Brian Greene: Quantum Gravity, The Big Bang, Aliens, Death, and Meaning | Lex Fridman Podcast #232

1. 0:00 – 0:27

   Introduction

   1. LFLex Fridman0:00

      The following is a conversation with Brian Greene, theoretical physicist at Columbia and author of many amazing books on physics, including his latest, Until the End of Time: Mind, Matter, and Our Search For Meaning In An Evolving Universe. This is the Lex Fridman Podcast. To support it, please check out our sponsors in the description, and now, here's my conversation with Brian Greene.

2. 0:27 – 8:35

   Entropy

   1. LFLex Fridman0:27

      In your most recent book, Until The End of Time, you quote Bertrand Russell from a debate he had about God in 1948. He says, quote, (laughs) "So far as scientific evidence goes, the universe has crawled by slow stages to a somewhat pitiful result on this Earth and is going to crawl by still more pitiful stages to a condition of universal death. If this is to be taken as evidence of purpose, I can only say that the purpose is one that does not appeal to me. I see no reason, therefore, to believe in any sort of God." That's quite, uh, a depressing statement. As you say, this is a bleak outlook on our universe and the emergence of human consciousness. So, let me ask, what is a more hopeful perspective to take on this story?

   2. BGBrian Greene1:18

      Well, I think the more hopeful perspective is to more fully understand, um, what was driving Bertrand Russell to this perspective, and then to see it within a broader context, and really that's, in some sense, what- what my book Until the End of Time is all about. But, in brief, I would say that there's a lot of truth to what Bertrand Russell was saying there. When you look at the second law of thermodynamics, which is the underlying scientific idea that's driving this notion that everything's gonna wither, decay, fall apart, yeah, that's true. Second law of thermodynamics establishes that disorder, entropy, in aggregate is always on the rise, and that is indeed interpretable as disintegration and destruction over sufficiently long time scales. But my view is, when you recognize how special that makes us, that we are these exquisitely ordered configurations of particles that only will last for a blink of an eye in cosmological time-like terms, the fact that we're here and we can do what we do, to me, that's just really something that inspires gratitude, and wonder, and- and a sense of- of deep purpose by virtue of being these unique collections of entities that happen to rise up, look around, and try to figure out where we are and what the heck we should do with our time. So, it's not that I would disagree with Bertrand Russell in terms of the basic physics and the basic unfolding, but I think it's really a matter of the slant that you take on what it means for us.

   3. LFLex Fridman3:04

      (sighs) So, maybe we'll skip around a bit, but let me ask the biggest possible question then. You said purpose. So, what's the meaning of it all then? Is, uh, is there a meaning to life that we can take from this, from this brief emergence of complexity that arises from simple things and then goes into a- a heat death that is, once again, returns to simple things as the march of the second law of ther- thermodynamics goes on?

   4. BGBrian Greene3:33

      I think there is, but I don't think it's a universal answer. And so I think throughout the ages, there has been a kind of quest for some final way of articulating meaning and purpose, whether it's God, whether it's love, whether it's companionship. I mean, any- many people put forward different ways of taking this question on, and there is no one right answer when you recognize deeply that the universe doesn't care. There is nothing out there that is the final answer. It's not as though we need a more powerful telescope, and somehow if we can look deeply into the universe, all will become clear. In fact, the deeper we've looked, both literally and metaphorically, into the universe and into the structure of reality, the more it's become clear that we are just a momentary byproduct of laws of physics that don't have any emotional content. They don't have any intrinsic sense of meaning or purpose. And when you recognize that, you realize that searching for the universal for this kind of a question is a fool's errand. Every individual has the capacity to make their own meaning, to set their own purpose. And that's not some platitude. That is what we are, because there is no fundamental answer. It's what you make of it. And however much that may sound like a Hallmark card, this really is the deep lesson of- of physics and science more generally over the past few hundred years.

   5. LFLex Fridman5:11

      Well, there's some level where you can objectively say that whatever we got going on here is kind of peculiar. It's kind of, um, special in- in- in, uh, in terms of complexity, and maybe you can even begin to measure it and, like, um, come up with metrics where whatever we got going on on Earth, these, like, uh, interesting hierarchical complexities that form more and more sophisticated biological system, that seems kind of unique when you look at the entirety of the universe, the, um, the observable part that we can see with our tools. I mean, so I have to ask, as you describe in your book once again, uh, Schrodinger wrote the book, What Is Life? based on a few lectures he gave in 1944. So, let me ask.... the fundamental question here, what is life? This particular thing we got going on here, this pocket of complexity that emerged from such simple things.

   6. BGBrian Greene6:10

      Yeah, it's a tough question. I asked that question even to, uh, Richard Dawkins once, and I already had my preconceived notion, which he pretty much confirmed, which is, if one could give an answer to that question that allowed you to sort of draw a line in the sand between the not living and the living, then perhaps we would have the insight that we yearn for in trying to say what is so special about life? But the fact of the matter is, it's a continuum. There's a continuum from the things that we would typically call non-living, inanimate, to the things that we obviously call animate and full of the currents of life. Somewhere in there, it is a question of the complexity of the structure, the ability of the structure to take in raw material from the environment and process it through a metabolism that allows the structure to extract energy and to release entropy to the wider environment. Somewhere in those collections of biological processes is the necessity or the necessary ingredients and processes for life, but drawing that line in the sand is not something that we're able to do. But I would agree with you, it's deeply peculiar. It may, in fact, be unique, but it may not. It could be that the universe is such that under fairly typical conditions, a star that's a well-ordered source of low entropy energy, that's what the sun is, together with a planet being bathed by that low entropy energy, together with a surface that has enough of the raw constituents that we recognize are fairly commonplace result of supernova explosions, where a star spews forth the result of the nuclear furnace that is the core of a star, it could be that all you need are those fairly commonplace conditions, and maybe life naturally forms. Look, the James Webb Space Telescope, right, is going up, hopefully in December.

   7. LFLex Fridman8:21

      Mm-hmm.

   8. BGBrian Greene8:21

      And one of the, one of the goals of that mission is to look at atmospheres around distant planets and perhaps come to some sense of how special or not life, or at least life as we know it, is in the universe.

3. 8:35 – 24:54

   Consciousness

   1. BGBrian Greene8:35

   2. LFLex Fridman8:36

      Which part of this story of life, let's stick to earth for a second, do you think is the, uh, is the hardest? If you were like a, a betting man, like which part is the hardest to, uh, make happen? Is it the origin of life? Again, we haven't drawn the line of where, as you say, uh, the line between a rock and a rabbit. Um, that part, is it, uh, complex organisms like multicellular organisms? Is it, uh, crawling out of the ocean where the fish somehow figured out how to crawl around? Is it then the, uh, us homo sapiens as we like to think of ourselves, s- special and intelligent? Uh, or is it somewhere in between as you also talk about, again, very hard to know at which point does consciousness-

   3. BGBrian Greene9:26

      Yeah.

   4. LFLex Fridman9:27

      ... emerge? Like, if you, if you were to sort of took a s- a survey and made bets about other Earth-like planets in the universe, where do you think they get stuck the most?

   5. BGBrian Greene9:38

      Well, I would certainly say if we're gonna go all the way to conscious beings like ourselves, I would put it at the onset of consciousness, which again, I think is a continuum. I don't think it is something that you can draw the line in the sand, but there are obvious circumstances, there are obvious creatures such as ourselves where we do recognize a certain kind of self-reflective conscious awareness. And if we think about what it would require for a system of living beings who acquire consciousness, I think that's probably the hardest part. Because look, take earth and recognize that weren't for, you know, some singular event 65 million years ago where this large rock slams into planet Earth and wipes out the dinosaurs, maybe the dinosaurs would still rule the planet, and they may well have not developed the kind of conscious awareness that we have. So, for billions of years on this planet, there was life that didn't have the kind of conscious awareness that we have, and it was an accidental event in astrophysical history that allowed a mammalian species like us to ultimately be the end product. And so, yeah, I could imagine there's a lot of life out there, but perhaps none of it's wondering what's the meaning of life (laughs) or trying to make sense of it. Just going about its business of survival, which of course is the dominant activity that life on this planet has practiced. We are a rare exception to that.

   6. LFLex Fridman11:17

      And I really appreciate that you lean into some of these unanswerable questions (laughs) with me today. But, uh, so you think about consciousness not as like a phase shift, a binary zero-one. You think, um, of it as a continuum that humans somehow are maybe some of the most conscious beings on Earth. So, you're s- so...

   7. BGBrian Greene11:39

      I mean, people will dispute that for us.

   8. LFLex Fridman11:40

      Yes. I mean, well, yeah.

   9. BGBrian Greene11:42

      And, and it's a very hard argument to make.

   10. LFLex Fridman11:43

       People will dispute that. Rocks probably will stay quiet on the matter.

   11. BGBrian Greene11:47

       Maybe not-

   12. LFLex Fridman11:48

       (laughs)

   13. BGBrian Greene11:48

       ... right? (laughs) For the moment, they're waiting for their opportunity. But, but, uh, but I, I, I, I agree that, um, look, even when you and I look at each other, I am not fully convinced...

   14. LFLex Fridman12:01

       Mm-hmm.

   15. BGBrian Greene12:01

       ... that you're a conscious being, right? I mean, I think that you are.

   16. LFLex Fridman12:04

       He's onto me.

   17. BGBrian Greene12:05

       I mean, your behavior is such that-

   18. LFLex Fridman12:07

       Yes.

   19. BGBrian Greene12:07

       ... that's the best explanation for what's going on. But of course, we're all in the position of only having direct awareness of our own conscious...... being, and therefore when it comes to other creatures in the world, we're in a similar state of ignorance regarding what's actually happening inside of their head, if they have a head, and so it's hard to know how singular we are. But I would say, based on the best available data and the best explanations we can make, yeah, there is something special about us. I don't think that there are fish walking around and, you know, coming up with, you know, existentialism. I don't know that there are, you know, dogs walking around who've developed an understanding of the general theory of relativity. I mean, maybe we're wrong, but that seems the best explanation.

   20. LFLex Fridman12:54

       What do you think is more special, intelligence or consciousness?

   21. BGBrian Greene12:58

       I think consciousness, and I think that there's, um, a deep connection between these ideas. They are distinct, but they're deeply connected. But, look, I mean, to me and to, of course, many philosophers who actually coined a name for this, the hard problem of consciousness, you know, David Chalmers and others, as a physicist I look out at the world and I see its particles governed by physical law. We can name them. You know, we got electrons, we've got quarks that come in various flavors and so forth. We have a list of ingredients that science has revealed, and we have a list of laws that seemingly govern those ingredients, and, and nowhere in there is there even a hint that when you put those particles together in the right way, an inner world should turn on. And it's not only that there's no hint, it's insane. I mean, it's ridiculous. How could it be that a thoughtless, passionless, emotionless particle when grouped together with compatriots somehow can yield something so deeply foreign to the nature of the ingredients themselves? So, so answering that question I think is among the deepest and most difficult questions that we face.

   22. LFLex Fridman14:17

       Do you think it is in fact a really hard problem or is it possible... I think you mention in your book that it's just like a, almost like a side effect. It's an emergent thing that's like, "Oh, it's nice. It's like a nice little feature." (laughs)

   23. BGBrian Greene14:35

       Yeah. Well, I mean, when people use the phrase "hard problem," I mean, they mean it in a somewhat technical sense that it's trying to explain something that seems fundamentally unavailable to third-party objective-

   24. LFLex Fridman14:50

       Mm-hmm.

   25. BGBrian Greene14:51

       ... analysis, right? I'm the only one that can get inside my head and I can tell you a lot about what's happening inside my head right now, as reflected in what I'm saying-

   26. LFLex Fridman15:00

       (laughs)

   27. BGBrian Greene15:00

       ... and you can try to deduce things about what's going on inside my head, but you don't have access to it in the way that I do. And so it seems like a fundamentally different kind of problem from the ones that we have successfully dealt with over the course of centuries in science, where we look at the motion of the moon. Everybody can look, everybody can measure it. We look at, you know, the properties of hydrogen when you shine lasers on it, everybody can look at the data and understand it. And so it seems like a fundamentally different problem, and in that sense it seems like it is hard-

   28. LFLex Fridman15:32

       Mm-hmm.

   29. BGBrian Greene15:32

       ... relative to the others, but I do think ultimately that the explanation will be as you recount. I think that 100 years from now, or maybe it's 1,000, it's hard to predict the time scale for developments, but I think we'll get to a place where we'll look back and kind of smile at those folks in the 20th century and before, 21st century and before, who thought consciousness was so incredibly mysterious, when the reality of it is, eh, it's just a thing that happens when particles come together. And, and however mysterious that feels right now, I think, for instance, when we start to build conscious systems, you know, things that, you know, you're more familiar with than I am, when we start to build these artificial systems and those systems report to us, "I'm feeling sad. You know, I'm feeling anxious. Yeah, there's a world going on inside here," I think the mystery of consciousness will just begin to evaporate.

   30. LFLex Fridman16:30

       Well, that's, first of all, beautifully put, and I agree with you completely, just the way you said it, "It'll begin to evaporate." I have b- built quite a few robots and have had them do emotion- emotional type things, and it's immediate that exactly what you're saying, this kind of mystery of consciousness starts to evaporate.
4. 24:54 – 28:14

   Quantum gravity

   1. BGBrian Greene24:54

   2. LFLex Fridman24:54

      Do you have a hope that we solve that theory of everything puzzle in, in the next few decades? So there's been a, a bunch of attempts from string theory to all, all kinds of attempts at trying to solve quantum gravity, or basically come up with a theory for quantum gravity. There's a lot of, uh, complexities to this. One, for experimental validation, you have to observe effects that are very difficult to, uh, measure. So you have to build ... Like, that's like an engineering challenge. And then there's the theory challenge, which is like it seems very difficult to connect the, the laws of gravity to quantum mechanics. Do you have a hope or are we s- hopelessly stuck?

   3. BGBrian Greene25:35

      Well, I have to, have to have a hope. I mean, it's, in some sense, why I devote at least part of my professional life toward trying to make progress on ... I'm glad you used the phrase quantum gravity. I'm not a great fan of the theory of everything phase, because it does make other scientists feel like if they're not working on this-

   4. LFLex Fridman25:54

      (laughs)

   5. BGBrian Greene25:54

      ... (laughs) what are they working on? I mean, it's like, you know, there's not much left when you're talking about a theory of everything. But-

   6. LFLex Fridman25:58

      Biology is just small details

   7. NANarrator26:00

      Yeah, right, exactly.

   8. LFLex Fridman26:00

      ... we'll figure out. (laughs)

   9. BGBrian Greene26:01

      Yeah. So, so it is really trying to put gravity and quantum mechanics together. And, uh, since I was a, a college kid, I was, uh, deeply fascinated with gravity. And as I learned quantum mechanics, the, the notion of physicists being stumped and trying to blend them together, how could one not get fired up about maybe contributing something to that journey? And so we've been on this, you know, I've been on this for 30 years, since I was a student. We, we have made progress. We do have ideas. You mentioned string theory is one possible scenario. It's not stuck. String theory is a vibrant field of research that is making incredible progress, but we've not made progress on this issue of experimental verification validation, which as you know, it is a vital part of the story. So I would have hoped that by now, we would have made contact with observation. If you would have interviewed me back in the '80s, when I was, you know, a wild, bright-eyed kid trying to make head ... w- working 18 hours a day and this sort of stuff, I would have said, "Yeah, by, by 2021, yeah, we're gonna know whether it's right or wrong, we'll have made contact." I, I would have said, "Look, there may be certain mathematical puzzles that we've yet to work out, but we'll know enough to make contact with experiment." That has not happened. On the other hand, if you would have interviewed me back then and asked me, "Will we be able to talk about detailed qualities of black holes and understand them at the, uh, the level of detail that we actually ..." I, I would have said, "No, I, I don't think that we're gonna be able to do that." "Will we have a, a, an exact formulation of string theory in certain circumstances? No, I don't think we're gonna have that." And yet we do.

   10. LFLex Fridman27:46

       Hm.

   11. BGBrian Greene27:46

       So, it's just to say you don't know where the progress is going to happen, but yes, I do hold out hope that maybe before I move on to wherever, I don't think there is an after, but I, I would love before I leave this Earth to, to know the answer. But, you know, science and the universe, it's not about pleasing (laughs) any individual. It is what it is. And so, um, we just press onward and we'll see

5. 28:14 – 41:41

   String theory

   1. BGBrian Greene28:14

      where it goes.

   2. LFLex Fridman28:15

      So in terms of string theory, if I just look from an outsider's perspective currently at the theoretical physics community, string theory as a theory was, as a theory has been very popular for, for a few decades. But it has recently fallen out of favor, or at least there's been like, you know, it became more popular to kind of ask the question, is string theory really the answer? Where do you fall on this? Like, how do you make sense of this puzzle? Why do you think it has fallen out of favor?

   3. BGBrian Greene28:45

      Yeah, so I don't ... I would actually challenge the statement that it's fallen out of favor. I would say that any field of research, when it's new and it's the, the-

   4. LFLex Fridman28:56

      Mm-hmm.

   5. BGBrian Greene28:56

      ... bright, shiny bicycle that no one has yet seen on that block, yeah, it's gonna attract attention, and, uh, the news outlets are gonna cover it and students are gonna flock to it, sure. But as a, as a field matures, it does shed those qualities because it's no longer as novel as it was when it was first introduced 30 or 40 years ago. But you need to judge it by a different standard. You need to judge it by is it making progress on foundational issues deepening our understanding of the subject? And by that measure, string theory is, is, is scoring very high. Now, at the same time, you also need to judge whether it makes contact with experiment, as we discussed before too. And in that measure, we're still challenged. So, I would say that many string theorists, myself included, are, are very sober about the theory. It, it has the tremendous progress that it had 30, 40 years ago, that hasn't gone away, but we've become better equipped at assessing the long journey ahead.

   6. LFLex Fridman30:07

      Mm-hmm.

   7. BGBrian Greene30:07

      And that was something that we weren't particularly good at back, say, in the '80s. Look, when I was just starting out in the field, there was a sense of physics is about to end. (laughs) String theory is about to be the be all and end all final unified theory, and that will bring this chapter to a close. Now I have to say, I think it was more the younger physicists who were saying that. Some of the more seasoned, even if they were pro-string theory at the time-... I don't know if they were rolling their eyes, but they knew.

   8. LFLex Fridman30:39

      Yeah.

   9. BGBrian Greene30:39

      That it was going to be a long, long journey. I think people like, you know, John Schwarz, one of the founders of string theory, Michael Green, no relation to me, founders of the theory, uh, Edward Witten, you know, one of the main people driving the theory back then and today, I think they knew that we were in for a long haul. And, and that's the nature of science. Quick hits that resolve everything, few and far between. And so if you were in for the quick solution to the big questions of the world, then you would have been disappointed, and I think there were people who were disappointed and moved on and worked on other subjects. If you were in, in the way that Einstein was in, for a lifetime of investigation to try to see where ... w- what the answers to the deep questions would be, then I think string theory has been a rich source of, of material that has kept so many people deeply engaged and moving the frontier forward.

   10. LFLex Fridman31:41

       There's a few qualities about string theory which are weird. I mean, a lot of physics is just weird and beautiful. So, let me ask the question, what to you is most beautiful about string theory?

   11. BGBrian Greene31:53

       Well, what, uh, what attracted me to the theory at the outset, beyond its putting gravity and quantum mechanics together which I think is, um, its true claim to fame, at least on paper it's able to do that, what attracted me to the theory was the fact that it requires extra dimensions of space.

   12. LFLex Fridman32:10

       Mm-hmm.

   13. BGBrian Greene32:11

       And this was an idea that intrigued me in a, in a very deep way, even before I really understood what it meant. I somehow had, I mean, talk about sort of the emotional part of consciousness and the cognitive part, in some, perhaps you'd call it strange, in some strange emotional way, I was enamored with Einstein's general relativity, the idea of curved space and time. Before I really knew what it meant, it just spoke to me. I don't know how else to say it.

   14. LFLex Fridman32:42

       Mm-hmm. Mm-hmm.

   15. BGBrian Greene32:43

       And then, when I subsequently learned that people had thought about more dimensions of space than we can see and how those extra dimensions would be vital to a deep understanding of the things that we do see in this world, four or five, six dimensions might explain why there are certain forces and particles and how they behave, to me this was like amazing, utterly amazing. And then when I learned that string theory embraced all these ideas, embraced the general theory of relativity, embraced quantum mechanics, embraced the possibility of extra dimensions, then I was, then I was hooked.

   16. LFLex Fridman33:19

       (laughs)

   17. BGBrian Greene33:19

       And so when I was a graduate student, we would just spend hours, uh, we, I mean a couple of other graduate students and myself who had, uh, had, uh, sort of worked really well together, this was at Oxford in England, we would, we would work these enormous numbers of hours a day trying to understand the shapes of these extra dimensions, the geometry of them, what those geometrical shapes for the extra dimensions would imply for things that we see in the world around us, and it was, uh, it was a heady, heady time. And, and that kind of excitement has sort of filtered through over the decades, but I'd say that's really the, the part of the theory that I think really hooked me most strongly.

   18. LFLex Fridman34:00

       How are we supposed to think about those extra dimensions? Are we supposed to imagine actual physical reality or are, is this more in the space of mathematics that allows you to sort of come up with tricks to describe the four-dimensional reality that we more, more directly perceive?

   19. BGBrian Greene34:17

       No one really knows the answer, of course, but if I take the most straightforward approach to string theory, you really are imagining that these dimensions are there, they're real. I mean, just as you would say that the three space dimensions around us, you know, left/right, back/forth, up/down, yeah, we, they're real, they're here. We are immersed within those dimensions. These other dimensions are as real as these, with the one difference being their shape and their size differs from the shape and size of the dimensions that we have direct access to through-

   20. LFLex Fridman34:52

       Mm-hmm.

   21. BGBrian Greene34:52

       ... through human experience. And one approach imagines that these extra dimensions are tightly coiled up-

   22. LFLex Fridman34:59

       Mm-hmm.

   23. BGBrian Greene35:00

       ... curled up, crushed together, if you will, into a beautiful geometrical form that's all around us, but just too small for us to detect with our eyes, too small for us to detect even with the most powerful equipment that we have.

   24. LFLex Fridman35:15

       Mm-hmm.

   25. BGBrian Greene35:16

       Nevertheless, according to the mathematics, the size and the shape of those extra dimensions leaves an imprint in the world that we do have access to. So one of the ways that we have hoped yet to achieve to make contact with experimental physics is to see a signature of those extra dimensions in places like the Large Hadron Collider in Geneva, Switzerland.

   26. LFLex Fridman35:37

       Mm-hmm.

   27. BGBrian Greene35:38

       And it hasn't happened yet. Doesn't mean it won't happen, but that would be a stunning moment in the history of the species if data that we acquired in these dimensions gives us kind of incontrovertible evidence that these dimensions are not the only dimensions. I mean how mind-blowing would, would that be?

   28. LFLex Fridman35:59

       So would the Large Hadron Collider, it would be something in the movement of the particles or, um, also the gravitation waves potentially be a, a place where you can detect signs of multiple dimensions like with-

   29. BGBrian Greene36:10

       Yeah.

   30. LFLex Fridman36:10

       ... something with LIGO but much more accurate?
6. 41:41 – 54:13

   Time

   1. LFLex Fridman41:41

      We, we've, uh, mentioned the second law of thermodynamics. I gotta ask you about time.

   2. BGBrian Greene41:46

      Yeah.

   3. LFLex Fridman41:47

      And do you, do you think of time as emergent or fundamental to our universe?

   4. BGBrian Greene41:53

      I like to think of it as emergent. I don't have a solid reason for that perspective. I have a lot of hints of reasons that some of which come out of string theory and quantum gravity that perhaps would be worth talking about. But what I would say is time is the most familiar quality of experience because there's nothing that takes place that doesn't take place within an interval of time. And yet at the same time, it is perhaps the most mysterious quality of the world. So, it's a wonderful confluence of the familiar and the deeply mysterious all in one little package. If you were to ask me, what is time? I don't, I don't really know. I don't think anybody does. I, I can say what time-... gives us, it allows us the language for talking about change. It allows us to envision the events of the universe being spread out in this temporal timeline, and in that way allows us to see the patterns that unfold within time. I mean, time-

   5. LFLex Fridman43:02

      Mm-hmm.

   6. BGBrian Greene43:02

      ... allows us the structure and the organization to think about things in that kind of a progression. But what actually is it? I, I, I don't really know, and that's so strange because we can measure it, right? (laughs) I mean, there are laboratories in the world that measure this thing called time to spectacular precision. But, you know, if you go up to the folks and say, like, "What is it that you're actually measuring?" I don't know that they can really articulate the kind of answer that you would expect from those who are engineering a device that can measure something called time to that level of precision. So, it's a very curious combination.

   7. LFLex Fridman43:47

      What do you make of the one-way feeling of causality? Like, is causality a, a, a thing or is that too just a human, uh, story that we put on top of this emerging phenomena of time?

   8. BGBrian Greene44:00

      I don't know. Um, I can give you my, my guess and my intuition about it. I, I do think that at the macroscopic level, if we're talking about sort of the human experience of time, I do think at the macroscopic level, there is a fundamental notion of causality-

   9. LFLex Fridman44:16

      Mm-hmm.

   10. BGBrian Greene44:17

       ... that does emerge from a starting point that may not have causality built in. So, I certainly would allow that at the deepest description of reality when we finally have that on the table, we may not see causality directly at that fundamental level.

   11. LFLex Fridman44:33

       Mm-hmm.

   12. BGBrian Greene44:33

       But I do believe that we will understand how to go from that fundamental level to a world where, at the macroscopic level, there is this notion of A causes B, a notion that Einstein deeply embraced in his special theory of relativity, where he showed that time has qualities that we wouldn't expect based on experience. You and I, if we move relative to each other, our clocks tick off time at different rate, and our clocks is just a means of measuring this thing called time. So, this is really time that we're talking about. Time for you and time for me are different if we're in relative motion. He then shows in the general theory of relativity that if we're experiencing different gravity, different gravitational-

   13. LFLex Fridman45:15

       Mm-hmm.

   14. BGBrian Greene45:16

       ... fields, or actually more precisely, different gravitational potentials, time will elapse for us at different rates. These are things that are astoundingly strange that give rise to a scientific notion of time travel, okay? So, this is, this is how far Einstein took us in wiping away the old understanding of time and injecting a new understanding of its quality. So, so, there's so much about time that's counterintuitive, but I do not think that we're ever going to wipe away causality at the mi- macroscopic level.

   15. LFLex Fridman45:50

       At the, at the macroscopic l- I mean, there's so many interesting things that the macroscopic level that may only exist (laughs) at the macroscopic level.

   16. BGBrian Greene45:56

       Yeah.

   17. LFLex Fridman45:56

       Like, we d- we already talked about consciousness. That, that very well could be one of the things. You mentioned time travel. So, um, I mean, according to Einstein, and in, and in general, what types of travel do you think our physical universe allows?

   18. BGBrian Greene46:14

       Well, it certainly allows time travel to the future, and I'm not talking about the silly thing that you and I are now going (laughs) into the future second by second by second. I'm talking about really the diversion that you see in Hollywood, at least in terms of its net effect, whereby an individual can follow an Einsteinian strategy and propel themselves into the future, in some sense, more quickly.

   19. LFLex Fridman46:41

       Mm-hmm.

   20. BGBrian Greene46:42

       So, if, if I wanted to see what's happening on planet Earth one million years from now, Einstein tells me how to get one million years from now. Build a ship. I gotta turn to guys, you know, who know how to build stuff.

   21. LFLex Fridman46:56

       Mm-hmm.

   22. BGBrian Greene46:56

       (laughs) I can't do it, like you. Build a ship that can go out into the universe near the speed of light.

   23. LFLex Fridman47:01

       Mm-hmm.

   24. BGBrian Greene47:01

       Turn around and come back. Let's say it's a six-month journey out and a six-month journey back. And Einstein tells me how fast I need to travel, how close to the speed of light I need to go, so that when I step out of my ship, it will now be one million years into the future on planet Earth. And this is not a controversial (laughs) statement, right? This is not something where there's differences of opinion in the scientific community. Any scientist who knows anything about what Einstein taught us agrees with what I just said. It's, it's commonplace. It's bread-and-butter physics. And so, that kind of travel to the future is absolutely allowed by the laws of physics. There are engineering challenges. There are, there are technological challenges.

   25. LFLex Fridman47:47

       Like, closing the speed of light part, yeah.

   26. BGBrian Greene47:49

       Yeah, and there are, there are even biological challenges, right? There are G-forces that you're gonna experience. You know, so there's all sorts of stuff embedded in this. But those, I will call the details, and those details, notwithstanding, the universe allows this kind of travel to the future.

   27. LFLex Fridman48:07

       And if I could pause real quick. You could also, at the macro level, with biology, extend the human lifespan to do a kind of travel forward in time. (laughs) If, if you expand how long we live-

   28. BGBrian Greene48:22

       Yeah.

   29. LFLex Fridman48:22

       ... that's a way to, from a perspective and of an observer, a conscious observer that is a human being, you're essentially traveling forward in time by allowing yourself to live long enough to see the thing.

   30. BGBrian Greene48:32

       Yes.
7. 54:13 – 58:36

   Free will

   1. BGBrian Greene54:13

   2. LFLex Fridman54:13

      (inhales) So if that's not the case and you have these simple particles that at the macro level emerges some interesting stuff like consciousness, another thing you write about in the Until the End of Time book is the, the, the thing that it seems to emerge at the macro level is the feeling like, uh, th- like there's a free will.

   3. BGBrian Greene54:34

      Mm.

   4. LFLex Fridman54:35

      Like we decide to do stuff. And you have a really interesting take here which is know there's not a free will. Uh, I'm just gonna speak for you and then you-

   5. BGBrian Greene54:44

      Sure.

   6. LFLex Fridman54:45

      ... can correct me. Know there's not a free will, but there is an experience of freedom.

   7. BGBrian Greene54:51

      Yeah.

   8. LFLex Fridman54:52

      ... (laughs)

   9. BGBrian Greene54:53

      Yeah.

   10. LFLex Fridman54:53

       ... can, uh, which I, uh, I really love. So where does the experience... Where does freedom come from if we don't have any kind of physics-based free will?

   11. BGBrian Greene55:02

       Yeah. And, and so the idea follows naturally from all that we've been talking about. Let's make the assumption that all there is in the physical universe is stuff governed by laws. We may not have those laws, may, may not know what the fundamental stuff is yet, but everything we know in science points in the direction that it's physical stuff governed by universal laws. And that being the case, or that being the assumption, then you come to a particular collection of those ingredients called a human being, and that human being has particles that are fully governed by physical law. And when you then recognize that every thought that we have, every action that we undertake, is just the motion of particles. When I'm thinking thoughts right now, of course, at this level of description, it is the motion of particles cascading down various neurons inside of my head, and so on. And every single one of those motions, collectively and individually, is fully governed by these laws that we perhaps don't have yet, but we imagine one day we will. That leaves no opportunity for any kind of freedom to break free from the constraint of physical law, and that is the end of the story.

   12. LFLex Fridman56:21

       Mm-hmm.

   13. BGBrian Greene56:21

       So the traditional intuitive notion of free will, that we're the ultimate authors of our actions, that we're where the buck stops, that there is no antecedent that is the cause for our deciding to go left or right, choose vanilla or chocolate, live or die, that intuitive sensation does not have a basis in our understanding of the physical world.

   14. LFLex Fridman56:43

       (laughs)

   15. BGBrian Greene56:43

       So, that's the end of the free will of the traditional sort. But then your question is, what about this other kind of freedom I talk about? And the other kind of freedom, if you focus on it intently, I think is actually the true version of freedom that we feel, and that freedom is this. You look at inanimate objects in the world, rocks, bottles of water, whatever, they have a very limited behavioral repertoire. Why? Their internal organization is too coarse for them to do very much, right? You have to... You try to have a conversation with a glass of water. You send sound waves. It doesn't do much. It may vibrate a little bit, but the repertoire of responses are incredibly limited.

   16. LFLex Fridman57:29

       Mm-hmm.

   17. BGBrian Greene57:30

       The difference between us and a rock or a bottle of water is that our inner organization, by virtue of eons of evolution by natural selection, is so refined, so spectacularly ordered, that we have a huge repertoire of behaviors that are finely attuned to stimuli from the external world. You ask me a question, that's a stimulus, and all of a sudden, these particle processes go into action and this is the result, this answer that I'm giving you. So, the freedom that we have is not from the control of physical law.

   18. LFLex Fridman58:05

       Mm-hmm.

   19. BGBrian Greene58:05

       The freedom that we have is from the constrained behavior that has long since governed inanimate objects. We are liberated from the limited behavioral repertoire of rocks and bottles of water to have this broad spectrum of responses. Do we pick them? We do not. Do we freely choose them? We do not. But yet we have them, and we can marvel at those behaviors, and that's the freedom that we have.

   20. LFLex Fridman58:31

       The complexity and the breadth of that repertoire is, is where the freedom emerges.

   21. BGBrian Greene58:35

       Yes.

8. 58:36 – 1:05:48

   Emergence and complexity

   1. BGBrian Greene58:36

   2. LFLex Fridman58:36

      Is there something to be said about emergence? I don't know if you know or have looked that much about objects that I seem to, uh, love way more than anyone else, which is cellular automata. (laughs)

   3. BGBrian Greene58:48

      Yeah.

   4. LFLex Fridman58:49

      Like Game of Life type of stuff. There, uh, you know, from simple things emerges beautiful complexity.

   5. BGBrian Greene58:56

      Yes.

   6. LFLex Fridman58:56

      And so that's that repertoire. It's like, it seems if you have enough stuff, just beautiful complexity emerges that sure as heck, to our human eyes, looks like there's consciousness there, there's free will, there's little objects moving about and making decisions. I mean, all of that, you could say it's anthropomorphization, but it sure as heck feels like there are organisms making decisions. Um, what is, what is that, that emergence thing? Is that, is that within the realm of physics to understand? Is it, uh, is it within the realm of poetry? What... 'Cause, what is that?

   7. BGBrian Greene59:36

      Well-

   8. LFLex Fridman59:37

      Like, complex systems, emergences, what is that? Will that ever be understood by science?

   9. BGBrian Greene59:41

      So, here's, here's the way that I think about it. So, there are clearly qualities of the world that emerge on macroscopic scales.

   10. LFLex Fridman59:50

       Yeah.

   11. BGBrian Greene59:51

       Our sense of beauty, wonder, consciousness, all of these kinds of qualities. Do I feel that they ultimately are explainable from the laws of physics? I do. There is nothing that's not ulti- ultimately explainable with the laws of physics, from this physicalist perspective, which is what I take. So, you got the particles, you got the laws, and you have things that emerge from the choreographed motions of those particles. But is that the best language for talking about these emergent qualities? Usually not. If I was to take something even more mundane, like a baseball flying through the air, if I was to describe it in terms of the quarks and the electrons, I'd give you this mountain of data with, you know, 10^28 particles (laughs) and all of their coordinates in space as a function of time, I hand you this mountain of data, you'd be like, "I don't know what this is." And then if you really were clever and you're looking, "Oh, it's a baseball," just described in the, in the least economical way possible. It is much more useful...... and insightful to talk about the baseball flying through the air. Similarly, there are things at the macroscopic level, like human experience and human emotion, and human action, and the sensation of free will that we undeniably all have, even if it itself doesn't have a basis in our understanding of the physical world. It's useful to talk about things in this very human language.

   12. LFLex Fridman1:01:24

       Mm-hmm.

   13. BGBrian Greene1:01:24

       And so, yes, it's vital to talk about things in the poetic language of human experience, but do not lose sight of the fact, and some people do, they say, "Oh, it's just an emergent phenomenon." Don't lose sight of the fact that emergent phenomena are emerging from this deeper understanding that comes from the reductionist account of physical law, and there's a lot of insight to come from that, such as the freedom that you thought that you had, the freedom of will that you thought you had, it doesn't have a basis in that reductionist account, so it's not real.

   14. LFLex Fridman1:01:56

       So, speaking of the poetry of human experience, you mentioned the images of the black holes. How did that make you feel a few years ago when that first image came out?

   15. BGBrian Greene1:02:04

       Truly amazing. Uh, a sense of... Well, I guess the feeling was both amazing and, and there was a little sense of, um... Jealousy is not quite the right word, but a sense of longing. Yeah, I think that's a better word. Because here's a subject that started with Einstein back in 1915, writes down the equations of the general theory of relativity, and then there are scores of individuals over the decades, you know, starting with people like Karl Schwarzschild, who analyzed the equation, see the possibility of black holes. People developed these ideas. John Wheeler, all these greats of physics. It's still a hypothetical subject. It gets closer to reality through observations of the center of our galaxy, stars whipping around in a manner that could only really be explained by there being a black hole in the center of our galaxy, but it was still indirect.

   16. LFLex Fridman1:02:58

       Mm-hmm.

   17. BGBrian Greene1:02:58

       To actually have a direct image that you can look at, what a beautiful arc, narrative arc from the theoretical to the absolutely established. And that's what we hope will happen with other areas. For instance, string theory, right? I mean, wholly mathematical subject at the outset, and still pretty much a wholly mathematical subject today. Yeah, do we long for that image where we can look at it and say, "String, it's real maybe."

   18. LFLex Fridman1:03:29

       (laughs)

   19. BGBrian Greene1:03:29

       You know, I mean, oh, how thrilling.

   20. LFLex Fridman1:03:32

       Mm-hmm.

   21. BGBrian Greene1:03:32

       How thrilling to be part of that journey, to be part of that, that step that moves things from the abstract to the concrete.

   22. LFLex Fridman1:03:40

       Yeah. Uh, so like the image of the DN- the early images of DNA, for example.

   23. BGBrian Greene1:03:45

       Sure.

   24. LFLex Fridman1:03:45

       Uh, but there is something espec- so the problem with strings is they're tiny, so it's harder to take a picture. Uh, in the- in- in the following sense, when you think of a black hole, I mean, you have a swirl of, I guess, what is that, I don't even know, it's dust go- or whatever, light-

   25. BGBrian Greene1:04:02

       Accreting onto the-

   26. LFLex Fridman1:04:03

       Yeah.

   27. BGBrian Greene1:04:03

       ... uh, event horizon.

   28. LFLex Fridman1:04:04

       And then there's darkness-

   29. BGBrian Greene1:04:06

       Yeah.

   30. LFLex Fridman1:04:06

       ... in the center, and then you could- you just imag- so that picture in particular, I guess of a- is of a gigantic (laughs) black hole. So you just, I mean, it's terrifying.
9. 1:05:48 – 1:18:47

   The Big Bang

   1. BGBrian Greene1:05:48

   2. LFLex Fridman1:05:48

      Well, I have to ask about the most stupendously powerful thing to have ever happened in our universe, which is the Big Bang.

   3. BGBrian Greene1:05:55

      Yeah.

   4. LFLex Fridman1:05:56

      What's up with the Big Bang? (laughs)

   5. BGBrian Greene1:05:58

      (laughs)

   6. LFLex Fridman1:05:59

      So we can- I mean, with gravitation waves, the hope is when you have more and more accurate measurements of the gravitation waves, you can crawl back further and further back in time towards the Big Bang. Do- do you ever hope that we'll be able to understand the- the early spark that created our universe?

   7. BGBrian Greene1:06:18

      Yeah. You know, that and the- the deep interior of a black hole, I think are the- the biggest mysteries that we hope the melding of quantum mechanics and gravity will reveal, will illuminate. And, you know, what question could be more captivating than why is there something rather than nothing, right? Why is there a universe at all? And will the theories that we're developing take us to an answer to that? I don't know. Even if we truly knew what the Big Bang is, and that's a big question in its own right, one would still be left with the question, well, okay, so you've explained the process by which a tiny nugget of a universe, a tiny nugget of space-time-... can undergo some kind of growth to yield the world around us, but presumably, in that explanation, you're going to involve mathematics and some ingredients like quantum fields or, or matter, or energy, or something. Where did that stuff come from, you know? Can we get to that level of explanation? I don't know. But it is remarkable that if you ask what happened a millionth of a second after the Big Bang, it's not really that controversial any longer, right? Even though there's a lot of argument in the field, and it's very heated right now, I should say, regarding what is the right theory of the Big Bang? What is the right theory of early universe cosmology, where I mean early, much earlier than a millionth of a second? A lot of dissent, a lot of, uh, uh, heated arguments about that.

   8. LFLex Fridman1:08:01

      No pun intended.

   9. BGBrian Greene1:08:02

      Yeah, right, exactly. Um-

   10. LFLex Fridman1:08:04

       (laughs)

   11. BGBrian Greene1:08:04

       But, but, but you go like a millionth of a second after that-

   12. LFLex Fridman1:08:07

       Yeah.

   13. BGBrian Greene1:08:08

       ... and, and we're on pretty firm ground. Isn't that amazing, right-

   14. LFLex Fridman1:08:11

       Yeah.

   15. BGBrian Greene1:08:11

       ... to, to understand, you know, what happened from that point forward? But to go back is, is, is controversial. So there is this theory called inflationary cosmology, which I would say has been the dominant paradigm since, uh, early 1980s. So what does that mean? Roughly 40 years now it's been the dominant cosmological paradigm, and it makes use of a curious feature of Einstein's general Theory of Relativity, his theory of gravity, where Einstein shows us mathematically that gravity can not only be attractive, you know, the kind of gravity that we're used to, things pull together, but it can also be repulsive. And that fact is then leveraged by people like Alan Guth and, and Andrei Linde, and at the time Paul Steinhardt and Andreas Albrecht and others to say, okay, if we had a little nugget in the early universe which was filled with the stuff that yields this repulsive gravity, well that would have blown everything apart.

   16. LFLex Fridman1:09:07

       Mm-hmm.

   17. BGBrian Greene1:09:07

       It would cause everything to swell. Beautiful explanation for what the bang in the Big Bang was. And then people mathematically analyzed the consequences of this idea, and they make predictions for tiny temperature differences across the night sky that in principle could be measured. You send up balloons, you send up satellites with very refined thermometers, and they measure the temperature of the night sky, and the statistical distribution of the temperature differences agrees with the mathematical predictions.

   18. LFLex Fridman1:09:38

       Yeah.

   19. BGBrian Greene1:09:39

       I mean-

   20. LFLex Fridman1:09:41

       It's amazing.

   21. BGBrian Greene1:09:41

       ... you just sort of have to stand in awe o- o- of this insight. So you think, aha, the theory has been established, but scientists are an incredibly skeptical bunch. And some scientists, including one of the people who helped develop the theory at the outset, Paul Steinhardt-

   22. LFLex Fridman1:09:59

       Mm-hmm.

   23. BGBrian Greene1:10:00

       ... comes along and says, well, yeah, it's done, this theory has done pretty well so far, but there are aspects of this theory that are making me lose confidence. For instance, this theory seems to suggest that there might be other universes. Like, how do you make sense of a theory that suggests there are other universes? Or, or there are others who come along and say, this theory seems to, um, talk about length scales that are minuscule even by the so-called Planck length, the sort of shortest length that we can imagine making sense of in a theory of quantum gravity. How do you make sense of that? And so on and so forth. They develop a list of, of things that they consider to be chinks in the inflationary cosmological theory's armor, and they develop other ideas which they claim yield the same predictions as inflationary cosmology for those temperature differences across space but don't suffer from these problems. And then the inflationary cosmology folks say, no, no, no, hang on, you know, your theory suffers from different problems, and, and so the argument goes. It's a healthy debate. Talk about real debates in science. So when you ask what's up with the Big Bang, I don't know right now. Um, if you would have asked me five years ago, maybe even less than that, three or four years ago, I would have said, look, inflationary cosmology has some issues, but the package of explanations it provides is so potent and the issues that beset it are seemingly solvable to me that I would imagine it's going to, in the end, win out. I would still say that today, but I wouldn't say it as loudly. I wouldn't say it as confidently. I think it's worth thinking about alternate ideas, and it could be the case that the paradigm at some point shifts.

   24. LFLex Fridman1:11:47

       Does, uh, dark matter and dark energy fit into the-

   25. BGBrian Greene1:11:49

       Huge.

   26. LFLex Fridman1:11:49

       ... the shif- shifting of the, the explanations for those?

   27. BGBrian Greene1:11:52

       Yeah, certainly. So, so dark energy has, uh, in, in the inflationary theory, is kind of a big mystery. So dark energy is the observational realization in the last 20 years that not only is the universe expanding, it's expanding ever more quickly. Something is still pushing things outward, and the explanation is that there's like a residual version of the repulsive gravity from the early universe, but it's such a strange number. When you write that amount of dark energy using the relevant units in a theory of quantum gravity, it's a decimal point followed by like 120 zeros and then a one.

   28. LFLex Fridman1:12:33

       Mm-hmm.

   29. BGBrian Greene1:12:34

       We're not used to those kinds of numbers in physics. We're used to a half, one, pi, e, square root of two.

   30. LFLex Fridman1:12:44

       (laughs)
10. 1:18:47 – 1:29:09

    Extraterrestrial life

    1. LFLex Fridman1:18:47

       uh, there's an equation called the Drake equation.

    2. BGBrian Greene1:18:49

       Yep.

    3. LFLex Fridman1:18:50

       When we're talking about life, have to ask when, uh, at the highest level first, when you look out there, how many alien civilization do you think are out there?

    4. BGBrian Greene1:19:00

       (laughs) Yeah.

    5. LFLex Fridman1:19:01

       Well, is it zero, one, or many?

    6. BGBrian Greene1:19:04

       So if you say civilization, I would bring my number way down. It could be zero. If you talk about life, I think it could be many. As we were saying before, I think the move from life to consciousness, the kinds of beings that would build what we would recognize as a civilization, that may be extraordinarily...Rare. I hope it's not. You know, as a kid I loved Star Trek. I, I just loved the idea that we would be part of some universal community where, look, experience on planet Earth suggests it doesn't always go so well when groups who are separated try to come together and, and live in some larger collective. But again, as an optimist, how amazing would it be to converse with an alien civilization and, and learn what they've figured out about physics and cosmology, and, and compare notes and, and learn from each other in, in some, some wonderful way. I, I, I love that idea, but if you ask me the likelihood of it, I, I would err on saying it may be so improbable that the conditions conspire to allow life to move to this place of, of consciousness that it might be rare.

    7. LFLex Fridman1:20:27

       It might be oversimplifying things, but just observing the power of the evolutionary process, I tend to believe ... And like, uh, you read different theories of how we went, uh, how homo sapiens evolved, it seems like the evolution process naturally leads to, to homo sapiens or s- or creatures like that or much better than that. So t- to me the, there's several scary scenarios. So, uh, okay, the positive scenario is life itself is really difficult, so that origin of life is difficult. Wh- that's exciting for many reasons because we might be able to prove that wrong easily in the near term by finding life elsewhere.

    8. BGBrian Greene1:21:14

       Sure.

    9. LFLex Fridman1:21:16

       The scary thing to me is if, uh, uh, life is easy and, uh, there's plenty of conscious, intelligent civilizations out there and we have not obviously made contact, which means with intelligence and consciousness comes responsibility and, uh, ultimately, uh, destruction.

    10. BGBrian Greene1:21:39

        Yeah.

    11. LFLex Fridman1:21:40

        So with power comes great responsibility, and then we end up destroying ourselves. That's the, uh, the scariest. The, the positive I guess version is that maybe we're being watched, uh, sort of like there's a transition to where you don't wanna ruin, uh, the primitive villages out there, and so there's a protective layer around us.

    12. BGBrian Greene1:22:04

        Yeah.

    13. LFLex Fridman1:22:04

        And they're, they're, they're watching. So where, where do you in these possible explanations for the Fermi paradox, why haven't we contacted aliens-

    14. BGBrian Greene1:22:12

        Yeah.

    15. LFLex Fridman1:22:12

        ... do you, do you land on?

    16. BGBrian Greene1:22:13

        Well, uh, I think the most straightforward explanation is that there aren't any. Now, there are many other explanations too, so I ... You can't be dogmatic about things that are just sort of gut feel, but y- you know, one of my favorite Twilight Zone episodes, I don't know (laughs) if you ever saw this one, where, you know, this alien civilization finally comes to planet Earth and, and gives us this book that they really want us to, to have and to hold. And it's in this foreign, you know, language, we don't understand it. The cryptographers, they desperately try to decipher it as humans are going to visit this other alien planet, and they're all sending back postcards how wonderful it is and so forth, and they, they finally d- decipher the title, it's To Serve Man. And everyone's so thrilled, "Oh, they're here to serve us, it all makes sense." And then just as one of the final cryptographers is going onto the alien ship, his, his helper runs and says, "I've deciphered the rest of the book. To Serve Man, it's a cookbook." You know? So... (laughs)

    17. LFLex Fridman1:23:16

        (laughs)

    18. BGBrian Greene1:23:17

        You know?

    19. LFLex Fridman1:23:17

        Yeah.

    20. BGBrian Greene1:23:17

        So, so yeah, is that ... Is (laughs) is that a, is that a possibility? Sure, you know, and, and so could they be watching us, and just sort of waiting for us to, uh, get to a, a mature enough level? I don't know. It strikes me ... Well, you know, I think it'd be better to have this conversation after the James Webb Telescope. I mean, I do think that, um, if we look at the atmospheres of many planets, I mean there's now an estimate now that there's on order of one planet per star on average. So we've long known that, you know, the galaxy, hundreds of billions of stars, numbers of galaxies, hundreds of billions of galaxies. I mean we're talking about hundreds of billions of hundreds of billions of planets

    21. NANarrator1:23:57

        Enlightening.

    22. BGBrian Greene1:23:58

        You know, and if we start to survey some of these planets, and one after the other after the other we just sort of find no evidence for any of the biological markers. It could be of course maybe life takes a, a radically different form. It would be hard to know that. But I think, you know, that would at least give us some insight on the life question. But I just don't see how we get insight on the civilization or consciousness question without, you know, the direct connection, and, and it strikes me that if consciousness is ubiquitous, let's say life is.

    23. LFLex Fridman1:24:33

        Mm-hmm.

    24. BGBrian Greene1:24:34

        I'm willing to grant that. If consciousness is also ubiquitous, then I don't understand why they haven't been here, or why there hasn't been

    25. NANarrator1:24:42

        (laughs)

    26. BGBrian Greene1:24:43

        Because presumably they should be much further ahead of us. How unlikely would it be that we're like, of all consciousness in the universe, we're the most advanced?

    27. LFLex Fridman1:24:53

        Mm-hmm.

    28. BGBrian Greene1:24:53

        That would be such a special place for human beings that it's hard for me to grant that as a likely possibility. Rather, I think we're kind of run-of-the-mill, and there are many who are far more advanced than us, and I don't think that they would expend the energy to hide themselves. So I don't think they care enough.

    29. LFLex Fridman1:25:12

        And so I ... See, see, that's actually what I, I believe, that there's uh, uh, a very large number of civilizations that are far more advanced than us, but my sense is that humans are exceptionally limited, both in our direct sensory capabilities and our physics, our tools of, of sensing, that just like with the string theory and the multiple dimensions, we're just not ... Like, it's like-... I honestly believe there could be stuff in front of our nose that we're just not seeing. We're ... 'cause we're too dumb, too, uh, too much hubris, and, I mean, it's, uh, a bunch of stuff, and too ignorant as to, uh, to, to, to the fabric of reality, all of those things.

    30. BGBrian Greene1:25:55

        Yeah.

Episode duration: 1:45:44