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


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The following is a conversation with Brian Greene,
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theoretical physicist at Columbia
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and author of many amazing books on physics,
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including his latest, Until the End of Time,
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Mind, Matter, and Our Search for Meaning
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in an Evolving Universe.
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This is the Lex Friedman podcast.
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To support it, please check out our sponsors
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in the description.
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And now, here's my conversation with Brian Greene.
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In your most recent book, Until the End of Time,
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you quote Bertrand Russell from a debate he had
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about God in 1948.
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He says, quote,
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"'So far as scientific evidence goes,
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"'the universe has crawled by slow stages
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"'to a somewhat pitiful result on this earth,
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"'and is going to crawl by still more pitiful stages
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"'to a condition of universal death.
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"'If this is to be taken as evidence of purpose,
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"'I can only say that the purpose is one
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"'that does not appeal to me.
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"'I see no reason, therefore,
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"'to believe in any sort of God.'"
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That's quite a depressing statement.
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As you say, this is a bleak outlook on our universe
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and the emergence of human consciousness.
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So let me ask, what is the more hopeful perspective
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to take on this story?
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Well, I think the more hopeful perspective
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is to more fully understand
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what was driving Bertrand Russell to this perspective,
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and then to see it within a broader context.
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And really, that's, in some sense,
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what my book, Until the End of Time, is all about.
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But in brief, I would say that there's a lot of truth
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to what Bertrand Russell was saying there.
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When you look at the second law of thermodynamics,
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which is the underlying scientific idea
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that's driving this notion that everything's gonna wither,
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decay, fall apart, yeah, that's true.
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Second law of thermodynamics establishes
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that disorder, entropy, in aggregate,
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is always on the rise.
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And that is indeed interpretable
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as disintegration and destruction
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over sufficiently long timescales.
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But my view is, when you recognize
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how special that makes us,
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that we are these exquisitely ordered configurations
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of particles that only will last for a blink of an eye
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in cosmological time like terms,
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the fact that we're here and we can do what we do,
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to me, that's just really something
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that inspires gratitude and wonder
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and a sense of deep purpose
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by virtue of being these unique collections of entities
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that happen to rise up, look around,
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and try to figure out where we are
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and what the heck we should do with our time.
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So it's not that I would disagree with Bertrand Russell
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in terms of the basic physics and the basic unfolding,
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but I think it's really a matter of the slant
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that you take on what it means for us.
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So maybe we'll skip around a bit,
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but let me ask the biggest possible question then.
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You said purpose.
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So what's the meaning of it all then?
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Is there a meaning to life that we can take from this,
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from this brief emergence of complexity
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that arises from simple things
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and then goes into a heat death
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that is once again returns to simple things
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as the march of the second law of thermodynamics goes on?
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I think there is,
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but I don't think it's a universal answer.
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And so I think throughout the ages,
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there has been a kind of quest for some final way
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of articulating meaning and purpose,
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whether it's God, whether it's love,
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whether it's companionship.
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I mean, many people put forward different ways
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of taking this question on,
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and there is no one right answer
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when you recognize deeply that the universe doesn't care.
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There is nothing out there that is the final answer.
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It's not as though we need a more powerful telescope
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and somehow if we can look deeply into the universe,
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all will become clear.
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In fact, the deeper we've looked,
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both literally and metaphorically,
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into the universe and into the structure of reality,
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the more it's become clear
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that we are just a momentary byproduct
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of laws of physics that don't have any emotional content.
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They don't have any intrinsic sense of meaning or purpose.
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And when you recognize that,
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you realize that searching for the universal
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for this kind of a question is a fool's errand.
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Every individual has the capacity to make their own meaning,
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to set their own purpose.
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And that's not some platitude, that is what we are.
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Because there is no fundamental answer,
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it's what you make of it.
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And however much that may sound like a hallmark card,
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this really is the deep lesson of physics and science
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more generally over the past few hundred years.
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Well, there's some level where you can objectively say
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that whatever we've got going on here,
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it's kind of peculiar.
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It's kind of special in terms of complexity.
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And maybe you can even begin to measure it
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and like come up with metrics
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where whatever we've got going on on Earth,
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these like interesting hierarchical complexities
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that form more and more sophisticated biological system,
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that seems kind of unique
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when you look at the entire universe,
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the observable part that we can see with our tools.
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I mean, so I have to ask,
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as you describe in your book once again,
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Schrodinger wrote the book,
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"'What is Life?' based on a few lectures he gave in 1944."
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So let me ask the fundamental question here.
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What is life?
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This particular thing we've got going on here,
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this pocket of complexity
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that emerged from such simple things?
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Yeah, it's a tough question.
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I asked that question even to Richard Dawkins once,
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and I already have my preconceived notion,
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which he pretty much confirmed,
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which is if one could give an answer to that question
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that allowed you to sort of draw a line in the sand
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between the not living and the living,
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then perhaps we would have the insight that we yearn for
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and trying to say, what is so special about life?
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But the fact of the matter is, it's a continuum.
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There's a continuum from the things
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that we would typically call nonliving and animate
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to the things that we obviously call animate
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and full of the currents of life.
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Somewhere in there,
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it is a question of the complexity of the structure,
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the ability of the structure to take in raw material
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from the environment and process it through a metabolism
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that allows the structure to extract energy
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and to release entropy to the wider environment.
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Somewhere in those collections of biological processes
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is the necessity or the necessary ingredients
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and processes for life,
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but drawing that line in the sand
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is not something that we're able to do,
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but I would agree with you.
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It's deeply peculiar.
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It may in fact be unique,
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but it may not.
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It could be that the universe is such
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that under fairly typical conditions,
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a star that's a well ordered source of low entropy energy,
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that's what the sun is,
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together with a planet being bathed
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by that low entropy energy,
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together with a surface that has enough
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of the raw constituents that we recognize
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are fairly commonplace result of supernova explosions
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where a star spews forth the result of the nuclear furnace
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that is the core of a star.
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It could be that all you need
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are those fairly commonplace conditions
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and maybe life naturally forms.
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Look, the James Webb Space Telescope, right?
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It's going up hopefully in December.
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And one of the goals of that mission
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is to look at atmospheres around distant planets
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and perhaps come to some sense of how special
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or not life or life as we know it is in the universe.
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Which part of the story of life,
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let's stick to Earth for a second,
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do you think is the hardest?
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If you were like a betting man,
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which part is the hardest to make happen?
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Is it the origin of life?
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Again, we haven't drawn the line where,
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as you say, the line between a rock and a rabbit.
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That part, is it complex organisms,
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like multicellular organisms?
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Is it crawling out of the ocean
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where the fish somehow figured out how to crawl around?
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Is it then the us homo sapiens,
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as we like to think of ourselves special and intelligent?
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Or is it somewhere in between?
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As you also talk about, again, very hard to know
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at which point this consciousness emerge.
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If you were to sort of took us a survey
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and made bets about other Earth like planets in the universe,
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where do you think they get stuck the most?
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Well, I would certainly say if we're gonna go all the way
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to conscious beings like ourselves,
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I would put it at the onset of consciousness,
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which again, I think is a continuum.
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I don't think it is something that you can draw the line
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in the sand, but there are obvious circumstances,
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there are obvious creatures such as ourselves
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where we do recognize a certain kind
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of self reflective conscious awareness.
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And if we think about what it would require
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for a system of living beings to acquire consciousness,
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I think that's probably the hardest part because look,
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take Earth and recognize that weren't for,
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some singular event 65 million years ago
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where this large rock slams into planet Earth
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and wipes out the dinosaurs,
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maybe the dinosaurs would still rule the planet
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and they may well have not developed
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the kind of conscious awareness that we have.
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So for billions of years on this planet,
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there was life that didn't have the kind
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of conscious awareness that we have.
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And it was an accidental event in astrophysical history
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that allowed a mammalian species like us
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to ultimately be the end product.
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And so, yeah, I could imagine there's a lot of life
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out there, but perhaps none of it's wondering
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what's the meaning of life or trying to make sense of it,
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just going about its business of survival,
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which of course is the dominant activity
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that life on this planet has practiced.
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We are a rare exception to that.
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And I really appreciate that you lean into
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some of these unanswerable questions from me today.
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But the, so you think about consciousness,
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not as like a phase shift, the binary zero one,
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you think of it as a continuum that humans somehow
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are maybe some of the most conscious beings on Earth.
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So you're, so.
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I mean, people will dispute that.
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Yes, I mean, well, and it's a very hard argument.
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People will dispute that, rocks probably
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will stay quiet on the matter.
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Maybe not, right?
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For the moment, they're waiting for their opportunity.
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But I agree that, look, even when you and I
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look at each other, I am not fully convinced
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that you're a conscious being, right?
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I mean, I think that you are.
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It's not to me.
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I mean, your behavior is such that
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that's the best explanation for what's going on.
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But of course, we're all in the position
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of only having direct awareness of our own conscious being.
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And therefore, when it comes to other creatures in the world,
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we're in a similar state of ignorance
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regarding what's actually happening inside of their head,
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if they have a head.
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And so it's hard to know how singular we are,
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but I would say based on the best available data
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and the best explanations that we can make,
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yeah, there is something special about us.
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I don't think that there are fish walking around
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and coming up with existentialism.
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I don't know that there are dogs walking around
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who've developed an understanding
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of the general theory of relativity.
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I mean, maybe we're wrong,
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but that seems the best explanation.
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What do you think is more special,
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intelligence or consciousness?
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I think consciousness.
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And I think that there's a deep connection
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between these ideas.
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They are distinct, but they're deeply connected.
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But look, I mean, to me and to, of course, many philosophers
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who actually coined a name for this,
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the hard problem of consciousness,
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David Chalmers and others,
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as a physicist, I look out at the world
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and I see it's particles governed by physical law.
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We can name them.
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We got electrons, we got quarks
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that come in various flavors and so forth.
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We have a list of ingredients that science has revealed
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and we have a list of laws that seemingly
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govern those ingredients.
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And nowhere in there is there even a hint
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that when you put those particles together in the right way,
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an inner world should turn on.
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And it's not only that there's no hint, it's insane.
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I mean, it's ridiculous.
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How could it be that a thoughtless,
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passionless, emotionless particle,
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when grouped together with compatriots,
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somehow can yield something so deeply foreign
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to the nature of the ingredients themselves?
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So answering that question,
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I think is among the deepest
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and most difficult questions that we face.
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Do you think it is in fact a really hard problem?
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Or is it possible, I think you mentioned in your book,
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that it's just like almost like a side effect.
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It's an emergent thing that's like, oh, it's nice.
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It's like a nice little feature.
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Yeah.
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Well, I mean, when people use the phrase hard problem,
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I mean, they mean in a somewhat technical sense
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that it's trying to explain something
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that seems fundamentally unavailable
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to third party objective analysis, right?
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I'm the only one that can get inside my head
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and I can tell you a lot about what's happening
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inside my head right now, it's reflected
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in what I'm saying, and you can try to deduce things
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about what's going on inside my head,
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but you don't have access to it in the way that I do.
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And so it seems like a fundamentally different
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kind of problem from the ones that we have successfully
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dealt with over the course of centuries in science,
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where we look at the motion of the moon,
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everybody can look, everybody can measure it.
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We look at the properties of hydrogen
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when you shine lasers on it,
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everybody can look at the data and understand it.
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And so it seems like a fundamentally different problem
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in that sense, it seems like it is hard
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relative to the others, but I do think ultimately
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that the explanation will be, as you recount,
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I think that a hundred years from now,
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or maybe it's a thousand, it's hard to predict
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the timescale for developments,
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but I think we'll get to a place where we'll look back
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and kind of smile at those folks in the 20th century
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and before, 21st century and before,
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who thought consciousness was so incredibly mysterious
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when the reality of it is, eh, it's just a thing that happens
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when particles come together.
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And however mysterious that feels right now,
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I think for instance, when we start to build
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conscious systems, things that you're more familiar with
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than I am, when we start to build these artificial systems
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and those systems report to us, I'm feeling sad,
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I'm feeling anxious, yeah, there's a world going on
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00:16:25.500
inside here, I think the mystery of consciousness
link |
00:16:28.580
will just begin to evaporate.
link |
00:16:30.860
Well, that's, first of all, beautifully put,
link |
00:16:33.460
and I agree with you completely,
link |
00:16:35.220
just the way you said it, it'll begin to evaporate.
link |
00:16:38.500
I have built quite a few robots
link |
00:16:41.260
and have had them do emotion, emotional type things,
link |
00:16:47.220
and it's immediate that exactly what you're saying,
link |
00:16:49.380
this kind of mystery of consciousness starts to evaporate,
link |
00:16:52.600
that the kind of need to truly understand,
link |
00:16:57.620
to solve the hard problem of consciousness disappears,
link |
00:17:00.380
because, well, I don't really care if I understand
link |
00:17:05.060
what can solve the hard problem of consciousness.
link |
00:17:07.300
That thing sure as heck looks conscious.
link |
00:17:09.660
I feel like that way when I interact with a dog.
link |
00:17:12.840
I don't need to solve the problem of consciousness
link |
00:17:16.420
to be able to interact and richly enjoy the experience
link |
00:17:22.740
with this other living being.
link |
00:17:24.380
Obviously, same thing with other humans.
link |
00:17:26.440
I don't need to fully understand it.
link |
00:17:27.940
And there's some aspect, maybe this is a little bit
link |
00:17:31.020
too engineering focused, but there's some aspect
link |
00:17:33.540
in which it feels like consciousness is just a nice trick
link |
00:17:38.660
to help us communicate with each other.
link |
00:17:41.740
It sounds ridiculous to say, but sort of the ability
link |
00:17:47.540
to experience the world is very useful,
link |
00:17:51.220
in a subjective sense, is very useful to put yourself
link |
00:17:55.160
in that world and to be able to describe the experience
link |
00:17:58.340
to others.
link |
00:17:59.180
It could be just a social and the merge.
link |
00:18:01.840
Obviously, animals, the sort of more primitive animals
link |
00:18:04.500
might experience consciousness in some more primitive way,
link |
00:18:08.780
but this kind of rich, subjective experience
link |
00:18:12.300
that we think about as humans, I think it's probably
link |
00:18:14.540
deeply coupled with language and poetry.
link |
00:18:17.840
Yeah, that resonates with my view as well.
link |
00:18:20.680
I mean, there's a scientist, maybe you've spoken to him,
link |
00:18:23.340
Michael Graziano from Princeton.
link |
00:18:25.140
Yeah, he's developed ideas of consciousness that,
link |
00:18:29.620
look, I don't think they solve the problem,
link |
00:18:31.620
but I think they do illuminate it in an interesting way
link |
00:18:34.340
where basically we are not aware
link |
00:18:39.020
of all the underlying physiochemical processes
link |
00:18:43.060
that make our brains and our inner worlds
link |
00:18:45.900
tick the way they do.
link |
00:18:48.020
And because of that dissociation between sensation
link |
00:18:52.220
and the physics of it and the chemistry of it
link |
00:18:55.140
and the biology of it, it feels like our minds
link |
00:18:58.900
and our inner worlds are just untethered,
link |
00:19:00.960
like floating somewhere in this gray matter
link |
00:19:04.640
inside of our heads.
link |
00:19:06.500
And the way I like to think of it is like,
link |
00:19:08.580
look, if you were in a dark room, right,
link |
00:19:13.980
and I had glow in the dark paint on my fingers,
link |
00:19:17.380
so all you saw was my fingers dancing around,
link |
00:19:20.380
there'd be something mysterious.
link |
00:19:21.980
How could those fingers be doing that?
link |
00:19:24.460
And then you turn on the light, you realize,
link |
00:19:25.300
oh, there's this arm underlying it,
link |
00:19:27.700
and that's the deep physical connection explains it all.
link |
00:19:30.660
And I think that's what we're missing,
link |
00:19:32.620
the deep physical connection between what's happening
link |
00:19:35.800
up here and what is responsible for it
link |
00:19:38.540
in a physical, chemical, biological way.
link |
00:19:41.420
And so to me, that at least gives me some understanding
link |
00:19:43.660
of why consciousness feels so mysterious
link |
00:19:46.740
because we are suppressing all of the underlying science
link |
00:19:51.580
that ultimately is responsible for it.
link |
00:19:53.540
And one day we will reveal that more fully,
link |
00:19:55.940
and I think that will help us tether this experience
link |
00:19:59.260
to something quite tangible in the world.
link |
00:20:01.540
I wonder if the mystery is an important component
link |
00:20:08.140
of enjoying something.
link |
00:20:10.120
So once we know how this thing works,
link |
00:20:14.180
maybe we will no longer enjoy this conversation.
link |
00:20:19.220
We'll seek other sources of enjoyment,
link |
00:20:21.260
but this is, again, from an engineering perspective,
link |
00:20:25.340
I wonder if the mystery is an important component.
link |
00:20:29.020
Well, have you ever seen,
link |
00:20:31.580
there's this beautiful interview
link |
00:20:33.500
that Richard Feynman did,
link |
00:20:36.940
great Nobel laureate physicist responsible
link |
00:20:39.620
for a lot of our understanding of quantum mechanics,
link |
00:20:42.060
quantum field theory and so forth.
link |
00:20:43.060
And he was in a conversation with an interviewer
link |
00:20:46.520
where he noted that some people feel
link |
00:20:48.580
like once the mystery is gone,
link |
00:20:51.060
once science explains something,
link |
00:20:55.900
the beauty goes away, the wonder of it goes away.
link |
00:20:58.300
And he was emphasizing in his response to that,
link |
00:21:02.060
he's like, no, that's not the right way of thinking about it.
link |
00:21:05.060
He says, look, when I look at a rose,
link |
00:21:07.700
he says, yeah, I can still deeply enjoy the aroma,
link |
00:21:11.540
the color, the texture.
link |
00:21:13.940
He says, but what I can do that you can't,
link |
00:21:15.920
if you're not a physicist,
link |
00:21:16.820
I can look more deeply and understand
link |
00:21:19.340
where the red comes from, where the aroma comes from,
link |
00:21:21.520
where the structure comes from.
link |
00:21:22.740
He says, that only augments my wonder.
link |
00:21:27.740
It only augments my experience.
link |
00:21:29.900
It doesn't flatten it or take away from it.
link |
00:21:32.580
So I sort of take that as a bit of a motto in some sense
link |
00:21:38.780
that there is a wonder that comes from a kind of ignorance.
link |
00:21:43.820
And I don't mean that in a derogatory sense,
link |
00:21:45.740
but just from not knowing.
link |
00:21:47.280
So there is a wonder that comes from mystery.
link |
00:21:49.700
There's another kind of wonder that comes from knowing
link |
00:21:53.500
and deep knowing.
link |
00:21:55.860
And I think that kind of wonder has its own
link |
00:21:59.260
special character that in some ways can be more gratifying.
link |
00:22:04.640
I hope he's right.
link |
00:22:06.080
I hope you're right.
link |
00:22:07.460
But there's also, I remember he said something
link |
00:22:10.300
about like science is an onion or something like that.
link |
00:22:13.940
You can peel back, you can keep peeling back.
link |
00:22:16.540
I mean, there is also, when you understand something,
link |
00:22:19.580
there's always a sense that there's more mystery
link |
00:22:22.060
to understand.
link |
00:22:23.380
Like you never get to the bottom of the mystery.
link |
00:22:27.060
But I think it's also different than,
link |
00:22:28.780
you know, I don't think you can analogize say
link |
00:22:31.460
to a magician, right?
link |
00:22:33.620
A magician does some trick.
link |
00:22:35.360
You learn how it sounds like, oh my God,
link |
00:22:37.780
that's ridiculous when you find.
link |
00:22:39.520
But nature is perhaps the best magician
link |
00:22:42.780
if you wanna try to make the analogy there
link |
00:22:45.060
because when you peel things back and you understand
link |
00:22:48.860
how it is that things have color and you have electrons,
link |
00:22:53.220
dancing from one orbital to another,
link |
00:22:56.420
emitting photons at very particular wavelengths
link |
00:22:59.220
that are described by these beautiful equations
link |
00:23:01.900
of quantum electrodynamics,
link |
00:23:03.460
part of which that Feynman developed,
link |
00:23:06.100
it gives you a greater sense of awe
link |
00:23:09.460
when the curtain is pulled back
link |
00:23:11.700
than what happens in other circumstances
link |
00:23:14.340
where it does flatten it completely.
link |
00:23:16.380
Yeah, it's very possible then say in physics
link |
00:23:18.540
that we arrive at a theory of everything
link |
00:23:21.400
that unifies the laws of physics
link |
00:23:23.460
and has a very strong understanding
link |
00:23:25.000
of the fabric of reality,
link |
00:23:26.540
even like from the big bang to today,
link |
00:23:30.380
it's possible that that understanding
link |
00:23:33.000
is only going to elevate our appreciation
link |
00:23:36.520
of this whole thing.
link |
00:23:37.360
Yeah, I think it will.
link |
00:23:38.260
I think it will.
link |
00:23:39.100
I mean, I think it has so far.
link |
00:23:40.980
But the other side of it which you emphasize
link |
00:23:43.380
is it's not like science somehow reaches an end, right?
link |
00:23:48.380
There are certain categories of questions
link |
00:23:50.700
that do reach an end.
link |
00:23:52.260
I think we one day will close the book
link |
00:23:54.340
on nature's ingredients and the fundamental laws.
link |
00:23:57.500
Now that we can't prove that,
link |
00:23:58.900
maybe it goes on forever, smaller and smaller,
link |
00:24:01.660
maybe there are deeper and deeper laws,
link |
00:24:03.140
but I don't think so.
link |
00:24:03.980
I think that there's going to be a collection
link |
00:24:06.180
of ingredients and a collection of basic laws.
link |
00:24:08.620
That chapter will close, but it's one chapter.
link |
00:24:12.940
Now we take that knowledge and we try to understand
link |
00:24:16.220
how the world builds the structures that it does,
link |
00:24:19.740
from planets to people to black holes
link |
00:24:23.380
to the possibility of other universes
link |
00:24:25.640
and every step of the way,
link |
00:24:27.700
the collection of questions
link |
00:24:29.580
that we don't know the answer to only blossoms.
link |
00:24:32.300
And so there's a deep sense of gratification
link |
00:24:36.760
from understanding certain qualities of the world.
link |
00:24:39.020
But I would say that if you take a ratio
link |
00:24:42.500
of what we understand to the things that we know
link |
00:24:45.780
that we don't yet understand,
link |
00:24:47.680
that ratio keeps getting smaller and smaller
link |
00:24:50.020
because the things that we know that we don't understand
link |
00:24:52.140
grows larger and larger.
link |
00:24:54.300
Do you have a hope that we solve that theory
link |
00:24:56.980
of everything puzzle in the next few decades?
link |
00:25:00.180
So there's been a bunch of attempts from string theory
link |
00:25:03.820
to all kinds of attempts at trying to solve quantum gravity
link |
00:25:07.500
or basically come up with a theory for quantum gravity.
link |
00:25:10.260
There's a lot of complexities to this.
link |
00:25:13.260
One, for experimental validation,
link |
00:25:16.260
you have to observe effects
link |
00:25:17.820
that are very difficult to measure.
link |
00:25:20.420
So you have to build,
link |
00:25:21.340
like that's like an engineering challenge.
link |
00:25:23.660
And then there's the theory challenge,
link |
00:25:25.260
which is like, it seems very difficult
link |
00:25:28.380
to connect the laws of gravity to quantum mechanics.
link |
00:25:31.820
Do you have a hope or are we hopelessly stuck?
link |
00:25:35.500
Well, I have to have to have a hope.
link |
00:25:37.620
I mean, it's in some sense,
link |
00:25:39.640
but I devote at least part of my professional life toward
link |
00:25:43.660
trying to make progress on.
link |
00:25:45.020
And I'm glad you used the phrase quantum gravity.
link |
00:25:47.540
I'm not a great fan of the theory of everything phrase
link |
00:25:50.300
because it does make other scientists feel like
link |
00:25:53.320
if they're not working on this, what are they working on?
link |
00:25:55.620
Man's like, there's not much left
link |
00:25:57.500
when you're talking about theory of everything.
link |
00:25:58.860
Biology is just small details we'll figure out.
link |
00:26:01.460
Yeah, so it is really trying to put gravity
link |
00:26:04.180
and quantum mechanics together.
link |
00:26:06.180
And since I was a college kid,
link |
00:26:08.580
I was deeply fascinated with gravity.
link |
00:26:12.980
And as I learned quantum mechanics,
link |
00:26:15.480
the notion of physicists being stumped
link |
00:26:19.000
and trying to blend them together,
link |
00:26:20.560
how could one not get fired up
link |
00:26:22.260
about maybe contributing something to that journey?
link |
00:26:25.940
And so we've been on this,
link |
00:26:27.660
I've been on this for 30 years since I was a student.
link |
00:26:29.820
We have made progress.
link |
00:26:31.800
We do have ideas.
link |
00:26:32.860
You mentioned string theory is one possible scenario.
link |
00:26:36.240
It's not stuck.
link |
00:26:37.520
String theory is a vibrant field of research
link |
00:26:40.900
that is making incredible progress,
link |
00:26:43.600
but we've not made progress
link |
00:26:45.980
on this issue of experimental verification validation,
link |
00:26:49.460
which is, you know, it is a vital part of the story.
link |
00:26:53.940
So I would have hoped that by now
link |
00:26:55.740
we would have made contact with observation.
link |
00:26:58.620
If you would have interviewed me back in the 80s
link |
00:27:01.620
when I was, you know, a wild bright eyed kid
link |
00:27:04.940
trying to make headway working 18 hours a day
link |
00:27:07.140
and this sort of stuff,
link |
00:27:07.980
I would have said, yeah, by 2021,
link |
00:27:10.380
yeah, we're gonna know whether it's right or wrong.
link |
00:27:12.160
We'll have made contact.
link |
00:27:13.620
I would have said, look,
link |
00:27:14.460
there may be certain mathematical puzzles
link |
00:27:16.020
that we've yet to work out,
link |
00:27:17.220
but we'll know enough to make contact with experiment.
link |
00:27:19.900
That has not happened.
link |
00:27:21.580
On the other hand,
link |
00:27:22.540
if you would have interviewed me back then and asked me,
link |
00:27:25.200
will we be able to talk about detailed qualities
link |
00:27:29.140
of black holes and understand them at the level of detail
link |
00:27:34.140
that we actually, I would have said,
link |
00:27:37.460
no, I don't think that we're gonna be able to do that.
link |
00:27:39.820
Will we have an exact formulation of string theory
link |
00:27:42.660
in certain circumstances?
link |
00:27:43.980
No, I don't think we're gonna have that, and yet we do.
link |
00:27:46.600
So it's just to say,
link |
00:27:47.440
you don't know where the progress is going to happen,
link |
00:27:51.020
but yes, I do hold out hope
link |
00:27:52.980
that maybe before I move on to wherever,
link |
00:27:56.740
I don't think there is an after,
link |
00:27:58.100
but I would love before I leave this earth
link |
00:28:01.780
to know the answer, but science and the universe,
link |
00:28:06.900
it's not about pleasing any individual, it is what it is.
link |
00:28:11.620
And so we just press onward and we'll see where it goes.
link |
00:28:15.000
So in terms of string theory,
link |
00:28:17.100
if I just look from an authoritative perspective currently
link |
00:28:20.400
at the theoretical physics community,
link |
00:28:22.480
string theory as a theory has been very popular
link |
00:28:26.500
for a few decades, but has recently fallen out of favor,
link |
00:28:30.700
or at least there's been like, you know,
link |
00:28:32.940
it became more popular to kind of ask the question,
link |
00:28:36.980
is string theory really the answer?
link |
00:28:39.380
Where do you fall on this?
link |
00:28:40.900
Like, how do you make sense of this puzzle?
link |
00:28:43.220
Why do you think it's fallen out of favor?
link |
00:28:45.480
Yeah, so I would actually challenge the statement
link |
00:28:47.900
that it's fallen out of favor.
link |
00:28:50.300
I would say that any field of research when it's new
link |
00:28:55.180
and it's the bright, shiny bicycle
link |
00:28:58.740
that no one has yet seen on that block,
link |
00:29:01.060
yeah, it's gonna attract attention
link |
00:29:03.060
and the news outlets are gonna cover it
link |
00:29:06.100
and students are gonna flock to it, sure.
link |
00:29:09.200
But as a field matures, it does shed those qualities
link |
00:29:14.260
because it's no longer as novel as it was
link |
00:29:17.260
when it was first introduced 30, 40 years ago,
link |
00:29:20.340
but you need to judge it by a different standard.
link |
00:29:22.660
You need to judge it by is it making progress
link |
00:29:26.220
on foundational issues deepening our understanding
link |
00:29:29.380
of the subject and by that measure,
link |
00:29:31.620
string theory is scoring very high.
link |
00:29:36.580
Now, at the same time, you also need to judge
link |
00:29:39.280
whether it makes contact with experiment
link |
00:29:41.100
as we discussed before too
link |
00:29:42.900
and in that measure, we're still challenged.
link |
00:29:45.900
So I would say that many string theorists,
link |
00:29:49.220
myself included, are very sober about the theory.
link |
00:29:54.220
It has the tremendous progress that it had 30, 40 years ago
link |
00:29:58.340
that hasn't gone away, but we become better equipped
link |
00:30:02.780
at assessing the long journey ahead
link |
00:30:06.700
and that was something that we weren't particularly good at
link |
00:30:09.580
back, say, in the 80s.
link |
00:30:10.860
Look, when I was just starting out in the field,
link |
00:30:13.900
there was a sense of physics is about to end.
link |
00:30:18.100
String theory is about to be the be all and end all
link |
00:30:21.940
final unified theory and that will bring this chapter
link |
00:30:26.580
to a close.
link |
00:30:27.780
Now, I have to say, I think it was more the younger
link |
00:30:30.180
physicists who were saying that.
link |
00:30:31.840
Some of them were seasoned,
link |
00:30:32.900
even if they were pro string theory at the time.
link |
00:30:35.820
I don't know if they were rolling their eyes,
link |
00:30:37.700
but they knew that it was gonna be a long, long journey.
link |
00:30:41.780
I think people like John Schwartz,
link |
00:30:43.860
one of the founders of string theory,
link |
00:30:45.180
Michael Green, no relation to me,
link |
00:30:46.620
founders of the theory, Edward Witten,
link |
00:30:49.660
one of the main people driving the theory
link |
00:30:52.100
back then and today.
link |
00:30:53.900
I think they knew that we were in for a long haul
link |
00:30:58.900
and that's the nature of science,
link |
00:31:01.780
quick hits that resolve everything few and far between.
link |
00:31:06.180
And so if you were in for the quick solution
link |
00:31:12.220
to the big questions of the world,
link |
00:31:13.860
then you would have been disappointed
link |
00:31:15.100
and I think there were people who were disappointed
link |
00:31:16.820
and moved on and work on other subjects.
link |
00:31:19.740
If you're in in the way that Einstein was in
link |
00:31:23.340
for a lifetime of investigation to try to see
link |
00:31:27.780
what the answers to the deep questions would be,
link |
00:31:30.660
then I think string theory has been a rich source
link |
00:31:33.860
of material that has kept so many people deeply engaged
link |
00:31:39.100
in moving the frontier forward.
link |
00:31:41.300
There's a few qualities about string theory,
link |
00:31:43.020
which are weird.
link |
00:31:45.140
I mean, a lot of physics is just weird and beautiful.
link |
00:31:48.940
So let me ask the question,
link |
00:31:50.220
what do you use most beautiful about string theory?
link |
00:31:53.140
Well, what attracted me to the theory at the outset
link |
00:31:57.900
beyond it's putting gravity and quantum mechanics together,
link |
00:32:00.980
which I think is its true claim to fame,
link |
00:32:03.940
at least on paper, it's able to do that.
link |
00:32:06.740
What attracted me to the theory was the fact
link |
00:32:08.260
that it requires extra dimensions of space.
link |
00:32:11.140
And this was an idea that intrigued me in a very deep way,
link |
00:32:16.900
even before I really understood what it meant.
link |
00:32:20.620
I somehow had, I mean, talk about sort of
link |
00:32:24.020
the emotional part of consciousness and the cognitive part
link |
00:32:27.180
in some, perhaps you call it strange,
link |
00:32:29.460
in some strange emotional way,
link |
00:32:31.940
I was enamored with Einstein's general relativity,
link |
00:32:35.420
the idea of curved space and time
link |
00:32:37.740
before I really knew what it meant.
link |
00:32:39.420
It just spoke to me, I don't know how else to say it.
link |
00:32:43.300
And then when I subsequently learned
link |
00:32:46.620
that people had thought about more dimensions of space
link |
00:32:49.620
than we can see and how those extra dimensions
link |
00:32:52.380
would be vital to a deep understanding
link |
00:32:55.060
of the things that we do see in this world,
link |
00:32:56.900
four, five, six dimensions might explain
link |
00:32:59.740
why there are certain forces and particles
link |
00:33:01.740
and how they behave.
link |
00:33:03.340
To me, this was like amazing, utterly amazing.
link |
00:33:06.300
And then when I learned that string theory
link |
00:33:09.060
embraced all these ideas,
link |
00:33:10.700
embraced the general theory of relativity,
link |
00:33:12.500
embraced quantum mechanics,
link |
00:33:13.620
embraced the possibility of extra dimensions,
link |
00:33:17.260
then I was hooked.
link |
00:33:19.140
And so when I was a graduate student,
link |
00:33:21.460
we would just spend hours,
link |
00:33:23.780
we, I mean, a couple of other graduate students and myself
link |
00:33:26.260
who had sort of worked really well together,
link |
00:33:29.300
it was at Oxford in England,
link |
00:33:30.940
we would work these enormous numbers of hours a day
link |
00:33:33.900
trying to understand the shapes of these extra dimensions,
link |
00:33:36.340
the geometry of them, what those geometrical shapes
link |
00:33:39.820
for the extra dimensions would imply
link |
00:33:41.460
for things that we see in the world around us.
link |
00:33:43.780
And it was a heady, heady time.
link |
00:33:46.660
And that kind of excitement has sort of filtered through
link |
00:33:50.500
over the decades.
link |
00:33:51.420
But I'd say that's really the part of the theory
link |
00:33:57.020
that I think really hooked me most strongly.
link |
00:34:00.260
How are we supposed to think about those extra dimensions?
link |
00:34:02.860
I was supposed to imagine actual physical reality
link |
00:34:05.940
or is this more in the space of mathematics
link |
00:34:08.620
that allows you to sort of come up with tricks
link |
00:34:11.620
to describe the four dimensional reality
link |
00:34:14.620
that we more directly perceive?
link |
00:34:17.420
No one really knows the answer, of course,
link |
00:34:19.700
but if I take the most straightforward approach
link |
00:34:22.700
to string theory,
link |
00:34:23.540
you really are imagining that these dimensions are there,
link |
00:34:28.020
they're real.
link |
00:34:28.860
I mean, just as you would say
link |
00:34:30.780
that the three space dimensions around us,
link |
00:34:33.380
left, right, back, forth, up, down,
link |
00:34:35.700
yeah, they're real, they're here.
link |
00:34:37.900
We are immersed within those dimensions.
link |
00:34:40.340
These other dimensions are as real as these
link |
00:34:44.500
with the one difference being their shape and their size
link |
00:34:47.620
differs from the shape and size of the dimensions
link |
00:34:50.500
that we have direct access to through human experience.
link |
00:34:54.660
And one approach imagines that these extra dimensions
link |
00:34:57.700
are tightly coiled up, curled up,
link |
00:35:01.060
crushed together, if you will,
link |
00:35:03.380
into a beautiful geometrical form
link |
00:35:06.500
that's all around us,
link |
00:35:08.820
but just too small for us to detect with our eyes,
link |
00:35:11.940
too small for us to detect
link |
00:35:13.300
even with the most powerful equipment that we have.
link |
00:35:16.220
Nevertheless, according to the mathematics,
link |
00:35:18.940
the size and the shape of those extra dimensions
link |
00:35:21.580
leaves an imprint in the world that we do have access to.
link |
00:35:24.940
So one of the ways that we have hoped yet to achieve
link |
00:35:28.980
to make contact with experimental physics
link |
00:35:31.820
is to see a signature of those extra dimensions
link |
00:35:34.460
in places like the Large Hadron Collider
link |
00:35:36.580
in Geneva, Switzerland.
link |
00:35:38.220
And it hasn't happened yet, doesn't mean it won't happen,
link |
00:35:41.420
but that would be a stunning moment
link |
00:35:44.700
in the history of the species
link |
00:35:46.140
if data that we acquired in these dimensions
link |
00:35:50.140
gives us kind of incontrovertible evidence
link |
00:35:53.420
that these dimensions are not the only dimensions.
link |
00:35:55.860
I mean, how mind blowing would that be?
link |
00:35:59.220
So with the Large Hadron Collider,
link |
00:36:00.980
it would be something in the movement of the particles
link |
00:36:03.260
or also the gravitational waves potentially be a place
link |
00:36:07.740
where you can detect signs of multiple dimensions,
link |
00:36:10.180
like with something like LIGO, but much more accurate.
link |
00:36:12.340
In principle, all of these can work.
link |
00:36:14.580
So one of the experiments that we had high hopes for,
link |
00:36:18.340
but by high hopes, I'm actually exaggerating.
link |
00:36:20.980
One of the experiments that we imagined
link |
00:36:24.340
might in the best of all circumstances,
link |
00:36:26.580
yield some insight.
link |
00:36:27.540
We weren't with bated breath waiting for the result.
link |
00:36:30.100
We knew it was a long shot.
link |
00:36:31.620
When you slam protons together at very high speed
link |
00:36:34.660
of the Large Hadron Collider,
link |
00:36:35.980
if there are these extra dimensions
link |
00:36:37.580
and if they have the right form,
link |
00:36:39.660
and that's a hypothesis that may not be correct,
link |
00:36:43.180
but when the protons collide,
link |
00:36:44.940
they can create debris, energetic debris
link |
00:36:48.060
that can in some sense leave our dimensions
link |
00:36:50.940
and insert itself into the other dimensions.
link |
00:36:53.780
And the way you'd recognize that is,
link |
00:36:56.380
there'd be more energy before the collision
link |
00:36:58.620
and after the collision because the debris
link |
00:37:00.940
would have taken energy away from the place
link |
00:37:03.780
where our detectors can detect it.
link |
00:37:06.540
So that's one real concrete way
link |
00:37:09.060
that you could find evidence for extra dimensions.
link |
00:37:12.020
But yeah, since extra dimensions are of space
link |
00:37:16.020
and gravity is something that exists within,
link |
00:37:19.380
in fact is associated with the shape of space,
link |
00:37:22.780
gravitational waves in principle
link |
00:37:25.220
can provide a kind of cat scan of the extra dimensions
link |
00:37:31.180
if you had sufficient control over those processes.
link |
00:37:35.340
We don't yet, but perhaps one day we will.
link |
00:37:38.660
Does it make you sad a little bit?
link |
00:37:41.420
Maybe looking out into the future,
link |
00:37:43.020
you mentioned Ed Witten that no Nobel prizes
link |
00:37:46.140
have been given yet related to string theory.
link |
00:37:48.940
Do you think they will be?
link |
00:37:50.300
Do you think you have to have experimental validation
link |
00:37:53.620
or can a Nobel prize be given?
link |
00:37:55.500
Which I don't think has been given for quite a long time
link |
00:37:58.620
for purely sort of theoretical contribution.
link |
00:38:01.940
Yeah, it's certainly as a matter of historical precedent
link |
00:38:06.140
has been the case that those who win the prize
link |
00:38:09.020
have established, investigated, illuminated
link |
00:38:14.180
a demonstrably real quality of the world.
link |
00:38:18.620
So gravitational waves, the prize was awarded
link |
00:38:22.740
after they were detected, not the mathematics of it,
link |
00:38:26.580
but the actual detection of it.
link |
00:38:28.980
The Higgs particle, it was an idea that came
link |
00:38:32.220
from the 1960s, Peter Higgs and others in fact.
link |
00:38:36.220
And it wasn't until 2012 on July 4th
link |
00:38:41.420
when the announcement came that this particle
link |
00:38:43.300
had been detected at the Large Hadron Collider
link |
00:38:45.660
that people viewed it as eligible for the Nobel prize.
link |
00:38:49.140
The idea was there, the math was there,
link |
00:38:50.700
but you needed to confirm it.
link |
00:38:52.780
Indeed, the prize ultimately was awarded.
link |
00:38:55.260
So I'm not surprised.
link |
00:38:56.940
In fact, I would have been surprised
link |
00:38:59.540
if a Nobel prize had been awarded
link |
00:39:02.140
in the arena of string theory
link |
00:39:04.340
because it's far too speculative right now.
link |
00:39:07.180
It's far too hypothetical.
link |
00:39:09.060
In fact, I am sympathetic to the view
link |
00:39:13.220
that it really shouldn't be called string theory.
link |
00:39:15.900
It degrades the word theory
link |
00:39:18.540
because theory in science, of course,
link |
00:39:20.900
means the best available explanation
link |
00:39:23.740
for the things that we observe in the world,
link |
00:39:25.940
the things that we measure in experiments about the world.
link |
00:39:30.820
And string theory does not do that, at least not yet.
link |
00:39:34.320
So it really should be the string hypothesis, right?
link |
00:39:37.620
We're at an earlier stage of development
link |
00:39:40.500
and that's not the kind of thing
link |
00:39:42.320
that Nobel prizes should be awarded for.
link |
00:39:45.580
What do you think about the critics out there, Peter White,
link |
00:39:48.700
he's from Columbia too, I think Sabine Hafenstatter.
link |
00:39:53.380
Is that a healthy thing or should we sort of focus
link |
00:39:56.340
on sort of the optimism of these hypotheses?
link |
00:39:59.540
Yeah, it's actually a good way that you frame it
link |
00:40:03.060
because I'm always somewhat repelled
link |
00:40:09.060
by views of the world that start from the negative.
link |
00:40:14.060
Try to cut down an idea, try to say that's the wrong way
link |
00:40:18.820
of thinking about things and so on.
link |
00:40:21.540
I'm much more drawn, maybe because I'm an optimist,
link |
00:40:24.980
I don't know, I'm much more drawn to those
link |
00:40:27.460
who go out into the world with new ideas.
link |
00:40:30.660
And don't try to cut down one idea,
link |
00:40:34.020
but rather present another one that might be better.
link |
00:40:38.020
And so you make the first idea, maybe string theory irrelevant
link |
00:40:41.940
because you've come up with the better approach
link |
00:40:46.340
to the world.
link |
00:40:47.580
So do I think it's healthy?
link |
00:40:49.040
Look, I think having a wide range of views
link |
00:40:53.020
and perspectives is generally a healthy thing.
link |
00:40:56.600
I think it's good to have arguments within a subject
link |
00:41:00.460
in order that you stay fresh and you stay focused
link |
00:41:04.060
on the things that matter.
link |
00:41:06.420
But in the end of the day,
link |
00:41:07.740
I think it's a more vital contribution
link |
00:41:11.940
to give us something new
link |
00:41:13.260
rather than to criticize something that's there.
link |
00:41:15.540
Yeah, I'm totally with you.
link |
00:41:17.020
But it could be just the nature of being an optimist
link |
00:41:19.780
and also just a love of engineering.
link |
00:41:24.220
It helps nobody by criticizing the rocket
link |
00:41:29.300
that somebody else built,
link |
00:41:30.580
just build a bigger, cheaper, better rocket.
link |
00:41:34.560
Right, exactly.
link |
00:41:36.580
And that seems to be how human civilization
link |
00:41:38.980
can progress effectively.
link |
00:41:41.420
We've mentioned the second law of thermodynamics.
link |
00:41:44.900
I gotta ask you about time.
link |
00:41:46.860
Yeah.
link |
00:41:47.700
And do you think of time as emergent
link |
00:41:51.380
or fundamental to our universe?
link |
00:41:53.700
I like to think of it as emergent.
link |
00:41:56.080
I don't have a solid reason for that perspective.
link |
00:42:00.940
I have a lot of hints of reasons
link |
00:42:02.720
that some of which come out of string theory
link |
00:42:04.340
and quantum gravity that perhaps would be worth talking about.
link |
00:42:09.140
But what I would say is,
link |
00:42:11.980
time is the most familiar quality of experience
link |
00:42:17.020
because there's nothing that takes place
link |
00:42:18.940
that doesn't take place within an interval of time.
link |
00:42:22.140
And yet at the same time,
link |
00:42:24.500
it is perhaps the most mysterious quality of the world.
link |
00:42:28.420
So it's a wonderful confluence
link |
00:42:31.020
of the familiar and the deeply mysterious
link |
00:42:33.500
all in one little package.
link |
00:42:35.980
If you were to ask me, what is time?
link |
00:42:38.580
I don't really know.
link |
00:42:39.760
I don't think anybody does.
link |
00:42:41.000
I can say what time gives us,
link |
00:42:45.220
it allows us the language for talking about change.
link |
00:42:48.740
It allows us to envision the events of the universe
link |
00:42:52.580
being spread out in this temporal timeline.
link |
00:42:55.860
And in that way, allows us to see the patterns
link |
00:42:59.080
that unfold within time.
link |
00:43:01.640
I mean, time allows us the structure and the organization
link |
00:43:05.120
to think about things in that kind of a progression.
link |
00:43:08.920
But what actually is it?
link |
00:43:11.420
I don't really know.
link |
00:43:12.740
And that's so strange because we can measure it, right?
link |
00:43:16.380
I mean, there are laboratories in the world
link |
00:43:19.060
that measure this thing called time
link |
00:43:21.100
to spectacular precision.
link |
00:43:24.020
But if you go up to the folks and say,
link |
00:43:28.460
what is it that you're actually measuring?
link |
00:43:31.900
I don't know that they can really articulate
link |
00:43:34.540
the kind of answer that you would expect
link |
00:43:37.180
from those who are engineering a device
link |
00:43:39.360
that can measure something called time
link |
00:43:41.460
to that level of precision.
link |
00:43:43.100
So it's a very curious combination.
link |
00:43:46.860
What do you make of the one way feeling of causality?
link |
00:43:51.260
Like is causality a thing or is that too just a human story
link |
00:43:56.260
that we put on top of this emergent phenomenon of time?
link |
00:44:00.780
I don't know.
link |
00:44:02.220
I can give you my guess and my intuition about it.
link |
00:44:05.940
I do think that at the macroscopic level,
link |
00:44:09.180
if we're talking about sort of the human experience of time,
link |
00:44:11.280
I do think at the macroscopic level,
link |
00:44:13.320
there is a fundamental notion of causality
link |
00:44:17.180
that does emerge from a starting point
link |
00:44:20.060
that may not have causality built in.
link |
00:44:21.760
So I certainly would allow that at the deepest description
link |
00:44:25.540
of reality when we finally have that on the table,
link |
00:44:28.880
we may not see causality directly at that fundamental level.
link |
00:44:33.540
But I do believe that we will understand
link |
00:44:36.240
how to go from that fundamental level
link |
00:44:38.340
to a world where at the macroscopic level,
link |
00:44:41.440
there is this notion of A causes B.
link |
00:44:44.460
A notion that Einstein deeply embraced
link |
00:44:47.660
in his special theory of relativity
link |
00:44:49.140
where he showed that time has qualities
link |
00:44:51.840
that we wouldn't expect based on experience.
link |
00:44:54.280
You and I, if we move relative to each other,
link |
00:44:56.740
our clocks tick off time at different rate.
link |
00:44:59.780
And our clocks is just a means of measuring
link |
00:45:02.540
this thing called time.
link |
00:45:03.520
So this is really time that we're talking about.
link |
00:45:05.860
Time for you and time for me are different
link |
00:45:08.100
if we're in relative motion.
link |
00:45:09.280
He then shows in the general theory of relativity
link |
00:45:11.500
that if we're experiencing different gravity,
link |
00:45:15.040
different gravitational fields
link |
00:45:16.300
or actually more precisely
link |
00:45:17.280
different gravitational potentials,
link |
00:45:19.180
time will elapse for us at different rates.
link |
00:45:21.660
These are things that are astoundingly strange
link |
00:45:25.960
that give rise to a scientific notion of time travel.
link |
00:45:29.700
Okay, so this is how far Einstein took us
link |
00:45:33.440
in wiping away the old understanding of time
link |
00:45:37.180
and injecting a new understanding of its qualities.
link |
00:45:40.420
So there's so much about time that's counterintuitive,
link |
00:45:44.420
but I do not think that we're ever going
link |
00:45:46.780
to wipe away causality at the macroscopic level.
link |
00:45:50.300
At the macroscopic, I mean, there's so many interesting
link |
00:45:52.340
things at the macroscopic level
link |
00:45:53.900
that may only exist at the macroscopic level.
link |
00:45:56.680
Like we already talked about consciousness
link |
00:45:59.200
that very well could be one of the things.
link |
00:46:01.060
You mentioned time travel.
link |
00:46:02.260
So, I mean, according to Einstein and in general,
link |
00:46:09.180
what types of travel do you think
link |
00:46:11.680
our physical universe allows?
link |
00:46:14.020
Well, it certainly allows time travel to the future.
link |
00:46:17.060
And I'm not talking about the silly thing
link |
00:46:18.660
that you and I are now going into the future
link |
00:46:21.420
second by second by second.
link |
00:46:22.420
I'm talking about really the diversion
link |
00:46:24.700
that you see in Hollywood, at least in terms
link |
00:46:27.460
of its net effect, whereby an individual
link |
00:46:32.260
can follow an Einsteinian strategy
link |
00:46:36.460
and propel themselves into the future
link |
00:46:40.660
in some sense more quickly.
link |
00:46:42.260
So if I wanted to see what's happening on planet Earth
link |
00:46:46.020
one million years from now, Einstein tells me
link |
00:46:50.100
how to get one million years from now.
link |
00:46:52.500
Build a ship.
link |
00:46:53.340
I got to turn to guys who know how to build stuff.
link |
00:46:56.380
I can't do it like you.
link |
00:46:57.980
Build a ship that can go out into the universe
link |
00:47:00.020
near the speed of light, turn around and come back.
link |
00:47:02.780
Let's say it's a six month journey out
link |
00:47:04.420
and a six month journey back.
link |
00:47:05.900
And Einstein tells me how fast I need to travel,
link |
00:47:09.420
how close to the speed of light I need to go
link |
00:47:11.180
so that when I step out of my ship,
link |
00:47:13.740
it will now be one million years into the future
link |
00:47:16.980
on planet Earth.
link |
00:47:20.140
And this is not a controversial statement, right?
link |
00:47:23.300
This is not something where there's differences
link |
00:47:25.940
of opinion in the scientific community.
link |
00:47:28.340
Any scientist who knows anything
link |
00:47:30.900
about what Einstein taught us agrees with what I just said.
link |
00:47:35.100
It's commonplace, it's bread and butter physics.
link |
00:47:37.740
And so that kind of travel to the future
link |
00:47:40.660
is absolutely allowed by the laws of physics.
link |
00:47:44.140
There are engineering challenges,
link |
00:47:45.820
there are technological challenges.
link |
00:47:47.940
They're close to the speed of light part, yeah.
link |
00:47:49.460
Yeah, and there are even biological challenges, right?
link |
00:47:52.780
They're G forces that you're gonna experience.
link |
00:47:55.180
So there's all sorts of stuff embedded in this,
link |
00:47:57.740
but those I will call the details.
link |
00:48:01.020
And those details, notwithstanding,
link |
00:48:04.380
the universe allows this kind of travel to the future.
link |
00:48:07.820
And if I could pause real quick,
link |
00:48:09.660
you could also, at the macro level,
link |
00:48:12.620
with biology extend the human lifespan
link |
00:48:15.360
to do a kind of travel forward in time.
link |
00:48:19.300
If you expand how long we live,
link |
00:48:22.540
that's a way to, from a perspective of an observer,
link |
00:48:25.300
a conscious observer that is a human being,
link |
00:48:27.780
you're essentially traveling forward in time
link |
00:48:29.920
by allowing yourself to live long enough to see the thing.
link |
00:48:32.740
So that's in the space of biology.
link |
00:48:34.920
What about traveling back in time?
link |
00:48:37.160
Yeah, that is a natural next question,
link |
00:48:41.980
especially if you're going on one of these journeys.
link |
00:48:45.540
Is it a one way journey or can you come back?
link |
00:48:48.860
And the physics community doesn't speak
link |
00:48:52.480
with a unified voice on this as yet,
link |
00:48:55.220
but I would say that the dominant perspective
link |
00:48:57.860
is that you cannot get back.
link |
00:49:00.260
Now, having said that, there are proposals
link |
00:49:03.900
that serious people have written papers on
link |
00:49:07.300
regarding hypothetical ways
link |
00:49:09.080
in which you could travel to the past.
link |
00:49:10.900
And we've seen some of these.
link |
00:49:13.500
Again, Hollywood loves to take the most sexy ideas
link |
00:49:16.900
of physics and build narratives around them.
link |
00:49:20.040
This idea of a wormhole,
link |
00:49:21.980
like Jodie Foster in Contact went through a wormhole,
link |
00:49:25.480
Deep Space Nine Star,
link |
00:49:26.500
I'm sure there are many other examples
link |
00:49:27.860
for these ideas that I've probably never even seen.
link |
00:49:30.480
But with wormholes, there's at least a proposal
link |
00:49:34.460
of how you could take a wormhole tunnel through space time,
link |
00:49:38.200
manipulate the openings of the wormhole
link |
00:49:40.520
in such a way that the openings are no longer synchronous.
link |
00:49:44.100
They are out of sync relative to each other,
link |
00:49:46.300
which would mean one's ahead and one's behind,
link |
00:49:48.980
which means if you go through one direction,
link |
00:49:50.500
you travel to the future.
link |
00:49:51.620
If you go back, you travel to the past.
link |
00:49:54.380
Now, we don't know if there are wormholes in the world.
link |
00:49:57.740
But they're possible according to Einstein, correct?
link |
00:49:59.820
They are possible according to Einstein.
link |
00:50:01.760
But even Einstein was very quick to say,
link |
00:50:04.420
just because my math allows for something,
link |
00:50:07.260
doesn't mean it's real.
link |
00:50:08.100
I mean, he famously didn't even believe in black holes.
link |
00:50:10.860
Didn't believe in the Big Bang, right?
link |
00:50:12.900
And yet the black hole issue has really been settled now.
link |
00:50:17.180
We have radio telescopic photographs
link |
00:50:20.740
of the black hole in M87.
link |
00:50:22.820
It was in newspapers around the world
link |
00:50:25.240
just a couple of years ago.
link |
00:50:26.360
So it's just to say that just because it's in Einstein's math,
link |
00:50:31.180
it doesn't mean it's real.
link |
00:50:32.180
But yes, it is the case that wormholes
link |
00:50:35.000
are allowed by Einstein's equations.
link |
00:50:36.680
And in principle, you can imagine, you know,
link |
00:50:39.460
putting electric charges on the openings of the wormhole,
link |
00:50:42.300
allowing you to tow them around
link |
00:50:44.380
in a manner that could yield
link |
00:50:45.560
this temporal asymmetry between them.
link |
00:50:48.180
Maybe you tow one of the mouths to the edge of a black hole.
link |
00:50:51.780
In principle, you can do this,
link |
00:50:53.380
slowing down the passage of time near that black hole.
link |
00:50:56.540
And then when you bring it back,
link |
00:50:58.140
it will be well out of sync with the other opening
link |
00:51:02.060
and therefore could be a significant temporal gap
link |
00:51:05.420
between one and the other.
link |
00:51:07.100
But people who study this in more detail question,
link |
00:51:10.840
could you ever keep a wormhole open,
link |
00:51:13.060
assuming it does exist?
link |
00:51:14.760
Could you ever travel through a wormhole
link |
00:51:17.420
or would there be a requirement
link |
00:51:19.700
to some kind of exotic matter to prop it open
link |
00:51:22.940
that perhaps doesn't exist?
link |
00:51:24.420
So there are many, many issues that people have raised.
link |
00:51:28.060
And I would say that the general sentiment
link |
00:51:31.060
is that it's unlikely that this kind of scenario
link |
00:51:34.780
is going to survive our deeper understanding of physics
link |
00:51:37.980
when we finally have it.
link |
00:51:39.220
But that doesn't mean that the door is closed.
link |
00:51:41.340
So maybe there's a small possibility
link |
00:51:44.800
that this could one day be real.
link |
00:51:45.640
That's such an interesting way to put it.
link |
00:51:47.780
It will not, this kind of scenario
link |
00:51:49.820
will not survive deep understanding of physics.
link |
00:51:53.500
It's an interesting way to put it
link |
00:51:54.860
because it makes you wonder what kind of scenarios
link |
00:51:59.700
will be created by our deeper understanding of physics.
link |
00:52:04.080
Maybe, sorry to go crazy for a second,
link |
00:52:08.340
but if you have like the pan psychism idea
link |
00:52:11.220
that consciousness permeates all matter,
link |
00:52:14.200
maybe traveling in that, whatever laws of physics,
link |
00:52:17.980
the consciousness operates under something like that.
link |
00:52:20.140
In that view of the university,
link |
00:52:21.740
if we somehow are able to understand that part,
link |
00:52:24.140
maybe traveling is super easy.
link |
00:52:26.420
Yeah, it does not follow the constraints
link |
00:52:30.340
of the speed of light, something like this.
link |
00:52:32.700
Yeah, so look, I have a definite degree of sympathy
link |
00:52:38.380
with the possibility that consciousness might be more
link |
00:52:42.980
than what we described earlier
link |
00:52:45.500
as just the byproduct of mindless particles.
link |
00:52:48.180
You just made the rock happy.
link |
00:52:50.500
Exactly, so it isn't the approach
link |
00:52:54.340
that feels to me the most likely, but I see the logic.
link |
00:52:59.580
If you've got the puzzle,
link |
00:53:01.680
how to mindless particles build mind,
link |
00:53:04.280
one resolution might be the particles are not mindless.
link |
00:53:08.320
The particles have some kind of proto conscious quality.
link |
00:53:10.960
So there's something appealing
link |
00:53:13.020
about that straightforward solution to the puzzle.
link |
00:53:16.180
And if that's the case, if we do live in a pan psychist world
link |
00:53:20.140
where there is a degree of consciousness residing
link |
00:53:22.980
in everything in the world around us, then yes,
link |
00:53:25.220
I do think some interesting possibilities might emerge
link |
00:53:28.820
where maybe there's a way of communing
link |
00:53:31.720
with physical reality in a deeper way than we have so far.
link |
00:53:36.940
I mean, we as human beings,
link |
00:53:38.660
a vital part of our existence
link |
00:53:40.580
is human to human communication, contact.
link |
00:53:43.860
We live in social groups and that's what it's allowed us
link |
00:53:46.540
to get to the place where we've gotten.
link |
00:53:48.820
Imagine that we have long missed
link |
00:53:51.700
that there's other consciousness out there
link |
00:53:54.700
and some kind of relationship or communion
link |
00:53:57.520
with that larger conscious possibility
link |
00:53:59.980
would take us to a different place.
link |
00:54:01.380
Now, do I buy into this yet?
link |
00:54:03.860
I don't, I don't see any evidence for it,
link |
00:54:06.420
but do I have an open mind and allow for the possibility
link |
00:54:10.460
in the future?
link |
00:54:11.420
Yeah, I do.
link |
00:54:13.460
So if that's not the case
link |
00:54:15.380
and you have these simple particles
link |
00:54:18.420
that at the macro level emerges some interesting stuff
link |
00:54:21.880
like consciousness, another thing you write about
link |
00:54:24.900
in the Until the End of Time book
link |
00:54:27.280
is the thing that it seems to emerge at the macro level
link |
00:54:30.860
is the feeling like there's a free will,
link |
00:54:34.960
like we decide to do stuff.
link |
00:54:36.380
And you have a really interesting take here,
link |
00:54:39.100
which is, no, there's not a free will.
link |
00:54:43.500
I'm just gonna speak for you and then you can correct me.
link |
00:54:45.900
No, there's not a free will,
link |
00:54:48.080
but there is an experience of freedom.
link |
00:54:51.420
Yeah.
link |
00:54:54.260
Which I really love.
link |
00:54:56.100
So where does the experience,
link |
00:54:58.400
where does freedom come from
link |
00:54:59.780
if we don't have any kind of physics based free will?
link |
00:55:02.700
Yeah, and so the idea follows naturally
link |
00:55:06.820
from all that we've been talking about.
link |
00:55:08.480
Let's make the assumption that all there is
link |
00:55:11.860
in the physical universe is stuff governed by laws.
link |
00:55:15.380
We may not have those laws,
link |
00:55:16.520
may not know what the fundamental stuff is yet,
link |
00:55:19.500
but everything we know in science points in the direction
link |
00:55:23.700
that it's physical stuff governed by universal laws.
link |
00:55:27.860
And that being the case, or that being the assumption,
link |
00:55:31.380
then you come to a particular collection
link |
00:55:33.880
of those ingredients called a human being.
link |
00:55:35.900
And that human being has particles
link |
00:55:38.120
that are fully governed by physical law.
link |
00:55:41.620
And when you then recognize it,
link |
00:55:43.100
every thought that we have,
link |
00:55:44.380
every action that we undertake
link |
00:55:46.500
is just the motion of particles.
link |
00:55:49.400
When I'm thinking thoughts right now,
link |
00:55:50.900
of course, at this level of description,
link |
00:55:53.840
it is the motion of particles cascading
link |
00:55:56.320
down various neurons inside of my head and so on.
link |
00:55:59.820
And every single one of those motions,
link |
00:56:02.780
collectively and individually,
link |
00:56:05.340
is fully governed by these laws
link |
00:56:08.540
that we perhaps don't have yet,
link |
00:56:09.900
but we imagine one day we will.
link |
00:56:12.060
That leaves no opportunity for any kind of freedom
link |
00:56:15.780
to break free from the constraint of physical law.
link |
00:56:19.580
And that is the end of the story.
link |
00:56:21.660
So the traditional intuitive notion of free will,
link |
00:56:24.480
that we're the ultimate authors of our actions,
link |
00:56:26.880
that we were the buck stops,
link |
00:56:28.300
that there is no antecedent,
link |
00:56:30.260
that is the cause for our decided to go left or right,
link |
00:56:35.000
choose vanilla or chocolate, live or die,
link |
00:56:38.180
that intuitive sensation does not have a basis
link |
00:56:42.060
in our understanding of the physical world.
link |
00:56:43.780
So that's the end of the free will of the traditional sort.
link |
00:56:47.140
But then your question is,
link |
00:56:49.100
what about this other kind of freedom I talk about?
link |
00:56:52.020
And the other kind of freedom,
link |
00:56:53.900
if you focus on it intently,
link |
00:56:55.860
I think is actually the true version of freedom
link |
00:57:00.700
that we feel.
link |
00:57:02.180
And that freedom is this.
link |
00:57:04.300
You look at inanimate objects in the world,
link |
00:57:07.020
rocks, bottles of water, whatever,
link |
00:57:10.140
they have a very limited behavioral repertoire.
link |
00:57:13.340
Why?
link |
00:57:14.180
Their internal organization is too coarse
link |
00:57:17.100
for them to do very much, right?
link |
00:57:18.880
You try to have a conversation with a glass of water,
link |
00:57:22.040
you send sound waves, it doesn't do much.
link |
00:57:24.800
It may vibrate a little bit,
link |
00:57:26.140
but the repertoire of responses are incredibly limited.
link |
00:57:30.200
The difference between us and a rock or a bottle of water
link |
00:57:33.060
is that our inner organization,
link |
00:57:35.100
by virtue of eons of evolution by natural selection,
link |
00:57:38.420
is so refined, so spectacularly ordered,
link |
00:57:42.720
that we have a huge repertoire of behaviors
link |
00:57:46.460
that are finely attuned to stimuli from the external world.
link |
00:57:51.460
You ask me a question, that's a stimulus,
link |
00:57:53.320
and all of a sudden,
link |
00:57:54.460
these particle processes go into action,
link |
00:57:56.860
and this is the result, this answer that I'm giving you.
link |
00:58:00.080
So the freedom that we have is not from
link |
00:58:03.760
the control of physical law.
link |
00:58:05.580
The freedom that we have is from the constrained behavior
link |
00:58:08.260
that has long since governed inanimate objects.
link |
00:58:11.380
We are liberated from the limited behavioral repertoire
link |
00:58:14.700
of rocks and bottles of water
link |
00:58:17.220
to have this broad spectrum of responses.
link |
00:58:20.100
Do we pick them?
link |
00:58:20.940
We do not.
link |
00:58:21.840
Do we freely choose them?
link |
00:58:23.060
We do not, but yet we have them,
link |
00:58:26.060
and we can marvel at those behaviors,
link |
00:58:29.340
and that's the freedom that we have.
link |
00:58:31.460
The complexity and the breadth of that repertoire
link |
00:58:34.300
is where the freedom emerges.
link |
00:58:36.700
Is there something to be said about emergence?
link |
00:58:40.260
I don't know if you know,
link |
00:58:42.060
I've looked at much about objects
link |
00:58:43.700
that I seem to love way more than anyone else,
link |
00:58:47.280
which is Sally or Tom,
link |
00:58:49.420
like game of life type of stuff.
link |
00:58:51.700
From simple things emerges beautiful complexities,
link |
00:58:56.740
and so that's that repertoire.
link |
00:58:58.980
It's like, it seems if you have enough stuff,
link |
00:59:04.060
just beautiful complexity emerges
link |
00:59:06.300
that sure as heck to our human eyes looks
link |
00:59:09.620
like there's consciousness there, there's free will,
link |
00:59:12.060
there's little objects moving about and making decisions.
link |
00:59:15.640
I mean, all of that,
link |
00:59:16.820
you can say it's anthropomorphization,
link |
00:59:18.920
but it sure as heck feels
link |
00:59:21.820
like they're organisms making decisions.
link |
00:59:25.580
What is that emergence thing?
link |
00:59:27.660
Is that within the realm of physics to understand?
link |
00:59:31.220
Is it within the realm of poetry?
link |
00:59:36.100
What is that, like complex systems, emergence?
link |
00:59:39.620
Will that ever be understood by science?
link |
00:59:41.580
So here's the way that I think about it.
link |
00:59:43.980
So there are clearly qualities of the world
link |
00:59:47.820
that emerge on macroscopic scales,
link |
00:59:50.980
our sense of beauty, wonder, consciousness,
link |
00:59:53.740
all of these kinds of qualities.
link |
00:59:55.900
Do I feel that they ultimately are explainable
link |
01:00:00.180
from the laws of physics?
link |
01:00:01.180
I do.
link |
01:00:02.540
There is nothing that's not ultimately explainable
link |
01:00:06.300
with the laws of physics from this physicalist perspective,
link |
01:00:09.460
which is what I take.
link |
01:00:10.880
So you got the particles, you got the laws,
link |
01:00:13.980
and you have things that emerge
link |
01:00:16.180
from the choreographed motions of those particles.
link |
01:00:20.780
But is that the best language
link |
01:00:23.060
for talking about these emergent qualities?
link |
01:00:26.100
Usually not.
link |
01:00:27.540
If I was to take something even more mundane,
link |
01:00:30.940
like a baseball flying through the air,
link |
01:00:33.180
if I was to describe it in terms of the quarks
link |
01:00:35.680
and the electrons,
link |
01:00:36.820
I'd give you this mountain of data
link |
01:00:39.020
with 10 to the 28 particles
link |
01:00:42.340
and all of their coordinates and spaces
link |
01:00:45.300
a function of time.
link |
01:00:46.120
I hand you this mountain of data,
link |
01:00:46.960
you'd be like, I don't know what this is.
link |
01:00:49.180
And then if you really were clever and you're looking,
link |
01:00:51.180
oh, it's a baseball,
link |
01:00:53.240
just described in the least economical way possible.
link |
01:00:57.060
It is much more useful and insightful
link |
01:01:00.240
to talk about the baseball flying through the air.
link |
01:01:01.940
Similarly, there are things at the macroscopic level
link |
01:01:05.660
like human experience and human emotion and human action
link |
01:01:09.680
and the sensation of free will
link |
01:01:12.660
that we undeniably all have,
link |
01:01:14.780
even if it itself doesn't have a basis
link |
01:01:17.420
in our understanding of the physical world.
link |
01:01:19.460
It's useful to talk about things in this very human language.
link |
01:01:24.380
And so, yes, it's vital to talk about things
link |
01:01:26.700
in the poetic language of human experience,
link |
01:01:29.360
but do not lose sight of the fact, and some people do.
link |
01:01:31.820
They say, oh, it's just an emergent phenomenon.
link |
01:01:33.880
Don't lose sight of the fact that emergent phenomena
link |
01:01:36.100
are emerging from this deeper understanding
link |
01:01:39.840
that comes from the reductionist account of physical law.
link |
01:01:42.820
And there's a lot of insight to come from that,
link |
01:01:44.840
such as the freedom that you thought that you had,
link |
01:01:48.580
the freedom of will that you thought you had.
link |
01:01:50.340
It doesn't have a basis in that reductionist account,
link |
01:01:53.180
so it's not real.
link |
01:01:56.380
So speaking of the poetry of human experience,
link |
01:01:59.060
you mentioned the images of the black holes.
link |
01:02:01.140
How did it make you feel a few years ago
link |
01:02:03.140
when that first image came out?
link |
01:02:04.820
It's truly amazing.
link |
01:02:06.300
A sense of, well, I guess the feeling was both amazing
link |
01:02:11.860
and there was a little sense of,
link |
01:02:14.640
jealousy is not quite the right word,
link |
01:02:17.340
but a sense of longing.
link |
01:02:19.540
Yeah, I think that's a better word,
link |
01:02:20.920
because here's a subject that started with Einstein
link |
01:02:25.480
back in 1915, writes down the equations
link |
01:02:28.520
of the general theory of relativity,
link |
01:02:30.620
and then there are scores of individuals over the decades,
link |
01:02:34.820
starting with people like Karl Schwarzschild
link |
01:02:37.500
who analyze the equations,
link |
01:02:38.900
see the possibility of black holes.
link |
01:02:40.340
People develop these ideas.
link |
01:02:41.620
John Wheeler, all these greats of physics.
link |
01:02:44.140
It's still a hypothetical subject.
link |
01:02:46.460
It gets closer to reality through observations
link |
01:02:48.940
of the center of our galaxy,
link |
01:02:50.500
stars whipping around in a manner
link |
01:02:52.400
that could only really be explained
link |
01:02:54.620
by there being a black hole in the center of our galaxy,
link |
01:02:56.940
but it was still indirect.
link |
01:02:58.780
To actually have a direct image that you can look at,
link |
01:03:03.580
what a beautiful arc, narrative arc
link |
01:03:06.180
from the theoretical to the absolutely established.
link |
01:03:10.180
And that's what we hope will happen with other areas,
link |
01:03:13.620
for instance, string theory, right?
link |
01:03:15.140
I mean, wholly mathematical subject at the outset
link |
01:03:18.620
and still pretty much a wholly mathematical subject today.
link |
01:03:22.580
Yeah, do we long for that image
link |
01:03:25.900
where we can look at it and say, string, it's real.
link |
01:03:29.500
I mean, how thrilling, how thrilling to be part
link |
01:03:33.600
of that journey, to be part of that step
link |
01:03:36.420
that moves things from the abstract to the concrete.
link |
01:03:39.040
Yeah, so like the image of the DNA, the early images
link |
01:03:44.240
of the DNA, for example, but there is something special.
link |
01:03:47.520
So the problem with strings is they're tiny.
link |
01:03:50.940
So it's harder to take a picture in the following sense.
link |
01:03:54.900
When you think of a black hole, I mean, you have a swirl
link |
01:03:58.000
of, I guess, what is, I don't even know it's dust,
link |
01:04:00.960
whatever light.
link |
01:04:02.400
A careening onto the event horizon.
link |
01:04:04.560
And then there's darkness in the center.
link |
01:04:06.680
And you just imagine, so that picture in particular,
link |
01:04:10.120
I guess, is of a gigantic black hole.
link |
01:04:13.000
So you just, I mean, it's terrifying.
link |
01:04:16.160
Billions of times the mass of the sun.
link |
01:04:17.600
Yeah, so it's both exciting and terrifying.
link |
01:04:19.880
I mean, I don't know where you fall in the spectrum.
link |
01:04:22.040
I think it's exciting at first.
link |
01:04:24.920
Like the longer I think about it, every time I think
link |
01:04:27.040
about it, the more terrifying it becomes.
link |
01:04:29.280
So it always starts exciting and then it goes to terrifying.
link |
01:04:32.760
And both are feelings, very human feelings
link |
01:04:36.160
that I appreciate.
link |
01:04:38.360
It's like terrified awe.
link |
01:04:40.600
Somehow it's still beautiful.
link |
01:04:43.080
It's a good way of saying it.
link |
01:04:43.920
And I think I kind of share that reaction
link |
01:04:45.960
because there is a way in which when you work on this
link |
01:04:49.040
subject, like all the time, I teach it, I teach about
link |
01:04:52.880
black holes, write the equations on the blackboard.
link |
01:04:56.800
The ideas reside in a very cognitive,
link |
01:05:01.800
I don't know, mathematical portion of the brain,
link |
01:05:06.440
or at least for me.
link |
01:05:08.280
And it's only when you like sit down and it's quiet
link |
01:05:11.920
and you start to contemplate, wait, wait, wait, wait,
link |
01:05:13.680
this isn't just like a mathematical game.
link |
01:05:17.160
There are these monsters out there.
link |
01:05:19.400
Now I don't, not in a sense of I fear for my life,
link |
01:05:22.760
but it's a sense of how extraordinary is this universe.
link |
01:05:28.360
And so it is breathtaking.
link |
01:05:30.440
How powerful nature is.
link |
01:05:31.960
Yeah, how stupendously powerful nature is.
link |
01:05:37.280
And so there is a deep sense of humility
link |
01:05:42.120
that I think this instills if you really allow
link |
01:05:45.200
the ideas to sink in.
link |
01:05:48.260
Well, I have to ask about the most stupendously
link |
01:05:51.440
powerful thing to have ever happened in our universe,
link |
01:05:54.360
which is the Big Bang.
link |
01:05:56.520
What's up with the Big Bang?
link |
01:05:57.880
So we can, I mean, with gravitational waves,
link |
01:06:01.360
the hope is you have more and more accurate measurements
link |
01:06:05.040
of the gravitational waves.
link |
01:06:06.040
You can crawl back further and further back in time
link |
01:06:08.440
towards the Big Bang.
link |
01:06:10.680
Do you have a hope that we'll be able to understand
link |
01:06:13.440
the early spark that created our universe?
link |
01:06:18.080
Yeah, that and the deep interior of a black hole
link |
01:06:23.280
I think are the biggest mysteries that we hope
link |
01:06:26.960
the melding of quantum mechanics and gravity will reveal,
link |
01:06:30.720
will illuminate.
link |
01:06:32.440
And what question could be more captivating
link |
01:06:36.960
than why is there something rather than nothing, right?
link |
01:06:39.920
Why is there a universe at all?
link |
01:06:43.240
And will the theories that we're developing
link |
01:06:46.360
take us to an answer to that?
link |
01:06:48.480
I don't know.
link |
01:06:49.720
Even if we truly knew what the Big Bang is,
link |
01:06:51.680
and that's a big question in its own right,
link |
01:06:53.480
one would still be left with the question,
link |
01:06:55.120
well, okay, so you've explained the process
link |
01:06:59.080
by which a tiny nugget of a universe,
link |
01:07:03.560
a tiny nugget of space time can undergo some kind of growth
link |
01:07:08.160
to yield the world around us.
link |
01:07:10.080
But presumably in that explanation,
link |
01:07:12.920
you're gonna involve mathematics and some ingredients
link |
01:07:16.400
like quantum fields or matter or energy or something.
link |
01:07:21.880
Where did that stuff come from?
link |
01:07:24.680
Can we get to that level of explanation?
link |
01:07:26.880
I don't know, but it is remarkable
link |
01:07:29.120
that if you ask what happened a millionth of a second
link |
01:07:34.280
after the Big Bang,
link |
01:07:36.040
it's not really that controversial any longer, right?
link |
01:07:40.240
Even though there's a lot of argument in the field
link |
01:07:42.760
and it's very heated right now I should say
link |
01:07:45.400
regarding what is the right theory of the Big Bang?
link |
01:07:49.920
What is the right theory of early universe cosmology
link |
01:07:53.440
where I mean early, much earlier
link |
01:07:55.000
than a millionth of a second,
link |
01:07:56.040
a lot of dissent, a lot of heated arguments about that.
link |
01:08:01.680
No pun intended.
link |
01:08:02.680
Yeah, right, exactly.
link |
01:08:04.280
But you go like a millionth of a second after that
link |
01:08:08.160
and we're on pretty firm ground.
link |
01:08:10.080
Isn't that amazing, right?
link |
01:08:12.160
To understand what happened from that point forward.
link |
01:08:15.400
But to go back is controversial.
link |
01:08:18.240
So there is this theory called inflationary cosmology,
link |
01:08:21.600
which I would say has been the dominant paradigm
link |
01:08:24.560
since early 1980s.
link |
01:08:27.120
So what does that mean?
link |
01:08:27.960
Roughly 40 years now,
link |
01:08:28.920
it's been the dominant cosmological paradigm.
link |
01:08:31.400
And it makes use of a curious feature
link |
01:08:33.760
of Einstein's general theory of relativity,
link |
01:08:36.000
his theory of gravity,
link |
01:08:37.240
where Einstein shows us mathematically
link |
01:08:39.800
that gravity can not only be attractive,
link |
01:08:41.840
the kind of gravity that we're used to,
link |
01:08:43.280
things pulled together, but it can also be repulsive.
link |
01:08:47.400
And that fact is then leveraged by people like Alan Guth
link |
01:08:53.200
and Andre Linde, and at the time Paul Steinhardt
link |
01:08:56.240
and Andreas Albrecht and others to say,
link |
01:08:58.760
okay, if we had a little nugget in the earlier universe,
link |
01:09:01.400
which was filled with the stuff
link |
01:09:03.520
that yields this repulsive gravity,
link |
01:09:05.520
well, that would have blown everything apart.
link |
01:09:07.360
It would cause everything to swell.
link |
01:09:09.160
Beautiful explanation for what the bang
link |
01:09:11.400
in the big bang was.
link |
01:09:13.040
And then people mathematically analyze the consequences
link |
01:09:16.760
of this idea and they make predictions
link |
01:09:19.040
for tiny temperature differences across the night sky
link |
01:09:22.680
that in principle could be measured.
link |
01:09:24.840
You send up balloons, you send up satellites
link |
01:09:27.120
with very refined thermometers,
link |
01:09:29.920
and they measured the temperature of the night sky
link |
01:09:33.000
and the statistical distribution
link |
01:09:34.800
of the temperature differences agrees
link |
01:09:36.440
with the mathematical predictions.
link |
01:09:39.920
I mean, you just sort of have to stand in awe
link |
01:09:43.200
of this insight.
link |
01:09:44.560
So you think, aha, the theory has been established,
link |
01:09:48.320
but scientists are an incredibly skeptical bunch.
link |
01:09:54.200
And some scientists, including one of the people
link |
01:09:56.640
who helped develop the theory at the outset,
link |
01:09:58.360
Paul Steinhardt comes along and says,
link |
01:10:00.960
well, yeah, this theory has done pretty well so far,
link |
01:10:04.120
but there are aspects of this theory
link |
01:10:06.480
that are making me lose confidence.
link |
01:10:08.160
For instance, this theory seems to suggest
link |
01:10:10.880
that there might be other universes.
link |
01:10:13.360
Like, how do you make sense of a theory
link |
01:10:15.280
that suggests there are other universes?
link |
01:10:16.880
Or there are others who come along and say,
link |
01:10:18.920
this theory seems to talk about length scales
link |
01:10:23.240
that are minuscule even by the so called Planck length,
link |
01:10:26.680
the sort of shortest length that we can imagine
link |
01:10:29.360
making sense of in a theory of quantum gravity.
link |
01:10:31.840
How do you make sense of that?
link |
01:10:33.440
And so on and so forth, they develop a list of things
link |
01:10:36.720
that they consider to be chinks
link |
01:10:38.560
in the inflationary cosmological theory's armor.
link |
01:10:42.600
And they develop other ideas,
link |
01:10:44.120
which they claim yield the same predictions
link |
01:10:47.560
as inflationary cosmology
link |
01:10:48.640
for those temperature differences across space,
link |
01:10:50.440
but don't suffer from these problems.
link |
01:10:52.840
And then the inflationary cosmology folks say,
link |
01:10:55.160
no, no, no, hang on.
link |
01:10:56.720
Your theory suffers from different problems.
link |
01:10:59.920
And so the arguments goes, it's a healthy debate.
link |
01:11:02.600
Talk about real debates in science.
link |
01:11:05.120
So when you ask what's up with the Big Bang,
link |
01:11:07.800
I don't know right now.
link |
01:11:09.920
If you would have asked me five years ago,
link |
01:11:12.760
maybe even less than that, three or four years ago,
link |
01:11:15.160
I've said, look, inflationary cosmology has some issues,
link |
01:11:19.080
but the package of explanations it provides is so potent
link |
01:11:23.560
and the issues that beset it are seemingly solvable to me
link |
01:11:29.080
that I would imagine it's going to in the end, win out.
link |
01:11:32.920
I would still say that today,
link |
01:11:34.200
but I wouldn't say it as loudly.
link |
01:11:36.200
I wouldn't say it as confidently.
link |
01:11:38.800
I think it's worth thinking about alternate ideas
link |
01:11:42.120
and it could be the case that the paradigm
link |
01:11:44.280
at some point shifts.
link |
01:11:46.840
Does dark matter and dark energy fit into the shifting
link |
01:11:50.480
of the explanations for those?
link |
01:11:52.520
Yeah, certainly.
link |
01:11:53.360
So dark energy has in the inflationary theory
link |
01:11:58.440
is kind of a big mystery.
link |
01:12:00.200
So dark energy is the observational realization
link |
01:12:05.600
in the last 20 years
link |
01:12:06.800
that not only is the universe expanding,
link |
01:12:09.440
it's expanding ever more quickly.
link |
01:12:11.520
Something is still pushing things outward.
link |
01:12:15.080
And the explanation is that there's like a residual version
link |
01:12:18.320
of the repulsive gravity from the early universe,
link |
01:12:20.560
but it's such a strange number.
link |
01:12:23.000
When you write that amount of dark energy
link |
01:12:25.600
using the relevant units in a theory of quantum gravity,
link |
01:12:29.080
it's a decimal point followed by like 120 zeros
link |
01:12:33.040
and then a one.
link |
01:12:34.640
We're not used to those kinds of numbers in physics.
link |
01:12:38.280
We're used to a half, one, pi, e squared to two.
link |
01:12:44.960
Those are the kinds of fundamental numbers
link |
01:12:46.720
that emerge in our explanations of the world.
link |
01:12:49.840
And we look at this bizarre number,
link |
01:12:51.920
decimal point, all these zeros and a one,
link |
01:12:53.720
we say something's wrong there.
link |
01:12:56.200
Like where would that number have come from?
link |
01:12:59.600
And now there are people who suggest resolution to it.
link |
01:13:01.800
So it's not like we're totally in the dark on it,
link |
01:13:03.600
but those people like Paul Steinhard
link |
01:13:06.680
who have alternate cosmological theories,
link |
01:13:09.120
cyclic cosmologies as they call it,
link |
01:13:11.160
claim that they have a more natural explanation
link |
01:13:14.480
of the dark energy,
link |
01:13:15.880
that it naturally feeds into a cyclical process
link |
01:13:19.360
that is their cosmological paradigm.
link |
01:13:22.760
So yeah, if the cosmology should change,
link |
01:13:26.240
it's conceivable our view of dark energy
link |
01:13:29.200
may change from deeply mysterious
link |
01:13:31.480
to deeply integrated into a different paradigm.
link |
01:13:34.240
That is possible.
link |
01:13:35.560
I think it's Roger Penrose that think
link |
01:13:37.440
that information can bleed through
link |
01:13:39.480
from before the Big Bang to the after the Big Bang.
link |
01:13:42.440
Is the Big Bang like a full erasure of the hard drive
link |
01:13:46.880
or is there some information that could bleed through?
link |
01:13:48.920
Yeah, I mean, so Roger is among the most creative thinkers
link |
01:13:54.040
of the last 100 years,
link |
01:13:55.760
rightly won the Nobel Prize for his insights
link |
01:13:59.280
into singularities in space time
link |
01:14:02.000
that we know to afflict our mathematical solutions
link |
01:14:06.480
of black holes in the Big Bang and so forth.
link |
01:14:08.120
And he has an enormously fertile imagination.
link |
01:14:13.400
And I mean that in the most positive sense.
link |
01:14:16.320
And so he has put forward this idea,
link |
01:14:19.640
this conformal cyclic cosmology,
link |
01:14:21.880
I think is the official title,
link |
01:14:23.760
although I could be getting that wrong.
link |
01:14:26.280
I can't say that I've studied it.
link |
01:14:27.920
I have seen lectures on it.
link |
01:14:30.280
I don't find it convincing as yet.
link |
01:14:33.240
It feels like it's being built to find a solution
link |
01:14:38.720
as opposed to sort of more naturally emerging.
link |
01:14:42.200
Maybe Roger would say otherwise.
link |
01:14:43.920
And I don't mean to in any way
link |
01:14:47.040
cast aspersions on the work.
link |
01:14:48.440
It's vital and interesting and people are thinking about it.
link |
01:14:51.400
I don't consider it as close a competitor
link |
01:14:55.400
to say the inflationary theory as for instance,
link |
01:14:58.080
the stuff that Paul Steinhardt has put forward.
link |
01:15:00.840
But again, you've got to keep an open mind
link |
01:15:04.120
in this business when there's so much
link |
01:15:06.320
that we don't yet understand.
link |
01:15:07.680
I mean, it is wild to think
link |
01:15:08.800
that information could survive something like that.
link |
01:15:10.880
Just like it is wild to imagine
link |
01:15:13.320
that information could escape a black hole, for example.
link |
01:15:16.560
It just seems like by construction,
link |
01:15:20.160
these things are supposed to not bleed out anything.
link |
01:15:24.160
But one of the challenges in all of these theories
link |
01:15:25.840
is when we talk about a singularity,
link |
01:15:27.640
has this real sexy term, the singularity.
link |
01:15:30.200
But a singularity is in more ordinary language,
link |
01:15:35.560
a physical system where the mathematics breaks down.
link |
01:15:39.760
It's nonsensical.
link |
01:15:41.080
It's like taking one divided by zero.
link |
01:15:42.800
You put that into a calculator and it says E error, right?
link |
01:15:45.640
It does not make sense, doesn't compute.
link |
01:15:48.240
And so it's very hard to make definitive statements
link |
01:15:53.240
about things like the Big Bang or about black holes
link |
01:15:56.160
until we cure the mathematical singularities.
link |
01:15:59.840
And there are some who claim that in certain regimes,
link |
01:16:03.160
the singularities have been cured.
link |
01:16:05.800
I don't by any means think that there's consensus
link |
01:16:08.560
on these ideas.
link |
01:16:09.560
So when one talks about information sort of bleeding
link |
01:16:12.560
through the Big Bang, you've really got to make sure
link |
01:16:15.000
that the equations have no singularity.
link |
01:16:16.840
You talk about cyclic cosmology,
link |
01:16:18.240
you've got to make sure that the equations
link |
01:16:20.040
don't have any singularities as you go from, say,
link |
01:16:22.080
one cycle to the next.
link |
01:16:23.680
Now, some of the proponents of these theories claim
link |
01:16:25.640
that they have resolved these issues.
link |
01:16:27.520
I don't think that there's a general sense
link |
01:16:30.160
that that is the case as yet, but it could be that,
link |
01:16:32.920
look, life is so short that I haven't had the time
link |
01:16:36.360
to deeply delve into all the mathematical intricacies
link |
01:16:39.000
of all the ideas that have been put forward.
link |
01:16:40.760
If I did that, I'd never do anything else.
link |
01:16:42.720
But that's what the issue is.
link |
01:16:44.200
And of course, it's just math.
link |
01:16:45.880
There may be holes.
link |
01:16:47.240
There may be gaps in our understanding
link |
01:16:52.920
in the way we're modeling physical reality.
link |
01:16:55.160
Well, that's the point.
link |
01:16:56.000
In fact, when you said, I was about to jump in
link |
01:16:57.480
and say modeling, but you got there first,
link |
01:16:59.360
and it's exactly the right point.
link |
01:17:02.000
We're talking about the universe here, right?
link |
01:17:04.640
And how do you talk about the universe
link |
01:17:06.960
with a straight face, mathematically?
link |
01:17:09.000
And the way you do it is you simplify,
link |
01:17:12.080
you throw away those characteristics of the universe
link |
01:17:14.680
that you don't think are vital to a full understanding.
link |
01:17:18.520
And so we're gonna get to a point people are starting to
link |
01:17:21.560
where we've got to go beyond those simplifications.
link |
01:17:24.800
And so cosmology has for a long time modeled the universe
link |
01:17:29.360
in the most simplest terms, homogeneous, isotropic.
link |
01:17:33.320
It has just a few parameters that describe it,
link |
01:17:35.920
the average density of mass and energy and so forth.
link |
01:17:38.560
We have to go beyond those simplifications,
link |
01:17:40.360
and that will require putting these things on computers.
link |
01:17:43.400
We're not gonna be able to do calculations there.
link |
01:17:45.200
So much as astrophysics has gone beyond many simplifications
link |
01:17:49.640
to now give really detailed simulations of star systems
link |
01:17:53.280
and galaxies and so forth,
link |
01:17:54.880
we're gonna have to do that with cosmology,
link |
01:17:56.880
and people are starting to do that today.
link |
01:17:59.120
Yeah, I've seen some interesting work on simulation,
link |
01:18:02.880
most simulation cosmology, by the way, is just awesome.
link |
01:18:05.760
But just like simulation of the early formation
link |
01:18:08.720
of our solar system to understand how the like the Oort cloud
link |
01:18:12.960
and just, I don't know, the whole of it,
link |
01:18:16.520
how Earth came to be, like how Jupiter just protects us.
link |
01:18:22.600
And then there's like weird like moons and volcanoes
link |
01:18:28.160
and like modeling all of that,
link |
01:18:30.600
the formation of all of that is fascinating.
link |
01:18:34.440
Because that naturally is the question
link |
01:18:37.120
of how does life emerge on these kinds of rocks?
link |
01:18:41.200
How does a rock become a rabbit?
link |
01:18:44.520
But speaking of models,
link |
01:18:47.440
there's an equation called the Drake equation.
link |
01:18:50.360
We were talking about life.
link |
01:18:52.720
Have to ask, at the highest level first,
link |
01:18:56.360
when you look out there,
link |
01:18:58.040
how many alien civilizations do you think are out there?
link |
01:19:01.240
Well, zero, one, or many?
link |
01:19:04.640
So if you say civilization,
link |
01:19:08.200
I would bring my number way down.
link |
01:19:12.480
It could be zero.
link |
01:19:15.000
If you talk about life, I think it could be many.
link |
01:19:20.520
As we were saying before,
link |
01:19:21.800
I think the move from life to consciousness,
link |
01:19:25.840
the kinds of beings that would build
link |
01:19:27.480
what we would recognize as a civilization,
link |
01:19:30.720
that may be extraordinarily rare.
link |
01:19:34.240
I hope it's not.
link |
01:19:36.080
You know, as a kid, I loved Star Trek.
link |
01:19:38.080
I just loved the idea that we would be part
link |
01:19:40.560
of some universal community where,
link |
01:19:43.680
look, experience on planet Earth
link |
01:19:46.000
suggests it doesn't always go so well
link |
01:19:48.120
when groups who are separated try to come together
link |
01:19:50.880
and live in some larger collective.
link |
01:19:53.760
But again, as an optimist,
link |
01:19:55.920
how amazing would it be to converse
link |
01:19:57.920
with an alien civilization and learn
link |
01:19:59.800
what they've figured out about physics and cosmology
link |
01:20:03.600
and compare notes and learn from each other
link |
01:20:06.960
in some wonderful way?
link |
01:20:09.280
I love that idea.
link |
01:20:10.480
But if you ask me the likelihood of it,
link |
01:20:13.800
I would err on saying it may be so improbable
link |
01:20:18.560
that the conditions conspire to allow life
link |
01:20:21.680
to move to this place of consciousness
link |
01:20:24.680
that it might be rare.
link |
01:20:27.120
It might be oversimplifying things,
link |
01:20:28.640
but just observing the power of the evolutionary process,
link |
01:20:32.560
I tend to believe,
link |
01:20:34.360
and like you read different theories of how we went,
link |
01:20:40.640
how Homo sapiens evolved,
link |
01:20:43.200
it seems like the evolutionary process
link |
01:20:45.560
naturally leads to Homo sapiens
link |
01:20:50.040
or creatures like that or much better than that.
link |
01:20:53.200
So to me, there's several scary scenarios.
link |
01:20:57.320
So, okay, the positive scenario
link |
01:21:00.760
is life itself is really difficult.
link |
01:21:03.240
So that origin of life is difficult.
link |
01:21:05.840
That's exciting for many reasons
link |
01:21:08.040
because we might be able to prove that wrong easily
link |
01:21:12.520
in the near term by finding life elsewhere.
link |
01:21:14.760
Sure.
link |
01:21:15.920
The scary thing to me is if life is easy
link |
01:21:21.320
and there's plenty of conscious intelligent civilizations
link |
01:21:26.120
out there and we have not obviously made contact,
link |
01:21:30.600
which means with intelligence and consciousness
link |
01:21:33.320
comes responsibility and ultimately destruction.
link |
01:21:39.920
So with power comes great responsibility
link |
01:21:42.840
and then we end up destroying ourselves.
link |
01:21:44.760
That's the scariest.
link |
01:21:48.120
The positive, I guess, version is that
link |
01:21:51.280
maybe we're being watched,
link |
01:21:54.280
sort of like there's a transition
link |
01:21:57.200
to where you don't wanna ruin the primitive villages
link |
01:22:00.720
out there and so there's a protective layer around us.
link |
01:22:04.600
They're watching.
link |
01:22:06.600
So where do you in these possible explanations
link |
01:22:09.520
to the Fermi paradox,
link |
01:22:10.520
why haven't we contacted aliens?
link |
01:22:12.240
Do you land on?
link |
01:22:13.600
Well, I think the most straightforward explanation
link |
01:22:17.720
is that there aren't any.
link |
01:22:20.320
Now, there are many other explanations too.
link |
01:22:23.160
So you can't be dogmatic about things
link |
01:22:25.560
that are just sort of gut feel,
link |
01:22:27.640
but one of my favorite Twilight Zone episodes,
link |
01:22:31.800
I don't know if you ever saw this one
link |
01:22:33.280
where this alien civilization finally comes
link |
01:22:36.280
to planet Earth and gives us this book
link |
01:22:39.280
that they really want us to have and to hold
link |
01:22:42.680
and it's in this foreign language,
link |
01:22:44.760
you don't understand it.
link |
01:22:45.600
The cryptographers, they desperately try to decipher it
link |
01:22:49.120
as humans are gonna visit this other alien planet
link |
01:22:52.480
and they're all sending back postcards,
link |
01:22:53.720
how wonderful it is and so forth
link |
01:22:55.240
and they finally decipher the title.
link |
01:22:58.560
It's To Serve Man and everyone's so thrilled,
link |
01:23:01.480
oh, they're here to serve us, it all makes sense
link |
01:23:03.680
and then just as one of the final cryptographers
link |
01:23:06.240
is going on to the alien ship,
link |
01:23:08.160
his helper runs and says,
link |
01:23:10.880
I've deciphered the rest of the book.
link |
01:23:12.960
To Serve Man, it's a cookbook.
link |
01:23:14.920
So yeah, is that a possibility?
link |
01:23:20.920
Sure.
link |
01:23:21.760
And so could they be watching us
link |
01:23:23.960
and just sort of waiting for us to get
link |
01:23:26.040
to a mature enough level?
link |
01:23:29.680
I don't know, it strikes me.
link |
01:23:31.120
Well, I think it'd be better to have this conversation
link |
01:23:33.440
after the James Webb Telescope.
link |
01:23:35.040
I mean, I do think that if we look
link |
01:23:38.440
at the atmospheres of many planets,
link |
01:23:41.360
I mean, there's now an estimate now
link |
01:23:42.520
that there's on order of one planet per star on average.
link |
01:23:48.000
So we've long known that the galaxy,
link |
01:23:50.760
hundreds of billions of stars,
link |
01:23:52.800
numbers of galaxies, hundreds of billions of galaxies.
link |
01:23:54.800
So we're talking about hundreds of billions
link |
01:23:56.680
of hundreds of billions of planets, oh my.
link |
01:23:59.040
And if we start to survey some of these planets
link |
01:24:02.320
and one after the other after the other,
link |
01:24:03.840
we just sort of find no evidence
link |
01:24:06.360
for any of the biological markers.
link |
01:24:10.400
It could be, of course,
link |
01:24:11.320
maybe life takes a radically different form.
link |
01:24:13.840
It'd be hard to know that.
link |
01:24:15.400
But I think that would at least give us some insight
link |
01:24:18.280
on the life question.
link |
01:24:19.360
But I just don't see how we get insight
link |
01:24:21.960
on the civilization or consciousness question
link |
01:24:25.120
without the direct connection.
link |
01:24:27.560
And it strikes me that if consciousness is ubiquitous,
link |
01:24:32.560
let's say life is, I'm willing to grant that.
link |
01:24:35.080
If consciousness is also ubiquitous,
link |
01:24:37.280
then I don't understand why they haven't been here
link |
01:24:41.680
or why there hasn't been separation
link |
01:24:43.520
because presumably they should be much further ahead of us.
link |
01:24:47.920
How unlike would it be that we're like,
link |
01:24:50.200
of all consciousness in the universe,
link |
01:24:52.120
we're the most advanced.
link |
01:24:53.520
That'd be such a special place for human beings
link |
01:24:56.960
that it's hard for me to grant that as a likely possibility.
link |
01:25:00.160
Rather, I think we're kind of run of the mill.
link |
01:25:02.680
And there are many who are far more advanced than us.
link |
01:25:06.000
And I don't think that they would expend the energy
link |
01:25:09.080
to hide themselves.
link |
01:25:11.360
I don't think they care enough.
link |
01:25:12.800
And so see, that's actually what I believe
link |
01:25:15.880
that there's a very large number of civilizations
link |
01:25:19.160
that are far more advanced than us.
link |
01:25:21.440
But my sense is that humans are exceptionally limited
link |
01:25:25.200
both in our direct sensory capabilities and our physics,
link |
01:25:29.280
our tools of sensing that just like with the string theory
link |
01:25:33.240
and the multiple dimensions, we're just not like,
link |
01:25:36.520
it's like, I honestly believe there could be stuff
link |
01:25:39.040
in front of our nose that we're just not seeing
link |
01:25:43.720
because we're too dumb, too much hubris
link |
01:25:48.720
and I mean, there's a bunch of stuff
link |
01:25:50.920
and too ignorant to the fabric of reality,
link |
01:25:54.920
all of those things.
link |
01:25:56.280
We're young in terms of intelligence.
link |
01:25:59.840
But I guess what I'd say is like, I'm on board
link |
01:26:01.880
with all of that as a real possibility,
link |
01:26:04.120
but then it does strike me that we are sufficiently
link |
01:26:09.440
able to observe the unit.
link |
01:26:11.760
Look, we can look back to a fraction of the duration
link |
01:26:16.760
from here to the, just a fraction is left
link |
01:26:20.040
that we are unable to see.
link |
01:26:22.680
So however young we are, we have been able
link |
01:26:27.320
to sort of pierce the universe and it just strikes me
link |
01:26:29.960
that there would be some signature,
link |
01:26:33.280
but maybe that's coming.
link |
01:26:35.240
But look, having said that I do, look,
link |
01:26:38.080
I certainly note the fact that it's rare
link |
01:26:41.560
that I stoop down while walking in Manhattan
link |
01:26:46.120
and sort of dig up some ants in the bushes
link |
01:26:48.920
on the side of the street and talk to the ants, right?
link |
01:26:51.520
Because it's just not interesting to me.
link |
01:26:52.960
So if we're like the ants on the cosmological landscape,
link |
01:26:56.080
then yeah, I can imagine that the super advanced aliens
link |
01:26:58.760
would be like, like whoever, you know,
link |
01:27:01.960
but I feel like we're sufficiently advanced
link |
01:27:04.320
that there should be some signal signature of that,
link |
01:27:07.200
but maybe it's coming.
link |
01:27:08.320
I think the deeper fundamental problem between us
link |
01:27:10.680
and the ants is that we don't have a common language.
link |
01:27:12.760
It's not the interest.
link |
01:27:14.600
It's that we don't even have a common language.
link |
01:27:17.280
And so the alien civilizations don't even know how to,
link |
01:27:21.840
like we humans have convinced ourselves we're special
link |
01:27:24.720
because we developed the language.
link |
01:27:25.880
And you talked about the importance of language
link |
01:27:28.760
to the intelligence, but it makes you wonder
link |
01:27:31.640
like how very niche is that like club that we've,
link |
01:27:36.360
like tribe we've created of language
link |
01:27:38.440
and linguistic type of systems that are very specific
link |
01:27:41.480
to our particular kinds of brains
link |
01:27:42.880
and we share ideas together are all super excited
link |
01:27:45.240
that we can understand the universe
link |
01:27:46.520
because we came up with some notation and math.
link |
01:27:49.320
I wonder if there's some totally other kinds of language
link |
01:27:52.440
that communicates on a different timescale
link |
01:27:54.440
with different, very different mechanisms
link |
01:27:56.840
in the space of information that just is not,
link |
01:28:00.080
it's everything, everything is lost in translation.
link |
01:28:03.200
Yeah, and it could well be as a look.
link |
01:28:05.120
I mean, I think part of the reason I go
link |
01:28:07.800
toward the possibility of the soul intelligence
link |
01:28:12.840
is there's a certain kind of romantic appeal
link |
01:28:16.400
to looking out in the cosmos and it's just quiet
link |
01:28:20.800
and it's just eternal silence.
link |
01:28:22.520
There's something that appeals to me
link |
01:28:25.320
at an emotional level that way.
link |
01:28:27.840
But yeah, I mean, nobody knows.
link |
01:28:31.680
And it's certainly conceivable
link |
01:28:35.480
that there's just a radical mismatch
link |
01:28:38.640
between the kinds of things
link |
01:28:40.040
that we are able to observe and sensitive to
link |
01:28:42.840
versus the kinds of structures that permeate the universe
link |
01:28:47.160
in a manner that simply we're unable to detect.
link |
01:28:50.400
Well, if we are alone, that is exciting.
link |
01:28:54.000
And one of the ways it's exciting
link |
01:28:56.560
is that it's up to us to become,
link |
01:29:00.280
to expand out into the universe,
link |
01:29:02.760
to permeate consciousness out into the universe.
link |
01:29:07.760
So that's where space exploration comes in.
link |
01:29:09.960
Let me ask you as somebody who's a screen theorist,
link |
01:29:12.440
a physicist, do you think space exploration,
link |
01:29:17.120
a colonizing space is a physics or an engineering problem?
link |
01:29:21.440
What would you say?
link |
01:29:22.280
Yeah, I think it's fundamentally an engineering problem
link |
01:29:25.440
if we're not trying to do things like build wormholes
link |
01:29:30.440
the way they did, say an interstellar
link |
01:29:32.960
to get to a different place
link |
01:29:34.160
or trying to travel near the speed of light
link |
01:29:36.880
so that we would actually be able
link |
01:29:38.360
to traverse interstellar distances.
link |
01:29:40.120
I mean, without that,
link |
01:29:41.800
our colonization will happen in a very, very slow rate.
link |
01:29:47.920
But one of the beauties of relativity
link |
01:29:50.400
is if you do travel near the speed of light,
link |
01:29:51.920
you can actually go arbitrarily far in a human lifetime.
link |
01:29:56.000
People say, how's that possible?
link |
01:29:57.120
You can't go billions of light years.
link |
01:29:59.120
Billions of light years, well, you can actually,
link |
01:30:01.720
because as you can do the speed of light,
link |
01:30:03.440
the way in which space and time change
link |
01:30:06.080
allows you to go in principle arbitrarily far.
link |
01:30:08.640
That's very exciting.
link |
01:30:09.960
But if we put that physics side of the issue
link |
01:30:13.640
and the manipulation of space and time to the side,
link |
01:30:15.960
yeah, I think it's a deep engineering problem.
link |
01:30:18.360
How do you terraform other planets?
link |
01:30:21.680
I mean, how do you go beyond our local neighborhood,
link |
01:30:26.680
say without using the ideas of relativity?
link |
01:30:30.320
So I think it's all quite exciting.
link |
01:30:32.080
And I think the idea is using solar sails
link |
01:30:34.920
that people have developed
link |
01:30:36.680
and trying to take that first step to Mars,
link |
01:30:40.720
I think that's a vital and valuable step to take.
link |
01:30:43.960
But yeah, I think these are
link |
01:30:44.800
fundamentally engineering challenges.
link |
01:30:46.320
Or extending the human lifespan through biology research
link |
01:30:49.440
or maybe reducing what it means to be a human being
link |
01:30:54.440
into information and uploading certain parts of it.
link |
01:30:57.720
Maybe not all of the full resolution of a human life,
link |
01:31:00.920
but maybe the essential things like the DNA
link |
01:31:03.920
and be able to reconstruct that human being.
link |
01:31:07.920
But I have to ask about Mars.
link |
01:31:12.600
Do you find the dream of humans stepping on Mars,
link |
01:31:17.520
stepping foot first, but also colonizing Mars,
link |
01:31:20.820
one that's worth us fighting for?
link |
01:31:25.020
Yeah, usually so.
link |
01:31:25.980
I mean, I think what we have long been
link |
01:31:28.500
not always in the best way is a species of explorers
link |
01:31:33.900
in the literal sense of traveling
link |
01:31:37.020
from one part of the world to another,
link |
01:31:39.540
or in the more metaphorical sense
link |
01:31:41.340
of trying to travel through our minds to the quantum realm
link |
01:31:45.100
or back to the Big Bang or to the center of black holes.
link |
01:31:47.740
So I think that's fundamentally part of the human spirit.
link |
01:31:51.460
So I do think that's a vital part of our heritage
link |
01:31:56.860
brought forward into its next incarnation.
link |
01:32:01.020
That's who we are.
link |
01:32:03.740
Do you think there'll be a day in the future
link |
01:32:06.860
where a human being is born on Mars
link |
01:32:11.300
and has to learn about his or her human origins on Earth?
link |
01:32:16.300
Like, they'll have to read in a book.
link |
01:32:18.860
Yeah, I don't think it'll be a book at that stage.
link |
01:32:20.420
It'll probably just be uploaded into the head or something
link |
01:32:22.900
or imprinted into the DNA,
link |
01:32:25.220
and then they just sort of sense it.
link |
01:32:26.900
But yeah, I think there's, well, look,
link |
01:32:29.540
the issue you raised before is the vital one.
link |
01:32:32.340
Is it the case that any sufficiently advanced civilization
link |
01:32:36.020
destroys itself?
link |
01:32:37.420
Is that sort of a commonplace quality?
link |
01:32:39.820
I mean, that's the other potential answer
link |
01:32:41.460
to the Fermi paradox.
link |
01:32:43.220
Why aren't they here?
link |
01:32:44.060
Because by the time they got to the technological development
link |
01:32:47.020
where they could travel here, they blew themselves up.
link |
01:32:49.140
They destroyed themselves.
link |
01:32:50.300
And that's an unfortunate,
link |
01:32:53.060
but not a hard to imagine possibility
link |
01:32:57.100
based on things that have happened here on planet Earth.
link |
01:33:01.020
But putting that to the side,
link |
01:33:02.980
I think that's the big obstacle,
link |
01:33:05.460
but putting that to the side,
link |
01:33:06.460
we will resolve the engineering challenges.
link |
01:33:09.140
And I should probably modify my answer
link |
01:33:12.940
from before when you said, is it engineering or physics?
link |
01:33:15.940
It's really both, right?
link |
01:33:17.460
So we will surmount the engineering challenges
link |
01:33:20.460
and that will then make the physics challenges relevant.
link |
01:33:23.620
It'll make it relevant to figure out
link |
01:33:24.980
how to travel near the speed of light.
link |
01:33:26.900
It'll make it relevant to learn
link |
01:33:27.980
how to manipulate the shape of space time and so forth.
link |
01:33:32.180
So I think it's a multi stage process
link |
01:33:35.660
where it is engineering and ultimately physics.
link |
01:33:38.100
And if we stick around long enough,
link |
01:33:40.380
those are the kinds of challenges
link |
01:33:41.380
I think that we're ultimately gonna surmount.
link |
01:33:43.460
And then the physics side is figuring out
link |
01:33:45.340
how to harness energy enough
link |
01:33:46.700
to travel outside the solar system,
link |
01:33:48.700
which seems like a heck of a difficult journey.
link |
01:33:51.140
But even Mars itself,
link |
01:33:54.780
I don't know, maybe because I was born in the Soviet Union
link |
01:33:57.420
and was born with the,
link |
01:34:02.140
looking up at the stars and that dream
link |
01:34:04.660
of like the highest of human achievement
link |
01:34:06.740
is the ability to fly out there,
link |
01:34:08.900
to join the stars.
link |
01:34:10.380
I really liked the idea of going to Mars
link |
01:34:13.220
and not just stepping foot on Mars.
link |
01:34:15.580
And it wasn't until maybe misinformed,
link |
01:34:21.060
but for me personally,
link |
01:34:23.860
it wasn't until Elon Musk started talking
link |
01:34:26.420
about the colonization of Mars,
link |
01:34:28.700
did I realize like we humans can actually do that.
link |
01:34:34.300
And first of all, the importance of somebody saying
link |
01:34:38.100
that we can do these seemingly impossible things
link |
01:34:42.780
is immeasurable because the fact that he placed that
link |
01:34:48.660
into my mind and into the minds of millions of others,
link |
01:34:52.140
maybe hundreds of millions, maybe billions of others,
link |
01:34:54.860
young kids today, I mean, that's gonna make it a reality.
link |
01:34:58.660
I, for some reason, am deeply excited,
link |
01:35:01.860
even though my work isn't AI that echoes all of this.
link |
01:35:06.260
I'm excited by the idea that somebody would be born,
link |
01:35:09.500
as we were saying, on Mars and sort of look up
link |
01:35:14.180
and be able to see with a telescope Earth
link |
01:35:16.660
and say, that's where I came from.
link |
01:35:19.340
I don't know, that idea scale to other planets,
link |
01:35:23.540
to other solar systems, that's really exciting.
link |
01:35:26.620
And hugely exciting.
link |
01:35:28.020
I think you're absolutely right.
link |
01:35:29.300
I mean, the vital thing is to dream, right?
link |
01:35:33.820
I mean, and it sounds hackneyed,
link |
01:35:36.380
but it is so important for young kids,
link |
01:35:40.340
for the next generation,
link |
01:35:42.220
to think about the things that are seemingly impossible.
link |
01:35:45.460
I mean, that's what makes them possible.
link |
01:35:47.140
And this is one which is concrete enough.
link |
01:35:50.300
I mean, this is something that's gonna happen soon
link |
01:35:52.100
in terms of actually going to Mars.
link |
01:35:54.820
And then the next step of establishing some presence,
link |
01:36:00.340
some semi permanent or permanent presence.
link |
01:36:02.620
This is not something that's gonna wait
link |
01:36:05.460
to the 25th century.
link |
01:36:06.580
I mean, this is something that's gonna happen
link |
01:36:07.740
relatively soon.
link |
01:36:09.140
So, I mean, it could well be in your lifetime,
link |
01:36:11.220
unlikely mine, but possibly in your lifetime
link |
01:36:13.660
that that kid will be born
link |
01:36:15.460
and have the experience that you described.
link |
01:36:18.260
So yeah, it's spectacularly exciting.
link |
01:36:21.620
And I actually, I would love to go on Mars
link |
01:36:24.260
on one of the early.
link |
01:36:25.900
You would? Yeah.
link |
01:36:26.740
It would if it's one way.
link |
01:36:28.180
I'm happy to do it one way. Really?
link |
01:36:29.900
Wow. Yeah.
link |
01:36:30.740
I'm single if there's ladies out there
link |
01:36:32.540
that wanna start that family.
link |
01:36:34.540
Let's go out to Mars.
link |
01:36:36.540
No, I think.
link |
01:36:37.740
See, I have to tell you something.
link |
01:36:38.580
You spoke about terror, thinking about like black holes.
link |
01:36:42.700
If I actually think about going to Mars
link |
01:36:45.420
and being on Mars and put myself in there fully,
link |
01:36:49.740
that's terror inducing.
link |
01:36:51.780
The idea of to be in this foreign world
link |
01:36:54.940
where you can't come back,
link |
01:36:56.740
where you've made this choice that can't be reversed.
link |
01:37:00.060
Well, at some point it may be,
link |
01:37:01.700
but in that guise, that to me carries a deep sense of terror.
link |
01:37:08.780
I feel that sense of terror every time Kerouac,
link |
01:37:11.100
Jack Kerouac talked about this on the road
link |
01:37:13.860
is when you leave a place, if you're honest about it,
link |
01:37:18.540
like life is short.
link |
01:37:20.740
And when you leave a place, you move to a new place
link |
01:37:23.140
and you think of all the friends, maybe family
link |
01:37:25.220
you're leaving behind as you drive over the hill,
link |
01:37:28.060
that really is goodbye.
link |
01:37:31.460
Like we sometimes don't think of it that way
link |
01:37:33.260
when we're moving, but that really is goodbye to that life,
link |
01:37:36.220
to the person you were, to all the people.
link |
01:37:38.620
Maybe if it's close friends, you'll see them maybe 10, 15
link |
01:37:41.780
more times in your life and that's it.
link |
01:37:43.820
And you're saying goodbye to all of that.
link |
01:37:46.100
And so in the same way, I see it as way more dramatic
link |
01:37:50.180
when you're flying away from earth and it's like,
link |
01:37:52.620
it's goodbye to Dunkin Donuts and Starbucks.
link |
01:37:56.180
And it's goodbye to whatever, I don't know why I picked
link |
01:37:59.420
those, but some, all the things that are special to earth,
link |
01:38:03.820
it's goodbye, but that's life.
link |
01:38:06.900
I suppose more, what excites me about that kind of journey
link |
01:38:11.700
is it's a distinct contemplation of your mortality,
link |
01:38:14.780
acceptance of your mortality.
link |
01:38:16.660
You're saying, just like when you take on any difficult
link |
01:38:20.420
journey, it's accepting that you're going to die one day
link |
01:38:25.180
and might as well do something truly exciting.
link |
01:38:28.740
Yes, I mean, I will, you know, I'm with you on that.
link |
01:38:31.580
I'm a strong believer that deep underneath human motivation
link |
01:38:36.780
is this terror of our own mortality.
link |
01:38:41.020
Yeah, there's this a wonderful book that had a great
link |
01:38:43.180
influence in me called The Denial of Death by Ernest Becker.
link |
01:38:47.580
And when you are aware of the ways in which our mortality
link |
01:38:52.580
influences our behaviors, it really does add a different
link |
01:38:57.020
slant, a different kind of color to the interpretation
link |
01:38:59.940
of human behavior.
link |
01:39:01.620
Yeah, it's funny that that book had a big influence
link |
01:39:05.620
in me as well.
link |
01:39:06.460
Oh, is that right?
link |
01:39:07.300
Wow.
link |
01:39:08.140
And the terror management theory and I, again,
link |
01:39:12.140
from an engineering perspective, I don't know how many
link |
01:39:14.620
people that book influenced because I talk to people
link |
01:39:19.100
about the fear of death and it doesn't seem like
link |
01:39:21.220
about the fear of death and it doesn't seem to be
link |
01:39:24.140
that fundamental to their experience.
link |
01:39:26.580
And I don't think on the surface it's fundamental
link |
01:39:28.860
to my experience, but it seems like an awfully,
link |
01:39:30.740
in terms of we talk about models and strength theory
link |
01:39:33.380
and theories, in terms of theories of this macro experience
link |
01:39:37.380
of human life, it seems like a heck of a good theory
link |
01:39:40.940
that the fear of death is at the kind of is the warm
link |
01:39:43.980
at the core.
link |
01:39:44.820
Yeah, well, I mean, and the terror management theories
link |
01:39:47.420
that you make reference to, I mean, this is a group
link |
01:39:51.060
of psychologists, social psychologists who devise
link |
01:39:54.380
these very clever experiments, real world experiments
link |
01:39:58.340
with real people, where you can directly measure
link |
01:40:02.140
the hidden influence of the recognition
link |
01:40:05.580
of our own mortality.
link |
01:40:07.460
I mean, they've done these experiments where they have
link |
01:40:09.220
group of people A, group of people B,
link |
01:40:11.540
and the only difference between the two groups
link |
01:40:12.900
is that group B, they somehow reminded them
link |
01:40:16.180
in some subtle way of their own mortality.
link |
01:40:18.060
Sometimes it's nothing more than interviewing them
link |
01:40:21.180
with a funeral home across the street.
link |
01:40:23.940
And influence is there, but it's subtle,
link |
01:40:25.820
you don't even think you'd take note of.
link |
01:40:27.500
And they can find measurable effects that differentiate
link |
01:40:32.260
the two groups to a high degree of statistical significance
link |
01:40:36.300
and how they respond to certain challenges
link |
01:40:38.900
or certain kinds of questions that shows a direct influence
link |
01:40:42.820
of the reminder of their own mortality.
link |
01:40:45.980
And I've read a number of these studies
link |
01:40:48.620
and they are really convincing.
link |
01:40:51.660
And so yeah, I would say that the reason why
link |
01:40:54.060
so many people would say that, yeah, fear of mortality,
link |
01:40:58.060
it's not front and center in my worldview.
link |
01:41:01.140
Yeah, I don't really think about it much,
link |
01:41:02.380
it doesn't really matter too much.
link |
01:41:03.300
The reason why they're able to say that
link |
01:41:05.100
is because this thing called culture has emerged
link |
01:41:08.540
over the course of the last 10,000 years.
link |
01:41:10.780
And part of the role of culture is to give us a means
link |
01:41:14.260
of not thinking about our mortality all the time,
link |
01:41:17.060
of not living in terror of the inevitable end,
link |
01:41:20.020
which faces us all.
link |
01:41:21.780
So it's completely understandable that that's the response
link |
01:41:24.500
because that's what culture is at least in part for.
link |
01:41:27.860
Is it at least possible that the fear of death,
link |
01:41:32.300
the terror of your mortality is the creative force
link |
01:41:36.300
that created all of the things around us
link |
01:41:39.020
at this human civilization?
link |
01:41:41.540
And I think about from an engineering perspective,
link |
01:41:45.020
this is where I lose all of my robotics colleagues
link |
01:41:49.220
is I feel like if you want to create intelligence,
link |
01:41:52.580
you have to also engineer in some kind of echoes
link |
01:41:58.140
of this kind of fear.
link |
01:42:01.580
Fear is such a complicated word,
link |
01:42:03.420
but it's kind of like a scarcity,
link |
01:42:06.860
a scarcity of time, a scarcity of resources
link |
01:42:10.540
that creates a kind of anxiety,
link |
01:42:12.500
like deadlines get you to do stuff.
link |
01:42:15.460
And there's something almost fundamental to that
link |
01:42:18.460
in terms of human experience.
link |
01:42:21.460
Yeah, well, that's an interesting thought.
link |
01:42:22.660
So you're basically in order to create a kind of structure
link |
01:42:30.940
that mirrors what we call consciousness.
link |
01:42:34.300
You'd better have that structure confront the same kinds
link |
01:42:38.820
of issues and terrors that we do.
link |
01:42:41.980
Consciousness and suffering only makes sense
link |
01:42:44.180
in the context of death.
link |
01:42:45.620
If you want to, I feel like,
link |
01:42:48.100
if you want to fit into human society,
link |
01:42:50.740
if you're a robot and if you want to fit into human society,
link |
01:42:54.420
you better have the same kind of existential dread,
link |
01:42:59.100
the same kind of fear of mortality,
link |
01:43:00.740
otherwise you're not gonna fit in.
link |
01:43:02.340
Right.
link |
01:43:03.180
Right.
link |
01:43:04.020
That's good.
link |
01:43:06.180
It might be wild, but it's at least,
link |
01:43:09.580
like we're talking about all the theories
link |
01:43:11.380
that are at least worth consideration.
link |
01:43:13.700
I think that's a really powerful one.
link |
01:43:15.780
And definitely one has resonated with me
link |
01:43:19.180
and definitely seems to capture something
link |
01:43:25.700
beautifully like real about the human condition.
link |
01:43:31.340
And I wonder, it's of course,
link |
01:43:34.180
it sucks to think that we need death to appreciate life,
link |
01:43:40.340
but that's just maybe the way it is.
link |
01:43:43.180
Well, it's interesting if this robotic
link |
01:43:44.500
or artificially intelligent system understands the world
link |
01:43:49.420
and understands the second law of thermodynamics
link |
01:43:51.700
and entropy, even an artificial intelligence will realize
link |
01:43:55.540
that even if its parts are really robust,
link |
01:43:59.220
ultimately it will disintegrate.
link |
01:44:02.380
Yeah.
link |
01:44:03.220
The timescales may be different,
link |
01:44:05.180
but in a way, when you think about it, it doesn't matter.
link |
01:44:06.980
Once you know that you are mortal
link |
01:44:09.220
in the sense that you are not eternal,
link |
01:44:11.580
the timescale hardly matters
link |
01:44:13.740
because it's either the whole thing or not.
link |
01:44:17.940
Because on the scales of eternity,
link |
01:44:19.740
any finite duration, however large is effectively zero
link |
01:44:23.700
on the scales of eternity.
link |
01:44:25.580
And so maybe it won't be so hard for an artificial system
link |
01:44:28.820
to feel that sense of mortality
link |
01:44:32.020
because it will recognize the underlying physical laws
link |
01:44:35.220
and recognize its own finitude.
link |
01:44:38.540
And then it'll be us and robots drinking beers,
link |
01:44:41.340
looking up at the stars and just,
link |
01:44:48.500
having a good laugh in awe of the whole thing.
link |
01:44:51.100
Yeah.
link |
01:44:53.140
I think that's a pretty good way to end it,
link |
01:44:55.500
talking about the fear of death.
link |
01:44:57.340
We started talking about the meaning of life
link |
01:44:59.820
and ended on the fear of death.
link |
01:45:01.060
Brian, this is an incredible conversation.
link |
01:45:03.140
My pleasure, thank you.
link |
01:45:03.980
I enjoyed it enormously.
link |
01:45:04.820
I really, really enjoyed it.
link |
01:45:05.660
It's been a long time coming.
link |
01:45:06.700
I'm a huge fan of your work, a huge fan of your writing.
link |
01:45:09.700
Thanks for talking to me, Brian.
link |
01:45:10.700
Thank you.
link |
01:45:12.060
Thanks for listening to this conversation
link |
01:45:13.580
with Brian Greene.
link |
01:45:14.780
To support this podcast,
link |
01:45:16.100
please check out our sponsors in the description.
link |
01:45:18.900
And now, let me leave you with some words from Bill Bryson.
link |
01:45:22.940
"'Physics is really nothing more
link |
01:45:25.500
"'than a search for ultimate simplicity.
link |
01:45:27.860
"'But so far, all we have is a kind of elegant messiness.'"
link |
01:45:32.860
Thank you for listening and hope to see you next time.