Brian Greene - The Mind-bending Physics Of Eternity | Modern Wisdom Podcast 308

1. 0:00 – 0:39

   Intro

   1. BGBrian Greene0:00

      When you realize how unlikely it is that collections of particles would come together to yield a living system called a human being, and how spectacular it is that this collection of particles called a human being can invent, manufacture notions of value and meaning and purpose, how spectacular is that? (wind blows)

   2. CWChris Williamson0:21

      Brian Greene, welcome to the show.

   3. BGBrian Greene0:24

      Thank you.

   4. CWChris Williamson0:25

      Thank you for being here. I am a massive fan of your work. I'm very, very glad that you're joining me today.

   5. BGBrian Greene0:30

      Oh, thank you. That's great to hear.

   6. CWChris Williamson0:32

      We hear a lot about the big bang and the beginning of the universe 13 and a bit billion years ago, but I wanna start at the end.

2. 0:39 – 11:15

   The End of the Universe

   1. CWChris Williamson0:39

      Have you got any predictions for the end of the universe? If the big bang is when time began, then when will time stop?

   2. BGBrian Greene0:46

      Well, we don't know. But there certainly are ideas that people have developed, so it's not as though we're just shooting in the dark. The most straightforward interpretation of the data and the mathematics suggests that the universe may continue to expand forever. Forever's a kind of funny concept. It's an idea where time wouldn't literally end, but en route to that eternity, everything that we know about will end. Every star will end, every galaxy, every planet. Matter itself will, according to some of our cutting-edge theories, disintegrate into a spray of more refined particles, electrons, neutrinos, that will just continue to waft through that ever-expanding cosmos. So we don't know that that's how things will end up, but if you were to ask me to place bets, based on what we know today and what we've observed today, that would probably where the bulk of my money would go.

   3. CWChris Williamson1:45

      Is that what's referred to as the big freeze?

   4. BGBrian Greene1:48

      It is, because the universe will just continue to get ever colder as it gets ever larger. And weirdly enough, it's also referred to as the heat death. It seems to be a kind of tension between the big freeze and the heat death. But they're actually the same thing, because the idea is that you'll reach a kind of equilibrium, where every place in the universe will come to the same temperature, and it's that equal distribution of heat that is what we refer to at the heat death. But, but the temperature, the common temperature will be so low that you can also think of it as a kind of big freeze.

   5. CWChris Williamson2:26

      What is a way that people can wrap their heads around how far away from us that is now?

   6. BGBrian Greene2:33

      Uh, that's a tough one. I, I have a metaphor that I like to use when taking people on a journey toward the far future. I use the Empire State Building in Manhattan, where I envision that every floor is 10 times the duration of the previous floor in this sort of poetic representation. So the ground floor is one year, the next floor, 10, the next floor, 100. So it's an exponential scale, where 10 to the floor number is representing the year that you're on at a given floor. And that approach takes you to 10 to the 100 years into the future. Today, we're 10 to the 10 years from the big bang, so we're on the 10th floor. So everything that we know about from the big bang till today only gets to the 10th floor, and exponentially far into the future as you climb. Now, by the time you reach 10 to the 100 years into the future, we'd be en route, if the ideas that we currently have are correct, we'd be en route toward that heat death. We'd be en route toward that big freeze. But again, if it keeps on going forever, then even the 100th floor of the Empire State Building, 10 to the 100 years in the future, at some point, that will be a mere blink of an eye en route to the (laughs) timescales that we'll ultimately encounter. So it's hard to have a metaphor. It's hard to have an image, but I think the Empire State Building and that exponential growth at least takes you part way toward the incredibly long timescales that we're talking about here.

   7. CWChris Williamson4:02

      What are the final things that are going to be around there? Is it black hole decay? Is it little, um, fluctuations in spacetime? What's left?

   8. BGBrian Greene4:14

      Yeah, so black hole and black hole decay, which is an idea that comes from Stephen Hawking, that's really what made Stephen Hawking, Stephen Hawking, he realized that black holes are not forever, right? You would think that if a black hole, I think as everybody's familiar, if it's always pulling in more material and getting bigger and bigger as it swallows up stars and planets and things in its environment, you would think that a black hole might just last forever. But Hawking realized that black holes can also evaporate. Particles can actually escape a black hole through certain quantum processes. And if you wait long enough, every black hole will disintegrate through this dissipation into particles, and indeed, by 10 to the 100 years into the future. In fact, that's why the Empire State Building analogy is really well-suited. Basically, all black holes, by that point, will have just evaporated, and they will have given off these particle sprays that will waft through the void. So when you ask what will be left in the far future, even black holes will not be left, as far as we know. We suspect that all black holes will be gone. So the only thing that will be left will be the most refined, the most stable elementary particles around. Maybe refined is the wrong word. It's really stability that matters. And so these particles will be wafting through the darkness, and then you're right, there will be quantum fluctuations.

   9. CWChris Williamson5:46

      That's the word I meant.

   10. BGBrian Greene5:48

       So, so quantum mechanics, that's still around, uh, in terms of a governing law, will allow small energetic fluctuations to appear, disappear, and sometimes those fluctuations might be large. They're more rare if they're large, but if you have infinite time on your hands, then rare things can happen.And so rare fluctuations where particle collections and energetic collections momentarily form, stick around for, for some period of time and then dissipate, that can happen too en route to eternity. So if you wait long enough, some weird things can happen because weird things can fluctuate out of nothingness.

   11. CWChris Williamson6:31

       That's something I took away from reading your book, that when you scale things up, either in terms of time or space, you get some incredibly odd outcomes. There's only a ... There's a, a relatively finite number of combinations of how you could piece particles together within the volume of space that you make up, right?

   12. BGBrian Greene6:52

       Yeah.

   13. CWChris Williamson6:52

       Which is one of the reasons that people think if the universe is infinite, that there's essentially an infinite number of Brians and, and Chrises-

   14. BGBrian Greene6:59

       Yeah.

   15. CWChris Williamson6:59

       ... having slightly altered versions of this conversation.

   16. BGBrian Greene7:03

       Yeah, that's a very strange idea, but one that naturally comes out of the mathematics. It's, again, one of those ideas that it's hard to fully internalize because it's so bizarre. But if space, as you say, does go on infinitely far, so not in a temporal quality, but in the spatial direction, which is ... I think if you were to survey most physicists w- who think about this and say, "Does it go on forever? Does space go on forever?" I think the, the reaction among the majority would be, "It does go on forever."

   17. CWChris Williamson7:32

       Is that right?

   18. BGBrian Greene7:33

       And I think that-

   19. CWChris Williamson7:33

       That's interesting.

   20. BGBrian Greene7:34

       I think that's really where the, the, the general zeitgeist is when it comes to thinking about the grand expanse of space. And, and you're absolutely right. So in any given finite volume of that space, there's a finite amount of energy, a finite number of distinct ways in which that energy can be manifested in terms of particle configurations. And so if space goes on infinitely far, there aren't enough distinct configurations to continue to populate those different regions with a different configuration of particles. The particle arrangement has got to repeat. And if it repeats, then the universe as we know it would repeat. We are just collections of particles, you and I, right? So if the configuration repeats, you and I are out there too, as you're suggesting, and we're out there even more times with slight variations on the reality that we know about. So maybe, you know, I've got, I've got the show and I'm interviewing you-

   21. CWChris Williamson8:33

       (laughs)

   22. BGBrian Greene8:33

       ... you're the physicist, you know, that, that kind of thing would happen out there. So, so yeah, I mean, these, these bizarre ideas are not just flights of fantasy. They do emerge from the laws of physics under certain modest assumptions, like space goes on infinitely far.

   23. CWChris Williamson8:50

       If that's the current on-trend, uh, idea amongst physicists, are they talking about the universe with matter beyond the observable universe, or are they talking about some sort of structure beyond a universe, our universe, that is outside of the observable universe?

   24. BGBrian Greene9:08

       Both. Both. And again, I'm, I'm ... I guess, m- maybe I spoke too quickly. I don't wanna speak for my colleagues. They may like do a survey and say, "Hey, Brian Greene, you're wrong," right? Y- the vast majority of us don't think in this way, but it is the case that, uh, a commonly held notion is that, number one, space can go on perhaps infinitely far, in which case you would have these other domains of reality that are contiguous with ours, right? And that's that first version of other stuff beyond the horizon, beyond the observable universe. But the common view for cosmologists today is that a theory called inflation, inflationary cosmology may well be the explanation for the Big Bang. So what banged in the Big Bang is a big question, and there's a proposal on the table that there's a certain kind of fuel called the infoton field, and the energy in that fuel may have driven a period of repulsive gravity that pushed everything apart. And if that's the case, the interesting conclusion is the math shows that it's virtually impossible to use up all the fuel, which means that the fuel that gave rise to our Big Bang would be left over. There'd be some left over to yield other Big Bangs, and those Big Bangs would leave over some fuel which would drive yet further Big Bangs. And that's that second version of beyond that you're referring to. Those Big Bangs would, would be outside the domain of reality that we would think about even if we're allowing space to go on infinitely far. You might think, "Well, if it goes on infinitely far, then that must exhaust everything, right?" I mean, there can't be something beyond the infinite of space going on infinitely far, but that isn't correct. The weirdnesses of space and time allow for our domain to be infinitely large and yet there to still be other Big Bangs-

   25. CWChris Williamson11:08

       (laughs)

   26. BGBrian Greene11:08

       ... giving rise to other realms which themselves can be infinitely far. So yeah-

   27. CWChris Williamson11:14

       Did it-

   28. BGBrian Greene11:14

       ... kind of an infinity of

3. 11:15 – 19:33

   Thinking Like a Theoretical Physicist

   1. BGBrian Greene11:15

      infinities.

   2. CWChris Williamson11:16

      Did it take time for you to dispense with the common person all of the assumptions that me and everybody that's listening has when we're talking about this stuff, that you're having to remind us about the biases that we come into this, our lack of capacity to understand what infinity is and stuff like that, timescales? Is there, like, some sort of deprogramming that advanced physicists and mathematicians go through, some sort of, like, onboarding camp that they need to go through to get rid of that thinking pattern?

   3. BGBrian Greene11:47

      Yeah. In fact, it's not even as easy as you suggest. I think it's a lifetime of reprogramming. I mean, our intuitions are built up from the very same experiences that everybody else has in everyday life, where, you know, there's a beginning, a middle and an end to things. You know, there's a finite size to things. There's a finite lifetime to things, right? Since ...... that's how we live. That's how our, our intuition has been built up. And it's more than just the intuition of a given lifetime. We have behavioral perspectives and predilections that emerge from our own deep physiology. Our brain patterns, our brain structure, the, the details of our DNA, all of these things carry an imprint of our collective experience across thousands of generations. And our forebearers, wandering around the African savanna, they had the everyday experiences that matter to survival. And yet when we go beyond the everyday experiences and examine the quantum realm, we examine the relativistic realm, the cosmological realm, everything that our math, some of which has been confirmed by observations, tells us is that the everyday experiences are not a good guide to how the world actually works. So we are, in a lifetime as a physicist, a lifetime of tension between what we experience collectively as a species and what we learn about the universe through observation.

   4. CWChris Williamson13:20

      Isn't it interesting that the consciousness that we have, maybe it's there so that we can correctly predict what other people are thinking so that we're more social beings? Or maybe it's there for any one of a number of other explanations for why consciousness is here. Isn't it insane that one of the byproducts of that is that it's given us this capacity to be able to start to grasp at infinities, to be able to push the limits of something? It, we were not designed to think about this, and yet-

   5. BGBrian Greene13:50

      Yeah, we've gone beyond our design specs.

   6. CWChris Williamson13:52

      ... it's, we've o-

   7. BGBrian Greene13:53

      Absolutely.

   8. CWChris Williamson13:53

      ... we've overclocked our brains.

   9. BGBrian Greene13:54

      Totally.

   10. CWChris Williamson13:54

       The same way that computer hackers overclock their computers, we've overclocked our brains. The same way that a light gives off light, but as a byproduct, it gives off heat. Maybe this is because it's given us this particular structure of things to do one service, pro- s- social animals, whatever it might be, that's also just got this slight side effect. And you guys in your industry are just leveraging that and twisting that as hard as possible.

   11. BGBrian Greene14:20

       Yeah. No, I think there's, I think there's a version of that idea that applies to many fields. Uh, but I think it is most pronounced for physics and mathematics. I mean, what, what we do is, as mathematically oriented scientists, physicists, we seek out patterns in the world, right? That's what we're do. We are pattern recognition machines that take in the world and try to find the regularities, and by encapsulating those regularities in mathematical equations, we're then able to go even further in our understanding. Now clearly, pattern recognition served us well in the ancestral environment. I mean, those of our ancestors who knew where to go the next day to get the food, those who knew what was gonna happen when there was, you know, thunder and lightning, and recognized the pattern that that was the signal to seek shelter, right? Those of our forebearers who could catch the patterns had a leg up in the battle for survival, and therefore, pattern recognition became intrinsic to what we do. But you're right. We are pushing that capacity well beyond the needs of survival and trying to find patterns in things that just don't seem to matter to our-

   12. CWChris Williamson15:36

       (laughs)

   13. BGBrian Greene15:36

       ... everyday survival, right? I mean, you don't need to know about the Big Bang or the, the weirdness of the electron's magnetic moment, you know, or quantum tunneling or quantum entanglement or inflationary cosmology or the infinities of space. You don't need to know that stuff to survive. And you can make an argument that those of our forebearers who did think about these things, perhaps they're the ones that actually were the ones that got eaten, right? I mean, if you, if you sat down on the African savanna to contemplate the, the Schrodinger equation and quantum evolution of electrons, you didn't notice, you know, the, the, the lion that was about to eat you, right? You know? So, so you could even say that it goes against survival, but, but we've gotten to a place in the modern world where we've got the luxury to do things that do not help us in the ways that pattern recognition was initially meant to help us. And it takes us to some pretty weird and wonderful places.

   14. CWChris Williamson16:35

       It's so fascinating that for a long time, the environment shaped our evolution because it caused the evolutionary forces that required us to become fitness-adapting creatures. But now that we shape our environment, we are shaping what we will evolve and adapt into in the future. Uh, I often think about how evolution at the moment, when the world is changing as quickly as it is, is basically pointless, because if you did get a slight genetic mutation, whatever environment it grew up in that was adaptive, by the time that it then passed that on to its children, it wouldn't be useful anymore.

   15. BGBrian Greene17:12

       Well, it's not completely true. You w- you might think that, and there is certainly controversy on this point, but there are some researchers who claim that there is real world evolution that we can measure and see today. They claim, for instance, that the heights of certain males in certain parts of the world is growing over time because females are-

   16. CWChris Williamson17:36

       Ah, a selection effect. Yeah.

   17. BGBrian Greene17:36

       ... selecting males based on height, and so there's a small differential in the reproductive, uh, yield among males that are taller, seeding the world with, uh ... You know, and for someone like me, average height, you kind of, like, go off to the corner and hang your head low when you hear that kind of data. But, uh, but, but, but the other side of it though is it's not only that we are shaping the environment that then is back reacting on our own evolutionary progression, we're interceding in...... the evolutionary process itself. So it used to be that mutations were these randomly occurring events, and those that happened to enhance our ability to survive and reproduce were the ones that hung around, and the mutations that didn't do that, they quickly died away. But now you don't just have mutations from random events. We're going in, and we're affecting the human genome directly. I mean, this are, this is only gonna become ever more prevalent toward the future. Uh, and look, there, there, there, there are clearly some very powerful things that we can do with that. I mean, look at the thing that we're dealing with right now, right? The coronavirus. So now we have vaccines that have been manufactured according to the techniques that allow us to get in and have a molecular control over certain kinds of nucleic acids, right? So, so, so it's powerful, but it also suggests that when we start to do these manipulations on human beings, which already we're doing, that's going to have its own evolutionary trajectory that will be somewhat different from the one that has been in control for, you know, millions of years.

   18. CWChris Williamson19:27

       Yeah. We're not just cargo aboard the space ship humanity, are we? We're crew as well.

   19. BGBrian Greene19:31

       Yeah. Yeah. Exactly.

   20. CWChris Williamson19:32

       And we're contributing

4. 19:33 – 25:00

   Explaining Time as a Phenomenon

   1. CWChris Williamson19:33

      to the direction. How do you explain time to people as a phenomenon?

   2. BGBrian Greene19:38

      Well, I think most people have an intuition about time, so the battle is to leverage that intuition and convince people that the things that they hold dear about time, some qualities are correct, but some qualities science has revealed to just not, not be the right way of thinking about things. So most of us have a sense that time for you, time for me, time for everybody else is basically the same. That time elapses at the same rate regardless of what you're doing, where you are, the gravity you're experiencing, the motion that you may be executing. That's plain wrong. Right? I mean, Einstein taught us. Now, in 1905, what are we now, 2021 or something? So, you know, uh, I can't subtract, but, what, 115, 116 years ago? He, he showed (laughs) us in the most direct way that that's just not correct. If you're in motion, your clock ticks off time at a different rate compared to somebody who relative to you is at rest. If you're near the edge of a black hole, time elapses for you at a different rate compared to someone not experiencing that gravitational field. That's an extreme example, but to go back to the Empire State Building, if you're at the top of the Empire State Building, your watch is ticking off time a little more quickly than the clock of someone on the ground on 34th Street and Fifth Avenue. That sounds crazy, but that is how time actually works. So I find that if you take people sequentially through these new qualities of time that are unintuitive, we haven't directly experienced them, and then explain experiments... I mean, literally people took atomic clocks, put one on the tarmac, put one on, on an airplane, and flew that plane around the world, and then they compared the clocks when that airplane landed, and these incredibly precise atomic clocks did not agree. And it wasn't because the plane was kinda jostling the clock. (laughs) It wasn't like... it was a smooth ride, smooth sailing. And yet because that clock was in motion and experiencing a different gravitational field because it was up in the air compared to the clock on the surface of the Earth, gravity gets a little weaker up there a little further from the center, the clocks ticked off time differently. There it is.

   3. CWChris Williamson21:56

      So that-

   4. BGBrian Greene21:56

      And so, so yeah.

   5. CWChris Williamson21:57

      So that explains the weirdness of time-

   6. BGBrian Greene21:59

      Yeah.

   7. CWChris Williamson21:59

      ... but what about it as a fundamental phenomenon? What is it? What's it doing?

   8. BGBrian Greene22:05

      As do which phenomenon? Sorry.

   9. CWChris Williamson22:06

      As time.

   10. BGBrian Greene22:07

       Oh, I don't-

   11. CWChris Williamson22:07

       What-

   12. BGBrian Greene22:07

       ... know what time is.

   13. CWChris Williamson22:08

       (laughs)

   14. BGBrian Greene22:08

       (laughs) I wish I could tell you. That's the weirdest thing of all, right? So we can measure this quality of the world called time. We can measure it to incredible accuracy, and when we do that, we can reveal features of time that are unexpected, you know, it ticks off at different rates in different environments. But if you ask me, "What is it that you are measuring?" I don't know. I mean, people have struggled to give an answer. One answer is, well, time is that quality of the world that allows change to take place. Okay, I, I can sort of figure that. That sort of makes sense. Uh, time is that quality of the world that ensures that everything doesn't happen all at once. Okay. Yeah, kind of, but does that really fill you with a deep sense of understanding of what time itself is? It doesn't do it for me, and, and so I think many of us suspect that the next revolution in understanding will be one where we can finally give a deeper explanation. And, and there are some who suggest in my own field, string theory, is starting to give evidence for this. Some think that part of the reason we're unable to give a real compelling definition of time is because time itself is not as fundamental as we might have thought, that there's a deeper level of reality where we'll find that time is made up of something finer, something more fundamental. I mean, you look at any piece of matter, and if I asked you like, "What is," I don't know, "what is, what is wood?" You could start to give me some answers, but they may not be that compelling. But then if you get down to the molecules and atoms and you talk about the atoms that make up the molecules that make up the wood, and you talk about the protons and the neutrons in the nucleus, and the electrons, and you talk about the quarks inside of the proton, now you get to a place where you're like, "Oh, okay, I get it." That's like the, the most basic ingredient. You put that together, and if you put it together in the right way, you get wood.

   15. CWChris Williamson24:17

       (laughs)

   16. BGBrian Greene24:17

       Ah, I, I, I can sorta get that. And maybe the same thing with time-So maybe the time is made up of some molecule. I put that in, you know, air quotes. I don't really know what that means. That, that molecule of time may be made up of atoms of time. Again, air quotes, I don't really know what that means. But, but if we could identify those fundamental constituents, then we could say, and if they come together in the right way, voila, you get time. And if we could do that, we can't yet, but when and if we can do that, I think that would give us that deeper sensation that we more fully understand what it is we're talking about when we invoke the word time.

5. 25:00 – 37:32

   Entropy & Thinking

   1. BGBrian Greene25:00

   2. CWChris Williamson25:00

      That's so cool. That's awesome. Can you talk about the relationship between entropy and evolution that you go through in your book? I thought this was absolutely fascinating.

   3. BGBrian Greene25:09

      Yeah, no, I'd be happy to do that. And, uh, as you see me bobbing back and forth, I clearly didn't calculate the angle of the sun.

   4. CWChris Williamson25:16

      (laughs) Spin yourself around if you need to.

   5. BGBrian Greene25:18

      That's what's happening. (laughs) It's binding me in whatever position I sit.

   6. CWChris Williamson25:21

      (laughs)

   7. BGBrian Greene25:21

      But, uh, yeah, so, so I like to think about the unfolding of reality as this kind of interplay between these two conceptual frameworks. One of which is the drive toward ever greater disorder, which is encapsulated by this notion of entropy, and perhaps people have heard of the second law of thermodynamics, which gives us a nice mathematical and intuitive understanding of why objects and things and situations tend to go from order toward disorder, that move from an orderly environment to a more disorderly environment, which we can frame mathematically. That's what the second law of thermodynamics encapsulates. So that's a kind of breaking down, a withering away, a disintegration. The flip side, which is entropy, is a force that drives things to get ever more refined structure. When you have a battle among living systems, or even before that, battle among chemical systems, where those configurations that are best adapted to their environment are the ones that are going to win, that are going to prevail, you can see a drive toward ever greater nuance and refinement. Because the more refined you are, the better adapted you are, the better chance you have of surviving. And so you kind of have these two forces at work. Entropy tends to drive toward disintegration. Evolution tends to drive toward ever more refined configurations. And you can trace these two forces right through the evolution of the universe from just after the Big Bang. Evolution we tend to think about at the level of living systems, but as I mentioned, once a molecule learns how to make copies of itself, to replicate, those molecules that can replicate faster, swifter, with greater economy and stability, those molecules are going to win in the sense that they're going to be able to grab at more raw materials from the environment and make more copies of themselves. So this drive toward increased refinement that evolution by natural selection gives us is something that has been with us even before living systems. Living systems are an interesting development along that evolutionary trajectory. And so there is this interplay, and you can trace it from the Big Bang till today, and what I do in the book is I trace it also from today arbitrarily far into the future, where again we see these forces at work guiding what takes place as we walk that trajectory toward eternity.

   8. CWChris Williamson28:03

      Is it fair to say that humans locally reverse entropy then?

   9. BGBrian Greene28:08

      In a sense, yes, but you have to be very careful with what you mean by that. I like to think of it as a kind of entropic dance that I've given a name. It's called the entropic two-step. And what I mean by the entropic two-step is the second law, and you hear the word law, you're like, "Okay, then it has to always be true." That's not even completely true. The second law is a little bit different. What the second law says is that there's an overwhelming likelihood that overall entropy and disorder will go up, but that doesn't prevent entropy and disorder from going down in some regions so long as there's a compensating amount of entropy that goes up in the wider world. And that's the two-step. Entropy can go down over here so long as it goes up over there in some surrounding region. And so human beings, sure, we constantly force entropy to go down. We constantly force order to go up in our local environment, but when you look very carefully at the detailed process by which we force entropy to go down, there's always entropy that's generated, heat and waste that is generated, that we expunge to the wider environment. So we can maintain order for a- a while because we can cause disorder to be emitted outside, but sooner or later, entropy does catch up with us. So it's a local phenomenon that we can carry on with for a period of time. Ultimately, we lose that entropic battle.

   10. CWChris Williamson29:47

       I remember speaking to Adam Frank on the show, and he was talking about how one of the universals he thought we would find with any intelligent civilizations on other planets would be an increase in heat, would be some sort of global warming, because inevitably when you try and wrangle the environment to do what you want it to do, whatever that is, you're going to give off these waste products.

   11. BGBrian Greene30:10

       Yeah. Yeah. Uh, so Adam, I, I agree with that statement, and it actually goes back to a statement of, uh, Albert Einstein. So Albert Einstein once said that he viewed all-... understanding of the universe as provisional, right? Theories come along, they get developed, they get replaced. He even viewed his own general theory of relativity as provisional, that one day it would be replaced. But he said when it comes to the second law of thermodynamics is that, "I don't view that one as provisional. I view that one as one that will always be with us." And indeed, the second law, by virtue of saying that entropy goes up, means that heat will ultimately always be generated by any system. And certainly a civilization of intelligent beings who want to preserve order in their local environment, they will only be able to do that at the expense of generating heat that wafts outwards. And so yes, that is a, a general tendency. And you might ask, "So why was Einstein so confident about this i- idea?" And that takes us, uh, uh, a little far afield, so I won't try to go into the detail, but I'll simply note that when you look at how you establish the second law of thermodynamics, it doesn't involve really any detailed math or complex ideas. It's simply the statement that there are more ways for a system to be disordered, more ways for its ingredients to be arranged that would be characterized as disordered compared to the number of ways that those ingredients can be arranged to look orderly. So it's simply a counting of the number of configurations of the particles, and there's an overwhelmingly large number that yield disordered systems, very few, relatively speaking, that yield ordered systems. I mean, you notice, you go into a kid's bedroom, right? It's a mess usually because it's just so much more likely that the ingredients, the good, the games, the books, the toys will be in a disordered arrangement. It takes a very careful arrangement of the ingredients to look orderly, and that's in s- in a nutshell why Einstein had such confidence in the second law of thermodynamics.

   12. CWChris Williamson32:18

       Because of a toddler's bedroom?

   13. BGBrian Greene32:20

       Toddler's bedroom. That's all it was. That was the inspiration.

   14. CWChris Williamson32:22

       (laughs)

   15. BGBrian Greene32:23

       (laughs)

   16. CWChris Williamson32:24

       Uh, you draw a line between entropy and thought and this impermanence of thought as well.

   17. BGBrian Greene32:30

       Yeah.

   18. CWChris Williamson32:30

       Can you take us through that?

   19. BGBrian Greene32:32

       Yeah. You know, so if you push these ideas even further and you say to yourself, "Look, any physical system of any sort has to generate heat to preserve its own inner order," if you take that as a, as a given, and as I said, they're very simple, basic arguments that lead us to that place, then you can say to yourself, "Look, let me consider a thinking system." Any thinking system, regardless of what it might be, a human brain, a computer, a weird thing in the far future that we can't imagine right now that's able to think, any thinking system, in order to have thought, must generate heat because it's a physical process. And if you follow that through into the far future of the cosmos, you find that in the far future, about the 50th floor of the Empire State Building, to go back to our little analogy 10 to 50 years into the future, a thinking system that generates heat, the universe will not be able to absorb that heat. It will not be able to take that heat in at a sufficiently fast rate, which means that any thinking system in the far future, if it thinks one more thought, it will burn up. It will fry in the heat generated by the entropy produced by the very process of thought itself. And that comes to the weird conclusion then that thought will come to an end. Thought itself is a product of physical processes that cannot be sustained indefinitely in the universe.

   20. CWChris Williamson34:03

       Isn't that fascinating that thinking is the thing which allows us to get the insight into how the universe works? It's also the process by which we may be able to slow down some of the processes that would lead to our destruction, but ultimately, it is the cause of our destruction.

   21. BGBrian Greene34:24

       Yeah. Yeah. It is funny how, you know, the snake eats its own tail, you know, once again, you know? Um, and you can even say it's also kind of remarkable that through the process of thought we can understand that this is the fate that awaits the process of thought.

   22. CWChris Williamson34:43

       You can watch the tail going into your own mouth predict it happening.

   23. BGBrian Greene34:45

       Yeah, yeah.

   24. CWChris Williamson34:46

       Yeah.

   25. BGBrian Greene34:46

       Yeah, yeah. And there's nothing you can do to sort of divert that tail from entering the mouth. There's no way that you can subvert the physical processes that ultimately will spell our own destruction.

   26. CWChris Williamson35:00

       I've read some Stephen Baxter sci-fi, and in those he likes to play around with alien civilizations very, very far into the future, and one of the propositions that he puts across is these civilizations would basically upload themselves into some form of computer and then put themselves to sleep until the universe is significantly colder, and then they would be able to run their operations and it wouldn't get so hot. I'm guessing that's something you've come across-

   27. BGBrian Greene35:26

       Yeah.

   28. CWChris Williamson35:26

       ... as well.

   29. BGBrian Greene35:27

       Yeah. In fact, it goes back to insights of a famous physicist named Freeman Dyson, who sadly passed away not too long ago. He played a key role in the early developments of quantum mechanics and had all sorts of interesting creative ideas, and one that he had was exactly what you're suggesting, that perhaps a living system, a civilization could preserve its existence by going through long periods of hibernation. So they think a couple thoughts, and then they go to sleep and allow the heat generated by those thoughts to dissipate. And it may take a long time for that heat to dissipate in the far future when the universe is, you know, very cold and things are moving very slowly, but then they'll wake up, and they won't even know they've been asleep because they weren't thinking while they were asleep, right? So they will wake up, and they'll have another couple thoughts, and then they go back to sleep and allow those thoughts to dissipate. And in that way, Freeman Dyson thought he had established...... a strategy by which any living system could exist forever. But what he didn't know at the time was that our universe is not just expanding, it's accelerating in its expansion. This is a discovery in 1998 that won the 2011 Nobel Prize. And if you take that idea seriously and imagine that the universe will continue to speed up in its expansion, then it turns out that Dyson's argument doesn't quite work. And the reason it doesn't work is because there's a source of heat that the accelerated expansion gives rise to, and that source of heat permeates the universe, permeates space. And it's that heat that prevents the universe from absorbing the additional heat that a thinking system would generate through the process of thought. And when you take all that into account, you see that living systems cannot live forever, unfortunately, or maybe fortunately-

   30. CWChris Williamson37:31

       (laughs)
6. 37:32 – 44:22

   What's a Boltzmann Brain?

   1. BGBrian Greene37:32

      perspective. (laughs)

   2. CWChris Williamson37:32

      Yeah. What's a, a Boltzmann brain?

   3. BGBrian Greene37:37

      A Boltzmann brain is kind of a weird fluctuation of a particle configuration, going back actually to the very first question that you asked me when we started this conversation. So in the far future, there will just be these particles wafting through the void, governed by quantum mechanics, and, and every so often en route to eternity, those particles can kind of bang into each other in an interesting way. It won't happen often, 'cause these particles are mostly isolated, but again, if you're waiting infinitely long times or arbitrarily long finite times, weird things can happen. And one of the weird things is particles can bang into each other and create or recreate a human brain out there in the void. And that brain floating in the void can have a thought or two. And these are called Boltzmann brains. Ludwig Boltzmann, he didn't actually describe these things, but using his ideas, physicists of more recent vintage have (laughs) developed this idea. And the weird thing is, imagine that that brain floating in the void just happens to have exactly the same particle configuration as my brain does right now, right? You might say, "Well, that's rare," and I'd say, "Yeah, it's rare, but en route to eternity, it's gonna happen." Rare things will happen with, uh, essentially probability one. So that brain floating in the void is gonna think it's me. It's gonna have my memories, 'cause my memories are just configurations of particles inside my head, right? It's gonna have my personality, and my personality is just the configuration of particles inside of my head. So that brain out there in the void is literally gonna be me saying, "Oh my God, how did I get here? What am I doing, you know, floating out here in the void?" Um, and that's kind of a weird, a weird idea. And, and the reason we come to this, it's not, like, for, you know, some kind of comedic turn or something. The reason we, we think about this idea is because you have to ask yourself, what is the most likely way that a thinking system such as ourselves comes to be? And you come to a weird conclusion when you invoke Boltzmann brains, because there's only one biological brain that we know of that's gonna, say, be me, right? Because there isn't enough time for multiple mes to form in the natural biological way. But because eternity is so far along, Boltzmann brains and my brain forming via this Boltzmann random manner, that can happen arbitrarily many times en route to eternity, and so will happen arbitrarily many times. And so there are gonna be, like, a gazillion Brian Greens floating in the void, if you can think about it all of time, and only one of me that forms in the biological manner. So if you ask me, like, who am I and where am I, how'd I get to be, a dispassionate look at the numbers would lead me to say, "I'm a Boltzmann brain that just formed in the void." And the conversation that I thought that we'd been having for whatever, the last half hour or so, it didn't really happen. It's just a configuration of particles inside my head making me think that I've been having a conversation with Chris Williamson. But in the reality, I just formed right now with those memories of fake things that never actually occurred. It's kind of a weird place to get to.

   4. CWChris Williamson40:57

      Wow. That's almost-

   5. BGBrian Greene40:59

      And weird a-

   6. CWChris Williamson40:59

      (laughs)

   7. BGBrian Greene41:00

      But even further though, even weirder is, it, it winds up being a self-defeating conclusion, because the only reason we even anticipate the possibility of Boltzmann brains is because of our understanding of the laws of physics, quantum mechanics and cosmology, and we extrapolate. But if Boltzmann brains are real, then my recollection of having learned quantum mechanics and having learned general relativity, that's also false. And the data that I thought supported quantum mechanics and general relativity and cos-, that's also just a fiction of the particle configuration-

   8. CWChris Williamson41:36

      (laughs)

   9. BGBrian Greene41:36

      ... of my brain right now. So-

   10. CWChris Williamson41:38

       (laughs)

   11. BGBrian Greene41:39

       ... so, so, so it winds up being a self-defeating conclusion, where you kind of come to a skeptical nightmare, where you can't trust anything at all.

   12. CWChris Williamson41:48

       (laughs)

   13. BGBrian Greene41:48

       So most physicists who take these ideas seriously are not really envisioning that we're Boltzmann brains. Rather, we use it as a kind of diagnostic tool to interrogate our theories. And hopefully, we believe we'll come to a point which we've not reached yet, where we'll be able to suppress this possibility of Boltzmann brains, getting our confidence back in the laws of physics as usually configured. But as yet, I would say we're not, we're not quite there. So this is really a, a, a moment of physics in progress as we try to eliminate (laughs) this, this possibility of Boltzmann brains, but we have not fully done so as yet.

   14. CWChris Williamson42:25

       Boltzmann brain is still on the menu. That is-

   15. BGBrian Greene42:27

       Still on the menu. Yeah.

   16. CWChris Williamson42:29

       It reminds me a little bit of the simulation hypothesis, this kind of-

   17. BGBrian Greene42:33

       Yeah.

   18. CWChris Williamson42:33

       ... like, root and then a number of different...... child universes or child experiences that could be going on.

   19. BGBrian Greene42:41

       Yeah. No, it's very similar, you know, this idea that we might be whatever, like in the Matrix or something, that we are just a simulation on some futuristic supercomputer. Um, and it's a similar kind of set of considerations where if we ever are able to create conscious beings in a simulation, then they will follow the same trajectory as with Boltzmann brains and say, "Look, there are a gazillion simulations that can be run, but there's only one real universe that actually formed, and therefore, it's overwhelmingly likely that we're in a simulation just by sort of counting the numbers, just by the laws of, of probability." And that, that's also a weird one, and how do you get out of that one? Well, maybe you don't. Maybe we truly are simulated beings, and maybe you just have to bite the bullet and accept that. Or Nick Bostrom, who is the guy who first came up with the simulation argument out of Oxford, you know, he says, "Well, maybe any sufficiently advanced civilization that could simulate conscious beings on a computer, they also develop weaponry. Maybe they go hand in hand and they blow themselves up, and so you never get to that... to that place." Or some suggest maybe the universe comes to an end before Boltzmann brains or before simulations actually arrive on the scene. That's a possibility too, right? Again, we talked about one way in which the universe could continue to develop and evolve effectively for eternity, but it's not the only idea about the far future. There are other theories that suggest maybe the universe expands for a while then collapses in on itself. A big crunch. The big crunch could wipe everything out before Boltzmann brains even have a chance of forming.

   20. CWChris Williamson44:20

       (laughs)

   21. BGBrian Greene44:21

       (laughs)

   22. CWChris Williamson44:21

       It's so

7. 44:22 – 51:34

   Do Physicists Have Existential Crises?

   1. CWChris Williamson44:22

      good. It's so good. Do many physicists encounter existential crises when they start to think incredibly deeply about this sort of stuff?

   2. BGBrian Greene44:32

      I mean, some have. You know, I mean, Ludwig Boltzmann, the Boltzmann of Boltzmann brains, you know, he died by his own hand.

   3. CWChris Williamson44:41

      Did he really?

   4. BGBrian Greene44:41

      He died by, by suicide. Now, look, I don't want to be armchair psychologist, and nobody else can. We don't know what was going on inside his head that day. And, uh, it was in Trieste, Ill- Italy, I believe it was 1905, 1906. He sent his, um, wife and family, I can't remember how many kids, maybe one or more, out, and when they came back they found him hanging, you know. Um, so w- we know... Was that some other, you know, just mental illness that, that was driving it? I don't know. But certainly he was confronted with these weird ideas. He was confronted with a physics community that didn't accept a lot of his ideas. I... Uh, that certainly may have contributed to it. Um, but in terms of, you know, otherwise stable physicists who go to a dark place because of their realizations in physics, I don't know that many. I do know some, and I, I don't wanna get too hyper-personal here, but I certainly am one of those (laughs) that on occasion has found myself in a less than happy place, a dark place, by, by taking in these ideas in a really full sense. My sense, and again, I don't wanna speak for the community, so I can only give you my personal sense and, and experience of the community, is that most physicists don't take these ideas in at a, at a fully emotional level. Some do. Don't get me wrong, some do. But many just see it as, uh, a mathematical game, where what we're trying to do is have a better explanation of that piece of data, a better explanation of the expansion of space, a better explanation of, uh, stellar processes that yield heat and light and spectra that we can measure with, with great precision. And so if you view it just as sort of a game of symbols that you write down trying to understand the external world, th- then that's it. You just play the game, you enjoy it. If you're lucky you come up with some equation that explains something, it gets you a trip to Stockholm, you know, you meet the, the royalty there and so forth. And, and if it's just that game, then that's the level at which you take it in. But I don't do physics for that reason. Not that I wouldn't mind getting (laughs) the Nobel Prize, don't get me wrong, but what I'm saying is, I do physics because I want to understand reality. I mean, I really want to understand reality. And so for me these ideas are not just about making a better prediction or, or maybe being used for a better gadget if you can apply these ideas. To me it's about, what can this tell us about the universe, reality, and how we fit into this grand cosmic schema? And if you take it in that way, then, for instance, to learn that all structure will disintegrate, to learn that thought itself will come to an end, to realize that your life is this momentary blip on this cosmological landscape, most of which is not inhabited by thinking creatures at all, most of which is not inhabited by complex structures because they've all disintegrated, when you really take that in fully, yeah, it can take you to a dark place. I can tell you that for sure.

   5. CWChris Williamson47:59

      I have some friends who are nurses, student doctors, recently qualified doctors, and I ask them the question as well, do you ever get training about how to separate yourself emotionally from the things that you have to do at work? You have some old lovely lady who comes in one day, she's fine, the next day she's blue, the next day she's dead, and you watch this unfold in front of you. And I think there's a parallel to draw there, that they see it as-

   6. BGBrian Greene48:28

      Yeah.

   7. CWChris Williamson48:28

      ... "Well, this is my job. There are some inputs, there are some processes, and there are some outputs that I need to make with it." But on the flip side I have some friends who are on the verge of leaving or decided to leave or sometimes get troubled by the fact that there is a...... there's an emotional layering on top of the job. And, um, yeah, it ma- it- oddly, it makes me feel, it makes me feel warm towards the physics community that the, those guys, yourself included, are having to pay this existential price internally in order to further our understanding of how the physical world works.

   8. BGBrian Greene49:04

      Well, I deeply appreciate your empathy for us. Uh, and I say that seriously. But I would also say that, uh, I think, I don't know if it's an occupational hazard or a selection mechanism. I, I would not call physicists the most introspective of human beings. And again, I hate to generalize because there are some that are deeply introspective. Um, obviously, I didn't know Einstein. I only know Einstein through his writings. Um, and some of his writings suggest that he was deeply introspective. Now, the way he, he lived his life and the way he treated some of his, um, companions and his female companions suggests that there was a, a disconnect between the introspection that perhaps allowed him to be deeply philosophical about the universe and the introspection that would've made him a, a, a, a better human being in a more conventional sense. So, so it's, it's hard to know. Um, but I, I've had so many students for whom this is just math and it's just calculations, and they would have no patience for, for thinking deeply about what these ideas might mean to them as a human being or what it might mean to their place in some grand cosmological sense. And, and certainly, m- my, my colleagues, you know, I've got some colleague, I'm at Columbia University, some who are very open to these more, more expansive conversations, and some who would just roll their eyes if we were to head into anything that had to do with an emotional response to, to our understanding of the un- "Oh, come on, give me a break," would be, be, be their, their kind of response. And that's fine. It takes all sorts to make a community, a rich and vibrant community. I'm certainly more on the, on the end of, of willing to talk about the emotional response to these ideas. I mean, I mean, the reason I wrote the book is because for my whole life, I've been experiencing an emotional reaction to the deep ideas of quantum mechanics and, and cosmology, and have felt the need to put down on paper a kind of journey, a journey of a physicist who, who's open to philosophical ideas, who's open to psychological ideas, open to artistic and emotional ideas, because to me, the richest way to be in the world is to hear all these voices and to participate in all of these conversations. But I would not say that that's a dominant perspective among my colleagues.

8. 51:34 – 58:33

   Meaning & Purpose in the Universe

   1. BGBrian Greene51:34

   2. CWChris Williamson51:35

      So we've talked about the matter and we've talked about the minds. Where, h- where does the leap come here to get to meaning, and, and why did you decide to put meaning into the book?

   3. BGBrian Greene51:45

      Well, I don't see how you can think deeply about these ideas without at least having an urge for them to inform some sense of meaning or purpose. And what has become so clear to me over many, many decades, but I felt like I sharpened it in articulating it in, in a written form in the book, is that, well, it's an idea that's old. I'm not claiming any kind of novelty in the idea that I'm about to mention, but I certainly felt like I got to it through a novel trajectory, a cosmological trajectory, and it's simply the n- the idea that there is no fundamental notion of meaning in reality, in the world. There's no fundamental notion of purpose. There's no fundamental notion of value. All reality is, is collections of particles governed by quantum mechanical laws that evolve from one configuration in the early universe to a different configuration in the late universe, and in between, there's a moment when those particles come together and they look like human beings on one particular remote planet in a nondescript galaxy. And when you think about things in those terms, it can take you to that dark place or it can take you to a place of great appreciation and a place of gratitude, because when you realize how unlikely it is that collections of particles would come together to yield a living system called a human being and how spectacular it is that this collection of particles called a human being can invent, manufacture notions of value and meaning and purpose, how spectacular is that, that particles can do that? And when you think about things in those terms, you recognize that there is a sense of gratitude that we should all have for the mere fact of existence. And to go beyond that, the spectacular fact that we can do things like create beauty and understand the universe and illuminate mystery and experience wonder, and the fact that particles can do all that, I feel strongly, if you take it in fully, can fill me and certainly I think can fill others with that sense of thankfulness for existence, however fleeting that existence may be. And if you can get to that point, I feel that it can really change your perspective on the world. And I've seen this with students. I teach my book to students. In fact, I was teaching it before it was a book, and the book emerged, you know, from, you know, all that kind of thought and experience. And I have students, you know, in the classroom who come to me and said that this has been a very different experience from, say, organic chemistry or even from, you know, English literature or from psychology, because this can be a life-changing perspective. And I've seen it happen and, and it's the most gratifying moment to me when I see students come to that realization.

   4. CWChris Williamson54:55

      It's so counter, isn't it, to the way that we, as humans, first phenomenologically as an individual, experience our day-to-day, moment-to-moment existence of the world. It feels like it's bestowed with specialness. Like, there's-

   5. BGBrian Greene55:14

      Yeah.

   6. CWChris Williamson55:14

      ... curses and blessings that come from on high, and we have these, th- all manner of different things going. It feels like more than just matter interacting with matter. And then-

   7. BGBrian Greene55:24

      Yeah.

   8. CWChris Williamson55:24

      ... when you layer on top of that the fact that we have cultural artifacts that are coming in, you have these stories that you've been told we're dispensing with, or some of us are dispensing with religion now and the, the stories that that had attached to it. And there's people that are into astrology, and there's people that are into all manner of different, different ways to be in the world. And, um, it's interesting to think that by getting rid of all of the things that add narrative and personify our experience in that way, that put it into sort of human language, that actually there's potentially even more beauty to say that I am just matter interacting with matter, and that's even more special.

   9. BGBrian Greene56:13

      Yeah. I, I, I agree with that, and the only caveat that I would include in there is for those who feel that certain narratives are absolutely vital to their appreciation of their world and their life, for those who want to embrace the theological accounts, or those who, who find that that propels them to a better place, I'm all for that. I'm not of the new atheist community perspective that the goal is to wipe, say, one particular narrative, the religious narrative, off the face of the earth. I do see that narrative as a natural outcome of the cosmological progression, that through evolution and entropy gave rise to living systems that themselves reflected back on their existence and sought to place that within a larger story. We are storytellers. That's what we do. And among the largest of stories we tell are these religious narratives that imagine that the end is not the end, that imagine that there is a larger purpose that is coming to us from on high. I don't subscribe to that perspective, but I see the power and the value of that perspective. And so I like to think about reality as these layered narratives, to use the language that you were mentioning a moment ago, where you've got the reductionist story that the physicist comes along with, and the, the chemist comes along with trying to build larger structures, and the biologist puts those together into larger structures still. And then you come along to the psychologist, the neuroscientist, the philosopher, the artist, the theologian. These are all these layered accounts of reality, and I think we as individuals have the power to figure out which of those narratives are most compelling to us, which of those narratives give us a clearer sense of who we are and how we came to be, and use those narratives to invent our own sense of purpose and meaning. Because in the end, we are the authors of whatever purpose and value and meaning that we ascribe to. It comes ultimately from ourselves, and we have the power to pick and choose among those stories or to invent new ones in order to give us that sense of grounding.

9. 58:33 – 1:06:34

   How Fine-tuned is the Universe?

   1. BGBrian Greene58:33

   2. CWChris Williamson58:33

      I love that. I absolutely love that. Can you talk to just how finely tuned our universe is?

   3. BGBrian Greene58:41

      There's a way in which it's incredibly finely tuned, because what we have found in recent decades is that if you were to change any of the fundamental numbers of reality that we have measured, and these are really concrete numbers like the mass of the electron, the mass of the proton, the charge of the electron, the strength of gravity, those are all numerical values that we have measured. And it turns out that if you change them by even a small percent, some of these numbers, the universe as we know it simply goes away. Stars don't light up, for instance, if you start to play with the strength of the electromagnetic force and the nuclear forces. And without stars, right, the universe as we know it would be a completely different place. So, some have come to the conclusion that there must be some guiding force out there in the universe that carefully adjusted all of these numbers to have just the right value for stars to light up, planets to form, and on at least one such planet, life to exist. Others, however, have a, a different perspective. They say, "Look, you know, um, maybe there are many universes," as you and I were talking about earlier in this conversation, and maybe those other universes have different values for those numbers, and among the collection of all universes, effectively all values are represented, and only in some of those universes will stars and planets and people exist. And of course we live in one of those universes, because we're people. And therefore there's nothing fine-tuned at all when you look at the larger landscape of this multiverse, of this reality that has multiple universes. So, those are sort of two ends of the spectrum. Our universe is highly tuned, maybe some godlike being picked it to be the way it is, or every possibility's out there and we simply inhabit that part of the larger reality that allows us to exist.

   4. CWChris Williamson1:00:40

      Is that the observation selection effect?

   5. BGBrian Greene1:00:43

      In a sense, it is, because clearly we couldn't observe one of those other universes where the conditions were such that we couldn't exist. So, you could say of course we're going to observe a universe that has the particular numbers that we've seen because...... we couldn't exist in any other universe, and therefore, we couldn't be there to observe the different values. So yeah, it's definitely an extreme version of that idea.

   6. CWChris Williamson1:01:09

      Just how fine are we talking? Like, how much-

   7. BGBrian Greene1:01:12

      It d-

   8. CWChris Williamson1:01:12

      ... of a knife edge are the numbers on?

   9. BGBrian Greene1:01:15

      It depends which number, and it also depends on some assumptions. So, there are certain numbers, and I wish I could rattle off precisely which ones and what percent off the top of my head, but I'll probably get it wrong, so I won't do it. Uh, but there are numbers, like the strength of the electromagnetic force or nuclear force, where it's just a few percent or call it 10% difference would really, uh, render inoperable the processes that give rise to the things that we are familiar with. However, there have been papers recently that have shown, sure, if you just change one number, then yeah, you can mess things up and that may make it seem finely tuned. But if you allow all of the numbers to vary, they say, like, there are all these islands of possibilities that would yield systems that are not so different from the ones that we are familiar with. And so it can be misleading, they say, to just look at one dimension, one direction of change, because that makes it seem more special than it actually is. Um, so, so it's somewhat up in the air exactly how special it is, but the fact is, you know, if you were to randomly choose all those numbers, you know, if I had, like, 20 dials here that you could change those numbers at, at random, I believe that it's unlikely that you'd hit upon one just randomly that would be like the universe that we know.

   10. CWChris Williamson1:02:39

       It's crazy when you think ... I'm trying to drive home the meaning in a rationalist world's point basically, that the unlikeliness of our existence, cosmologically, individually, genetically, whatever it might be, is so, so vast. I did a, I did a TEDx Talk, um, at the start of last month and looked at some research that worked out to the likelihood of your specific combination of genetics existing, and it works out that the number's one in 10 to the power of 2,685,000-

   11. BGBrian Greene1:03:14

       Sure.

   12. CWChris Williamson1:03:14

       ... um, which is obscenely large. It's a ridiculously large number. Um, and then when you think, okay, and that's within a universe where the cosmological constant is this, and the gravity force, and blah, blah, blah, and you just realize that there is an awful lot to kind of be thankful for. And I understand why it gives people, I think awe and dread are kind of, th- th- they kind of sort of dance in tandem a little bit with this, that I, I can't believe how rare it is, and oh my God, I can't believe how rare it is at the same time. (laughs) And it kind of, it terrifies you at the same, at the same moment.

   13. BGBrian Greene1:03:53

       No, no, totally. In fact, there's another way of, of framing the, the unlikeliness. I mean, one way is, as you say, just look at the sequence of letters in your DNA and figure out how many possible sequences of letters of DNA, and you've got three billion base pairs, each of which, you know, could be one of four letters or a lot of combinations. Um, but another way of looking at it is, we are the end product of a series of quantum processes that stretch all the way back to the Big Bang. So, that's all that reality is, it's a series of quantum processes. And in quantum mechanics, there are many possible outcomes in any given quantum process. So, each and every event that has happened from the Big Bang until today is an event that could have turned out differently, and those different outcomes of those quantum events would yield a different reality when you look at the long sequence of events that stretch back to the Big Bang and reach until today. And so right there, (laughs) you've got just a gargantuan number of possible trajectories that the universe could have followed that would not result in, say, you and I having this conversation right now. You and I not even being here. So, so there is a great deal to be thankful for when you frame it in the DNA approach or the quantum processes approach. It, it, it, it just so, it's so unlikely that we would be here, and it'd be so unlikely that we would be able to even think about the sequence of events that result in us being here, right? I mean, if a, if an asteroid hadn't slammed into the Earth 65 million years ago, it could still be that the dinosaurs would be the dominant species walking around. And who knows? Maybe the dinosaurs would have evolved to a place of self-reflection.

   14. CWChris Williamson1:05:47

       (laughs)

   15. BGBrian Greene1:05:48

       I think it's unlikely, right? You know? Um, and, and so, and so right there, again, you see how that chance event, astrophysical event was vital to changing the course of how life evolved on our planet, allowing mammals to take over and allowing, through other chance events, our species to, to prevail and to take the form that it currently does. So, all of it suggests that it is so unlikely that we would be here having this conversation. It would be so unlikely that there'd be libraries full of reflections on what life is and how life came to be, that yeah, if you, if you take that all in, you can do nothing else but stare in wonder at the fact that we're here at all.

10. 1:06:34 – 1:09:56

    What's the Potential for the Future?

    1. CWChris Williamson1:06:34

       Beautiful. Given the fact that it's so rare, given the fact that our appearance on this planet and there being a planet is so unlikely, what are your thoughts with regards to us moving forward? Like, how likely is it, do you think, that we make it to space-faring civilization level? Given that it's so rare, that feels almost like an imperative for us. Until we answer the Fermi paradox, we potentially are the only corner of the universe which is lit up with its own self-awareness, which means that we have a duty. And I know Nick Bostrom talks about, um-... is it the, the waste of our, uh, galactic potential basically every moment that we're not spending colonizing the galaxy is a, is a waste as far as he's concerned. Do you think about that? Do you think about our potentials for future?

    2. BGBrian Greene1:07:23

       I, I, I do, and I've read some of, of Nick's writing on this. I, I do see it a little bit differently. Um, I don't see a temporal pressure. Like I don't feel like, "We gotta get out there. We gotta start spreading, you know, life." I, I don't sort of feel it that way, but I do feel the weight of responsibility, which is at the root of, of what Nick is talking about and what I'm talking about, you're talking about. There is a sense of, "Let's not squander what the universe has been able to do at least once and maybe only once," which is to have living systems that can re- reflect back on the universe, understand the universe, and take that understanding and begin to manipulate the universe, to control aspects of the universe. Let's not squander that in the way that we clearly have and are, right? I mean, I wouldn't say it's a waste of every moment that we don't start our journey to the stars, but I would say it's a waste of every joule, that's J-O-U-L-E, every unit of energy that we expend on building weapons, that we expend on war, that we expend on killing each other. That's the astounding waste. That's the profound waste. And, and I think it's our responsibility as, as thinking individuals who think this way to try to spread the word to the rest of our brethren, our brothers and sisters, that we have this incredible opportunity that emerged from this incredible sequence of events to, to reach out to the wider universe, and to understand more fully, and to, to seek other life and see what's out there. I think if people could just be inculcated with the thrill of that possibility and the weight of that responsibility, then I think things in principle could change. But of course, we're like infinitely far away from that on planet Earth at the moment. And so, you know, some of us, you know, the conversations that you're having, books that I and others are writing, I mean, it's all geared toward trying to spread the wonder of these ideas. And so we just keep going, and hopefully w- we'll be successful.

11. 1:09:56 – 1:16:30

    Do Our Emotions Hinder Us?

    1. BGBrian Greene1:09:56

    2. CWChris Williamson1:09:56

       It's only in the ignorance of the unlikeliness of our existence and the potential existential threats that we have that can stop our continuation, plus the hubris that allows us to believe that we can continue to just wrangle stuff around us, that I think anybody could consider it not our duty, our imperative, to be focused on this. Um, it's such a shame. I often think about this. I, I had this discussion with a existential risk guy. I don't think that you would be able to find a civilization out there in the universe that is much more emotional than we are. I think that if you turned our emotional, um, set point up to be more reactive by maybe 10 to 20%, I th- I don't think we'd get anything done, which is crazy, because that, that, that suggests that we're close to the upper bound of how emotional a m- slightly naught .7 on the, uh, Kardashev scale civilization could be. How insane is that to think?

    3. BGBrian Greene1:11:05

       It, it, it is an interesting way of framing it, and I'd say it becomes even more interesting when you look at the other end of the scale. I feel that if we were significantly less emotional, that we would be that much less successful as a species, because if you were a Spock-like species, say, from planet Vulcan, and your take on reality was all about logic and all about having a completely unemotional interpretation of the facts of the world and processing them through a rational, logical perspective, I don't think that that species, if that were us, I don't think we would've gotten to this place. I don't know that we would've been able to spread across the world. I don't know that we would've been able to invent the things that ultimately have transformed modern civilization in the ways that they have. I think it's the creative spirit, the, the ingenuity, the innovation that comes from not approaching the world in a completely rational way that has allowed us to come upon unexpected discoveries and unexpected developments. I mean, even just take Albert Einstein as a case in point, right? If, if Einstein was just taking a purely logical, rational approach to things, I don't know that he would've had the leap of imagination that gave rise to the special theory of relativity and the general theory of relativity and the, and the photoelectric effect, his 1905 paper. I mean, he was a bundle of emotion that had access to this powerful, rational intelligence, and it's the union of the two that I think has been the source of our, of our success. You're right. Too much emotionality, whatever, we'd be at each other's throats even more than we are right now, and we wouldn't have been able to make any progress. Much less than that...... I don't think that we would have gotten to the place that we, we currently have. So, so if you're right and emotional beings are kind of rare in the cosmos, maybe it'll be either a kind of boring galactic exploration, where we're like, "Oh, yeah, it's another rational civilization on this planet M," you know? (laughs)

    4. CWChris Williamson1:13:32

       (laughs) Yeah, it's another spot.

    5. BGBrian Greene1:13:33

       "What are we doing out here?"

    6. CWChris Williamson1:13:34

       Yeah.

    7. BGBrian Greene1:13:35

       "This is, like, awful." Or, or they just will never develop to the point where we'll even be able to have that kind of communication.

    8. CWChris Williamson1:13:44

       Something tells me that our capacity for emotion is directly proportional to the amount of enjoyment and utility that we get from the thought of exploration and from exploration itself. That the goal is not simply-

    9. BGBrian Greene1:13:57

       Yeah.

    10. CWChris Williamson1:13:57

        ... to exist. When Nick talks about the trillions and trillions of potential future human lives, he's talking about the utility that they could get, the, the flourishing, the eudaimonia, the happiness that they could-

    11. BGBrian Greene1:14:09

        Yeah.

    12. CWChris Williamson1:14:09

        ... experience if we go on for X number of million, tr- trillion years. So it's not about just existing. It's not about just exploring. It's about using the, our capacity to experience exploration, to enjoy it. And, um, yeah, that's, that's interesting that it's both the poison and the tonic.

    13. BGBrian Greene1:14:31

        Yeah. And, and again, I can give you a concrete example with, with, with Einstein again. So in November of 1915, as Einstein's heading toward the general theory of relativity, right? That's the final month of, of research and work. He, he's going at it day and night, day and night, because there's a competitor named David Hilbert who he learns is hot on his tail. Now, a completely rational, logical being would be like, "Well, it doesn't matter who discovers this. It's just, we want to get to a deeper understanding," and wouldn't have worked anywhere near as hard as Einstein did, and maybe wouldn't have had the logical leaps that he had in that, in that final month. And at the end of that journey, he said something like, you know, "The last few weeks of, um, exploration toward general relativity," he says, "have left me exhausted." But he then said, "The success is sublime." And it's that feeling of the sublime which I think has driven so much of human achievement. And I would say, to, to, to underscore what you just mentioned, and also perhaps to re-shade the conversation that we were had about Nick and people needing to space fare across the cosmos, I don't think that every human being needs to be concerned with extraterrestrial life. I don't think that every human being needs to be excited about a journey to the stars. You know, if you have a, a Johannes Brahms who's composing, you know, a spectacular symphony, let Brahms compose Brahms' Fourth Symphony. Brahms doesn't need to be thinking about extraterrestrial intelligence. So, so that, that emotional, that sublime quality of creation and creativity, I think that's what you want humankind to respect and to revere and to participate in, but it doesn't have to be all focused in one direction.

    14. CWChris Williamson1:16:27

        Yeah. Aga- I, I, again, I absolutely love that.

12. 1:16:30 – 1:21:05

    The Boötes Void

    1. CWChris Williamson1:16:30

       One thing that I was researching recently, the Boötes void. Have you had a look at this?

    2. BGBrian Greene1:16:36

       I don't know what that is. What is that?

    3. CWChris Williamson1:16:37

       S- so it's a supervoid. It's the largest supervoid that's been found.

    4. BGBrian Greene1:16:41

       Oh, okay. In space? Yeah, yeah.

    5. CWChris Williamson1:16:41

       Yeah, yeah, yeah. Um, have you had a look at much of these supervoids? I mean-

    6. BGBrian Greene1:16:44

       I've not. I, I, I've not followed that at all. I mean, certainly our, uh, our understanding of cosmology is predicated on the assumption that on the largest of scales, the universe is homogeneous and isotropic. And the voids have provided an interesting way of wondering whether that's true, because the assumption is, on large enough scales, the voids would average out together with the arena that are not void, that are full of stuff, that, on average, it'll all be the same. Is that wrong? If that's wrong, then it causes us to go back and rethink some of our cosmological ideas.

    7. CWChris Williamson1:17:24

       There's some awesome YouTube videos about it, absolutely fascinating. I suppose the-

    8. BGBrian Greene1:17:28

       Oh yeah, I'll have to check in, yep.

    9. CWChris Williamson1:17:29

       The crazy thing is, it's, it's massive. It's a s- it's the biggest supervoid that's been found. The, the gaps are absolutely huge. But I suppose if that's just the head of a pin, if our observable universe is the head of a pin, then perhaps that fluctuation is so low that actually it doesn't matter, and perhaps it still is compatible. And talking about from, from the biggest to the smallest, why do you think the Planck scale exists?

    10. BGBrian Greene1:17:57

        Well, um, it's an interesting mathematical fact that if you just take certain constants of nature that we've measured, Newton's universal gravitational constant, usually called G, H-bar, Planck's constant, that speaks to the quantum effects, and C, the speed of light. If you take these constants and you combine them in just the right way, you can make the units come out to a length, and the particular length we call the Planck length, and it's a particular number, 10 to the minus 33 centimeters. And so, so from a, from a purely methodological perspective, we understand why there seems to be a fundamental length built into the laws of physics. You need units, and those units are such that they can conspire to yield this fundamental length scale. From a more philosophical perspective, we suspect it's because the laws of physics, as we understand them, only work down to a particular length scale. As we probe the universe on ever-shorter scales, we've encountered newer and unexpected phenomenon, but it's possible that the very notion of a smaller length doesn't always make any sense. There may come a length where the notion of a smaller length is a concept that doesn't mean anything any longer.And if that idea, if that chain of reasoning is true, then that is another rationale for the Planck length. The Planck length would be that length below which the notion of "below which" doesn't mean anything. And, and so if there is such a length, the Planck length would be it.

    11. CWChris Williamson1:19:37

        It's so cool. I saw a, um, a theory online, where someone said that the reason the Planck length exists is because we're in a simulation and that's the size of the pixels-

    12. BGBrian Greene1:19:48

        (laughs)

    13. CWChris Williamson1:19:48

        ... essentially. That that's the smallest amount of bit information that could be transmitted, so that's, that's why it's there. I thought that was quite a cute, a cute way to put it.

    14. BGBrian Greene1:19:57

        Yeah, but, but whenever I hear things like that, my rejoinder to that is, but if you had a really clever programmer, the programmer could make the sentient beings in that simulation think that there wasn't a Planck length, because the programmer is in control of the reality and therefore can make the simulants, you and I, think whatever the programmer wants us to think. So I'm less convinced that real constraints from the physical universe necessarily have a home in a simulated universe.

    15. CWChris Williamson1:20:30

        Or maybe he's put it in as a red herring, so that you think, "That Brian Greene guy thinks that he knows what's going on."

    16. BGBrian Greene1:20:36

        Yeah, so that's the other, the other, the, the, the flip side, is that the simulator can, again, conjure things that have no basis in reality. Um, so yeah, the interplay between physical reality and the reality that the simulator creates, that's a, that's a subtle one, and I suspect it's in the hands of the simulator, in the hands of the creator. And therefore crossing over between the two always feels, to me, suspect.

13. 1:21:05 – 1:23:35

    The Copenhagen Interpretation

    1. BGBrian Greene1:21:06

    2. CWChris Williamson1:21:06

       Can you just explain for me the Copenhagen interpretation? I really want to try and cut through ... Th- this seems to be, like, the woo-woo element of physics that gets thrown around and is excuse for all manner of bad thinking. Can you just try and break down-

    3. BGBrian Greene1:21:23

       Yeah.

    4. CWChris Williamson1:21:23

       ... what it is and what it isn't?

    5. BGBrian Greene1:21:25

       Well, different people will answer this question differently in the community today, so it's not a fully well-defined notion, the Copenhagen interpretation. But my view, and it's shared by many other physicists as well, is that, look, Niels Bohr, who was one of the founding pioneers of quantum physics, who was working in Copenhagen, had a particular attitude about quantum mechanics. And any interpretation of quantitative mechanics that captures that attitude is what we call the Copenhagen approach. And his attitude was, "Quantum mechanics is not about describing the universe as it is." This is almost a quote of his. "Quantum mechanics is about describing the universe as it is." It's all about just making predictions for what we'll see on devices, on counters, on, on measurers, on, on instruments. So Bohr was basically, "Don't think about the meaning of quantum mechanics, don't think about the deep nature of reality. Just think about quantum mechanics as a tool. And as a tool, you should just use it to make predictions about the world." And, and so he viewed quantum mechanics as a mathematical algorithm. "Follow these steps and we can teach these steps to any undergraduate, even high school kids. We can teach them, follow these steps and it will yield a number. And then compare that number with w- the number you get on a dial." And that, to me, is the most concrete form of the Copenhagen interpretation. Now, others will say things like, "No, the Copenhagen interpretation is about, you know, you look at an experiment and that causes the quantum mechanical wave function to collapse onto this result or that result, and therefore it's all about an, uh, interrelationship between an observer and the observed." Eh, yeah, I get it. Some people will say that, but I don't think Bohr ever really felt that he'd gotten to grips with that relationship, and so I think the, the most, um, accurate description of the Copenhagen approach, Bohr's approach, is just use quantum mechanics as an algorithm. Don't worry about what it means.

14. 1:23:35 – 1:24:30

    Where to Find Brian

    1. CWChris Williamson1:23:35

       Perfect. I think we fixed a lot of bad thinking with that. Brian, today's been fantastic. I really appreciate having you on. We will be linking the brand new paperback version of Until the End of Time in the show notes below. Anything else? Where should people go if they want to keep up to date with what you're doing?

    2. BGBrian Greene1:23:51

       Oh, well, we're doing a lot of stuff with my, uh, organization called the World Science Festival, creating all sorts of programming. So yeah, if people check out worldsciencefestival.com, sign up, it's all free. Some really cool science programming coming down the pike.

    3. CWChris Williamson1:24:05

       Perfect. Thank you very much.

    4. BGBrian Greene1:24:08

       My pleasure. Thank you. Enjoyed the conversation.

    5. CWChris Williamson1:24:11

       Thank you very much for tuning in. If you enjoyed that, then press here for a selection of the best clips from the podcast over the last few months. And don't forget to subscribe. It makes me very happy indeed. Peace.

Episode duration: 1:24:30