Frank Wilczek: Physics of Quarks, Dark Matter, Complexity, Life & Aliens

00:00:00.000 | The following is a conversation with Frank Wolchek,

00:00:02.800 | a theoretical physicist at MIT,

00:00:04.920 | who won the Nobel Prize for the co-discovery

00:00:08.100 | of asymptotic freedom in the theory of strong interaction.

00:00:12.160 | Quick mention of our sponsors,

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00:00:20.440 | Check them out in the description to support this podcast.

00:00:23.600 | As a side note, let me say a word about asymptotic freedom.

00:00:26.920 | Protons and neutrons make up the nucleus of an atom.

00:00:30.020 | Strong interaction is responsible

00:00:31.840 | for the strong nuclear force that binds them.

00:00:34.200 | But strong interaction also holds together the quarks

00:00:37.720 | that make up the protons and neutrons.

00:00:40.060 | Frank Wolchek, David Gross, and David Pulitzer

00:00:43.280 | came up with a theory postulating

00:00:45.320 | that when quarks come really close to one another,

00:00:48.080 | the attraction abates and they behave like free particles.

00:00:51.480 | This is called asymptotic freedom.

00:00:54.460 | This happens at very, very high energies,

00:00:57.900 | which is also where all the fun is.

00:01:00.680 | This is the Lex Friedman Podcast,

00:01:02.920 | and here is my conversation with Frank Wolchek.

00:01:06.580 | What is the most beautiful idea in physics?

00:01:11.000 | - The most beautiful idea in physics

00:01:13.560 | is that we can get a compact description of the world

00:01:18.560 | that's very precise and very full

00:01:24.080 | at the level of the operating system of the world.

00:01:26.880 | That's an extraordinary gift,

00:01:32.120 | and we get worried when we find discrepancies

00:01:37.120 | between our description of the world

00:01:41.080 | and what's actually observed

00:01:42.800 | at the level even of a part in a billion.

00:01:46.800 | - You actually have this quote from Einstein

00:01:49.440 | that the most incomprehensible thing

00:01:51.880 | about the universe is that it is comprehensible,

00:01:54.920 | something like that.

00:01:55.760 | - Yes, so that's the most beautiful surprise

00:01:58.320 | that I think that really was, to me,

00:02:03.200 | the most profound result of the scientific revolution

00:02:06.560 | of the 17th century with the shining example

00:02:11.560 | of Newtonian physics that you could aspire

00:02:14.800 | to completeness, precision, and a concise description

00:02:19.480 | of the world, of the operating system.

00:02:21.400 | And it's gotten better and better over the years,

00:02:25.280 | and that's the continuing miracle.

00:02:27.940 | Now, there are a lot of beautiful sub-miracles, too.

00:02:30.880 | The form of the equations is governed

00:02:33.600 | by high degrees of symmetry,

00:02:35.760 | and they have a very surprising kind

00:02:39.000 | of mind-expanding structure,

00:02:40.800 | especially in quantum mechanics.

00:02:42.920 | But if I had to say the single most beautiful revelation

00:02:48.360 | is that, in fact, the world is comprehensible.

00:02:53.360 | - Would you say that's a fact or a hope?

00:02:56.440 | - It's a fact. (laughs)

00:02:58.120 | We can do, you can point to things like the rise

00:03:03.120 | of gross national products per capita around the world

00:03:09.360 | as a result of the scientific revolution.

00:03:14.180 | You can see it all around you.

00:03:18.080 | In recent developments with exponential production

00:03:21.400 | of wealth, control of nature at a very profound level

00:03:26.400 | where we do things like sense tiny, tiny, tiny,

00:03:31.440 | tiny vibrations to tell that there are black holes

00:03:35.540 | colliding far away, or we test laws, as I alluded to,

00:03:40.540 | as a part in a billion, and do things

00:03:45.400 | in what appear on the surface

00:03:47.640 | to be entirely different conceptual universes.

00:03:49.800 | I mean, on the one hand, pencil and paper

00:03:52.040 | are nowadays computers that calculate abstractions,

00:03:55.520 | and on the other hand, magnets and accelerators

00:03:58.640 | and detectors that look at the behavior

00:04:00.840 | of fundamental particles,

00:04:02.000 | and these different universes have to agree,

00:04:06.640 | or else we get very upset.

00:04:08.200 | And that's an amazing thing if you think about it.

00:04:12.200 | And it's telling us that we do understand a lot

00:04:17.200 | about nature at a very profound level.

00:04:20.580 | And there are still things we don't understand, of course,

00:04:25.520 | but as we get better and better answers

00:04:28.960 | and better and better ability to address

00:04:31.680 | difficult questions, we can ask more

00:04:33.960 | and more ambitious questions.

00:04:35.560 | - Well, I guess the hope part of that

00:04:37.760 | is because we are surrounded by mystery.

00:04:40.280 | So we've, one way to say it,

00:04:42.480 | if you look at the growth, the GDP,

00:04:45.040 | over time that we figured out quite a lot,

00:04:47.200 | and we're able to improve the quality of life

00:04:50.320 | because of that, and we've figured out

00:04:52.200 | some fundamental things about this universe,

00:04:54.360 | but we still don't know how much mystery there is.

00:04:57.400 | And it's also possible that there's some things

00:05:00.520 | that are, in fact, incomprehensible

00:05:03.360 | to both our minds and the tools of science.

00:05:07.400 | Like we, the sad thing is we may not know it

00:05:11.600 | because, in fact, they are incomprehensible.

00:05:14.320 | And that's the open question is

00:05:16.000 | how much of the universe is comprehensible?

00:05:18.200 | If we figured out the everything,

00:05:21.880 | what's inside the black hole,

00:05:23.480 | and everything that happened at the moment of the Big Bang,

00:05:26.760 | does that still give us the key

00:05:28.880 | to understanding the human mind

00:05:30.760 | and the emergence of all the beautiful complexity

00:05:33.880 | we see around us?

00:05:35.020 | That's not, like when I see these objects,

00:05:38.120 | like I don't know if you've seen them,

00:05:39.560 | like cellular automata, all these kinds of objects

00:05:43.320 | where from simple rules emerges complexity,

00:05:46.940 | it makes you wonder maybe it's not reducible

00:05:50.080 | to simple, beautiful equations, the whole thing,

00:05:53.280 | only parts of it.

00:05:54.900 | That's the tension I was getting at with the hope.

00:05:57.680 | - Well, when we say the universe is comprehensible,

00:06:00.240 | we have to kind of draw careful distinctions

00:06:04.940 | about, or definitions about what we mean by that.

00:06:09.940 | - Both the universe and the comprehensibility.

00:06:15.240 | - Exactly, right.

00:06:16.400 | So in certain areas of understanding reality,

00:06:21.400 | we've made extraordinary progress, I would say,

00:06:29.040 | in understanding fundamental physical processes

00:06:32.520 | and getting very precise equations

00:06:34.680 | that really work and allow us to do

00:06:37.480 | profound sculpting of matter,

00:06:40.520 | to make computers and iPhones and everything else,

00:06:43.240 | and they really work,

00:06:44.120 | and they're extraordinary productions.

00:06:46.020 | And that's all based on the laws of quantum mechanics,

00:06:53.200 | and they really work,

00:06:55.640 | and they give us tremendous control of nature.

00:07:00.800 | On the other hand, as we get better answers,

00:07:04.800 | we can also ask more ambitious questions,

00:07:07.240 | and there are certainly things that have been observed,

00:07:11.160 | even in what would be usually called the realm of physics

00:07:15.320 | that aren't understood.

00:07:16.920 | For instance, there seems to be another source of mass

00:07:21.120 | in the universe, the so-called dark matter,

00:07:23.640 | that we don't know what it is,

00:07:25.080 | and it's a very interesting question what it is.

00:07:30.360 | But also, as you were alluding to,

00:07:33.320 | it's one thing to know the basic equations,

00:07:36.680 | it's another thing to be able to solve them

00:07:39.880 | in important cases.

00:07:42.200 | So we run up against the limits of that

00:07:45.440 | in things like chemistry,

00:07:46.980 | where we'd like to be able to design molecules

00:07:49.680 | and predict their behavior from the equations.

00:07:52.220 | We think the equations could do that in principle,

00:07:55.240 | but in practice, it's very challenging to solve them

00:08:00.480 | in all but very simple cases.

00:08:02.640 | And then there's the other thing,

00:08:06.320 | which is that a lot of what we're interested in

00:08:08.740 | is historically conditioned.

00:08:11.480 | It's not a matter of the fundamental equations,

00:08:15.420 | but about what has evolved or come out

00:08:19.920 | of the early universe and formed into people and frogs

00:08:23.600 | and societies and things.

00:08:25.240 | And the basic laws of physics only take you so far

00:08:30.120 | in that it kind of provides a foundation,

00:08:32.660 | but you need entirely different concepts

00:08:35.720 | to deal with those kind of systems.

00:08:39.740 | And one thing I can say about that

00:08:44.740 | is that the laws themselves point out their limitations,

00:08:48.880 | that they're laws for dynamical evolution.

00:08:53.340 | So they tell you what happens

00:08:55.080 | if you have a certain starting point,

00:08:56.660 | but they don't tell you what the starting point should be,

00:08:59.760 | at least, yeah.

00:09:01.680 | And the other thing that emerges

00:09:04.960 | from the equations themselves is the phenomena of chaos

00:09:09.960 | and sensitivity to initial conditions,

00:09:15.080 | which tells us that there are intrinsic limitations

00:09:20.080 | on how well we can spell out the consequences of the laws

00:09:25.200 | if we try to apply them.

00:09:26.320 | - It's the old apple pie.

00:09:27.480 | If you wanna, what is it, make an apple pie from scratch,

00:09:31.400 | you have to build the universe or something like that.

00:09:34.280 | - Well, you're much better off starting with apples

00:09:37.280 | than starting with quarks, let's put it that way.

00:09:39.800 | - In your book, "A Beautiful Question,"

00:09:41.680 | you ask, "Does the world embody beautiful ideas?"

00:09:44.920 | So the book is centered around this

00:09:47.240 | very interesting question.

00:09:48.760 | It's like Shakespeare.

00:09:49.600 | You can dig in and read into all the different

00:09:51.720 | interpretations of this question.

00:09:53.480 | But at the high level, what to use the connection

00:09:56.920 | between beauty of the world and physics of the world?

00:10:01.920 | - In a sense, we now have a lot of insight

00:10:04.880 | into what the laws are, the form they take

00:10:07.880 | that allow us to understand matter in great depth

00:10:12.240 | and control it, as we've discussed.

00:10:15.500 | And it's an extraordinary thing how mathematically ideal

00:10:21.600 | those equations turn out to be.

00:10:26.620 | In the early days of Greek philosophy,

00:10:29.680 | Plato had this model of atoms built out of the five

00:10:35.800 | perfectly symmetrical platonic solids.

00:10:38.040 | So there was somehow the idea that mathematical symmetry

00:10:42.320 | should govern the world.

00:10:43.960 | And we've out-Platoed Plato by far in modern physics

00:10:48.960 | because we have symmetries that are much more extensive,

00:10:52.280 | much more powerful, that turn out to be the ingredients

00:10:56.700 | out of which we construct our theory of the world.

00:10:59.140 | And it works.

00:11:00.260 | So that's certainly beautiful.

00:11:06.780 | So the idea of symmetry, which is a driving inspiration

00:11:11.780 | in much of human art, especially decorative art,

00:11:18.780 | like the Alhambra or in wallpaper designs

00:11:21.960 | or things you see around you everywhere,

00:11:23.960 | also turns out to be the dominant theme

00:11:27.980 | in modern fundamental physics,

00:11:30.440 | symmetry and its manifestations.

00:11:32.520 | The laws turn out to be very,

00:11:34.480 | to have these tremendous amounts of symmetry.

00:11:36.520 | You can change the symbols and move them around

00:11:38.880 | in different ways and they still have the same consequences.

00:11:45.120 | So that's beautiful.

00:11:48.500 | These concepts that humans find appealing

00:12:00.540 | also turn out to be the concepts

00:12:03.180 | that govern how the world actually works.

00:12:05.620 | I don't think that's an accident.

00:12:09.060 | I think humans were evolved to be able to interact

00:12:13.660 | with the world in ways that are advantageous

00:12:17.720 | and to learn from it.

00:12:19.200 | And so we are naturally evolved or designed

00:12:22.160 | to enjoy beauty and to symmetry and the world has it.

00:12:26.880 | And that's why we resonate with it.

00:12:31.040 | - Well, it's interesting that the ideas of symmetry

00:12:33.160 | emerge at many levels of the hierarchy of the universe.

00:12:38.160 | So you're talking about particles,

00:12:42.760 | but it also is at the level of chemistry and biology

00:12:47.280 | and the fact that our cognitive,

00:12:52.280 | sort of our perception system and whatever our cognition is

00:12:57.700 | also finds it appealing.

00:13:00.500 | Or somehow our sense of what is beautiful

00:13:02.980 | is grounded in this idea of symmetry

00:13:05.180 | or the breaking of symmetry.

00:13:06.760 | Symmetry is at the core of our conception of beauty,

00:13:09.500 | whether it's the breaking

00:13:10.540 | or the non-breaking of the symmetry.

00:13:12.980 | It makes you wonder why, why?

00:13:17.980 | Like, so I come from Russia and the question of Dostoevsky,

00:13:23.740 | he has said that beauty will save the world.

00:13:27.020 | Maybe as a physicist you can tell me

00:13:29.540 | what do you think he meant by that?

00:13:31.380 | - I don't know if it saves the world,

00:13:32.980 | but it does turn out to be a tremendous source

00:13:35.700 | of insight into the world.

00:13:37.500 | When we investigate kind of the most fundamental

00:13:42.500 | interactions, things that are hard to access

00:13:46.100 | because they occur at very short distances

00:13:48.460 | between very special kinds of particles

00:13:53.460 | whose properties are only revealed at high energies,

00:13:59.020 | we don't have much to go on from everyday life.

00:14:03.940 | But so we have, when we guess what the,

00:14:06.060 | and the experiments are difficult to do,

00:14:08.620 | so you can't really follow a very wholly empirical procedure

00:14:13.620 | to sort of in the Baconian style figure out the laws

00:14:19.740 | kind of step by step just by accumulating a lot of data.

00:14:23.180 | What we actually do is guess.

00:14:25.940 | And the guesses are kind of aesthetic, really.

00:14:29.400 | What would be a nice description

00:14:31.500 | that's consistent with what we know?

00:14:34.140 | And then you try it out and see if it works.

00:14:36.260 | And by gosh, it does in many profound cases.

00:14:41.260 | So there's that, but there's another source of symmetry

00:14:46.060 | which I didn't talk so much about in A Beautiful Question,

00:14:51.060 | but does relate to your comments.

00:14:56.840 | And I think very much relates to the source of symmetry

00:15:01.960 | that we find in biology and in our heads, in our brain,

00:15:06.960 | which is that, although, well,

00:15:14.340 | it is discussed a bit in A Beautiful Question

00:15:18.100 | and also in fundamentals, is that when you have,

00:15:23.100 | symmetry is also a very important means of construction.

00:15:30.300 | So when you have, for instance, simple viruses

00:15:34.500 | that need to construct their coat, their protein coat,

00:15:39.340 | the coats often take the form of platonic solids.

00:15:42.220 | And the reason is that the viruses are really dumb

00:15:47.060 | and they only know how to do one thing.

00:15:48.980 | So they make a pentagon, then they make another pentagon,

00:15:51.580 | and they make another pentagon,

00:15:52.580 | and they all glue together in the same way.

00:15:55.380 | And that makes a very symmetrical object.

00:15:58.940 | So the rules of development, when you have simple rules

00:16:02.060 | and they work again and again, you get symmetrical patterns.

00:16:07.060 | That's kind of, in fact, it's a recipe also

00:16:09.740 | for generating fractals, like the kind of broccoli

00:16:14.740 | that has all this internal structure.

00:16:19.340 | And I wish I had a picture to show,

00:16:20.740 | but maybe people remember it from the supermarket.

00:16:27.540 | And you say, how did a vegetable get so intelligent

00:16:30.020 | to make such a beautiful object

00:16:31.620 | with all this fractal structure?

00:16:33.500 | And the secret is stupidity.

00:16:35.940 | You just do the same thing over and over again.

00:16:38.580 | And in our brains also, we came out,

00:16:43.120 | we start from single cells and they reproduce,

00:16:47.480 | and each one does roughly the same thing.

00:16:51.860 | The program evolves in time, of course,

00:16:56.780 | different modules get turned on and off,

00:17:01.060 | genetic, different regions of the genetic code

00:17:03.460 | get turned on and off.

00:17:04.780 | But basically, a lot of the same things are going on,

00:17:08.780 | and they're simple things,

00:17:09.740 | and so you produce the same patterns over and over again,

00:17:12.460 | and that's a recipe for producing symmetry,

00:17:14.540 | 'cause you're getting the same thing in many, many places.

00:17:17.140 | And if you look at, for instance,

00:17:20.860 | the beautiful drawings of Rahman Iqbal,

00:17:24.860 | the great neuroanatomist who drew the structure

00:17:29.220 | of different organs like the hippocampus,

00:17:33.380 | you see it's very regular and very intricate,

00:17:37.820 | and it's symmetry in that sense.

00:17:42.820 | It's 'cause it's many repeated units

00:17:46.860 | that you can take from one place to the other

00:17:49.580 | and see that they look more or less the same.

00:17:51.860 | - But when you're describing this kind of beauty

00:17:54.300 | that we're talking about now,

00:17:55.540 | it's a very small sample in terms of space-time

00:18:00.540 | in a very big world,

00:18:01.940 | in a very short, brief moment in this long history.

00:18:08.020 | In your book, "Fundamentals, 10 Keys to Reality,"

00:18:11.420 | I'd really recommend people read it,

00:18:13.460 | you say that space and time are pretty big, or very big.

00:18:20.340 | How big are we talking about?

00:18:23.740 | Can you tell a brief history of space and time?

00:18:28.020 | - It's easy to tell a brief history

00:18:30.020 | if the details get very involved, of course.

00:18:33.380 | But one thing I like to say is that

00:18:35.500 | if you take a broad enough view,

00:18:38.460 | the history of the universe is simpler

00:18:40.140 | than the history of Sweden, say.

00:18:41.740 | Because your standards are lower.

00:18:45.220 | But just to make it quantitative,

00:18:50.900 | I'll just give a few highlights.

00:18:52.700 | And it's a little bit easier to talk about time,

00:18:57.460 | so let's start with that.

00:18:59.220 | The Big Bang occurred, we think,

00:19:02.020 | the universe was much hotter and denser and more uniform

00:19:05.740 | about 13.8 billion years ago,

00:19:09.020 | and that's what we call the Big Bang.

00:19:10.860 | And it's been expanding and cooling,

00:19:14.420 | the matter in it has been expanding and cooling ever since.

00:19:18.060 | So in a real sense, the universe is 13.8 billion years old.

00:19:22.620 | That's a big number, kind of hard to think about.

00:19:26.580 | A nice way to think about it, though,

00:19:28.460 | is to map it onto one year.

00:19:31.460 | So let's say the universe,

00:19:33.940 | just linearly map the time intervals

00:19:36.100 | from 13.8 billion years onto one year.

00:19:39.940 | So the Big Bang then is on January 1st at 12 a.m.

00:19:44.940 | And you wait for quite a long time

00:19:52.260 | before the dinosaurs emerge.

00:19:53.900 | The dinosaurs emerge on Christmas, it turns out.

00:19:57.060 | - 12 months, almost 12 months later.

00:20:00.180 | - Getting close to the end, yes.

00:20:01.900 | - Getting close to the end.

00:20:03.540 | - And the extinction event that let the mammals

00:20:07.960 | and ultimately humans inherit the Earth

00:20:11.180 | from the dinosaurs occurred on December 30th.

00:20:15.660 | And all of human history is a small part of the last day.

00:20:20.820 | And so yes, so we're occupying only,

00:20:25.820 | and a human lifetime is a very, very infinitesimal part

00:20:29.340 | of this interval, of these gigantic cosmic reaches of time.

00:20:34.340 | And in space, we can tell a very similar story.

00:20:41.780 | In fact, it's convenient to think

00:20:45.780 | that the size of the universe is the distance

00:20:49.660 | that light can travel in 13.8 billion years.

00:20:52.780 | That's so 13.8 billion light years.

00:20:56.580 | That's how far you can see out.

00:20:59.180 | That's how far signals can reach us.

00:21:03.620 | And that is a big distance,

00:21:08.620 | because compared to that, the Earth

00:21:14.740 | is a fraction of a light second.

00:21:18.140 | So again, it's really, really big.

00:21:21.540 | And so we have, if we wanna think about the universe

00:21:26.540 | as a whole in space and time,

00:21:29.360 | we really need a different kind of imagination.

00:21:35.020 | It's not something you can grasp

00:21:38.660 | in terms of psychological time.

00:21:43.620 | In a useful way, you have to think,

00:21:45.500 | you have to use exponential notation and abstract concepts

00:21:48.700 | to really get any hold on these vast times and spaces.

00:21:53.700 | On the other hand, let me hasten to add

00:21:58.100 | that that doesn't make us small,

00:22:00.520 | or make the time that we have to us small,

00:22:06.580 | because again, looking at those pictures

00:22:10.660 | of what our minds are, and some of the components

00:22:15.480 | of our minds, these beautiful drawings

00:22:18.620 | of the cellular patterns inside the brain,

00:22:21.180 | you see that there are many, many, many processing units.

00:22:24.820 | And if you analyze how fast they operate,

00:22:29.740 | I try to estimate how many thoughts

00:22:31.660 | a person can have in a lifetime.

00:22:33.340 | That's kind of a fuzzy question,

00:22:34.740 | but I'm very proud that I was able

00:22:36.740 | to define it pretty precisely.

00:22:39.460 | And it turns out we have time for billions

00:22:43.620 | of meaningful thoughts in a lifetime.

00:22:46.980 | So it's a lot.

00:22:48.540 | We shouldn't think of ourselves as terribly small,

00:22:51.840 | either in space or in time, because although we're small

00:22:56.280 | in those dimensions compared to the universe,

00:22:59.200 | we're large compared to meaningful units

00:23:03.760 | of processing information and being able

00:23:08.080 | to conceptualize and understand things.

00:23:11.620 | - Yeah, but 99% of those thoughts are probably food,

00:23:15.120 | sex, or internet-related.

00:23:16.840 | - Well, yeah, well, yeah, well, they're not necessarily.

00:23:20.540 | - Only like 0.1 is Nobel Prize-winning ideas.

00:23:24.100 | - That's true, but there's more to life

00:23:26.460 | than winning Nobel Prizes.

00:23:27.740 | - How did you do that calculation?

00:23:29.860 | Can you maybe break that apart a little bit,

00:23:31.380 | just kind of for fun, sort of an intuition

00:23:34.020 | of how we calculate the number of thoughts?

00:23:35.940 | - The number of thoughts, right.

00:23:38.180 | It's necessarily imprecise, because a lot

00:23:40.540 | of things are going on in different ways.

00:23:42.100 | What is a thought?

00:23:43.260 | But there are several things that point

00:23:45.900 | to more or less the same rate of being able

00:23:50.900 | to have meaningful thoughts.

00:23:52.700 | For instance, the one that I think

00:23:56.760 | is maybe the most penetrating is how fast

00:24:01.380 | we can process visual images.

00:24:04.380 | How do we do that?

00:24:07.820 | If you've ever watched old movies,

00:24:11.340 | you can see that, well, any movie, in fact,

00:24:15.140 | that a motion picture is really not a motion picture.

00:24:18.060 | It's a series of snapshots that are playing

00:24:20.540 | one after the other.

00:24:21.900 | And it's because our brains also work that way.

00:24:26.520 | We take snapshots of the world,

00:24:28.500 | integrate over a certain time,

00:24:29.940 | and then go on to the next one.

00:24:31.120 | And then by post-processing, create the illusion

00:24:34.580 | of continuity and flow, we can deal with that.

00:24:38.380 | And if the flicker rate is too slow,

00:24:43.380 | then you start to see that it's a series of snapshots.

00:24:48.660 | And you can ask, what is the crossover?

00:24:51.060 | When does it change from being something

00:24:53.100 | that is matched to our processing speed versus too fast?

00:24:57.460 | And it turns out about 40 per second.

00:25:00.460 | And then if you take 40 per second

00:25:03.060 | as how fast we can process visual images,

00:25:06.860 | you get to several billions of thoughts.

00:25:09.420 | If you, similarly, if you ask,

00:25:13.780 | what are some of the fastest things that people can do?

00:25:16.940 | Well, they can play video games,

00:25:18.660 | they can play the piano very fast if they're skilled at it.

00:25:22.460 | And again, you get to similar units.

00:25:25.300 | Or how fast can people talk?

00:25:27.220 | You get to, within a couple of orders of magnitude,

00:25:30.100 | you get more or less to the same idea.

00:25:32.700 | So that's how you can say that there's billions of,

00:25:39.500 | there's room for billions of meaningful thoughts.

00:25:42.780 | I won't argue for exactly two billion versus 1.8 billion.

00:25:47.580 | It's not that kind of question.

00:25:49.340 | But I think any estimate that's reasonable

00:25:52.780 | will come out within, say, 100 billion and 100 million.

00:25:58.140 | So it's a lot.

00:25:59.820 | - It would be interesting to map out

00:26:04.100 | for an individual human being the landscape of thoughts

00:26:07.260 | that they've sort of traveled.

00:26:09.280 | If you think of thoughts as a set of trajectories,

00:26:12.920 | what that landscape looks like.

00:26:16.340 | I mean, I've been recently really thinking about

00:26:20.100 | this Richard Dawkins idea of memes

00:26:24.740 | and just all this ideas and the evolution of ideas

00:26:27.800 | inside of one particular human mind

00:26:29.860 | and how they're then changed and evolved

00:26:33.700 | by interaction with other human beings.

00:26:36.500 | It's interesting to think about.

00:26:38.060 | So if you think the number is billions,

00:26:41.860 | you think there's also social interaction.

00:26:44.340 | So these aren't, like there's interaction

00:26:48.660 | in the same way you have interaction with particles.

00:26:50.740 | There's interaction between human thoughts.

00:26:52.980 | Perhaps that interaction in itself

00:26:56.380 | is fundamental to the process of thinking.

00:26:59.120 | Like without social interaction,

00:27:01.380 | we would be stuck like walking in a circle.

00:27:04.100 | We need the perturbation of other humans

00:27:07.360 | to create change and evolution.

00:27:09.600 | - Once you bring in concepts of interactions

00:27:13.320 | and correlations and relations,

00:27:15.880 | then you have what's called a combinatorial explosion.

00:27:19.300 | That the number of possibilities

00:27:22.920 | expands exponentially, technically,

00:27:24.960 | with the number of things you're considering.

00:27:28.920 | And it can easily, rapidly outstrip

00:27:33.200 | these billions of thoughts that we're talking about.

00:27:36.800 | So we definitely cannot by brute force

00:27:41.680 | master complex situations

00:27:44.440 | or think of all the possibilities in a complex situations.

00:27:48.920 | I mean, even something as relatively simple as chess

00:27:53.480 | is still something that human beings

00:27:56.280 | can't comprehend completely.

00:27:57.840 | Even the best players lose, still sometimes lose,

00:28:00.920 | and they consistently lose to computers these days.

00:28:05.100 | And in computer science, there's a concept of NP-complete.

00:28:08.800 | So large classes of problems, when you scale them up

00:28:12.200 | beyond a few individuals, become intractable.

00:28:16.040 | And so in that sense, the world is inexhaustible.

00:28:20.960 | - But and that makes it beautiful

00:28:22.440 | that we can make any laws that generalize

00:28:27.200 | efficiently and well can compress all of that

00:28:31.400 | combinatorial complexity into a simple rule.

00:28:33.900 | That in itself is beautiful.

00:28:35.360 | - It's a happy situation, I think,

00:28:38.240 | that we can find general principles

00:28:43.240 | sort of of the operating system

00:28:45.760 | that are comprehensible, simple, extremely powerful,

00:28:49.880 | and let us control things very well

00:28:52.720 | and ask profound questions.

00:28:55.420 | And on the other hand, that the world

00:28:57.000 | is going to be inexhaustible.

00:28:58.560 | Once we start asking about relationships

00:29:03.280 | and how they evolve and social interactions,

00:29:07.080 | we'll never have a theory of everything

00:29:10.600 | in any meaningful sense because--

00:29:12.640 | - Of everything, everything.

00:29:15.120 | Truly everything is.

00:29:17.880 | Can I ask you about the Big Bang?

00:29:19.920 | So we talked about the space and time are really big,

00:29:23.460 | but then, and we humans give a lot of meaning

00:29:27.800 | to the word space and time in our daily lives.

00:29:32.300 | But then can we talk about this moment of beginning

00:29:37.320 | and how we're supposed to think about it?

00:29:39.360 | That at the moment of the Big Bang,

00:29:42.440 | everything was what, like infinitely small?

00:29:46.640 | And then it just blew up?

00:29:48.760 | - We have to be careful here

00:29:49.840 | 'cause there's a common misconception

00:29:53.480 | that the Big Bang is like the explosion of a bomb

00:29:58.480 | in empty space that fills up the surrounding place.

00:30:02.920 | - It is space.

00:30:03.920 | - It is, yeah.

00:30:05.280 | As we understand it, it's the fact,

00:30:08.920 | it's the fact or the hypothesis,

00:30:12.240 | but well-supported up to a point,

00:30:14.760 | that everywhere in the whole universe,

00:30:19.760 | early in the history,

00:30:23.160 | matter came together into a very hot, very dense,

00:30:28.120 | if you run it backwards in time,

00:30:29.920 | matter comes together into a very hot, very dense,

00:30:32.720 | and yet very homogeneous plasma

00:30:36.240 | of all the different kinds of elementary particles

00:30:39.480 | and quarks and antiquarks and gluons and photons

00:30:41.840 | and electrons and anti-electrons, everything,

00:30:43.840 | all of that stuff.

00:30:45.120 | - Like really hot, really, really dense.

00:30:48.560 | - Really hot.

00:30:49.400 | We're talking about way, way hotter

00:30:52.080 | than the surface of the sun.

00:30:53.620 | In fact, if you take the equations as they come,

00:31:00.640 | the prediction is that the temperature

00:31:02.920 | just goes to infinity, but then the equations break down.

00:31:07.000 | The equations become infinity equals infinity,

00:31:12.920 | so they don't feel, it's called a singularity.

00:31:15.080 | We don't really know.

00:31:16.200 | This is running the equations backwards,

00:31:19.640 | so you can't really get a sensible idea

00:31:21.760 | of what happened before the Big Bang.

00:31:24.360 | We need different equations

00:31:25.600 | to address the very earliest moments.

00:31:28.340 | So things were hotter and denser.

00:31:35.600 | We don't really know why things started out that way.

00:31:40.640 | We have a lot of evidence that they did start out that way,

00:31:43.960 | but since most of the,

00:31:47.840 | we don't get to visit there and do controlled experiments.

00:31:55.400 | Most of the record is very, very processed,

00:31:59.560 | and we have to use very subtle techniques

00:32:04.560 | and powerful instruments to get information

00:32:09.440 | that has survived.

00:32:11.080 | - Get closer and closer to the Big Bang.

00:32:12.800 | - Get closer and closer to the beginning of things.

00:32:16.480 | What's revealed there is that, as I said,

00:32:23.200 | there undoubtedly was a period when everything

00:32:26.120 | in the universe that we have been able to look at

00:32:29.560 | and understand, and that's consistent with everything,

00:32:38.200 | was in a condition where it was much, much hotter

00:32:41.360 | and much, much denser,

00:32:43.000 | but still obeying the laws of physics

00:32:46.320 | as we know them today.

00:32:47.560 | And then you start with that,

00:32:51.080 | so all the matter is in equilibrium,

00:32:53.140 | and then with small quantum fluctuations

00:32:57.920 | and run it forward, and then it produces,

00:33:01.720 | at least in broad strokes,

00:33:04.000 | the universe we see around us today.

00:33:06.600 | - Do you think we'll ever be able to,

00:33:09.200 | with the tools of physics, with the way science is,

00:33:12.640 | with the way the human mind is,

00:33:14.040 | we'll ever be able to get to the moment of the Big Bang

00:33:17.680 | in our understanding, or even the moment before the Big Bang?

00:33:21.720 | Can we understand what happened before the Big Bang?

00:33:24.720 | - I'm optimistic both that we'll be able to measure more,

00:33:29.720 | so observe more, and that we'll be able to figure out more.

00:33:36.660 | So there are very, very tangible prospects

00:33:40.660 | for observing the extremely early universe,

00:33:45.660 | so even much earlier than we can observe now,

00:33:49.420 | through looking at gravitational waves.

00:33:52.220 | Gravitational waves, since they interact so weakly

00:33:55.660 | with ordinary matter,

00:33:57.300 | sort of send a minimally processed signal from the Big Bang.

00:34:03.620 | It's a very weak signal, because it's traveled a long way

00:34:07.340 | and diffused over long spaces,

00:34:09.420 | but people are gearing up to try to detect

00:34:13.300 | gravitational waves that could have come

00:34:15.180 | from the early universe.

00:34:16.300 | - Yeah, LIGO's incredible engineering project,

00:34:19.100 | just the most sensitive, precise devices on Earth.

00:34:24.100 | The fact that humans can build something like that

00:34:27.500 | is truly awe-inspiring from an engineering perspective.

00:34:31.300 | - Right, but these gravitational waves

00:34:33.940 | from the early universe will probably be

00:34:36.500 | of a much longer wavelength than LIGO is capable of sensing,

00:34:41.460 | so there's a beautiful project that's contemplated

00:34:46.460 | to put lasers in different locations in the solar system.

00:34:53.340 | We really, really separated by solar system scale

00:34:59.100 | differences, like artificial planets or moons

00:35:02.220 | in different places, and see the tiny motions

00:35:05.540 | of those relative to one another as a signal

00:35:07.900 | of radiation from the Big Bang.

00:35:10.060 | We can also maybe indirectly see the imprint

00:35:15.060 | of gravitational waves from the early universe

00:35:18.300 | on the photons, the microwave background radiation

00:35:22.740 | that is our present way of seeing

00:35:25.940 | into the earliest universe.

00:35:27.200 | But those photons interact much more strongly

00:35:30.820 | with matter, they're much more strongly processed,

00:35:32.940 | so they don't give us directly such an unprocessed view

00:35:37.940 | of the early universe, of the very early universe.

00:35:41.100 | But if gravitational waves leave some imprint

00:35:45.020 | on that as they move through, we could detect that too,

00:35:49.380 | and people are trying, as we speak,

00:35:53.180 | working very hard towards that goal.

00:35:56.860 | - It's so exciting to think about a sensor

00:35:58.980 | the size of a solar system.

00:36:00.560 | - That would be a fantastic, I mean,

00:36:03.500 | that would be a pinnacle artifact of human endeavor to me.

00:36:07.540 | It would be such an inspiring thing

00:36:11.860 | that just we want to know, and we go

00:36:15.900 | to these extraordinary lengths of making gigantic things

00:36:19.360 | that are also very sophisticated,

00:36:20.820 | because what you're trying to do,

00:36:22.200 | you have to understand how they move,

00:36:24.920 | you have to understand the properties of light

00:36:27.980 | that are being used, the interference between light,

00:36:30.860 | and you have to be able to make the light with lasers

00:36:34.140 | and understand the quantum theory

00:36:35.700 | and get the timing exactly right.

00:36:38.020 | It's an extraordinary endeavor involving all kinds

00:36:41.660 | of knowledge from the very small to the very large,

00:36:45.060 | and all in the service of curiosity

00:36:49.020 | and built on a grand scale, so yeah.

00:36:54.140 | - Yeah, it'd make me proud to be a human if we did that.

00:36:58.320 | - I love that you're inspired both by the power of theory

00:37:01.280 | and the power of experiment, so both, I think,

00:37:04.560 | are exceptionally impressive that the human mind

00:37:08.640 | can come up with theories that give us a peek

00:37:11.600 | into how the universe works, but also construct tools

00:37:15.160 | that are way bigger than the evolutionary origins

00:37:19.920 | we came from. - Right, and by the way,

00:37:22.000 | the fact that we can design such things and they work

00:37:25.680 | is an extraordinary demonstration

00:37:28.160 | that we really do understand a lot.

00:37:30.600 | - And in some ways-- - And it's our ability

00:37:34.340 | to answer questions that also leads us to be able

00:37:37.820 | to address more ambitious questions.

00:37:39.800 | - So you mentioned that at the Big Bang in the early days,

00:37:44.180 | things are pretty homogeneous. - Yes.

00:37:47.840 | - But here we are, sitting on Earth,

00:37:51.640 | two hairless apes, you could say, with microphones.

00:37:56.640 | In talking about the brief history of things,

00:37:58.820 | you said it's much harder to describe Sweden

00:38:00.800 | than it is the universe, so there's a lot of complexity.

00:38:05.360 | There's a lot of interesting details here,

00:38:07.440 | so how does this complexity come to be, do you think?

00:38:11.000 | It seems like there's these pockets.

00:38:13.500 | - Yeah. - We don't know how rare

00:38:14.800 | of where hairless apes just emerge.

00:38:18.860 | - Yeah. - And then,

00:38:20.280 | that came from the initial soup that was homogeneous.

00:38:23.520 | Was that, is that an accident?

00:38:26.480 | - Well, we understand in broad outlines how it could happen.

00:38:31.480 | We certainly don't understand why it happened exactly

00:38:36.360 | in the way it did, but there are certainly open questions

00:38:41.360 | about the origins of life and how inevitable

00:38:45.640 | the emergence of intelligence was and how that happened.

00:38:48.920 | But in the very broadest terms,

00:38:52.160 | the universe early on was quite homogeneous,

00:38:58.000 | but not completely homogeneous.

00:39:00.120 | There were part in 10,000 fluctuations in density

00:39:07.040 | within this primordial plasma, and as time goes on,

00:39:12.040 | there's an instability which causes

00:39:17.640 | those density contrasts to increase.

00:39:20.120 | There's a gravitational instability.

00:39:21.680 | Where it's denser, the gravitational attractions

00:39:24.600 | are stronger, and so that brings in more matter,

00:39:27.240 | and it gets even denser, and so on and so on.

00:39:29.760 | So there's a natural tendency of matter to clump

00:39:34.360 | because of gravitational interactions.

00:39:37.160 | And then the equation gets complicated

00:39:40.160 | when you have lots of things clumping together.

00:39:42.860 | Then we know what the laws are,

00:39:47.020 | but we have to, to a certain extent,

00:39:49.120 | wave our hands about what happens.

00:39:51.840 | But basic understanding of chemistry says that if things,

00:39:56.840 | and the physics of radiation tells us

00:40:00.600 | that as things start to clump together,

00:40:02.800 | they can radiate, give off some energy,

00:40:05.500 | so they slow down, and as a result,

00:40:08.520 | they lose energy, they can clumber together,

00:40:11.040 | cool down, form things like stars,

00:40:14.000 | form things like planets, and so in broad terms,

00:40:18.300 | there's no mystery.

00:40:19.360 | That's what the equations tell you should happen,

00:40:25.440 | but because it's a process involving

00:40:30.560 | many, many individual units,

00:40:33.680 | the application of the laws that govern

00:40:39.560 | individual units to these things is very delicate,

00:40:44.560 | or computationally very difficult,

00:40:48.200 | and more profoundly, the equations have

00:40:52.000 | this probability of chaos,

00:40:53.320 | or sensitivity to initial conditions,

00:40:55.260 | which tells you tiny differences in the initial state

00:40:58.880 | can lead to enormous differences in the subsequent behavior.

00:41:02.400 | So physics, fundamental physics at some point says,

00:41:08.320 | okay, chemists, biologists, this is your problem.

00:41:11.780 | And then again, in broad terms,

00:41:16.640 | we know how it's conceivable that humans

00:41:21.640 | and things like that can,

00:41:24.660 | how complex structure can emerge.

00:41:28.120 | It's a matter of having the right kind of temperature

00:41:33.120 | and the right kind of stuff,

00:41:36.280 | so you need to be able to make chemical bonds

00:41:41.280 | that are reasonably stable,

00:41:42.840 | and be able to make complex structures.

00:41:45.360 | And we're very fortunate that carbon has this ability

00:41:48.680 | to make backbones and elaborate branchings and things,

00:41:53.680 | so you can get complex things that we call biochemistry,

00:41:57.560 | and yet the bonds can be broken a little bit

00:42:01.120 | with the help of energetic injections from the sun,

00:42:04.720 | so you have to have both the possibility of changing,

00:42:07.400 | but also the useful degree of stability.

00:42:10.560 | And we know at that very, very broad level,

00:42:14.000 | physics can tell you that it's conceivable.

00:42:17.760 | If you want to know what actually,

00:42:19.840 | what really happened, what really can happen,

00:42:24.120 | then you have to work, go to chemistry.

00:42:27.000 | If you want to know what actually happened,

00:42:29.800 | then you really have to consult

00:42:31.320 | the fossil record and biologists.

00:42:33.200 | And so, but it's, so these ways of addressing the issue

00:42:38.200 | are complementary in a sense.

00:42:43.480 | They use different kinds of concepts,

00:42:48.480 | they use different languages,

00:42:52.440 | and they address different kinds of questions,

00:42:54.320 | but they're not inconsistent, they're just complementary.

00:42:59.320 | - It's kind of interesting to think about

00:43:01.000 | those early fluctuations as our earliest ancestors.

00:43:06.000 | - Yes, that's right.

00:43:08.160 | So it's amazing to think that, you know,

00:43:11.360 | this is the modern answer to the,

00:43:16.820 | well, the modern version of what the Hindu philosophers had,

00:43:23.880 | that art thou.

00:43:25.680 | If you ask, okay, that, those little quantum fluctuations

00:43:30.440 | in the early universe are the seeds out of which complexity,

00:43:34.600 | including plausibly humans, really evolve.

00:43:40.840 | You don't need anything else.

00:43:42.200 | - That brings up the question of asking for a friend here,

00:43:47.200 | if there's, you know, other pockets of complexity,

00:43:52.080 | commonly called as alien intelligent civilizations out there.

00:43:59.400 | - Well, we don't know for sure,

00:44:00.880 | but I have a strong suspicion that the answer is yes,

00:44:05.700 | because the one case we do have at hand to study

00:44:10.700 | here on Earth, we sort of know what the conditions were

00:44:17.680 | that were helpful to life,

00:44:18.840 | the right kind of temperature, the right kind of star

00:44:21.680 | that keeps, maintains that temperature for a long time,

00:44:24.240 | the liquid environment of water.

00:44:28.360 | And once those conditions emerged on Earth,

00:44:33.360 | which was roughly four and a half billion years ago,

00:44:36.000 | it wasn't very long before what we call life

00:44:39.640 | started to leave relics.

00:44:41.520 | So we can find forms of life, primitive forms of life

00:44:46.520 | that are almost as old as the Earth itself,

00:44:49.940 | in the sense that once the Earth became,

00:44:54.080 | was turned from a very hot boiling thing

00:44:58.640 | and cooled off into a solid mass with water,

00:45:02.480 | life emerged very, very quickly.

00:45:03.920 | So it seems that these general conditions for life

00:45:07.800 | are enough to make it happen relatively quickly.

00:45:13.860 | Now, the other lesson I think that one can draw

00:45:19.880 | from this one example,

00:45:22.560 | it's dangerous to draw lessons from one example,

00:45:25.280 | but that's all we've got.

00:45:26.820 | And that the emergence of intelligent life

00:45:32.020 | is a different issue altogether.

00:45:34.220 | That took a long time

00:45:36.800 | and seems to have been pretty contingent.

00:45:42.140 | For a long time, well, for most of the history of life,

00:45:50.560 | it was single-celled things.

00:45:54.020 | Even multicellular life only rose

00:45:58.000 | about 600 million years ago, so much after.

00:46:01.520 | And then intelligence is kind of a luxury,

00:46:09.680 | if you think.

00:46:11.280 | Many more kinds of creatures have big stomachs

00:46:17.520 | than big brains.

00:46:20.200 | In fact, most have no brains at all

00:46:23.520 | in any reasonable sense.

00:46:25.320 | And the dinosaurs ruled for a long, long time,

00:46:30.140 | and some of them were pretty smart,

00:46:31.480 | but they were at best bird brains

00:46:35.260 | because birds came from the dinosaurs.

00:46:37.720 | And it could have stayed that way.

00:46:41.860 | And the emergence of humans was very contingent

00:46:46.240 | and kind of a very, very recent development

00:46:49.560 | on evolutionary timescales.

00:46:51.800 | And you can argue about the level of human intelligence,

00:46:55.040 | but I think it's--

00:46:56.720 | - Pretty impressive.

00:46:57.560 | - That's what we're talking about.

00:46:58.400 | And it's very impressive,

00:47:00.360 | and can ask these kinds of questions

00:47:02.280 | and discuss them intelligently.

00:47:04.000 | So I guess my, so this is a long-winded answer

00:47:12.040 | or justification of my feeling is that

00:47:18.440 | the conditions for life in some form

00:47:23.440 | are probably satisfied in many, many places

00:47:28.680 | around the universe, and even within our galaxy.

00:47:32.100 | I'm not so sure about the emergence of intelligent life

00:47:36.040 | or the emergence of technological civilizations.

00:47:41.800 | That seems much more contingent and special

00:47:47.360 | and we might, it's conceivable to me

00:47:50.360 | that we're the only example in the galaxy.

00:47:52.840 | Although, yeah, I don't know one way or the other.

00:47:56.640 | I have different opinions on different days of the week.

00:47:59.600 | - But one of the things that worries me

00:48:01.400 | in the spirit of being humble,

00:48:04.640 | that our particular kind of intelligence

00:48:08.000 | is not very special.

00:48:10.680 | So there's all kinds of different intelligences.

00:48:13.680 | And even more broadly,

00:48:15.000 | there could be many different kinds of life.

00:48:19.080 | So the basic definition, and I just had,

00:48:22.440 | I think somebody that you know, Sarah Walker,

00:48:24.840 | I just had a very long conversation with her

00:48:27.280 | about even just the very basic question

00:48:29.360 | of trying to define what is life

00:48:32.360 | from a physics perspective.

00:48:34.580 | Even that question within itself,

00:48:36.080 | I think one of the most fundamental questions

00:48:38.160 | in science and physics and everything

00:48:41.080 | is just trying to get a hold,

00:48:43.760 | trying to get some universal laws

00:48:45.480 | around the ideas of what is life.

00:48:47.400 | 'Cause that kind of unlocks a bunch of things

00:48:49.640 | around life, intelligence, consciousness,

00:48:52.400 | all those kinds of things.

00:48:53.400 | - I agree with you in a sense,

00:48:55.000 | but I think that's a dangerous question

00:48:56.520 | because the answer can't be any more precise

00:49:01.520 | than the question.

00:49:02.880 | And the question what is life

00:49:06.120 | kind of assumes that we have a definition of life

00:49:11.280 | and that it's a natural phenomena

00:49:12.880 | that can be distinguished.

00:49:14.600 | But really there are edge cases like viruses

00:49:17.520 | and some people would like to say

00:49:20.720 | that electrons have consciousness.

00:49:24.960 | So you can't, if you really have fuzzy concepts,

00:49:28.640 | it's very hard to reach precise kinds of scientific answers.

00:49:33.640 | But I think there's a very fruitful question

00:49:36.960 | that's adjacent to it, which has been pursued

00:49:40.960 | in different forms for quite a while

00:49:44.960 | and is now becoming very sophisticated

00:49:47.800 | in reaching in new directions.

00:49:49.960 | And that is what are the states of matter

00:49:53.880 | that are possible?

00:49:55.080 | So in high school or grade school,

00:49:58.400 | you learn about solids, liquids and gases,

00:50:01.680 | but that really just scratches the surface

00:50:04.640 | of different ways that are distinguishable,

00:50:07.760 | that matter can form into macroscopically different

00:50:12.760 | meaningful patterns that we call phases.

00:50:17.360 | And then there are precise definitions

00:50:19.400 | of what we mean by phases of matter

00:50:21.640 | and that have been worked out fruitful over the decades.

00:50:26.080 | And we're discovering new states of matter all the time

00:50:29.800 | and kind of having to work at what we mean by matter.

00:50:33.240 | We're discovering the capabilities of matter

00:50:35.920 | to organize in interesting ways.

00:50:39.560 | And some of them like liquid crystals

00:50:44.560 | are important ingredients of life,

00:50:49.000 | our cell membranes are liquid crystals,

00:50:51.680 | and that's very important to the way they work.

00:50:54.040 | Recently, there's been a development

00:50:57.320 | in where we're talking about states of matter

00:51:01.440 | that are not static,

00:51:04.240 | but that have dynamics,

00:51:06.560 | that have characteristic patterns,

00:51:09.560 | not only in space, but in time.

00:51:11.500 | These are called time crystals.

00:51:12.840 | And that's been a development

00:51:14.400 | that's just in the last decade or so,

00:51:17.520 | it's just really, really flourishing.

00:51:20.760 | And so is there a state of matter

00:51:25.760 | or a group of states of matter that corresponds to life?

00:51:31.600 | Maybe, but the answer can't be any more definite

00:51:34.480 | than the question.

00:51:35.880 | - I mean, I gotta push back on the,

00:51:38.760 | those are just words.

00:51:39.920 | I mean, I disagree with you.

00:51:42.000 | The question points to a direction.

00:51:45.920 | The answer might be able to be more precise

00:51:49.200 | than the question.

00:51:51.040 | Because just as you're saying,

00:51:53.440 | we could be discovering certain characteristics

00:51:58.600 | and patterns that are associated

00:52:00.600 | with a certain type of matter, macroscopically speaking.

00:52:04.440 | And that we can then be able to post facto say,

00:52:09.440 | this is, let's assign the word life

00:52:13.080 | to this kind of matter.

00:52:14.440 | - I agree with that completely.

00:52:16.000 | That's, so it's not a disagreement.

00:52:19.800 | It's very frequent in physics that,

00:52:22.360 | or in science, that words that are in common use

00:52:26.840 | gets, get refined and reprocessed into scientific terms.

00:52:31.360 | That's happened for things like force and energy.

00:52:34.260 | And so we, in a way, we find out

00:52:38.760 | what the useful definition is, or symmetry, for instance.

00:52:43.760 | And the common usage may be quite different

00:52:47.240 | from the scientific usage,

00:52:48.440 | but the scientific usage is special

00:52:52.000 | and takes on a life of its own.

00:52:53.340 | And we find out what the useful version of it is,

00:52:58.340 | what the fruitful version of it is.

00:53:02.040 | So I do think, so in that spirit,

00:53:05.320 | I think if we can identify states of matter

00:53:10.320 | or linked states of matter that can carry on processes

00:53:18.000 | of self-reproduction and development

00:53:23.040 | and information processing,

00:53:27.360 | we should say, we might be tempted

00:53:30.600 | to classify those things as life.

00:53:34.200 | - Well, can I ask you about the craziest one,

00:53:36.820 | which is the one we know maybe least about,

00:53:41.540 | which is consciousness?

00:53:42.700 | Is it possible that there are certain kinds of matter

00:53:44.960 | would be able to classify as conscious,

00:53:50.320 | meaning, so there's the panpsychists, right,

00:53:54.400 | or the philosophers who kind of try to imply

00:53:57.880 | that all matter has some degree of consciousness

00:54:01.200 | and you can almost construct

00:54:02.460 | like a physics of consciousness.

00:54:04.160 | Again, we're in such early days of this,

00:54:09.240 | but nevertheless, it seems useful to talk about.

00:54:13.080 | Is there some sense from a physics perspective

00:54:15.860 | to make sense of consciousness?

00:54:17.400 | Is there some hope?

00:54:19.680 | - Yeah, consciousness is--

00:54:21.520 | - Imprecise.

00:54:23.400 | - A very imprecise word and loaded with connotations

00:54:27.680 | that I think we don't wanna start a scientific analysis

00:54:31.560 | with that, I don't think.

00:54:32.800 | It's often been important in science

00:54:38.320 | to start with simple cases and work up.

00:54:41.680 | Consciousness, I think what most people think of

00:54:45.840 | when you talk about consciousness is,

00:54:47.720 | okay, what am I doing in the world?

00:54:52.720 | This is my experience.

00:54:53.840 | I have a rich inner life and experience,

00:54:57.120 | and where is that in the equations?

00:54:59.520 | I think that's a great question, a great, great question,

00:55:03.400 | and actually, I think I'm gearing up to spend part of the,

00:55:07.720 | I mean, to try to address that in coming years.

00:55:10.960 | - One version of asking that question,

00:55:12.640 | just as you said now, is what is the simplest formulation

00:55:17.280 | of that to study?

00:55:18.560 | - I think I'm much more comfortable with the idea

00:55:21.520 | of studying self-awareness as opposed to consciousness,

00:55:25.440 | 'cause that sort of gets rid of the mystical aura

00:55:29.160 | of the thing, and self-awareness is in simple,

00:55:33.760 | I think contiguous, at least, with ideas about feedback.

00:55:40.560 | So if you have a system that looks at its own state

00:55:45.360 | and responds to it, that's a kind of self-awareness,

00:55:48.840 | and more sophisticated versions could be like

00:55:55.200 | in information processing things,

00:55:57.360 | computers that look into their own internal state

00:56:00.520 | and do something about it, and I think

00:56:03.960 | that could also be done in neural nets.

00:56:08.280 | This is called recurrent neural nets,

00:56:10.280 | which are hard to understand and kind of a frontier.

00:56:13.280 | So I think understanding those and gradually building up

00:56:18.280 | a kind of profound ability to conceptualize

00:56:26.160 | different levels of self-awareness,

00:56:32.200 | what do you have to not know and what do you have to know,

00:56:34.600 | and when do you know that you don't know it,

00:56:36.720 | or what do you think you know that you don't really know?

00:56:41.720 | I think clarifying those issues,

00:56:45.720 | when we clarify those issues and get a rich theory

00:56:48.760 | around self-awareness, I think that will illuminate

00:56:53.760 | the questions about consciousness in a way that,

00:56:58.200 | scratching your chin and talking about qualia

00:57:00.840 | and blah, blah, blah, blah is never gonna do.

00:57:04.280 | - Well, I also have a different approach

00:57:06.280 | to the whole thing, so there's, from a robotics perspective,

00:57:09.080 | you can engineer things that exhibit

00:57:12.840 | qualities of consciousness without understanding

00:57:15.320 | how things work, and from that perspective,

00:57:21.960 | it's like a back door, like enter through

00:57:26.400 | the psychology door. - Precisely.

00:57:28.760 | - The cognitive science door. - I think we're on

00:57:31.120 | the same wavelength here.

00:57:32.360 | And let me just add one comment, which is,

00:57:37.440 | I think we should try to understand consciousness

00:57:41.840 | as we experience it, in evolutionary terms,

00:57:46.840 | and ask ourselves, why, why does it happen?

00:57:53.000 | - This thing seems useful, why is it useful?

00:57:55.240 | - Why is it useful? - Interesting question.

00:57:57.120 | (laughing)

00:57:59.280 | - We've got a conscious eye watch here.

00:58:01.560 | Interesting question, thank you, Siri.

00:58:03.480 | Okay.

00:58:06.320 | - Thank you, brother.

00:58:08.120 | - I'll get back to you later.

00:58:09.520 | (laughing)

00:58:11.760 | And I think, I'm morally certain that what's gonna emerge

00:58:18.120 | from analyzing recurrent neural nets and robotic design

00:58:23.480 | and advanced computer design is that having this kind of

00:58:29.160 | looking at the internal state in a structured way

00:58:35.720 | that doesn't look at everything, it's encapsulated,

00:58:40.560 | looks at highly processed information,

00:58:42.240 | is very selective and makes choices

00:58:44.360 | without knowing how they're made,

00:58:45.760 | so there'll also be an unconscious.

00:58:47.320 | I think that that is gonna turn out to be really essential

00:58:51.880 | to doing efficient information processing.

00:58:55.440 | And that's why it evolved, because it's helpful.

00:59:03.400 | Because brains come at a high cost.

00:59:06.200 | - So there has to be a good why.

00:59:09.440 | - And there's a reason, yeah, they're rare in evolution.

00:59:13.000 | And big brains are rare in evolution

00:59:17.680 | and they come at a big cost.

00:59:19.880 | I mean, they have high metabolic demands.

00:59:24.880 | They require very active lifestyle, warm-bloodedness,

00:59:32.760 | and take away from the ability to support metabolism

00:59:37.760 | of digestion, so it comes at a high cost.

00:59:42.240 | It has to pay back.

00:59:44.280 | - Yeah, I think it has a lot of value in social interaction.

00:59:47.120 | So I actually am spending the rest of the day today

00:59:49.560 | and with our friends that are, our legged friends

00:59:54.560 | in robotic form at Boston Dynamics.

00:59:59.120 | And I think, so my probably biggest passion

01:00:03.760 | is human-robot interaction.

01:00:05.800 | And it seems that consciousness from the perspective

01:00:09.480 | of the robot is very useful to improve

01:00:12.920 | the human-robot interaction experience.

01:00:15.260 | The first, the display of consciousness,

01:00:18.540 | but then to me there's a gray area

01:00:20.200 | between the display of consciousness

01:00:21.960 | and consciousness itself.

01:00:23.640 | If you think of consciousness

01:00:24.920 | from an evolutionary perspective,

01:00:26.900 | it seems like a useful tool in human communication.

01:00:29.880 | - Yes, it's certainly, well,

01:00:32.040 | whatever consciousness is will turn out to be.

01:00:35.240 | I think addressing it through its use

01:00:39.700 | and working up from simple cases

01:00:42.060 | and also working up from engineering experience

01:00:45.680 | in trying to do efficient computation,

01:00:48.760 | including efficient management of social interactions

01:00:53.380 | is going to really shed light on these questions.

01:00:56.260 | As I said, in a way that sort of musing abstractly

01:00:59.680 | about consciousness never would.

01:01:01.640 | - So as I mentioned, I talked to Sarah Walker

01:01:04.040 | and first of all, she says hi,

01:01:05.920 | spoke very highly of you.

01:01:07.560 | One of her concerns about physics and physicists and humans

01:01:12.420 | is that we may not fully understand the system

01:01:16.960 | that we're inside of.

01:01:19.000 | Meaning, like, there may be limits

01:01:22.880 | to the kind of physics we do

01:01:24.440 | in trying to understand the system of which we're part of.

01:01:28.760 | So like, the observer is also the observed.

01:01:33.760 | In that sense, it seems like

01:01:36.720 | our tools of understanding the world,

01:01:42.760 | I mean, this is mostly centered around the questions

01:01:44.840 | of what is life, trying to understand the patterns

01:01:47.520 | that are characteristic of life and intelligence,

01:01:51.300 | all those kinds of things.

01:01:53.320 | We're not using the right tools because we're in the system.

01:01:57.360 | Is there something that resonates with you there?

01:02:01.360 | Almost like-- - Well, yes.

01:02:03.720 | We do have, we have limitations, of course,

01:02:08.560 | in the amount of information we can process.

01:02:11.740 | On the other hand, we can get help from our silicon friends

01:02:16.840 | and we can get help from all kinds of instruments

01:02:21.460 | that make up for our perceptual deficits.

01:02:24.200 | And we have to, and we can use, at a conceptual level,

01:02:30.040 | we can use different kinds of concepts

01:02:32.760 | to address different kinds of questions.

01:02:35.360 | So I'm not sure exactly what problem she's talking about.

01:02:40.280 | - It's the problem akin to an organism living

01:02:44.000 | in a 2D plane trying to understand a three-dimensional world.

01:02:47.800 | - Well, we can do that.

01:02:48.920 | I mean, we, in fact, for practical purposes,

01:02:53.340 | most of our experience is two-dimensional.

01:02:55.780 | It's hard to move vertically, and yet we've produced

01:02:59.420 | conceptually a three-dimensional symmetry,

01:03:01.780 | and in fact, four-dimensional space-time.

01:03:04.420 | So by thinking in appropriate ways and using instruments

01:03:10.420 | and getting consistent accounts and rich accounts,

01:03:14.820 | we find out what concepts are necessary.

01:03:18.740 | And I don't see any end in sight of the process

01:03:25.920 | or any showstoppers because,

01:03:28.880 | let me give you an example.

01:03:32.160 | I mean, for instance, QCD,

01:03:35.400 | our theory of the strong interaction,

01:03:37.320 | has nice equations, which I helped to discover.

01:03:40.280 | - What's QCD?

01:03:41.240 | - Quantum chromodynamics.

01:03:42.860 | So it's our theory of the strong interaction,

01:03:47.460 | the interaction that is responsible for nuclear physics.

01:03:51.380 | So it's the interaction that governs how quarks

01:03:53.700 | and gluons interact with each other

01:03:55.300 | and make protons and neutrons and all the strong,

01:04:00.300 | the related particles and many things in physics.

01:04:05.340 | That's one of the four basic forces of nature

01:04:07.900 | as we presently understand it.

01:04:11.080 | And so we have beautiful equations,

01:04:15.740 | which we can test in very special circumstances,

01:04:20.740 | using at high energies, at accelerators.

01:04:25.660 | So we're certain that these equations are correct.

01:04:28.660 | Prizes are given for it, and so,

01:04:30.460 | and people try to knock it down and they can't.

01:04:38.660 | But the situations in which we can calculate

01:04:42.960 | the consequences of these equations are very limited.

01:04:46.200 | So for instance, no one has been able to demonstrate

01:04:51.200 | that this theory, which is built on quarks and gluons,

01:04:57.000 | which no one, which you don't observe,

01:05:01.000 | actually produces protons and neutrons

01:05:03.280 | and the things you do observe.

01:05:04.480 | This is called the problem of confinement.

01:05:07.560 | So no one's been able to prove that analytically

01:05:10.960 | in a way that a human can understand.

01:05:13.500 | On the other hand, we can take these equations

01:05:16.620 | to a computer, to gigantic computers and compute,

01:05:20.380 | and by God, you get the world from it.

01:05:25.380 | So these equations, in a way that we don't understand

01:05:30.420 | in terms of human concepts, we can't do the calculations,

01:05:36.720 | but our machines can do them.

01:05:38.980 | So with the help of what I like to call our silicon friends

01:05:43.440 | and their descendants in the future,

01:05:46.560 | we can understand in a different way

01:05:50.680 | that allows us to understand more.

01:05:52.980 | But I don't think we'll ever,

01:05:55.020 | no human is ever going to be able

01:05:56.820 | to solve those equations in the same way.

01:06:00.220 | But I think that's, you know,

01:06:04.740 | when we find limitations to our natural abilities,

01:06:09.540 | we can try to find workarounds,

01:06:12.860 | and sometimes that's appropriate concepts,

01:06:15.140 | sometimes it's appropriate instruments,

01:06:17.300 | sometimes it's a combination of the two,

01:06:19.740 | but I think it's premature to get defeatist about it.

01:06:24.740 | I don't see any logical contradiction

01:06:32.500 | or paradox or limitation

01:06:35.060 | that will bring this process to a halt.

01:06:38.300 | - Well, I think the idea is to continue thinking

01:06:40.980 | outside the box in different directions,

01:06:42.900 | meaning just like how the math allows us

01:06:45.860 | to think in multiple dimensions

01:06:47.280 | outside of our perception system,

01:06:49.060 | sort of thinking, you know,

01:06:54.580 | coming up with new tools of mathematics or computation

01:06:57.100 | or all those kinds of things

01:07:00.980 | to take different perspectives on our universe.

01:07:04.220 | - Well, I'm all for that, you know,

01:07:05.740 | and I kind of have even elevated it into a principle,

01:07:08.820 | which is of complementarity, following Bohr,

01:07:11.540 | that you need different ways of thinking,

01:07:16.540 | even about the same things,

01:07:18.660 | in order to do justice to their reality

01:07:21.120 | and answer different kinds of questions about them.

01:07:23.940 | I mean, we've several times alluded to the fact

01:07:27.540 | that human beings are hard to understand

01:07:30.300 | and the concepts that you use to understand human beings,

01:07:34.580 | if you wanna prescribe drugs for them

01:07:37.660 | or see what's gonna happen if they move very fast

01:07:42.580 | or are exposed to radiation,

01:07:45.180 | and so that requires one kind of thinking

01:07:47.180 | that's very physical,

01:07:48.700 | based on the fact that the materials that we're made out of.

01:07:55.420 | On the other hand, if you want to understand

01:07:57.620 | how a person's going to behave

01:07:59.380 | in a different kind of situation,

01:08:01.220 | you need entirely different concepts from psychology,

01:08:06.100 | and there's nothing wrong with that.

01:08:08.460 | You can have very different ways

01:08:09.740 | of addressing the same material

01:08:11.800 | that are useful for different purposes, right?

01:08:14.900 | - Can you describe this idea,

01:08:16.100 | which is fascinating, of complementarity a little bit?

01:08:18.900 | Sort of, first of all, what state is the principle?

01:08:23.900 | What is it?

01:08:26.780 | And second of all, what are good examples?

01:08:29.140 | Starting from quantum mechanics,

01:08:30.900 | you still mentioned psychology.

01:08:32.660 | Let's talk about this more.

01:08:33.500 | It's like, in your new book,

01:08:34.860 | one of the most fascinating ideas, actually.

01:08:37.060 | - I think it's a wonderful, yeah.

01:08:40.220 | To me, it's, well, it's the culminating chapter of the book,

01:08:43.140 | and I think, since the whole book is about the big lessons

01:08:48.140 | or big takeaways from profound understanding

01:08:52.500 | of the physical world that we've achieved,

01:08:55.500 | including that it's mysterious in some ways,

01:08:59.080 | the, this was the final,

01:09:03.580 | overarching lesson, complementarity.

01:09:08.220 | And it's a approach.

01:09:13.220 | So, unlike some of these other things,

01:09:18.460 | which are just facts about the world,

01:09:20.580 | like the world is both big and small

01:09:22.420 | in different sense, and is big, but we're not small,

01:09:26.260 | the things we talked about earlier,

01:09:28.420 | and the fact that the universe is comprehensible,

01:09:30.760 | and how complexity could emerge from simplicity,

01:09:33.560 | and those things are, in the broad sense,

01:09:37.840 | facts about the world,

01:09:39.720 | complementarity is more an attitude towards the world,

01:09:42.920 | and encouraged by the facts about the world.

01:09:46.280 | And it's the idea, the concept, or the approach,

01:09:53.640 | that, or the realization, that it can be appropriate,

01:09:58.640 | and useful, and inevitable, and unavoidable

01:10:02.840 | to use very different descriptions of the same object,

01:10:07.840 | or the same system, or the same situation,

01:10:11.740 | to answer different kinds of questions

01:10:15.500 | that may be very different,

01:10:17.920 | and even mutually uninterpretable,

01:10:22.960 | and mutually incomprehensible.

01:10:26.920 | - But both correct somehow.

01:10:28.960 | - But both correct, and sources

01:10:30.960 | of different kinds of insight.

01:10:32.720 | - Which is so weird.

01:10:34.040 | - Yeah, well--

01:10:34.880 | - But it seems to work in so many cases.

01:10:36.600 | - It works in many cases, and I think it's a deep fact

01:10:41.080 | about the world, and how we should approach it.

01:10:44.600 | It's most rigorous form, where it's actually a theorem,

01:10:50.960 | if quantum mechanics is correct,

01:10:53.480 | occurs in quantum mechanics,

01:10:55.320 | where the primary description of the world

01:11:00.320 | is in terms of wave functions.

01:11:03.360 | But let's not talk about the world,

01:11:04.640 | let's just talk about a particle, an electron.

01:11:07.440 | The primary description of that electron

01:11:12.560 | is its wave function.

01:11:14.400 | And the wave function can be used to predict

01:11:19.920 | where it's gonna be, if you observe,

01:11:23.040 | it'll be in different places with different probabilities,

01:11:25.680 | or how fast it's moving,

01:11:27.480 | and it'll also be moving in different ways

01:11:31.240 | with different probabilities,

01:11:32.720 | that's what quantum mechanics says.

01:11:35.200 | And you can predict either set of probabilities,

01:11:39.360 | what's gonna happen if I make an observation

01:11:42.940 | of the position or the velocity.

01:11:47.400 | But, so the wave function gives you ways

01:11:50.240 | of doing both of those, but to do it,

01:11:53.200 | to get those predictions, you have to process

01:11:55.280 | the wave function in different ways.

01:11:57.280 | You process it one way for position,

01:11:59.080 | and in a different way for momentum,

01:12:01.480 | and those ways are mathematically incompatible.

01:12:05.360 | It's like, you know, it's like you have a stone

01:12:08.440 | and you can sculpt it into a Venus de Milo,

01:12:11.120 | or you can sculpt it into David, but you can't do both.

01:12:15.440 | And that's an example of complementarity,

01:12:20.440 | to answer different kinds of questions,

01:12:22.540 | you have to analyze the system in different ways

01:12:25.880 | that are mutually incompatible,

01:12:29.160 | but both valid to answer different kinds of questions.

01:12:32.760 | So in that case, it's a theorem,

01:12:34.840 | but I think it's a much more widespread phenomena

01:12:38.880 | that applies to many cases

01:12:40.400 | where we can't prove it as a theorem,

01:12:42.400 | but it's a piece of wisdom, if you like,

01:12:46.480 | and appears to be a very important insight.

01:12:51.480 | - Do you--

01:12:52.960 | - And if you ignore it, you can get very confused

01:12:57.040 | and misguided.

01:13:01.600 | - Do you think this is a useful hack

01:13:07.000 | for ideas that we don't fully understand,

01:13:10.560 | or is this somehow a fundamental property

01:13:13.720 | of all or many ideas that you can take multiple perspectives

01:13:18.720 | and they're both true?

01:13:20.800 | - Well, I think it's both.

01:13:22.160 | - So it's both the answer to all questions.

01:13:26.040 | - Yes, that's right.

01:13:27.400 | It's not either or, it's both.

01:13:28.920 | - It's paralyzing to think that we live in a world

01:13:32.760 | that's fundamentally surrounded by complementary ideas.

01:13:39.520 | Because we want universe,

01:13:41.880 | we somehow want to attach ourselves to absolute truths,

01:13:45.720 | and absolute truths certainly don't like

01:13:48.000 | the idea of complementarity.

01:13:50.080 | - Yes, Einstein was very uncomfortable with complementarity.

01:13:53.120 | And in a broad sense, the famous Bohr-Einstein debates

01:13:57.400 | revolved around this question

01:14:00.720 | of whether the complementarity

01:14:03.000 | that is a foundational feature of quantum mechanics

01:14:08.280 | as we have it is a permanent feature of the universe

01:14:13.280 | and our description of nature.

01:14:19.000 | And so far, quantum mechanics wins.

01:14:22.880 | (laughing)

01:14:23.720 | And it's gone from triumph to triumph.

01:14:26.440 | Whether complementarity is rock bottom,

01:14:28.680 | I guess you can never be sure.

01:14:31.560 | I mean, but it looks awfully good

01:14:34.200 | and it's been very successful.

01:14:35.520 | And certainly, complementarity has been extremely useful

01:14:40.360 | and fruitful in that domain,

01:14:43.440 | including some of Einstein's attempts to challenge it,

01:14:49.340 | like the famous Einstein-Podolsky-Rosen experiment

01:14:55.400 | turned out to be confirmations

01:14:57.320 | that have been useful in themselves.

01:15:03.240 | But so thinking about these things was fruitful,

01:15:05.120 | but not in the way that Einstein hoped.

01:15:07.880 | Yeah, so as I said,

01:15:15.440 | in the case of quantum mechanics

01:15:19.560 | and this dilemma or dichotomy

01:15:22.000 | between processing the wave function in different ways,

01:15:29.200 | it's a theorem.

01:15:30.040 | They're mutually incompatible

01:15:31.120 | and that the physical correlate of that

01:15:32.840 | is the Heisenberg uncertainty principle

01:15:35.040 | that you can't have position and momentum

01:15:37.600 | determined at once.

01:15:38.840 | But in other cases,

01:15:43.960 | like one that I like to think about

01:15:48.080 | or like to point out as an example

01:15:50.080 | is free will and determinism.

01:15:52.960 | It's much less of a theorem

01:15:57.160 | and more a kind of

01:16:02.520 | way of thinking about things

01:16:06.200 | that I think is reassuring

01:16:10.600 | and avoids a lot of unnecessary quarreling and confusion.

01:16:15.600 | - The quarreling I'm okay with

01:16:17.440 | and the confusion I'm okay with,

01:16:18.920 | I mean, people debate about difficult ideas,

01:16:21.600 | but the question is whether it could be

01:16:24.520 | almost a fundamental truth.

01:16:26.840 | - I think it is a fundamental truth.

01:16:28.280 | - Free will is both an illusion

01:16:31.560 | and not.

01:16:32.600 | - Yes, I think that's correct.

01:16:34.200 | - And there's a reason why people say

01:16:37.400 | quantum mechanics is weird

01:16:39.240 | and complementarity is a big part of that.

01:16:42.780 | To say that our actual whole world is weird,

01:16:48.720 | the whole hierarchy of the universe is weird

01:16:52.080 | in this kind of particular way,

01:16:54.400 | and it's quite profound,

01:16:58.440 | but it's also humbling

01:17:01.440 | because it's like we're never going to be on sturdy ground

01:17:06.720 | in the way that humans like to be.

01:17:09.300 | It's like you have to embrace that

01:17:11.000 | this whole thing is a unsteady mess.

01:17:17.840 | - It's one of many lessons in humility

01:17:21.080 | that we run into in profound understanding of the world.

01:17:27.040 | I mean, the Copernican revolution was one,

01:17:30.680 | that the Earth is not the center of the universe.

01:17:35.160 | Darwinian evolution is another,

01:17:36.920 | that humans are not the pinnacle

01:17:39.640 | of God's creation.

01:17:45.240 | And the apparent result of deep understanding

01:17:56.480 | of physical reality, that mind emerges from matter,

01:18:00.360 | and there's no call on special life forces or souls.

01:18:05.360 | These are all lessons in humility,

01:18:11.400 | and I actually find complementarity a liberating concept.

01:18:16.400 | It's, okay, you know--

01:18:21.520 | - Yeah, it is in a way.

01:18:22.680 | (laughing)

01:18:24.920 | There's a story about Dr. Johnson,

01:18:30.880 | and he's talking with Boswell,

01:18:32.640 | and Boswell was, they were discussing a sermon

01:18:36.440 | that they'd both heard,

01:18:37.840 | and the sort of culmination of the sermon

01:18:41.160 | was the speaker saying, "I accept the universe."

01:18:45.400 | And Dr. Johnson said, "Well, he'd damn well better."

01:18:49.280 | (laughing)

01:18:51.400 | And there's a certain joy in accepting the universe,

01:18:55.720 | because it's mind-expanding.

01:18:57.320 | And to me, complementarity also suggests tolerance,

01:19:07.480 | suggests opportunities for understanding things

01:19:15.160 | in different ways, that add to,

01:19:20.760 | rather than detract from understanding.

01:19:25.080 | So I think it's an opportunity for mind expansion,

01:19:30.080 | and demanding that there's only one way

01:19:33.200 | to think about things can be very limiting.

01:19:36.760 | - On the free will one, that's a trippy one, though.

01:19:38.960 | (laughing)

01:19:39.800 | To think like I am the decider of my own actions,

01:19:43.560 | and at the same time, I'm not,

01:19:45.360 | is tricky to think about,

01:19:49.800 | but there does seem to be some kind of profound truth

01:19:53.480 | in that.

01:19:54.320 | - I get, well, I think it is tied up,

01:19:56.880 | it will turn out to be tied up

01:19:58.400 | when we understand things better

01:20:00.320 | with these issues of self-awareness,

01:20:02.760 | and where we get, what we perceive as making choices,

01:20:06.980 | what does that really mean,

01:20:08.080 | and what's going on under the hood,

01:20:10.280 | but I'm speculating about a future understanding

01:20:15.040 | that's not in place at present.

01:20:17.000 | - Your sense there will always be,

01:20:18.800 | like as you dig into the self-awareness thing,

01:20:22.880 | there'll always be some places

01:20:24.600 | where complementarity is gonna show up.

01:20:26.640 | - Oh, definitely, yeah.

01:20:28.040 | I mean, there will be, how should I say,

01:20:31.560 | there'll be kind of a God's eye view,

01:20:33.720 | which sees everything that's going on

01:20:37.400 | in the computer or the brain,

01:20:40.120 | and then there's the brain's own view,

01:20:42.280 | or the central processor, or whatever it is,

01:20:46.240 | what we call the self, the consciousness,

01:20:50.760 | that's only aware of a very small part of it,

01:20:53.480 | and those are very different.

01:20:54.920 | So the God's eye view can be deterministic

01:20:59.680 | while the self view sees free will.

01:21:04.680 | I'm pretty sure that's how it's gonna work out, actually.

01:21:11.360 | But as it stands, free will is a concept

01:21:15.140 | that we definitely, at least I feel I definitely experience.

01:21:19.240 | I can choose to do one thing than another,

01:21:21.560 | and other people, I think, are sufficiently similar to me

01:21:24.880 | that I trust that they feel the same way.

01:21:28.380 | And it's an essential concept in psychology,

01:21:33.560 | and law, and so forth.

01:21:35.680 | But at the same time, I think that mind emerges from matter,

01:21:42.480 | and that there's an alternative description of matter

01:21:47.320 | that's up to subtleties about quantum mechanics,

01:21:51.120 | which I don't think are relevant here,

01:21:53.920 | really is deterministic.

01:21:56.140 | - Let me ask you about some particles.

01:21:57.940 | - Okay.

01:21:59.160 | - First, the absurd question,

01:22:00.840 | almost like a question that Plato would ask.

01:22:04.940 | What is the smallest thing in the universe?

01:22:08.820 | - As far as we know, the fundamental particles

01:22:13.500 | out of which we build our most successful description

01:22:17.460 | of nature are points.

01:22:20.020 | They have zero, they don't have any internal structure.

01:22:24.880 | So that's as small as can be.

01:22:29.600 | So what does that mean operationally?

01:22:33.980 | That means that they obey equations

01:22:37.980 | that describe entities that are singular concentrations

01:22:42.980 | of energy, momentum, angular momentum,

01:22:47.740 | the things that particles have,

01:22:50.140 | but localized at individual points.

01:22:53.460 | Now, that mathematical structure

01:22:57.940 | is only revealed partially in the world

01:23:01.420 | because to process the wave function

01:23:04.620 | in a way that accesses information

01:23:08.460 | about the precise position of things,

01:23:10.280 | you have to apply a lot of energy,

01:23:12.060 | and that's an idealization that you can apply

01:23:15.620 | infinite amount of energy to determine a precise position.

01:23:19.860 | But at the mathematical level,

01:23:22.420 | we build the world out of particles that are points.

01:23:26.580 | - So do they actually exist, and what are we talking about?

01:23:29.260 | - Oh, they exist.

01:23:30.100 | - So let me ask, do quarks exist?

01:23:33.000 | - Yes. (laughs)

01:23:34.980 | Do electrons exist?

01:23:36.220 | Yes.

01:23:37.060 | Do photons exist?

01:23:37.900 | Yes.

01:23:38.720 | - But what does it mean for them to exist?

01:23:39.700 | - Okay, so well, the hard answer to that,

01:23:43.520 | the precise answer is that we construct the world

01:23:48.520 | out of equations that contain entities

01:23:51.860 | that are reproducible,

01:23:56.740 | that exist in vast numbers throughout the universe,

01:24:01.940 | that have definite properties of mass, spin,

01:24:06.740 | and a few others that we call electrons.

01:24:13.380 | And what an electron is is defined by the equations

01:24:17.220 | that it satisfies, theoretically,

01:24:19.900 | and we find that there are many, many exemplars

01:24:24.180 | of that entity in the physical world.

01:24:28.860 | So in the case of electrons, we can isolate them

01:24:33.620 | and study them in individual ones in great detail,

01:24:36.740 | and we can check that they all actually are identical,

01:24:41.180 | and that's why chemistry works.

01:24:44.820 | And yes, so in that case, it's very tangible.

01:24:49.820 | Similarly with photons, you can study them individually,

01:24:53.580 | they're the units of light.

01:24:56.520 | And nowadays, it's very practical

01:24:59.900 | to study individual photons and determine their spin

01:25:04.140 | and their other basic properties

01:25:05.740 | and check out the equations in great detail.

01:25:11.100 | For quarks and gluons, which are the other two

01:25:15.300 | main ingredients of our model of matter

01:25:20.300 | that's so successful, it's a little more complicated

01:25:23.580 | because the quarks and gluons that appear in our equations

01:25:28.320 | don't appear directly as particles you can isolate

01:25:33.360 | and study individually.

01:25:35.720 | They always occur within what are called bound states

01:25:40.720 | or structures like protons.

01:25:43.960 | A proton, roughly speaking, is composed of three quarks

01:25:48.040 | and a lot of gluons, but we can detect them

01:25:50.600 | in a remarkably direct way actually nowadays,

01:25:54.400 | whereas at relatively low energies,

01:25:57.300 | the behavior of quarks is complicated,

01:26:00.820 | at high energies, they can propagate through space

01:26:05.500 | relatively freely for a while, and we can see their tracks.

01:26:10.500 | So ultimately, they get recaptured into protons

01:26:14.820 | and other mesons and funny things,

01:26:17.940 | but for a short time, they propagate freely,

01:26:21.020 | and while that happens, we can take snapshots

01:26:25.220 | and see their manifestations.

01:26:27.400 | This is actually, this kind of thing is exactly

01:26:31.660 | what I got the Nobel Prize for, predicting that this

01:26:34.060 | would work, and similarly for gluons,

01:26:36.460 | although you can't isolate them as individual particles

01:26:41.460 | and study them in the same way we study electrons,

01:26:43.860 | say, you can use them theoretically as entities

01:26:48.860 | out of which you build tangible things

01:26:56.780 | that we actually do observe, but also you can,

01:27:02.020 | at accelerators, at high energy, you can liberate them

01:27:04.880 | for brief periods of time and study how they,

01:27:07.400 | and get convincing evidence that they leave tracks

01:27:13.540 | and you can get convincing evidence that they were there

01:27:16.820 | and have the properties that we wanted them to have.

01:27:19.540 | - Can we talk about asymptotic freedom,

01:27:21.220 | this very idea that you won the Nobel Prize for?

01:27:23.940 | - Yeah.

01:27:25.260 | - So it describes a very weird effect to me,

01:27:29.620 | the weird in the following way.

01:27:33.180 | So the way I think of most forces or interactions,

01:27:39.780 | the closer you are, the stronger the effect,

01:27:43.820 | the stronger the force, right?

01:27:46.300 | With quarks, the closer they are, the less,

01:27:51.300 | so the strong interaction, and in fact,

01:27:55.380 | they basically act like free particles

01:27:58.620 | when they're very close.

01:28:00.660 | - That's right, yes.

01:28:01.900 | - But this requires a huge amount of energy.

01:28:04.560 | Like, can you describe me,

01:28:08.300 | why, how does this even work?

01:28:10.820 | (Dave laughs)

01:28:11.660 | You know how weird it is?

01:28:12.500 | - A proper description must bring in quantum mechanics

01:28:17.500 | and relativity and it's,

01:28:20.640 | so a proper description, and equations,

01:28:25.460 | so a proper description really is probably

01:28:28.660 | more than we have time for and require quite a bit

01:28:33.580 | of patience on your part.

01:28:34.900 | - How does relativity come into play?

01:28:37.660 | Wait, wait a minute.

01:28:38.500 | - Oh, relativity is important because when we talk about,

01:28:43.020 | trying to think about short distances,

01:28:51.540 | we have to think about very large momenta

01:28:55.020 | and very large momenta are connected

01:28:56.540 | to very large energy in relativity,

01:28:59.140 | and so the connection between how things behave

01:29:02.440 | at short distances and how things behave at high energy

01:29:06.140 | really is connected through relativity

01:29:09.340 | in sort of a slightly backhanded way.

01:29:12.980 | Quantum mechanics indicates that short,

01:29:16.180 | to get, to analyze short distances,

01:29:19.000 | you need to bring in probes that carry a lot of momentum.

01:29:25.120 | This again is related to uncertainty

01:29:29.140 | because it's the fact that you have to bring in

01:29:31.980 | a lot of momentum that interferes with the possibility

01:29:36.060 | of determining position and momentum at the same time.

01:29:40.220 | If you want to determine position,

01:29:42.000 | you have to use instruments that bring in a lot of momentum,

01:29:45.180 | and because of that, those same instruments

01:29:48.580 | can't also measure momentum

01:29:50.060 | 'cause they're disturbing the momentum,

01:29:51.960 | and then the momentum brings in energy, and yeah.

01:29:56.220 | So that, there's also the effect that asymptotic freedom

01:29:59.540 | comes from the possibility of spontaneously making

01:30:05.540 | quarks and gluons for short amounts of time

01:30:10.540 | that fluctuate into existence and out of existence,

01:30:15.460 | and the fact that that can be done

01:30:21.580 | with a very little amount of energy

01:30:23.780 | and uncertainty in energy

01:30:26.100 | translates into uncertainty in time.

01:30:27.580 | So if you do that for a short time, you can do that.

01:30:31.440 | Well, it all comes in a package.

01:30:34.840 | So I told you it would take a while to really explain,

01:30:39.480 | but the results can be understood.

01:30:44.080 | I mean, we can state the results pretty simply, I think.

01:30:48.120 | So in everyday life, we do encounter some forces

01:30:53.120 | that increase with distance

01:30:56.400 | and kind of turn off at short distances.

01:30:59.320 | That's the way rubber bands work, if you think about it,

01:31:02.120 | or if you pull them hard, they resist,

01:31:07.000 | but they get flabby if the rubber band is not pulled.

01:31:11.640 | And so there are, that can happen in the physical world,

01:31:17.640 | but what's really difficult is to see

01:31:19.860 | how that could be a fundamental force

01:31:21.800 | that's consistent with everything else we know,

01:31:24.400 | and that's what asymptotic freedom is.

01:31:28.480 | It says that there's a very particular kind

01:31:33.480 | of fundamental force that involves special particles

01:31:37.440 | called gluons with very special properties

01:31:40.320 | that enables that kind of behavior.

01:31:43.040 | So there were experiment, at the time we did our work,

01:31:47.340 | there were experimental indications

01:31:49.240 | that quarks and gluons did have this kind of property,

01:31:54.160 | but there were no equations that were capable

01:31:57.680 | of capturing it, and we found the equations

01:32:01.320 | and showed how they work and showed how they,

01:32:03.880 | that they were basically unique,

01:32:06.240 | and this led to a complete theory

01:32:08.320 | of how the strong interaction works,

01:32:10.000 | which is the quantum chromodynamics we mentioned earlier.

01:32:14.220 | So that's the phenomenon, that quarks and gluons

01:32:23.160 | interact very, very weakly when they're close together.

01:32:26.500 | That's connected through relativity

01:32:29.080 | with the fact that they also interact very, very weakly

01:32:32.480 | at high energies.

01:32:33.980 | So if you have, so at high energies,

01:32:36.640 | the simplicity of the fundamental interaction gets revealed.

01:32:42.200 | At the time we did our work, the clues were very subtle,

01:32:45.700 | but nowadays, at what are now high-energy accelerators,

01:32:50.100 | it's all obvious, so we would have had a much,

01:32:52.840 | well, somebody would have had a much easier time

01:32:55.500 | 20 years later looking at the data.

01:32:57.680 | You can sort of see the quarks and gluons.

01:32:59.920 | As I mentioned, they leave these short tracks

01:33:02.120 | that would have been much, much easier,

01:33:04.320 | but from indirect clues, we were able to piece together

01:33:09.320 | enough to make that behavior a prediction

01:33:13.200 | rather than a postdiction, right?

01:33:15.880 | - So it becomes obvious at high energies.

01:33:17.920 | - It becomes very obvious.

01:33:19.200 | When we first did this work, it was frontiers

01:33:23.560 | of high-energy physics, and at big international conferences,

01:33:27.740 | there would always be sessions on testing QCD

01:33:30.840 | and whether this proposed description

01:33:34.360 | of the strong interaction was, in fact, correct

01:33:36.420 | and so forth, and it was very exciting.

01:33:39.720 | But nowadays, the same kind of work,

01:33:44.720 | but much more precise with calculations

01:33:48.880 | to more accuracy and experiments

01:33:50.660 | that are much more precise and comparisons

01:33:55.320 | that are very precise.

01:33:57.140 | Now it's called calculating backgrounds

01:33:59.080 | because people take this for granted

01:34:03.000 | and wanna see deviations from the theory,

01:34:06.640 | which would be the new discoveries.

01:34:09.720 | - Yeah, the cutting edge becomes the foundation,

01:34:11.680 | the foundation becomes boring, yes.

01:34:13.560 | Is there some, for basic explanation purposes,

01:34:19.120 | is there something to be said about strong interactions

01:34:23.320 | in the context of the strong nuclear force

01:34:26.240 | for the attraction between protons and neutrons

01:34:30.800 | versus the interaction between quarks within protons?

01:34:35.360 | - Well, quarks and gluons have the same relation

01:34:40.360 | basically to nuclear physics as electrons

01:34:45.600 | and photons have to atomic and molecular physics.

01:34:49.720 | So atoms and photons are the dynamic entities

01:34:54.720 | that really come into play in chemistry and atomic physics.

01:35:01.540 | Of course, you have to have the atomic nuclei,

01:35:03.180 | but those are small and relatively inert,

01:35:07.040 | really the dynamical part.

01:35:09.400 | And for most purposes of chemistry,

01:35:12.060 | you just say you have this tiny little nucleus,

01:35:14.160 | which QCD gives you, don't worry about it, it's there.

01:35:19.160 | The real action is the electrons moving around

01:35:22.640 | and exchanging and things like that.

01:35:24.440 | But okay, but we wanted to understand the nucleus too.

01:35:29.300 | And so atoms are sort of quantum mechanical clouds

01:35:34.300 | of electrons held together by electrical forces,

01:35:38.840 | which is photons, and then there's radiation,

01:35:40.780 | which is another aspect of photons.

01:35:43.280 | - That's where all the fun happens

01:35:44.520 | is the electrons and the photons and all that kind of stuff.

01:35:46.480 | - That's right, and the nucleus are kind of the,

01:35:49.120 | well, they give the positive charge

01:35:53.880 | and most of the mass of matter,

01:35:55.720 | but they don't, since they're so heavy,

01:36:01.160 | they don't move very much in chemistry

01:36:03.760 | and I'm oversimplifying drastically.

01:36:07.920 | - They're not contributing much to the interaction

01:36:09.720 | in chemistry.

01:36:12.220 | - For most purposes in chemistry,

01:36:13.620 | you can just idealize them as concentrations

01:36:16.100 | of positive mass and charge that are,

01:36:18.700 | you don't have to look inside,

01:36:22.060 | but people are curious what's inside.

01:36:24.220 | And that was a big thing on the agenda

01:36:29.260 | of 20th century physics starting in the 19,

01:36:32.480 | well, starting with the 20th century

01:36:34.480 | and unfolding throughout of trying to understand

01:36:38.220 | what forces held the atomic nucleus together,

01:36:41.580 | what it was and so on.

01:36:42.700 | Anyway, the story that emerges from QCD

01:36:49.620 | is that very similar to the way that,

01:36:55.540 | well, broadly similar to the way that clouds of electrons

01:37:00.380 | held together by electrical forces give you atoms

01:37:04.460 | and ultimately molecules,

01:37:08.940 | protons and neutrons are like atoms

01:37:13.700 | made now out of quarks, quark clouds held together

01:37:17.780 | by gluons, which are like the photons

01:37:20.900 | that give the electric forces,

01:37:23.540 | but this is giving a different force, the strong force.

01:37:26.460 | And the residual forces between protons and neutrons

01:37:31.460 | that are left over from the basic binding

01:37:37.540 | are like the residual forces between atoms

01:37:40.060 | that give molecules, but in the case of protons and neutrons

01:37:43.500 | it gives you atomic nuclei.

01:37:45.340 | - So again, for definitional purposes,

01:37:48.340 | QCD, quantum chromodynamics,

01:37:50.940 | is basically the physics of strong interaction.

01:37:54.000 | - Yeah, we now would, I think most physicists would say

01:37:58.660 | it's the theory of quarks and gluons and how they interact.

01:38:04.220 | But it's a very precise, and I think it's fair to say

01:38:07.820 | very beautiful theory based on mathematical symmetry

01:38:11.900 | of a high order.

01:38:13.500 | And another thing that's beautiful about it

01:38:17.020 | is that it's kind of

01:38:19.180 | in the same family as electrodynamics.

01:38:26.260 | The conceptual structure of the equations are very similar.

01:38:31.180 | They're based on having particles that respond to charge

01:38:34.860 | in a very symmetric way.

01:38:37.140 | In the case of electrodynamics,

01:38:39.660 | it's photons that respond to electric charge.

01:38:42.060 | In the case of quantum chromodynamics,

01:38:44.540 | there are three kinds of charge that we call colors,

01:38:47.500 | but they're nothing like colors.

01:38:49.340 | They really are like different kinds of charge.

01:38:51.900 | - But they rhyme with the same kind of,

01:38:54.540 | like it's similar kind of dynamics.

01:38:56.580 | - Similar kind of dynamics.

01:38:58.300 | I like to say that QCD is like QED on steroids.

01:39:02.900 | And instead of one photon, you have eight gluons.

01:39:05.860 | Instead of one charge, you have three color charges.

01:39:09.140 | But there's a strong family resemblance between them.

01:39:13.140 | - But the context in which QCD does this thing

01:39:16.860 | is at much higher energies.

01:39:19.360 | Like that's where it comes to life.

01:39:20.500 | - Well, it's a stronger force.

01:39:22.300 | So that to access how it works

01:39:26.580 | and kind of pry things apart,

01:39:28.140 | you have to inject more energy.

01:39:30.380 | - And so that gives us, in some sense,

01:39:35.380 | a hint of how things were in the earlier universe.

01:39:39.460 | - Yeah, well, in that regard,

01:39:41.100 | asymptotic freedom is a tremendous blessing

01:39:43.760 | because it means things get simpler at high energy.

01:39:47.600 | - The universe was born free.

01:39:50.060 | - Born free, that's very good, yes.

01:39:52.660 | The universe was born.

01:39:53.540 | So in atomic physics,

01:39:56.060 | I mean, a similar thing happens in the theory of stars.

01:39:59.420 | Stars are hot enough that the interactions

01:40:03.420 | between electrons and photons, they're liberated.

01:40:07.540 | They don't form atoms anymore.

01:40:08.700 | They make a plasma, which in some ways

01:40:10.480 | is simpler to understand.

01:40:12.300 | You don't have complicated chemistry.

01:40:14.640 | And in the early universe, according to QCD,

01:40:18.140 | similarly, atomic nuclei dissolved

01:40:20.500 | into the constituent quarks and gluons,

01:40:22.900 | which are moving around very fast

01:40:24.460 | and interacting in relatively simple ways.

01:40:27.020 | And so this opened up the early universe

01:40:30.580 | to scientific calculation.

01:40:33.580 | - Can I ask you about some other weird particles

01:40:35.820 | that make up our universe?

01:40:37.900 | What are axions and what is the strong CP problem?

01:40:42.620 | - Okay, so let me start with what the strong CP problem is.

01:40:47.620 | First of all, well, C is charge conjugation,

01:40:53.700 | which is the transformation,

01:40:56.820 | the notional transformation, if you like,

01:40:59.940 | that changes all particles into their antiparticles.

01:41:03.380 | And the concept of C symmetry,

01:41:08.380 | charge conjugation symmetry, is that if you do that,

01:41:12.260 | you find the same laws would work.

01:41:15.420 | So the laws are symmetric.

01:41:18.380 | If the behavior that particles exhibit is the same

01:41:22.780 | as the behavior you get with all their antiparticles,

01:41:27.140 | then P is parity, which is also called spatial inversion.

01:41:33.580 | It's basically looking at a mirror universe

01:41:39.020 | and saying that the laws that are obeyed

01:41:41.900 | in a mirror universe, when you look at the mirror images

01:41:45.660 | obey the same laws as the sources of their images.

01:41:50.420 | There's no way of telling left from right, for instance,

01:41:52.820 | that the laws don't distinguish between left and right.

01:41:55.580 | Now, in the mid 20th century, people discovered

01:42:01.340 | that both of those are not quite true.

01:42:03.620 | Really, the equation, the mirror universe,

01:42:09.180 | the universe that you see in a mirror

01:42:14.180 | is not gonna obey the same laws

01:42:18.500 | as the universe that we actually exhibit and interpret.

01:42:23.500 | You would be able to tell if you did the right kind

01:42:28.300 | of experiments, which was the mirror

01:42:30.100 | and which was the real thing.

01:42:31.540 | Anyway, that--

01:42:34.820 | - So that's the parity and they show

01:42:36.060 | that the parity doesn't necessarily hold.

01:42:37.860 | - It doesn't quite hold.

01:42:39.060 | Examining what the exceptions are turned out to be,

01:42:45.660 | to lead to all kinds of insight

01:42:47.360 | about the nature of fundamental interactions,

01:42:49.820 | especially properties of neutrinos

01:42:51.600 | and the weak interaction.

01:42:52.580 | It's a long story, but it's a very--

01:42:55.460 | - So you just define the C and the P,

01:42:57.660 | the conjugation, the charged conjugation.

01:42:59.420 | - Now that I've done that, I wanna--

01:43:00.860 | - What's the problem?

01:43:01.700 | - Shove them off.

01:43:02.540 | - Okay, great.

01:43:04.020 | - 'Cause it's easier to talk about T,

01:43:06.500 | which is time reversal symmetry.

01:43:08.900 | We have very good reasons to think CPT

01:43:13.180 | is an accurate symmetry of nature.

01:43:17.140 | It's on the same level as relativity

01:43:19.360 | and quantum mechanics, basically,

01:43:20.940 | so that better be true.

01:43:22.560 | - So it's symmetric when you do conjugation,

01:43:27.140 | parity, and time.

01:43:27.980 | - And time and space reversal.

01:43:30.920 | If you do all three, then you get

01:43:32.840 | the same physical consequences.

01:43:35.000 | But that means that CP is equivalent to T.

01:43:39.680 | But what's observed in the world is that T

01:43:42.640 | is not quite an accurate symmetry of nature either.

01:43:46.680 | So most phenomena at the fundamental level,

01:43:51.680 | so interactions among elementary particles

01:43:54.660 | and the basic gravitational interaction,

01:43:57.500 | if you ran them backwards in time,

01:44:02.380 | you'd get the same laws.

01:44:05.380 | So if, again, going back,

01:44:08.400 | unless this time we don't talk about a mirror,

01:44:11.460 | but we talk about a movie,

01:44:13.180 | if you take a movie and then run it backwards,

01:44:18.180 | that's the time reversal.

01:44:20.280 | - It's cool to think about a mirror in time.

01:44:23.340 | - Yeah, it's like a mirror in time.

01:44:25.180 | If you run the movie backwards,

01:44:29.060 | it would look very strange

01:44:30.620 | if you were looking at complicated objects

01:44:32.740 | and a Charlie Chaplin movie or whatever.

01:44:37.340 | It would look very strange if you ran it backwards in time.

01:44:40.180 | But at the level of basic interactions,

01:44:43.780 | if you were able to look at the atoms

01:44:45.940 | and the quarks involved,

01:44:48.540 | they would obey the same laws

01:44:50.540 | to a very good approximation, but not exactly.

01:44:53.340 | - So not exactly, that means you could tell.

01:44:55.920 | - You could tell, but you'd have to do

01:44:57.860 | very, very subtle experiments

01:45:01.900 | with that high energy accelerators

01:45:04.660 | to take a movie that looked different

01:45:06.700 | when you ran it backwards.

01:45:08.700 | This was a discovery by two great physicists

01:45:13.700 | named Jim Cronin and Val Fitch

01:45:17.500 | in the mid 1960s.

01:45:20.540 | Previous to that, over all the centuries

01:45:22.460 | of development of physics with all its precise laws,

01:45:25.220 | they did seem to have this gratuitous property

01:45:28.880 | that they look the same if you run the equations backwards.

01:45:33.300 | It's kind of an embarrassing property actually,

01:45:35.280 | because life isn't like that.

01:45:38.500 | So empirical reality does not have this imagery

01:45:41.860 | in any obvious way, and yet the laws did.

01:45:44.900 | - It's almost like the laws of physics

01:45:46.280 | are missing something fundamental about life

01:45:48.700 | if it holds that property, right?

01:45:51.340 | - Well-- - I mean,

01:45:52.180 | that's the embarrassing nature of it.

01:45:54.340 | - Yeah, it's embarrassing.

01:45:55.220 | Well, people worked hard at what's,

01:46:00.220 | this is a problem that's thought to belong

01:46:04.780 | to the foundations of statistical mechanics

01:46:07.140 | or the foundations of thermodynamics

01:46:10.540 | to understand how behavior, which is grossly not symmetric

01:46:15.540 | with respect to reversing the direction of time

01:46:21.240 | in large objects, how that can emerge from equations

01:46:24.320 | which are symmetric with respect to changing

01:46:28.100 | the direction of time to a very good approximation.

01:46:31.060 | And that's still an interesting endeavor.

01:46:33.140 | That's interesting, and actually it's an exciting frontier

01:46:37.820 | of physics now to sort of explore the boundary

01:46:40.140 | between when that's true and when it's not true

01:46:42.300 | when you get to smaller objects

01:46:44.460 | and exceptions like time crystals.

01:46:46.520 | - I definitely have to ask you about time crystals

01:46:49.420 | in a second here, but so the CP problem and T,

01:46:53.620 | so there's flaws to all of these.

01:46:55.620 | - We're in danger of infinite regress,

01:46:57.520 | but we'll have to convert soon.

01:46:59.180 | - No, it can't possibly be turtles all the way down.

01:47:02.060 | We're gonna get to the bottom turtle.

01:47:04.020 | - So it became, so it got to be a real,

01:47:08.860 | I mean, it's a really puzzling thing

01:47:11.140 | why the laws should have this very odd property

01:47:15.300 | that we don't need, and in fact, it's kind of an embarrassment

01:47:19.940 | in addressing empirical reality,

01:47:22.140 | but it seemed to be almost,

01:47:24.620 | it seemed to be exactly true for a long time,

01:47:26.940 | and then almost true.

01:47:30.980 | And in a way, almost true is more disturbing

01:47:34.660 | than exactly true because exactly true,

01:47:37.380 | it could have been just a fundamental feature of the world,

01:47:39.780 | and at some level, you just have to take it as it is,

01:47:42.300 | and if it's a beautiful, easily articulatable regularity,

01:47:47.300 | you could say that, okay, that's fine

01:47:50.260 | as a fundamental law of nature,

01:47:51.740 | but to say that it's approximately true but not exactly,

01:47:54.220 | that's weird.

01:47:55.060 | - That's very weird.

01:47:56.420 | So, and then, so there was great progress

01:48:00.900 | in the late part of the 20th century

01:48:05.220 | in getting to an understanding

01:48:09.260 | of fundamental interactions in general

01:48:11.680 | that shed light on this issue.

01:48:13.680 | It turns out that the basic principles of relativity

01:48:19.780 | and quantum mechanics plus the kind of high degree

01:48:25.740 | of symmetry that we found, the so-called gauge symmetry

01:48:28.940 | that characterizes the fundamental interactions,

01:48:31.980 | when you put all that together,

01:48:33.800 | it's a very, very constraining framework,

01:48:36.560 | and it has some indirect consequences

01:48:40.560 | because the possible interactions are so constrained,

01:48:45.940 | and one of the indirect consequences

01:48:48.660 | is that the possibilities for violating the symmetry

01:48:54.380 | between forwards and backwards in time are very limited.

01:48:57.900 | There are basically only two, okay?

01:49:00.980 | And one of them occurs and leads to a very rich theory

01:49:05.100 | that explains the Cronin-Fitch experiment,

01:49:07.580 | and a lot of things that have been done subsequently

01:49:09.700 | has been used to make all kinds of successful predictions.

01:49:13.660 | So that's turned out to be a very rich interaction.

01:49:18.660 | It's esoteric, and the effects only show up

01:49:22.380 | at accelerators and are small,

01:49:23.740 | but they might've been very important

01:49:25.500 | in the early universe and be connected

01:49:28.700 | to the asymmetry between matter and antimatter

01:49:31.420 | in the present universe, and so on.

01:49:33.220 | But that's another digression.

01:49:35.420 | The point is that that was fine, that was a triumph

01:49:41.180 | to say that there was one possible kind of interaction

01:49:44.940 | that would violate time-reversal symmetry,

01:49:47.300 | and sure enough, there it is.

01:49:49.500 | But the other kind doesn't occur,

01:49:54.500 | so we still got a problem.

01:49:55.900 | Why doesn't it occur?

01:49:57.040 | So we're close to really finally understanding

01:50:01.780 | this profound, gratuitous feature of the world

01:50:04.740 | that is almost but not quite symmetric

01:50:08.380 | under reversing the direction of time, but not quite there.

01:50:12.260 | And to understand that last bit

01:50:18.540 | is a challenging frontier of physics today.

01:50:21.820 | And we have a promising proposal for how it works,

01:50:26.700 | which is a kind of theory of evolution.

01:50:29.940 | So there's this possible interaction,

01:50:35.600 | which we call a coupling, and there's a numerical quantity

01:50:39.100 | that tells us how strong that is.

01:50:41.460 | And traditionally in physics,

01:50:43.640 | we think of these kinds of numerical quantities

01:50:46.380 | as constants of nature that you just have to put them in,

01:50:51.380 | from experiment, they have a certain value and that's it.

01:50:57.020 | And who am I to question what God did?

01:51:02.020 | They seem to be just constants.

01:51:04.620 | But in this case, it's been fruitful to think

01:51:13.420 | and work out a theory where that strength of interaction

01:51:18.420 | is actually not a constant, it's a field.

01:51:26.980 | Fields are the fundamental ingredients of modern physics.

01:51:32.380 | Like there's an electron field, there's a photon field,

01:51:35.140 | which is also called the electromagnetic field.

01:51:37.140 | And so all of these particles are manifestations

01:51:40.180 | of different fields, and there could be a field,

01:51:45.180 | something that depends on space and time.

01:51:47.700 | So a dynamical entity instead of just a constant here.

01:51:52.700 | And if you do things in a nice way, that's very symmetric,

01:51:58.060 | very much suggested aesthetically by the theory,

01:52:02.140 | but the theory we do have, then you find that you get

01:52:09.260 | a field which as it evolves from the early universe,

01:52:14.260 | settles down to a value that's just right

01:52:22.220 | to make the laws very nearly exact,

01:52:29.460 | invariant or symmetric with respect to reversal of time.

01:52:33.580 | - It might appear as a constant,

01:52:34.740 | but it's actually a field that evolved over time.

01:52:36.580 | - It evolved over time, okay?

01:52:38.460 | But when you examine this proposal in detail,

01:52:42.140 | you find that it hasn't quite settled down to exactly zero.

01:52:47.040 | The field is still moving around a little bit.

01:52:52.020 | And because the motion is so difficult,

01:52:57.020 | the material is so rigid, and this material that fills,

01:53:02.100 | the field that fills all space is so rigid,

01:53:03.940 | even small amounts of motion can involve lots of energy.

01:53:08.180 | And that energy takes the form of particles,

01:53:13.180 | fields that are in motion are always associated

01:53:17.820 | with particles, and those are the axions.

01:53:20.500 | And if you calculate how much energy

01:53:23.340 | is in these residual oscillations,

01:53:26.060 | this axion gas that fills all the universe,

01:53:30.260 | if this fundamental theory is correct,

01:53:32.300 | you get just the right amount to make the dark matter

01:53:37.740 | that astronomers want, and it has just the right properties.

01:53:41.780 | So I'd love to believe that--

01:53:44.260 | - So that might be a thing that unlocks,

01:53:47.680 | might be the key to understanding dark matter.

01:53:50.180 | - Yeah, I'd like to think so.

01:53:51.540 | And many physicists are coming around to this point of view,

01:53:54.180 | which I've been a voice in the wilderness,

01:53:58.420 | I was a voice in the wilderness for a long time,

01:54:00.700 | but now it's become very popular, maybe even dominant.

01:54:04.660 | - So almost like, so this axion particle/field

01:54:09.660 | would be the thing that explains dark matter.

01:54:14.020 | - It explains, yeah, it would solve

01:54:15.300 | this fundamental question of, finally,

01:54:17.980 | of why the laws are almost, but not quite exactly,

01:54:22.980 | the same if you run them backwards in time,

01:54:26.540 | and then seemingly in a totally different

01:54:30.380 | conceptual universe, it would also provide,

01:54:35.260 | give us an understanding of the dark matter.

01:54:37.980 | That's not what it was designed for,

01:54:41.540 | and the theory wasn't proposed with that in mind,

01:54:45.020 | but when you work out the equations, that's what you get.

01:54:47.940 | - That's always a good sign, actually.

01:54:49.840 | (laughing)

01:54:51.020 | I think I vaguely read somewhere that there may be

01:54:54.860 | early experimental validation of axion,

01:54:59.580 | is that, am I reading the wrong?

01:55:03.100 | - Well, there have been quite a few false alarms,

01:55:05.580 | and I think there are some of them still,

01:55:08.100 | people desperately wanna find this thing,

01:55:10.140 | but I don't think any of them are convincing at this point,

01:55:15.980 | but there are very ambitious experiments,

01:55:20.460 | and you have to design new kinds of antennas

01:55:24.900 | that are capable of detecting these predicted particles,

01:55:28.300 | and it's very difficult, they interact very, very weakly.

01:55:31.340 | If it were easy, it would have been done already,

01:55:33.740 | but I think there's good hope that we can get down

01:55:38.740 | to the required sensitivity and actually test

01:55:41.700 | whether these ideas are right in coming years,

01:55:46.000 | or maybe decades.

01:55:47.380 | - And then understand one of the big mysteries,

01:55:50.420 | like literally big in terms of its fraction

01:55:53.860 | of the universe is dark matter.

01:55:55.420 | - Yes.

01:55:56.540 | - Let me ask you about, you mentioned a few times,

01:55:58.980 | time crystals, what are they?

01:56:02.820 | These things are, it's a very beautiful idea

01:56:05.340 | when we start to treat space and time

01:56:08.820 | as similar frameworks, physical phenomena.

01:56:15.100 | - Right, that's what motivated it.

01:56:17.460 | - First of all, what are crystals?

01:56:19.220 | - Yeah. - And what are time crystals?

01:56:20.460 | - Okay, so crystals are orderly arrangements

01:56:24.500 | of atoms in space, and many materials,

01:56:29.500 | if you cool them down gently,

01:56:34.140 | will form crystals, and so we say that that's

01:56:41.300 | a state of matter that forms spontaneously,

01:56:45.940 | and an important feature of that state of matter

01:56:50.220 | is that the end result, the crystal,

01:56:54.700 | has less symmetry than the equations

01:56:59.700 | that give rise to the crystal.

01:57:03.060 | So the equations, the basic equations of physics,

01:57:07.560 | are the same if you move a little bit,

01:57:12.700 | so you can move, they're homogeneous,

01:57:15.580 | but crystals aren't, the atoms are in particular places,

01:57:18.900 | though they have less symmetry.

01:57:22.520 | And time crystals are the same thing in time.

01:57:25.180 | Basically, but of course, so it's not positions of atoms,

01:57:30.180 | but it's orderly behavior that certain states of matter

01:57:35.200 | will arrange themselves into spontaneously

01:57:41.000 | if you treat them gently and let them do

01:57:45.500 | what they want to do.

01:57:46.760 | - But repeat in that same way indefinitely.

01:57:50.000 | - That's the crystalline form.

01:57:51.440 | You can also have time liquids,

01:57:54.900 | or you can have all kinds of other states of matter.

01:57:57.380 | You can also have space-time crystals

01:57:58.920 | where the pattern only repeats if,

01:58:02.640 | with each step of time, you also move it

01:58:04.600 | a certain direction in space.

01:58:07.280 | So yeah, but basically, it's states of matter

01:58:12.280 | that display structure in time spontaneously.

01:58:17.640 | - So here's the difference.

01:58:21.120 | When it happens in time,

01:58:22.760 | it sure looks a lot like it's motion,

01:58:27.760 | and if it repeats indefinitely,

01:58:29.440 | it sure looks a lot like perpetual motion.

01:58:32.000 | - Yeah.

01:58:32.840 | - Like, looks like free lunch.

01:58:35.060 | I was told that there's no such thing as free lunch.

01:58:39.240 | Does this violate laws of thermodynamics?

01:58:42.440 | - No, but it requires a critical examination

01:58:45.600 | of the laws of thermodynamics.

01:58:47.880 | I mean, let me say on background

01:58:49.800 | that the laws of thermodynamics

01:58:51.520 | are not fundamental laws of physics.

01:58:55.360 | They are things we prove under certain circumstances,

01:59:00.360 | emerge from the fundamental laws of physics.

01:59:03.000 | We don't posit them separately.

01:59:06.660 | They're meant to be deduced,

01:59:08.280 | and they can be deduced under limited circumstances,

01:59:10.560 | but not necessarily universally,

01:59:12.800 | and we're finding some of the subtleties

01:59:15.520 | and sort of except edge cases

01:59:18.320 | where they don't apply in a straightforward way,

01:59:21.040 | and this is one.

01:59:23.540 | So time crystals do obey,

01:59:27.640 | do have this structure in time,

01:59:30.360 | but it's not a free lunch,

01:59:31.960 | because although in a sense things are moving,

01:59:35.700 | they're already doing what they want to do.

01:59:39.080 | They're in there.

01:59:40.360 | So if you want to extract energy from it,

01:59:44.040 | you're gonna be foiled

01:59:44.880 | because there's no spare energy there.

01:59:48.680 | So you can add energy to it and kind of disturb it,

01:59:53.680 | but you can't extract energy from this motion

01:59:58.360 | because it wants to do,

02:00:00.400 | that's the lowest energy configuration that there is,

02:00:03.400 | so you can't get further energy out of it.

02:00:06.120 | - So in theory, I guess perpetual motion,

02:00:08.680 | you would be able to extract energy from it.

02:00:13.080 | If such a thing was to be created,

02:00:15.080 | you can then milk it for energy.

02:00:17.080 | - Well, what's usually meant in the literature

02:00:21.360 | of perpetual motion is a kind of macroscopic motion

02:00:26.360 | that you could extract energy from

02:00:29.400 | and somehow it would crank back up.

02:00:33.560 | That's not the case here.

02:00:35.160 | If you want to extract,

02:00:36.320 | this motion is not something you can extract energy from.

02:00:42.160 | If you intervene in the behavior,

02:00:45.400 | you can change it, but only by injecting energy,

02:00:48.920 | not by taking away energy.

02:00:51.120 | - You mentioned that a theory of everything

02:00:54.200 | may be quite difficult to come by.

02:00:56.480 | A theory of everything broadly defined,

02:00:58.520 | meaning truly a theory of everything.

02:01:00.760 | But let's look at a more narrow theory of everything,

02:01:03.120 | which is the way it's used often in physics,

02:01:07.160 | is a theory that unifies our current laws of physics

02:01:13.160 | general relativity, quantum field theory.

02:01:18.160 | Do you have thoughts on this dream

02:01:22.200 | of a theory of everything in physics?

02:01:25.360 | How close are we?

02:01:26.560 | Is there any promising ideas out there in your view?

02:01:29.440 | - Well, it would be nice to have.

02:01:31.080 | It would be aesthetically pleasing.

02:01:34.080 | - Will it be useful?

02:01:36.760 | - No, probably not.

02:01:38.480 | Well, I shouldn't.

02:01:41.400 | It's dangerous to say that, but probably not.

02:01:45.040 | I think we, certainly not in the foreseeable future.

02:01:50.040 | - Maybe to understand black holes?

02:01:54.240 | - Yeah, but that's, yes, maybe to understand black holes,

02:01:57.640 | but that's not useful.

02:02:00.400 | (laughing)

02:02:02.640 | And well, not only, I mean, to understand,

02:02:05.920 | it's worse, it's not useful in the sense

02:02:09.520 | that we're not gonna be basing any technology

02:02:11.960 | anytime soon on black holes,

02:02:14.200 | but it's more severe than that, I would say.

02:02:16.500 | It's that the kinds of questions about black holes

02:02:21.500 | that we can't answer within the framework of existing theory

02:02:26.480 | are ones that are not going to be susceptible

02:02:33.480 | to astronomical observation in the foreseeable future.

02:02:37.620 | They're questions about very, very small black holes

02:02:41.500 | when quantum effects come into play,

02:02:45.060 | so that black holes are, you know, not black holes.

02:02:51.720 | They're emitting this discovery of Hawking

02:02:55.360 | called Hawking radiation,

02:02:57.100 | which for astronomical black holes is a tiny, tiny effect

02:03:01.060 | that no one has ever observed.

02:03:02.900 | It's a prediction that's never been checked.

02:03:04.540 | - Like supermassive black holes that doesn't apply?

02:03:06.740 | - No, no, the predicted rate of radiation

02:03:11.220 | from those black holes is so tiny

02:03:13.580 | that it's absolutely unobservable

02:03:15.460 | and is overwhelmed by all kinds of other effects.

02:03:17.900 | So it's not practical in the sense of technology.

02:03:24.420 | It's not even practical in the sense

02:03:26.380 | of application to astronomy.

02:03:30.140 | We are existing theory of general relativity

02:03:35.980 | and quantum theory and our theory

02:03:38.980 | of the different fundamental forces

02:03:41.660 | is perfectly adequate to all problems of technology,

02:03:46.660 | for sure, and almost all problems of astrophysics

02:03:55.700 | and cosmology that appear,

02:04:03.060 | except with the notable exception

02:04:06.580 | of the extremely early universe, if you want to ask.

02:04:09.460 | What happened before the Big Bang

02:04:11.100 | or what happened right at the Big Bang,

02:04:13.060 | which would be a great thing to understand, of course.

02:04:17.340 | - Yes. - We don't.

02:04:19.180 | - But what about the engineering question?

02:04:21.140 | So if we look at space travel,

02:04:23.940 | so I think you've spoken with him, Eric Weinstein.

02:04:28.460 | - Oh, yeah. - Really,

02:04:31.900 | he says things like we want to get off this planet.

02:04:36.020 | His intuition is almost a motivator

02:04:39.140 | for the engineering project of space exploration.

02:04:42.300 | In order for us to crack this problem

02:04:44.740 | of becoming a multi-planetary species,

02:04:47.460 | we have to solve the physics problem.

02:04:49.320 | His intuition is like if we figure out

02:04:51.460 | what he calls the source code, which is like,

02:04:55.020 | a theory of everything might give us clues

02:05:00.660 | on how to start hacking the fabric of reality,

02:05:04.260 | like getting shortcuts, right?

02:05:06.500 | - It might, I can't say that it won't,

02:05:10.100 | but I can say that in the 1970s and early 1980s,

02:05:15.100 | we achieved huge steps in understanding matter.

02:05:21.340 | QCD, much better understanding of the weak interaction,

02:05:28.740 | much better understanding of quantum mechanics in general,

02:05:32.500 | and it's had minimal impact on technology.

02:05:36.500 | - On rocket design, on propulsion.

02:05:38.020 | - Certainly on rocket design, on anything,

02:05:40.300 | any technology whatsoever,

02:05:42.620 | and now we're talking about much more esoteric things,

02:05:46.360 | and since I don't know what they are,

02:05:48.780 | I can't say for sure that they won't affect technology,

02:05:51.180 | but I'm very, very skeptical

02:05:52.700 | that they would affect technology.

02:05:57.780 | Because to access them,

02:05:59.660 | you need very exotic circumstances

02:06:02.460 | to make new kinds of particles with high energy,

02:06:04.620 | you need accelerators that are very expensive,

02:06:07.860 | and you don't produce many of them, and so forth.

02:06:10.220 | It's just, it's a pipe dream, I think.

02:06:13.060 | Yeah, about space exploration.

02:06:15.380 | I'm not sure exactly what he has in mind,

02:06:18.140 | but to me, it's more a problem of,

02:06:26.700 | I don't know, something between biology and--

02:06:29.300 | - Oh yeah, automatically.

02:06:31.140 | Maybe a little AI.

02:06:33.300 | - And information processing.

02:06:35.460 | What you mean, how should I,

02:06:36.860 | I think human bodies are not well adapted to space.

02:06:42.160 | Even Mars, which is the closest thing

02:06:46.380 | to a kind of human environment

02:06:49.140 | that we're gonna find anywhere close by,

02:06:51.140 | very, very difficult to maintain humans on Mars.

02:06:56.700 | And gonna be very expensive and very unstable.

02:07:01.700 | But I think the process, however,

02:07:05.820 | if we take a broader view of what it means

02:07:10.820 | to bring human civilization outside of the Earth,

02:07:16.900 | if we're satisfied with sending minds out there

02:07:23.020 | that we can converse with, and actuators,

02:07:26.740 | and that we can manipulate,

02:07:31.260 | and sensors that we can get feedback from,

02:07:33.740 | I think that's where it's at.

02:07:37.860 | And I think that's so much more realistic.

02:07:41.540 | And I think that's the long-term future

02:07:45.780 | of space exploration.

02:07:48.140 | It's not hauling human bodies all over the place.

02:07:50.620 | That's just silly.

02:07:52.780 | - Well, it's possible that human bodies,

02:07:56.740 | so like you said, it's a biology problem.

02:07:59.060 | What's possible is that we extend human lifespan

02:08:03.500 | in some way.

02:08:04.620 | Just we have to look at a bigger picture.

02:08:07.500 | It could be just like you're saying,

02:08:09.400 | by sending robots with actuators

02:08:12.380 | and kind of extending our limbs.

02:08:16.340 | But it could also be extending some aspect of our minds,

02:08:19.140 | some information, all those kinds of things.

02:08:19.980 | - And it could be cyborgs.

02:08:21.460 | It could be--

02:08:23.820 | - Now we're talking.

02:08:24.780 | (Dave laughs)

02:08:25.620 | Now the game is fun.

02:08:26.620 | - It could be human brains or cells

02:08:31.620 | that realize something like human brain architecture

02:08:36.220 | within artificial environments,

02:08:42.780 | shells, if you like, that are more adapted

02:08:46.220 | to the conditions of space.

02:08:49.540 | So that's entirely, man-machine hybrids,

02:08:53.300 | as well as sort of remote outposts

02:08:57.940 | that we can communicate with.

02:08:59.220 | I think those will happen.

02:09:01.660 | - Yeah, to me, there's some sense in which,

02:09:05.300 | as opposed to understanding the physics

02:09:07.340 | of the fundamental fabric of the universe,

02:09:12.340 | I think getting to the physics of life,

02:09:17.360 | the physics of intelligence, the physics of consciousness,

02:09:20.820 | the physics of information that brings

02:09:24.820 | from which life emerges,

02:09:29.380 | that will allow us to do space exploration.

02:09:32.140 | - Yeah, well, I think physics in the larger sense

02:09:34.700 | has a lot to contribute here.

02:09:36.840 | Not the physics of finding fundamental new laws

02:09:39.980 | in the sense of another quark or axions even.

02:09:46.780 | But physics in the sense of,

02:09:51.420 | physics has a lot of experience

02:09:53.460 | in analyzing complex situations

02:09:56.660 | and analyzing new states of matter

02:09:58.220 | and devising new kinds of instruments

02:10:00.140 | that do clever things.

02:10:01.580 | Physics in that sense has enormous amounts

02:10:05.940 | to contribute to this kind of endeavor.

02:10:09.980 | But I don't think that looking for a so-called theory

02:10:15.620 | of everything has much to do with it at all.

02:10:19.020 | - What advice would you give to a young person today

02:10:24.020 | with a bit of fire in their eyes,

02:10:26.380 | high school student, college student,

02:10:28.100 | thinking about what to do with their life?

02:10:30.460 | Maybe advice about career

02:10:33.180 | or bigger advice about life in general?

02:10:36.220 | - Well, first, read fundamentals

02:10:38.900 | 'cause there I've tried to give some coherent,

02:10:44.820 | deep advice.

02:10:45.780 | - That's fundamentals, 10 keys to reality

02:10:48.980 | by Frank Kulczak.

02:10:50.140 | - So that's a good place to start.

02:10:50.980 | - Available everywhere.

02:10:52.260 | - If you wanna learn what I can tell you.

02:10:55.140 | - Is there an audio book?

02:10:57.740 | I've read that. - Yes, yes,

02:10:58.900 | there is an audio book. - There's an audio book.

02:10:59.980 | That's awesome.

02:11:00.820 | - Yeah, I think I can give three pieces of wise advice

02:11:05.220 | that I think are generally applicable.

02:11:08.340 | One is to cast a wide net,

02:11:13.540 | to really look around and see what looks promising,

02:11:18.540 | what catches your imagination.

02:11:21.380 | And promise, yeah, and those,

02:11:26.740 | you have to balance those two things.

02:11:28.340 | You can have things that catch your imagination,

02:11:30.020 | but don't look promising in the sense

02:11:32.340 | that the questions aren't ripe,

02:11:34.140 | and things that you,

02:11:37.820 | and part of what makes things attractive

02:11:41.180 | is that whether you thought you liked them or not,

02:11:43.900 | is if you can see that there's ferment

02:11:45.940 | and new ideas coming out,

02:11:47.140 | that's attractive in itself.

02:11:49.380 | So when I started out, I thought I was,

02:11:52.340 | and when I was an undergraduate,

02:11:53.540 | I intended to study philosophy

02:11:55.380 | or questions of how mind emerges from matter,

02:11:57.620 | but I thought that that wasn't really ripe.

02:12:00.260 | - The timing isn't right yet.

02:12:01.220 | - The timing wasn't right

02:12:02.980 | for the kind of mathematical thinking

02:12:05.220 | and conceptualization that I really enjoy and am good at.

02:12:11.220 | But, so that's one thing,

02:12:15.500 | cast a wide net, look around.

02:12:17.260 | And that's a pretty easy thing to do today

02:12:23.780 | because of the internet.

02:12:27.060 | You can look at all kinds of things.

02:12:30.020 | You have to be careful though,

02:12:30.940 | because there's a lot of crap also,

02:12:33.460 | but you can sort of tell the difference

02:12:36.580 | if you do a little digging.

02:12:39.860 | The, so don't settle on just,

02:12:44.860 | what your thesis advisor tells you to do

02:12:46.780 | or what your teacher tells you to do.

02:12:49.100 | Look for yourself and get a sense of what seems promising,

02:12:54.100 | not what seemed promising 10 years ago.

02:12:57.660 | So that's one.

02:13:03.580 | Another thing is to,

02:13:07.700 | is kind of complimentary to that.

02:13:09.940 | Well, they're all complimentary.

02:13:11.700 | Complimentary to that is to read history

02:13:17.820 | and read the masters of the history of ideas

02:13:20.980 | and masters of ideas.

02:13:22.260 | I benefited enormously from,

02:13:25.420 | as early in my career, from reading in physics,

02:13:30.420 | Einstein in the original and Feynman's lectures

02:13:36.100 | as they were coming out.

02:13:37.580 | And Darwin, you know, these,

02:13:40.500 | you can learn what it is, and Galileo,

02:13:43.500 | you can learn what it is to wrestle with difficult ideas

02:13:46.660 | and how great minds did that.

02:13:48.140 | You can learn a lot about style,

02:13:51.180 | how to write your ideas up and express them in clear ways.

02:13:56.180 | - And also just a couple of that with,

02:14:00.180 | I also enjoy reading biographies.

02:14:02.260 | - And biographies, yes, similarly, right.

02:14:04.140 | - Like, so it gives you the context

02:14:06.300 | of the human being that created those ideas.

02:14:08.900 | - Right, and brings it down to earth in the sense that,

02:14:11.820 | you know, it was really human beings who did this.

02:14:14.340 | And they made mistakes.

02:14:17.300 | I also got inspiration from Bertrand Russell,

02:14:22.940 | who was a big hero, and H.G. Wells.

02:14:24.620 | And yeah, so read the masters,

02:14:29.060 | make contact with great minds.

02:14:31.380 | And when you are sort of narrowing down on a subject,

02:14:33.820 | learn about the history of the subject

02:14:35.420 | because that really puts in context

02:14:38.340 | what you're trying to do,

02:14:39.620 | and also gives a sense of community and grandeur

02:14:44.660 | to the whole enterprise.

02:14:45.980 | And then the third piece of advice

02:14:48.860 | is complimentary to both those,

02:14:51.820 | which is sort of to get the basics under control

02:14:56.820 | as soon as possible.

02:15:00.380 | So if you want to do theoretical work in science,

02:15:04.180 | you know, you have to learn calculus,

02:15:08.380 | multivariable calculus, complex variables, group theory.

02:15:11.540 | Nowadays, you have to be highly computer literate.

02:15:15.260 | If you want to do experimental work,

02:15:16.500 | you also have to be computer literate,

02:15:17.900 | then you have to learn about electronics

02:15:19.620 | and optics and instruments and so on.

02:15:22.220 | So get that under control as soon as possible

02:15:26.820 | because it's like learning a language.

02:15:29.220 | To produce great works and express yourself fluently

02:15:34.220 | and with confidence, it should be your native language.

02:15:39.380 | These things should be like your native language.

02:15:41.380 | So you're not wondering, "Hmm, what is a derivative?"

02:15:44.660 | (laughs)

02:15:45.820 | This is just part of your, you know,

02:15:47.620 | it's in your bones, so to speak, you know?

02:15:51.860 | And the sooner that you can do that, then the better.

02:15:55.020 | So all those things can be done in parallel and should be.

02:15:57.940 | - Yeah, yeah.

02:15:59.020 | You've accomplished some incredible things in your life,

02:16:04.500 | but the sad thing about this thing we have is it ends.

02:16:09.500 | Do you think about your mortality?

02:16:15.260 | Are you afraid of death?

02:16:16.460 | - Well, afraid is the wrong word.

02:16:20.420 | I mean--

02:16:21.740 | - Let's define it then.

02:16:22.580 | - I wish it weren't gonna happen, and I'd like to, but--

02:16:27.020 | - Do you think about it?

02:16:28.900 | - Occasionally, I think about,

02:16:30.500 | well, I think about it very operationally

02:16:32.420 | in the sense that there's always a trade-off

02:16:35.520 | between exploration and exploitation.

02:16:39.520 | This is a classic subject in computer science,

02:16:42.620 | actually, in machine learning,

02:16:44.120 | that when you're in an unusual circumstance,

02:16:48.420 | you want to explore to see what the landscape is

02:16:52.580 | and gather data, but then at some point,

02:16:55.880 | you want to use that, make choices,

02:16:59.700 | and say, "This is what I'm gonna do,"

02:17:00.940 | and exploit the knowledge you've accumulated.

02:17:03.420 | And the longer the period of exploitation you anticipate,

02:17:08.420 | the more exploration you should do in new directions.

02:17:14.620 | And so for me, I've had to sort of adjust the balance

02:17:18.780 | of exploration and exploitation,

02:17:25.020 | and--

02:17:25.900 | - That's it, you've explored quite a lot.

02:17:28.180 | - Yeah, well, I haven't shut off the exploitation at all.

02:17:31.960 | I'm still hoping for--

02:17:32.800 | - The exploration.

02:17:33.960 | - The exploration, right.

02:17:35.140 | I'm still hoping for 10 or 15 years

02:17:38.240 | of top flight performance, but the...

02:17:40.920 | Several years ago now, when I was 50 years old,

02:17:46.020 | I was at the Institute for Advanced Study,

02:17:49.500 | and my office was right under Freeman Dyson's office,

02:17:52.460 | and we were kind of friendly.

02:17:53.900 | And he found out it was my 50th birthday,

02:17:58.740 | and said, "Congratulations, and you should feel liberated,"

02:18:03.020 | because no one expects much

02:18:05.020 | of a 50-year-old theoretical physicist.

02:18:07.460 | And he obviously had felt liberated

02:18:10.100 | by reaching a certain age.

02:18:13.180 | And yeah, there is something to that.

02:18:15.020 | I feel I don't have to keep in touch

02:18:21.660 | with the latest hyper-technical developments

02:18:25.020 | in particle physics or string theory or something,

02:18:27.460 | because I'm really not gonna be exploiting that.

02:18:32.560 | But I am exploring in these directions

02:18:37.620 | of machine learning and things like that.

02:18:40.940 | But I'm also concentrating within physics

02:18:43.940 | on exploiting directions that I've already established

02:18:48.020 | and the laws that we already have,

02:18:50.020 | and doing things like...

02:18:52.420 | I'm very actively involved in trying to design,

02:18:58.260 | helping people, experimentalists and engineers even,

02:19:02.620 | to design antennas that are capable of detecting axions.

02:19:07.620 | So there, and that's, there we're deep

02:19:10.940 | in the exploitation stage.

02:19:13.100 | It's not a matter of finding the new laws,

02:19:14.920 | but of really using the laws we have

02:19:17.820 | to kind of finish the story off.

02:19:20.820 | So it's complicated.

02:19:22.260 | But I'm very happy with my life right now,

02:19:27.260 | and I'm enjoying it, and I don't wanna cloud that

02:19:31.660 | by thinking too much that it's gonna come to an end.

02:19:36.660 | It's a gift I didn't earn.

02:19:42.060 | - Is there a good thing to say about why

02:19:48.020 | this gift that you've gotten and didn't deserve

02:19:51.160 | is so damn enjoyable?

02:19:53.080 | So like, what's the meaning of this thing, of life?

02:19:57.220 | - To me, interacting with people I love, my family,

02:20:01.540 | and I have a very wide circle of friends now,

02:20:04.900 | and I'm trying to produce some institutions

02:20:08.940 | that will survive me as well as my work.

02:20:14.940 | And it's just, it's, how should I say?

02:20:18.740 | It's a positive feedback work loop

02:20:22.540 | when you do something and people appreciate it,

02:20:26.340 | and then you wanna do more, and they get rewarded.

02:20:30.140 | And it's just, how should I say?

02:20:32.220 | This is another gift that I didn't earn

02:20:34.060 | and don't understand, but I have a dopamine system.

02:20:37.580 | And yeah, I'm happy to use it.

02:20:42.300 | - It seems to get energized by the creative process,

02:20:47.300 | by the process of exploration.

02:20:48.860 | - Very much so.

02:20:49.700 | - And all of that started from the little fluctuations

02:20:54.220 | shortly after the Big Bang.

02:20:58.620 | Frank, well, whatever those initial conditions

02:21:01.620 | and fluctuation did that created you, I'm glad they did.

02:21:04.580 | This was, thank you for all the work you've done,

02:21:07.620 | for the many people you've inspired, for the many,

02:21:10.100 | of the billion, most of your ideas were pretty useless

02:21:13.500 | of the several billions, as it is for all humans,

02:21:17.780 | but you had quite a few truly special ideas.

02:21:21.760 | And thank you for bringing those to the world,

02:21:23.580 | and thank you for wasting your valuable time with me today.

02:21:26.580 | It's truly an honor.

02:21:27.740 | - It's been a joy, and I hope people enjoy it.

02:21:31.780 | And I think the kind of mind expansion that I've enjoyed

02:21:37.100 | by interacting with physical reality at this deep level,

02:21:41.220 | I think can be conveyed to and enjoyed by many, many people.

02:21:45.500 | And that's one of my missions in life this year.

02:21:47.860 | - Beautiful.

02:21:49.340 | Thanks for listening to this conversation

02:21:50.860 | with Frank Wilczek, and thank you to The Information,

02:21:54.020 | NetSuite, ExpressVPN, Blinkist, and 8sleep.

02:21:58.460 | Check them out in the description to support this podcast.

02:22:01.660 | And now let me leave you with some words

02:22:03.260 | from Albert Einstein.

02:22:05.180 | "Nothing happens until something moves."

02:22:08.300 | Thanks for listening, and hope to see you next time.

02:22:12.140 | (upbeat music)

02:22:14.720 | (upbeat music)

02:22:17.300 | [BLANK_AUDIO]

Frank Wilczek: Physics of Quarks, Dark Matter, Complexity, Life & Aliens | Lex Fridman Podcast #187

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