Brian Greene: Quantum Gravity, The Big Bang, Aliens, Death, and Meaning #232

Transcript

00:00:00 The following is a conversation with Brian Greene,

00:00:02 theoretical physicist at Columbia

00:00:04 and author of many amazing books on physics,

00:00:08 including his latest, Until the End of Time,

00:00:11 Mind, Matter, and Our Search for Meaning

00:00:14 in an Evolving Universe.

00:00:16 This is the Lex Friedman podcast.

00:00:19 To support it, please check out our sponsors

00:00:21 in the description.

00:00:22 And now, here’s my conversation with Brian Greene.

00:00:27 In your most recent book, Until the End of Time,

00:00:29 you quote Bertrand Russell from a debate he had

00:00:32 about God in 1948.

00:00:34 He says, quote,

00:00:37 “‘So far as scientific evidence goes,

00:00:39 “’the universe has crawled by slow stages

00:00:42 “’to a somewhat pitiful result on this earth,

00:00:45 “‘and is going to crawl by still more pitiful stages

00:00:48 “’to a condition of universal death.

00:00:52 “‘If this is to be taken as evidence of purpose,

00:00:54 “‘I can only say that the purpose is one

00:00:57 “’that does not appeal to me.

00:00:59 “‘I see no reason, therefore,

00:01:01 “’to believe in any sort of God.’”

00:01:04 That’s quite a depressing statement.

00:01:06 As you say, this is a bleak outlook on our universe

00:01:09 and the emergence of human consciousness.

00:01:12 So let me ask, what is the more hopeful perspective

00:01:15 to take on this story?

00:01:18 Well, I think the more hopeful perspective

00:01:19 is to more fully understand

00:01:25 what was driving Bertrand Russell to this perspective,

00:01:28 and then to see it within a broader context.

00:01:32 And really, that’s, in some sense,

00:01:34 what my book, Until the End of Time, is all about.

00:01:37 But in brief, I would say that there’s a lot of truth

00:01:41 to what Bertrand Russell was saying there.

00:01:43 When you look at the second law of thermodynamics,

00:01:45 which is the underlying scientific idea

00:01:48 that’s driving this notion that everything’s gonna wither,

00:01:51 decay, fall apart, yeah, that’s true.

00:01:55 Second law of thermodynamics establishes

00:01:57 that disorder, entropy, in aggregate,

00:02:00 is always on the rise.

00:02:02 And that is indeed interpretable

00:02:05 as disintegration and destruction

00:02:07 over sufficiently long timescales.

00:02:09 But my view is, when you recognize

00:02:12 how special that makes us,

00:02:14 that we are these exquisitely ordered configurations

00:02:18 of particles that only will last for a blink of an eye

00:02:22 in cosmological time like terms,

00:02:25 the fact that we’re here and we can do what we do,

00:02:27 to me, that’s just really something

00:02:30 that inspires gratitude and wonder

00:02:34 and a sense of deep purpose

00:02:38 by virtue of being these unique collections of entities

00:02:42 that happen to rise up, look around,

00:02:44 and try to figure out where we are

00:02:46 and what the heck we should do with our time.

00:02:48 So it’s not that I would disagree with Bertrand Russell

00:02:51 in terms of the basic physics and the basic unfolding,

00:02:58 but I think it’s really a matter of the slant

00:03:00 that you take on what it means for us.

00:03:04 So maybe we’ll skip around a bit,

00:03:06 but let me ask the biggest possible question then.

00:03:09 You said purpose.

00:03:10 So what’s the meaning of it all then?

00:03:12 Is there a meaning to life that we can take from this,

00:03:17 from this brief emergence of complexity

00:03:22 that arises from simple things

00:03:24 and then goes into a heat death

00:03:26 that is once again returns to simple things

00:03:29 as the march of the second law of thermodynamics goes on?

00:03:33 I think there is,

00:03:33 but I don’t think it’s a universal answer.

00:03:36 And so I think throughout the ages,

00:03:39 there has been a kind of quest for some final way

00:03:44 of articulating meaning and purpose,

00:03:47 whether it’s God, whether it’s love,

00:03:50 whether it’s companionship.

00:03:51 I mean, many people put forward different ways

00:03:53 of taking this question on,

00:03:56 and there is no one right answer

00:03:59 when you recognize deeply that the universe doesn’t care.

00:04:05 There is nothing out there that is the final answer.

00:04:08 It’s not as though we need a more powerful telescope

00:04:11 and somehow if we can look deeply into the universe,

00:04:14 all will become clear.

00:04:17 In fact, the deeper we’ve looked,

00:04:18 both literally and metaphorically,

00:04:21 into the universe and into the structure of reality,

00:04:24 the more it’s become clear

00:04:27 that we are just a momentary byproduct

00:04:30 of laws of physics that don’t have any emotional content.

00:04:36 They don’t have any intrinsic sense of meaning or purpose.

00:04:39 And when you recognize that,

00:04:41 you realize that searching for the universal

00:04:43 for this kind of a question is a fool’s errand.

00:04:47 Every individual has the capacity to make their own meaning,

00:04:51 to set their own purpose.

00:04:53 And that’s not some platitude, that is what we are.

00:04:57 Because there is no fundamental answer,

00:04:59 it’s what you make of it.

00:05:01 And however much that may sound like a hallmark card,

00:05:04 this really is the deep lesson of physics and science

00:05:09 more generally over the past few hundred years.

00:05:11 Well, there’s some level where you can objectively say

00:05:14 that whatever we’ve got going on here,

00:05:16 it’s kind of peculiar.

00:05:18 It’s kind of special in terms of complexity.

00:05:23 And maybe you can even begin to measure it

00:05:26 and like come up with metrics

00:05:28 where whatever we’ve got going on on Earth,

00:05:31 these like interesting hierarchical complexities

00:05:35 that form more and more sophisticated biological system,

00:05:39 that seems kind of unique

00:05:40 when you look at the entire universe,

00:05:45 the observable part that we can see with our tools.

00:05:48 I mean, so I have to ask,

00:05:50 as you describe in your book once again,

00:05:53 Schrodinger wrote the book,

00:05:55 “‘What is Life?’ based on a few lectures he gave in 1944.”

00:05:59 So let me ask the fundamental question here.

00:06:02 What is life?

00:06:04 This particular thing we’ve got going on here,

00:06:06 this pocket of complexity

00:06:08 that emerged from such simple things?

00:06:10 Yeah, it’s a tough question.

00:06:11 I asked that question even to Richard Dawkins once,

00:06:15 and I already have my preconceived notion,

00:06:18 which he pretty much confirmed,

00:06:20 which is if one could give an answer to that question

00:06:24 that allowed you to sort of draw a line in the sand

00:06:28 between the not living and the living,

00:06:30 then perhaps we would have the insight that we yearn for

00:06:34 and trying to say, what is so special about life?

00:06:36 But the fact of the matter is, it’s a continuum.

00:06:39 There’s a continuum from the things

00:06:41 that we would typically call nonliving and animate

00:06:44 to the things that we obviously call animate

00:06:46 and full of the currents of life.

00:06:49 Somewhere in there,

00:06:51 it is a question of the complexity of the structure,

00:06:55 the ability of the structure to take in raw material

00:07:00 from the environment and process it through a metabolism

00:07:04 that allows the structure to extract energy

00:07:07 and to release entropy to the wider environment.

00:07:10 Somewhere in those collections of biological processes

00:07:15 is the necessity or the necessary ingredients

00:07:19 and processes for life,

00:07:20 but drawing that line in the sand

00:07:22 is not something that we’re able to do,

00:07:25 but I would agree with you.

00:07:27 It’s deeply peculiar.

00:07:30 It may in fact be unique,

00:07:33 but it may not.

00:07:35 It could be that the universe is such

00:07:38 that under fairly typical conditions,

00:07:41 a star that’s a well ordered source of low entropy energy,

00:07:47 that’s what the sun is,

00:07:49 together with a planet being bathed

00:07:51 by that low entropy energy,

00:07:52 together with a surface that has enough

00:07:55 of the raw constituents that we recognize

00:07:59 are fairly commonplace result of supernova explosions

00:08:03 where a star spews forth the result of the nuclear furnace

00:08:07 that is the core of a star.

00:08:09 It could be that all you need

00:08:11 are those fairly commonplace conditions

00:08:15 and maybe life naturally forms.

00:08:17 Look, the James Webb Space Telescope, right?

00:08:19 It’s going up hopefully in December.

00:08:21 And one of the goals of that mission

00:08:23 is to look at atmospheres around distant planets

00:08:26 and perhaps come to some sense of how special

00:08:30 or not life or life as we know it is in the universe.

00:08:35 Which part of the story of life,

00:08:39 let’s stick to Earth for a second,

00:08:40 do you think is the hardest?

00:08:42 If you were like a betting man,

00:08:45 which part is the hardest to make happen?

00:08:48 Is it the origin of life?

00:08:50 Again, we haven’t drawn the line where,

00:08:52 as you say, the line between a rock and a rabbit.

00:08:55 That part, is it complex organisms,

00:09:01 like multicellular organisms?

00:09:03 Is it crawling out of the ocean

00:09:05 where the fish somehow figured out how to crawl around?

00:09:09 Is it then the us homo sapiens,

00:09:12 as we like to think of ourselves special and intelligent?

00:09:17 Or is it somewhere in between?

00:09:18 As you also talk about, again, very hard to know

00:09:23 at which point this consciousness emerge.

00:09:28 If you were to sort of took us a survey

00:09:31 and made bets about other Earth like planets in the universe,

00:09:36 where do you think they get stuck the most?

00:09:38 Well, I would certainly say if we’re gonna go all the way

00:09:40 to conscious beings like ourselves,

00:09:42 I would put it at the onset of consciousness,

00:09:45 which again, I think is a continuum.

00:09:47 I don’t think it is something that you can draw the line

00:09:50 in the sand, but there are obvious circumstances,

00:09:53 there are obvious creatures such as ourselves

00:09:56 where we do recognize a certain kind

00:09:58 of self reflective conscious awareness.

00:10:01 And if we think about what it would require

00:10:05 for a system of living beings to acquire consciousness,

00:10:10 I think that’s probably the hardest part because look,

00:10:14 take Earth and recognize that weren’t for,

00:10:18 some singular event 65 million years ago

00:10:21 where this large rock slams into planet Earth

00:10:25 and wipes out the dinosaurs,

00:10:27 maybe the dinosaurs would still rule the planet

00:10:31 and they may well have not developed

00:10:35 the kind of conscious awareness that we have.

00:10:38 So for billions of years on this planet,

00:10:41 there was life that didn’t have the kind

00:10:44 of conscious awareness that we have.

00:10:47 And it was an accidental event in astrophysical history

00:10:52 that allowed a mammalian species like us

00:10:56 to ultimately be the end product.

00:10:58 And so, yeah, I could imagine there’s a lot of life

00:11:00 out there, but perhaps none of it’s wondering

00:11:04 what’s the meaning of life or trying to make sense of it,

00:11:08 just going about its business of survival,

00:11:11 which of course is the dominant activity

00:11:13 that life on this planet has practiced.

00:11:15 We are a rare exception to that.

00:11:17 And I really appreciate that you lean into

00:11:20 some of these unanswerable questions from me today.

00:11:22 But the, so you think about consciousness,

00:11:25 not as like a phase shift, the binary zero one,

00:11:28 you think of it as a continuum that humans somehow

00:11:33 are maybe some of the most conscious beings on Earth.

00:11:37 So you’re, so.

00:11:39 I mean, people will dispute that.

00:11:40 Yes, I mean, well, and it’s a very hard argument.

00:11:43 People will dispute that, rocks probably

00:11:45 will stay quiet on the matter.

00:11:47 Maybe not, right?

00:11:48 For the moment, they’re waiting for their opportunity.

00:11:51 But I agree that, look, even when you and I

00:11:57 look at each other, I am not fully convinced

00:12:01 that you’re a conscious being, right?

00:12:03 I mean, I think that you are.

00:12:04 It’s not to me.

00:12:05 I mean, your behavior is such that

00:12:07 that’s the best explanation for what’s going on.

00:12:09 But of course, we’re all in the position

00:12:11 of only having direct awareness of our own conscious being.

00:12:16 And therefore, when it comes to other creatures in the world,

00:12:19 we’re in a similar state of ignorance

00:12:21 regarding what’s actually happening inside of their head,

00:12:25 if they have a head.

00:12:26 And so it’s hard to know how singular we are,

00:12:30 but I would say based on the best available data

00:12:33 and the best explanations that we can make,

00:12:34 yeah, there is something special about us.

00:12:36 I don’t think that there are fish walking around

00:12:39 and coming up with existentialism.

00:12:43 I don’t know that there are dogs walking around

00:12:46 who’ve developed an understanding

00:12:48 of the general theory of relativity.

00:12:49 I mean, maybe we’re wrong,

00:12:50 but that seems the best explanation.

00:12:54 What do you think is more special,

00:12:55 intelligence or consciousness?

00:12:57 I think consciousness.

00:12:59 And I think that there’s a deep connection

00:13:02 between these ideas.

00:13:03 They are distinct, but they’re deeply connected.

00:13:06 But look, I mean, to me and to, of course, many philosophers

00:13:10 who actually coined a name for this,

00:13:11 the hard problem of consciousness,

00:13:13 David Chalmers and others,

00:13:15 as a physicist, I look out at the world

00:13:17 and I see it’s particles governed by physical law.

00:13:23 We can name them.

00:13:24 We got electrons, we got quarks

00:13:27 that come in various flavors and so forth.

00:13:29 We have a list of ingredients that science has revealed

00:13:33 and we have a list of laws that seemingly

00:13:36 govern those ingredients.

00:13:37 And nowhere in there is there even a hint

00:13:41 that when you put those particles together in the right way,

00:13:45 an inner world should turn on.

00:13:48 And it’s not only that there’s no hint, it’s insane.

00:13:52 I mean, it’s ridiculous.

00:13:53 How could it be that a thoughtless,

00:13:56 passionless, emotionless particle,

00:14:00 when grouped together with compatriots,

00:14:03 somehow can yield something so deeply foreign

00:14:07 to the nature of the ingredients themselves?

00:14:09 So answering that question,

00:14:12 I think is among the deepest

00:14:14 and most difficult questions that we face.

00:14:17 Do you think it is in fact a really hard problem?

00:14:23 Or is it possible, I think you mentioned in your book,

00:14:28 that it’s just like almost like a side effect.

00:14:30 It’s an emergent thing that’s like, oh, it’s nice.

00:14:33 It’s like a nice little feature.

00:14:34 Yeah.

00:14:35 Well, I mean, when people use the phrase hard problem,

00:14:38 I mean, they mean in a somewhat technical sense

00:14:40 that it’s trying to explain something

00:14:44 that seems fundamentally unavailable

00:14:47 to third party objective analysis, right?

00:14:53 I’m the only one that can get inside my head

00:14:55 and I can tell you a lot about what’s happening

00:14:57 inside my head right now, it’s reflected

00:14:59 in what I’m saying, and you can try to deduce things

00:15:02 about what’s going on inside my head,

00:15:03 but you don’t have access to it in the way that I do.

00:15:06 And so it seems like a fundamentally different

00:15:08 kind of problem from the ones that we have successfully

00:15:12 dealt with over the course of centuries in science,

00:15:14 where we look at the motion of the moon,

00:15:15 everybody can look, everybody can measure it.

00:15:18 We look at the properties of hydrogen

00:15:20 when you shine lasers on it,

00:15:22 everybody can look at the data and understand it.

00:15:25 And so it seems like a fundamentally different problem

00:15:29 in that sense, it seems like it is hard

00:15:32 relative to the others, but I do think ultimately

00:15:35 that the explanation will be, as you recount,

00:15:38 I think that a hundred years from now,

00:15:41 or maybe it’s a thousand, it’s hard to predict

00:15:43 the timescale for developments,

00:15:45 but I think we’ll get to a place where we’ll look back

00:15:48 and kind of smile at those folks in the 20th century

00:15:53 and before, 21st century and before,

00:15:55 who thought consciousness was so incredibly mysterious

00:15:59 when the reality of it is, eh, it’s just a thing that happens

00:16:03 when particles come together.

00:16:05 And however mysterious that feels right now,

00:16:10 I think for instance, when we start to build

00:16:12 conscious systems, things that you’re more familiar with

00:16:15 than I am, when we start to build these artificial systems

00:16:19 and those systems report to us, I’m feeling sad,

00:16:23 I’m feeling anxious, yeah, there’s a world going on

00:16:25 inside here, I think the mystery of consciousness

00:16:28 will just begin to evaporate.

00:16:30 Well, that’s, first of all, beautifully put,

00:16:33 and I agree with you completely,

00:16:35 just the way you said it, it’ll begin to evaporate.

00:16:38 I have built quite a few robots

00:16:41 and have had them do emotion, emotional type things,

00:16:47 and it’s immediate that exactly what you’re saying,

00:16:49 this kind of mystery of consciousness starts to evaporate,

00:16:52 that the kind of need to truly understand,

00:16:57 to solve the hard problem of consciousness disappears,

00:17:00 because, well, I don’t really care if I understand

00:17:05 what can solve the hard problem of consciousness.

00:17:07 That thing sure as heck looks conscious.

00:17:09 I feel like that way when I interact with a dog.

00:17:12 I don’t need to solve the problem of consciousness

00:17:16 to be able to interact and richly enjoy the experience

00:17:22 with this other living being.

00:17:24 Obviously, same thing with other humans.

00:17:26 I don’t need to fully understand it.

00:17:27 And there’s some aspect, maybe this is a little bit

00:17:31 too engineering focused, but there’s some aspect

00:17:33 in which it feels like consciousness is just a nice trick

00:17:38 to help us communicate with each other.

00:17:41 It sounds ridiculous to say, but sort of the ability

00:17:47 to experience the world is very useful,

00:17:51 in a subjective sense, is very useful to put yourself

00:17:55 in that world and to be able to describe the experience

00:17:58 to others.

00:17:59 It could be just a social and the merge.

00:18:01 Obviously, animals, the sort of more primitive animals

00:18:04 might experience consciousness in some more primitive way,

00:18:08 but this kind of rich, subjective experience

00:18:12 that we think about as humans, I think it’s probably

00:18:14 deeply coupled with language and poetry.

00:18:17 Yeah, that resonates with my view as well.

00:18:20 I mean, there’s a scientist, maybe you’ve spoken to him,

00:18:23 Michael Graziano from Princeton.

00:18:25 Yeah, he’s developed ideas of consciousness that,

00:18:29 look, I don’t think they solve the problem,

00:18:31 but I think they do illuminate it in an interesting way

00:18:34 where basically we are not aware

00:18:39 of all the underlying physiochemical processes

00:18:43 that make our brains and our inner worlds

00:18:45 tick the way they do.

00:18:48 And because of that dissociation between sensation

00:18:52 and the physics of it and the chemistry of it

00:18:55 and the biology of it, it feels like our minds

00:18:58 and our inner worlds are just untethered,

00:19:00 like floating somewhere in this gray matter

00:19:04 inside of our heads.

00:19:06 And the way I like to think of it is like,

00:19:08 look, if you were in a dark room, right,

00:19:13 and I had glow in the dark paint on my fingers,

00:19:17 so all you saw was my fingers dancing around,

00:19:20 there’d be something mysterious.

00:19:21 How could those fingers be doing that?

00:19:24 And then you turn on the light, you realize,

00:19:25 oh, there’s this arm underlying it,

00:19:27 and that’s the deep physical connection explains it all.

00:19:30 And I think that’s what we’re missing,

00:19:32 the deep physical connection between what’s happening

00:19:35 up here and what is responsible for it

00:19:38 in a physical, chemical, biological way.

00:19:41 And so to me, that at least gives me some understanding

00:19:43 of why consciousness feels so mysterious

00:19:46 because we are suppressing all of the underlying science

00:19:51 that ultimately is responsible for it.

00:19:53 And one day we will reveal that more fully,

00:19:55 and I think that will help us tether this experience

00:19:59 to something quite tangible in the world.

00:20:01 I wonder if the mystery is an important component

00:20:08 of enjoying something.

00:20:10 So once we know how this thing works,

00:20:14 maybe we will no longer enjoy this conversation.

00:20:19 We’ll seek other sources of enjoyment,

00:20:21 but this is, again, from an engineering perspective,

00:20:25 I wonder if the mystery is an important component.

00:20:29 Well, have you ever seen,

00:20:31 there’s this beautiful interview

00:20:33 that Richard Feynman did,

00:20:36 great Nobel laureate physicist responsible

00:20:39 for a lot of our understanding of quantum mechanics,

00:20:42 quantum field theory and so forth.

00:20:43 And he was in a conversation with an interviewer

00:20:46 where he noted that some people feel

00:20:48 like once the mystery is gone,

00:20:51 once science explains something,

00:20:55 the beauty goes away, the wonder of it goes away.

00:20:58 And he was emphasizing in his response to that,

00:21:02 he’s like, no, that’s not the right way of thinking about it.

00:21:05 He says, look, when I look at a rose,

00:21:07 he says, yeah, I can still deeply enjoy the aroma,

00:21:11 the color, the texture.

00:21:13 He says, but what I can do that you can’t,

00:21:15 if you’re not a physicist,

00:21:16 I can look more deeply and understand

00:21:19 where the red comes from, where the aroma comes from,

00:21:21 where the structure comes from.

00:21:22 He says, that only augments my wonder.

00:21:27 It only augments my experience.

00:21:29 It doesn’t flatten it or take away from it.

00:21:32 So I sort of take that as a bit of a motto in some sense

00:21:38 that there is a wonder that comes from a kind of ignorance.

00:21:43 And I don’t mean that in a derogatory sense,

00:21:45 but just from not knowing.

00:21:47 So there is a wonder that comes from mystery.

00:21:49 There’s another kind of wonder that comes from knowing

00:21:53 and deep knowing.

00:21:55 And I think that kind of wonder has its own

00:21:59 special character that in some ways can be more gratifying.

00:22:04 I hope he’s right.

00:22:06 I hope you’re right.

00:22:07 But there’s also, I remember he said something

00:22:10 about like science is an onion or something like that.

00:22:13 You can peel back, you can keep peeling back.

00:22:16 I mean, there is also, when you understand something,

00:22:19 there’s always a sense that there’s more mystery

00:22:22 to understand.

00:22:23 Like you never get to the bottom of the mystery.

00:22:27 But I think it’s also different than,

00:22:28 you know, I don’t think you can analogize say

00:22:31 to a magician, right?

00:22:33 A magician does some trick.

00:22:35 You learn how it sounds like, oh my God,

00:22:37 that’s ridiculous when you find.

00:22:39 But nature is perhaps the best magician

00:22:42 if you wanna try to make the analogy there

00:22:45 because when you peel things back and you understand

00:22:48 how it is that things have color and you have electrons,

00:22:53 dancing from one orbital to another,

00:22:56 emitting photons at very particular wavelengths

00:22:59 that are described by these beautiful equations

00:23:01 of quantum electrodynamics,

00:23:03 part of which that Feynman developed,

00:23:06 it gives you a greater sense of awe

00:23:09 when the curtain is pulled back

00:23:11 than what happens in other circumstances

00:23:14 where it does flatten it completely.

00:23:16 Yeah, it’s very possible then say in physics

00:23:18 that we arrive at a theory of everything

00:23:21 that unifies the laws of physics

00:23:23 and has a very strong understanding

00:23:25 of the fabric of reality,

00:23:26 even like from the big bang to today,

00:23:30 it’s possible that that understanding

00:23:33 is only going to elevate our appreciation

00:23:36 of this whole thing.

00:23:37 Yeah, I think it will.

00:23:38 I think it will.

00:23:39 I mean, I think it has so far.

00:23:40 But the other side of it which you emphasize

00:23:43 is it’s not like science somehow reaches an end, right?

00:23:48 There are certain categories of questions

00:23:50 that do reach an end.

00:23:52 I think we one day will close the book

00:23:54 on nature’s ingredients and the fundamental laws.

00:23:57 Now that we can’t prove that,

00:23:58 maybe it goes on forever, smaller and smaller,

00:24:01 maybe there are deeper and deeper laws,

00:24:03 but I don’t think so.

00:24:03 I think that there’s going to be a collection

00:24:06 of ingredients and a collection of basic laws.

00:24:08 That chapter will close, but it’s one chapter.

00:24:12 Now we take that knowledge and we try to understand

00:24:16 how the world builds the structures that it does,

00:24:19 from planets to people to black holes

00:24:23 to the possibility of other universes

00:24:25 and every step of the way,

00:24:27 the collection of questions

00:24:29 that we don’t know the answer to only blossoms.

00:24:32 And so there’s a deep sense of gratification

00:24:36 from understanding certain qualities of the world.

00:24:39 But I would say that if you take a ratio

00:24:42 of what we understand to the things that we know

00:24:45 that we don’t yet understand,

00:24:47 that ratio keeps getting smaller and smaller

00:24:50 because the things that we know that we don’t understand

00:24:52 grows larger and larger.

00:24:54 Do you have a hope that we solve that theory

00:24:56 of everything puzzle in the next few decades?

00:25:00 So there’s been a bunch of attempts from string theory

00:25:03 to all kinds of attempts at trying to solve quantum gravity

00:25:07 or basically come up with a theory for quantum gravity.

00:25:10 There’s a lot of complexities to this.

00:25:13 One, for experimental validation,

00:25:16 you have to observe effects

00:25:17 that are very difficult to measure.

00:25:20 So you have to build,

00:25:21 like that’s like an engineering challenge.

00:25:23 And then there’s the theory challenge,

00:25:25 which is like, it seems very difficult

00:25:28 to connect the laws of gravity to quantum mechanics.

00:25:31 Do you have a hope or are we hopelessly stuck?

00:25:35 Well, I have to have to have a hope.

00:25:37 I mean, it’s in some sense,

00:25:39 but I devote at least part of my professional life toward

00:25:43 trying to make progress on.

00:25:45 And I’m glad you used the phrase quantum gravity.

00:25:47 I’m not a great fan of the theory of everything phrase

00:25:50 because it does make other scientists feel like

00:25:53 if they’re not working on this, what are they working on?

00:25:55 Man’s like, there’s not much left

00:25:57 when you’re talking about theory of everything.

00:25:58 Biology is just small details we’ll figure out.

00:26:01 Yeah, so it is really trying to put gravity

00:26:04 and quantum mechanics together.

00:26:06 And since I was a college kid,

00:26:08 I was deeply fascinated with gravity.

00:26:12 And as I learned quantum mechanics,

00:26:15 the notion of physicists being stumped

00:26:19 and trying to blend them together,

00:26:20 how could one not get fired up

00:26:22 about maybe contributing something to that journey?

00:26:25 And so we’ve been on this,

00:26:27 I’ve been on this for 30 years since I was a student.

00:26:29 We have made progress.

00:26:31 We do have ideas.

00:26:32 You mentioned string theory is one possible scenario.

00:26:36 It’s not stuck.

00:26:37 String theory is a vibrant field of research

00:26:40 that is making incredible progress,

00:26:43 but we’ve not made progress

00:26:45 on this issue of experimental verification validation,

00:26:49 which is, you know, it is a vital part of the story.

00:26:53 So I would have hoped that by now

00:26:55 we would have made contact with observation.

00:26:58 If you would have interviewed me back in the 80s

00:27:01 when I was, you know, a wild bright eyed kid

00:27:04 trying to make headway working 18 hours a day

00:27:07 and this sort of stuff,

00:27:07 I would have said, yeah, by 2021,

00:27:10 yeah, we’re gonna know whether it’s right or wrong.

00:27:12 We’ll have made contact.

00:27:13 I would have said, look,

00:27:14 there may be certain mathematical puzzles

00:27:16 that we’ve yet to work out,

00:27:17 but we’ll know enough to make contact with experiment.

00:27:19 That has not happened.

00:27:21 On the other hand,

00:27:22 if you would have interviewed me back then and asked me,

00:27:25 will we be able to talk about detailed qualities

00:27:29 of black holes and understand them at the level of detail

00:27:34 that we actually, I would have said,

00:27:37 no, I don’t think that we’re gonna be able to do that.

00:27:39 Will we have an exact formulation of string theory

00:27:42 in certain circumstances?

00:27:43 No, I don’t think we’re gonna have that, and yet we do.

00:27:46 So it’s just to say,

00:27:47 you don’t know where the progress is going to happen,

00:27:51 but yes, I do hold out hope

00:27:52 that maybe before I move on to wherever,

00:27:56 I don’t think there is an after,

00:27:58 but I would love before I leave this earth

00:28:01 to know the answer, but science and the universe,

00:28:06 it’s not about pleasing any individual, it is what it is.

00:28:11 And so we just press onward and we’ll see where it goes.

00:28:15 So in terms of string theory,

00:28:17 if I just look from an authoritative perspective currently

00:28:20 at the theoretical physics community,

00:28:22 string theory as a theory has been very popular

00:28:26 for a few decades, but has recently fallen out of favor,

00:28:30 or at least there’s been like, you know,

00:28:32 it became more popular to kind of ask the question,

00:28:36 is string theory really the answer?

00:28:39 Where do you fall on this?

00:28:40 Like, how do you make sense of this puzzle?

00:28:43 Why do you think it’s fallen out of favor?

00:28:45 Yeah, so I would actually challenge the statement

00:28:47 that it’s fallen out of favor.

00:28:50 I would say that any field of research when it’s new

00:28:55 and it’s the bright, shiny bicycle

00:28:58 that no one has yet seen on that block,

00:29:01 yeah, it’s gonna attract attention

00:29:03 and the news outlets are gonna cover it

00:29:06 and students are gonna flock to it, sure.

00:29:09 But as a field matures, it does shed those qualities

00:29:14 because it’s no longer as novel as it was

00:29:17 when it was first introduced 30, 40 years ago,

00:29:20 but you need to judge it by a different standard.

00:29:22 You need to judge it by is it making progress

00:29:26 on foundational issues deepening our understanding

00:29:29 of the subject and by that measure,

00:29:31 string theory is scoring very high.

00:29:36 Now, at the same time, you also need to judge

00:29:39 whether it makes contact with experiment

00:29:41 as we discussed before too

00:29:42 and in that measure, we’re still challenged.

00:29:45 So I would say that many string theorists,

00:29:49 myself included, are very sober about the theory.

00:29:54 It has the tremendous progress that it had 30, 40 years ago

00:29:58 that hasn’t gone away, but we become better equipped

00:30:02 at assessing the long journey ahead

00:30:06 and that was something that we weren’t particularly good at

00:30:09 back, say, in the 80s.

00:30:10 Look, when I was just starting out in the field,

00:30:13 there was a sense of physics is about to end.

00:30:18 String theory is about to be the be all and end all

00:30:21 final unified theory and that will bring this chapter

00:30:26 to a close.

00:30:27 Now, I have to say, I think it was more the younger

00:30:30 physicists who were saying that.

00:30:31 Some of them were seasoned,

00:30:32 even if they were pro string theory at the time.

00:30:35 I don’t know if they were rolling their eyes,

00:30:37 but they knew that it was gonna be a long, long journey.

00:30:41 I think people like John Schwartz,

00:30:43 one of the founders of string theory,

00:30:45 Michael Green, no relation to me,

00:30:46 founders of the theory, Edward Witten,

00:30:49 one of the main people driving the theory

00:30:52 back then and today.

00:30:53 I think they knew that we were in for a long haul

00:30:58 and that’s the nature of science,

00:31:01 quick hits that resolve everything few and far between.

00:31:06 And so if you were in for the quick solution

00:31:12 to the big questions of the world,

00:31:13 then you would have been disappointed

00:31:15 and I think there were people who were disappointed

00:31:16 and moved on and work on other subjects.

00:31:19 If you’re in in the way that Einstein was in

00:31:23 for a lifetime of investigation to try to see

00:31:27 what the answers to the deep questions would be,

00:31:30 then I think string theory has been a rich source

00:31:33 of material that has kept so many people deeply engaged

00:31:39 in moving the frontier forward.

00:31:41 There’s a few qualities about string theory,

00:31:43 which are weird.

00:31:45 I mean, a lot of physics is just weird and beautiful.

00:31:48 So let me ask the question,

00:31:50 what do you use most beautiful about string theory?

00:31:53 Well, what attracted me to the theory at the outset

00:31:57 beyond it’s putting gravity and quantum mechanics together,

00:32:00 which I think is its true claim to fame,

00:32:03 at least on paper, it’s able to do that.

00:32:06 What attracted me to the theory was the fact

00:32:08 that it requires extra dimensions of space.

00:32:11 And this was an idea that intrigued me in a very deep way,

00:32:16 even before I really understood what it meant.

00:32:20 I somehow had, I mean, talk about sort of

00:32:24 the emotional part of consciousness and the cognitive part

00:32:27 in some, perhaps you call it strange,

00:32:29 in some strange emotional way,

00:32:31 I was enamored with Einstein’s general relativity,

00:32:35 the idea of curved space and time

00:32:37 before I really knew what it meant.

00:32:39 It just spoke to me, I don’t know how else to say it.

00:32:43 And then when I subsequently learned

00:32:46 that people had thought about more dimensions of space

00:32:49 than we can see and how those extra dimensions

00:32:52 would be vital to a deep understanding

00:32:55 of the things that we do see in this world,

00:32:56 four, five, six dimensions might explain

00:32:59 why there are certain forces and particles

00:33:01 and how they behave.

00:33:03 To me, this was like amazing, utterly amazing.

00:33:06 And then when I learned that string theory

00:33:09 embraced all these ideas,

00:33:10 embraced the general theory of relativity,

00:33:12 embraced quantum mechanics,

00:33:13 embraced the possibility of extra dimensions,

00:33:17 then I was hooked.

00:33:19 And so when I was a graduate student,

00:33:21 we would just spend hours,

00:33:23 we, I mean, a couple of other graduate students and myself

00:33:26 who had sort of worked really well together,

00:33:29 it was at Oxford in England,

00:33:30 we would work these enormous numbers of hours a day

00:33:33 trying to understand the shapes of these extra dimensions,

00:33:36 the geometry of them, what those geometrical shapes

00:33:39 for the extra dimensions would imply

00:33:41 for things that we see in the world around us.

00:33:43 And it was a heady, heady time.

00:33:46 And that kind of excitement has sort of filtered through

00:33:50 over the decades.

00:33:51 But I’d say that’s really the part of the theory

00:33:57 that I think really hooked me most strongly.

00:34:00 How are we supposed to think about those extra dimensions?

00:34:02 I was supposed to imagine actual physical reality

00:34:05 or is this more in the space of mathematics

00:34:08 that allows you to sort of come up with tricks

00:34:11 to describe the four dimensional reality

00:34:14 that we more directly perceive?

00:34:17 No one really knows the answer, of course,

00:34:19 but if I take the most straightforward approach

00:34:22 to string theory,

00:34:23 you really are imagining that these dimensions are there,

00:34:28 they’re real.

00:34:28 I mean, just as you would say

00:34:30 that the three space dimensions around us,

00:34:33 left, right, back, forth, up, down,

00:34:35 yeah, they’re real, they’re here.

00:34:37 We are immersed within those dimensions.

00:34:40 These other dimensions are as real as these

00:34:44 with the one difference being their shape and their size

00:34:47 differs from the shape and size of the dimensions

00:34:50 that we have direct access to through human experience.

00:34:54 And one approach imagines that these extra dimensions

00:34:57 are tightly coiled up, curled up,

00:35:01 crushed together, if you will,

00:35:03 into a beautiful geometrical form

00:35:06 that’s all around us,

00:35:08 but just too small for us to detect with our eyes,

00:35:11 too small for us to detect

00:35:13 even with the most powerful equipment that we have.

00:35:16 Nevertheless, according to the mathematics,

00:35:18 the size and the shape of those extra dimensions

00:35:21 leaves an imprint in the world that we do have access to.

00:35:24 So one of the ways that we have hoped yet to achieve

00:35:28 to make contact with experimental physics

00:35:31 is to see a signature of those extra dimensions

00:35:34 in places like the Large Hadron Collider

00:35:36 in Geneva, Switzerland.

00:35:38 And it hasn’t happened yet, doesn’t mean it won’t happen,

00:35:41 but that would be a stunning moment

00:35:44 in the history of the species

00:35:46 if data that we acquired in these dimensions

00:35:50 gives us kind of incontrovertible evidence

00:35:53 that these dimensions are not the only dimensions.

00:35:55 I mean, how mind blowing would that be?

00:35:59 So with the Large Hadron Collider,

00:36:00 it would be something in the movement of the particles

00:36:03 or also the gravitational waves potentially be a place

00:36:07 where you can detect signs of multiple dimensions,

00:36:10 like with something like LIGO, but much more accurate.

00:36:12 In principle, all of these can work.

00:36:14 So one of the experiments that we had high hopes for,

00:36:18 but by high hopes, I’m actually exaggerating.

00:36:20 One of the experiments that we imagined

00:36:24 might in the best of all circumstances,

00:36:26 yield some insight.

00:36:27 We weren’t with bated breath waiting for the result.

00:36:30 We knew it was a long shot.

00:36:31 When you slam protons together at very high speed

00:36:34 of the Large Hadron Collider,

00:36:35 if there are these extra dimensions

00:36:37 and if they have the right form,

00:36:39 and that’s a hypothesis that may not be correct,

00:36:43 but when the protons collide,

00:36:44 they can create debris, energetic debris

00:36:48 that can in some sense leave our dimensions

00:36:50 and insert itself into the other dimensions.

00:36:53 And the way you’d recognize that is,

00:36:56 there’d be more energy before the collision

00:36:58 and after the collision because the debris

00:37:00 would have taken energy away from the place

00:37:03 where our detectors can detect it.

00:37:06 So that’s one real concrete way

00:37:09 that you could find evidence for extra dimensions.

00:37:12 But yeah, since extra dimensions are of space

00:37:16 and gravity is something that exists within,

00:37:19 in fact is associated with the shape of space,

00:37:22 gravitational waves in principle

00:37:25 can provide a kind of cat scan of the extra dimensions

00:37:31 if you had sufficient control over those processes.

00:37:35 We don’t yet, but perhaps one day we will.

00:37:38 Does it make you sad a little bit?

00:37:41 Maybe looking out into the future,

00:37:43 you mentioned Ed Witten that no Nobel prizes

00:37:46 have been given yet related to string theory.

00:37:48 Do you think they will be?

00:37:50 Do you think you have to have experimental validation

00:37:53 or can a Nobel prize be given?

00:37:55 Which I don’t think has been given for quite a long time

00:37:58 for purely sort of theoretical contribution.

00:38:01 Yeah, it’s certainly as a matter of historical precedent

00:38:06 has been the case that those who win the prize

00:38:09 have established, investigated, illuminated

00:38:14 a demonstrably real quality of the world.

00:38:18 So gravitational waves, the prize was awarded

00:38:22 after they were detected, not the mathematics of it,

00:38:26 but the actual detection of it.

00:38:28 The Higgs particle, it was an idea that came

00:38:32 from the 1960s, Peter Higgs and others in fact.

00:38:36 And it wasn’t until 2012 on July 4th

00:38:41 when the announcement came that this particle

00:38:43 had been detected at the Large Hadron Collider

00:38:45 that people viewed it as eligible for the Nobel prize.

00:38:49 The idea was there, the math was there,

00:38:50 but you needed to confirm it.

00:38:52 Indeed, the prize ultimately was awarded.

00:38:55 So I’m not surprised.

00:38:56 In fact, I would have been surprised

00:38:59 if a Nobel prize had been awarded

00:39:02 in the arena of string theory

00:39:04 because it’s far too speculative right now.

00:39:07 It’s far too hypothetical.

00:39:09 In fact, I am sympathetic to the view

00:39:13 that it really shouldn’t be called string theory.

00:39:15 It degrades the word theory

00:39:18 because theory in science, of course,

00:39:20 means the best available explanation

00:39:23 for the things that we observe in the world,

00:39:25 the things that we measure in experiments about the world.

00:39:30 And string theory does not do that, at least not yet.

00:39:34 So it really should be the string hypothesis, right?

00:39:37 We’re at an earlier stage of development

00:39:40 and that’s not the kind of thing

00:39:42 that Nobel prizes should be awarded for.

00:39:45 What do you think about the critics out there, Peter White,

00:39:48 he’s from Columbia too, I think Sabine Hafenstatter.

00:39:53 Is that a healthy thing or should we sort of focus

00:39:56 on sort of the optimism of these hypotheses?

00:39:59 Yeah, it’s actually a good way that you frame it

00:40:03 because I’m always somewhat repelled

00:40:09 by views of the world that start from the negative.

00:40:14 Try to cut down an idea, try to say that’s the wrong way

00:40:18 of thinking about things and so on.

00:40:21 I’m much more drawn, maybe because I’m an optimist,

00:40:24 I don’t know, I’m much more drawn to those

00:40:27 who go out into the world with new ideas.

00:40:30 And don’t try to cut down one idea,

00:40:34 but rather present another one that might be better.

00:40:38 And so you make the first idea, maybe string theory irrelevant

00:40:41 because you’ve come up with the better approach

00:40:46 to the world.

00:40:47 So do I think it’s healthy?

00:40:49 Look, I think having a wide range of views

00:40:53 and perspectives is generally a healthy thing.

00:40:56 I think it’s good to have arguments within a subject

00:41:00 in order that you stay fresh and you stay focused

00:41:04 on the things that matter.

00:41:06 But in the end of the day,

00:41:07 I think it’s a more vital contribution

00:41:11 to give us something new

00:41:13 rather than to criticize something that’s there.

00:41:15 Yeah, I’m totally with you.

00:41:17 But it could be just the nature of being an optimist

00:41:19 and also just a love of engineering.

00:41:24 It helps nobody by criticizing the rocket

00:41:29 that somebody else built,

00:41:30 just build a bigger, cheaper, better rocket.

00:41:34 Right, exactly.

00:41:36 And that seems to be how human civilization

00:41:38 can progress effectively.

00:41:41 We’ve mentioned the second law of thermodynamics.

00:41:44 I gotta ask you about time.

00:41:46 Yeah.

00:41:47 And do you think of time as emergent

00:41:51 or fundamental to our universe?

00:41:53 I like to think of it as emergent.

00:41:56 I don’t have a solid reason for that perspective.

00:42:00 I have a lot of hints of reasons

00:42:02 that some of which come out of string theory

00:42:04 and quantum gravity that perhaps would be worth talking about.

00:42:09 But what I would say is,

00:42:11 time is the most familiar quality of experience

00:42:17 because there’s nothing that takes place

00:42:18 that doesn’t take place within an interval of time.

00:42:22 And yet at the same time,

00:42:24 it is perhaps the most mysterious quality of the world.

00:42:28 So it’s a wonderful confluence

00:42:31 of the familiar and the deeply mysterious

00:42:33 all in one little package.

00:42:35 If you were to ask me, what is time?

00:42:38 I don’t really know.

00:42:39 I don’t think anybody does.

00:42:41 I can say what time gives us,

00:42:45 it allows us the language for talking about change.

00:42:48 It allows us to envision the events of the universe

00:42:52 being spread out in this temporal timeline.

00:42:55 And in that way, allows us to see the patterns

00:42:59 that unfold within time.

00:43:01 I mean, time allows us the structure and the organization

00:43:05 to think about things in that kind of a progression.

00:43:08 But what actually is it?

00:43:11 I don’t really know.

00:43:12 And that’s so strange because we can measure it, right?

00:43:16 I mean, there are laboratories in the world

00:43:19 that measure this thing called time

00:43:21 to spectacular precision.

00:43:24 But if you go up to the folks and say,

00:43:28 what is it that you’re actually measuring?

00:43:31 I don’t know that they can really articulate

00:43:34 the kind of answer that you would expect

00:43:37 from those who are engineering a device

00:43:39 that can measure something called time

00:43:41 to that level of precision.

00:43:43 So it’s a very curious combination.

00:43:46 What do you make of the one way feeling of causality?

00:43:51 Like is causality a thing or is that too just a human story

00:43:56 that we put on top of this emergent phenomenon of time?

00:44:00 I don’t know.

00:44:02 I can give you my guess and my intuition about it.

00:44:05 I do think that at the macroscopic level,

00:44:09 if we’re talking about sort of the human experience of time,

00:44:11 I do think at the macroscopic level,

00:44:13 there is a fundamental notion of causality

00:44:17 that does emerge from a starting point

00:44:20 that may not have causality built in.

00:44:21 So I certainly would allow that at the deepest description

00:44:25 of reality when we finally have that on the table,

00:44:28 we may not see causality directly at that fundamental level.

00:44:33 But I do believe that we will understand

00:44:36 how to go from that fundamental level

00:44:38 to a world where at the macroscopic level,

00:44:41 there is this notion of A causes B.

00:44:44 A notion that Einstein deeply embraced

00:44:47 in his special theory of relativity

00:44:49 where he showed that time has qualities

00:44:51 that we wouldn’t expect based on experience.

00:44:54 You and I, if we move relative to each other,

00:44:56 our clocks tick off time at different rate.

00:44:59 And our clocks is just a means of measuring

00:45:02 this thing called time.

00:45:03 So this is really time that we’re talking about.

00:45:05 Time for you and time for me are different

00:45:08 if we’re in relative motion.

00:45:09 He then shows in the general theory of relativity

00:45:11 that if we’re experiencing different gravity,

00:45:15 different gravitational fields

00:45:16 or actually more precisely

00:45:17 different gravitational potentials,

00:45:19 time will elapse for us at different rates.

00:45:21 These are things that are astoundingly strange

00:45:25 that give rise to a scientific notion of time travel.

00:45:29 Okay, so this is how far Einstein took us

00:45:33 in wiping away the old understanding of time

00:45:37 and injecting a new understanding of its qualities.

00:45:40 So there’s so much about time that’s counterintuitive,

00:45:44 but I do not think that we’re ever going

00:45:46 to wipe away causality at the macroscopic level.

00:45:50 At the macroscopic, I mean, there’s so many interesting

00:45:52 things at the macroscopic level

00:45:53 that may only exist at the macroscopic level.

00:45:56 Like we already talked about consciousness

00:45:59 that very well could be one of the things.

00:46:01 You mentioned time travel.

00:46:02 So, I mean, according to Einstein and in general,

00:46:09 what types of travel do you think

00:46:11 our physical universe allows?

00:46:14 Well, it certainly allows time travel to the future.

00:46:17 And I’m not talking about the silly thing

00:46:18 that you and I are now going into the future

00:46:21 second by second by second.

00:46:22 I’m talking about really the diversion

00:46:24 that you see in Hollywood, at least in terms

00:46:27 of its net effect, whereby an individual

00:46:32 can follow an Einsteinian strategy

00:46:36 and propel themselves into the future

00:46:40 in some sense more quickly.

00:46:42 So if I wanted to see what’s happening on planet Earth

00:46:46 one million years from now, Einstein tells me

00:46:50 how to get one million years from now.

00:46:52 Build a ship.

00:46:53 I got to turn to guys who know how to build stuff.

00:46:56 I can’t do it like you.

00:46:57 Build a ship that can go out into the universe

00:47:00 near the speed of light, turn around and come back.

00:47:02 Let’s say it’s a six month journey out

00:47:04 and a six month journey back.

00:47:05 And Einstein tells me how fast I need to travel,

00:47:09 how close to the speed of light I need to go

00:47:11 so that when I step out of my ship,

00:47:13 it will now be one million years into the future

00:47:16 on planet Earth.

00:47:20 And this is not a controversial statement, right?

00:47:23 This is not something where there’s differences

00:47:25 of opinion in the scientific community.

00:47:28 Any scientist who knows anything

00:47:30 about what Einstein taught us agrees with what I just said.

00:47:35 It’s commonplace, it’s bread and butter physics.

00:47:37 And so that kind of travel to the future

00:47:40 is absolutely allowed by the laws of physics.

00:47:44 There are engineering challenges,

00:47:45 there are technological challenges.

00:47:47 They’re close to the speed of light part, yeah.

00:47:49 Yeah, and there are even biological challenges, right?

00:47:52 They’re G forces that you’re gonna experience.

00:47:55 So there’s all sorts of stuff embedded in this,

00:47:57 but those I will call the details.

00:48:01 And those details, notwithstanding,

00:48:04 the universe allows this kind of travel to the future.

00:48:07 And if I could pause real quick,

00:48:09 you could also, at the macro level,

00:48:12 with biology extend the human lifespan

00:48:15 to do a kind of travel forward in time.

00:48:19 If you expand how long we live,

00:48:22 that’s a way to, from a perspective of an observer,

00:48:25 a conscious observer that is a human being,

00:48:27 you’re essentially traveling forward in time

00:48:29 by allowing yourself to live long enough to see the thing.

00:48:32 So that’s in the space of biology.

00:48:34 What about traveling back in time?

00:48:37 Yeah, that is a natural next question,

00:48:41 especially if you’re going on one of these journeys.

00:48:45 Is it a one way journey or can you come back?

00:48:48 And the physics community doesn’t speak

00:48:52 with a unified voice on this as yet,

00:48:55 but I would say that the dominant perspective

00:48:57 is that you cannot get back.

00:49:00 Now, having said that, there are proposals

00:49:03 that serious people have written papers on

00:49:07 regarding hypothetical ways

00:49:09 in which you could travel to the past.

00:49:10 And we’ve seen some of these.

00:49:13 Again, Hollywood loves to take the most sexy ideas

00:49:16 of physics and build narratives around them.

00:49:20 This idea of a wormhole,

00:49:21 like Jodie Foster in Contact went through a wormhole,

00:49:25 Deep Space Nine Star,

00:49:26 I’m sure there are many other examples

00:49:27 for these ideas that I’ve probably never even seen.

00:49:30 But with wormholes, there’s at least a proposal

00:49:34 of how you could take a wormhole tunnel through space time,

00:49:38 manipulate the openings of the wormhole

00:49:40 in such a way that the openings are no longer synchronous.

00:49:44 They are out of sync relative to each other,

00:49:46 which would mean one’s ahead and one’s behind,

00:49:48 which means if you go through one direction,

00:49:50 you travel to the future.

00:49:51 If you go back, you travel to the past.

00:49:54 Now, we don’t know if there are wormholes in the world.

00:49:57 But they’re possible according to Einstein, correct?

00:49:59 They are possible according to Einstein.

00:50:01 But even Einstein was very quick to say,

00:50:04 just because my math allows for something,

00:50:07 doesn’t mean it’s real.

00:50:08 I mean, he famously didn’t even believe in black holes.

00:50:10 Didn’t believe in the Big Bang, right?

00:50:12 And yet the black hole issue has really been settled now.

00:50:17 We have radio telescopic photographs

00:50:20 of the black hole in M87.

00:50:22 It was in newspapers around the world

00:50:25 just a couple of years ago.

00:50:26 So it’s just to say that just because it’s in Einstein’s math,

00:50:31 it doesn’t mean it’s real.

00:50:32 But yes, it is the case that wormholes

00:50:35 are allowed by Einstein’s equations.

00:50:36 And in principle, you can imagine, you know,

00:50:39 putting electric charges on the openings of the wormhole,

00:50:42 allowing you to tow them around

00:50:44 in a manner that could yield

00:50:45 this temporal asymmetry between them.

00:50:48 Maybe you tow one of the mouths to the edge of a black hole.

00:50:51 In principle, you can do this,

00:50:53 slowing down the passage of time near that black hole.

00:50:56 And then when you bring it back,

00:50:58 it will be well out of sync with the other opening

00:51:02 and therefore could be a significant temporal gap

00:51:05 between one and the other.

00:51:07 But people who study this in more detail question,

00:51:10 could you ever keep a wormhole open,

00:51:13 assuming it does exist?

00:51:14 Could you ever travel through a wormhole

00:51:17 or would there be a requirement

00:51:19 to some kind of exotic matter to prop it open

00:51:22 that perhaps doesn’t exist?

00:51:24 So there are many, many issues that people have raised.

00:51:28 And I would say that the general sentiment

00:51:31 is that it’s unlikely that this kind of scenario

00:51:34 is going to survive our deeper understanding of physics

00:51:37 when we finally have it.

00:51:39 But that doesn’t mean that the door is closed.

00:51:41 So maybe there’s a small possibility

00:51:44 that this could one day be real.

00:51:45 That’s such an interesting way to put it.

00:51:47 It will not, this kind of scenario

00:51:49 will not survive deep understanding of physics.

00:51:53 It’s an interesting way to put it

00:51:54 because it makes you wonder what kind of scenarios

00:51:59 will be created by our deeper understanding of physics.

00:52:04 Maybe, sorry to go crazy for a second,

00:52:08 but if you have like the pan psychism idea

00:52:11 that consciousness permeates all matter,

00:52:14 maybe traveling in that, whatever laws of physics,

00:52:17 the consciousness operates under something like that.

00:52:20 In that view of the university,

00:52:21 if we somehow are able to understand that part,

00:52:24 maybe traveling is super easy.

00:52:26 Yeah, it does not follow the constraints

00:52:30 of the speed of light, something like this.

00:52:32 Yeah, so look, I have a definite degree of sympathy

00:52:38 with the possibility that consciousness might be more

00:52:42 than what we described earlier

00:52:45 as just the byproduct of mindless particles.

00:52:48 You just made the rock happy.

00:52:50 Exactly, so it isn’t the approach

00:52:54 that feels to me the most likely, but I see the logic.

00:52:59 If you’ve got the puzzle,

00:53:01 how to mindless particles build mind,

00:53:04 one resolution might be the particles are not mindless.

00:53:08 The particles have some kind of proto conscious quality.

00:53:10 So there’s something appealing

00:53:13 about that straightforward solution to the puzzle.

00:53:16 And if that’s the case, if we do live in a pan psychist world

00:53:20 where there is a degree of consciousness residing

00:53:22 in everything in the world around us, then yes,

00:53:25 I do think some interesting possibilities might emerge

00:53:28 where maybe there’s a way of communing

00:53:31 with physical reality in a deeper way than we have so far.

00:53:36 I mean, we as human beings,

00:53:38 a vital part of our existence

00:53:40 is human to human communication, contact.

00:53:43 We live in social groups and that’s what it’s allowed us

00:53:46 to get to the place where we’ve gotten.

00:53:48 Imagine that we have long missed

00:53:51 that there’s other consciousness out there

00:53:54 and some kind of relationship or communion

00:53:57 with that larger conscious possibility

00:53:59 would take us to a different place.

00:54:01 Now, do I buy into this yet?

00:54:03 I don’t, I don’t see any evidence for it,

00:54:06 but do I have an open mind and allow for the possibility

00:54:10 in the future?

00:54:11 Yeah, I do.

00:54:13 So if that’s not the case

00:54:15 and you have these simple particles

00:54:18 that at the macro level emerges some interesting stuff

00:54:21 like consciousness, another thing you write about

00:54:24 in the Until the End of Time book

00:54:27 is the thing that it seems to emerge at the macro level

00:54:30 is the feeling like there’s a free will,

00:54:34 like we decide to do stuff.

00:54:36 And you have a really interesting take here,

00:54:39 which is, no, there’s not a free will.

00:54:43 I’m just gonna speak for you and then you can correct me.

00:54:45 No, there’s not a free will,

00:54:48 but there is an experience of freedom.

00:54:51 Yeah.

00:54:54 Which I really love.

00:54:56 So where does the experience,

00:54:58 where does freedom come from

00:54:59 if we don’t have any kind of physics based free will?

00:55:02 Yeah, and so the idea follows naturally

00:55:06 from all that we’ve been talking about.

00:55:08 Let’s make the assumption that all there is

00:55:11 in the physical universe is stuff governed by laws.

00:55:15 We may not have those laws,

00:55:16 may not know what the fundamental stuff is yet,

00:55:19 but everything we know in science points in the direction

00:55:23 that it’s physical stuff governed by universal laws.

00:55:27 And that being the case, or that being the assumption,

00:55:31 then you come to a particular collection

00:55:33 of those ingredients called a human being.

00:55:35 And that human being has particles

00:55:38 that are fully governed by physical law.

00:55:41 And when you then recognize it,

00:55:43 every thought that we have,

00:55:44 every action that we undertake

00:55:46 is just the motion of particles.

00:55:49 When I’m thinking thoughts right now,

00:55:50 of course, at this level of description,

00:55:53 it is the motion of particles cascading

00:55:56 down various neurons inside of my head and so on.

00:55:59 And every single one of those motions,

00:56:02 collectively and individually,

00:56:05 is fully governed by these laws

00:56:08 that we perhaps don’t have yet,

00:56:09 but we imagine one day we will.

00:56:12 That leaves no opportunity for any kind of freedom

00:56:15 to break free from the constraint of physical law.

00:56:19 And that is the end of the story.

00:56:21 So the traditional intuitive notion of free will,

00:56:24 that we’re the ultimate authors of our actions,

00:56:26 that we were the buck stops,

00:56:28 that there is no antecedent,

00:56:30 that is the cause for our decided to go left or right,

00:56:35 choose vanilla or chocolate, live or die,

00:56:38 that intuitive sensation does not have a basis

00:56:42 in our understanding of the physical world.

00:56:43 So that’s the end of the free will of the traditional sort.

00:56:47 But then your question is,

00:56:49 what about this other kind of freedom I talk about?

00:56:52 And the other kind of freedom,

00:56:53 if you focus on it intently,

00:56:55 I think is actually the true version of freedom

00:57:00 that we feel.

00:57:02 And that freedom is this.

00:57:04 You look at inanimate objects in the world,

00:57:07 rocks, bottles of water, whatever,

00:57:10 they have a very limited behavioral repertoire.

00:57:13 Why?

00:57:14 Their internal organization is too coarse

00:57:17 for them to do very much, right?

00:57:18 You try to have a conversation with a glass of water,

00:57:22 you send sound waves, it doesn’t do much.

00:57:24 It may vibrate a little bit,

00:57:26 but the repertoire of responses are incredibly limited.

00:57:30 The difference between us and a rock or a bottle of water

00:57:33 is that our inner organization,

00:57:35 by virtue of eons of evolution by natural selection,

00:57:38 is so refined, so spectacularly ordered,

00:57:42 that we have a huge repertoire of behaviors

00:57:46 that are finely attuned to stimuli from the external world.

00:57:51 You ask me a question, that’s a stimulus,

00:57:53 and all of a sudden,

00:57:54 these particle processes go into action,

00:57:56 and this is the result, this answer that I’m giving you.

00:58:00 So the freedom that we have is not from

00:58:03 the control of physical law.

00:58:05 The freedom that we have is from the constrained behavior

00:58:08 that has long since governed inanimate objects.

00:58:11 We are liberated from the limited behavioral repertoire

00:58:14 of rocks and bottles of water

00:58:17 to have this broad spectrum of responses.

00:58:20 Do we pick them?

00:58:20 We do not.

00:58:21 Do we freely choose them?

00:58:23 We do not, but yet we have them,

00:58:26 and we can marvel at those behaviors,

00:58:29 and that’s the freedom that we have.

00:58:31 The complexity and the breadth of that repertoire

00:58:34 is where the freedom emerges.

00:58:36 Is there something to be said about emergence?

00:58:40 I don’t know if you know,

00:58:42 I’ve looked at much about objects

00:58:43 that I seem to love way more than anyone else,

00:58:47 which is Sally or Tom,

00:58:49 like game of life type of stuff.

00:58:51 From simple things emerges beautiful complexities,

00:58:56 and so that’s that repertoire.

00:58:58 It’s like, it seems if you have enough stuff,

00:59:04 just beautiful complexity emerges

00:59:06 that sure as heck to our human eyes looks

00:59:09 like there’s consciousness there, there’s free will,

00:59:12 there’s little objects moving about and making decisions.

00:59:15 I mean, all of that,

00:59:16 you can say it’s anthropomorphization,

00:59:18 but it sure as heck feels

00:59:21 like they’re organisms making decisions.

00:59:25 What is that emergence thing?

00:59:27 Is that within the realm of physics to understand?

00:59:31 Is it within the realm of poetry?

00:59:36 What is that, like complex systems, emergence?

00:59:39 Will that ever be understood by science?

00:59:41 So here’s the way that I think about it.

00:59:43 So there are clearly qualities of the world

00:59:47 that emerge on macroscopic scales,

00:59:50 our sense of beauty, wonder, consciousness,

00:59:53 all of these kinds of qualities.

00:59:55 Do I feel that they ultimately are explainable

01:00:00 from the laws of physics?

01:00:01 I do.

01:00:02 There is nothing that’s not ultimately explainable

01:00:06 with the laws of physics from this physicalist perspective,

01:00:09 which is what I take.

01:00:10 So you got the particles, you got the laws,

01:00:13 and you have things that emerge

01:00:16 from the choreographed motions of those particles.

01:00:20 But is that the best language

01:00:23 for talking about these emergent qualities?

01:00:26 Usually not.

01:00:27 If I was to take something even more mundane,

01:00:30 like a baseball flying through the air,

01:00:33 if I was to describe it in terms of the quarks

01:00:35 and the electrons,

01:00:36 I’d give you this mountain of data

01:00:39 with 10 to the 28 particles

01:00:42 and all of their coordinates and spaces

01:00:45 a function of time.

01:00:46 I hand you this mountain of data,

01:00:46 you’d be like, I don’t know what this is.

01:00:49 And then if you really were clever and you’re looking,

01:00:51 oh, it’s a baseball,

01:00:53 just described in the least economical way possible.

01:00:57 It is much more useful and insightful

01:01:00 to talk about the baseball flying through the air.

01:01:01 Similarly, there are things at the macroscopic level

01:01:05 like human experience and human emotion and human action

01:01:09 and the sensation of free will

01:01:12 that we undeniably all have,

01:01:14 even if it itself doesn’t have a basis

01:01:17 in our understanding of the physical world.

01:01:19 It’s useful to talk about things in this very human language.

01:01:24 And so, yes, it’s vital to talk about things

01:01:26 in the poetic language of human experience,

01:01:29 but do not lose sight of the fact, and some people do.

01:01:31 They say, oh, it’s just an emergent phenomenon.

01:01:33 Don’t lose sight of the fact that emergent phenomena

01:01:36 are emerging from this deeper understanding

01:01:39 that comes from the reductionist account of physical law.

01:01:42 And there’s a lot of insight to come from that,

01:01:44 such as the freedom that you thought that you had,

01:01:48 the freedom of will that you thought you had.

01:01:50 It doesn’t have a basis in that reductionist account,

01:01:53 so it’s not real.

01:01:56 So speaking of the poetry of human experience,

01:01:59 you mentioned the images of the black holes.

01:02:01 How did it make you feel a few years ago

01:02:03 when that first image came out?

01:02:04 It’s truly amazing.

01:02:06 A sense of, well, I guess the feeling was both amazing

01:02:11 and there was a little sense of,

01:02:14 jealousy is not quite the right word,

01:02:17 but a sense of longing.

01:02:19 Yeah, I think that’s a better word,

01:02:20 because here’s a subject that started with Einstein

01:02:25 back in 1915, writes down the equations

01:02:28 of the general theory of relativity,

01:02:30 and then there are scores of individuals over the decades,

01:02:34 starting with people like Karl Schwarzschild

01:02:37 who analyze the equations,

01:02:38 see the possibility of black holes.

01:02:40 People develop these ideas.

01:02:41 John Wheeler, all these greats of physics.

01:02:44 It’s still a hypothetical subject.

01:02:46 It gets closer to reality through observations

01:02:48 of the center of our galaxy,

01:02:50 stars whipping around in a manner

01:02:52 that could only really be explained

01:02:54 by there being a black hole in the center of our galaxy,

01:02:56 but it was still indirect.

01:02:58 To actually have a direct image that you can look at,

01:03:03 what a beautiful arc, narrative arc

01:03:06 from the theoretical to the absolutely established.

01:03:10 And that’s what we hope will happen with other areas,

01:03:13 for instance, string theory, right?

01:03:15 I mean, wholly mathematical subject at the outset

01:03:18 and still pretty much a wholly mathematical subject today.

01:03:22 Yeah, do we long for that image

01:03:25 where we can look at it and say, string, it’s real.

01:03:29 I mean, how thrilling, how thrilling to be part

01:03:33 of that journey, to be part of that step

01:03:36 that moves things from the abstract to the concrete.

01:03:39 Yeah, so like the image of the DNA, the early images

01:03:44 of the DNA, for example, but there is something special.

01:03:47 So the problem with strings is they’re tiny.

01:03:50 So it’s harder to take a picture in the following sense.

01:03:54 When you think of a black hole, I mean, you have a swirl

01:03:58 of, I guess, what is, I don’t even know it’s dust,

01:04:00 whatever light.

01:04:02 A careening onto the event horizon.

01:04:04 And then there’s darkness in the center.

01:04:06 And you just imagine, so that picture in particular,

01:04:10 I guess, is of a gigantic black hole.

01:04:13 So you just, I mean, it’s terrifying.

01:04:16 Billions of times the mass of the sun.

01:04:17 Yeah, so it’s both exciting and terrifying.

01:04:19 I mean, I don’t know where you fall in the spectrum.

01:04:22 I think it’s exciting at first.

01:04:24 Like the longer I think about it, every time I think

01:04:27 about it, the more terrifying it becomes.

01:04:29 So it always starts exciting and then it goes to terrifying.

01:04:32 And both are feelings, very human feelings

01:04:36 that I appreciate.

01:04:38 It’s like terrified awe.

01:04:40 Somehow it’s still beautiful.

01:04:43 It’s a good way of saying it.

01:04:43 And I think I kind of share that reaction

01:04:45 because there is a way in which when you work on this

01:04:49 subject, like all the time, I teach it, I teach about

01:04:52 black holes, write the equations on the blackboard.

01:04:56 The ideas reside in a very cognitive,

01:05:01 I don’t know, mathematical portion of the brain,

01:05:06 or at least for me.

01:05:08 And it’s only when you like sit down and it’s quiet

01:05:11 and you start to contemplate, wait, wait, wait, wait,

01:05:13 this isn’t just like a mathematical game.

01:05:17 There are these monsters out there.

01:05:19 Now I don’t, not in a sense of I fear for my life,

01:05:22 but it’s a sense of how extraordinary is this universe.

01:05:28 And so it is breathtaking.

01:05:30 How powerful nature is.

01:05:31 Yeah, how stupendously powerful nature is.

01:05:37 And so there is a deep sense of humility

01:05:42 that I think this instills if you really allow

01:05:45 the ideas to sink in.

01:05:48 Well, I have to ask about the most stupendously

01:05:51 powerful thing to have ever happened in our universe,

01:05:54 which is the Big Bang.

01:05:56 What’s up with the Big Bang?

01:05:57 So we can, I mean, with gravitational waves,

01:06:01 the hope is you have more and more accurate measurements

01:06:05 of the gravitational waves.

01:06:06 You can crawl back further and further back in time

01:06:08 towards the Big Bang.

01:06:10 Do you have a hope that we’ll be able to understand

01:06:13 the early spark that created our universe?

01:06:18 Yeah, that and the deep interior of a black hole

01:06:23 I think are the biggest mysteries that we hope

01:06:26 the melding of quantum mechanics and gravity will reveal,

01:06:30 will illuminate.

01:06:32 And what question could be more captivating

01:06:36 than why is there something rather than nothing, right?

01:06:39 Why is there a universe at all?

01:06:43 And will the theories that we’re developing

01:06:46 take us to an answer to that?

01:06:48 I don’t know.

01:06:49 Even if we truly knew what the Big Bang is,

01:06:51 and that’s a big question in its own right,

01:06:53 one would still be left with the question,

01:06:55 well, okay, so you’ve explained the process

01:06:59 by which a tiny nugget of a universe,

01:07:03 a tiny nugget of space time can undergo some kind of growth

01:07:08 to yield the world around us.

01:07:10 But presumably in that explanation,

01:07:12 you’re gonna involve mathematics and some ingredients

01:07:16 like quantum fields or matter or energy or something.

01:07:21 Where did that stuff come from?

01:07:24 Can we get to that level of explanation?

01:07:26 I don’t know, but it is remarkable

01:07:29 that if you ask what happened a millionth of a second

01:07:34 after the Big Bang,

01:07:36 it’s not really that controversial any longer, right?

01:07:40 Even though there’s a lot of argument in the field

01:07:42 and it’s very heated right now I should say

01:07:45 regarding what is the right theory of the Big Bang?

01:07:49 What is the right theory of early universe cosmology

01:07:53 where I mean early, much earlier

01:07:55 than a millionth of a second,

01:07:56 a lot of dissent, a lot of heated arguments about that.

01:08:01 No pun intended.

01:08:02 Yeah, right, exactly.

01:08:04 But you go like a millionth of a second after that

01:08:08 and we’re on pretty firm ground.

01:08:10 Isn’t that amazing, right?

01:08:12 To understand what happened from that point forward.

01:08:15 But to go back is controversial.

01:08:18 So there is this theory called inflationary cosmology,

01:08:21 which I would say has been the dominant paradigm

01:08:24 since early 1980s.

01:08:27 So what does that mean?

01:08:27 Roughly 40 years now,

01:08:28 it’s been the dominant cosmological paradigm.

01:08:31 And it makes use of a curious feature

01:08:33 of Einstein’s general theory of relativity,

01:08:36 his theory of gravity,

01:08:37 where Einstein shows us mathematically

01:08:39 that gravity can not only be attractive,

01:08:41 the kind of gravity that we’re used to,

01:08:43 things pulled together, but it can also be repulsive.

01:08:47 And that fact is then leveraged by people like Alan Guth

01:08:53 and Andre Linde, and at the time Paul Steinhardt

01:08:56 and Andreas Albrecht and others to say,

01:08:58 okay, if we had a little nugget in the earlier universe,

01:09:01 which was filled with the stuff

01:09:03 that yields this repulsive gravity,

01:09:05 well, that would have blown everything apart.

01:09:07 It would cause everything to swell.

01:09:09 Beautiful explanation for what the bang

01:09:11 in the big bang was.

01:09:13 And then people mathematically analyze the consequences

01:09:16 of this idea and they make predictions

01:09:19 for tiny temperature differences across the night sky

01:09:22 that in principle could be measured.

01:09:24 You send up balloons, you send up satellites

01:09:27 with very refined thermometers,

01:09:29 and they measured the temperature of the night sky

01:09:33 and the statistical distribution

01:09:34 of the temperature differences agrees

01:09:36 with the mathematical predictions.

01:09:39 I mean, you just sort of have to stand in awe

01:09:43 of this insight.

01:09:44 So you think, aha, the theory has been established,

01:09:48 but scientists are an incredibly skeptical bunch.

01:09:54 And some scientists, including one of the people

01:09:56 who helped develop the theory at the outset,

01:09:58 Paul Steinhardt comes along and says,

01:10:00 well, yeah, this theory has done pretty well so far,

01:10:04 but there are aspects of this theory

01:10:06 that are making me lose confidence.

01:10:08 For instance, this theory seems to suggest

01:10:10 that there might be other universes.

01:10:13 Like, how do you make sense of a theory

01:10:15 that suggests there are other universes?

01:10:16 Or there are others who come along and say,

01:10:18 this theory seems to talk about length scales

01:10:23 that are minuscule even by the so called Planck length,

01:10:26 the sort of shortest length that we can imagine

01:10:29 making sense of in a theory of quantum gravity.

01:10:31 How do you make sense of that?

01:10:33 And so on and so forth, they develop a list of things

01:10:36 that they consider to be chinks

01:10:38 in the inflationary cosmological theory’s armor.

01:10:42 And they develop other ideas,

01:10:44 which they claim yield the same predictions

01:10:47 as inflationary cosmology

01:10:48 for those temperature differences across space,

01:10:50 but don’t suffer from these problems.

01:10:52 And then the inflationary cosmology folks say,

01:10:55 no, no, no, hang on.

01:10:56 Your theory suffers from different problems.

01:10:59 And so the arguments goes, it’s a healthy debate.

01:11:02 Talk about real debates in science.

01:11:05 So when you ask what’s up with the Big Bang,

01:11:07 I don’t know right now.

01:11:09 If you would have asked me five years ago,

01:11:12 maybe even less than that, three or four years ago,

01:11:15 I’ve said, look, inflationary cosmology has some issues,

01:11:19 but the package of explanations it provides is so potent

01:11:23 and the issues that beset it are seemingly solvable to me

01:11:29 that I would imagine it’s going to in the end, win out.

01:11:32 I would still say that today,

01:11:34 but I wouldn’t say it as loudly.

01:11:36 I wouldn’t say it as confidently.

01:11:38 I think it’s worth thinking about alternate ideas

01:11:42 and it could be the case that the paradigm

01:11:44 at some point shifts.

01:11:46 Does dark matter and dark energy fit into the shifting

01:11:50 of the explanations for those?

01:11:52 Yeah, certainly.

01:11:53 So dark energy has in the inflationary theory

01:11:58 is kind of a big mystery.

01:12:00 So dark energy is the observational realization

01:12:05 in the last 20 years

01:12:06 that not only is the universe expanding,

01:12:09 it’s expanding ever more quickly.

01:12:11 Something is still pushing things outward.

01:12:15 And the explanation is that there’s like a residual version

01:12:18 of the repulsive gravity from the early universe,

01:12:20 but it’s such a strange number.

01:12:23 When you write that amount of dark energy

01:12:25 using the relevant units in a theory of quantum gravity,

01:12:29 it’s a decimal point followed by like 120 zeros

01:12:33 and then a one.

01:12:34 We’re not used to those kinds of numbers in physics.

01:12:38 We’re used to a half, one, pi, e squared to two.

01:12:44 Those are the kinds of fundamental numbers

01:12:46 that emerge in our explanations of the world.

01:12:49 And we look at this bizarre number,

01:12:51 decimal point, all these zeros and a one,

01:12:53 we say something’s wrong there.

01:12:56 Like where would that number have come from?

01:12:59 And now there are people who suggest resolution to it.

01:13:01 So it’s not like we’re totally in the dark on it,

01:13:03 but those people like Paul Steinhard

01:13:06 who have alternate cosmological theories,

01:13:09 cyclic cosmologies as they call it,

01:13:11 claim that they have a more natural explanation

01:13:14 of the dark energy,

01:13:15 that it naturally feeds into a cyclical process

01:13:19 that is their cosmological paradigm.

01:13:22 So yeah, if the cosmology should change,

01:13:26 it’s conceivable our view of dark energy

01:13:29 may change from deeply mysterious

01:13:31 to deeply integrated into a different paradigm.

01:13:34 That is possible.

01:13:35 I think it’s Roger Penrose that think

01:13:37 that information can bleed through

01:13:39 from before the Big Bang to the after the Big Bang.

01:13:42 Is the Big Bang like a full erasure of the hard drive

01:13:46 or is there some information that could bleed through?

01:13:48 Yeah, I mean, so Roger is among the most creative thinkers

01:13:54 of the last 100 years,

01:13:55 rightly won the Nobel Prize for his insights

01:13:59 into singularities in space time

01:14:02 that we know to afflict our mathematical solutions

01:14:06 of black holes in the Big Bang and so forth.

01:14:08 And he has an enormously fertile imagination.

01:14:13 And I mean that in the most positive sense.

01:14:16 And so he has put forward this idea,

01:14:19 this conformal cyclic cosmology,

01:14:21 I think is the official title,

01:14:23 although I could be getting that wrong.

01:14:26 I can’t say that I’ve studied it.

01:14:27 I have seen lectures on it.

01:14:30 I don’t find it convincing as yet.

01:14:33 It feels like it’s being built to find a solution

01:14:38 as opposed to sort of more naturally emerging.

01:14:42 Maybe Roger would say otherwise.

01:14:43 And I don’t mean to in any way

01:14:47 cast aspersions on the work.

01:14:48 It’s vital and interesting and people are thinking about it.

01:14:51 I don’t consider it as close a competitor

01:14:55 to say the inflationary theory as for instance,

01:14:58 the stuff that Paul Steinhardt has put forward.

01:15:00 But again, you’ve got to keep an open mind

01:15:04 in this business when there’s so much

01:15:06 that we don’t yet understand.

01:15:07 I mean, it is wild to think

01:15:08 that information could survive something like that.

01:15:10 Just like it is wild to imagine

01:15:13 that information could escape a black hole, for example.

01:15:16 It just seems like by construction,

01:15:20 these things are supposed to not bleed out anything.

01:15:24 But one of the challenges in all of these theories

01:15:25 is when we talk about a singularity,

01:15:27 has this real sexy term, the singularity.

01:15:30 But a singularity is in more ordinary language,

01:15:35 a physical system where the mathematics breaks down.

01:15:39 It’s nonsensical.

01:15:41 It’s like taking one divided by zero.

01:15:42 You put that into a calculator and it says E error, right?

01:15:45 It does not make sense, doesn’t compute.

01:15:48 And so it’s very hard to make definitive statements

01:15:53 about things like the Big Bang or about black holes

01:15:56 until we cure the mathematical singularities.

01:15:59 And there are some who claim that in certain regimes,

01:16:03 the singularities have been cured.

01:16:05 I don’t by any means think that there’s consensus

01:16:08 on these ideas.

01:16:09 So when one talks about information sort of bleeding

01:16:12 through the Big Bang, you’ve really got to make sure

01:16:15 that the equations have no singularity.

01:16:16 You talk about cyclic cosmology,

01:16:18 you’ve got to make sure that the equations

01:16:20 don’t have any singularities as you go from, say,

01:16:22 one cycle to the next.

01:16:23 Now, some of the proponents of these theories claim

01:16:25 that they have resolved these issues.

01:16:27 I don’t think that there’s a general sense

01:16:30 that that is the case as yet, but it could be that,

01:16:32 look, life is so short that I haven’t had the time

01:16:36 to deeply delve into all the mathematical intricacies

01:16:39 of all the ideas that have been put forward.

01:16:40 If I did that, I’d never do anything else.

01:16:42 But that’s what the issue is.

01:16:44 And of course, it’s just math.

01:16:45 There may be holes.

01:16:47 There may be gaps in our understanding

01:16:52 in the way we’re modeling physical reality.

01:16:55 Well, that’s the point.

01:16:56 In fact, when you said, I was about to jump in

01:16:57 and say modeling, but you got there first,

01:16:59 and it’s exactly the right point.

01:17:02 We’re talking about the universe here, right?

01:17:04 And how do you talk about the universe

01:17:06 with a straight face, mathematically?

01:17:09 And the way you do it is you simplify,

01:17:12 you throw away those characteristics of the universe

01:17:14 that you don’t think are vital to a full understanding.

01:17:18 And so we’re gonna get to a point people are starting to

01:17:21 where we’ve got to go beyond those simplifications.

01:17:24 And so cosmology has for a long time modeled the universe

01:17:29 in the most simplest terms, homogeneous, isotropic.

01:17:33 It has just a few parameters that describe it,

01:17:35 the average density of mass and energy and so forth.

01:17:38 We have to go beyond those simplifications,

01:17:40 and that will require putting these things on computers.

01:17:43 We’re not gonna be able to do calculations there.

01:17:45 So much as astrophysics has gone beyond many simplifications

01:17:49 to now give really detailed simulations of star systems

01:17:53 and galaxies and so forth,

01:17:54 we’re gonna have to do that with cosmology,

01:17:56 and people are starting to do that today.

01:17:59 Yeah, I’ve seen some interesting work on simulation,

01:18:02 most simulation cosmology, by the way, is just awesome.

01:18:05 But just like simulation of the early formation

01:18:08 of our solar system to understand how the like the Oort cloud

01:18:12 and just, I don’t know, the whole of it,

01:18:16 how Earth came to be, like how Jupiter just protects us.

01:18:22 And then there’s like weird like moons and volcanoes

01:18:28 and like modeling all of that,

01:18:30 the formation of all of that is fascinating.

01:18:34 Because that naturally is the question

01:18:37 of how does life emerge on these kinds of rocks?

01:18:41 How does a rock become a rabbit?

01:18:44 But speaking of models,

01:18:47 there’s an equation called the Drake equation.

01:18:50 We were talking about life.

01:18:52 Have to ask, at the highest level first,

01:18:56 when you look out there,

01:18:58 how many alien civilizations do you think are out there?

01:19:01 Well, zero, one, or many?

01:19:04 So if you say civilization,

01:19:08 I would bring my number way down.

01:19:12 It could be zero.

01:19:15 If you talk about life, I think it could be many.

01:19:20 As we were saying before,

01:19:21 I think the move from life to consciousness,

01:19:25 the kinds of beings that would build

01:19:27 what we would recognize as a civilization,

01:19:30 that may be extraordinarily rare.

01:19:34 I hope it’s not.

01:19:36 You know, as a kid, I loved Star Trek.

01:19:38 I just loved the idea that we would be part

01:19:40 of some universal community where,

01:19:43 look, experience on planet Earth

01:19:46 suggests it doesn’t always go so well

01:19:48 when groups who are separated try to come together

01:19:50 and live in some larger collective.

01:19:53 But again, as an optimist,

01:19:55 how amazing would it be to converse

01:19:57 with an alien civilization and learn

01:19:59 what they’ve figured out about physics and cosmology

01:20:03 and compare notes and learn from each other

01:20:06 in some wonderful way?

01:20:09 I love that idea.

01:20:10 But if you ask me the likelihood of it,

01:20:13 I would err on saying it may be so improbable

01:20:18 that the conditions conspire to allow life

01:20:21 to move to this place of consciousness

01:20:24 that it might be rare.

01:20:27 It might be oversimplifying things,

01:20:28 but just observing the power of the evolutionary process,

01:20:32 I tend to believe,

01:20:34 and like you read different theories of how we went,

01:20:40 how Homo sapiens evolved,

01:20:43 it seems like the evolutionary process

01:20:45 naturally leads to Homo sapiens

01:20:50 or creatures like that or much better than that.

01:20:53 So to me, there’s several scary scenarios.

01:20:57 So, okay, the positive scenario

01:21:00 is life itself is really difficult.

01:21:03 So that origin of life is difficult.

01:21:05 That’s exciting for many reasons

01:21:08 because we might be able to prove that wrong easily

01:21:12 in the near term by finding life elsewhere.

01:21:14 Sure.

01:21:15 The scary thing to me is if life is easy

01:21:21 and there’s plenty of conscious intelligent civilizations

01:21:26 out there and we have not obviously made contact,

01:21:30 which means with intelligence and consciousness

01:21:33 comes responsibility and ultimately destruction.

01:21:39 So with power comes great responsibility

01:21:42 and then we end up destroying ourselves.

01:21:44 That’s the scariest.

01:21:48 The positive, I guess, version is that

01:21:51 maybe we’re being watched,

01:21:54 sort of like there’s a transition

01:21:57 to where you don’t wanna ruin the primitive villages

01:22:00 out there and so there’s a protective layer around us.

01:22:04 They’re watching.

01:22:06 So where do you in these possible explanations

01:22:09 to the Fermi paradox,

01:22:10 why haven’t we contacted aliens?

01:22:12 Do you land on?

01:22:13 Well, I think the most straightforward explanation

01:22:17 is that there aren’t any.

01:22:20 Now, there are many other explanations too.

01:22:23 So you can’t be dogmatic about things

01:22:25 that are just sort of gut feel,

01:22:27 but one of my favorite Twilight Zone episodes,

01:22:31 I don’t know if you ever saw this one

01:22:33 where this alien civilization finally comes

01:22:36 to planet Earth and gives us this book

01:22:39 that they really want us to have and to hold

01:22:42 and it’s in this foreign language,

01:22:44 you don’t understand it.

01:22:45 The cryptographers, they desperately try to decipher it

01:22:49 as humans are gonna visit this other alien planet

01:22:52 and they’re all sending back postcards,

01:22:53 how wonderful it is and so forth

01:22:55 and they finally decipher the title.

01:22:58 It’s To Serve Man and everyone’s so thrilled,

01:23:01 oh, they’re here to serve us, it all makes sense

01:23:03 and then just as one of the final cryptographers

01:23:06 is going on to the alien ship,

01:23:08 his helper runs and says,

01:23:10 I’ve deciphered the rest of the book.

01:23:12 To Serve Man, it’s a cookbook.

01:23:14 So yeah, is that a possibility?

01:23:20 Sure.

01:23:21 And so could they be watching us

01:23:23 and just sort of waiting for us to get

01:23:26 to a mature enough level?

01:23:29 I don’t know, it strikes me.

01:23:31 Well, I think it’d be better to have this conversation

01:23:33 after the James Webb Telescope.

01:23:35 I mean, I do think that if we look

01:23:38 at the atmospheres of many planets,

01:23:41 I mean, there’s now an estimate now

01:23:42 that there’s on order of one planet per star on average.

01:23:48 So we’ve long known that the galaxy,

01:23:50 hundreds of billions of stars,

01:23:52 numbers of galaxies, hundreds of billions of galaxies.

01:23:54 So we’re talking about hundreds of billions

01:23:56 of hundreds of billions of planets, oh my.

01:23:59 And if we start to survey some of these planets

01:24:02 and one after the other after the other,

01:24:03 we just sort of find no evidence

01:24:06 for any of the biological markers.

01:24:10 It could be, of course,

01:24:11 maybe life takes a radically different form.

01:24:13 It’d be hard to know that.

01:24:15 But I think that would at least give us some insight

01:24:18 on the life question.

01:24:19 But I just don’t see how we get insight

01:24:21 on the civilization or consciousness question

01:24:25 without the direct connection.

01:24:27 And it strikes me that if consciousness is ubiquitous,

01:24:32 let’s say life is, I’m willing to grant that.

01:24:35 If consciousness is also ubiquitous,

01:24:37 then I don’t understand why they haven’t been here

01:24:41 or why there hasn’t been separation

01:24:43 because presumably they should be much further ahead of us.

01:24:47 How unlike would it be that we’re like,

01:24:50 of all consciousness in the universe,

01:24:52 we’re the most advanced.

01:24:53 That’d be such a special place for human beings

01:24:56 that it’s hard for me to grant that as a likely possibility.

01:25:00 Rather, I think we’re kind of run of the mill.

01:25:02 And there are many who are far more advanced than us.

01:25:06 And I don’t think that they would expend the energy

01:25:09 to hide themselves.

01:25:11 I don’t think they care enough.

01:25:12 And so see, that’s actually what I believe

01:25:15 that there’s a very large number of civilizations

01:25:19 that are far more advanced than us.

01:25:21 But my sense is that humans are exceptionally limited

01:25:25 both in our direct sensory capabilities and our physics,

01:25:29 our tools of sensing that just like with the string theory

01:25:33 and the multiple dimensions, we’re just not like,

01:25:36 it’s like, I honestly believe there could be stuff

01:25:39 in front of our nose that we’re just not seeing

01:25:43 because we’re too dumb, too much hubris

01:25:48 and I mean, there’s a bunch of stuff

01:25:50 and too ignorant to the fabric of reality,

01:25:54 all of those things.

01:25:56 We’re young in terms of intelligence.

01:25:59 But I guess what I’d say is like, I’m on board

01:26:01 with all of that as a real possibility,

01:26:04 but then it does strike me that we are sufficiently

01:26:09 able to observe the unit.

01:26:11 Look, we can look back to a fraction of the duration

01:26:16 from here to the, just a fraction is left

01:26:20 that we are unable to see.

01:26:22 So however young we are, we have been able

01:26:27 to sort of pierce the universe and it just strikes me

01:26:29 that there would be some signature,

01:26:33 but maybe that’s coming.

01:26:35 But look, having said that I do, look,

01:26:38 I certainly note the fact that it’s rare

01:26:41 that I stoop down while walking in Manhattan

01:26:46 and sort of dig up some ants in the bushes

01:26:48 on the side of the street and talk to the ants, right?

01:26:51 Because it’s just not interesting to me.

01:26:52 So if we’re like the ants on the cosmological landscape,

01:26:56 then yeah, I can imagine that the super advanced aliens

01:26:58 would be like, like whoever, you know,

01:27:01 but I feel like we’re sufficiently advanced

01:27:04 that there should be some signal signature of that,

01:27:07 but maybe it’s coming.

01:27:08 I think the deeper fundamental problem between us

01:27:10 and the ants is that we don’t have a common language.

01:27:12 It’s not the interest.

01:27:14 It’s that we don’t even have a common language.

01:27:17 And so the alien civilizations don’t even know how to,

01:27:21 like we humans have convinced ourselves we’re special

01:27:24 because we developed the language.

01:27:25 And you talked about the importance of language

01:27:28 to the intelligence, but it makes you wonder

01:27:31 like how very niche is that like club that we’ve,

01:27:36 like tribe we’ve created of language

01:27:38 and linguistic type of systems that are very specific

01:27:41 to our particular kinds of brains

01:27:42 and we share ideas together are all super excited

01:27:45 that we can understand the universe

01:27:46 because we came up with some notation and math.

01:27:49 I wonder if there’s some totally other kinds of language

01:27:52 that communicates on a different timescale

01:27:54 with different, very different mechanisms

01:27:56 in the space of information that just is not,

01:28:00 it’s everything, everything is lost in translation.

01:28:03 Yeah, and it could well be as a look.

01:28:05 I mean, I think part of the reason I go

01:28:07 toward the possibility of the soul intelligence

01:28:12 is there’s a certain kind of romantic appeal

01:28:16 to looking out in the cosmos and it’s just quiet

01:28:20 and it’s just eternal silence.

01:28:22 There’s something that appeals to me

01:28:25 at an emotional level that way.

01:28:27 But yeah, I mean, nobody knows.

01:28:31 And it’s certainly conceivable

01:28:35 that there’s just a radical mismatch

01:28:38 between the kinds of things

01:28:40 that we are able to observe and sensitive to

01:28:42 versus the kinds of structures that permeate the universe

01:28:47 in a manner that simply we’re unable to detect.

01:28:50 Well, if we are alone, that is exciting.

01:28:54 And one of the ways it’s exciting

01:28:56 is that it’s up to us to become,

01:29:00 to expand out into the universe,

01:29:02 to permeate consciousness out into the universe.

01:29:07 So that’s where space exploration comes in.

01:29:09 Let me ask you as somebody who’s a screen theorist,

01:29:12 a physicist, do you think space exploration,

01:29:17 a colonizing space is a physics or an engineering problem?

01:29:21 What would you say?

01:29:22 Yeah, I think it’s fundamentally an engineering problem

01:29:25 if we’re not trying to do things like build wormholes

01:29:30 the way they did, say an interstellar

01:29:32 to get to a different place

01:29:34 or trying to travel near the speed of light

01:29:36 so that we would actually be able

01:29:38 to traverse interstellar distances.

01:29:40 I mean, without that,

01:29:41 our colonization will happen in a very, very slow rate.

01:29:47 But one of the beauties of relativity

01:29:50 is if you do travel near the speed of light,

01:29:51 you can actually go arbitrarily far in a human lifetime.

01:29:56 People say, how’s that possible?

01:29:57 You can’t go billions of light years.

01:29:59 Billions of light years, well, you can actually,

01:30:01 because as you can do the speed of light,

01:30:03 the way in which space and time change

01:30:06 allows you to go in principle arbitrarily far.

01:30:08 That’s very exciting.

01:30:09 But if we put that physics side of the issue

01:30:13 and the manipulation of space and time to the side,

01:30:15 yeah, I think it’s a deep engineering problem.

01:30:18 How do you terraform other planets?

01:30:21 I mean, how do you go beyond our local neighborhood,

01:30:26 say without using the ideas of relativity?

01:30:30 So I think it’s all quite exciting.

01:30:32 And I think the idea is using solar sails

01:30:34 that people have developed

01:30:36 and trying to take that first step to Mars,

01:30:40 I think that’s a vital and valuable step to take.

01:30:43 But yeah, I think these are

01:30:44 fundamentally engineering challenges.

01:30:46 Or extending the human lifespan through biology research

01:30:49 or maybe reducing what it means to be a human being

01:30:54 into information and uploading certain parts of it.

01:30:57 Maybe not all of the full resolution of a human life,

01:31:00 but maybe the essential things like the DNA

01:31:03 and be able to reconstruct that human being.

01:31:07 But I have to ask about Mars.

01:31:12 Do you find the dream of humans stepping on Mars,

01:31:17 stepping foot first, but also colonizing Mars,

01:31:20 one that’s worth us fighting for?

01:31:25 Yeah, usually so.

01:31:25 I mean, I think what we have long been

01:31:28 not always in the best way is a species of explorers

01:31:33 in the literal sense of traveling

01:31:37 from one part of the world to another,

01:31:39 or in the more metaphorical sense

01:31:41 of trying to travel through our minds to the quantum realm

01:31:45 or back to the Big Bang or to the center of black holes.

01:31:47 So I think that’s fundamentally part of the human spirit.

01:31:51 So I do think that’s a vital part of our heritage

01:31:56 brought forward into its next incarnation.

01:32:01 That’s who we are.

01:32:03 Do you think there’ll be a day in the future

01:32:06 where a human being is born on Mars

01:32:11 and has to learn about his or her human origins on Earth?

01:32:16 Like, they’ll have to read in a book.

01:32:18 Yeah, I don’t think it’ll be a book at that stage.

01:32:20 It’ll probably just be uploaded into the head or something

01:32:22 or imprinted into the DNA,

01:32:25 and then they just sort of sense it.

01:32:26 But yeah, I think there’s, well, look,

01:32:29 the issue you raised before is the vital one.

01:32:32 Is it the case that any sufficiently advanced civilization

01:32:36 destroys itself?

01:32:37 Is that sort of a commonplace quality?

01:32:39 I mean, that’s the other potential answer

01:32:41 to the Fermi paradox.

01:32:43 Why aren’t they here?

01:32:44 Because by the time they got to the technological development

01:32:47 where they could travel here, they blew themselves up.

01:32:49 They destroyed themselves.

01:32:50 And that’s an unfortunate,

01:32:53 but not a hard to imagine possibility

01:32:57 based on things that have happened here on planet Earth.

01:33:01 But putting that to the side,

01:33:02 I think that’s the big obstacle,

01:33:05 but putting that to the side,

01:33:06 we will resolve the engineering challenges.

01:33:09 And I should probably modify my answer

01:33:12 from before when you said, is it engineering or physics?

01:33:15 It’s really both, right?

01:33:17 So we will surmount the engineering challenges

01:33:20 and that will then make the physics challenges relevant.

01:33:23 It’ll make it relevant to figure out

01:33:24 how to travel near the speed of light.

01:33:26 It’ll make it relevant to learn

01:33:27 how to manipulate the shape of space time and so forth.

01:33:32 So I think it’s a multi stage process

01:33:35 where it is engineering and ultimately physics.

01:33:38 And if we stick around long enough,

01:33:40 those are the kinds of challenges

01:33:41 I think that we’re ultimately gonna surmount.

01:33:43 And then the physics side is figuring out

01:33:45 how to harness energy enough

01:33:46 to travel outside the solar system,

01:33:48 which seems like a heck of a difficult journey.

01:33:51 But even Mars itself,

01:33:54 I don’t know, maybe because I was born in the Soviet Union

01:33:57 and was born with the,

01:34:02 looking up at the stars and that dream

01:34:04 of like the highest of human achievement

01:34:06 is the ability to fly out there,

01:34:08 to join the stars.

01:34:10 I really liked the idea of going to Mars

01:34:13 and not just stepping foot on Mars.

01:34:15 And it wasn’t until maybe misinformed,

01:34:21 but for me personally,

01:34:23 it wasn’t until Elon Musk started talking

01:34:26 about the colonization of Mars,

01:34:28 did I realize like we humans can actually do that.

01:34:34 And first of all, the importance of somebody saying

01:34:38 that we can do these seemingly impossible things

01:34:42 is immeasurable because the fact that he placed that

01:34:48 into my mind and into the minds of millions of others,

01:34:52 maybe hundreds of millions, maybe billions of others,

01:34:54 young kids today, I mean, that’s gonna make it a reality.

01:34:58 I, for some reason, am deeply excited,

01:35:01 even though my work isn’t AI that echoes all of this.

01:35:06 I’m excited by the idea that somebody would be born,

01:35:09 as we were saying, on Mars and sort of look up

01:35:14 and be able to see with a telescope Earth

01:35:16 and say, that’s where I came from.

01:35:19 I don’t know, that idea scale to other planets,

01:35:23 to other solar systems, that’s really exciting.

01:35:26 And hugely exciting.

01:35:28 I think you’re absolutely right.

01:35:29 I mean, the vital thing is to dream, right?

01:35:33 I mean, and it sounds hackneyed,

01:35:36 but it is so important for young kids,

01:35:40 for the next generation,

01:35:42 to think about the things that are seemingly impossible.

01:35:45 I mean, that’s what makes them possible.

01:35:47 And this is one which is concrete enough.

01:35:50 I mean, this is something that’s gonna happen soon

01:35:52 in terms of actually going to Mars.

01:35:54 And then the next step of establishing some presence,

01:36:00 some semi permanent or permanent presence.

01:36:02 This is not something that’s gonna wait

01:36:05 to the 25th century.

01:36:06 I mean, this is something that’s gonna happen

01:36:07 relatively soon.

01:36:09 So, I mean, it could well be in your lifetime,

01:36:11 unlikely mine, but possibly in your lifetime

01:36:13 that that kid will be born

01:36:15 and have the experience that you described.

01:36:18 So yeah, it’s spectacularly exciting.

01:36:21 And I actually, I would love to go on Mars

01:36:24 on one of the early.

01:36:25 You would? Yeah.

01:36:26 It would if it’s one way.

01:36:28 I’m happy to do it one way. Really?

01:36:29 Wow. Yeah.

01:36:30 I’m single if there’s ladies out there

01:36:32 that wanna start that family.

01:36:34 Let’s go out to Mars.

01:36:36 No, I think.

01:36:37 See, I have to tell you something.

01:36:38 You spoke about terror, thinking about like black holes.

01:36:42 If I actually think about going to Mars

01:36:45 and being on Mars and put myself in there fully,

01:36:49 that’s terror inducing.

01:36:51 The idea of to be in this foreign world

01:36:54 where you can’t come back,

01:36:56 where you’ve made this choice that can’t be reversed.

01:37:00 Well, at some point it may be,

01:37:01 but in that guise, that to me carries a deep sense of terror.

01:37:08 I feel that sense of terror every time Kerouac,

01:37:11 Jack Kerouac talked about this on the road

01:37:13 is when you leave a place, if you’re honest about it,

01:37:18 like life is short.

01:37:20 And when you leave a place, you move to a new place

01:37:23 and you think of all the friends, maybe family

01:37:25 you’re leaving behind as you drive over the hill,

01:37:28 that really is goodbye.

01:37:31 Like we sometimes don’t think of it that way

01:37:33 when we’re moving, but that really is goodbye to that life,

01:37:36 to the person you were, to all the people.

01:37:38 Maybe if it’s close friends, you’ll see them maybe 10, 15

01:37:41 more times in your life and that’s it.

01:37:43 And you’re saying goodbye to all of that.

01:37:46 And so in the same way, I see it as way more dramatic

01:37:50 when you’re flying away from earth and it’s like,

01:37:52 it’s goodbye to Dunkin Donuts and Starbucks.

01:37:56 And it’s goodbye to whatever, I don’t know why I picked

01:37:59 those, but some, all the things that are special to earth,

01:38:03 it’s goodbye, but that’s life.

01:38:06 I suppose more, what excites me about that kind of journey

01:38:11 is it’s a distinct contemplation of your mortality,

01:38:14 acceptance of your mortality.

01:38:16 You’re saying, just like when you take on any difficult

01:38:20 journey, it’s accepting that you’re going to die one day

01:38:25 and might as well do something truly exciting.

01:38:28 Yes, I mean, I will, you know, I’m with you on that.

01:38:31 I’m a strong believer that deep underneath human motivation

01:38:36 is this terror of our own mortality.

01:38:41 Yeah, there’s this a wonderful book that had a great

01:38:43 influence in me called The Denial of Death by Ernest Becker.

01:38:47 And when you are aware of the ways in which our mortality

01:38:52 influences our behaviors, it really does add a different

01:38:57 slant, a different kind of color to the interpretation

01:38:59 of human behavior.

01:39:01 Yeah, it’s funny that that book had a big influence

01:39:05 in me as well.

01:39:06 Oh, is that right?

01:39:07 Wow.

01:39:08 And the terror management theory and I, again,

01:39:12 from an engineering perspective, I don’t know how many

01:39:14 people that book influenced because I talk to people

01:39:19 about the fear of death and it doesn’t seem like

01:39:21 about the fear of death and it doesn’t seem to be

01:39:24 that fundamental to their experience.

01:39:26 And I don’t think on the surface it’s fundamental

01:39:28 to my experience, but it seems like an awfully,

01:39:30 in terms of we talk about models and strength theory

01:39:33 and theories, in terms of theories of this macro experience

01:39:37 of human life, it seems like a heck of a good theory

01:39:40 that the fear of death is at the kind of is the warm

01:39:43 at the core.

01:39:44 Yeah, well, I mean, and the terror management theories

01:39:47 that you make reference to, I mean, this is a group

01:39:51 of psychologists, social psychologists who devise

01:39:54 these very clever experiments, real world experiments

01:39:58 with real people, where you can directly measure

01:40:02 the hidden influence of the recognition

01:40:05 of our own mortality.

01:40:07 I mean, they’ve done these experiments where they have

01:40:09 group of people A, group of people B,

01:40:11 and the only difference between the two groups

01:40:12 is that group B, they somehow reminded them

01:40:16 in some subtle way of their own mortality.

01:40:18 Sometimes it’s nothing more than interviewing them

01:40:21 with a funeral home across the street.

01:40:23 And influence is there, but it’s subtle,

01:40:25 you don’t even think you’d take note of.

01:40:27 And they can find measurable effects that differentiate

01:40:32 the two groups to a high degree of statistical significance

01:40:36 and how they respond to certain challenges

01:40:38 or certain kinds of questions that shows a direct influence

01:40:42 of the reminder of their own mortality.

01:40:45 And I’ve read a number of these studies

01:40:48 and they are really convincing.

01:40:51 And so yeah, I would say that the reason why

01:40:54 so many people would say that, yeah, fear of mortality,

01:40:58 it’s not front and center in my worldview.

01:41:01 Yeah, I don’t really think about it much,

01:41:02 it doesn’t really matter too much.

01:41:03 The reason why they’re able to say that

01:41:05 is because this thing called culture has emerged

01:41:08 over the course of the last 10,000 years.

01:41:10 And part of the role of culture is to give us a means

01:41:14 of not thinking about our mortality all the time,

01:41:17 of not living in terror of the inevitable end,

01:41:20 which faces us all.

01:41:21 So it’s completely understandable that that’s the response

01:41:24 because that’s what culture is at least in part for.

01:41:27 Is it at least possible that the fear of death,

01:41:32 the terror of your mortality is the creative force

01:41:36 that created all of the things around us

01:41:39 at this human civilization?

01:41:41 And I think about from an engineering perspective,

01:41:45 this is where I lose all of my robotics colleagues

01:41:49 is I feel like if you want to create intelligence,

01:41:52 you have to also engineer in some kind of echoes

01:41:58 of this kind of fear.

01:42:01 Fear is such a complicated word,

01:42:03 but it’s kind of like a scarcity,

01:42:06 a scarcity of time, a scarcity of resources

01:42:10 that creates a kind of anxiety,

01:42:12 like deadlines get you to do stuff.

01:42:15 And there’s something almost fundamental to that

01:42:18 in terms of human experience.

01:42:21 Yeah, well, that’s an interesting thought.

01:42:22 So you’re basically in order to create a kind of structure

01:42:30 that mirrors what we call consciousness.

01:42:34 You’d better have that structure confront the same kinds

01:42:38 of issues and terrors that we do.

01:42:41 Consciousness and suffering only makes sense

01:42:44 in the context of death.

01:42:45 If you want to, I feel like,

01:42:48 if you want to fit into human society,

01:42:50 if you’re a robot and if you want to fit into human society,

01:42:54 you better have the same kind of existential dread,

01:42:59 the same kind of fear of mortality,

01:43:00 otherwise you’re not gonna fit in.

01:43:02 Right.

01:43:03 Right.

01:43:04 That’s good.

01:43:06 It might be wild, but it’s at least,

01:43:09 like we’re talking about all the theories

01:43:11 that are at least worth consideration.

01:43:13 I think that’s a really powerful one.

01:43:15 And definitely one has resonated with me

01:43:19 and definitely seems to capture something

01:43:25 beautifully like real about the human condition.

01:43:31 And I wonder, it’s of course,

01:43:34 it sucks to think that we need death to appreciate life,

01:43:40 but that’s just maybe the way it is.

01:43:43 Well, it’s interesting if this robotic

01:43:44 or artificially intelligent system understands the world

01:43:49 and understands the second law of thermodynamics

01:43:51 and entropy, even an artificial intelligence will realize

01:43:55 that even if its parts are really robust,

01:43:59 ultimately it will disintegrate.

01:44:02 Yeah.

01:44:03 The timescales may be different,

01:44:05 but in a way, when you think about it, it doesn’t matter.

01:44:06 Once you know that you are mortal

01:44:09 in the sense that you are not eternal,

01:44:11 the timescale hardly matters

01:44:13 because it’s either the whole thing or not.

01:44:17 Because on the scales of eternity,

01:44:19 any finite duration, however large is effectively zero

01:44:23 on the scales of eternity.

01:44:25 And so maybe it won’t be so hard for an artificial system

01:44:28 to feel that sense of mortality

01:44:32 because it will recognize the underlying physical laws

01:44:35 and recognize its own finitude.

01:44:38 And then it’ll be us and robots drinking beers,

01:44:41 looking up at the stars and just,

01:44:48 having a good laugh in awe of the whole thing.

01:44:51 Yeah.

01:44:53 I think that’s a pretty good way to end it,

01:44:55 talking about the fear of death.

01:44:57 We started talking about the meaning of life

01:44:59 and ended on the fear of death.

01:45:01 Brian, this is an incredible conversation.

01:45:03 My pleasure, thank you.

01:45:03 I enjoyed it enormously.

01:45:04 I really, really enjoyed it.

01:45:05 It’s been a long time coming.

01:45:06 I’m a huge fan of your work, a huge fan of your writing.

01:45:09 Thanks for talking to me, Brian.

01:45:10 Thank you.

01:45:12 Thanks for listening to this conversation

01:45:13 with Brian Greene.

01:45:14 To support this podcast,

01:45:16 please check out our sponsors in the description.

01:45:18 And now, let me leave you with some words from Bill Bryson.

01:45:22 “‘Physics is really nothing more

01:45:25 “’than a search for ultimate simplicity.

01:45:27 “‘But so far, all we have is a kind of elegant messiness.’”

01:45:32 Thank you for listening and hope to see you next time.