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This is Alex Friedman podcast, and here is my conversation with Brian Green And 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 scientific evidence goes, the universe has crawled by slow stages to somewhat pitiful result on this earth and is going to crawl by still more pitiful stages to a condition of universal death.

7:16

If this is to be taken as evidence of purpose, I can only say that the purpose is one that does not appeal to me.

7:24

I see no reason therefore, to believe in any sort of God, that's quite a depressing statement.

7:32

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

7:37

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

7:44

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.

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And really that's in some sense what, what my book until the end of the time was all about.

8:02

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 going to wither decay fall apart.

8:18

Yeah, that's true.

8:20

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.

8:34

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.

8:53

That's just really something that inspires gratitude and wonder and, and a sense of, of deep purpose by virtue of being these unique collections of entities that happen to rise up, look around and try to figure out where we are and what the heck would you do with our time.

9:13

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.

9:30

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

9:34

Then you said purpose. So what's the meaning of it all then is a, 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

9:59

think there is, but I don't think it's a universal answer.

10:01

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.

10:16

I mean, many people put forward different ways of taking this question on and there is no one right answer when you recognize deeply that the universe doesn't care, there is nothing out there.

10:32

That is the final answer.

10:34

It's not as though we need a more powerful telescope and somehow we can look deeply into the universe, all will become clear.

10:42

In fact, the deeper we've looked built literally and metaphorically into the universe and into the structure of reality.

10:49

The more it's become clear that we are just a momentary by-product of laws of physics that don't have any emotional content, they don't have any intrinsic sense of meaning or purpose.

11:04

And when you recognize that you realize that searching for the universal for this kind of a question is a fool's errand.

11:12

Every individual has the capacity to make their own meaning to set their own purpose.

11:18

And that's not some platitude.

11:20

That is what we are because there is no fundamental answer.

11:25

It's what you make of it. And however much that may sound like a hallmark card.

11:29

This really is the deep lesson of, of physics and science more generally over the past few hundred years.

11:37

Well, there's some level where you can objectively say that whatever we got going on here is kind of peculiar.

11:42

It's kind of special in, in, in, in, in terms of complexity.

11:48

And maybe you can even begin to measure it and like come up with metrics where whatever we got going on earth, these like interesting hierarchical complexities, that form more and more sophisticated biological system.

12:04

That seems kind of unique.

12:06

When you look at the entirety universe open the, the observable part that we can see with our tools.

12:13

I mean, so I have to ask, as you describing your book, once again, short and go wrote the book, what is life based on the few lectures he gave in 1944?

12:23

So let me ask the fundamental question here.

12:27

What is life, this particular thing we got going on in here?

12:32

This pocket of complexity that emerged from such simple things.

12:35

Yeah, it's a tough, I

12:37

asked that question even to a Richard Dawkins once and I already had my preconceived notion, which he pretty much confirmed, which is if one could give an answer to that question that allowed you to sort of draw a line in the sand between the not living and the living, then perhaps we would have the insight that we yearn for and trying to say, what is so special about life.

13:01

But the fact of the matter is it's a continuum.

13:04

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.

13:14

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.

13:35

Somewhere in those collections of biological processes is the necessity or the necessary ingredients and processes for life.

13:46

But drawing that line in the sand is not something that we're able to do, but I would agree with you, it's deeply peculiar.

13:54

It may in fact be unique, but it may not.

14:00

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.

14:12

That's what the sun is together with a planet being bathed by that low entropy energy together with a surface that has enough of the raw constituents that we recognize are fairly commonplace result of supernova explosions, where star spews forth, the result of the nuclear furnace.

14:33

That is the core of a star. It could be that all you need are those fairly commonplace conditions and maybe life naturally forms.

14:42

Look, the James Webb space telescope, right?

14:45

It's going up hopefully in December.

14:46

And one of the, one of the goals of that mission is to look at atmospheres around distant planets and perhaps come to some sense of how special or not life or leave life.

14:58

As we know it is in the universe, Which

15:01

part of the story of life let's stick to earth for a second.

15:06

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

15:13

Is it the origin of life?

15:15

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?

15:27

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

15:34

Is it then the us homosapians as we like to think of ourselves special and intelligent, or is it somewhere in between as you also talk about again, do very hard to know at which point this consciousness emerge.

15:53

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

16:04

Well, I would certainly say, Gonna go all the way to conscious beings like ourselves.

16:07

I would put it at the onset of consciousness, which again, I think is a continuum.

16:12

I don't think it is something that you can draw the line in the sand, but there are obvious circumstances.

16:18

There are obvious creatures such as ourselves where we do recognize a certain kind of self reflective, conscious awareness.

16:26

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, you know, some singular event 65 million years ago, where this large rock slams into planet earth and wipes out the dinosaurs.

16:52

Maybe the dinosaurs would still rule the planet and they may well have not developed the kind of conscious awareness that we have.

17:03

So for billions of years on this planet, there was life that didn't have the kind of conscious awareness that we have.

17:12

And it was an accidental event in astrophysical history that allowed a mammalian species like us to ultimately be the end product.

17:23

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 practice.

17:40

We are a rare exception to that.

17:43

And I really appreciate You lean into some of these unanswerable questions for me today, but the, so you think about consciousness, not as like a face shift, a binary zero one, you think it was a continuum that human somehow are maybe some of the most conscious beings on earth.

18:02

So you're, So

18:04

I mean, people will dispute that.

18:06

Yes. Well, and it's a very hard argument.

18:09

People get that Rocks

18:10

probably will stay quiet on the Matter.

18:12

Maybe not right for the moment they're waiting for their opportunity.

18:16

But, but, but I, I, 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.

18:29

I mean, I think that you are onto me.

18:30

I mean, your behavior is such that that's the best explanation for what's going on.

18:35

But of course we're all in the position of only having direct awareness of our own conscious being.

18:41

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.

18:51

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.

19:00

Yeah. There is something special about us. I don't think that there are fish walking around and, you know, coming up with, you know, existentialism, I don't know that there are, you know, dogs walking around, who've developed an understanding of the general theory of relativity.

19:14

I mean, maybe we're wrong, but that seems the best explanation.

19:20

What do you think is more special intelligence or consciousness?

19:23

I think consciousness. And I think that there's a deep connection between these ideas.

19:29

There are distinct, but they're deeply connected.

19:30

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 out the world and I see it's particles governed by physical law.

19:47

We can name them.

19:50

You know, we've got electrons, we've got corks that come in various flavors and so forth.

19:55

We have a list of ingredients that science has revealed.

19:58

And we have a list of laws that seemingly govern those ingredients.

20:02

And, and nowhere in there is there even a hint that when you put those particles together in the right way, an inner world should turn on.

20:13

And it's not only that there's no hint, it's insane.

20:16

I mean, it's ridiculous.

20:18

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.

20:34

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

20:43

Do you think it is in fact a really hard problem?

20:48

Or is it possible?

20:50

I think you mentioned your book that is just like a, almost like a side effect.

20:55

It's an emergent thing. That's like, oh, that's nice.

20:58

It's like a nice little feature.

21:00

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

21:18

I'm the only one that can get inside my head.

21:20

And I can tell you a lot about what's happening inside my head right now.

21:24

It's reflected in what I'm saying. And you can try to deduce things about what's going on at the top of my head, but you don't have access to it.

21:30

And 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 and science, where we look at the motion of the moon, everybody can look, everybody can measure it.

21:43

We look at the properties of hydrogen when you shine, lasers on, everybody can look at the data and understand it.

21:51

And so it seems like a fundamentally different problem.

21:54

And in that sense, it seems like it is hard relative to the others.

21:58

But I do think ultimately that the explanation will be as you recount, I think that a hundred years from now, or maybe it's a thousand, 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 before who thought consciousness was so incredibly mysterious when the reality of it is, eh, it's just a thing that happens when particles come together and, and however mysterious that feels right now.

22:35

I think for instance, when we start to build conscious systems, you know, things that, you know, you're more familiar with than I am when we start to build these artificial systems and those systems report to us, I'm feeling sad.

22:48

I'm feeling anxious.

22:50

Yeah. There's a world going on inside here.

22:51

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

22:57

Well, first of all, beautifully put, and I agree with you completely, just the way you said it, it will begin to evaporate.

23:02

I have built quite a few robots and have had them do emotion, emotional type things.

23:12

And it's immediate that exactly what you're saying.

23:14

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 or can solve the hard problem of consciousness, that thing sure.

23:33

As heck looks conscious. You know, I feel like that way, when I interact with a dog, I don't need to solve the problem of cautiousness to, to be able to interact.

23:43

And originally in enjoy the experience with this other living, being obviously the same thing with other humans.

23:51

I don't need to fully understand it.

23:53

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

24:06

It sounds ridiculous to say, but sort of the ability to experience the world is very useful in a subjective sense is very useful.

24:19

So put yourself in that world and to be able to describe the experience to others, it could be just the social and the merge, obviously, animals that sort of more primitive animals might experience cautiousness in some more primitive way, but this kind of rich subjective experience that we think about as humans I think is probably deeply coupled like language and poetry With

24:44

my view as well. I mean, there's a scientist.

24:47

Maybe you've spoken to him, Michael Graziano from Princeton.

24:51

Yeah. He he's developed ideas of consciousness that look, I don't think they solve the problem, but I think they do.

24:58

Aluminate it in an interesting way where basically we are not aware of all the underlying physio chemical processes that make our brains and our inner worlds tick the way they do.

25:13

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.

25:31

And the way I like to think of it is like, look, you know, if, if, if, if you're in a dark room, right?

25:39

And, and I had glow in the dark paint on my fingers, so all you saw was my fingers dancing around.

25:45

There'd be something mysterious.

25:47

How, how could those fingers be doing that?

25:50

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

25:53

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

25:55

And I think that's what we're missing.

25:57

The deep physical connection between what's happening up here and what is responsible for it in a physical, chemical, biological way.

26:06

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.

26:19

And one day we will reveal that more fully.

26:21

And I think that will help us tether this experience to something quite tangible in the world.

26:26

I wonder If

26:29

the mystery is an important component of enjoying something.

26:34

So once, once we know how this thing works, maybe we we'll no longer enjoy, like this conversation will seek other sources of enjoyment, but there's a, this is again from an engineering perspective.

26:50

I wonder if the mystery is, is an important component, You

26:55

know, there's, have you ever seen there's this beautiful interview that Richard Fineman did, you know, great Nobel Laureate physicist responsible for a lot of our understanding of quantum mechanics, quantum field theory, and so forth.

27:08

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, it deputy goes away, know the wonder if it goes away.

27:24

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

27:30

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.

27:48

He says that only augments my wonder, it only augments my experience.

27:55

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

27:58

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

28:09

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

28:12

So there is a wonder that comes from mystery.

28:14

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

28:20

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

28:30

I hope he's right. I hope you're right.

28:32

And, but there's also, I remember he said something about like an like sizes, an onion or something like that.

28:39

You can peel back, you can keep it, keep peeling back.

28:42

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, But

28:52

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

28:59

And it does some trick.

29:00

You learn how it sounds like, oh my God, that was, that's ridiculous when you find, but, but nature is perhaps the best magician.

29:08

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 one orbital to another emitting photons at very particular wavelengths that are described by these beautiful equations of quantum electrodynamics part of which that Fineman developed, it gives you a greater sense of awe when the curtain is pulled back, then what happens in other circumstances where it does flatten it completely.

29:41

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

29:51

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

30:04

I think it will. I may think it has. It has so far, the other side of it, which you, which you emphasize is it's not like science somehow reaches an end, right?

30:14

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

30:18

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

30:23

Now that can't prove that maybe it goes on forever, smaller and smaller, maybe they're deeper and deeper laws, but I don't think so.

30:30

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

30:34

That chapter will close, but it's one chapter.

30:38

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.

30:57

And so there's a, there's a deep sense of gratification from understanding certain qualities of the world.

31:04

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 understand grows larger and larger, Do

31:20

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

31:25

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

31:35

There's a lot of complexities to this one for experimental validation.

31:40

You have to observe effects that are very difficult to measure.

31:45

So you have to build, that's like an engineering challenge.

31:48

And then there's the theory challenge, which is like, it seems very difficult to connect to the laws of gravity to quantum mechanics.

31:56

Do you have a hope or are we Hopelessly

32:00

stuck? Well, I have to have to have a hope.

32:03

I mean, it's in some sense, but a devoted, at least part of my professional life toward trying to make progress on, I'm glad you use the phrase quantum gravity.

32:12

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?

32:21

It's like, you know, there's not much left when you're talking about a theory of everything Is

32:25

just small details.

32:27

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

32:31

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

32:37

And as I learned quantum mechanics, the, the notion of physicists being stumped and trying to blend them together, how could one not get fired up about maybe contributing something to that journey?

32:50

And so we've been on this, you know, I've been on this for 30 years since I was a student.

32:55

We, we have made progress.

32:56

We do have ideas.

32:58

You mentioned string theory is one possible scenario.

33:01

It's not stuck.

33:02

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.

33:19

So I would have hoped that by now we would've made contact with observation.

33:23

If you would have interviewed me back in the eighties, when I was, you know, wild, bright eyed kids trying to make headway working 18 hours a day on this sort of stuff I would've said.

33:34

Yeah, by, by 2021.

33:36

Yeah. We're going to know whether it's right or wrong, but make contact.

33:38

I would have said, look, there may be certain mathematical puzzles that we've yet to work out, but we'll know enough to make contact with experiment that has not happened.

33:46

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

34:05

Will we have a, an exact formulation of string theory in certain circumstances?

34:09

No, I don't think we're going to have that.

34:11

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.

34:18

Hope that maybe before I move on to wherever, I don't think there is an after, but I, I would love before I leave this earth to, to know the answer, but you know, science and the universe, it's not about pleasing any individual.

34:35

It is what it is.

34:37

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

34:40

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

35:06

Like, how do you make sense of this puzzle?

35:08

Why do you think has fallen out of favor?

35:11

Yeah. So I don't, I would actually challenge the statement.

35:13

That's fallen out of favor.

35:14

I would say that any field of research when it's new and it's the bright, shiny bicycle that no one has yet seen on that block.

35:26

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

35:34

Sure. But as a, as a field matures, it does shed those qualities because it's no longer as novel as it was when it was first introduced 30, 40 years ago.

35:45

But you need to judge it by a different standard.

35:48

You need to judge it by, is it making progress on foundational issues, deepening our understanding of the subject.

35:55

And by that measure, string theory is, is, is scoring very high.

36:01

Now at the same time, you also need to judge whether it makes contact with experiment as we discussed before, too.

36:08

And in that measure, we're still challenged.

36:10

So I would say that many strength areas, myself included are, are very sober about the theory.

36:20

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.

36:32

And that was something that we weren't particularly good at back say in the eighties, look, when I was just starting out in the field, there was a sense of physics is about to end.

36:43

Strength is about to be the Beal and all final unified theory.

36:49

And that will bring this chapter to a close.

36:52

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.

37:00

I don't know if they were rolling their eyes, but they knew that was going to be a long, long journey.

37:07

I think people like John Schwartz, one of the founders of string theory, Michael Green, no relation to me, founders of the theory, Edward Witten, you know, one of the main people drive in the theory back then, and today I think they knew that we were in for a long haul.

37:23

And, and that's the nature of science quick hits that resolve everything few and far between.

37:30

And so if you were in for the quick solution to the big questions of the world, then you would have been disappointed.

37:40

And I think there were people who were disappointed and moved on and work on other subjects.

37:44

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.

37:55

Then I think string theory has been a rich source of, of material that has kept so many people deeply engaged in moving the frontier forward.

38:07

A few qualities about string theory, which are weird.

38:09

I mean, a lot of physics is just weird and beautiful.

38:14

So let me ask the question.

38:15

What do you as most beautiful boss strength theory?

38:19

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

38:31

What attracted me to theater was the fact that it requires extra of space.

38:35

And this was an idea that intrigued me in a, in a very deep way, even before I really understood what it meant.

38:45

I somehow had.

38:47

I mean, talk about sort of the emotional part of consciousness and the cognitive part.

38:52

And some perhaps you call it strange in some strange emotional way.

38:56

I was in Nam bird with Einstein's general relativity, the idea of curved space and time before I really knew what it meant.

39:04

It just spoke to me.

39:06

I don't know how else to say it.

39:08

And then when I subsequently learned that people had thought about more dimensions of space than we can see and how those extra dimensions would be vital to a deep understanding of the things that we do see in this world four or five, six dimensions might explain why there are certain forces and particles and how they behave to me.

39:29

This was like amazing, utterly amazing.

39:31

And then when I learned that string theory embraced all these ideas, embrace the general theory of relativity embrace.

39:38

Quantum mechanics embrace the possibility of extra dimensions.

39:41

Then I was then I was hooked.

39:44

And so when I was a graduate student, we would just spend hours.

39:48

We, I mean, a couple of other graduate students and myself who had, have sort of worked really well together as at Oxford in England, we would, we would work these enormous numbers of hours a day, trying to understand the shapes of these extra dimensions, the geometry of them, what those geometrical shapes for the extra dimensions would imply for things that we see in the world around us.

40:08

And it was, it was a heady heady time and, and that kind of excitement has sort of filtered through over the decades.

40:16

But I'd say that's really the, the part of the theory that I think really hooked me most strongly.

40:26

How are we supposed to think about those extra dimensions?

40:28

I was supposed to imagine actual physical reality, or is this more in the space of mathematics that allows you to sort of come up with tricks to describe the four-dimensional reality that we mow more directly preceding?

40:43

No one really knows the answer, of course, but if I take the most straightforward approach to string theory, you really are imagining that these dimensions are there.

40:52

They're real. I mean, just as you would say, that the three space dimensions around us, you know, left right back, forth up down.

41:00

Yeah, we they're real they're here.

41:03

We are immersed within those dimensions.

41:05

These other dimensions are as real as these, with the one difference being their shape and their size differs from the shape and size of the dimensions that we have direct access to through, through human experience.

41:19

And one approach imagines that these extra dimensions are tightly coiled up, curled up, crushed together.

41:27

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

41:41

Nevertheless, according to the mathematics, the size and the shape of those extra dimensions leaves an imprint in the world that we do have access to.

41:50

So one of the ways that we have hoped yet to achieve, to make contact with experimental physics is to see a signature of those extra dimensions in places like the large Hadron Collider in Geneva, Switzerland.

42:02

And it hasn't happened yet.

42:05

It doesn't mean it won't happen, but that would be a stunning moment in the history of the species.

42:11

If data that we acquired in these dimensions gives us kind of in controvertible evidence that these dimensions are not the only dimensions.

42:21

I mean, how mindblowing would, would that be Large

42:25

Hadron Collider? It will be something in the movement of the particles or also the gravitational waves potentially be a place where you can detect signs of multiple dimensions, like with something that would LIGO, but much more active In

42:38

principle, all of these can work.

42:40

So one of the experiments that we had high hopes for, but not by high hopes, I'm actually exaggerating one of the experiments that we imagined might in the best of all, circumstances yield some insight we weren't with bated breath waiting for the result.

42:55

We knew it was a long shot when you slam protons together at very high speed of the large Hadron Collider.

43:01

If there are these extra dimensions and if they have the right form and that's a hypothesis that may not be correct, but when the proteins collide, they can create debris, energetic debris that can, in some sense, leave our dimensions and insert itself into the other dimensions.

43:18

And the way you'd recognize that is there'd be more energy before the collision than after the collision, because the debris would have taken energy away from the place where our detectors can detect it.

43:31

So that's, that's one real concrete way that you could find evidence for extra dimensions.

43:36

But yeah, since extra dimensions are of space and gravity is something that exists within, in fact is associated with the shape of space.

43:47

Gravitational waves in principle can provide a kind of, you know, tat scan of, of the extra dimensions.

43:56

If you had sufficient control over those processes, we don't yet, or perhaps one day we will.

44:04

Does it make you sad a little bit, maybe looking out into the future.

44:08

You mentioned ed Witten that no Nobel prizes have been given yet related to string theory.

44:14

Do you think they will be, do you think you have to have experimental validation or can a Nobel prize be given?

44:20

I don't think it has been given for quite a long time for a purely sort of theoretical.

44:27

Yeah. It certainly, as a matter of historical precedent has been the case that those who win the prize have established, investigated, illuminated a demonstrably real quality of the world.

44:43

So gravitational waves, the prize was awarded after they were detected, not, not the mathematics of it, but the actual detection of it, you know, the Higgs particle, you know, it was an idea that came from the 1960s, Peter Higgs and others, in fact, and it wasn't until 2012 on July 4th, when the announcement came that this protocol had been detected, the large Hadron Collider that people viewed it as eligible for the Nobel prize, the idea was there, the math was there, but you needed to confirm it indeed the prize ultimately was awarded.

45:20

So I'm not surprised.

45:21

In fact, I would have been surprised if a Nobel prize had been awarded in the arena of string theory because it's far too speculative right now, as far too hypothetical.

45:34

In fact, I am sympathetic to the view that it really shouldn't be called string theory.

45:40

It degrades the word theory because theory in science of course means the best available explanation for the things that we observe in the world.

45:51

The things that we measure in experiments about the world and string theory does not do that at least not yet.

46:00

So it really should be the string hypothesis, right?

46:03

We're at an earlier stage of development and that's not the kind of thing that Nobel prizes should be awarded for.

46:11

What do you think about the critics out there?

46:13

Peter Wood he's from Columbia, trying to think Sabine Hofstadter, is that a healthy thing, or should we sort of focus on sort of the optimism of, of these hypothesis?

46:25

Yeah. It's actually a good way that you frame it because I'm always somewhat repelled by views of the world that start from the negative.

46:39

Try to cut down an idea, try to say that's the wrong way of thinking about things.

46:47

And so on, I'm much more drawn.

46:49

Maybe it goes, I'm an optimist.

46:51

I don't know. I'm, I'm much more drawn to those who go out into the world with new ideas and, and don't try to cut down one idea, but rather present another one that might be better.

47:03

And so you make the first idea, maybe strength irrelevant because you've come up with the, the better approach to the world.

47:12

So do I think it's healthy?

47:14

Look, I think having a wide range of views and perspectives is generally a healthy thing.

47:21

I think it's good to have arguments within a subject in order that you stay fresh and you stay focused on the things that matter.

47:31

But at the end of the day, I think it's a more vital contribution to give us something new rather than to criticize something that's there.

47:41

Yeah, I'm totally with you, but it could be just the nature of being an optimist.

47:44

I, and also just the, a love of engineering.

47:49

It's there's, it, it, it helps nobody by criticizing the, the rocket that somebody else built, just build a big, bigger, cheaper, better rocket.

48:00

Right.

48:00

And

48:00

that

48:00

seems

48:00

to

48:00

be

48:00

how

48:00

a

48:00

human

48:00

civilization

48:00

can

48:00

progress

48:05

effectively. We we've mentioned the second law of thermodynamics.

48:10

I got to ask you about time.

48:12

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

48:19

I like to think of it as emergent.

48:20

I don't have a solid reason for that perspective.

48:26

I have a lot of hints of reasons that some of which come out of string theory and quantum gravity that perhaps be worth talking about.

48:33

But what I would say is time is the most familiar quality of experience because there's nothing that takes place that doesn't take place within an interval of time.

48:47

And yet at the same time, it is perhaps the most mysterious quality of the world.

48:54

So it's a wonderful confluence of the familiar and the deeply mysterious all in one little package.

49:00

If you were to ask me, what is time?

49:03

I don't, I don't really know.

49:05

I don't think anybody does. I can say what time gives us.

49:10

It allows us the language for talking about change.

49:13

It allows us to envision the events of the universe being spread out in this temporal timeline.

49:21

And in that way allows us to see the patterns that unfold within time.

49:27

I mean, time allows us the structure in the organization to think about things in that kind of a progression, but what actually is it?

49:36

I don't really know.

49:38

And that's so strange because we can measure it, right.

49:41

I mean, there are laboratories in the world that measure this thing called time to spectacular precision.

49:48

But you know, if you go up to the folks and say like, what is it that you're actually measuring?

49:56

I don't know that they can really articulate the kind of answer that you would expect from those who are engineering, a device that can measure something called time to that level of precision.

50:08

So it's a very curious combination.

50:12

What do you make of the one way feeling of causality?

50:16

Like is causality a thing or is that too just a human story that we put on top of this emergent phenomenon of Time?

50:26

I don't know. I can give you my, my guests, my intuition about it.

50:31

I do think that at the macroscopic level, if we're talking about sort of the human experience of time, I do think at the macroscopic level, there is a fundamental notion of causality that does emerge from a starting point that may not have causality built in.

50:47

So I certainly would allow that at the deepest description of reality, when we finally have that on the table, we may not see causality directly at that fundamental level, but I do believe that we will understand how to go from that fundamental level to a world where at the macroscopic level, there is this notion of a causes B a notion that Einstein deeply embraced in his special theory of relativity, where he showed the time has qualities that we wouldn't expect based on experience you and I, if we move relative To

51:22

each other, our clocks tick off time at different rate in our clocks is just a means of measuring this thing called time.

51:29

So this is really time that we're talking about time for you.

51:32

And time for me are different. If we're in relative motion, he then shows in the general theory of relativity, that if we're experiencing different gravity, different gravitational fields are actually more precisely different.

51:43

Gravitational potentials time will elapse for us at different rates.

51:47

These are things that are astoundingly strange that give rise to a scientific notion of time travel.

51:55

Okay. So this is, this is how far Einstein took us in wiping away the old understanding of time and injecting a new understanding of its quality.

52:05

So, so there's so much about time that's counter-intuitive, but I do not think that we're ever going to wipe away causality at the MC macroscopic at the macro scale.

52:16

I mean, there's so many interesting things at the macroscopic level.

52:19

They may only exist at the macroscopic level.

52:21

Like we already talked about consciousness, that that very well could be one of the things you mentioned, time travel.

52:27

So, I mean, according to Einstein and in general, what types of travel do you think are physical?

52:38

Universal? Well, certainly allows time traveled to the future.

52:42

And I'm not talking about the silly thing that you and I are now going into the future.

52:47

Second by second, by second, I'm talking about really the diversion that you see in Hollywood, at least in terms of its net effect, whereby an individual can follow an Einsteinian strategy and propel themselves into the future in some sense more quickly.

53:07

So if I wanted to see what's happening on planet earth, 1 million years from now, Einstein tells me how to get 1 million years from now, build a ship.

53:18

I got to turn to guys, you know, who know how to build stuff.

53:21

I can't do it. Like you built a ship that can go out into the universe, near the speed of light turnaround and come back.

53:28

Let's say it's a six month journey out a six month journey back.

53:31

And Einstein tells me how fast I need to travel.

53:34

How close to the speed of light I need to go.

53:36

So that when I step out of my ship, it will now be 1 million years into the future on planet earth.

53:44

And this is not a controversial statement, right?

53:49

This is not something where there's differences of opinion in the scientific community.

53:53

Any scientists who knows anything about what Einstein taught us agrees with what I just said, it's, it's commonplace, it's bread and butter physics.

54:02

And so that kind of travel to the future is absolutely allowed by the laws of physics.

54:09

There are engineering challenges, there, there technological challenges to this part.

54:14

Yeah, there are they're even biological challenges right there G-forces that you're going to experience it.

54:20

You know, so there's all sorts of stuff embedded in this, but those I will call the details and those details, not withstanding the universe allows this kind of travel to the future.

54:33

If I could pause real quick, you can also at the macro level with biology, extend the human lifespan to do a kind of travel forward in time.

54:44

If you expand how long we live.

54:48

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

54:58

Yes. So that's in the space of biology.

54:59

What about traveling backwards?

55:03

Yeah, that's the, that is a natural, next question.

55:07

Especially if you, if you're doing, if you're going on one of these journeys, is it a one-way journey?

55:12

Can you, can you come back?

55:13

And the physics community doesn't speak with a unified voice on this as yet.

55:20

But I would say that the dominant perspective is that you cannot get back.

55:24

Now, having said that there are proposals that serious people have written papers on regarding hypothetical ways in which you could travel to the past.

55:36

And we've seen some of these again, Hollywood loves to take the most sexy ideas of physics and build narratives around them.

55:45

This idea of a wormhole like Jodie foster in contact, went through a wormhole, a deep space, nine star.

55:52

I'm sure there are many other examples where these ideas that I've probably never even seen, but with wormholes, there's at least a proposal of how you could take a Wormald tunnel through space-time manipulate the openings of the wormhole in such a way that the openings are no longer synchronous.

56:09

They are out of sync relative to each other, which would mean one's ahead.

56:13

And one's behind, which means if you go through one direction, you traveled to the future.

56:17

If you go back, you travel to the past.

56:19

Now we don't know if there are wormholes Possible.

56:23

According to Einstein, They are possible according to Einstein, but even Einstein was very quick to say, just because my math allows for something doesn't mean it's real.

56:33

I mean, he famously didn't even believe in black holes.

56:36

Yeah. Didn't believe in the big bang. Right.

56:38

And yet the big, the, the black hole issue is really been settled.

56:42

Now we have radio telescopic photographs of the black hole and M 87.

56:48

It was in newspapers around the world just a couple of years ago.

56:51

So, so it's just to say that just because it's in Einstein's math, it doesn't mean it's real, but yes, it is the case that wormholes are allowed by Einstein's equations.

57:02

And in principle, you can imagine, you know, putting electric charges on the openings of the wormhole, allowing you to tow them around in a manner that could yield this temporal asymmetry between them maybe tow one of the mouse to the edge of a black hole in principle, you can do this slowing down the passage of time near that black hole.

57:22

And then when you bring it back, it will be well out of sync with the other opening.

57:27

And therefore could be a significant temporal gap between one and the other.

57:32

But people study this in more detail question.

57:35

Could you ever keep a wormhole open, assuming it does exist?

57:39

Could you ever travel through a wormhole or would there be a requirement to have some kind of exotic matter to prop it open that perhaps doesn't exist?

57:49

So there are many, many issues that people have raised.

57:53

And I would say that the general sentiment is that it's unlikely that this kind of scenario is going to survive our deeper understanding of physics when we finally have it.

58:05

But that doesn't mean that the door is closed.

58:06

So maybe there's a small possibility that this could be, That's

58:11

such an interesting way to put it.

58:12

It will not. This kind of scenario will not survive deep understanding of physics.

58:18

It's an interesting way to put it because it makes you wonder what kind of scenarios will be created by our deeper understanding of physics.

58:28

Maybe, sorry to go crazy for a second.

58:33

But if you have like the Penn site, cause of my idea that consciousness permeates all matter, maybe traveling in that, whatever, the laws of physics, the consciousness operates under, something like that, and that view of the university, if we somehow are able to understand that part, maybe traveling is super easy.

58:51

It

58:51

does

58:51

not

58:51

follow

58:51

the

58:51

constraints

58:51

of

58:51

the

58:51

speed

58:51

of

58:51

light,

58:51

something

58:51

like

58:58

this. Yeah. So look, I have, I have a definite degree of sympathy with the possibility that consciousness might be more than what we described earlier as just the by-product of mindless particles.

59:13

You just made The rock happy.

59:16

Exactly. You know, so, so it isn't the approach that feels to me the most likely, but I, I see the logic.

59:24

If you've got the puzzle, had a mindless particles build mind, one resolution might be, the particles are not mindless.

59:33

The particles have some kind of protocol conscious quality.

59:36

So there's, there's something appealing about that straightforward solution to the puzzle.

59:41

And if that's the case, if we do live in a pant cyclist world, where there is a degree of consciousness residing in everything in the world around us, then yes, I do think some interesting possibilities might emerge where maybe there's a way of communing with physical reality in a, in a deeper way than we have so far.

1:00:02

I mean, we, as human beings, a vital part of our existence as human to human communication contact, we live in social groups and that's what it's allowed us to get to the place where we've gotten.

1:00:14

Imagine that we have long missed that there's other consciousness out there and some kind of relationship or communion with that larger conscious possibility would take us to a different place.

1:00:26

Now, do I, do I buy into this yet?

1:00:29

I don't, I don't see any evidence for it, but do I have an open mind and allow for the possibility in the future?

1:00:36

Yeah, I do.

1:00:39

So if that's not the case and you have these simple particles that at the macro level emerges some interesting stuff like consciousness, another thing you write about in the, on till the end of time book is the thing that it seems to emerge at the macro level is the feeling like, like there's a freewill, like we decide to do stuff and you have a really interesting take here, which is no, there's not a freewill out.

1:01:09

I'm just going to speak for you. And then you shouldn't correct me.

1:01:11

No, there's not a freewill, but there is an experience of freedom.

1:01:17

Yeah. Can, which I, I, I really loves where does the experience, where does freedom come from if we don't have any kind of physics-based freeway.

1:01:28

Yeah. And, and so the idea follows naturally from all that we've been talking about, let's make the assumption that all there is in the physical universe is stuff governed by laws.

1:01:40

We may not have those laws may, may not know what the fundamental stuff is yet, but everything we know in science points in the direction that it's physical stuff governed by universal laws and that being the case or that being the assumption, then you come to a particular collection of those ingredients called the human being.

1:02:01

And that human being has particles that are fully governed by physical law.

1:02:06

And when you then recognize it, every thought that we have every action that we undertake is just the motion of particles when I'm thinking thoughts right now, of course, at this level of description, it is the motion of particles cascading down, various neurons inside of my head and so on.

1:02:25

And every single one of those motions collectively and individually is fully governed by these laws that we perhaps don't have yet.

1:02:35

But we imagine one day we will, that leaves no opportunity for any kind of freedom to break free from the constraint of physical law.

1:02:44

And that is the end of the story.

1:02:46

So the traditional intuitive notion of free will that we're the ultimate authors of our actions that we were, the buck stops that there is no antecedent.

1:02:54

That is the cause for our decided to go left or right choose vanilla or chocolate live or die.

1:03:03

That intuitive sensation does not have a basis in our understanding of physical world.

1:03:09

So that's the end of the free will of the traditional sort.

1:03:12

But then your question is, what about this other kind of freedom I talk about and the other kind of freedom, if you focus on intently, I think is actually the true version of freedom that we feel.

1:03:27

And that freedom is this.

1:03:28

You look at inanimate objects in the world, rocks bottles of water, but either they have a very limited behavioral repertoire, why their internal organization is to course for them to do very much, right?

1:03:44

You have to, you try to have a conversation with a glass of water.

1:03:47

You send sound waves.

1:03:49

It doesn't do much may vibrate a little bit, but the repertoire of responses are incredibly limited.

1:03:54

The difference between us and a rock or a bottle of water is that our inner organization by virtue of eons of evolution by natural selection is so refined.

1:04:05

So spectacularly ordered that we have a huge repertoire of behaviors that are finally attuned to stimuli from the external world.

1:04:16

You asked me a question that's a stimulus.

1:04:18

And all of a sudden these particle processes go into action.

1:04:22

And this is the result.

1:04:24

This answer that I'm giving you. So the freedom that we have is not from the control of physical law.

1:04:30

The freedom that we have is from the constrained behavior that has long since govern inanimate objects.

1:04:36

We are liberated from the limited behavioral repertoire of rocks and bottles of water to have this broad spectrum of responses.

1:04:45

Do we pick them? We do not do refer freely, choose them.

1:04:48

We do not, but yet we have them and we can Marvel at those behaviors.

1:04:54

And that's the freedom that we have, The

1:04:57

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

1:05:01

Is there something to be said about emergence?

1:05:04

I don't know if you know, I've looked at much about objects that I seem to love way more than anyone else, which is sell they're tough.

1:05:14

Yeah. Like game of life type of stuff there, you know, from simple things, emerges beautiful complexities.

1:05:21

And so that's that repertoire is like, it seems if you have enough stuff, just beautiful complexity emergencies that sure as heck or humanized looks like there's consciousness there, there's free.

1:05:37

Will there's little objects moving about and making decisions.

1:05:40

I mean, all of that, you could say it's anthropomorphization, but it sure as heck feels like they're organisms making decisions.

1:05:49

What is, what is that, that emergence thing is, is that within the realm of physics to understand, is it, is it within the realm of poetry where, cause what does that look like?

1:06:02

Complex systems emergencies? What is that?

1:06:04

Will that ever be understood by science?

1:06:07

So here's the, here's the way that I think about it.

1:06:09

So there are clearly qualities of the world that emerge on macroscopic scales, our sense of beauty, wonder consciousness, all of these kinds of qualities.

1:06:20

Do I feel that they ultimately are explainable from the laws of physics I do.

1:06:27

There is nothing that's not ultimately ultimately explainable with the laws of physics from this physicalist perspective, which is what I take.

1:06:35

So you got the particles, you got the laws and you have things that emerge from the choreographed motions of those particles.

1:06:45

But is that the best language for talking about these emergent qualities?

1:06:51

Usually not.

1:06:52

If I was to take something even more mundane, like a baseball flying through the air, if I was to describe it in terms of the corks and the electrons, I'd give you this mountain of data with, you know, 10 to the 28 particles and all of their coordinates in spaces of at a time, I hand you this mountain of data and be like, I don't know what this is.

1:07:14

And then if you really were clever and looking, oh, it's up baseball just described in the, in the least economical way possible, it is much more useful and insightful to talk about the baseball find through the air.

1:07:27

Similarly, there are things at the macroscopic level, like human experience and human emotion and human action and the sensation of free will that we undeniably all have.

1:07:40

Even if it itself doesn't have a basis in our understanding of the physical world, it's useful to talk about things in this very human language.

1:07:49

And so, yes, it's vital to talk about things in the poetic language of human experience, but do not lose sight of the fact.

1:07:56

And some people do they say, oh, it's just an emergent phenomenon.

1:07:58

Don't lose sight of the fact that emergent phenomenon are emerging from this deeper understanding that comes from the reductionist account of physical law.

1:08:08

And there's a lot of insight to come from that such as the freedom that you thought that you had the freedom will, that you thought you had, it doesn't have a basis in that reductionist account.

1:08:18

So it's not real.

1:08:22

So speaking of the poetry of human experience, you mentioned the images of the black holes.

1:08:26

How does it make you feel a few years ago when that first image came out?

1:08:31

It's amazing. It's a sense of, well, I guess the feeling was both amazing and, and there's a little sense of jealousy is not quite the right word, but a sense of longing.

1:08:45

Yeah. I think that's a better word because here's a subject that started with Einstein back in 1915, writes down the equations of the general theory of relativity.

1:08:55

And then there are scores of individuals over the decades, you know, starting with people like Carl Schwartz, child who analyzed the equations, see the possibility of black holes.

1:09:06

People develop these ideas, John Wheeler, all these greats of physics, it's still a hypothetical subject.

1:09:11

It gets closer to reality through observations of the center of our galaxy stars, whipping around in a manner that could only really be explained by there being a black hole in the center of our galaxy.

1:09:22

But it was still indirect tax.

1:09:24

You have a direct image that you can look at what a beautiful arc narrative arc from the theoretical to the absolutely established.

1:09:34

And that's what we hope will happen with other areas, for instance, string theory, right?

1:09:40

I mean, wholly mathematical subject at the outset and still pretty much a wholly mathematical subject today.

1:09:48

Yeah. Do we long for that image where we can look at it and say string it's really maybe, you know what I mean, how thrilling, how thrilling to be part of that journey to be part of that, that step that moves things from the abstract to the concrete.

1:10:06

Yeah. So like the image of the DNA, the early images of DNA, for example, but there is something especially, so the problem with strings is they're tiny.

1:10:16

So it's harder to take a picture in the, in the following sense.

1:10:20

When you think of a black hole, I mean, you have a swirl of, I guess, what is, I, I don't even know it's dust to go whatever light Accreting

1:10:28

onto the event Horizon,

1:10:30

and then there's darkness center.

1:10:32

And then you just imagine, so that picture in particular, I guess, is a gigantic black hole.

1:10:38

So you just, I mean, it's Terrifying

1:10:41

billions of times the mass of the sun.

1:10:43

Yeah. So it is both exciting and terrifying.

1:10:45

I mean, I don't, I don't know where you fall in the spectrum.

1:10:47

I think it's exciting at first, like the longer I think about it, every time I think about it, the more terrifying it becomes.

1:10:54

So it always starts exciting.

1:10:56

And then it goes to terrifying and both our feelings, very human feelings that I appreciate.

1:11:02

It's like terrified.

1:11:04

Awe somehow it's still beautiful.

1:11:08

That's a good way of saying it. I think I kind of share that reaction because there is a way in which when you work on this subject, like all the time I teach it, I teach about black holes, right?

1:11:19

The equations on the Blackboard, the ideas reside in a very cognitive, I don't know, mathematical portion of the brain or at least for me.

1:11:32

And it's only when you like sit down and it's quiet and you start to contemplate, wait, wait, wait, wait.

1:11:39

This is just like a mathematical game.

1:11:41

There are these monsters out there now I, don't not net in a, in a sense of, I fear for my life, but it's a sense of how extraordinary is this universe.

1:11:53

And so it is breathtaking how powerful Nature.

1:11:57

Yeah. How stupendously powerful nature is.

1:12:01

And so there is a deep sense of humility that I think this instills, if you really allow the ideas to sink in, Well,

1:12:14

I have to ask about the most stupendously powerful thing to have ever happened in our universe, which is the big bang.

1:12:21

Yeah. What's up with the big bang.

1:12:23

So we can, I mean, with gravitational waves, the hope is you have more and more accurate measurements of the gravitation waves.

1:12:31

You can crawl back further and further back in time towards a big bang.

1:12:34

Do you have a hope that we'll be able to understand the early spark that created Our

1:12:43

universe? Yeah. You know, that and the deep interior of a black hole, I think of the biggest mysteries that we hope the melding of quantum mechanics and gravity will reveal will eliminate.

1:12:57

And you know, what question could be more captivating then?

1:13:02

Why is there something rather than nothing, right?

1:13:05

Why is there a universe at all?

1:13:08

And will the theories that we're developing, take us to an answer to that.

1:13:14

I don't know, even if we truly knew what the big bang is, and that's a big question it's own, right.

1:13:18

When would still be left with the question?

1:13:20

Well, okay. So you've explained the process by which a tiny nugget of a universal kind of negative spacetime can undergo some kind of growth to you, the world around us.

1:13:35

But presumably in that explanation, you're going to involve mathematics and some ingredients like quantum fields or, or matter, or energy or something, where did that stuff come from?

1:13:49

You know, can we get to that level of explanation?

1:13:52

I don't know, but it is remarkable that if you ask what happened a millionth of a second after the big bang, it's not really that controversial any longer.

1:14:05

Right. Even though there's a lot of argument in the field and it's very heated right now, I should say regarding what is the right theory of the big bang?

1:14:15

What is the right theory of early universe cosmology, where, I mean early much earlier than a month of a second, a lot of dissent, a lot of heated arguments about that.

1:14:27

No pun intended. Yeah. Right. Exactly.

1:14:29

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

1:14:33

Yeah. And, and we're pretty firm grant.

1:14:35

Isn't that amazing right.

1:14:37

To, to understand, you know, what happened from that point forward, but to go back is, is, is controversial.

1:14:43

So there's this theory called inflationary cosmology, which I would say has been the dominant paradigm since the early 1980s.

1:14:52

So what does that mean roughly 40 years now it's been the dominant cosmological paradigm and it makes you so of a curious feature of Einstein's general theory of relativity.

1:15:01

His theory of gravity Reinstein shows us mathematically that gravity cannot only be attractive.

1:15:06

You know, the kind of gravity that we're used to things pulled together, but it can also be repulsive.

1:15:11

And that fact is then leveraged by people like Alan Guth and Andre Linda.

1:15:19

And at the time Paul Steinhardt and Andres Hallberg and others to say, okay, if we had a little nugget in the earlier universe, which was filled with the stuff that yields this repulsive gravity, well, that would have blown everything apart.

1:15:32

It would cause everything to swell, beautiful explanation for what the bang in the big bang was.

1:15:38

And then people mathematically analyze the consequences of this idea and then make predictions for tiny temperature differences across the night sky that in principle could be measured.

1:15:49

You send up balloons, you send up satellites with very refined the monitors and they measured the temperature of the night sky and the statistical distribution of the temperature differences agrees with the mathematical predictions.

1:16:04

Yeah. I mean, it's amazing.

1:16:07

You just sort of have to stand in awe of this insight.

1:16:10

So you think, aha, the theory has been established, but scientists are an incredibly skeptical bunch and some scientists, including one of the people who helped develop the theory at the outset, Paul Steinhardt comes along and says, well, yeah, it's done.

1:16:27

This theory has done pretty well so far, but there are aspects of this theory that are making me lose confidence.

1:16:33

For instance, this theory seems to suggest that there might be other universes, like how do you make sense of it theory that suggests there are other universes or are there others who come along and say, this theory seems to talk about length scales that are minuscule even by the so-called plank lane, the sort of shortest length that we can imagine making sense of and a theory of quantum gravity, how do you make sense of that?

1:16:58

And so-and-so they develop a list of, of things that they considered to be chinks in the inflationary, cosmological theories armor, and they other ideas which they claim you'll the same predictions as inflation because of mileage for those temperature differences across space, but don't suffer from these problems.

1:17:18

And then the inflationary cosmology folks even no, no, no, hang on.

1:17:22

Yeah. Your theory suffers from different problems.

1:17:25

And so the arguments, cause it's a healthy debate.

1:17:28

Talk about real debates in science.

1:17:29

So when you ask what's up with the big bang, I don't know right now, if you would've asked me five years ago, maybe even less than that three or four years ago, I've said look, inflation at cosmology has some issues, but the package of explanations it provides is so potent and the issues that beset it are seemingly solvable to me that I would imagine it's going to in the end, win out.

1:17:57

I would still say that today, but I wouldn't say it as loudly.

1:18:01

It wouldn't say it as confidently.

1:18:03

I think it's worth thinking about alternate ideas and it could be the case that the paradigm at some point shifts Does

1:18:12

the dark matter and dark energy fit into the shifting of the explanations for Those.

1:18:17

Yeah, certainly. So, so dark energy has a in, in the inflationary theory is kind of a big mystery.

1:18:25

So dark energy is the observational realization in the last 20 years that not only is universe expanding, it's expanding evermore quickly.

1:18:36

Something is still pushing things outward.

1:18:39

And the explanation is that there's like a residual version of the repulsive gravity from the early universe, but it's such a strange number when you write that amount of dark energy using the relevant units and a theory of quantum gravity.

1:18:54

It's a decimal point fall by like 120 zeros.

1:18:58

And then a one we're not used to those kinds of numbers in physics.

1:19:03

We're used to half one PI E squared to two.

1:19:10

Those are the kinds of fundamental numbers that emerge in our explanations of the world.

1:19:14

And we look at this bizarre number, decimal point, all the zeros and, and one, we say, something's wrong there?

1:19:21

Like where would that number have come from?

1:19:25

And now there are people who suggest resolution to it.

1:19:27

So it's not like we're totally in the dark on it. But those people like Paul Steinhardt who have alternate cosmological theories, cyclical cosmologists as they call it, claim that they have a more natural explanation of the dark energy that it naturally feeds into a cyclical process.

1:19:44

That is their cosmological paradigm.

1:19:47

So yeah, if the cosmology should change, it's conceivable our view of dark energy may change from deeply mysterious to deeply integrated into a different paradigm that is possible.

1:20:01

I think it's Roger Penrose that think that information can bleed through from before the big bang to the, after the big bang, is that a, is the big bang, like a full ratio of the hard drive or is there some information that could bleed?

1:20:14

Yeah, I mean, so, so Roger is among the most creative thinkers of the last a hundred years rightly won the Nobel prize for his insights into singularities in space time that we know to afflict our mathematical solutions of black holes and the big bang and so forth.

1:20:33

And he has an enormously fertile imagination and, and I mean that in the most positive sense.

1:20:41

And so he has put forward this idea, this conformal cyclic cosmology, I think is the, the official title though.

1:20:49

I could be getting that wrong.

1:20:51

I can't say that I've studied it.

1:20:53

I have seen lectures on it.

1:20:55

I don't find it convincing as yet.

1:20:58

It feels like it's being built to find a solution as opposed to sort of more naturally emerging.

1:21:06

Maybe Roger would say otherwise.

1:21:09

And I don't mean to in any way, cast dispersions on the work it's, it's vital and interesting and people are thinking about it.

1:21:16

I don't consider it as close a competitor to say the inflationary theory as for instance, the stuff that Paul Steinhardt has put forward.

1:21:26

But again, you've got, you got to keep an open mind in this, in this business when there's so much that we don't yet understand A

1:21:34

while to think that information could survive. Something like that, just like it is wild to imagine that information could escape a black hole, for example, or it just seems like by construction, these things are supposed to not bleed out.

1:21:49

Okay. But one of the challenges and all of these series is when we talk about a singularity has this really sexy term, that singularity, but a singularity is, is in more ordinary language, a physical system where the mathematics breaks down, it's nonsensical.

1:22:05

It's like taking one divided by zero.

1:22:08

You put that into a calculator and it says E error, right?

1:22:11

It does not make sense. It doesn't compute.

1:22:13

And so it's very hard to make definitive statements about things like the big bang or about black holes until we cure to mathematical singularities.

1:22:24

And there are some who claim that in certain regimes, the singularities have been cured.

1:22:30

I don't by any means, think that there's consensus on these ideas.

1:22:35

So when, when talks about information sort of bleeding through the big bang, you've really got to make sure that the equations have no singularity.

1:22:42

You talk about cyclical cosmology.

1:22:44

You've got to make sure that the equations don't have any singularities as you go from say one cycle to the next.

1:22:49

Now some of the proponents of these theories claim that they have resolved these issues.

1:22:52

I don't think that there's a general sense that that is the case as yet, but it could be that look, I, life is so short that I haven't had the time to deeply delve into all the mathematical intricacies of all the ideas that have been put forward, but did that.

1:23:07

I'd never do anything else, but that that's what the issue is.

1:23:10

And of course, it's just math. There may be holes that there may be a, there may be gaps in our understanding in the way we're modeling physical vanilla.

1:23:21

That's the point. In fact, when you said it was about to jump in and say modeling, but you got there first and it's exactly the right point.

1:23:26

You're talking about the universe here.

1:23:29

Yeah. Right. And then how do you, how do you talk about the universe with a straight face mathematically, the way you do it is you, you simplify, you throw away those characteristics of the universe that you don't think are vital to a full understanding.

1:23:43

And so we're going to get to a point and people are starting to where we've got to go beyond those simplifications.

1:23:48

And so cosmology has for a long time model, the universe in the most simplest terms, homogeneous isotropic, it has just a few parameters that describe it, the average density of mass and energy and so forth.

1:24:04

We have to go beyond those simplifications and that will require putting these things on computers.

1:24:08

We're not going to be able to do calculations there so much as astrophysics has gone beyond many simplifications to now give really detailed simulations of star systems and galaxies and so forth.

1:24:20

We're going to have to do that with cosmology and people are starting to do that today.

1:24:25

Yeah. I've seen some interesting work on simulation, most simulation because Mazda, by the way is just awesome.

1:24:31

But you know, just like simulation of the early formation of our solar system don't understand how the, like the Oracle cloud and just, I don't know, the, the whole of it, how earth came to be.

1:24:43

Yeah. Like how Jupiter just protects us, protects us.

1:24:48

And then there's like weird, like moons and volcanoes and w and like modeling all of that.

1:24:56

The formation of all of that is fascinating.

1:24:59

Yeah. Because that naturally leads the question of how does life emerge in these kinds of rocks?

1:25:05

How does a rock become a rabbit?

1:25:08

Yeah. But speaking of models, there's an equation called the Drake equation.

1:25:15

Yeah. We were talking about life.

1:25:17

Have to ask when you, at the highest level, first, when you look out there, how many alien civilization do you think are out there?

1:25:26

Well, zero one or many.

1:25:30

So if you say civilization, I would bring my number way down.

1:25:36

It could be zero.

1:25:39

If you talk about life, I think it could be many, as we were saying before, I think the move from life to consciousness, the kinds of beings that would build what we would recognize as a civilization, that may be extraordinarily rare.

1:25:59

I hope it's not, you know, as a kid, I love star Trek.

1:26:03

I just love the idea that we would be part of some universal community where look experienced on planet earth.

1:26:11

Suggest it doesn't always go so well when groups who are separated, try to come together and live in some larger collective.

1:26:18

But again, as an optimist, how amazing would it be to converse with an alien civilization and learn what they've figured out about physics and cosmology and, and compare notes and, and, and learn from each other in, in some, some wonderful way.

1:26:34

I love that idea. But if you asked me the likelihood of it, I would err on saying it may be so improbable that the conditions can Spire to allow life, to move to this place of, of consciousness.

1:26:50

That it might be rare.

1:26:53

It might be over simplifying things, but just observing the power of the evolutionary process.

1:26:57

I tend to believe.

1:26:59

And like, you read different theories of how we went, how homosapiens evolved.

1:27:07

It seems like the evolutionary process naturally leased to homosapiens or, or creatures like that, or much better than that.

1:27:18

So to me, the several scary scenarios.

1:27:22

So, okay.

1:27:25

The positive scenario is life itself is really difficult.

1:27:28

So that origin of life is difficult.

1:27:31

That's exciting for many reasons, because we might be able to prove that wrong easily in the near term by finding life elsewhere.

1:27:40

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

1:28:04

So with power comes great responsibility.

1:28:07

And then we end up destroying ourselves.

1:28:10

That's the, the scariest, the, the positive, I guess, version is that maybe we're being watched sort of like, does it transition to where you don't want to ruin the primitive villages out there?

1:28:26

And so there's a protective layer around us there they're watching.

1:28:30

So where, where do you in these possible explanation to the Fermi paradox?

1:28:35

Why haven't we contacted aliens?

1:28:37

Do you land on?

1:28:40

I think the most straightforward explanation is that there aren't any, now there are many other explanations too.

1:28:48

So I, you can't be dogmatic about things that are just sort of gut feel, but you know, one of my favorite Twilight zone episodes on this one where, you know, there's aliens, civilization finally comes to planet earth and it gives us this book that they really want us to, to have and to hold.

1:29:07

And it's in this foreign language, you don't understand it, the cryptographers, they desperately try to decipher it as humans are going to visit this other alien planet.

1:29:18

And they're all sending back postcards how wonderful it is and so forth.

1:29:20

And they, they finally the decipher, the title it's to serve man.

1:29:25

And everyone's so thrilled, oh, they're here to serve as it all makes sense.

1:29:28

And then just as the, one of the final cryptographers is going onto the alien ship, his, his helper runs and says, I've deciphered the rest of the book to serve man.

1:29:39

It's a cookbook, you know, so, you know, so yeah.

1:29:43

Is that a possibility?

1:29:46

Sure. You know, and, and so could they be watching us and just sort of waiting for us to get to a mature enough level?

1:29:54

I don't know. It strikes me well, you know, I think it'd be better to have this conversation after the James Webb telescope.

1:30:00

I mean, I do think that if we look at the atmospheres of many planets, you mean, there's now an estimate now that there's on order of one planet per star on average.

1:30:13

So we've long known that, you know, the galaxy hundreds of billions of stars, numbers of gallium, hundreds of billions of galaxies that we're talking about hundreds of billions, of hundreds, of billions of planets.

1:30:23

Oh my. You know, and if we start to survey some of these planets and one after the other, after the other, we just sort of find no evidence for any of the biological markers.

1:30:35

It could be, of course, maybe life takes a radically different form.

1:30:39

It'd be hard to know that, but I think, you know, that would at least given some insight on the life question, but I just don't see how we get insight on the civilization or consciousness question without, you know, the direct connection.

1:30:52

And, and it strikes me that if consciousness is ubiquitous, let's say life is I'm willing to grant that if consciousness is also ubiquitous, then I don't understand why they haven't been here or why there hasn't been set because presumably they should be much further ahead of us.

1:31:13

How unlikely would it be that we're like of all consciousness in the universe were the most advanced, that'd be such a special place for human beings.

1:31:22

That it's hard for me to grant that as a likely possibility, rather, I think we're kind of running the mill and there are many who are far more advanced than us.

1:31:31

And I don't think that they would expend the energy to hide themselves.

1:31:35

So I don't think they care enough.

1:31:39

So I see that's actually what I, I believe that there's a very large number of civilizations that are far more advanced than us, but my sense is the humans they're exceptionally limited both in our direct sensory capabilities and our physics, our tools of sensing that just like with the string and the multiple dimensions, we're just not like it's like, I honestly believe that it could be stuff in front of our nose that we're just not seeing work.

1:32:09

Cause we're too dumb too, too much hubris.

1:32:13

And I mean, it's a bunch of stuff and too ignorant as to the fabric of reality, all of those things when we're young in terms of intelligence, But

1:32:25

I guess what I'd say is like I'm on board with all of that as a real possibility, but then it does strike me that we are sufficiently able to observe the unit.

1:32:37

Look, we can look back to, you know, a fraction of the duration from here to there just a fraction is left that we are unable to see.

1:32:47

So however young we are, we have been able to sort of Pierce the universe and it just strikes me that there would be some signature, but maybe, maybe that that's coming.

1:33:00

But, but the good look having said that I do look, I, I certainly note the fact that it's rare that I stooped down while walking in Manhattan and sorta dig up some aunts in the bushes on the side of the street and talk to the ants.

1:33:17

Right. Because it's just not interesting to me. So if we're like the ants on the cosmological landscape, then yeah.

1:33:22

I can imagine that the super-advanced aliens would be like, like who would ever, you know, but, but I feel like we're sufficiently advanced that there should be some signal signature of that, but maybe it's, I

1:33:34

think the deeper, fundamental problem between us and the ants is that we don't have a common language.

1:33:38

It's not, it's not the interest it's that we don't even have a common language.

1:33:42

And so the alien civilizations don't even know how to be like, we humans have convinced ourselves for a special, because we developed the language.

1:33:51

You talked about, you talk about the importance of language to intelligence, but it makes you wonder like how very niche is that fan like club that we've like tribe we've created of language and linguistic type of systems that are very specific to our particular kinds of brains.

1:34:08

And we share ideas together. We're all super excited that we can understand the universe.

1:34:11

Cause we came up with some notation.

1:34:13

Yeah. And math. I wonder if there's some totally other kinds of language that communicates on a different timescale with different, very different mechanisms in a space of information that just is not it's everything.

1:34:26

Everything is lost in translation.

1:34:29

Yeah. And it could well be it was a look. I mean, I think part of the reason I go toward the possibility of the soul intelligence is there's a certain kind of romantic appeal to looking out in the cosmos and it's just quiet and it's just eternal silence.

1:34:47

There's some, there's something that appeals to me at an emotional level that way.

1:34:53

But yeah, I mean, nobody, nobody knows.

1:34:56

And it's certainly a conceivable that we're this just a radical mismatch between the kinds of things that we are able to observe and sensitive to versus the kinds of structures that permeate the universe in a manner that simply were unable to detect Our

1:35:17

loan. That is exciting in one of the ways it's exciting is that it's up to us to become, to expand out into the universe, to permeate consciousness out into the universe.

1:35:32

So that's where space exploration comes in.

1:35:35

Let me ask you as somebody who was a string theorist, the physicist, do you think space exploration, colonizing space is a physics or an engineering problem?

1:35:48

Yeah, I think it's fundamentally an engineering problem.

1:35:50

If we're not trying to do things like build wormholes the way they did say an interstellar to get to a different place for trying to travel near the speed of light so that we would actually be able to traverse interstellar distances.

1:36:06

I mean, without that our colonization will happen in a very, very slow rate, right.

1:36:13

But one of the beauties of relativity is if you do travel near the speed of light, you, you can actually go arbitrarily far in a human lifetime.

1:36:22

He was like, how's that possible? You can't go billions of light years.

1:36:25

All you can actually, because as you can do this blade of light the way in which space and time change allows you to go in principle arbitrarily far, that's, that's very exciting.

1:36:35

But if we put that physics side of the issue in the manipulation space and time to the side, yeah.

1:36:41

I think it's a deep engineering problem.

1:36:43

You know, how do you Terraform other planets?

1:36:47

I mean, how do you go beyond our local neighborhood say without, you know, using the ideas of relativity.

1:36:55

So I think it's all quite exciting.

1:36:57

And I think the idea is, you know, using solar sales, you know, people have developed and you know, trying to take that first step to Mars.

1:37:06

I think that's a vital and valuable step to take.

1:37:09

But yeah, I think these are fundamentally engineering challenge Or

1:37:12

extending the human life span through biology research, or maybe reducing what it means to be a human being into information and uploading certain parts of it.

1:37:23

Maybe not all the full resolution of a human life, but maybe the essential things like the DNA and be able to reconstruct that human being.

1:37:31

But

1:37:31

no,

1:37:31

I

1:37:31

have

1:37:31

to

1:37:31

ask

1:37:31

about

1:37:31

Mars,

1:37:31

you

1:37:31

know,

1:37:31

do

1:37:31

you

1:37:31

find

1:37:31

the

1:37:31

dream

1:37:31

of

1:37:31

human

1:37:31

stepping

1:37:31

on

1:37:31

Mars

1:37:31

stepping

1:37:31

foot

1:37:31

first,

1:37:31

but

1:37:31

also

1:37:31

colonizing

1:37:31

Mars

1:37:31

one

1:37:31

that's

1:37:31

worth

1:37:31

us

1:37:31

fighting

1:37:31

for

1:37:50

Yeah, hugely. So, I mean, I think what we have long been, not always in the best way is a species of explorers in the literal sense of traveling from one part of the world to another or in a more metaphorical sense of trying to travel through our minds, to the quantum realm.

1:38:10

We're back to the big bang into the center of black holes.

1:38:13

So I think that's fundamentally part of, of the human spirit.

1:38:16

So I do think that's a vital part of our heritage prod forward into its next incarnation.

1:38:25

That's who we are.

1:38:29

Do you think there'll be a day in the future where a human being is born on Mars and has to learn about his or her human origins on earth?

1:38:43

Like they'll have to read in a book.

1:38:46

Yeah. I don't think it'll be a book at that stage. They'll probably just be uploaded into the head or something or, you know, imprinted into the DNA and then they just sort of sense it.

1:38:53

But yeah, I think there's there's well, look, the issue you raised before is the vital one.

1:38:59

Is it the case that any sufficiently advanced civilization destroys itself is that sort of commonplace quality?

1:39:06

I mean, that's the other potential answer to the Fermi paradox?

1:39:09

Why aren't they here?

1:39:11

Because by the time they got to the technological development where they could travel here, they blew themselves up, they destroyed themselves and that's a, you know, an, you know, an unfortunate, but you know, not a hard to imagine possibility based on things that have happened here on planet earth.

1:39:28

But, but putting that to the side, I think it, you know, that's the big obstacle, but put it to the side, we will resolve the engineering challenges and, and, you know, I should, I should probably modify my answer from before when you said, is it engineering or physics?

1:39:42

It's really both. Right.

1:39:43

So, so we will surmount the engineering challenges and that will then make the physics challenges relevant.

1:39:49

It'll make it relevant to figure out how to travel near the speed of light, a little, make it relevant to learn how to manipulate the shape of space-time and so forth.

1:39:58

So, so I think it's a multi-stage process where it is engineering and ultimately physics.

1:40:04

And if we stick around long enough, those are the kinds of challenges I think that we're ultimately going to surmount.

1:40:09

And then the Does excite is figuring out how to harness energy enough to travel outside of the solar system, which seems like a heck of a difficult journey, but even Mars itself of, I don't know, maybe because I, I was born in the Soviet union and it was born with the, you know, looking up at the stars and that dream of like the highest of human achievement, his ability to fly out there to the, not to join the stars.

1:40:36

I really liked the idea of going to Mars of, and not just stepping foot on Mars and it wasn't until maybe I'm misinformed.

1:40:47

But for me personally, it wasn't until y'all Musk started talking about the colonization of Mars, did I realize like we, we, humans can actually do that.

1:41:00

And the first of all, the importance of somebody saying that we can do these seemingly impossible things is immeasurable because you know, the fact that he, he placed that into my mind and into the minds of millions of others, maybe hundreds of millions, maybe billions of others, young kids today.

1:41:21

I mean that that's going to make it a reality.

1:41:23

I, for some reason, deeply excited, even though my work isn't AI that echoes all of this, I'm excited by the idea that somebody would be born, as we were saying on Mars and sort of look up and be able to see what the telescope earth and say, that's where I came from.

1:41:44

I don't know that, that idea scale to other planets, to other solar systems.

1:41:51

Yeah. That's really Hugely exciting.

1:41:52

I think you're absolutely right.

1:41:54

I mean, the vital thing is to dream, right?

1:41:59

I mean, it sound hackneyed, but it is so important for, for young kids for the next generation to, to think about the things that are seemingly impossible.

1:42:10

I mean, that's what makes them possible.

1:42:12

And this is one which is concrete enough.

1:42:15

I mean, this is something that's going to happen soon in terms of actually going to Mars.

1:42:19

And then the next step of establishing some presence, some semi-permanent or permanent presence.

1:42:28

This is, this is not something that's going to wait till the 25th century.

1:42:32

I mean, this is something that's going to happen relatively soon.

1:42:34

So I'm in, it could well be in your lifetime, unlikely mine, but possibly in your lifetime that that kid will be born and, and, and have the experience that you described.

1:42:43

So yeah, it's expect tactically exciting.

1:42:47

And I actually, I would love to go on Mars and one of the early You

1:42:51

would, yeah, It was one way I was, I'm happy to want.

1:42:55

Really. Wow. And I'm single, if there's ladies out there that want to start that family, let's go, let's go out to Mars.

1:43:01

Now, I think I have to tell you, You

1:43:04

spoke about terror thinking about like black holes.

1:43:07

If I actually think about going to Mars and being on Mars and put myself in there fully that's terror inducing the idea of, to be in this foreign world where you can't come back where you've made this, this choice that can't be reversed or, you know, at some point it may be.

1:43:27

But, but in that guys, that to me carries a deep sense of terror.

1:43:34

You know, I, I feel that sense of terror every time talked about this and on the road is, you know, when you leave a place, if you're honest about it, like life is short.

1:43:45

And when you leave a place, you move to a new place and you think of all the friends, maybe family leaving behind as you drive over the hill, that that really is goodbye.

1:43:56

Like we sometimes don't think of it that way when we're moving, but that really is goodbye to that life, to the person you were to all the people.

1:44:03

Maybe if it's close friends, you'll see them maybe 10, 15 more times in your life.

1:44:08

And that's it. And it you're saying goodbye to all of that.

1:44:11

And so in the same way, I see it as way more dramatic when you're flying away from earth.

1:44:17

And it's like, it's goodbye to Dunkin donuts and Starbucks and it's goodbye to whatever.

1:44:24

I don't know why I picked those, but some, all the things that are special to earth it's goodbye, but that's life, I suppose, more what excites me about that kind of journey is it's a distinct contemplation of your mortality, acceptances your mortality.

1:44:41

You're saying just like when you take on any difficult journey, it's accepting that you're going to die one day and might as well do something truly exciting.

1:44:54

Yes. I mean, I, well, you know, I'm with you on that.

1:44:56

I, I'm a strong believer that deep underneath human motivation is this, this terror of our own mortality.

1:45:06

Yeah. There's this a wonderful book that had a great influence on me called the denial of death by Ernest Becker.

1:45:12

And when you are aware of the ways in which our mortality influences our behaviors, it really does add a different slant, a different kind of color to the interpretation of human behavior.

1:45:29

Yeah. It's funny that that book had a big influence on me as well, and a terror management theory.

1:45:37

And I, again, from an engineering perspective, I don't know how many people that book influenced because I talked to people about the fear of death and it doesn't seem to be that fundamental to their experience.

1:45:51

And I don't think on the surface, it's fundamental to my experience, but it seems like an awfully in terms of talking about models and string theory and theories, in terms of theories of this macro experience of human life, it seems like a heck of a good theory that the fear of death is at the kind of, is the warm at the core.

1:46:10

Yes. Well, I mean, and the terror management theory is that you make reference to, I mean, the, this is a group of, you know, psychologists, social psychologists who devise these very clever experiments, real-world experiments with real people where you can directly measure the hidden influence of the recognition of our own mortality.

1:46:32

I mean, they've done these experiments where they have group of people, a group of people B and the only difference between the two groups is that group B, they somehow reminded them in some subtle way of their own mortality.

1:46:43

Sometimes it's nothing more than interviewing them with a funeral home across the street, you know, an influence it's there, but it's, but it's selling, you don't even think you'd take note of, and they can find measurable effects that differentiate the two groups to a high degree of statistical significance and how they respond to certain challenges or certain kinds of questions that shows a direct influence of the reminder of their own mortality.

1:47:11

And I've read a number of these studies and they are really convincing.

1:47:16

And so, yeah, I would say that the reason why so many people would say that yeah, fear of mortality, it's not front and center in my worldview.

1:47:27

Yeah. I don't really think about it. My, it doesn't really matter too much.

1:47:29

The reason why they're able to say that is because this thing called culture has emerged over the course of the last 10,000 years.

1:47:36

And part of the role of culture is to give us a means of not thinking about our mortality all the time of not living in terror of the inevitable end, which faces us all.

1:47:47

So it's completely understandable that that's the response because that's what culture is at least in part for The

1:47:54

least possible that the fear of death, the terror of your mortality is the creative force that created all of the things around us at this human civilization.

1:48:06

And I think about from an engineering perspective, this is where I lose all of my robotics colleagues is I feel like if you want to create intelligence, you have to also engineer in some kind of echoes of this kind of fear of, you know, fear is such a complicated word, but it's kind of like a scarcity, a scarcity of time, a scarcity of resources that creates a kind of anxiety like deadlines, get you to do stuff.

1:48:40

And there's something almost fundamental to that in terms of a human experience.

1:48:47

It's an interesting thought. So you're basically in order to create a kind of structure that mirrors what we call consciousness, you better have that structure confront the same kinds of issues and terrorism.

1:49:07

We do consciousness and suffering only makes sense in the context of death.

1:49:10

If you want to, I feel like if you want to fit into human society, if you, if you're a robot, if you want to fit into human society, you better have the same kind of existential dread the same kind of fear of mortality.

1:49:26

Otherwise you're not going to fit in.

1:49:27

It

1:49:27

might

1:49:27

be,

1:49:27

it

1:49:27

might

1:49:27

be

1:49:27

wild,

1:49:27

but

1:49:27

it's

1:49:27

at

1:49:27

least

1:49:27

like

1:49:27

we're

1:49:27

talking

1:49:27

about

1:49:27

all

1:49:27

the

1:49:27

theories

1:49:27

that

1:49:27

are

1:49:27

at

1:49:27

least

1:49:27

worth

1:49:38

consideration. I think that's a really powerful one.

1:49:40

And definitely one is resonated with me and definitely seems to capture something beautifully, like real about the human condition.

1:49:55

And I wonder it's of course sucks to think that we need death to appreciate life, but that's just maybe the way it is.

1:50:09

Well, it's interesting if this robotic or artificially intelligent system understands the world and understands the second law of thermodynamics and entropy, even in artificial intelligence will realize that even if its parts are really robust, ultimately it will disintegrate.

1:50:28

Yeah. I mean, so the timescales may be different, but in a way, when you think about it, it doesn't matter once you know that you are mortal in the sense that you are not eternal, the timescale hardly matters because it's, it's either the whole thing or not because on the scales of eternity, any finite duration, however large is effectively zero on the scales of eternity.

1:50:50

And so maybe it won't be so hard for an artificial system to feel that sense of mortality, because it will recognize the underlying physical laws and recognizes its own finances.

1:51:04

And then it'll be us and robots drinking beers, looking up at the stars and just, you know, having a good laugh in all of the whole thing.

1:51:16

Yeah.

1:51:16

I

1:51:16

think

1:51:16

that's

1:51:16

a

1:51:16

pretty

1:51:16

good

1:51:16

way

1:51:16

to

1:51:16

end

1:51:16

it

1:51:16

talking

1:51:16

about

1:51:16

the

1:51:16

fear

1:51:16

of

1:51:22

death. We started talking about the meaning of life and ended on the fear of death.

1:51:26

Brian's just an incredible calm I've really, really enjoyed.

1:51:30

It has been a long time coming. I'm a huge fan of your work, a huge fan of your writing.

1:51:34

Thanks for talking neighbor. Thank you.

1:51:36

Thanks for listening to this conversation with Brian Green, to support this podcast, please check out our sponsors in the description.

1:51:43

And now let me leave you with some words from bill Bryson.

1:51:47

Physics is really nothing more than a search for ultimate simplicity, but so far, all we have is a kind of elegant messiness.

1:51:57

Thank you for listening and hope to see you next time.

1:52:01

The following is a conversation with Brian Green, theoretical physicist at Columbia and author of many amazing books on physics, including his latest until the end of time, mind following is a conversation with Brian Green, 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. And now a quick few second summary of the sponsors. Check them out in the description is the best way to support this podcast. First is wine. My wine of my wine of choice. Second is Blinkist the Second Blinkist. The app. I used to read summaries of I used to read summaries of books. Third is element my go-to electrolyte drink mix fourth is better help and online therapy Third is Element. My go to electrolyte drink mix. Fourth is BetterHelp. An online therapy service. And fifth, is NI, a company that helps engineers solve the world's toughest problems. 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Other exclusions may apply. Please enjoy wines please enjoy wines responsibly. This This show is also brought to you by show is also brought to you Blinkist, my favorite app for learning new things. Blinkist takes the key ideas from thousands of non-fiction books and condenses them down into just 15 minutes that you can read or listen Blinkist, takes the key ideas from thousands of non fiction books and condenses them down into just fifteen minutes that you can read or listen to. My recommendation here are endless. Maybe the big books that pop to mind are Sapiens, meditations, the Marcus Aurelius, beginning with affinity by David Deutsch. Obviously a, I love that book and blinkers does a great job of summarizing Obviously, I I love that book, and does a great job of summarizing it. The Snowden book is on The Snowden book is on there. I mean the list goes on and I mean, the list goes on and on. I enjoy using blinkist to remind me of the core ideas and the books I've read. But I also use it to help me select the books that I'm going read in the future. Go to dot com slash LEX to start your free seven day trial and get twenty five percent off of a Blinkist premium membership. That's blinkist.com/lex spelled B L I N K I S T That's Blinkist dot com slash LEX spelled Blinkist dot com slash LEX. This This episode is also brought to you by element electrolyte drink mix spelled L M N T to do low carb diets episode is also brought to you by Element Electrolike Spelled LMNT. To do low carb diets correctly, I think the number one thing you have to get right is electrolyte. Specifically sodium, potassium, and magnesium. Element is my go to drink. I don't know how many I drink a day, but it's a lot it's I don't know how many I drink a day, but it's a lot. It's delicious. And like I said, it's essential to the kind of diet that I And like I said, it's essential to the kind of diet that practice. So both the intermittent fasting part of it and also the, the Quito or the carnivore part of So both the intermittent fasting part of it and also the the keto or the carnivore part of it. And honestly, it's kind of And honestly, it's kinda magic how much of a difference electrolytes make in a diet? So they called the keto So they call the flu. So if you're not feeling well, getting the right amount of salt and water in your system, it's just, it's So if you're not feeling well, getting the right amount of salt and water, in your system. It's just it's incredible how much of a difference that makes. Olympians use it? Tech people use Tech people use it. I swear by this stuff, try it at I swear by this stuff. Try it at drink element dot com slash LEX. That's drink element t dot com slash lex. This episode is also brought to you by better help spelled H E L P episode is also brought to you by BetterHelp, spelled HELP help. They figure out what you need and match you with a licensed professional therapist and under 48 hours, when I was young, I've dreamed about being a They figure out what you need and match it with a licensed professional therapist in under forty eight hours. When I was young, I've dreamed about being a psychiatrist. I was curious about the human mind, and I thought one of the best ways, practically speaking to explore the human mind is by interacting with individual people and diving together deep into their was curious about the human mind and I thought one of the best ways practically speaking to explore the human mind is by interacting with individual people and diving together deep into their mind. I got a little bit disillusioned by psychiatry as a discipline because drugs became such a big part of that field, basically prescription drugs. But nevertheless, talk therapy is still part of that field. And as the thing I really believe is the thing I really believe in. So I definitely think that should be part of the tools you use in your life is a therapy, but our help, I think is a definitely a great option to consider because it's easy, private, affordable, and available So I definitely think that should be part of the tools you use in your life. Is therapy. BetterHelp, I think, is definitely a great option to consider because it's easy, private, affordable, and available worldwide. Check them out a better them out at betterhelp dot com slash LEX. That's betterhelp dot com slash flex. This show is also brought to you by an I formerly known as national show is also brought to you NI. Formally known as national instruments. And I is a company that has been helping engineers to solve the world's toughest challenges for forty years. Their model. Probably one of my favorite models for company is engineer ambitiously. They have a podcast called the testing 123, They have amazing articles at n I dot com slash perspectives covering engineers and innovators, and they emphasize the power of failure through testing. So fail often and fast in the beginning to figure out what the problems are you can solve them before you deploy the system. That is engineering. That is what I love about engineering is deeply That is what I love upon engineering RSS deeply honest. You're confronting the realities, the physics of nature. Engineered ambitiously with NI I at n I dot com slashperspectives. That's n I dot com slash prospectives. This is LEX Friedman podcast, and here is my conversation with Brian Queen. In your most recent book, until the end of time, you quote Bertrand Russell from a debate he had about God in nineteen forty eight. He says, quote, so far scientific evidence goes, the universe has crawled by slow stages to somewhat pitiful result. On this earth and is going to crawl by still more pitiful stages to a condition of universal death. If this is to be taken as evidence of purpose, I can only say that the purpose is one that does not appeal to me. I see no reason therefore to believe in any sort of god. That's quite a depressing statement. As you say, this is a bleak outlook on our universe and the emergence of human consciousness. So let me ask what is the more hopeful perspective to take on the story? Well, I think the more hopeful perspective is to more fully under Dan, what was driving Brians Russel to this perspective? And then 25 see it, within a broader context. And, really, that's in some sense what what my book until the end of time is all about. But in brief, I would say that there's a lot of truth to what Brians Russel 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 is gonna wither decay, fall apart. Yeah. That's true. Second law of thermodynamics establishes that this order entropy, an aggregate is always on the rise and that is indeed interpretable as disintegration and destruction over vision long time scales. But my view is when you recognize how special that makes us that we are these squeezingly ordered configurations of particles that only will last for blink of an eye in cosmological time like terms. The fact that we're Brians we can do what we do. To me, that's just really something that inspires gratitude and wonder and and a sense of of deep purpose by virtue of being these unique collections of entities that happen to rise up, look around, and try to figure out where we Brians what the heck we should do with our time. So it's not that would agree with Brians 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 maybe we'll skip around a bit, let me ask the biggest possible question then you said purpose. So what's the meaning of it all then? Is is there a meaning to life that we can take from this from this brief emergence of complexity that arises from simple things and then goes into a a heat death that is once again returns to simple things as the march of the second law of thermodynamics goes on. Well, I I think there is, but I don't think it's a universal think there is, but I don't think it's a universal answer. And so 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 compassionate ship. I mean, NI people put forward different ways of taking this question on. And there is no one right and So 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, but 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 10, 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 25 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 And however much that may sound like a hallmark card, this really is the deep lesson of of physics and science more generally over the past few hundred years. Well, there's some level where you can objectively say that whatever we got going on here, it's kind of peculiar. It's kind of special in in in in in terms of LEX. And maybe you can even begin to measure it and, like, come up with metrics where whatever we got going 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 universe. The the observable part that we can see with our tools. I mean, so I have to ask as you describing your book once again, Shored in girl wrote the book his life based on a few lectures he gave in nineteen forty four. 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? Yeah. It's a tough question. I asked that question even to Richard Dockkins once. And I already have my preconceived notion, which he pretty much confirmed, which is If one could give an answer to that question that allowed you to sort of draw a line in the sand, between the not living and the living, then perhaps we would have the insight that we yearn for in trying to say what is so special about life, But the fact of the matter is it's a continuum. There's a continuum from the things that we would typically call nonliving in animit 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 were able to do, but I would agree with you. It's deeply peculiar. It may, in fact, be NI, but it may not. It could be that the universe is such that under fairly typical conditions, a star That's a well ordered source of low entropy energy. That's what the sun is. Together with a planet being bathed by that low entropy energy together with a surface that has enough of the wrong constituents that we record nies are fairly commonplace, result of supernova explosions, where 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? It's going up hopefully in Right? It's going up hopefully in December. Mhmm. And one of the one of the goals of that mission is to look at atmospheres around distant planets and perhaps come to some sense of how special or not life or life 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 is the hardest if you were like a a betting man, like which part is the hardest to make happen? Is it the origin of life? Again, we haven't drawn the line where as you say the line between a rock and a rabbit. That part is 25 complex Brians, like multicellular Brians? Is it crawling out of the ocean where the fish somehow figured out how to crawl around? Is it then the RSS homo sapiens as we like to think of ourselves special and intelligent? Or is it Somewhere in between is you also talk about, again, very hard to know at which point this consciousness yeah, emerge. Like, if you if you were to sort of took a 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 see if we're gonna go all the way to conscious beings like ourselves. I would put it at the onset of conscious this, 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 creature 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 conscious RSS, I think that's probably the hardest part because look, take earth and recognize that weren't for, you know, some singular event sixty five million years ago where this large rock slams into planet earth and wipes out the dinosaur 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. We are a rare exception to that. And I really appreciate that you lean into some of these unanswerable questions for me today. But the so you think about consciousness, not as, like, a face shift, the binary zero one. You was a continuum that humans somehow are maybe some of the most conscious beings on earth. So you're So I mean, people will dispute I mean, people will dispute that. Yes. I mean, well And it's a very hard argument. People dispute that. Rocks probably will stay quiet on the matter. Maybe not. Right. For the moment. They're waiting for their opportunity. But but IIII agree that look, even when you and I look at each other, I am not fully convinced -- Mhmm. -- that you're a conscious being. right. I mean, I think that you are onto I mean, I think that you are. Onto me. I mean, your behavior is such that that's the best ex pollination for what's going But of course, we're all in the position of only having direct awareness of our own conscious Brians. And therefore, When it comes to other creatures in the world, we're in a similar state of ignorance regarding what's actually happening inside of their head if they have a head. And so it's hard to know how singular we are. But I would say, based on the best available data and the best explanations we can make, yeah, there is something special about us. I don't think that there are fish walking around and, you know, coming up with, you know, existentialism. I don't know that there are, you know, dogs walk and around who've developed an understanding 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 25 name for this, the hard problem of consciousness. David Chalmers and others. As a physicist, I look out the world and I see it's particles governed by physical law. Look a name. Yeah. You know, we've got electrons. We've got quarks that come in various flavors and so forth. We have a list of ingredients that science has revealed. And we have a list of laws that seemingly govern those ingredients and and nowhere in there, is there even a hint that when you put those particles together in the right way, and in the world should turn on. And it's not only that there's no hint It's insane. I mean, it's ridiculous. How could it be that a thoughtless, passionless, emotionless, particle when grouped together with compatriots, somehow can yield something so deeply foreign to the nature of the ingredients themselves. So so answering that question, I 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 of It's an emergent thing that's like, oh, it's nice. It's like a nice little feature. Yeah. Well, I mean, when people use the phrase, hard problem. I mean, they mean somewhat technical sense that it's trying to explain something that seems fundamentally unavailable to third party objective analysis. Right? I'm the only one that can get inside my head, and I can tell you 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 on top of my head, but you don't have access to it. And the way that I And 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 where we look at the motion of the moon. Everybody can look. Everybody can measure it. We look at, you know, the properties of hydrogen when you shine lasers on 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 Mhmm. -- relative to the others. But I do think ultimately that the explanation will be as you recount, I think that a hundred years from now or maybe it's a thousand. It's hard to predict the timescale for elements, but I think we'll get to a place where we'll look back and kind of smile at those folks in the twentieth century and before 20 first 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 and however mysterious that feels right now I think for instance, when we start to build conscious systems, you know, things that, you know, you're more familiar with than I am. When we start to build these artificial systems, and those systems report to us, I'm feeling sad. Yeah, I'm feeling anxious. Yeah, there's a world going on inside here. I think the mystery of consciousness will just begin to evaporate. Well, Well, first of all, beautifully put, and I agree with you completely, just the way you said it, it will begin to 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 I've had them do emotion emotional type things, and it's immediate that exactly what you're saying. This kind of mystery of consciousness starts to evaporate, 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, that thing sure as heck looks conscious. You know, I feel like that way when I interact with a dog, I don't need to solve the problem of consciousness to to be able to interact and originally enjoy the experience with this other living being. Obviously, same thing with other humans. I don't need to fully understand it. And there there's some aspect. Maybe this is a little bit too engineering focus but there's some aspect in which it feels like 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. It's very useful. So put yourself in that world and to be able to describe the experience to others. Yeah. It could be just the social and the merch. Obviously, animals, the sort of more primitive animals might experience caution essence 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. Yeah. That resonates with my view as well. I mean, there's scientists maybe you've spoken to Michael Graziano from Princeton. Yeah. He 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 under relying 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, 25 feels like our minds and inter interworlds are just untethered, like floating somewhere in this gray matter inside of our heads. And the way I like the thing of it is like, look, you know, if if if if you're in a dark room, Brians, and I had blown the dark paint on my fingers. So all you saw is my fingers dancing around. There something mysterious how how could those fingers be doing that? And then you turn a light, 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 physical, chemical, biological way. And so 25 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 one day we will reveal that more And one day, we will reveal that more fully, and I think that 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 once we know how this thing works, Maybe we will no longer enjoy like this conversation. We'll seek other sources of enjoyment, but there's this is again from an engineering perspective. I wonder if the mystery is is an important component. Well, you know, there's have you ever seen there's this beautiful interview that Richard Feynman did, you know, great Nobel laureate physicist responsible for a lot of our understanding of quantum cans, quantum fields 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, it the beauty goes away. Yeah. You know, the wonder of it goes away. And he was emphasizing in his response to that. He's like, NI. That's not the right way of thinking about it. He says, look, when I look at it, 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. He says, that only augments my wonder. It only augments my experience. It doesn't flatten it or or take away from it. So I should Right. Yeah. Well, I should've take that as bit of a of a motto in some sense that that there is a wonder that comes from a kind of ignorance. And I don't mean that in 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 and and deep knowing. And I think that kind of wonder has its own special character that in some ways can be more gratifying? I hope he's I hope he's right. I hope you're right. And but there's also I remember he said something about, like, an like, size as an onion or something like that. You can peel back. You can't keep 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 a mystery. But I think it's also different than, you know, I don't think you can analogize, say, to a magician. Right? A magician. It does some trick. You learn how it sounds like, oh my god. That was that's ridiculous when you find it. But but nature is perhaps the best magician if you wanna 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 one 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 when the curtain is pulled back, then what happens in other circumstances where it does flatten it completely Yeah. It's very possible than saying physics that we arrive at a theory of everything that unifies the laws of physics as a very strong understanding of the Fed book of reality, even like from the very for the big bang to to today, it's possible that that understanding is only going to elevate our appreciation of this whole thing. Yeah. I think it will. I think it will. I mean, NI think it has it has so far But the other side of it, which you 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 one day will close the book on nature's ingredients and the fundamental laws. Mhmm. Now that can't prove that, maybe it goes on forever smaller and smaller, maybe they're deeper and deeper laws. But I I don't think so. think that there's going to be a collection of ingredients and a collection of basic laws. That chapter will close. Mhmm. But it's one chapter. Now we take that knowledge and we try to understand how the world builds the structures that it does. You know, from planets 25 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 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 understand grows larger and larger. Do you have a hope that we solve that theory of everything puzzle in, in the next few you have a hope that we solve that theory of everything puzzle in in the next few decades? So there's been a a bunch of attempts from string theory to all all kinds of attempts at trying to solve quantum gravity or basically come up with theory for quantum gravity. There's a lot of complexities to this. One, for experimental validation, you have to observe facts 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. Do you have a hope or are we hopelessly stuck. Well, I have to have to have a hope. 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 RSS the phrase quantum gravity. I'm not a great fan of the theory of everything phrases because it does make other scientists feel like if they're not working on this, what are they working on men's like, you know, there's not much left when you're talking about theory of everything. Biology is just small detail to figure out. Yeah. So 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 one not get fired up about maybe contributing something to that journey? And so we've been on this. You know, I've been on this for thirty years since I was a student. We we have made progress. We do have ideas. You mentioned string theory is one possible scenario, it's not stuck. Strength theory is a vibrant field of research that is making incredible progress But we've not made progress on this issue of experimental verification validation, which as you know, is 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 eighties when I was, you know, a wild bright eyed kid trying to make headway work in eighteen hours a day and this sort of stuff. Obviously, yep, I By twenty one, yeah, we're gonna know whether it's right or wrong, but make contact. I would have said, look, there may be certain mathematical puzzles that we've got to work out, but we'll know enough. To make contact with experiment that has not happened. On the other hand, if you would have interviewed me back then and asked me, will we be able to talk about detail qualities of black holes and understand them at the the level of detail that we actually I I would have said, NI. I 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. Don't think we're gonna have that yet. We do. Mhmm. So it's just say you don't know where the progress is going to happen, but yes, I do hold out. Hope that maybe before I move on to wherever, I don't think there is an after, but I, I would love before I leave this earth to, to know the answer, but you know, science and the universe, it's not about pleasing any hope that maybe before I move on to wherever. I don't think there is an after, but I I would love before I leave this earth to to know the answer. But, you know, science in the universe, it's not about pleasing any individual. It is what it is. 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 outside perspective currently at the theoretical physics community. String theory is the theory was as a theory has been very popular for for a few decades. But it has recently fallen out of favor or at least there's been, like, you know, it became more popular to kinda ask the question a string theory really the answer. Where do you fall on this? Like, how do you make sense of this puzzle? Why do you think it has fallen out of favor. RSS. I I would actually challenge this statement. That's fallen out of that's fallen out of favor. I would say that any field of research when it's new and it's the the bright shiny bicycle that no one has yet seen on that block. Yeah. It's gonna attract 10. And the news outlets are gonna cover it, and students are gonna flock to it? Sure. But as a as a field matures, it does shed those qualities because it's no longer as novel as it was when it was first introduced thirty, forty years ago. But you need to judge it by a different standard. You need to judge it by is it making progress on foundational issues deepening our understanding of the subject. And by that measure, string theory is is is scoring in 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 theory is myself included, are are very sober about the theory. It it has the tremendous progress that it had thirty, forty years ago that hasn't gone away, but we've become better equipped at assessing the long journey ahead. Mhmm. And that was something that we weren't particularly good at back, say, in the eighties. Look, when I was just starting out in the field, there was a sense of physics is about to end. Stream theory is about to be the beyond and all final unify Brians that will bring this chapter to a close. Now I have to say, I was more the younger physicists says 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 -- Yeah. -- that was gonna be a long long journey. I think people like, you know, John Schwartz, one of the founders of string theory Michael Green, no relation to me founders of the theory. Edward Witten, you know, one of the main people driving the theory back then and today. I think they knew that we were in for a long haul. And and that's the nature of science quick hits that resolve everything few and far between. And so if you were in for the quick solution to the big questions of the world, then you would have been disappointed. And I think there were people who were disappointed and then moved on and work on other subjects. If we were 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 think string theory has been a rich source of of material that has kept so many people deeply engaged and moving the frontier forward. There's a A few qualities about string theory, which are 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 25 you as most beautiful boss drink theory? Well, what what attracted me to the theory at the outset. Set beyond it's putting grabbing quantum mechanics together, which I think is it's true claim to fame. At least on paper, it's able to do that. What attracted me to the theater was the fact that it requires extra dimensions space. Mhmm. And this was an idea that in trigued me in a in a very deep way even before I really understood what it meant. I somehow had. I mean, talk about sort of the emotional part of consciousness and the cognitive had I mean, talk about sort of the emotional part of consciousness and the cognitive part, and some perhaps called Strange in some strange emotional way, I was enamored with Einstein's general relativity, the idea of curve space in time before I really knew what it meant. It just spoke to me. don't know how else to say it. Mhmm. And then when I subsequently learned that people had thought about more dimensions of space than we can see and how those extra dimensions would be vital to a deep understanding of the things that we do see in this world, 456 dimensions might explain why there are certain forces and particles and how they behave. 25 this was like amazing. Totally amazing. And then when I learned that string theory embraced all these ideas, embraced the general theory of relativity, embraced quantum mechanics embraced the possibility of extra dimensions, then I was then I was hooked. And so when I was a graduate student, we would just spend hours. But we, I mean, a couple of other graduate students and myself who had to have sort of worked really well together. Is it Oxford in England? We would we would work these enormous numbers of hours a day trying to understand the shapes of these extra dimensions. The geometry of them what those geometrical shapes for the extra dimensions would imply for things that we see in the world around RSS. And it was a it was a heavy heavy time. And and that kind of excitement has sort of filtered through over the decades. But I'd say that's really the the part of the theory that I think really hooked me most strongly. How are we supposed to think about those extra dimensions? I was supposed to imagine actual physical reality? Or RSS this more in the space of mathematics that allows you to sort of come up with tricks to describe the four dimensional reality that we more more directly perceive. NI one really knows the answer, of RSS, but I take the most straightforward approach to string theory, you really are imagining that these dimensions are there. They're real. I mean, just as you would say that the three space dimensions around us, you know, left right, back, forth, up, down. Yeah, we they're real. They're here. We are immersed within those dimensions. These other dimensions are as real as these with the one difference being their shape and their size differs from the shape and size of the dimensions that we have direct access to through through human experience. And one approach imagines that these extra dimensions are tightly coils up -- Mhmm. -- curled up, crushed together, if you will, into a beautiful, geometrical form that's all around RSS, but just too small for us to detect whether our eyes too small for us to detect even with the most powerful equipment that we have. Mhmm. Nevertheless, according to the mathematics, the size and the shape of those extra dimensions leaves an imprint in the world that we do have access to. So one of the ways that we have hoped yet to achieve to make contact with experimental physics is to see a signature of those extra dimensions in places like the Large Hadron Collider in Geneva, Switzerland. And it hasn't happened yet. doesn't mean it won't happen, but that would be a stunning moment in the history of the species if data that we acquired in these dimensions gives us kind of incontrovertible evidence that these dimensions are not the only dimensions. I mean, how mind blowing would would that be? So with a large head around collider, it would be something in the movement of particles or also the gravitational waves potentially be a place where you can detect signs and multi dimensions like with some old LIGO but much more accurate. In principle, all of these can In in principle, all of these can work. So one of the experiments that we had high hopes for. But by high hopes, I'm actually exaggerating. One of the experiments that we imagined might in the best of all circumstances yield some insight. We weren't with baited breath waiting for the result. We knew it was a long shot. When you slam protons together at very high speed as large hadron collider, if there are these x dimensions. And if they have the right form, and that's a hypothesis that may not be correct. But when the proteins collide, they can create debris. Energetic debris that can in some sense leave our dimensions and insert itself into the other dimensions. And the way you'd recognize that is there'd be more energy before the collision than after the collision because the debris would have taken energy away from the place where our detectors can detect Mhmm. So that's that's one real concrete way that you could find evidence for extra dimensions. But yeah, since extra dimensions are of space, and gravity is something that exists within, in fact, is associated with the shape of space. Gravitational waves in principle can provide a kind of, you know, cat scan of of the extra dimensions if you had sufficient control over those processes. We don't yet, perhaps one day we will. Does it make you sad a little bit or maybe looking out into the future? You mentioned Ed Witten that no noble prizes have been given yet related to string theory? Do you think they will be? Do you think you have to have experimental validation? Or can a Nobel Prize be given? Which I don't it being given for quite a long time for purely sort of theoretical contribution. Yeah. It's certainly as a matter of historical precedent has been the case that those who win the prize have established, investigated, illuminated, a demonstrably real quality of the world. Mhmm. So gravitational waves. The prize was awarded after they were detected, not not the mathematics of it, but the actual detection -- Mhmm. -- of it. You know, the hoax particle. You know, it was an idea that came from the nineteen sixties, Peter Higgs and others in fact, and it wasn't until twenty twelve, on July fourth, when the announcement came that this protocol had been detected, the large Hadron Collider, that people viewed it as eligible for the Nobel Prize. The idea was there, the math was there, but you needed to confirm it, indeed, the prize ultimately was awarded. So I'm not surprised. Mhmm. In fact, I would have been surprised if Inoval Prize have been awarded in the arena of string theory because it's far too speculative right now. It's far too hypothetical. In fact, I am sympathetic to the view that it really shouldn't be called string theory. It degrades the word theory. Mhmm. Because theory in science, of course, means the best available explanation the things that we observe in the world, the things that we measure in experiments about the world, and string theory does not do that, at least not yet. So it really should be the string hypothesis, So it really should be the string hypothesis. right? We're at an earlier stage of development and that's not the kind of thing that Nobel prizes should be awarded Right? We're at an earlier stage of development. And not the kind of thing that Nobel Prize should be awarded for. What do think about the critics out there, Peter White, he's from Columbia 25 Sabine, Harvastat, or is that a healthy thing? Or should we sort of focus on sort of the optimism of of these hypotheses. Yeah. It's actually a good way that you frame it because I'm always somewhat repelled by views of the world that start from the negative. Try to cut down an idea. Try to say that's the wrong way of thinking about things. And so on, I'm much more drawn, maybe because I'm an optimist. I don't know. I'm I'm much more drawn to those who go out into the world with new ideas. And and don't try to cut down one idea, but rather present another one. That might be better. Mhmm. And so you make the first idea maybe string the irrelevant because you've come up with the the better approach to the world. So do I think it's healthy look? I think having a wide range of views and perspectives is generally a healthy thing. I think it's good to have arguments within a subject in order that you stay fresh and you stay focused on the things that matter. But in the end of the day, I think it's a more vital contribution to give us something new rather than to criticize something that's there. Yeah. I'm totally with you. But it could be just nature being an optimist. I and also just a a level of engineering. If there's it it it helps nobody by criticizing the the rocket that somebody else built. Just build a bigger, cheaper, better rocket. Right. Exactly. Yeah. And that seems to be how human cellization can progress effectively. We we've mentioned the second law of thermodynamics. I gotta ask you about time. Yeah. And do you, do you think of time as emergent or fundamental to our And Do you do you think of time as emergent or fundamental to our universe? I like to think of it as emergent. I don't have a solid reason for that perspective. I have a lot of hints of reasons that some of which come out of string theory and quantum gravity that perhaps would be worth talking about. But what I would say is time is the most familiar quality of experience because there's nothing that takes place. It doesn't take place. Within an interval of time, and yet at the same time, it is perhaps the most mysterious quality of the world so it's a wonderful confluence of the familiar and the deeply mysterious all in one little package. If you were ask me, what is time? I don't don't really know. I don't think anybody does. I I can say, what time gives us It allows us the language for talking about change. It allows us to envision the events of the universe being spread out in this temporal timeline, and then that way allows us to see the patterns that unfold within time. I mean, time allows us the structure in the organization to think about things in that kind of a progression. But what actually is it? I I don't really know, and that's so strange because we can measure it. Right? I mean, there are laboratories in the world that measure this thing called time to spectacular precision. But, you know, if you go up to the folks and say, like, what is it that you're actually measuring? I don't know that they can really articulate the kind of answer that you would expect from those who are engineering a device that can measure something called time to that level of precision. So it's a very curious combination. What do you make of the one way feeling of causality? Like this causality a a thing or is that just a human story that we put on top of this emergent phenomena of time. don't know. I can give you my my guess and my intuition about it. I I do think that at the macroscopic level. If we're talking about sort of the human experience of time, I do think at the macroscopic level, there is a fundamental notion of causality that does emerge from a starting point that may not have causality built in. So I certainly would allow that at the deepest description of reality when we finally have that on the table, we may not see causality directly at that fundamental level. Mhmm. But I do believe that we will understand how to go from that fundamental level to a world where at the macroscopic level, there is this notion of a causes b. A notion that Einstein deeply embraced in his specialty creativity where he showed the time as qualities that we wouldn't expect based on experience. You and I, if we move relative To each other, our clocks tick off time at different rate in our clocks is just a means of measuring this thing called to each other, our clocks tick off time at different rate, and our clocks is just a means of measuring this thing called time. So this is really time that we're talking about. Time for you and time for me different if we're in relative motion, he then shows in the general theory of relativity that if we're experiencing different gravity, different gravitational fields or more precisely different gravitational 10. Time will collapse for us at different rates. These are things that are astoundingly strange that give rise to a scientific notion of time travel. Okay? So this is this is how far Einstein took us in wiping away the old understanding of time and injecting a new understanding of its quality. So So there's so much about time that's counterintuitive, but I do not think that we're ever going to wipe away causality at the mic, macro sky. At the at the macro I mean, there's so many interesting things at the macroscopic level that may only exist at the macroscopic level. Yeah. Like, we we already talked about conscious that that very welcome you wanna think. You mentioned time travel. So, I mean, according to Einstein, And in in general, what types of travel do you think our physical universe allows? Well, certainly allows time travel to the future. And I'm not talking about the silly thing that you and I are now going into the future. Second by second by second, I'm talking about really the diversion that you see in Hollywood, at least in terms of its net effect, whereby an individual can follow an Einsteinian strategy and propel themselves into the future in some sense more quickly. Mhmm. So if if I wanted to see what's happening on planet Earth one million years from now, Einstein tells me how to get one million years from now. Build a ship. I gotta turn to guys, you know, who know how to build stuff. I can't do it like you. Build ship that can go out into the universe near the speed of light. Mhmm. Turn around and come back. Let's say it's a six month journey out, a six month journey Brians. Einstein tells me how fast I need to travel, how close to the speed of light I need go that when I step out of my ship, it will now be one million years into the future on planet Earth. And this is not a controversial statement. right? This is not something where there's differences of opinion in the scientific This is not something where there's differences of opinion in the scientific community. Any scientist who knows anything about what Einstein taught us agrees with what I just said. It's it's commonplace. It's bread and butter physics. And so that kind of travel to the future is absolutely allowed by the laws of physics, their engineering challenges, their their technological challenges close to the speed of light part. Yeah. Yeah. And they're they're even biological challenges. Right? They're g forces that you're gonna experience. it. You know, so there's all sorts of stuff embedded in this, but those I will call the details and those details, not withstanding the universe allows this kind of travel to the know, so there's all sorts of stuff embedded in this. But those, I will call the details. And those details, notwithstanding, the universe allows this kind of travel to the future. And if I could pause real quick, You can also, at the macro level, would biology extend the human lifespan 25 do a kind of travel forward in time? If you expand how long we live -- Yep. -- that's a way 25, from a perspective and of an observer, conscious observer that as a human being, you're essentially traveling forward in time by allowing yourself to live long enough to see the thing. Yes. So that's in the space of So that's in the space of biology. What about traveling back in time? Yeah. That's the that is a natural next question, especially if you are if you're doing you're going on one of these journeys, is it a one way journey? Yeah. Can you can you come back? And the the physics community doesn't speak with a unified voice on this as yet. But I would say that the dominant perspective is that you cannot get back. Now, having said that, there are proposals that serious people have written papers on regarding hypothetical ways in which you could travel to the past. And we've seen some of these. Again, Hollywood loves to take the most sexy ideas of physics and build narratives around them, this idea of a wormhole, like Jody Foster in contact went wormhole. Deep Space nine star. I'm sure there many other examples where these ideas that I've probably never even seen. But with wormholes, there's at least a proposal of how you could take a wormhole tunnel through spacetime, manipulate the openings of the wormhole in such a way that the openings are no longer synchronous. They are out of sync relative to each other, which would mean one's ahead and one's behind, which means if you go through one direction, you travel to the future, if you go back, you travel to the past. Now we don't know if there are wormholes that were possible according to Einstein. Correct. They are possible according to Einstein. But even Einstein was very quick to say, just because my math allows for something because I mean, it's real. I mean, he famously didn't even believe in black holes. Yeah. Didn't believe in the big bang. Right? And yet the big the the black hole issue has really been settled. Now we have radio telescopic photographs of the Black Hole in m eighty seven. It was in newspapers around the world just a couple of years ago. So so it's just to say that just because it's in Einstein's math, it doesn't mean it's real. But, yes, it is the case that wormholes are allowed by Einstein's equation. That in principle, you can imagine, you know, putting electric charges on the openings of the wall, allowing you to tow them around in a manner that could yield this temporal asymmetry between them. Maybe you toe one of the mouths to the edge of a black hole. In principle, you can do this. Slowing down the passage of time near that black hole. And then when you bring it back, it will be well out of sync with the other opening and therefore could be a significant temporal gap -- Mhmm. -- between one and the other. But people who studied this in more detail question, could you ever keep a wormhole open? To me, it does exist. Could you ever travel through a wormhole? Or would there be requirement to some kind of exotic matter to prop it open that perhaps doesn't exist. So there are NI, many issues that people have raised. And I would say that the general sentiment is that it's unlikely that this kind of scenario is going to survive our deeper understanding of physics when we finally have it. But that doesn't mean that the door is closed. So maybe it's a small possibility that this could one day if we were. That's such an interesting way to put it it will not this kind of scenario will not survive deep understanding of physics. It's an interesting way to put it because makes you wonder what kind of scenarios will be created by our deep or understand of physics. Maybe sorry to go crazy for a second. But if you have, like, the panpsychism idea that consciousness permeates all matter, maybe traveling in that whatever laws of physics, consciousness operates under or something like that. In that view, universe if we somehow are able to understand that part. Maybe traveling is super easy. Yeah. Yeah. It does not follow the trains at the speed of light, something like this. Yeah. So look, I have I have a definite degree of sympathy with a possibility that consciousness might be more than what we described earlier is just the byproduct of mindless articles. You just made the rock happy. Exactly. You know, so so it it isn't the approach that feels to me the the most likely, but I I see the logic. If you've got the puzzle, how to mindless particles build mind, one resolution might be, the particles are not mindless. The particles have some kind of proto conscious quality. So there's there's something appealing about that straightforward solution to the puzzle And if that's the case, if we do live in a pancyclist world where there a degree of consciousness residing in everything in the world around us, then yes, I do think some interesting possibilities might emerge where maybe there's a way of communing with physical reality in a in a deeper way than we have so far. I mean, we as human beings, a vital part of our existence is human to human communication. Contact. We live in social groups, and that's what it's allowed us to get to the place where we've gotten. Imagine that we have long missed that there's other consciousness out there -- Mhmm. -- and some kind of relationship or communion with that larger conscious possibility would take us to a different place. Now, do I do I buy into this yet? I don't. I don't see any evidence for it, but do I have an open mind and allow for the possibility? In the future? Yeah, I do. So if that's not the case and you have these simple particles that at the macro level emerges some interesting stuff like consciousness, another thing you write about in the, on till the end of time book is the thing that it seems to emerge at the macro level is the feeling like, like there's a freewill, like we decide to do stuff and you have a really interesting take here, which is no, there's not a freewill So if that's not the case and you have these simple particles that at the macro level emerges some interesting stuff like consciousness. Another thing you're right about in the on the end of time book is the the the thing that it seems to emerge at the macro level is the feeling. Like, that like, there's a free will. Like, we decide to do stuff. And you have a really interesting take here, which is, no, there's not a free will. Well, out. I'm just going to speak for I'm just gonna speak for you and then you shouldn't correct me. NI, there's not a free will, but there is an experience of freedom. Yeah. Yeah. Can which III really love. So where does the experience where does freedom come from if we don't have any kind of physics based free will. Yeah. And and so the idea follows naturally from all that we've been talking about. Let's make the assumption. That all there is in the physical universe is stuff governed by laws. We may not have those laws. We may may not know what the fundamental stuff is yet. But everything we know in science points in the direction that it's physical stuff governed by universal laws. And that being the case or that being the assumption, then you come to a particular collection of those ingredients called the human Brians. And that human being has particles that are fully governed by physical law. And when you then recognize that every thought that we have, every action that we undertake is just the motion of particles. When I'm thinking thoughts right now, of course, at this level of scription. It is the motion of particles cascading down various neurons inside of my head and so on, and every single one of those motions. Collectively and individually is fully governed by these laws that we perhaps don't have yet. But we imagine one day we will, that leaves no opportunity for any kind of freedom to break free from the constraint of physical but we imagine one day we will. That leaves no opportunity for any kind of freedom to break free from the constraint of physical law. And that is the end of story. Mhmm. So the traditional intuitive notion of free will that we're the ultimate authors of our actions that we were the buck stops that there is no antecedent, that is the cause for our decided to go left or right choose vanilla or chocolate live or die, that intuitive sensation does not have a basis in our understanding of physical world. So that's the end of the free will of the traditional sort. But then your question is, what about this other kind of freedom I talk about? And the other kind of freedom, if you focus on intently, I think, is actually the true version of freedom that we feel. And that freedom is this. You look at inanimate objects in the world, rocks, bottles of water, but other, they have a very limited behavioral repertoire. Why their internal organization is too coarse for them to do very much. Right? You have to you try to have a conversation with a glass of water. You send sound waves, it doesn't do much. It may vibrate a little bit, but the repertoire of responses are incredibly limited. Mhmm. The difference between us and a rock or a bottle of water is that our inner organization by virtue of, Eons of evolution by natural selection, is so refined. So spectacularly ordered that we have a huge repertoire of behaviors that are finally attuned to stimuli from the external world. You asked me a question that's a stimulus and all of a sudden, these particle processes go into action and this is the result, this answer that I'm giving you. So the freedom that we have is not from the control of physical law. The freedom that we have is from the drained behavior that has long since governed inanimate objects, we are liberated from the limited behavioral repertoire of rocks and bottles of water to have this broad spectrum of responses. Do we pick them? We do not? Do we freely choose them? We do not. But yet we have them, and we can marvel at those behaviors. And that's the freedom that we have. The complexity and the breadth of that repertoire is is where the freedom of margin. Is there something to be said about emergence? I don't know if you know I've looked that much about objects that I seem to love doing more than anyone else, which is cellular talk. Yeah. Like, game of life type of stuff. There you know, from simple things, emerges beautiful LEX. Yes. And so that's that repertoire. It's like it seems if you have enough stuff. Just beautiful complexity emerges that sure heck to our human eyes looks Like, there's consciousness there. There's free will. There's little objects moving about and making decisions. I mean, all of that You could say it's anthropomorphization, but it sure a heck feels like their organisms making decisions What is that that emergence thing? Is that is that within the realm of physics to understand? Is it Is it within the realm of poetry? What because what is that, like, the clock systems emergences? What is that will that ever be understood by science? So here's here's the way that I think about it. So there are clearly qualities of the world that emerge on macroscopic scales, our sense of beauty, wonder consciousness, all of these kinds of it. So there are clearly qualities of the world that emerge on macroscopic excales -- Yes. -- our sense of beauty, wonder, consciousness, all these kinds of qualities, do I feel that they ultimately are explainable from the laws of physics do. There is nothing that's not ultimate ultimately explainable with the laws of physics from this physicalist perspective, which is what I take. So you got the particles, you got the laws, and you have things that emerge from the choreographed motions of those particles. But is that the best language for talking about these emergent qualities Usually not. If I was to take something even more mundane like a baseball flying through the air, if I was to describe it in terms of the quarks and the electrons, I'd give you this mountain of data with, you know, ten to the twenty eight particles and all of their coordinates and spaces function of the time. I hand you this mountain a day to be like, I don't know what this is. And then if you really were clever and looking, oh, it's a baseball. Just describe in the in the least economical way possible. It is much more useful and insightful to talk about the baseball finder. The air similarly, there are things at the macroscopic level like human experience and human emotion and human action and the sensation of free will that we undeniably all have even if it itself doesn't have a basis in our understanding of the physical world. It's useful to talk about things in this very human language. And so, yes, it's vital to talk about things in the poetic language of human experience, but do not lose sight of the fact than some people do. They say, oh, it's just an emergent phenomena. Don't lose out of the fact that emergent phenomena are emerging from this deeper understanding that comes from the reductionist account of physical law. And there's a lot of insight to come from that such as the freedom that you thought that you had, the freedom of will that you thought you had, it doesn't have a basis in that reductions account, so it's not real. So speaking of the poetry of human experience, you mentioned in the images of the black holes. How did it make you feel a few years ago when that first image came out? Truly amazing. A sense of I guess the feeling was both amazing and and there's a little sense of jealousy is not quite the right word. But a sense of longing. Yeah. I think that's a better word because here's a subject that started with Einstein back in nineteen fifteen writes down the equations of the general theory of relativity. And then there are scores of individuals over the decade. You know, starting with people like Karl Schwarzschild who analyze the equation, see the possibility of black holes. People develop these ideas, John Wheeler or all these great physics, It's still a hypothetical subject. It gets closer to reality through observations of the center of our LEX, stars whipping around in a manner that could only really be explained by there being a black hole in the center of our galaxy, but it was still indirect actually have a direct image that you can look at. What a beautiful narrative arc from the theoretical to the absolutely established And that's what we hope will happen with other areas for instance string theory. Right? I mean, holy mathematical subject at the outset and still pretty much a holy mathematical subject today. Yeah, do we long for that image? Where we can look at it and say, string. It's really amazing, you know. I mean, how thrilling. How thrilling to be part of that NI, to be part of that that step that moves things from the abstract to the concrete. Yeah. So it's like the image of the the early image of the DNA for example. But there is something special. So the problem with strings is they're NI. So it's harder to take a picture in the in in the following sense. When you think of a black hole, I mean, you have a swirl of, I guess, what is I I don't even know it's dust to go, whatever light creating on to the event Brians. And then there's darkness -- Yeah. -- center. And then you can you just imagine so that picture in particular I guess, it's a it's a gigantic black hole. So you just I mean, it's -- Yeah. -- barely a billion billions of times to master son. Yeah. So it's it's both exciting and terrifying. I mean, I don't I don't know where you fall in the special. I think it's exciting at first Like, the longer think about it, every time I think about it, the more terrifying it becomes. So it always starts exciting, and then it goes to terrifying. And both are feelings, very human feelings that I appreciate. It's like terrified awe -- Yeah. -- how it's still beautiful. That's it's a good way. And think I kinda share that that reaction because there is a way in which when you work on this subject, like all the time, I teach it, I teach about black holes. right? The equations on the Blackboard, the ideas reside in a very cognitive, I don't know, mathematical portion of the brain or at least for the equations on the blackboard. The ideas reside. In a very cognitive, I don't know, mathematical portion of the brain or at least for me. And it's only when you, like, sit down and it's quiet and you start to contemplate. Wait. Wait. Wait. This is just like a mathematical game. Mhmm. There are these monsters out there. Now I don't Not in a in a sense of I fear for my life, but it's a a sense of How extraordinary is this universe? And so it is breathtaking. How powerful nature is Yeah. How how tend powerful nature is. And so there is a deep sense of humility that I think this instills if you really allow the ideas to sink in. Well, I have to ask about the most stupendously powerful thing to have ever happened in our universe, which is the big bang. Yeah. What's up with the big bang? RSS we can I mean, with gravitational waves, the hope is when you have more and more accurate measurements of the gravitational waves, you can crawl back further and further back in time towards a big bang? Did did you ever hope to be able to understand the the early spark that created Our our universe? Yeah. You know, that and the deep interior of a black hole. I think the the biggest mysteries that we hope the melding of quantum mechanics and gravity will reveal, will illuminate. And you know, what question could be more captivating, then why is there something rather than nothing? Right? Why is there a universe at all? And will the theories that we're developing take us to an answer to that? I don't know. Even if we truly knew what the big bang is, that's a big question in own. Right? When would still be left with the question, well, okay. So you've explained the process by which a tiny nugget of a universe, a tiny nugget of space time can undergo some kind of growth to yield the world around us. But presumably in that explanation, you're going to involve mathematics and some ingredients like quantum fields or, or matter, or energy or something, where did that stuff come But presumably in that explanation, you're going to involve mathematics and some ingredients like quantum fields, or matter energy or something, where did that stuff come from? You know, can we get to that level explanation. I don't know. But it is remarkable that if you RSS, what happened a millionth of a second? After the big bang. It's not really that controversial any longer. Right? Even though there's a lot of argument in the field and it's very heated right now, I should say, regarding what is the right theory of the big bang? What is the right theory of early universe cosmology, where I mean, early, much earlier than month of a second. A lot of descent, a lot of heated arguments about that. No pun intended. Yeah. Right. Exactly. But but but you go, like, a million for the second half. After that. Yeah. And and we're pretty firm grant. Isn't that amazing Isn't that amazing? Right? Yeah. To to understand, you know, what happened from that point forward. But to go back, is is is controversial. So there is this theory called inflationary cosmology, which I would say has been the dominant paradigm since early nineteen eighties. So what does that mean? Roughly forty years now. It's been the dominant cosmological paradigm. And it makes use of a curious feature of Einstein's general theory of relativity is theory of gravity. Where Einstein shows us mathematically that gravity can not only be attractive, you know, the kind of gravity that we're used to things pulled together, but it can also be repulsive. And that fact is then leveraged by people like Alan Good. And and Andre Linde and at the time Paul Steinhart and Andre's Hall Brecht and others 25 okay, if we had little nugget in the earlier universe, which was filled with the stuff that yields this repulsive gravity. Well, that would have blown everything apart. It would cause everything to swell. Beautiful explanation for what the bang in the big bang was and then people mathematically analyze the consequences of this idea and they make predictions for tiny temperature differences across the night sky that in principle could be measured. You send up balloons, you send up satellites with very refined thermometers, and they measured the temperature of the night sky and the statistical distribution of the temperature differences agrees with the mathematical predictions. Yeah. I mean, amazing. You just sort of have to stand in awe of of this insight. So you think aha, the theory has been established. But scientists are an incredibly skeptical bunch. And some scientists, including one of the people who help developed a theory of the outset, Paul Steinhart, comes along and says, well, yeah, it's done. This theory has done pretty well so far, but their aspects of this theory that are making me lose confidence. For instance, this theory seems to suggest that there might be other universes. Like how do you make sense of a theory that suggests there are other universes? Or are there others who come along and say this theory seems to talk about length scales that are minuscule even by the so called plank length, the sort of shortest length that we can imagine making sense of in a theory of quantum gravity. How do you make sense of that? And so on so they develop a list of of things that they consider to be chinks in the inflationary cosmological theories armor. And they develop other ideas which they claim yield the same predictions as inflationary cosmology for those temperature differences across space, but don't suffer from these problems. And then the inflationary cosmology folks. Even now? No. No. Hang on. Yeah. Your theory suffers from different problems. And so the arguments goes, it's a healthy debate. Talk about real debates in science. So when you ask, what's up with the big bang? I don't know right now. If you would have asked me five years ago, maybe even less than that three or four years ago. I said, look, inflation at cosmology has some issues. But the package of explanations it provides is so potent and the issues that beset it are seemingly solvable to me that I would imagine it's going to in the end went out. I would still say that today, but I wouldn't say it as loudly. I wouldn't say it as confidently. I think it's worth thinking about alternate ideas and it could be the case that the paradigm at some point shifts. Does dark matter and dark energy fit into the the shift shifting of the explanations for those? Yeah. Certainly. So dark energy has in in the inflationary theory RSS kind of a big mystery. So dark energy is the observational realization in the last twenty years that not only is universe expanding, it's expanding ever more quickly. Something is still pushing things outward. And the explanation is that there's like a residual version of the repulsive gravity from the early universe, but It's such a strange number. When you write that amount of dark energy using the relevant units in a theory of quantum gravity, it's a decimal point followed by like a hundred and twenty zeros and then a one. Mhmm. We're not used to those kinds of numbers. In physics. We're used to a half, one pie, e, square to two. Those are the kinds of fundamental numbers that emerge in our explanations of world, and we look at this bizarre number, decimal point, all these zeros, and it won't be say, something's wrong there. Like, where would that number have come from? Now there are people who suggest resolution to it, so it's not like we're totally in the dark on it, but those people like Paul dinehart who have alternate cosmological theories, cyclic cosmologies, as they call it, claim, that they have more natural explanation of the dark energy that it naturally feeds into a cyclical process that is their cosmological paradigm. So, yeah, if the cosmology should change, it's conceivable our view of dark energy may change from deeply mysterious to deeply integrate it into a different paradigm. That is possible. I think it's Roger Penrose that think that information complete through from before the big bang to the after the big bang. Yeah. Is that is the big bang, like, a full ratio of the hard drive, or is there some information that could bleed through. Yeah. I mean, so so Roger is among the most creative thinkers of the last hundred years. Rightly won the Nobel Prize for insights into singularities and space time that we know to afflict our mathematical solutions of black holes in the big bang and so forth. And he has an enormously fertile imagination and and I mean that in the most positive sense. And so he has put forward this idea, this conformal cyclic cosmology, I the official title, although I could be getting that wrong. I can't say that I've studied it. I have seen lectures on it. I don't find it convincing as yet. It feels like it's being built to find a solution as opposed to sort of more naturally It feels like it's being built to find a solution as opposed to sort of more naturally emerging. Maybe Roger would say otherwise, and I don't mean 25, in any way, cast dispersions on the work. It's it's vital and interesting and people are thinking about it. I don't consider it as close a competitor to say the inflationary theory as, for instance, the stuff that Paul Steinhart has put forward. But, again, you've got you gotta keep an open mind in this in this business when there's so much that we don't yet understand. I mean, it is wild to think that information could survive something like that. Just like it is wild to imagine that information could escape a black hole example. It just seems like by construction, these things are supposed to not bleed out NI. But one of the challenges in all these theories is when we talk about a singularity, has this real sexy term, the singularity. Yeah. But a singularity is is in more ordinary language, a a physical system where the mathematics breaks down -- Mhmm. -- it's 10. It's like taking one divided by zero, you put that into a calculator, and it says e error. Right? It does not make sense, doesn't compute. And and so it's very hard to make definitive statements about things like the Big Bang or about black holes until we cure the mathematical singularity. And there are some who claim that in certain regimes, the singularities have been cured. I don't, by any means, think that there's consensus. On these ideas. So when when talks about information sort of bleeding through the big thing, you've really got to make sure that the equations have no singularity. You talk about cyclic cosmology. You gotta make sure that the equations don't have any singularities as you go from, say, one cycle to the next. Now some of the proponents of these theories claim that they have resolved these issues. I don't think that there's a general sense that that is the case as yet, but it could be that look, life is so short that I haven't had the time to deeply delve into all the mathematical intricacies of all the ideas that have been put forward, but did that, I'd never do anything else. But that that's what the issue is. And of course, it's just math. There may be holes. There may be there may be gaps in our understanding in the way we're modeling physical Well, well, That's the point. In fact, when you said I was about to jump in and say modeling, but you got their first, and it's exactly the right point. You're talking about the universe here. Right? And the how do you how do you talk about the universe with a straight face? Mathematically. And the way you do it is you you simplify. You throw away those characteristics of the universe that you don't think are vital to a full understanding. And so we're going to get to a point people are starting to where we've got to go beyond those simplifications. And so cosmology has for a long time, model the universe in the most simplest terms, homogeneous, isotropic. It has just a few parameters that describe it, the average density of mass and energy and so forth. We have to go beyond those simplifications, and that will require putting these things on computers. We're not gonna be able to do calculations there. So much as astrophysics has gone beyond many simplifications, and I give really detailed simulations of star systems and galaxies and so forth, we're gonna have to do that with cosmology and people are starting to do that today. Yeah, I've seen some interesting work on simulation. Most simulation cosmology, by the way, is just awesome. But, you know, just like simulation of the early formation of our solar system them 25 understand how the, like, the old cloud and just I don't know. The the whole of it, the the how earth came to be. Yeah. Like, how Jupiter just -- The protects us. -- protects us. And then there's, like, weird, like, moons and volcanoes and and, like, modeling all of that. The formation of all of that is fascinating. Yeah. Because that naturally is the question of how does life emerge in these kinds of rocks? How does a rock become a rabbit? Yep. But speaking of models, there's an equation called the dray equation. Yep. We were talking about life. Have to ask when you at the highest level first, when you look out there, how many alien civilization do you think are out there? Zero one or many. So if you say civilization, I would bring my number way down, it could be zero. If you talk about life, I think it could be many. As we're saying before, I think the move from life to consciousness, the kinds of beings that would build what we would recognize as a civilization. That may be extraordinarily rare. I hope it's not. You know, as kid I love. Star trek. I I just love the idea that we would be part of some universal community where, look, experience in planet Earth suggests it doesn't always go so well when groups who are separated try to come together and and live in some larger collective. But again, as an optimist, how amazing would it be to converse with an alien civilization and and learn what they've figured out about physics and cosmology and and compare notes and and and learn from each other in in some some wonderful way. III love that idea. But if you RSS me the likelihood of it, I I would air on saying it may be so improbable that the conditions conspire to allow life to move to this place of of consciousness is that it might be rare. It might be over simplifying things, but just observing the power of the evolutionary process, I tend to believe and, like, you read different theories of how we went. Cajon recipients evolved. It seems like dilution process us naturally at least to to the homo sapiens or or creatures like that or much better than that. To me, the there's several scary scenarios. So okay. The positive scenario is life. It's self is really difficult. So that origin of life is difficult. That's exciting for many reasons, because we might be able to prove that wrong easily in the near term by finding life That's exciting for many reasons because we might be able to prove that wrong easily in the near term by finding life elsewhere. Sure. The scary thing to me is if life is easy, and there's plenty of conscious intelligent civilizations out there and we have not obviously made contact, which means with intelligence and consciousness comes responsibility and, ultimately, destruction. Yeah. So with power comes great responsibility. And then we end up destroying ourselves. That's the the scariest. The the positive, I guess, version is that maybe we're being watched, sort of like, does a transition to where you don't wanna ruin the primitive villages out there. And so there's a protective layer around us -- Yeah. -- they're they're watching. So where where do you in this possible explanation to the Fermi Paradox? Why haven't we contacted aliens? Do you -- Yeah. -- do you land on? Well, I think the most straightforward explanation is that there aren't any, now there are many other explanations think the most straightforward explanation is that there aren't any. Now there are many other explanations too. So you can't be dogmatic about things that are just sort of gut feel. But you you know, one of my favorite twilight zone episodes on a paper softness one where, you know, the alien civilization finally comes to planet Earth and and gives us this book that that they really want us to to have and to hold. And it's in this Brians you know, language. You don't understand it. The cryptographers, they desperately tried to decipher it as humans are going to visit this other alien planet. They're all sending back postcards, how wonderful it is and so forth. And they they finally the the side for the title RSS to serve man. And everyone's so thrilled out there here to service. It all makes sense. And then just as one of the final cryptographers is going on to the alien ship, his his helper runs and says, I've deciphered the rest of the book 25 serve man. It's a cookbook, you know. you know Yeah. So so, yeah, is that RSS Adam? It's a possibility short, you know. And and so could they be watching us since you're sort of waiting for us to get to a mature enough level? I don't know. It strikes me well, you know, I think it'd be better to have this conversation after the James Webb It strikes me you know, I think it'd be better to have this conversation after the James Webb telescope. I mean, I do think that if we look at the atmospheres of many planets. I mean, there's now an estimate now that there's on order of one planet per star on average. So we've long known that, you know, the galaxy hundreds of billions of stars, numbers of galaxies, hundreds of billions of galaxies that we're talking about hundreds of billions of hundreds billions planets. my. You know, and if we start to survey some of these planets and one after the other, after the other, we just sort of find no evidence for any of the biological I You know? And if we start to survey some of these planets, and one after the other after the other after the other, we just sort of find no evidence for any of the biological markers. It could be, of course, maybe life takes a radically different form. It'd be hard to know that. But I think, you know, that would at least give us some insight on the life question. But I just don't see how we get insight on the civilization or consciousness question without, you know, the direct connection. And and it's strikes me that if consciousness is ubiquitous, let's say life is. Mhmm. I'm willing to grant that. If consciousness is also ubiquitous, then I don't understand why they haven't been here or why there hasn't been separate decision because presumably they should be much further ahead of us. How unlikely would it be that we're like of all consciousness in the universe were the most advanced, that'd be such a special place for human How unlikely would it be that we're like, of all consciousness in the universe, we're the most advanced. Mhmm. That'd be such a special place for human beings that it's hard for me to grant that as a likely possibility. Rather, I think we're kind of running the mill. And there are many who are far more advanced than us. And don't think that they would expend the energy to hide themselves. I don't think they care enough. And so, you see, that's actually what I I believe that there's a a very large number civilizations that are far more advanced than RSS. But my sense is that humans are exceptionally limited both in our direct sensory capabilities and our physics our tools of of sensing just like with the string theory in the multiple dimensions. We're just not like, it's like I honestly believe there could be stuff in front of our nose that we're just not seeing. work. Cause we're too dumb too, too much we're too dumb, too too much hubris. And, I mean, it's a bunch of stuff and too ignorant as to 25 the fabric of reality. All of those things -- Yeah. -- we're young -- Yeah. -- in terms of intelligence. But I guess what it says, like, I'm on board. With all of that as real possibility. But then, it does strike me that we are sufficiently able to observe the unit. Look, we can look back to, you know, a fraction of the duration from here to the just fraction is left that we are unable to see. Mhmm. So however young we are, we have been able to sort of pierce the universe, and it just strikes me that there would be some signature, but maybe maybe that that's coming. But but look, having said that I do look, III certainly note the fact that it's rare, that I stooped down while walking in Manhattan and sort of dig up some ants in the bushes on the side of the street and talk to the ants. Right? Because it's just not interesting to me. So if we're like the ants, on the cosmological landscape, then yeah, I can imagine that the super advanced aliens would be like like whoever you know, but but I feel like we're sufficiently advanced that there should be some signal signature of that, but maybe it's coming. I think the deeper fundamental problem between us and the ants is that we don't have common language. It's not it's not the interest. It's that we don't even have a common language. And so the the alien civilizations don't even know. Like, we humans have convinced ourselves for special because developed the language. You you talked about you talk about the importance of language to the intelligence. But it it makes you wonder, like, how very niches that, like, club that we've, like, tribe, we've created of language and linguistic type of systems that are very specific to our particular kinds of and share ideas together. We're all super excited that we can understand the universe because we came up with some notation -- Yeah. -- and math. I wonder if there's some 25 the other kinds of language that communicates on a different time scale with different very different mechanisms in a space of information that's just there's not It's true. Everything everything is lost in translation. Yeah. And it could well be as a look. I mean, I think part of the reason I go toward the possibility of the soul intelligence RSS there's certain kind of romantic appeal to looking out in the cosmos and it's just quiet, and it's just eternal silence. There's some there's something that appeals to me at an emotional level that way But yeah, I mean, nobody nobody knows. And it's certainly conceivable that where there's just a radical mismatch between the kinds of things that we are able to observe and sensitive to versus the kinds of structures that permeate the universe in a manner that simply we're unable to detect. Well, if we are alone that is exciting and one of the ways it's exciting is that it's up to us to become to expand out into the universe. To permeate consciousness out into the universe. So that's first paced exploration comes in. LEX me ask you, is is somebody who's a string theorist, the physicist, do you think space exploration, a colonizing space? Is it physics or an engineering problem. What would you say? Yeah. I think it's fundamentally an engineering problem. If we're not trying to do things like build worm holes the way they did, say, an interstellar 25 get to a different place for trying to travel near the speed of light that we would actually be able to traverse interstellar distances. I mean, without that, our colonization will happen in a very very slow rate. Right? But one of the beauties of of relativity is if you do travel near this beauty, but you you can actually go arbitrarily far in human lifetime. People say, how is that possible? You can't go billions of light years or you can. Actually. Because as you can move this split of light, the way in which space and time change allows you to go in principle arbitrarily far. That's that's very exciting. But if we put that physics side of the issue and the manipulation of space and time to the side, yeah, I think it's a deep engineering problem. know, how do you terraform other planets? I mean, how do you go beyond our local neighborhood say without, you know, using the ideas of relativity. So I think it's all quite exciting. And I think the idea is, you know, using solar sales that, you know, people have developed and, you know, trying to take that first step to Mars. I think that's a a vital and valuable step to take. But, yeah, think these are fundamentally engineering challenges or extending the human lifespan through biology research or maybe reducing what it means to be a human being into information and uploading certain parts of it, maybe not all full resolution of a human life, but maybe the essential things like the DNA and be able to reconstruct that human being. Yep. But, you know, I had to ask about Mars. You know, do you do you find the the dream of humans stepping on Mars, stepping foot first, but also colonizing Mars. One that's worth us fighting for? Yeah. Usually so. I mean, I think what we have long been not always in the best way is a species of explorers in the literal sense of traveling from one part of the world to another or in the more metaphorical sense of trying to travel through our minds to the quantum realm or back to the big bang or to the center of black holes. So I think that's fundamentally part of of the human spirit. So I do think that's a vital part of our heritage brought forward into its next incarnation? That's who we are. Do you think there'll be a day in the future where a human being is born on Mars and has to learn about his or her human origins on earth? Like, they'll have to read in the book. Yeah. I don't think it'll be a book at that stage. It'll probably just be uploaded into the head or something. Or, you know, and print it into the DNA, and then they just sort of sense it. But yeah, I think there's there's well, look, the the issue you raised before is the vital one. Is it the case that any sufficiently advanced civilization destroys itself? Is that sort of a common place quality. I mean, that's the other potential answer to the Fermi Paradox. Why aren't they here? Because by the time they got to the technological development where they travel here. They blew themselves up. They destroyed themselves. And that's a, you know, an, you know, an unfortunate but, you know, not a hard to imagine possibility based on things that have happened here on planet Earth. But but putting that to the side, think it you know, that's big obstacle. But put it the side, we will resolve the engineering challenges. And and, you know, as you as you probably modify my answer from before, you said, is it engineering or physics? It's really both. Right? So so we will surmount the engineering challenges, and that will then make the physics challenges relevant It'll make it relevant to figure out how to travel near this beautiful light. It'll make it relevant to learn how to manipulate the shape of of space time and so forth. RSS so I think it's a multistage process where it is engineering and ultimately physics. And if we stick around long enough, Those are the kinds of challenges I think that we're ultimately gonna surmount. And then the physics side is figuring out how to harness energy enough to travel outside the solar system, which seems like a heck of a difficult journey. But even Mars itself have I don't know. Maybe because I I was born in the Soviet Union and it was born with the the, you know, looking up at the stars in that dream of, like, the highest of human achievement, his ability fly out there to to, you know, to join the Stars. I I really like the idea of of going to Mars of and not just stepping foot to Mars. It it wasn't until, maybe, misinformed, but for me, personally, it wasn't until you must started talking about the colonization of Mars. Did I realize, like, we we humans can actually do that? And the first of all, the importance of somebody saying that we can do these seemingly impossible things is immeasurable because, you know, the fact that he he placed that into my mind and into the minds and millions of others, maybe hundreds of millions, maybe billions of others, young kids today. I mean, that that's gonna make it reality. For some reason, deeply excited even though my work is an AI that echoes all of this. I'm excited by the idea that somebody would be born as we were saying on Mars and sort of look up and be able to see with the telescope earth and say that's where I I came from. I don't know that that idea scale to other planets, to other solar systems. Yeah. That's really exciting. It's Hugely exciting. III think you're absolutely right. I mean, the vital thing is to dream. Right? I I mean and it's not a hackney, but it is so important for for young kids for the next generation 25 to think about the things that are seemingly impossible I mean, that's what makes them possible. And this is one which is concrete enough. I mean, this is something that's gonna happen soon in terms of actually going to Mars. And then the next step of establishing some presence, some semi permanent or permanent presence. This is this is not something that's gonna wait the twenty fifth century. I mean, this is something that's gonna happen relatively soon. Mhmm. So, I mean, it could be in your lifetime, unlikely mine, but possibly in your lifetime that that kid will be born and and and have the experience that that you described. So, yeah, six spectacularly exciting. And I actually I would love to go on Mars on one of the early You would, yeah, You would? Yeah. You would It was one way I was, I'm happy to it one way? I was I'm happy doing one really. Wow. Yeah. And I'm I'm single. If there's leaves out there, they wanna start that family. Let's go let's go out to Mars. NI. I think See, I have to tell you something. You just talk about terror? Thinking about, like, black holes. Mhmm. If I actually think about going to Mars and being on Mars, and put myself in there fully. That's terror inducing. The idea of to be in this foreign world where you can't come back, where you've made this this choice that can't be reversed. Oh, you know, at some point, it may be. But but in that guys, that, to me, carries a deep sense of terror. You know, I I feel that sense of terror every time Kerak, Jack Kerak talked about this on the road is, you know, when you leave a place, if you're honest about it, like life is short. And when you leave a place, place, you moved to a new place, and you think of all the friends, maybe family, you're leaving behind as you drive over the hill, that that really is goodbye. We sometimes don't think of it that way when we're moving, but that really is goodbye to that life, to the person you were, to the all the people maybe if it's close friends, you'll see them maybe ten, fifteen more times in your life, and that's it. Yeah. And you're saying goodbye to all of that. And so in the same way, I I see it as way more dramatic when you're flying away from Earth and it's like, it's goodbye to Dunkin' Donuts and Starbucks and It's it's goodbye to whatever I I don't know why I picked those, but some all the things that -- Yeah. -- are special to Earth. It's goodbye. But that's that's life. I I suppose more what excites me about that kind of journey is it's a distinct contemplation of your mortality acceptance your mortality. You're saying, just like when you take on any difficult journey, it's accepting that you're going to die one day. And might as well do something truly exciting. Yes. I mean, I, well, you know, I'm with you on I will you know, I'm with you on that. I I'm a strong believer that deep underneath human motivation is this this terror of our own mortality. Yeah. There's this wonderful book that had a great influence and may call a denial of death by Ernest Becker. And when you are aware of the ways in which our mortality influences our behaviors. It really does add a different slant, a different kind of color, to the interpretation. Of human behavior. Yeah. It it's funny that that book had a big influence on me as well. Was that right? Why? And the terror management theory and and -- Yeah. -- I again, from an engineering perspective, I don't know how many people that book influenced. Because I I talked to people about the fear of death and it doesn't seem to be that fundamental to their experience. And I don't think on the surface fundamental to my experience, but it seems like an awfully in terms of we talk about models and strength theory and theories. In terms of theories, of this macro experience of human life, it seems like a heck of a good theory that the fear of death is that the kind of is the warm at the core. Yeah? Well, I mean, and the terror management theories that you make reference 25, I mean, the this is group of, you know, psychology social psychologists who devise these very clever experiments, real world experiments with real people, where you can directly measure the hidden influence of the recognition of our own mortality. I mean, if them is experiments. So they have group of people, a group of people Brians the only difference between the two groups is that group b, they somehow reminded them in some subtle way of their own mortality. Sometimes it's nothing more than interviewing them -- Mhmm. -- with a funeral home across the street. You know, an influence is there, but but it's telling you don't even think you'd take note of. And they can find measurable effects that differentiate the two groups to a high degree of statistics identical significance and how they respond to certain challenges or certain kinds of questions that shows a direct influence of the reminder of their own mortality. And I've read a number of these studies, and they are really convincing. And yeah, I would say that the reason why so many people would say that, yeah, fear of mortality. It's not front and center in my worldview. Yeah. I don't really think about it. Much doesn't really matter much. The reason why they're able to say that is because this thing called culture has emerged over the course of the last ten thousand years. Yeah. And part of the role of culture is to give us a means of not thinking about our more tality all the time of not living in terror of the inevitable end, which faces us all. So it's completely understandable that that's a response because that's what culture is at least in part for. It's at least possible that the fear of death. The terror of your mortality is the creative force that created all of the things around us at this human civilization. Yeah. And and I think about from an engineering perspective, this is where I lose all of my robotics colleagues. Is I feel like if you want to create intelligence, you have to also engineer in some kind of echoes of this kind of fear of and not you know, fear is such a complicated word, but a kind of like a scarcity, a scarcity of time, a scarcity of resources that creates a kind of anxiety, like deadlines, get you to do stuff. Yeah. And there's something almost fundamental to that in terms of human experience. Well, that's an interesting thought. So you're basically in order to create a kind of structure that mirrors what we call consciousness. Yes. You'd better have that structure confront the same kinds of issues and tears, thoughts that we do. Consciousness and suffering only makes sense in the context of death. If you want to I feel like if you want to fit into human society, if you if you're a robot, if you want to fit into human society, you better have the same kind of existential dread, the same kind of fear of mortality. Otherwise, you're not gonna fit in. Right? Yeah. It might be it might be wild, but at least, like, we're talking about all the theories that are at least worth consideration. I think that's a really powerful one. And definitely one is resonated with me. And definitely seems to capture something beautifully, like, real about the human condition. And I I wonder it's, of course, sucks to think that we need death to appreciate life. But that's just maybe the way it is. What's interesting if this robotic or artificially intelligent system understands the world and understands the second law of thermodynamics and entropy, even in artificial intelligence will realize that even if RSS parts are really robust, ultimately, it will disintegrate. Yeah. I mean, so the time scales may be different. But in a way when you think about it, it doesn't matter once you know that you are mortal in the sense that you are not eternal the time scale hardly matters -- Mhmm. -- because it's it's either the whole thing or not. Because on the scales of eternity, any finite duration however large is effectively zero -- Mhmm. -- on the scales of eternity. And so maybe it won't be so hard for an artificial system to feel that sense of mortality because it will recognize the underlying physical laws and recognize its own finitude. And then it'll be us and robots drinking beers, looking up at the stars and just, you know, having a good laugh in awe of the whole thing. Yeah. I think that's a pretty good way ended talking about the fear of death. We started talking about the meaning of life and ended on the fear of death, Brians. Just an incredible comment Thank you. enjoyed it. NI Really really enjoyed. It has been a long time it. It's been a long time coming. I'm a huge fan of your work, a huge fan of your writing. Thanks for talking to everyone. Thank you. Thanks for listening to this conversation with Brian Green. To support the podcast, please check out our sponsors in the description. And now LEX me leave you some words from Bill Bryson. Physics is really nothing more than a search for ultimate simplicity. But so far, all we have is a kind of elegant messiness. Thank you for listening and hope to see you next time.