah.

   29. MRMartin Rees37:43

       ... a mosaic of 800 sheets of glass, and that will collect enough light from one of these exoplanets around a nearby star, um, to be able to, um, separate out its light from that of the star, which is, uh, millions of times brighter, and get the spectrum of the planet-

   30. LFLex Fridman38:01

       Mm-hmm.
7. 47:12 – 1:11:35

   Space exploration

   1. LFLex Fridman47:12

      So, do you think we would more and more, you know, maybe start with some genetic modification and then move to basically cyborgs, increasing integration of electronic systems, computational systems into our bodies and brains?

   2. MRMartin Rees47:27

      This is a theme of, um, uh, my other new book out this year, which is called The End of Astronauts.

   3. LFLex Fridman47:32

      The End of Astronauts.

   4. MRMartin Rees47:33

      And it's co- co-written with my, um, uh, old friend and colleague from Berkeley, Don Goldsmith. And, uh, it's really about, um, the- the role of, uh, human space flight versus sort of robotic space flight. And, um, just to summarize what it says, um, it argues that the, um, practical case for sending humans into space is getting weaker all the time as robots get better and more capable. Robots 50 years ago couldn't do anything very much, but now they could assemble big structures on space or, um, in space or on the moon, and they could probably do exploration. But present ones, uh, on Mars, um, can't actually, um, do the geology, but future AI will be able to do the geology, and already they can dig on Mars. And so, if you want to do exploration of Mars and of course, even more of, um, Enceladus or Europa where you could never send humans, we depend on robots. And they're far, far cheaper, because to send a human to Mars requires feeding them for 200 days on the journey there and bringing them back, and neither of those are necessary for robots. So, the practical case for humans is getting very, very weak. And if humans go, it's only as an adventure, really. And so the line in our book is that, um, uh...... human space flight should be pursued by NASA or public funding agencies, um, because it has no practical purpose, but also because it's specially expensive if they do it, because they would have to be risk-averse in launching civilians into space. We, I can illustrate that by s- noting that the shuttle was launched 135 times, and it had two spectacular failures which each killed the seven people in the crew. Um, and, uh, it had been mistakenly presented as safe for civilians, and there was a woman schoolteacher killed in one of them. You know, it was a big national trauma, and they tried to make it safer still. Um, but if you launch into space just the kind of people prepared to accept that sort of risk, and of course, test pilots and people who go hang-gliding and go to the South Pole, et cetera-

   5. LFLex Fridman50:01

      Yeah.

   6. MRMartin Rees50:01

      ... are prepared to accept, uh, a 2% risk, at least, for a big challenge, then of course you do it more cheaply. And that's why, um, uh, I think, um, human space flight should be left to the billionaires, um, and their sponsors, um, because then the taxpayers aren't paying, and they can launch simply those people who are prepared to accept high risks. Space adventure, not space tourism.

   7. LFLex Fridman50:30

      Yeah.

   8. MRMartin Rees50:30

      And, and, and, uh, we should cheer them on. Um, and, um, uh, as regards where they would go, then, um, low Earth orbit, I suspect, can be done quite cheaply in future. But going to Mars, which is very, very expensive and dangerous for humans, um, the only people who would go would be, um, these, um, adventurers, um, maybe on, on a one-way trip, like some of the early polar explorers and Magellan and people like that, you know, and, and we would cheer them on. Um, and I expect, and I very much hope, that by the end of the century, there will be a small community of such people on Mars, um, living very uncomfortably. Far less comfortably than at the South Pole or the bottom of the ocean or the top of Everest. But they will be there, uh, um, and they won't have a return ticket. Um, but they'll, they'll be there. Um, incidentally, I think it's a dangerous delusion to think, as, uh, Elon Musk has said, that we can have mass emigration from the Earth to Mars to escape the Earth's problems. Um, it's a dangerous delusion because it's far easier to deal with climate change on Earth than to terraform Mars to make it properly habitable to humans. And so there's no Planet B for ordinary risk-averse people, but for these crazy adventurers, uh, then you can imagine that, that they would be trying to live on Mars as, um, as great pioneers.

   9. LFLex Fridman52:03

      (laughs)

   10. MRMartin Rees52:03

       And by the end of the century, then there will be huge advances compared to the present in two things. First, in, in, uh, understanding genetics so as to genetically redesign one's offspring, and secondly, to, uh, use cyborg techniques to, um, implant some, something in our brain, or indeed think about downloading, et cetera. And those techniques will, one hopes, be heavily regulated on Earth on prudentials and ethical grounds, and of course, we are pretty well adapted to the Earth, so we don't have the incentive to do these things in the way they were there. Uh, so, um, our argument is that, um, it'll be those crazy pioneers on Mars using all these scientific advances, which would be controlled here away from the regulators. They will transition into a new post-human species.

   11. LFLex Fridman52:58

       Mm-hmm.

   12. MRMartin Rees52:58

       And so, um, if they do that, and if they tr- transition into something which is electronic eventually, because there may be some limits to the capacity of flesh and blood brains anyways, um, then, um, those electronic entities, um, may not want to stay on a planet like Mars. They may want to go, go away. And so they'll be the precursors of the future, um, evolution of life and intelligence coming from the Earth. Um, and of course, there's one point which perhaps astronomers are more aware of than most people. Most people are aware that we are the outcome of 4 billion years of evolution. Ma- most of them, nonetheless, probably think that we humans are somehow the culmination, the top of the tree. But-

   13. LFLex Fridman53:46

       Yes.

   14. MRMartin Rees53:47

       ... no astronomers could believe that, because astronomers know that the Earth is four and a half billion years old. The sun has been shining for that length of time, but the sun has got 6 billion years more to go before it flares up and engulfs the inner planets. So, the sun is less than halfway through its life, um, and, uh, the expanding universe goes on far longer still. Maybe forever. And I like to quote Woody Allen, who said, "Eternity is very long, especially towards the end." Uh, so, uh, s- so we shouldn't think of ourselves as maybe even the halfway stage-

   15. LFLex Fridman54:20

       Yeah.

   16. MRMartin Rees54:20

       ... in the emergence of, uh, cosmic complexity. And so these entities who are post-cursors, they will go beyond the solar system, and of course, even if there's nothing else out there already, uh, then, then they could, uh, populate the, the rest of the g- the galaxy.

   17. LFLex Fridman54:38

       And maybe eventually meet the others who are out there expanding as well.

   18. MRMartin Rees54:42

       Yeah.

   19. LFLex Fridman54:42

       Expanding, populating.

   20. MRMartin Rees54:44

       Yes, yes, yes.

   21. LFLex Fridman54:44

       With expanded, uh, capacity for life and intelligence, all those kinds of things.

   22. MRMartin Rees54:50

       Well, uh, they, they might. Um, but, um, uh, uh, again, w- all better off because I can't conceive what they'd be like.

   23. LFLex Fridman54:58

       (laughs)

   24. MRMartin Rees54:58

       Um, they won't, they won't be, uh, um, green.... green men and women with eyes on stalks, you know?

   25. LFLex Fridman55:03

       Yeah.

   26. MRMartin Rees55:03

       Maybe something quite different. Um, we, we, we just don't know. Um, but th- there, there is an interesting question, actually, which comes up when I've sometimes spoken to audiences about this topic, that... The question of consciousness and self-awareness. Because, you know, going back to philosophical questions, I mean, it's whether an electronic robot would, uh, be a zombie, or would it be conscious and self-aware? And, um, um, I think there's no way of answering this empirically. Um, and, um, uh, some people think that consciousness and self-awareness is an emergent property in any sufficiently complicated network that there would be.

   27. LFLex Fridman55:40

       Yeah.

   28. MRMartin Rees55:40

       Others say, "Well, maybe it's something special to the flesh and blood that we're made of." We don't know. Um, and in a sense, this may not matter, um, to the way peop- things behave because we... They, they could be zombies and still behave as though they were intelligent. Um, but, uh, I remember after one of my talks, someone came up and said, "Wouldn't it be sad if these future entities, which were the main intelligence in the universe, um, had no self-awareness?" So there was nothing which could appreciate the wonder and mystery of the universe, and the beauty of the universe in the way that we do. Um, and, and so it does perhaps affect one's perspective of whether you welcome or deplore this possible future scenario, depending on whether you think the, the future post-human entities are conscious and have an aesthetic sense or whether they're just zombies.

   29. LFLex Fridman56:38

       And, uh, of course, you have to be humble to realize that self-awareness may not be the highest form of being, that humans have a very strong ego and a very strong sense of identity, like personal identity connected to this particular brain.

   30. MRMartin Rees56:57

       Yeah, yeah.
8. 1:11:35 – 1:22:57

   Future technology

   1. MRMartin Rees1:11:35

   2. LFLex Fridman1:11:36

      Do you know the movie 2001: A Space Odyssey?

   3. MRMartin Rees1:11:39

      Oh, of course, yes. Mm-hmm.

   4. LFLex Fridman1:11:40

      Uh-

   5. MRMartin Rees1:11:40

      But you must be s- too young to have seen that when it came out, obviously.

   6. LFLex Fridman1:11:44

      Uh, yeah, but it's still-

   7. MRMartin Rees1:11:44

      I remember seeing it when it came out, y- yes.

   8. LFLex Fridman1:11:47

      You saw it when it came out?

   9. MRMartin Rees1:11:49

      Yeah, yeah.

   10. LFLex Fridman1:11:49

       You saw-

   11. MRMartin Rees1:11:49

       50 years ago.

   12. LFLex Fridman1:11:50

       ... 60-

   13. MRMartin Rees1:11:51

       Mm-hmm.

   14. LFLex Fridman1:11:51

       ... 60... When was it 60, uh-

   15. MRMartin Rees1:11:53

       It was...

   16. LFLex Fridman1:11:54

       In the '60s.

   17. MRMartin Rees1:11:55

       Yeah. That's right. Mm-hmm.

   18. LFLex Fridman1:11:56

       And-

   19. MRMartin Rees1:11:56

       Still a classic. Mm-hmm. Mm-hmm.

   20. LFLex Fridman1:11:58

       Ah, it's still probably-

   21. MRMartin Rees1:12:00

       I don't know. I- I- I-

   22. LFLex Fridman1:12:00

       ... for me, the greatest AI movie ever made.

   23. MRMartin Rees1:12:03

       Yes, yes. I agree.

   24. LFLex Fridman1:12:04

       Uh, one of the great space movies ever made.

   25. MRMartin Rees1:12:06

       Yes, yes.

   26. LFLex Fridman1:12:07

       So, well, let me ask you a philosophical question since we're talking about robots exploring space, do you think HAL 9000 is good or bad? So for people who haven't watched-

   27. MRMartin Rees1:12:19

       (laughs) Yeah. ... this computer system makes a decision to, uh, basically prioritize the mission that it, it, the ship is on over the humans that are part- Mm-hmm. Yes.

   28. LFLex Fridman1:12:33

       ... of the mission. Uh, do you think HAL is good or evil?

   29. MRMartin Rees1:12:38

       If you ask me probably in that context, it was probably good. But I think you're raising what is, of course, very much a active issue in everyday life, uh, about, uh, the extent to which we should, um, entrust any important decision, uh, to a machine. And, and there again, I'm very worried because I, I think, um, if you are recommended for an operation or not given parole from prison, or even denied credit by your bank, you feel you should be entitled to an explanation. It's not enough to be told that the machine has a more reliable record, um, on the whole than humans have of making these decisions. You-... think you should be given reasons you could understand. And, and that's why I think, uh, the present societal trend to, um, uh, take away the humans and, uh, leave us, um, in the hands of decisions that, uh, we can't contest, uh, is a very dangerous one. I think we've got to d- be, be very careful of the extent to which AI, which can handle lots of information, actually makes the decisions without oversight. And I think, uh, um, we, we can use them as a supplement. But to take the case of, um, uh, uh, radiology and cancer, um, I mean, it's true that the ra- radiologist hasn't seen as many, uh, uh, X-rays of cancer lungs as the machine, so the machine can certainly help. But you want the human to make the final decision. And I think that's true in most of, of these instances. But if we turn a bit to the short term concerns with, uh, robotics, I think the, the big worry, of course, is the, uh, effect it has on, um, people's self-respect and their labor market. And I think, um, uh, my, my solution would be that we should, um, arrange to tax more heavily the big international c- conglomerates which, uh, use the robots, um, and, um, use that tax to, uh, uh, fund decently paid dignified posts of the kind where being a human being is important. Above all, carers for old people, teacher's assistants for young, gardeners in public parks, and things like that. And if the people who are now working in mind-numbing jobs in Amazon warehouses, uh, or in telephone call centers are automated, but those same people are given jobs where being a human i- is an asset. Um, then that's a plus plus situation. And so th- that's w- the way I think that we should, uh, benefit from these, these technologies, um, of take over the mind-numbing jobs, um, and, uh, u- use machines to make them more efficient. But, um, uh, enable, um, the people so displaced to do jobs where we do want a human being. I mean, most people, when they're, when they're old, um, or rich people if they have the choice, they want human carers and all that, don't they? They may want robots to help with some things, empty bedpans and things like that. But, but for, but they, they want real people. And, uh, uh, and, and certainly in this country, and I think even worse in America, um, the, the care of old people is completely inadequate and it needs just more human beings to, uh, help them cope with everyday life and look after them w- when they're sick. And, um, uh, and so, um, that seems to be the way in which the money raised in tax from these big companies should be deployed.

   30. LFLex Fridman1:16:21

       So that's in the short term, but if you actually just look, the fact is, where we are today to long-term future in 100 years-
9. 1:22:57 – 1:26:59

   Newton and Einstein

   1. LFLex Fridman1:22:57

      in your book on The Future Prospects for Humanity, you imagine a time machine that allows you to send a tweet-length message to scientists in the past, like to Newton.

   2. MRMartin Rees1:23:07

      (laughs) Yes.

   3. LFLex Fridman1:23:07

      Uh, what tweet would you send? That's an interesting thought experiment. What message would you send to Newton about what we know today?

   4. MRMartin Rees1:23:16

      Well, I think he'd love to know that there were planets around other stars. Um, he'd, he'd like to know that, uh-

   5. LFLex Fridman1:23:22

      That would really blow his mind, right?

   6. MRMartin Rees1:23:23

      ... yeah. He'd like to know that everything was made of atoms. Uh, he'd like to know that if he looked a bit more carefully, uh, through his prisms, um, uh, and, uh, looked at light not just from the sun but from, th- from some flames, he might get the idea that, uh, different substances emitted light of different, different colors, and he might have, uh, been twigged to discover some things that had to wait 200 or 300 years. Go- could've given him those clues, I think.

   7. LFLex Fridman1:23:54

      (sighs) It's kinda, it's fascinating to think, to look back at how little he understood, people at that time understood about our world.

   8. MRMartin Rees1:24:03

      Mm-hmm. Mm-hmm. Yes. Well, and, uh-

   9. LFLex Fridman1:24:05

      And how much we've-

   10. MRMartin Rees1:24:06

       ... and certainly about the cosmos, because of course-

   11. LFLex Fridman1:24:08

       About the cosmos, yes.

   12. MRMartin Rees1:24:09

       ... um, well, if we think about astronomy, um, then until about 1850, um, uh, astronomy was a matter of, um, um, uh, the positions of how the stars and the planets moved around, et cetera. Of course, that goes back a long way, but New- Newton understood why the planets moved around in ellipses. But, uh, he didn't understand, um, why the solar system was all in a plane, what we call the ecliptic. And, uh, he didn't understand it. In fact, no one did till the mid-19th century what the stars are made of. I mean, they were thought to be made of some fifth essence, not earth, air, fire, and water like everything else, you know? Um, and it was only after 1850 when, um, people did use, uh, prisms more precisely to get, to get spectra, that they realized that the, the sun was made of the same stuff as the earth, and indeed that the stars were. And, uh, it wasn't until, um, 1930 that people knew about nuclear energy and knew what kept the sun shining for, for so long. So, uh, it was quite late that some of these key ideas came in, you know, which would completely transform Newton's views and of course the, uh, entire scale of the solars, of the ga- galaxy, and, and the rest of the universe.

   13. LFLex Fridman1:25:26

       Just imagine-

   14. MRMartin Rees1:25:26

       So something that came later.

   15. LFLex Fridman1:25:27

       ... what he would have thought about the Big Bang, or even just general relativity.

   16. MRMartin Rees1:25:31

       Absolutely.

   17. LFLex Fridman1:25:31

       Just gravity.

   18. MRMartin Rees1:25:32

       Yeah, yeah. Yeah.

   19. LFLex Fridman1:25:32

       Just, just s- him and Einstein talking for, for a couple weeks.

   20. MRMartin Rees1:25:36

       Yeah, yeah. Mm-hmm. Yeah.

   21. LFLex Fridman1:25:38

       (sighs) ... (sighs) would he be able to make sense of spacetime and the curvature of spacetime and...

   22. MRMartin Rees1:25:44

       Well, I think g- given a quick course, I mean, he was sort of, uh...

   23. LFLex Fridman1:25:48

       (laughs)

   24. MRMartin Rees1:25:48

       If one looks back, he, he was really a unique intellect in a way, you know? And, uh, uh, he said that he thought better than everything, everyone else by thinking on things continually and thinking very deep thoughts. And, um, so he, he was a utterly remarkable intellect, obviously. But of course, scientists aren't all like that. I think it's very... One thing that interests me having spent a life among scientists is what a variety of, uh, mindsets and mental styles they have.

   25. LFLex Fridman1:26:16

       Yes.

   26. MRMartin Rees1:26:17

       Um, and, um, um, well, just to contrast Newton and Darwin, um, D- D- Darwin, uh, uh, said, uh, uh, and he's probably correct, does he... Th- this he thought he just had a, um, as, as much sort of a common sense and reasoning power as the average lawyer.

   27. LFLex Fridman1:26:36

       (laughs)

   28. MRMartin Rees1:26:38

       You know? (laughs) And, and that's probably true because his, his ability was to sort of, uh, collect data and think through things deeply. Um, that's a quite different kind of thinking from what was involved in a, in Newton or someone doing abstract mathematics.

   29. LFLex Fridman1:26:53

       (inhales deeply) I think in the 20th century, the coolest... Well, there's the theory, but

10. 1:26:59 – 1:40:40

    Black holes

    1. LFLex Fridman1:26:59

       from a astronomy perspective, black holes is one of the most fascinating entities to have been through theory and through experiment to have emerged-

    2. MRMartin Rees1:27:12

       Mm. No, obviously I agree. It's an amazing story that, uh, um, uh... Well, of course, what's interesting is Einstein's reaction because of course although, as you know, we now accept this is one of the most remarkable predictions of Einstein's theory. Uh, he never took it seriously or even believed it.

    3. LFLex Fridman1:27:29

       Yeah.

    4. MRMartin Rees1:27:29

       Um, although it was a consequence of, uh, a solution of his equations which someone discovered just a year after his theory, Schwarzschild. Um, but he, he never took it seriously, and others did. Um, but then of course, um, uh, well, this is something that I've been involved in actually finding evidence for black holes, and that's come in the last 50 years. And, um, uh, so now there's pretty compelling evidence that they exist, um, as the remnants of stars or big ones in the centers of galaxies. And we under- we understand, uh, h- what's the... What's going on. We have ideas vaguely on how, how they form. Uh, and of course, uh, uh, gravitational waves have been detected, and that's an amazing piece of technology.

Episode duration: 2:13:16