Toward a Fundamental Theory of Physics (Stephen Wolfram) | AI Podcast Clips
00:00:00.000 | - What kind of computation do you think
00:00:05.000 | the fundamental laws of physics might emerge from?
00:00:09.200 | So just to clarify, so you've done a lot of fascinating work
00:00:13.900 | with kind of discrete kinds of computation that,
00:00:17.400 | you know, you could sell your automata,
00:00:20.080 | and we'll talk about it, have this very clean structure.
00:00:24.080 | It's such a nice way to demonstrate that simple rules
00:00:27.400 | can create immense complexity.
00:00:29.560 | But what, you know, is that actually,
00:00:34.560 | are cellular automata sufficiently general
00:00:36.440 | to describe the kinds of computation
00:00:39.000 | that might create the laws of physics?
00:00:41.640 | Just to give, can you give a sense of
00:00:43.840 | what kind of computation do you think
00:00:45.880 | would create the laws of physics?
00:00:47.720 | - So this is a slightly complicated issue,
00:00:49.640 | because as soon as you have universal computation,
00:00:52.600 | you can, in principle, simulate anything with anything.
00:00:55.640 | But it is not a natural thing to do,
00:00:58.080 | and if you're asking, were you to try to find
00:01:00.920 | our physical universe by looking at possible programs
00:01:04.400 | in the computational universe of all possible programs,
00:01:07.260 | would the ones that correspond to our universe
00:01:10.300 | be small and simple enough that we might find them
00:01:13.320 | by searching that computational universe?
00:01:15.600 | We gotta have the right basis, so to speak.
00:01:17.500 | We have to have the right language in effect
00:01:19.800 | for describing computation for that to be feasible.
00:01:22.840 | So the thing that I've been interested in for a long time
00:01:24.880 | is what are the most structuralist structures
00:01:27.460 | that we can create with computation?
00:01:29.720 | So in other words, if you say a cellular automaton
00:01:32.520 | has a bunch of cells that are arrayed on a grid,
00:01:35.400 | and it's very, you know, and every cell is updated
00:01:38.040 | in synchrony at a particular, you know,
00:01:40.440 | when there's a click of a clock, so to speak,
00:01:43.400 | and it goes a tick of a clock,
00:01:45.480 | and every cell gets updated at the same time.
00:01:48.000 | That's a very specific, very rigid kind of thing.
00:01:51.440 | But my guess is that when we look at physics,
00:01:54.880 | and we look at things like space and time,
00:01:57.080 | that what's underneath space and time
00:01:59.420 | is something as structureless as possible.
00:02:02.080 | That what we see, what emerges for us as physical space,
00:02:06.040 | for example, comes from something
00:02:08.380 | that is sort of arbitrarily unstructured underneath.
00:02:11.940 | And so I've been for a long time interested in kind of
00:02:14.800 | what are the most structuralist structures
00:02:17.220 | that we can set up?
00:02:18.620 | And actually what I had thought about for ages
00:02:21.820 | is using graphs, networks, where essentially,
00:02:25.580 | so let's talk about space, for example.
00:02:28.100 | So what is space?
00:02:29.860 | Is a kind of a question one might ask.
00:02:32.360 | Back in the early days of quantum mechanics, for example,
00:02:34.580 | people said, "Oh, for sure, space is gonna be discrete,
00:02:37.900 | "'cause all these other things we're finding are discrete."
00:02:39.820 | But that never worked out in physics.
00:02:41.880 | And so space and physics today is always treated
00:02:44.560 | as this continuous thing, just like Euclid imagined it.
00:02:47.940 | I mean, the very first thing Euclid says
00:02:50.080 | in his sort of common notions is, you know,
00:02:52.580 | "A point is something which has no part."
00:02:54.740 | In other words, there are points that are arbitrarily small
00:02:58.340 | and there's a continuum of possible positions of points.
00:03:01.820 | And the question is, is that true?
00:03:03.780 | And so, for example, if we look at, I don't know,
00:03:05.540 | fluid like air or water,
00:03:07.460 | we might say, "Oh, it's a continuous fluid.
00:03:09.100 | "We can pour it, we can do all kinds of things continuously."
00:03:12.260 | But actually we know, 'cause we know the physics of it,
00:03:14.620 | that it consists of a bunch of discrete molecules
00:03:16.500 | bouncing around and only in the aggregate
00:03:18.980 | is it behaving like a continuum.
00:03:21.420 | And so the possibility exists that that's true of space too.
00:03:24.660 | People haven't managed to make that work
00:03:26.340 | with existing frameworks and physics,
00:03:29.460 | but I've been interested in whether one can imagine
00:03:32.540 | that underneath space and also underneath time
00:03:35.780 | is something more structureless.
00:03:37.700 | And the question is, is it computational?
00:03:40.540 | So there are a couple of possibilities.
00:03:42.740 | It could be computational,
00:03:43.880 | somehow fundamentally equivalent to a Turing machine,
00:03:46.400 | or it could be fundamentally not.
00:03:48.420 | So how could it not be?
00:03:49.820 | It could not be, so a Turing machine
00:03:51.620 | essentially deals with integers, whole numbers, some level.
00:03:55.140 | And it can do things like it can add one to a number,
00:03:58.060 | it can do things like this.
00:03:59.500 | - It can also store whatever the heck it did.
00:04:01.940 | - Yes, it has an infinite storage.
00:04:05.460 | But when one thinks about doing physics
00:04:09.580 | or sort of idealized physics or idealized mathematics,
00:04:13.580 | one can deal with real numbers,
00:04:15.440 | numbers with an infinite number of digits,
00:04:17.660 | numbers which are absolutely precise.
00:04:19.940 | And one can say, we can take this number
00:04:21.660 | and we can multiply it by itself.
00:04:23.340 | - Are you comfortable with infinity in this context?
00:04:26.140 | Are you comfortable in the context of computation?
00:04:29.140 | Do you think infinity plays a part?
00:04:31.400 | - I think that the role of infinity is complicated.
00:04:33.740 | Infinity is useful in conceptualizing things.
00:04:37.860 | It's not actualizable.
00:04:40.060 | Almost by definition, it's not actualizable.
00:04:42.700 | - But do you think infinity is part of the thing
00:04:44.740 | that might underlie the laws of physics?
00:04:47.380 | - I think that, no.
00:04:49.300 | I think there are many questions that you ask about,
00:04:51.660 | you might ask about physics,
00:04:52.940 | which inevitably involve infinity.
00:04:54.420 | Like when you say, is faster than light travel possible?
00:04:58.420 | You could say, given the laws of physics,
00:05:02.180 | can you make something even arbitrarily large,
00:05:04.480 | even quotes infinitely large,
00:05:06.700 | that will make faster than light travel possible?
00:05:10.180 | Then you're thrown into dealing with infinity
00:05:12.460 | as a kind of theoretical question.
00:05:14.580 | But I mean, talking about sort of
00:05:16.740 | what's underneath space and time
00:05:18.580 | and how one can make a computational infrastructure,
00:05:23.060 | one possibility is that you can't make
00:05:25.540 | a computational infrastructure in a Turing machine sense,
00:05:29.680 | that you really have to be dealing with precise real numbers,
00:05:32.580 | you're dealing with partial differential equations,
00:05:34.340 | which have precise real numbers
00:05:37.580 | at arbitrarily closely separated points.
00:05:39.600 | You have a continuum for everything.
00:05:42.260 | Could be that that's what happens,
00:05:44.120 | that there's sort of a continuum for everything
00:05:45.700 | and precise real numbers for everything.
00:05:47.140 | And then the things I'm thinking about are wrong.
00:05:50.100 | And that's the risk you take
00:05:52.620 | if you're trying to sort of do things about nature,
00:05:56.680 | is you might just be wrong.
00:05:58.180 | For me personally, it's kind of a strange thing,
00:06:02.060 | 'cause I've spent a lot of my life building technology
00:06:04.500 | where you can do something that nobody cares about,
00:06:07.580 | but you can't be sort of wrong in that sense,
00:06:09.980 | in the sense you build your technology
00:06:11.460 | and it does what it does.
00:06:12.860 | But I think this question of what
00:06:16.100 | the sort of underlying computational infrastructure
00:06:18.100 | for the universe might be,
00:06:19.440 | so it's sort of inevitable it's gonna be fairly abstract,
00:06:24.900 | because if you're gonna get all these things,
00:06:27.820 | like there are three dimensions of space,
00:06:29.380 | there are electrons, there are muons,
00:06:30.860 | there are quarks, there are this,
00:06:32.680 | you don't get to, if the model for the universe is simple,
00:06:36.900 | you don't get to have sort of a line of code
00:06:38.900 | for each of those things.
00:06:39.820 | You don't get to have sort of the muon case,
00:06:43.900 | the tau lepton case and so on.
00:06:45.900 | - All of those things have to be emergent somehow.
00:06:47.780 | - Right.
00:06:48.620 | - So something deeper.
00:06:49.860 | - Right, so that means it's sort of inevitable
00:06:52.060 | that it's a little hard to talk about
00:06:53.860 | what the sort of underlying
00:06:55.260 | structuralist structure actually is.
00:06:57.260 | - Do you think human beings have the cognitive capacity
00:07:01.300 | to understand, if we're to discover it,
00:07:03.300 | to understand the kinds of simple structure
00:07:06.860 | from which these laws can emerge?
00:07:08.740 | Like, do you think that's a hopeless pursuit?
00:07:11.300 | - Well, here's what I think.
00:07:12.220 | I think that, I mean, I'm right in the middle
00:07:14.660 | of this right now.
00:07:15.500 | So I'm telling you that I--
00:07:16.340 | - Do you think you're hit a wall?
00:07:17.900 | - Yeah, I mean, this human has a hard time understanding
00:07:22.180 | a bunch of the things that are going on.
00:07:23.460 | But what happens in understanding is,
00:07:25.900 | one builds waypoints.
00:07:27.140 | I mean, if you said,
00:07:28.300 | understand modern 21st century mathematics,
00:07:31.220 | starting from counting back in,
00:07:35.780 | whenever counting was invented 50,000 years ago,
00:07:37.900 | whatever it was, right?
00:07:39.980 | That will be really difficult.
00:07:41.540 | But what happens is we build waypoints
00:07:43.620 | that allow us to get to higher levels of understanding.
00:07:46.340 | And we see the same thing happening in language.
00:07:48.540 | You know, when we invent a word for something,
00:07:50.900 | it provides kind of a cognitive anchor,
00:07:53.260 | a kind of a waypoint that lets us, you know,
00:07:55.500 | like a podcast or something.
00:07:57.640 | You could be explaining, well, it's a thing,
00:07:59.700 | which this works this way, that way, the other way.
00:08:02.180 | But as soon as you have the word podcast
00:08:04.780 | and people kind of societally understand it,
00:08:07.460 | you start to be able to build on top of that.
00:08:09.420 | And so I think,
00:08:10.260 | and that's kind of the story of science actually too.
00:08:12.780 | I mean, science is about building these kinds of waypoints
00:08:15.820 | where we find this sort of cognitive mechanism
00:08:19.240 | for understanding something,
00:08:20.320 | then we can build on top of it.
00:08:21.460 | You know, we have the idea of, I don't know,
00:08:23.780 | differential equations, we can build on top of that.
00:08:26.380 | We have this idea or that idea.
00:08:28.020 | So my hope is that if it is the case
00:08:31.400 | that we have to go all the way
00:08:33.060 | sort of from the sand to the computer,
00:08:35.780 | and there's no waypoints in between, then we're toast.
00:08:39.580 | We won't be able to do that.
00:08:40.940 | - Well, eventually we might.
00:08:42.260 | So if we're, us clever apes are good enough
00:08:45.700 | for building those abstractions,
00:08:47.580 | eventually from sand we'll get to the computer, right?
00:08:50.220 | And it just might be a longer journey than-
00:08:51.820 | - The question is whether it is something that,
00:08:53.820 | you asked whether our human brains
00:08:56.500 | will quote, "Understand what's going on."
00:08:59.300 | And that's a different question,
00:09:00.620 | because for that, it requires steps that are,
00:09:04.220 | for whether it's sort of,
00:09:05.780 | from which we can construct
00:09:07.140 | a human understandable narrative.
00:09:09.420 | And that's something that I think
00:09:12.180 | I am somewhat hopeful that that will be possible.
00:09:15.100 | Although, as of literally today, if you ask me,
00:09:19.120 | I'm confronted with things that I don't understand very well.
00:09:22.120 | - So this is a small pattern in a computation
00:09:25.820 | trying to understand the rules
00:09:27.880 | under which the computation functions.
00:09:29.820 | And it's an interesting possibility
00:09:33.500 | under which kinds of computations
00:09:35.700 | such a creature can understand itself.
00:09:38.700 | - My guess is that within,
00:09:40.620 | so we didn't talk much about computational irreducibility,
00:09:43.260 | but it's a consequence of this principle
00:09:44.860 | of computational equivalence.
00:09:46.420 | And it's sort of a core idea
00:09:47.660 | that one has to understand, I think, which is,
00:09:50.140 | question is, you're doing a computation,
00:09:52.580 | you can figure out what happens in the computation
00:09:54.820 | just by running every step in the computation
00:09:56.820 | and seeing what happens.
00:09:58.460 | Or you can say, let me jump ahead and figure out,
00:10:02.780 | have something smarter that figures out
00:10:04.660 | what's gonna happen before it actually happens.
00:10:07.020 | And a lot of traditional science
00:10:09.380 | has been about that act of computational reducibility.
00:10:13.260 | It's like, we've got these equations
00:10:15.820 | and we can just solve them
00:10:16.900 | and we can figure out what's gonna happen.
00:10:18.140 | We don't have to trace all of those steps,
00:10:20.460 | we just jump ahead 'cause we solved these equations.
00:10:23.260 | Okay, so one of the things that is a consequence
00:10:25.500 | of the principle of computational equivalence
00:10:27.060 | is you don't always get to do that.
00:10:28.980 | Many, many systems will be computationally irreducible
00:10:32.260 | in the sense that the only way to find out what they do
00:10:34.240 | is just follow each step and see what happens.
00:10:36.520 | Why is that?
00:10:37.360 | Well, if you're saying,
00:10:38.740 | well, we, with our brains, we're a lot smarter.
00:10:41.540 | We don't have to mess around
00:10:43.260 | like the little cellular automaton
00:10:45.000 | going through and updating all those cells.
00:10:47.020 | We can just use the power of our brains to jump ahead.
00:10:50.980 | But if the principle of computational equivalence is right,
00:10:53.860 | that's not gonna be correct
00:10:55.120 | because it means that there's us
00:10:58.340 | doing our computation in our brains,
00:11:00.460 | there's a little cellular automaton doing its computation,
00:11:03.240 | and the principle of computational equivalence says,
00:11:05.620 | these two computations are fundamentally equivalent.
00:11:08.540 | So that means we don't get to say,
00:11:10.320 | we're a lot smarter than the cellular automaton
00:11:12.140 | and jump ahead 'cause we're just doing computation
00:11:14.900 | that's of the same sophistication
00:11:16.700 | as the cellular automaton itself.
00:11:18.720 | - That's computational irreducibility.
00:11:20.300 | It's fascinating, and that's a really powerful idea.
00:11:23.740 | I think that's both depressing and humbling and so on,
00:11:28.660 | that we're all, we and a cellular automaton are the same.
00:11:31.300 | But the question we're talking about,
00:11:33.000 | the fundamental laws of physics,
00:11:35.020 | is kind of the reverse question.
00:11:37.100 | You're not predicting what's gonna happen.
00:11:39.300 | You have to run the universe for that.
00:11:41.260 | But saying, can I understand what rules likely generated me?
00:11:45.280 | - I understand, but the problem is,
00:11:48.060 | to know whether you're right,
00:11:50.280 | you have to have some computational reducibility
00:11:53.020 | because we are embedded in the universe.
00:11:55.020 | If the only way to know whether we get the universe
00:11:57.060 | is just to run the universe, we don't get to do that
00:11:59.940 | 'cause it just ran for 14.6 billion years or whatever,
00:12:02.980 | and we can't rerun it, so to speak.
00:12:05.680 | So we have to hope that there are pockets
00:12:08.020 | of computational reducibility
00:12:10.380 | sufficient to be able to say,
00:12:11.980 | yes, I can recognize those are electrons there.
00:12:15.020 | And I think that it's a feature
00:12:17.740 | of computational irreducibility.
00:12:19.700 | It's sort of a mathematical feature
00:12:21.020 | that there are always an infinite collection
00:12:22.740 | of pockets of reducibility.
00:12:24.780 | The question of whether they land in the right place
00:12:26.660 | and whether we can sort of build a theory
00:12:28.460 | based on them is unclear.
00:12:30.100 | But to this point about whether we,
00:12:32.860 | as observers in the universe,
00:12:34.260 | built out of the same stuff as the universe,
00:12:36.740 | can figure out the universe, so to speak,
00:12:39.620 | that relies on these pockets of reducibility.
00:12:42.620 | Without the pockets of reducibility,
00:12:44.180 | it won't work, can't work.
00:12:46.240 | But I think this question about how observers operate,
00:12:49.440 | it's one of the features of science
00:12:52.120 | over the last hundred years particularly,
00:12:54.100 | has been that every time we get more realistic
00:12:56.720 | about observers, we learn a bit more about science.
00:13:00.100 | So for example, relativity was all about
00:13:02.740 | observers don't get to say when,
00:13:05.860 | you know, what's simultaneous with what.
00:13:07.420 | They have to just wait for the light signal to arrive
00:13:09.660 | to decide what's simultaneous.
00:13:11.780 | Or for example, in thermodynamics,
00:13:14.580 | observers don't get to say the position
00:13:16.420 | of every single molecule in a gas.
00:13:19.060 | They can only see the kind of large scale features
00:13:21.380 | and that's why the second law of thermodynamics,
00:13:23.700 | law of entropy increase and so on works.
00:13:25.980 | If you could see every individual molecule,
00:13:28.420 | you wouldn't conclude something about thermodynamics.
00:13:32.680 | You would conclude, oh, these molecules
00:13:34.340 | just all doing these particular things.
00:13:35.700 | You wouldn't be able to see this aggregate fact.
00:13:38.420 | So I strongly expect that,
00:13:41.100 | and in fact, in the theories that I have,
00:13:43.500 | that one has to be more realistic
00:13:45.900 | about the computation and other aspects of observers
00:13:49.860 | in order to actually make a correspondence
00:13:52.580 | between what we experience.
00:13:53.580 | In fact, my little team and I have a little theory
00:13:57.400 | right now about how quantum mechanics may work,
00:13:59.820 | which is a very wonderfully bizarre idea
00:14:03.340 | about how the sort of thread of human consciousness
00:14:07.460 | relates to what we observe in the universe.
00:14:10.540 | But there's several steps to explain what that's about.
00:14:13.540 | - What do you make of the mess of the observer
00:14:16.140 | at the lower level of quantum mechanics?
00:14:18.700 | Sort of the textbook definition with quantum mechanics
00:14:23.700 | kind of says that there's two worlds.
00:14:27.540 | One is the world that actually is,
00:14:30.940 | and the other is that's observed.
00:14:32.920 | What do you make sense of that kind of observing?
00:14:36.820 | - Well, I think actually the ideas we've recently had
00:14:39.900 | might actually give away into this.
00:14:43.580 | And that's, I don't know yet.
00:14:47.220 | I mean, I think that's, it's a mess.
00:14:50.060 | I mean, the fact is there is a,
00:14:52.540 | one of the things that's interesting,
00:14:54.620 | and when people look at these models
00:14:56.740 | that I started talking about 30 years ago now,
00:14:59.380 | they say, "Oh no, that can't possibly be right.
00:15:01.980 | "What about quantum mechanics?"
00:15:03.660 | Right?
00:15:04.500 | And you say, "Okay, tell me what is the essence
00:15:06.460 | "of quantum mechanics?
00:15:07.300 | "What do you want me to be able to reproduce
00:15:09.220 | "to know that I've got quantum mechanics, so to speak?"
00:15:12.340 | Well, and that question comes up,
00:15:14.140 | comes up very operational actually,
00:15:15.540 | because we've been doing a bunch of stuff
00:15:16.700 | with quantum computing,
00:15:18.060 | and there are all these companies that say,
00:15:19.360 | "We have a quantum computer."
00:15:21.020 | We say, "Let's connect to your API,
00:15:23.020 | "and let's actually run it."
00:15:24.980 | And they're like, "Well, maybe you shouldn't do that yet.
00:15:28.260 | "We're not quite ready yet."
00:15:29.740 | And one of the questions that I've been curious about is,
00:15:32.220 | if I have five minutes with a quantum computer,
00:15:34.740 | how can I tell if it's really a quantum computer,
00:15:36.860 | or whether it's a simulator at the other end?
00:15:39.140 | Right?
00:15:39.980 | And turns out it's really hard.
00:15:40.860 | It turns out there isn't,
00:15:41.860 | it's like a lot of these questions about sort of,
00:15:44.900 | what is intelligence, what's life?
00:15:46.740 | - That's a boring test for a quantum computer.
00:15:49.020 | - That's right, that's right.
00:15:50.060 | It's like, are you really a quantum computer?
00:15:52.460 | And I think-- - Or just a simulation, yeah.
00:15:54.540 | - Yes, exactly.
00:15:55.380 | Is it just a simulation,
00:15:56.500 | or is it really a quantum computer?
00:15:58.140 | Same issue all over again.
00:16:00.020 | But that, so, you know, this whole issue
00:16:03.780 | about the sort of mathematical structure
00:16:06.140 | of quantum mechanics,
00:16:07.580 | and the completely separate thing that is our experience,
00:16:12.340 | in which we think definite things happen,
00:16:14.740 | whereas quantum mechanics doesn't say
00:16:16.100 | definite things ever happen.
00:16:17.540 | Quantum mechanics is all about the amplitudes
00:16:19.380 | for different things to happen.
00:16:21.020 | But yet, our thread of consciousness
00:16:24.460 | operates as if definite things are happening.
00:16:27.340 | - To linger on the point,
00:16:30.220 | you've kind of mentioned the structure
00:16:33.740 | that could underlie everything,
00:16:35.660 | and this idea that it could perhaps have something
00:16:38.860 | like the structure of a graph.
00:16:40.660 | Can you elaborate why your intuition is
00:16:43.660 | that there's a graph structure of nodes and edges,
00:16:46.340 | and what it might represent?
00:16:48.300 | - Right, okay.
00:16:49.340 | So the question is,
00:16:50.900 | what is, in a sense, the most structuralist structure
00:16:54.340 | you can imagine, right?
00:16:56.380 | So, and in fact, what I've recently realized
00:17:01.220 | in the last year or so,
00:17:02.580 | I have a new most structuralist structure.
00:17:05.540 | - By the way, the question itself is a beautiful one
00:17:08.260 | and a powerful one in itself.
00:17:09.700 | So even without an answer,
00:17:11.420 | just the question is a really strong question.
00:17:13.700 | - Right, right.
00:17:14.540 | - But what's your new idea?
00:17:16.140 | - Well, it has to do with hypergraphs.
00:17:18.060 | Essentially, what is interesting about the sort of model
00:17:23.620 | that I have now is it's a little bit like
00:17:26.500 | what happened with computation.
00:17:28.140 | Everything that I think of as,
00:17:29.940 | oh, well, maybe the model is this,
00:17:32.340 | I discover it's equivalent.
00:17:34.500 | And that's quite encouraging,
00:17:36.420 | because it's like I could say,
00:17:38.180 | well, I'm gonna look at trivalent graphs
00:17:40.500 | with three edges for each node and so on,
00:17:42.700 | or I could look at this special kind of graph,
00:17:44.780 | or I could look at this kind of algebraic structure,
00:17:48.060 | and turns out that the things I'm now looking at,
00:17:51.380 | everything that I've imagined
00:17:53.220 | that is a plausible type of structureless structure
00:17:56.260 | is equivalent to this.
00:17:57.820 | So what is it?
00:17:59.140 | Well, a typical way to think about it is,
00:18:01.820 | well, so you might have some collection of tuples,
00:18:08.260 | collection of, let's say numbers.
00:18:14.380 | So you might have one, three, five, two, three, four,
00:18:19.860 | little, just collections of numbers,
00:18:22.500 | triples of numbers, let's say,
00:18:23.780 | quadruples of numbers, pairs of numbers, whatever.
00:18:26.580 | And you have all these sort of floating little tuples.
00:18:31.020 | They're not in any particular order.
00:18:33.020 | And that sort of floating collection of tuples,
00:18:37.780 | and I told you this was abstract,
00:18:39.820 | represents the whole universe.
00:18:41.900 | The only thing that relates them
00:18:44.220 | is when a symbol is the same, it's the same, so to speak.
00:18:48.820 | So if you have two tuples,
00:18:50.340 | and they contain the same symbol,
00:18:52.500 | let's say at the same position of the tuple,
00:18:54.060 | the first element of the tuple,
00:18:55.540 | then that represents a relation.
00:18:57.860 | Okay, so let me try and peel this back.
00:19:00.860 | - Wow, okay.
00:19:01.940 | (laughing)
00:19:03.860 | - I told you it's abstract, but this is the--
00:19:06.820 | - So the relationship is formed
00:19:08.220 | by some aspect of sameness.
00:19:10.820 | - Right, but so think about it in terms of a graph.
00:19:13.660 | So a graph, a bunch of nodes,
00:19:16.620 | let's say you number each node, okay?
00:19:19.340 | Then what is a graph?
00:19:20.500 | A graph is a set of pairs that say,
00:19:23.340 | this node has an edge connecting it to this other node.
00:19:26.780 | So that's the, and a graph is just a collection
00:19:30.940 | of those pairs that say,
00:19:33.540 | this node connects to this other node.
00:19:35.540 | So this is a generalization of that,
00:19:38.020 | in which instead of having pairs,
00:19:39.940 | you have arbitrary and tuples.
00:19:42.020 | That's it, that's the whole story.
00:19:45.820 | And now the question is, okay,
00:19:47.300 | so that might represent the state of the universe.
00:19:50.620 | How does the universe evolve?
00:19:51.980 | What does the universe do?
00:19:53.500 | And so the answer is that what I'm looking at
00:19:56.140 | is transformation rules on these hypergraphs.
00:20:00.180 | In other words, you say this,
00:20:02.860 | whenever you see a piece of this hypergraph
00:20:07.380 | that looks like this,
00:20:09.300 | turn it into a piece of a hypergraph that looks like this.
00:20:12.220 | So on a graph, it might be, when you see the subgraph,
00:20:15.140 | when you see this thing with a bunch of edges hanging out
00:20:17.100 | in this particular way,
00:20:18.580 | then rewrite it as this other graph, okay?
00:20:22.340 | And so that's the whole story.
00:20:24.540 | So the question is, what, so now you say, I mean,
00:20:29.100 | as I say, this is quite abstract.
00:20:32.180 | And one of the questions is,
00:20:33.700 | where do you do those updating?
00:20:36.540 | So you've got this giant graph.
00:20:38.020 | - What triggers the updating?
00:20:39.380 | Like what's the ripple effect of it?
00:20:42.180 | Is it?
00:20:43.540 | - Yeah.
00:20:44.380 | I suspect everything's discrete, even in time, so.
00:20:48.980 | - Okay, so the question is, where do you do the updates?
00:20:51.420 | And the answer is, the rule is,
00:20:53.020 | you do them wherever they apply.
00:20:55.020 | And you do them, the order in which the updates is done
00:20:58.540 | is not defined.
00:21:00.020 | That is, you can do them,
00:21:01.780 | so there may be many possible orderings for these updates.
00:21:05.180 | Now, the point is,
00:21:06.180 | imagine you're an observer in this universe.
00:21:09.020 | So, and you say, did something get updated?
00:21:12.260 | Well, you don't in any sense know
00:21:14.580 | until you yourself have been updated.
00:21:16.800 | - Right.
00:21:18.620 | - So in fact, all that you can be sensitive to
00:21:21.940 | is essentially the causal network
00:21:24.160 | of how an event over there affects an event that's in you.
00:21:29.160 | - That doesn't even feel like observation.
00:21:32.100 | That's like, that's something else.
00:21:33.660 | You're just part of the whole thing.
00:21:35.220 | - Yes, you're part of it, but even to have,
00:21:37.700 | so the end result of that is all you're sensitive to
00:21:41.460 | is this causal network of what event affects
00:21:43.940 | what other event.
00:21:45.580 | I'm not making a big statement
00:21:47.420 | about sort of the structure of the observer.
00:21:49.920 | I'm simply saying, I'm simply making the argument
00:21:52.260 | that what happens, the microscopic order of these rewrites
00:21:56.820 | is not something that any observer,
00:21:59.980 | any conceivable observer in this universe
00:22:02.580 | can be affected by.
00:22:04.280 | Because the only thing the observer can be affected by
00:22:07.400 | is this causal network of how the events
00:22:11.180 | in the observer are affected by other events
00:22:14.100 | that happen in the universe.
00:22:15.060 | So the only thing you have to look at
00:22:16.300 | is the causal network.
00:22:17.620 | You don't really have to look at this microscopic rewriting
00:22:20.580 | that's happening.
00:22:21.400 | So these rewrites are happening wherever they,
00:22:24.140 | they happen wherever they feel like.
00:22:25.660 | - Causal network, is there,
00:22:27.820 | you said that there's not really,
00:22:30.900 | so the idea would be an undefined,
00:22:33.580 | like what gets updated, the sequence of things is undefined.
00:22:37.380 | - Yes.
00:22:39.660 | - Is that's what you mean by the causal network,
00:22:41.420 | but then the--
00:22:42.260 | - No, the causal network is given that an update has happened
00:22:45.520 | that's an event.
00:22:46.900 | Then the question is, is that event causally related to?
00:22:50.580 | Does that event, if that event didn't happen,
00:22:53.380 | then some future event couldn't happen yet.
00:22:55.820 | - Gotcha.
00:22:56.660 | - And so you build up this network of what affects what.
00:23:00.020 | Okay?
00:23:00.860 | And so what that does, so when you build up that network,
00:23:04.480 | that's kind of the observable aspect of the universe
00:23:07.380 | in some sense.
00:23:08.220 | - Gotcha.
00:23:09.040 | - And so then you can ask questions about, you know,
00:23:11.780 | how robust is that observable network
00:23:14.820 | of what's happening in the universe.
00:23:16.740 | Okay, so here's where it starts getting kind of interesting.
00:23:19.620 | So for certain kinds of microscopic rewriting rules,
00:23:23.340 | the order of rewrites does not matter
00:23:25.780 | to the causal network.
00:23:27.300 | And so this is, okay, mathematical logic moment,
00:23:31.060 | this is equivalent to the Church-Rosser property
00:23:33.340 | or the confluence property of rewrite rules.
00:23:35.700 | And it's the same reason that if you are simplifying
00:23:37.980 | an algebraic expression, for example,
00:23:40.120 | you can say, oh, let me expand those terms out,
00:23:42.460 | let me factor those pieces.
00:23:44.100 | Doesn't matter what order you do that in,
00:23:45.940 | you'll always get the same answer.
00:23:47.640 | And that's, it's the same fundamental phenomenon
00:23:50.720 | that causes for certain kinds of microscopic rewrite rules
00:23:54.560 | that causes the causal network to be independent
00:23:57.820 | of the microscopic order of rewritings.
00:24:00.600 | - Why is that property important?
00:24:02.800 | - 'Cause it implies special relativity.
00:24:05.800 | I mean, the reason it's important is that that property,
00:24:10.800 | special relativity says you can look at these sort of,
00:24:16.760 | you can look at different reference frames.
00:24:18.840 | You can have different, you can be looking at your notion
00:24:21.560 | of what space and what's time can be different,
00:24:24.540 | depending on whether you're traveling at a certain speed,
00:24:26.480 | depending on whether you're doing this, that, and the other.
00:24:28.860 | But nevertheless, the laws of physics are the same.
00:24:31.000 | That's what the principle of special relativity says,
00:24:33.900 | is the laws of physics are the same
00:24:35.240 | independent of your reference frame.
00:24:37.240 | Well, turns out this sort of change
00:24:41.680 | of the microscopic rewriting order
00:24:43.880 | is essentially equivalent to a change of reference frame,
00:24:46.100 | or at least there's a sub part of how that works
00:24:48.700 | that's equivalent to change of reference frame.
00:24:50.640 | So, somewhat surprisingly, and sort of for the first time
00:24:54.080 | in forever, it's possible for an underlying
00:24:57.040 | microscopic theory to imply special relativity,
00:25:00.440 | to be able to derive it.
00:25:01.520 | It's not something you put in as a,
00:25:03.960 | this is a, it's something where this other property,
00:25:07.320 | causal invariance, which is also the property
00:25:10.600 | that implies that there's a single thread of time
00:25:13.080 | in the universe.
00:25:14.440 | It might not be the case.
00:25:15.760 | That's what would lead to the possibility
00:25:20.320 | of an observer thinking that definite stuff happens.
00:25:23.720 | Otherwise, you've got all these possible rewriting orders,
00:25:26.200 | and who's to say which one occurred.
00:25:28.280 | But with this causal invariance property,
00:25:29.680 | there's a notion of a definite thread of time.
00:25:32.440 | - It sounds like that kind of idea of time,
00:25:34.880 | even space, would be emergent from the system.
00:25:37.920 | - Oh yeah.
00:25:38.760 | - So it's not a fundamental part of the system.
00:25:40.440 | - No, no, at a fundamental level,
00:25:42.440 | all you've got is a bunch of nodes connected
00:25:44.200 | by hyper edges or whatever.
00:25:46.120 | - So there's no time, there's no space.
00:25:47.760 | - That's right.
00:25:49.000 | But the thing is that it's just like imagining,
00:25:51.760 | imagine you're just dealing with a graph,
00:25:53.840 | and imagine you have something like a honeycomb graph,
00:25:56.800 | where you have a bunch of hexagons.
00:25:58.800 | That graph, at a microscopic level,
00:26:01.840 | it's just a bunch of nodes connected to other nodes.
00:26:04.160 | But at a macroscopic level,
00:26:05.440 | you say that looks like a honeycomb, you know, lattice.
00:26:09.160 | It looks like a two-dimensional, you know,
00:26:11.520 | manifold of some kind.
00:26:12.880 | It looks like a two-dimensional thing.
00:26:14.760 | If you connect it differently,
00:26:15.840 | if you just connect all the nodes one to another,
00:26:18.560 | in kind of a sort of linked list type structure,
00:26:21.000 | then you'd say, well,
00:26:21.840 | that looks like a one-dimensional space.
00:26:24.200 | But at the microscopic level,
00:26:25.720 | all these are just networks with nodes.
00:26:27.920 | The macroscopic level,
00:26:29.400 | they look like something that's like
00:26:31.120 | one of our sort of familiar kinds of space.
00:26:33.680 | And it's the same thing with these hypergraphs.
00:26:36.280 | Now, if you ask me, have I found one
00:26:38.040 | that gives me three-dimensional space,
00:26:39.680 | the answer is not yet.
00:26:41.320 | So we don't know, you know, this is one of these things,
00:26:43.800 | we're kind of betting against nature, so to speak.
00:26:46.480 | And I have no way to know.
00:26:48.480 | So there are many other properties of this kind of system
00:26:51.920 | that are very beautiful, actually, and very suggestive.
00:26:56.040 | And it will be very elegant if this turns out to be right,
00:26:58.520 | because it's very clean.
00:27:00.200 | I mean, you start with nothing and everything gets built up.
00:27:03.360 | Everything about space, everything about time,
00:27:06.120 | everything about matter,
00:27:07.520 | it's all just emergent from the properties
00:27:10.520 | of this extremely low-level system.
00:27:12.520 | And that will be pretty cool
00:27:14.360 | if that's the way our universe works.
00:27:16.520 | Now, do I, on the other hand,
00:27:18.880 | the thing that I find very confusing is,
00:27:22.880 | let's say we succeed.
00:27:24.440 | Let's say we can say this particular
00:27:28.600 | sort of hypergraph rewriting rule gives the universe.
00:27:32.320 | Just run that hypergraph rewriting rule for enough times,
00:27:35.360 | and you'll get everything.
00:27:36.200 | You'll get this conversation we're having.
00:27:37.880 | You'll get everything.
00:27:39.840 | It's that,
00:27:41.480 | if we get to that point and we look at what is this thing,
00:27:47.240 | what is this rule that we just have
00:27:49.280 | that is giving us our whole universe?
00:27:50.640 | How do we think about that thing?
00:27:52.720 | Let's say, turns out the minimal version of this,
00:27:55.240 | and this is kind of cool thing
00:27:56.880 | for a language designer like me,
00:27:58.600 | the minimal version of this model
00:28:00.560 | is actually a single line of orphan language code.
00:28:03.560 | So that's, which I wasn't sure was gonna happen that way,
00:28:06.280 | but it's, it's, that's, it's kind of, no.
00:28:10.520 | We don't know what, we don't know what,
00:28:12.720 | that's, that's just the framework.
00:28:14.680 | To know the actual particular hypergraph,
00:28:17.240 | it might be a longer,
00:28:18.840 | the specification of the rules might be slightly longer.
00:28:20.760 | - How does that help you accept marveling
00:28:24.200 | in the beauty and the elegance of the simplicity
00:28:26.760 | that creates the universe?
00:28:28.200 | That does that help us predict anything?
00:28:30.320 | Not really, because of the irreducibility.
00:28:32.520 | - That's correct, that's correct.
00:28:34.000 | But so the thing that is really strange to me,
00:28:36.360 | and I haven't wrapped my brain around this yet,
00:28:39.720 | is, you know, one is,
00:28:42.560 | one keeps on realizing that we're not special,
00:28:45.560 | in the sense that, you know,
00:28:47.240 | we don't live at the center of the universe,
00:28:48.880 | we don't blah, blah, blah.
00:28:50.480 | And yet, if we produce a rule for the universe,
00:28:55.080 | and it's quite simple,
00:28:56.400 | and we can write it down in a couple of lines or something,
00:28:59.840 | that feels very special.
00:29:01.560 | How did we come to get a simple universe,
00:29:04.720 | when many of the available universes, so to speak,
00:29:07.560 | are incredibly complicated?
00:29:09.080 | Might be, you know, a quintillion characters long.
00:29:12.400 | Why did we get one of the ones that's simple?
00:29:14.600 | And so I haven't wrapped my brain around that issue yet.
00:29:17.840 | - If indeed we are in such a simple,
00:29:21.040 | the universe is such a simple rule,
00:29:23.160 | is it possible that there is something outside of this,
00:29:27.320 | that we are in a kind of what people call,
00:29:29.960 | so the simulation, right?
00:29:32.080 | That we're just part of a computation
00:29:33.760 | that's being explored by a graduate student
00:29:36.520 | in an alternate universe?
00:29:38.280 | - Well, you know, the problem is,
00:29:40.280 | we don't get to say much about what's outside our universe,
00:29:42.760 | because by definition,
00:29:43.800 | our universe is what we exist within.
00:29:46.680 | Now, can we make a sort of almost theological conclusion
00:29:50.720 | from being able to know how our particular universe works?
00:29:54.380 | Interesting question.
00:29:55.840 | I don't think that, if you ask the question,
00:29:59.120 | could we, and it relates again to this question
00:30:01.680 | about the extraterrestrial intelligence,
00:30:04.160 | you know, we've got the rule for the universe.
00:30:06.620 | Was it built in on purpose?
00:30:08.720 | Hard to say.
00:30:09.840 | That's the same thing as saying,
00:30:11.360 | we see a signal from, you know,
00:30:13.600 | that we're receiving from some random star somewhere,
00:30:18.320 | and it's a series of pulses,
00:30:20.800 | and, you know, it's a periodic series of pulses, let's say.
00:30:23.880 | Was that done on purpose?
00:30:25.080 | Can we conclude something about the origin
00:30:26.880 | of that series of pulses?
00:30:28.320 | - Just because it's elegant does not necessarily mean
00:30:32.040 | that somebody created it,
00:30:34.480 | or that we can even comprehend what would create it.
00:30:36.320 | - Yeah, I mean, I think it's the ultimate version
00:30:39.600 | of the sort of identification
00:30:42.120 | of the technosignature question.
00:30:44.560 | It's the ultimate version of that,
00:30:45.680 | which is, was our universe a piece of technology,
00:30:47.960 | so to speak, and how on earth would we know?
00:30:50.660 | Because, but I mean, it'll be, it's, I mean, you know,
00:30:54.240 | in the kind of crazy science fiction thing
00:30:56.100 | you could imagine, you could say,
00:30:57.960 | oh, somebody's going to have, you know,
00:31:00.040 | there's gonna be a signature there.
00:31:01.260 | It's gonna be, you know, made by so-and-so.
00:31:04.040 | But there's no way we could understand that, so to speak,
00:31:07.120 | and it's not clear what that would mean,
00:31:08.860 | because the universe simply, you know,
00:31:12.760 | this, if we find a rule for the universe,
00:31:16.080 | we're not, we're simply saying that rule
00:31:18.040 | represents what our universe does.
00:31:20.720 | We're not saying that that rule is something
00:31:23.320 | running on a big computer and making our universe.
00:31:26.160 | It's just saying that represents what our universe does,
00:31:29.240 | in the same sense that, you know,
00:31:30.760 | laws of classical mechanics, differential equations,
00:31:33.360 | whatever they are, represent what mechanical systems do.
00:31:37.000 | It's not that the mechanical systems
00:31:39.480 | are somehow running solutions
00:31:41.120 | to those differential equations.
00:31:42.840 | Those differential equations are just representing
00:31:44.920 | the behavior of those systems.
00:31:46.280 | - So what's the gap, in your sense,
00:31:48.360 | to linger on the fascinating,
00:31:50.740 | perhaps slightly sci-fi question?
00:31:52.760 | What's the gap between understanding
00:31:55.280 | the fundamental rules that create a universe
00:31:57.680 | and engineering a system,
00:32:00.640 | actually creating a simulation ourselves?
00:32:02.800 | You've talked about, sort of,
00:32:05.080 | you've talked about, you know,
00:32:07.360 | nanoengineering, kind of ideas that are kind of exciting,
00:32:10.080 | actually creating some ideas of computation
00:32:12.520 | in the physical space.
00:32:13.720 | How hard is it, as an engineering problem,
00:32:16.440 | to create the universe,
00:32:17.440 | once you know the rules that create it?
00:32:19.520 | - Well, that's an interesting question.
00:32:20.920 | I think the substrate on which the universe is operating
00:32:24.400 | is not a substrate that we have access to.
00:32:26.660 | I mean, the only substrate we have
00:32:28.680 | is that same substrate that the universe is operating in.
00:32:31.960 | So, if the universe is a bunch of hypergraphs
00:32:34.020 | being rewritten, then we get to attach ourselves
00:32:37.420 | to those same hypergraphs being rewritten.
00:32:39.960 | We don't get to,
00:32:41.360 | and if you ask the question, you know,
00:32:44.600 | is the code clean?
00:32:46.240 | You know, can we write nice, elegant code
00:32:48.600 | with efficient algorithms and so on?
00:32:50.600 | Well, that's an interesting question.
00:32:53.440 | How, you know, that's this question
00:32:55.440 | of how much computational reducibility
00:32:57.280 | there is in the system.
00:32:58.600 | - But, so I've seen some beautiful cellular automata
00:33:00.920 | that basically create copies of itself within itself, right?
00:33:04.080 | So, that's the question, whether it's possible to create,
00:33:07.600 | like, whether you need to understand the substrate
00:33:09.800 | or whether you can just--
00:33:11.560 | - Yeah, well, right.
00:33:12.400 | I mean, so one of the things that is
00:33:14.240 | sort of one of my slightly sci-fi thoughts
00:33:16.960 | about the future, so to speak, is, you know,
00:33:19.800 | right now, if you poll typical people, you say,
00:33:22.280 | "Do you think it's important to find
00:33:23.320 | "the fundamental theory of physics?"
00:33:25.580 | You get, because I've done this poll, informally at least,
00:33:29.320 | it's curious, actually.
00:33:30.640 | You get a decent fraction of people saying,
00:33:32.500 | "Oh, yeah, that would be pretty interesting."
00:33:34.840 | - I think that's becoming, surprisingly enough, more,
00:33:38.360 | I mean, a lot of people are interested in physics
00:33:43.080 | in a way that, like, without understanding it,
00:33:44.920 | just kind of watching scientists,
00:33:49.120 | a very small number of them, struggle to understand
00:33:51.880 | the nature of our reality.
00:33:53.160 | - Right, I mean, I think that's somewhat true,
00:33:55.400 | and in fact, in this project that I'm launching into
00:33:58.680 | to try and find the fundamental theory of physics,
00:34:01.200 | I'm going to do it as a very public project.
00:34:03.040 | I mean, it's gonna be live-streamed
00:34:04.800 | and all this kind of stuff, and I don't know
00:34:06.560 | what will happen, it'll be kind of fun.
00:34:08.560 | I mean, I think that it's the interface
00:34:11.520 | to the world of this project.
00:34:14.120 | I mean, I figure one feature of this project is,
00:34:18.000 | you know, unlike technology projects
00:34:20.240 | that basically are what they are,
00:34:21.980 | this is a project that might simply fail,
00:34:23.920 | because it might be the case that it generates
00:34:25.500 | all kinds of elegant mathematics,
00:34:27.200 | but it has absolutely nothing to do
00:34:28.440 | with the physical universe that we happen to live in.
00:34:30.880 | Well, okay, so we're talking about
00:34:33.760 | kind of the quest to find the fundamental theory of physics.
00:34:36.920 | First point is, you know, it's turned out
00:34:39.960 | it's kind of hard to find the fundamental theory of physics.
00:34:42.080 | People weren't sure that that would be the case.
00:34:44.440 | Back in the early days of applying mathematics to science,
00:34:48.720 | 1600s and so on, people were like,
00:34:50.840 | "Oh, in 100 years, we'll know everything there is to know
00:34:53.720 | "about how the universe works."
00:34:54.960 | Turned out to be harder than that,
00:34:56.520 | and people got kind of humble at some level,
00:34:58.800 | 'cause every time we got to sort of a greater level
00:35:01.000 | of smallness in studying the universe,
00:35:03.080 | it seemed like the math got more complicated
00:35:05.080 | and everything got harder.
00:35:06.920 | When I was a kid, basically,
00:35:11.720 | I started doing particle physics,
00:35:13.600 | and when I was doing particle physics,
00:35:16.800 | I always thought finding the fundamental,
00:35:19.360 | fundamental theory of physics,
00:35:21.120 | that's a kooky business, we'll never be able to do that.
00:35:24.240 | But we can operate within these frameworks that we built
00:35:27.200 | for doing quantum field theory and general relativity
00:35:29.280 | and things like this, and it's all good,
00:35:31.160 | and we can figure out a lot of stuff.
00:35:33.400 | - Did you even at that time have a sense
00:35:35.040 | that there's something behind that too?
00:35:37.480 | - Sure, I just didn't expect that.
00:35:39.400 | I thought in some rather un,
00:35:42.800 | it's actually kind of crazy thinking back on it,
00:35:45.560 | because it's kind of like there was this long period
00:35:48.520 | in civilization where people thought the ancients
00:35:50.360 | had it all figured out and will never figure out
00:35:52.000 | anything new.
00:35:53.240 | And to some extent, that's the way I felt about physics
00:35:56.480 | when I was in the middle of doing it, so to speak,
00:35:59.240 | was we've got quantum field theory,
00:36:01.600 | it's the foundation of what we're doing,
00:36:03.560 | and yes, there's probably something underneath this,
00:36:06.880 | but we'll sort of never figure it out.
00:36:09.640 | But then I started studying simple programs
00:36:12.920 | in the computational universe,
00:36:14.680 | things like cellular automata and so on,
00:36:16.880 | and I discovered that they do all kinds of things
00:36:20.320 | that were completely at odds with the intuition
00:36:22.760 | that I had had.
00:36:23.920 | And so after that, after you see this tiny little program
00:36:27.740 | that does all this amazingly complicated stuff,
00:36:30.280 | then you start feeling a bit more ambitious about physics
00:36:33.240 | and saying, maybe we could do this for physics too.
00:36:36.000 | And so that got me started years ago now
00:36:39.780 | in this kind of idea of could we actually find
00:36:44.160 | what's underneath all of these frameworks
00:36:46.440 | like quantum field theory and general relativity and so on.
00:36:48.240 | And people perhaps don't realize as clearly as they might
00:36:51.520 | that the frameworks we're using for physics,
00:36:53.680 | which is basically these two things,
00:36:54.960 | quantum field theory, sort of the theory of small stuff
00:36:59.520 | and general relativity, theory of gravitation
00:37:01.760 | and large stuff, those are the two basic theories,
00:37:04.420 | and they're 100 years old.
00:37:05.840 | I mean, general relativity was 1915,
00:37:08.280 | quantum field theory, well, 1920s.
00:37:11.120 | So basically 100 years old.
00:37:12.960 | And it's been a good run.
00:37:15.800 | There's a lot of stuff been figured out.
00:37:17.740 | But what's interesting is the foundations haven't changed
00:37:21.680 | in all that period of time.
00:37:23.360 | Even though the foundations had changed several times
00:37:25.760 | before that in the 200 years earlier than that.
00:37:28.460 | And I think the kinds of things that I'm thinking about,
00:37:32.360 | which are sort of really informed by thinking
00:37:34.360 | about computation and the computational universe,
00:37:36.880 | it's a different foundation.
00:37:38.480 | It's a different set of foundations and might be wrong,
00:37:42.400 | but it is at least, we have a shot.
00:37:45.680 | And I think it's, to me, it's,
00:37:48.520 | my personal calculation for myself is,
00:37:51.360 | is, you know, if it turns out that the finding
00:37:55.840 | the fundamental theory of physics,
00:37:57.160 | it's kind of low hanging fruit, so to speak,
00:37:59.600 | it'd be a shame if we just didn't think to do it.
00:38:02.160 | You know, if people just said,
00:38:04.080 | oh, you'll never figure that stuff out.
00:38:05.640 | Let's, you know, and it takes another 200 years
00:38:08.280 | before anybody gets around to doing it.
00:38:11.720 | You know, I think it's, I don't know how low hanging
00:38:15.560 | this fruit actually is.
00:38:16.600 | It may be, you know, it may be that it's kind
00:38:19.920 | of the wrong century to do this project.
00:38:21.840 | I mean, I think the cautionary tale for me, you know,
00:38:25.520 | I think about things that I've tried to do in technology
00:38:28.560 | where people thought about doing them a lot earlier.
00:38:32.160 | And my favorite example is probably Leibniz
00:38:34.560 | who thought about making essentially encapsulating
00:38:38.360 | the world's knowledge in a computational form
00:38:41.280 | in the late 1600s and did a lot of things towards that.
00:38:45.600 | And basically, you know, we finally managed to do this,
00:38:48.680 | but he was 300 years too early.
00:38:50.560 | And that's kind of the, in terms of life planning,
00:38:54.100 | it's kind of like avoid things that can't be done
00:38:56.640 | in your century, so to speak.
00:38:59.040 | - Yeah, timing, timing is everything.
00:39:02.200 | So you think if we kind of figure out the underlying rules
00:39:07.200 | it can create from which quantum field theory
00:39:11.360 | and general relativity can emerge,
00:39:13.540 | do you think that'll help us unify it
00:39:15.160 | at that level of abstraction?
00:39:16.320 | - Oh, we'll know it completely.
00:39:17.400 | We'll know how that all fits together.
00:39:19.080 | Yes, without a question.
00:39:20.800 | And I mean, it's already, even the things I've already done,
00:39:25.800 | there are very, you know, it's very, very elegant actually,
00:39:30.000 | how things seem to be fitting together.
00:39:31.920 | Now, you know, is it right?
00:39:33.040 | I don't know yet.
00:39:33.960 | It's awfully suggestive.
00:39:36.320 | If it isn't right, it's then the designer of the universe
00:39:40.720 | should feel embarrassed, so to speak,
00:39:42.120 | 'cause it's a really good way to do it.
00:39:43.920 | - And your intuition in terms of design universe,
00:39:46.620 | does God play dice?
00:39:48.400 | Is there randomness in this thing, or is it deterministic?
00:39:53.200 | So the kind of--
00:39:54.040 | - That's a little bit of a complicated question
00:39:55.800 | because when you're dealing with these things
00:39:58.220 | that involve these rewrites that have, okay.
00:40:00.760 | - Even randomness is an emergent phenomenon perhaps?
00:40:03.240 | - Yes, yes.
00:40:04.320 | I mean, it's a, yeah, well, randomness,
00:40:06.240 | in many of these systems, pseudo-randomness and randomness
00:40:09.880 | are hard to distinguish.
00:40:11.840 | In this particular case, the current idea that we have
00:40:14.840 | about measurement and quantum mechanics
00:40:17.840 | is something very bizarre and very abstract,
00:40:21.960 | and I don't think I can yet explain it
00:40:25.120 | without kind of yakking about very technical things.
00:40:28.360 | Eventually I will be able to, but if that's right,
00:40:32.920 | it's kind of a, it's a weird thing
00:40:34.720 | because it slices between determinism and randomness
00:40:39.220 | in a weird way that hasn't been sliced before, so to speak.
00:40:42.140 | So like many of these questions that come up in science
00:40:45.120 | where it's like, is it this or is it that?
00:40:47.660 | Turns out the real answer is it's neither of those things.
00:40:50.040 | It's something kind of different
00:40:51.540 | and sort of orthogonal to those categories.
00:40:55.860 | And so that's the current, you know,
00:40:58.020 | this week's idea about how that might work.
00:41:01.120 | But, you know, we'll see how that unfolds.
00:41:05.780 | I mean, there's this question about a field like physics
00:41:09.180 | and sort of the quest for fundamental theory and so on.
00:41:12.420 | And there's both the science of what happens
00:41:14.860 | and there's the sort of the social aspect of what happens
00:41:18.380 | because, you know, in a field that is basically
00:41:21.700 | as old as physics, we're at, I don't know what it is,
00:41:25.060 | fourth generation, I don't know, fifth generation,
00:41:26.860 | I don't know what generation it is of physicists.
00:41:29.540 | And like, I was one of these, so to speak.
00:41:31.580 | And for me, the foundations were like the pyramids,
00:41:34.940 | so to speak, you know, it was that way
00:41:36.880 | and it was always that way.
00:41:39.220 | It is difficult in an old field to go back
00:41:42.180 | to the foundations and think about rewriting them.
00:41:44.920 | It's a lot easier in young fields
00:41:46.780 | where you're still dealing with the first generation
00:41:49.340 | of people who invented the field.
00:41:51.000 | And it tends to be the case, you know,
00:41:53.460 | that the nature of what happens in science tends to be,
00:41:56.740 | you know, you'll get, typically the pattern
00:41:59.260 | is some methodological advance occurs.
00:42:02.400 | And then there's a period of five years, 10 years,
00:42:04.520 | maybe a little bit longer than that,
00:42:06.260 | where there's lots of things that are now made possible
00:42:08.860 | by that methodological advance, whether it's, you know,
00:42:12.580 | I don't know, telescopes or whether that's
00:42:14.420 | some mathematical method or something.
00:42:16.740 | It's, you know, there's a, something happens,
00:42:21.740 | a tool gets built, and then you can do a bunch of stuff.
00:42:25.580 | And there's a bunch of low-hanging fruit to be picked.
00:42:28.600 | And that takes a certain amount of time.
00:42:30.980 | After that, all that low-hanging fruit is picked,
00:42:33.980 | then it's a hard slog for the next however many decades
00:42:38.180 | or century or more to get to the next sort of level
00:42:42.620 | at which one can do something.
00:42:43.660 | And it's kind of a, and it tends to be the case
00:42:46.420 | that in fields that are in that kind of,
00:42:48.460 | I wouldn't say cruise mode, 'cause it's really hard work,
00:42:51.140 | but it's very hard work for very incremental progress.
00:42:54.260 | (laughing)
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