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OUTLINE:
0:00 - Introduction
0:27 - Entropy
8:35 - Consciousness
24:54 - Quantum gravity
28:14 - String theory
41:41 - Time
54:13 - Free will
58:36 - Emergence and complexity
1:05:48 - The Big Bang
1:18:47 - Extraterrestrial life
1:29:09 - Space exploration
1:37:07 - Fear of death

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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.

To support it, please check out our sponsors in the description.

And now, here's my conversation with Brian Green.

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, "'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 1 that does not appeal to me.

I see no reason therefore to believe in any sort of God.

As you say, this is a bleak outlook on our universe and the emergence of human consciousness.

So let me ask, what is the more hopeful perspective to take on this story?

Well, I think the more hopeful perspective is to more fully understand 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 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.

Second law of thermodynamics establishes that disorder, entropy, in aggregate, is always on the rise.

And that is indeed Interpretable as disintegration destruction over sufficiently long timescales 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 a sense 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?

So maybe we'll skip around a bit, but let me ask the biggest possible question.

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 heat death that is once again returns to simple things as the march of the second law of thermodynamics goes on?

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, many people put forward different ways of taking this question on.

And there is no 1 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 physics and science more generally over the past few hundred years.

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 special in terms of complexity.

And maybe you can even begin to measure it and like come up with metrics where whatever we got going on on earth, These like 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 observable part that we can see with our tools.

I mean, so I have to ask, as you describe in your book once again, 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?

I asked that question even to Richard Dawkins once, and I already have my preconceived notion, which he pretty much confirmed, which is if 1 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.

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 the 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.

And 1 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.

Which part of the story of life, let's stick to earth for a second, do you think is the hardest?

If you were like a betting man, which part is the hardest to make happen?

Again, we haven't drawn the line of where, as you say, the line between a rock and a rabbit.

That part, is it complex organisms like multicellular organisms?

Is it crawling out of the ocean where the fish somehow figured out how to crawl around?

Is it then the us homo sapiens, as we like to think of ourselves special and intelligent?

Or is it somewhere in between as you also talk about, again, very hard to know at which point this consciousness emerge?

Like if you were to sort of took a survey and made bets about other Earth-like planets in the universe.

Where do you think they get stuck the most?

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 to acquire consciousness, I think that's probably the hardest part because look, take Earth and recognize that it weren't for 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 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.

I really appreciate that you lean into some of these unanswerable questions with me today.

But so you think about consciousness not as like a phase shift, the binary 0 1.

You think of it as a continuum that humans somehow are maybe some of the most conscious beings on earth.

Rocks probably will stay quiet on the matter.

For the moment, they're waiting for their opportunity.

But I agree that, look, even when you and I look at each other, I am not fully convinced that you're a conscious being, right?

I mean, your behavior is such that 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 that we can make, yeah, there is something special about us.

I don't think that there are fish walking around and coming up with existentialism.

I don't know that there are 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.

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

I think consciousness, and I think that there's 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 actually coined a name for this, the hard problem of consciousness, you know, David Chalmers and others.

As a physicist, I look at the world and I see it's particles governed by physical law.

You know, we got electrons, we 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 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.

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 answering that question, I think is among the deepest and most difficult questions that we face.

Do you think it is in fact a really hard problem or is it possible, I think you mentioned in your book that it's just like almost like a side effect, it's an emergent thing that's like, oh, it's nice.

Yeah, well, I mean, when people use the phrase hard problem, I mean, they mean in a somewhat technical sense that it's trying to explain something that seems fundamentally unavailable to third party objective analysis, right?

I'm the only 1 that can get inside my head and I can tell you a lot about what's happening inside my head right now is reflected in what I'm saying 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 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 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 timescale 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, it's just a thing that happens when particles come together.

And however mysterious that feels right now, I think, for instance, when we start to build conscious systems, you know, things that 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.

Yeah, there's a world going on inside here.

I think the mystery of consciousness will just begin to evaporate.

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 built quite a few robots and have had them do emotional type things, and it's immediate that exactly what you're saying, this kind of mystery of consciousness starts to evaporate.

That the kind of need to truly understand, to solve the hard problem of consciousness, like disappears because, well, I don't really care if I understand what can solve the hard problem of consciousness.

You know, I feel like that way when I interact with a dog.

I don't need to solve the problem of consciousness to be able to interact and richly enjoy the experience with this other living being obviously same thing with other humans.

And there's some aspect, Maybe this is a little bit too engineering focused, but there's some aspect in which it feels that consciousness is just a nice trick to help us communicate with each other.

It sounds ridiculous to say, but sort of the ability to experience the world is very useful in a subjective sense, is very useful to put yourself in that world and to be able to describe the experience to others.

It could be just a social and the emerge, obviously animals, the sort of more primitive animals might experience consciousness in some more primitive way, but this kind of rich subjective experience that we think about as humans, I think it's probably deeply coupled like language and poetry.

Yeah, that resonates with my view as well.

I mean, there's a scientist, maybe you've spoken to him, Michael Graziano from Princeton.

Yeah, he's developed ideas of consciousness that, look, I don't think they solve the problem, but I think they do illuminate it in an interesting way where basically we are not aware of all the underlying physiochemical processes that make our brains and our inner worlds tick the way they do.

And because of that dissociation between sensation and the physics of it and the chemistry of it and the biology of it, it feels like our minds and our inner worlds are just untethered, like floating somewhere in this gray matter inside of our heads.

And the way I like to think of it is like, look, if you're in a dark room, right, and I had glow-in-the-dark paint on my fingers, So all you saw was my fingers dancing around.

And then you turn on the light, you realize, oh, there's this arm underlying it.

And that's the deep physical connection explains it all.

And I think that's what we're missing, the deep physical connection between what's happening up here and what is responsible for it in a physical, chemical, biological way.

And so to me, that at least gives me some understanding of why consciousness feels so mysterious, because we are suppressing all of the underlying science that ultimately is responsible for it.

And 1 day we will reveal that more fully and I think that will help us tether this experience to something quite tangible in the world.

I wonder if the mystery is an important component of enjoying something.

So once we know how this thing works, maybe we will no longer enjoy this conversation.

We'll seek other sources of enjoyment, but this is again from an engineering perspective.

I wonder if the mystery is an important component.

Have you ever seen, there's this beautiful interview that Richard Feynman did, a great Nobel laureate physicist responsible for a lot of our understanding of quantum mechanics, quantum field theory and so forth, and he was in a conversation with an interviewer where he noted that some people feel like once the mystery is gone, once science explains something, the beauty goes away, the wonder of it goes away.

And he was emphasizing in his response to that, he's like, no, that's not the right way of thinking about it.

He says, look, when I look at a rose, he says, yeah, I can still deeply enjoy the aroma, the color, the texture.

He says, but what I can do that you can't, if you're not a physicist, I can look more deeply and understand where the red comes from, where the aroma comes from, where the structure comes from.

It doesn't flatten it or take away from it.

well I sort of take that as a bit of a motto in some sense, that there is a wonder that comes from a kind of ignorance.

And I don't mean that in a derogatory sense, but just from not knowing.

So there is a wonder that comes from mystery.

There's another kind of wonder that comes from knowing and deep knowing.

And I think that kind of wonder has its own special character that in some ways can be more gratifying.

But there's also, I remember he said something about like science is an onion or something like that.

You can peel back, you can Keep peeling back.

I mean, there is also, when you understand something, there's always a sense that there's more mystery to understand.

Like you never get to the bottom of the mystery.

But I think it's also different than, you know, I don't think you can analogize, say, to a magician.

A magician does some trick, you learn how it's done, it's like, oh my God, that's ridiculous when

But nature is perhaps the best magician if you want to try to make the analogy there because when you peel things back and you understand how it is that things have color and you have electrons dancing from 1 orbital to another, emitting photons at very particular wavelengths that are described by these beautiful equations of quantum electrodynamics, part of which that Feynman developed, it gives you a greater sense of awe when the curtain is pulled back than what happens in other circumstances where it does flatten it completely.

Yeah, it's very possible then, say in physics, that we arrive at a theory of everything that unifies the laws of physics and has a very strong understanding of the fabric of reality.

Even like from the Big Bang to today, it's possible that that understanding is only going to elevate our appreciation of this whole thing.

But the other side of it, which you emphasize, is it's not like science somehow reaches an end, right?

There are certain categories of questions that do reach an end.

I think we 1 day will close the book on nature's ingredients and the fundamental laws.

Now that, we can't prove that, maybe it goes on forever, smaller and smaller, maybe there are deeper and deeper laws.

I think that there's going to be a collection of ingredients and a collection of basic laws.

Now we take that knowledge and we try to understand how the world builds the structures that it does, you know, from planets to people to black holes to the possibility of other universes and every step of the way the collection of questions that we don't know the answer to only blossoms.

And so there's a deep sense of gratification from understanding certain qualities of the world, but I would say that if you take a ratio of what we understand to the things that we know that we don't yet understand, that ratio keeps getting smaller and smaller because the things that we know that we don't yet understand, that ratio keeps getting smaller and smaller because the things that we know that we don't understand grows larger and larger.

Do you have a hope that we solve that theory of everything puzzle in the next few decades?

So there's been a bunch of attempts from string theory to all kinds of attempts at trying to solve quantum gravity or basically come up with a theory for quantum gravity.

1 for experimental validation, you have to observe effects that are very difficult to 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 laws of gravity to quantum mechanics.

I mean, it's in some sense, but 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 phrase because it does make other scientists feel like if they're not working on this, what are they working on?

Man's like, you know, there's not much left when you're talking about theory of everything.

Yeah, so it is really trying to put gravity and quantum mechanics together.

And since I was a college kid, I was deeply fascinated with gravity.

And as I learned quantum mechanics, the notion of physicists being stumped and trying to blend them together.

How could 1 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.

You mentioned string theory as 1 possible scenario.

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 is, 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 headway, working 18 hours a day and this sort of stuff, I would have said, yeah, by 2021, yeah, we're going to know whether it's right or wrong, we'll make contact.

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.

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 level of detail that we actually, I would have said no, I don't think that we're gonna be able to do that.

Will we have an exact formulation of strength here in certain circumstances?

No, I don't think we're gonna have that, and yet we do.

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 would love before I leave this earth to know the answer.

But science and the universe, it's not about pleasing any individual.

And so we just press onward and we'll see where it goes.

So in terms of strength theory, if I just look from an outsider's perspective currently at the theoretical physics community, string theory as a theory has been very popular for a few decades, but 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?

Like, how do you make sense of this puzzle?

Why do you think it has fallen out of favor?

Yeah, so I would actually challenge the statement that's fallen out of favor.

I would say that any Field of research when it's new and it's the bright shiny Bicycle that no 1 has yet seen on that block.

Yeah, it's going to attract attention and the news outlets are gonna cover it and students are gonna flock to it, sure.

But 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, 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 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 very sober about the theory.

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.

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.

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 them were seasoned, even if they were pro-string theory at the time, I don't know if they were rolling their eyes, but they knew that it was gonna be a long, long journey.

I think people like John Schwartz, 1 of the founders of string theory, Michael Green, no relation to me, founders of the theory.

Edward Witten, you know, 1 of the main people driving the theory back then and today.

I think they knew that we were in for a long haul.

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 work on other subjects.

If you're in, in the way that Einstein was in, for a lifetime of investigation to try to see where, what the answers to the deep questions would be, then I think string theory has been a rich source of material that has kept so many people deeply engaged in moving the frontier forward.

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?

Well, what attracted me to the theory at the outset, beyond it's putting gravity and quantum mechanics together, which I think is its true claim to fame, at least on paper, it's able to do that.

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