Lisa Randall: Dark Matter, Theoretical Physics, and Extinction Events

00:00:00.000 | The following is a conversation with Lisa Rundell,

00:00:03.200 | a theoretical physicist and cosmologist at Harvard.

00:00:06.360 | Her work involves improving our understanding

00:00:08.880 | of particle physics, supersymmetry,

00:00:11.120 | baryogenesis, cosmological inflation, and dark matter.

00:00:15.600 | This is the Lex Friedman Podcast.

00:00:17.480 | To support it, please check out our sponsors

00:00:19.460 | in the description.

00:00:20.680 | And now, dear friends, here's Lisa Rundell.

00:00:23.980 | One of the things you work on and write about

00:00:27.580 | is dark matter.

00:00:29.000 | We can't see it, but there's a lot of it in the universe.

00:00:32.540 | You also end one of your books with a Beatles song quote,

00:00:36.860 | "Got to be good looking 'cause he's so hard to see."

00:00:39.520 | (Lisa laughs)

00:00:41.000 | What is dark matter?

00:00:42.600 | How should we think about it, given that we can't see it?

00:00:45.200 | How should we visualize it in our mind's eye?

00:00:47.880 | - I think one of the really important things

00:00:49.440 | that physics teaches you is just our limitations,

00:00:52.520 | but also our abilities.

00:00:54.440 | So the fact that we can deduce the existence

00:00:57.360 | of something that we don't directly see

00:00:59.720 | is really a tribute to people, that we can do that.

00:01:03.160 | But it's also something that tells you

00:01:05.360 | you can't overly rely on your direct senses.

00:01:10.160 | If you just relied on just what you see directly,

00:01:12.540 | you would miss so much of what's happening in the world.

00:01:15.460 | And we can generalize this, but just for now,

00:01:18.060 | to focus on dark matter, it's something we know is there.

00:01:21.520 | And it's not just one way we know it's there.

00:01:23.960 | In my book, Dark Matter and the Dinosaurs,

00:01:25.640 | I talk about the many different ways,

00:01:27.800 | you know, there's eight or nine,

00:01:29.280 | that we deduce not just the existence of dark matter,

00:01:32.560 | but how much is there, and they all agree.

00:01:36.440 | Now, how do we know it's there?

00:01:37.880 | Because of its gravitational force.

00:01:41.560 | And individually, a particle doesn't have

00:01:44.280 | such a big gravitational force.

00:01:45.480 | In fact, gravity is an extremely weak force

00:01:48.240 | compared to other forces we know about in nature.

00:01:51.800 | But there's a lot of dark matter out there.

00:01:53.600 | It carries a lot of energy,

00:01:54.720 | five times the amount of energy as the matter we know

00:01:57.360 | that's in atoms, et cetera.

00:01:59.440 | So, you can ask how should we think about it?

00:02:02.640 | Well, it's just another form of matter

00:02:04.860 | that doesn't interact with light,

00:02:06.680 | or at least as far as we know.

00:02:08.520 | So it interacts gravitationally, it clumps,

00:02:11.000 | it forms galaxies, but it doesn't interact with light,

00:02:15.600 | which means we just don't see it.

00:02:16.800 | And most of our detection,

00:02:18.420 | before gravitational wave detectors,

00:02:20.800 | we only saw things because of their interactions

00:02:24.160 | with light in some sense.

00:02:25.560 | - So in theory, it behaves just like any other matter,

00:02:28.840 | it just doesn't interact with light.

00:02:30.440 | - So when we say it interacts just like

00:02:32.640 | any other form of matter, we have to be careful.

00:02:35.040 | Because gravitationally, it interacts

00:02:36.920 | like other forms of matter.

00:02:38.520 | But it doesn't experience electromagnetism,

00:02:41.400 | which is why it has a different distribution.

00:02:44.040 | So in our galaxy, it's roughly spherical,

00:02:47.000 | unless it has its own interactions, that's another story.

00:02:50.800 | But we know that it's roughly spherical.

00:02:53.920 | Whereas ordinary matter can radiate and clumps into a disk.

00:02:58.920 | And that's why we see the Milky Way disk.

00:03:01.600 | So on large scales, in some sense,

00:03:04.280 | yes, all the matter is similar in some sense.

00:03:06.840 | In fact, dark matter is in some sense more important,

00:03:10.340 | because it can collapse more readily than ordinary matter,

00:03:15.340 | because ordinary matter has radiative forces,

00:03:19.120 | which makes it hard to collapse on small scales.

00:03:21.700 | So actually, it's dark matter that sort of drives

00:03:25.200 | galaxy formation, and then ordinary matter

00:03:28.000 | kind of comes along with it.

00:03:30.080 | And there's also just more of it.

00:03:31.440 | And because there's more of it,

00:03:32.400 | it can start collapsing sooner.

00:03:34.320 | That is to say, the energy density in dark matter

00:03:37.000 | dominates over radiation earlier

00:03:40.800 | than you would if you just had ordinary matter.

00:03:43.240 | - So it's part of the story of the origin of a galaxy,

00:03:45.520 | part of the story of the end of the galaxy,

00:03:47.200 | and part of the story of all the various interactions.

00:03:50.040 | - Exactly, I mean, in my book,

00:03:51.660 | I make kind of sort of jokes about,

00:03:53.980 | you know, it's like when we think about a building,

00:03:56.100 | we think about the architect,

00:03:57.260 | we think about the high level,

00:03:58.980 | but we forget about all the workers

00:04:00.280 | that did all the grunt work.

00:04:01.740 | And in fact, dark matter was really important

00:04:03.900 | in the formation of our universe,

00:04:06.180 | and we forget that sometimes.

00:04:07.620 | - That's a metaphor, on top of a metaphor.

00:04:10.920 | Okay. (Bridget laughing)

00:04:12.660 | The unheard voices that do the actual work.

00:04:16.680 | Okay. - Exactly.

00:04:17.520 | No, but it is a metaphor, but it also captures something,

00:04:19.900 | because the fact is, we don't directly see it,

00:04:22.660 | so we forget it's there,

00:04:24.460 | or we don't understand it's there, or we think it's not.

00:04:27.220 | The fact that we don't see it makes it no less legitimate.

00:04:30.300 | It just means that we have challenges

00:04:32.740 | in order to find out exactly what it is.

00:04:35.340 | - Yeah, but the things we cannot see

00:04:37.960 | that nevertheless have gravitational interaction

00:04:41.340 | with the things we can see is,

00:04:43.100 | at the layman level,

00:04:47.940 | it's just mind-blowing.

00:04:50.620 | - It is, and it isn't,

00:04:51.980 | because I think what it's teaching us is that we're human.

00:04:56.300 | The universe is what it is,

00:04:58.060 | and we're trying to interact with that universe

00:05:00.420 | and discover what it is.

00:05:01.460 | We've discovered amazing things.

00:05:03.780 | In fact, I would say it's more surprising

00:05:06.580 | that the matter that we know about

00:05:08.700 | constitutes as big a fraction of the universe as it does.

00:05:12.580 | I mean, we're limited, we're human.

00:05:14.700 | And the fact that we see 5% of the energy density

00:05:18.340 | of the universe,

00:05:19.180 | about 1/6 of the energy density of matter,

00:05:22.540 | that's kind of remarkable.

00:05:23.780 | I mean, why should that be?

00:05:25.060 | There could be anything, anything could be out there,

00:05:27.540 | yet the universe that we see is a significant fraction.

00:05:30.900 | - Yeah, but a lot of our intuition, I think,

00:05:33.220 | operates using visualizations in the mind.

00:05:36.140 | - That's absolutely true,

00:05:37.460 | and it's certainly writing books I realized.

00:05:39.860 | Also, how many of our words are based

00:05:41.620 | on how we see the world.

00:05:43.920 | And that's true, and that's actually

00:05:46.660 | one of the fantastic things about physics

00:05:48.500 | is that it teaches you how to go beyond

00:05:51.000 | your immediate intuition to develop intuitions

00:05:53.840 | that apply at different distances, different scales,

00:05:56.560 | different ways of thinking about things.

00:05:57.980 | - Yeah, how do you anthropomorphize dark matter?

00:06:00.380 | - I just did, I think.

00:06:02.720 | I made it the grant workers.

00:06:04.400 | - Oh yeah, that's good.

00:06:05.400 | Yeah, you did.

00:06:06.840 | That's why you get paid the big bucks

00:06:08.640 | with the big bucks, and write the great books.

00:06:11.000 | Okay, so you also write in that book

00:06:14.280 | about dark matter having to do something

00:06:18.240 | with the extinction events, the extinction of the dinosaurs,

00:06:21.920 | which is kind of a fascinating presentation

00:06:26.680 | of how everything is connected.

00:06:28.340 | So I guess the disturbances from the dark matter,

00:06:33.340 | they create gravitational disturbances in the Oort cloud

00:06:36.040 | at the edge of our solar system,

00:06:37.800 | and then that increases the rate of asteroids

00:06:40.640 | hitting Earth.

00:06:41.840 | - So I want to be really clear.

00:06:43.840 | This was a speculative theory.

00:06:45.520 | - Love it, though.

00:06:47.480 | - I mean, and I liked it, too,

00:06:49.480 | and we still don't know for sure,

00:06:52.680 | but we can, what we liked about it,

00:06:55.720 | so let me take a step back.

00:06:57.440 | So we usually assume that dark matter,

00:07:00.320 | we being physicists, that it's just one thing.

00:07:02.840 | It's just basically non-interacting,

00:07:05.360 | aside from gravity, or very weakly interacting matter.

00:07:10.360 | But again, we have to get outside the mindset

00:07:13.480 | of just humans and ask, what else could be there?

00:07:16.400 | And so what we suggested is that there's a fraction

00:07:19.900 | of dark matter, not all the dark matter,

00:07:22.040 | but some of the dark matter,

00:07:23.080 | maybe it has interactions of its own.

00:07:25.520 | Just the same way in our universe,

00:07:27.760 | we have lots of different types of matter.

00:07:29.720 | We have nuclei, we have electrons, we have forces.

00:07:33.920 | It's not a simple model, the standard model,

00:07:37.920 | but it does have some basic ingredients.

00:07:40.400 | So maybe dark matter also has

00:07:41.960 | some interesting structure to it.

00:07:44.680 | So maybe there's some small fraction.

00:07:46.840 | And the interesting thing is that

00:07:49.320 | if some of the dark matter does radiate,

00:07:51.960 | and I like to call it dark light,

00:07:54.120 | because it's light that we don't see,

00:07:56.040 | but dark matter would see, it could radiate that,

00:07:59.440 | and then it could perhaps collapse into a disk

00:08:01.840 | the same way ordinary matter collapsed

00:08:04.600 | into the Milky Way disk.

00:08:06.120 | So it's not all the dark matter, it's a fraction.

00:08:08.840 | But it could conceivably be a very thin disk of dark matter,

00:08:12.480 | thin, dense disk of dark matter.

00:08:14.960 | And so then the question is, do these exist?

00:08:16.800 | And people have done studies now

00:08:19.080 | to think about whether they can find them.

00:08:21.560 | I mean, it's an interesting target,

00:08:22.840 | it's something you can measure.

00:08:24.300 | By measuring the positions and velocities of stars,

00:08:26.720 | you can find out what the structure of the Milky Way is.

00:08:30.440 | But the fun proposal was that

00:08:33.800 | the solar system orbits around the galaxy.

00:08:36.440 | And as it does so, it goes a little bit up and down,

00:08:39.200 | kind of like horses on a carousel.

00:08:41.280 | And the suggestion was every time it goes through,

00:08:43.080 | you have an enhanced probability

00:08:45.600 | that you would dislodge something

00:08:47.600 | from the edge of the solar system,

00:08:49.280 | in something called the Oort Cloud.

00:08:51.040 | So the idea was that at those times,

00:08:52.800 | you're more likely to have these cataclysmic events,

00:08:55.800 | such as the amazing one that actually caused

00:08:59.000 | the last extinction that we know of, for sure.

00:09:01.680 | - It wasn't so amazing for the dinosaurs.

00:09:04.240 | - Or for 2/3 of the species on the planet.

00:09:06.440 | - Yeah, but it's amazing for humans, it wouldn't be--

00:09:08.760 | - What really is amazing, I mean, I talk about this

00:09:12.160 | in "Dark Matter and the Dinosaurs."

00:09:13.280 | It's just an amazing scientific story,

00:09:15.800 | because it really is one of the real stories

00:09:18.120 | that combine together different fields of science.

00:09:20.720 | Geologists at the time, or, you know,

00:09:23.760 | people thought that things happened slowly,

00:09:25.520 | and this would be a cataclysmic event.

00:09:27.440 | And also, I have to say, if you think about it,

00:09:30.080 | it sounds like a story like a five-year-old would make up.

00:09:32.440 | Maybe the dinosaurs were killed by some big rock

00:09:34.760 | that came and hit the Earth,

00:09:36.720 | but then there really was a scientific story behind it.

00:09:40.400 | And that's also why I like the dark disc,

00:09:41.840 | 'cause there's a scientific story behind it.

00:09:43.720 | So as far-fetched as it might sound,

00:09:45.840 | you could actually go and look for

00:09:47.400 | the experimental consequences,

00:09:48.840 | or the observational consequences,

00:09:50.320 | to test whether it's true.

00:09:52.000 | - I wish you could know high-resolution details

00:09:56.420 | of where that asteroid came from,

00:09:58.880 | like where in the Oort cloud, why it happened,

00:10:01.400 | is it in fact because of dark matter?

00:10:03.120 | Just like the full tracing back

00:10:04.440 | to the origin of the universe.

00:10:06.640 | Humans seem to be somewhat special,

00:10:09.080 | but it just, it seems like so many fascinating events

00:10:11.680 | at all scales of physics had to happen for--

00:10:16.080 | - So I'm really, really glad you mentioned that,

00:10:18.080 | because actually, that was one of the main points

00:10:20.520 | of my book, Dark Matter and the Dinosaurs.

00:10:22.340 | One of the reasons I wrote it was because

00:10:24.920 | I really think we are abusing the planet,

00:10:26.760 | we're changing the planet way too quickly.

00:10:28.920 | And just like anything else, when you alter things,

00:10:30.880 | it's good to think about the history

00:10:32.200 | of what it took to get here.

00:10:33.920 | And as you point out, it took many operations

00:10:37.700 | on many different scales.

00:10:39.480 | We had to have the formation of structure,

00:10:41.800 | the formation of galaxies,

00:10:43.080 | the formation of the solar system,

00:10:44.440 | the formation of our planet, the formation of humans.

00:10:46.640 | I mean, there's so many steps that go into this.

00:10:49.280 | And humans, in some part, were the result

00:10:51.560 | of the fact that this big object hit the Earth,

00:10:54.680 | made the dinosaurs go extinct, and mammals developed.

00:10:57.320 | I mean, it is an incredible story.

00:10:59.200 | And yes, something else might come of it,

00:11:02.520 | but it won't be us if we mess with it too much.

00:11:05.520 | - But it is, on a grand scale,

00:11:07.840 | Earth is a pretty resilient system.

00:11:10.940 | Can you just clarify, it's just fascinating,

00:11:15.520 | the shape of things.

00:11:18.280 | So the shape of the Milky Way,

00:11:20.440 | of the observable stuff is mostly flat.

00:11:24.520 | And you said dark matter tends to be spherical,

00:11:27.840 | but a subset of that might be a flat disk.

00:11:31.560 | - So you wanted to hear about the shape of things.

00:11:33.440 | - Yes, please.

00:11:35.520 | - So structure formed early on,

00:11:37.840 | and now our structure that we live in,

00:11:40.040 | so we know about the Milky Way galaxy.

00:11:43.360 | So the Milky Way galaxy has the disk you can see

00:11:46.760 | in a dry, dark place.

00:11:48.960 | That's where stars and light is.

00:11:51.840 | But you can also measure, in some ways, the dark matter.

00:11:56.840 | And we believe that dark matter

00:11:59.560 | is more or less spherically distributed.

00:12:01.560 | And like we said, there's a lot of it.

00:12:05.280 | Not necessarily in the disk,

00:12:06.720 | but just because it's a sphere,

00:12:08.160 | there's a lot of it sitting there.

00:12:10.200 | And the reason it doesn't collapse, as far as we know,

00:12:14.120 | is that it can't radiate the same way.

00:12:16.960 | So because it can radiate, ordinary matter collapses.

00:12:19.400 | And it's actually because

00:12:20.880 | of conservation of angular momentum.

00:12:22.920 | It stays a disk, and it doesn't just collapse to the center.

00:12:26.440 | So our suggestion was that maybe there are some components

00:12:30.160 | of dark matter that also radiate.

00:12:31.780 | Like I said, that's far from proven.

00:12:33.360 | People have looked for a disk.

00:12:34.480 | They see some evidence of some disks of certain densities.

00:12:37.880 | But these are all questions that are worth asking.

00:12:40.580 | Basically, if we can figure it out

00:12:42.400 | from existing measurements, why not try?

00:12:44.680 | - Okay, so there's not all dark matter is made the same.

00:12:47.960 | - Well, that's a possibility.

00:12:49.720 | We actually don't know what dark matter is

00:12:51.960 | in the first place.

00:12:52.800 | We don't know what most of it is.

00:12:53.840 | We don't know what a fraction is.

00:12:55.200 | I mean, it's hard to measure.

00:12:56.480 | Why is it hard to measure?

00:12:57.400 | For exactly the reason you said earlier, we don't see it.

00:13:00.580 | So we wanna think of possibilities for what it can be,

00:13:03.680 | especially if those give rise

00:13:06.400 | to some observational consequences.

00:13:08.760 | I mean, it's a tough game,

00:13:10.120 | because it's not something that's just there for the taking.

00:13:13.780 | You have to think about what it could be

00:13:15.040 | and how you might find it.

00:13:16.240 | - And the way you detect it is gravitational effects

00:13:19.680 | on things we can see.

00:13:22.000 | - That would be the way you detect the type of dark matter

00:13:24.280 | I've been talking about.

00:13:25.520 | People have suggestions for other forms of dark matter.

00:13:28.600 | They could be particles called axions.

00:13:30.440 | They could be other types of particles.

00:13:32.360 | And then there are different ways of detecting it.

00:13:33.920 | I mean, the most popular candidate for dark matter,

00:13:36.960 | probably until pretty recently, because they haven't found it,

00:13:39.800 | is something called WIMPs,

00:13:40.880 | weakly interacting massive particles,

00:13:43.380 | particles that have mass about the same

00:13:45.320 | as the Higgs boson mass.

00:13:46.720 | And it turns out then you would get

00:13:49.120 | about the right density of dark matter.

00:13:51.320 | But then people really like that, of course,

00:13:53.560 | because it is connected to the standard model,

00:13:56.440 | the particles that we know about.

00:13:58.440 | And if it's connected to that,

00:13:59.920 | we have a better chance of actually seeing it.

00:14:02.040 | Fortunately or unfortunately,

00:14:03.040 | it's also a better chance that you can rule it out,

00:14:04.680 | because you can look for it.

00:14:05.920 | And so far, no one has found it.

00:14:07.200 | We're still looking for it.

00:14:08.240 | - Is that one of the hopes of the Large Hadron Collider?

00:14:11.840 | - That was originally one of the hopes

00:14:13.320 | of the Large Hadron Collider.

00:14:14.800 | I'd say at this point, it would be very unlikely,

00:14:18.120 | given what they've already accomplished.

00:14:21.200 | But there are these underground detectors,

00:14:24.520 | xenon detectors that look for dark matter coming in.

00:14:28.160 | And they are going to try to achieve

00:14:32.160 | a much stronger bound than exists today.

00:14:35.080 | - Just to take that tangent, looking back now,

00:14:38.040 | what's the biggest, to you, insight to humanity

00:14:44.120 | that the LHC has been able to provide?

00:14:47.640 | - It's interesting.

00:14:48.480 | It's both a major victory.

00:14:50.840 | The Higgs boson was proposed 50 years ago,

00:14:54.120 | and it was discovered.

00:14:55.640 | The Higgs mechanism seemed to be the only way

00:14:57.700 | to explain elementary particle masses, and it was right.

00:15:00.760 | So on the one hand, it was a major victory.

00:15:03.000 | On the other hand, I've been in physics long enough

00:15:04.760 | to know it was also a cautionary tale in some sense,

00:15:07.920 | because at the time I started out in physics,

00:15:11.120 | we had proposed something in the United States

00:15:12.920 | called the superconducting supercollider.

00:15:15.640 | A lot of physicists, I'll say particularly in Europe,

00:15:18.360 | but I'd say a lot of physicists,

00:15:20.240 | were saying when that the Large Hadron Collider

00:15:22.760 | would have the energy reach necessary

00:15:25.300 | to discover what underlies the standard model.

00:15:27.520 | We don't want to just discover the standard model,

00:15:29.000 | we want to know what the next step is.

00:15:30.920 | And I think here, people were more cautious about that.

00:15:34.200 | They wanted to have a more comprehensive search

00:15:36.600 | that could get to higher energies, more events,

00:15:39.280 | so that we could really more definitively rule it out.

00:15:43.040 | But in that case, many people thought

00:15:45.000 | they knew what would be there.

00:15:45.960 | It happened to be a theory called supersymmetry,

00:15:48.120 | so a lot of physicists thought it would be supersymmetry.

00:15:51.080 | I mean, it's one of the many factors, I think,

00:15:52.980 | that went into the fact that the Large Hadron Collider

00:15:55.400 | became the only machine in town.

00:15:57.280 | And the superconducting supercollider,

00:16:00.080 | would have just been a much,

00:16:01.160 | if it really had achieved what it was supposed to,

00:16:03.580 | would have been a much more robust test of the space.

00:16:07.000 | So I'd say for humanity, it's both a tribute

00:16:10.800 | to the ability of discovery

00:16:12.560 | and the ability of really believing in things,

00:16:14.800 | so that you have the confidence to go look for them.

00:16:16.880 | But it's also a cautionary tale that you don't want to,

00:16:20.000 | you know, assume things before they've been actually found.

00:16:23.900 | So you want to do things,

00:16:25.000 | and you want to believe in your theories,

00:16:27.660 | but you also want to question them at the same time,

00:16:29.840 | in ways that you're more likely to discover the truth.

00:16:32.480 | - But it's also an illustration of grand engineering efforts

00:16:36.240 | that humanity can take on,

00:16:38.280 | and maybe a lesson that you could go even bigger.

00:16:41.900 | - I'm really glad you said that, though, too,

00:16:44.840 | because that's absolutely true.

00:16:46.960 | I mean, it really is an impressive,

00:16:49.840 | it's impressive in so many ways.

00:16:51.640 | It's impressive technologically,

00:16:53.240 | it's impressive at an engineering level.

00:16:55.120 | It's also impressive that so many countries work together

00:16:58.160 | to do this, it wasn't just one country.

00:17:01.980 | And how it was, it was also impressive in that

00:17:04.540 | it was a long-term project that people committed to

00:17:07.280 | and made it happen.

00:17:09.320 | So it is a demonstration that when people

00:17:12.840 | set their minds to things and they commit to it,

00:17:16.200 | that they can do something amazing.

00:17:18.080 | - But also, in the United States,

00:17:20.400 | maybe a lesson that bureaucracy can slow things down.

00:17:23.880 | - Bureaucracy and politics. - Politics.

00:17:27.160 | - And economics, many, many things can make them faster

00:17:30.840 | and make them slower.

00:17:32.240 | So science is the way to make progress,

00:17:34.420 | politics is the way to slow that progress down.

00:17:38.240 | And here we-- - Well, I don't wanna

00:17:39.560 | overstate that because without politics,

00:17:41.560 | the LHC wouldn't happen either. - No, we need it.

00:17:44.900 | - But-- - You need broccoli.

00:17:47.080 | - But sometimes I do think, I mean,

00:17:52.040 | you're not asking this question,

00:17:53.260 | but sometimes I do think when I think about

00:17:56.640 | some of these conflicts, sometimes it's just good

00:18:00.520 | to have a project that people work on together.

00:18:03.520 | And there were some efforts to do that in science too,

00:18:07.800 | to have Palestinians and Israelis work together,

00:18:10.760 | project called Sesame.

00:18:12.080 | I think it's not a bad idea when you can do that,

00:18:15.320 | when you can get, you know, sort of forget the politics

00:18:20.320 | and just focus on some particular project,

00:18:23.760 | sometimes that can work.

00:18:25.200 | - Some kind of forcing function, some kind of deadline

00:18:27.440 | that gets people to sit in a room together,

00:18:29.280 | and you're working on a thing, but as part of that,

00:18:32.640 | you realize the common humanity,

00:18:35.720 | that you all have the same concerns, the same hopes,

00:18:38.200 | the same fears, the same, that you are all human.

00:18:41.040 | And that's an accidental side effect

00:18:43.080 | of working together on a thing.

00:18:45.400 | - That's absolutely true, and it's one of the reasons

00:18:47.000 | CERN was formed, actually.

00:18:48.560 | It was post-World War II, and a lot of European physicists

00:18:51.800 | had actually left Europe, and they wanted to see

00:18:54.480 | Europeans work together and sort of rebuild.

00:18:57.560 | And it worked, I mean, they did.

00:19:00.680 | And it's true, I often think that one of the major problems

00:19:04.800 | is we just don't meet enough people,

00:19:06.880 | so that everyone thinks, when they seem like the other,

00:19:09.560 | it's more easy to forget their humanity.

00:19:12.200 | So I think it is important to have these connections.

00:19:15.040 | - Given the complexity, all cosmological scales involved here

00:19:21.120 | that led to the extension of the dinosaurs,

00:19:23.760 | when you look out at the future of Earth,

00:19:26.800 | do you worry about future extinction events?

00:19:29.800 | - I do think that we might be in the middle

00:19:31.760 | of an extinction right now, if you define it

00:19:34.360 | by the number of species that are getting killed off.

00:19:37.160 | And it's subtle, but it's a complex system.

00:19:40.880 | The way things respond to events is sometimes things evolve,

00:19:45.800 | sometimes animals just move to another place.

00:19:48.460 | And the way we've developed the Earth,

00:19:50.600 | it's very hard for species just to move somewhere else.

00:19:54.400 | And we're seeing that with people now too.

00:19:57.520 | I mean, I know people are worried just about AI taking over,

00:20:00.360 | and that's a totally different story.

00:20:02.400 | We just don't think about the future very much,

00:20:04.720 | we think about what we're doing now.

00:20:06.160 | And we certainly don't think enough about all the animals

00:20:09.160 | that we're destroying, all the things that are precursors

00:20:11.720 | to humans that we sort of rely on.

00:20:13.460 | - It's interesting to think whether the things

00:20:18.680 | that threaten us is the stuff we see

00:20:21.920 | that's happening gradually, or the stuff we don't really see

00:20:25.120 | that's gonna happen all of a sudden.

00:20:27.040 | I sometimes think about what should we be more worried about?

00:20:32.040 | 'Cause it seems like with asteroids or nuclear war,

00:20:35.280 | it could be stuff that just happens one day.

00:20:38.360 | When I say one day, meaning over a span

00:20:41.520 | of a few days or a few months,

00:20:43.920 | but not on a scale of decades and centuries.

00:20:48.100 | 'Cause we sometimes mostly talk about stuff

00:20:51.880 | that's happening gradually.

00:20:54.640 | But you can be really surprised.

00:20:56.840 | - It's actually really interesting,

00:20:58.720 | and that was actually one of the reasons

00:21:00.680 | it took a while to determine what it was

00:21:03.320 | that had caused the last extinction.

00:21:04.600 | Because people did think at the time,

00:21:07.120 | many people thought that things were more gradual.

00:21:09.420 | And the idea of extinction was actually a novel concept

00:21:12.640 | at some point.

00:21:14.280 | I mean, these aren't predictable events necessarily,

00:21:17.040 | they're only predictable on a grand scale.

00:21:19.800 | But sometimes they are.

00:21:21.760 | And I think people were pretty aware

00:21:26.760 | that nuclear weapons were dangerous.

00:21:29.480 | I'm not sure people are as aware now

00:21:31.560 | as they were say 20 or 30 years ago.

00:21:34.520 | And that certainly worries me.

00:21:36.320 | I have to say I was not as worried about AI as other people,

00:21:41.120 | but now I understand.

00:21:42.760 | And it's not, I mean, it's more that

00:21:45.660 | as soon as you create things that we lose control over,

00:21:49.360 | it's scary.

00:21:50.200 | And the other thing that we're learning

00:21:51.960 | from the events today is that it takes a few bad actors.

00:21:55.560 | It takes everyone to sort of make things work well.

00:21:59.180 | It takes not that many things to make things go wrong.

00:22:01.800 | It's the issue with disease.

00:22:03.600 | We can find out what causes a disease,

00:22:05.760 | but to make things better is not necessarily that simple.

00:22:08.800 | Sometimes it is.

00:22:10.220 | But for things to be healthy, a lot of things have to work.

00:22:13.640 | For things to go wrong, only one thing has to go wrong.

00:22:16.840 | And so it's amazing that we do it.

00:22:19.320 | And the same is true for democracy.

00:22:20.800 | For democracy to work,

00:22:21.760 | a lot of people have to believe in it.

00:22:23.440 | A few bad actors can destroy things sometimes.

00:22:27.000 | So a lot of the things that we really rely on

00:22:30.760 | are delicate equilibrium situations.

00:22:33.560 | And there is some robustness in the systems.

00:22:36.400 | We try to build in robustness,

00:22:38.440 | but a few extreme events can sometimes alter things.

00:22:41.440 | And I think that's what people are scared of today

00:22:45.800 | in many ways.

00:22:46.640 | They're scared of it for democracy.

00:22:47.760 | They're scared of it for peace.

00:22:49.320 | They're scared of it for AI.

00:22:51.000 | I think they're not as scared as they should be

00:22:52.720 | about nuclear weapons, to be honest.

00:22:55.320 | I think that's a more serious danger than people realize.

00:22:58.120 | I think people are a little bit more scared about pandemics

00:23:02.000 | than they were before,

00:23:03.640 | but I still say they're not super scared about it.

00:23:06.400 | So you're right.

00:23:07.340 | There are these major events that can happen,

00:23:10.800 | and we are setting things up so that they might happen.

00:23:14.320 | And we should be thinking about them.

00:23:16.200 | The question is, who should be thinking about them?

00:23:18.200 | How should we be thinking about them?

00:23:19.400 | How do you make things happen on a global scale?

00:23:21.800 | 'Cause that's really what we need.

00:23:23.400 | - It certainly shouldn't be a source of division.

00:23:25.360 | It should be a source of grand collaboration, probably.

00:23:29.160 | - Wouldn't that be nice?

00:23:30.560 | - Yeah.

00:23:31.400 | I just wonder what it'd be like to be a dinosaur.

00:23:34.440 | It must have been beautiful to look at the asteroid

00:23:37.440 | just enter the atmosphere.

00:23:39.520 | Until everything just, man, would I...

00:23:43.840 | That'd be one of the things I would travel back in time to.

00:23:47.100 | It's just to watch it. - That's also one

00:23:49.320 | of the things that I think you probably could do

00:23:51.640 | with virtual reality.

00:23:52.680 | I don't think you have to be there and get extinct.

00:23:54.440 | - To just experience it.

00:23:55.680 | - I think there's something, it's an event,

00:23:57.240 | you're just watching, you're not doing anything,

00:23:58.760 | you're just looking at it.

00:24:00.080 | So maybe you could just recreate it.

00:24:01.720 | - I actually heard that there's a nuclear weapon

00:24:05.280 | explosion experience in virtual reality

00:24:07.920 | that's good to remind you about what it would feel like.

00:24:13.200 | I have to say, I got an award from the Museum of Nuclear

00:24:17.480 | History and Technology in the Southwest,

00:24:20.440 | and I went to visit the museum,

00:24:22.200 | which turned out to be mostly a museum of nuclear weapons.

00:24:26.120 | And the scary thing is that they look really cool.

00:24:30.120 | It's true that you have that, yes, this is scary,

00:24:32.920 | but you also have this, this is cool feeling.

00:24:35.160 | And I think we have to get around that

00:24:37.360 | because I kind of think that, yes, you can be in that,

00:24:40.840 | but I'm not sure that's going to make people scared.

00:24:44.000 | Have they actually asked afterwards,

00:24:46.000 | are you more or less scared?

00:24:48.000 | - That's a good, it's a really good point.

00:24:51.680 | I mean, that's a good summary of just humanity in general.

00:24:54.760 | We're attracted to creating cool stuff,

00:24:59.460 | even though it can be dangerous.

00:25:01.120 | - And actually, that was the really interesting thing

00:25:02.960 | about visiting that museum, actually.

00:25:04.440 | It was very nice 'cause I had a tour from people

00:25:06.120 | who had been working there in the Cold War,

00:25:08.040 | and actually one or two people from the Manhattan Project.

00:25:10.520 | It was a very cool tour.

00:25:12.320 | And you just realize just how,

00:25:14.680 | just the thing itself gets you so excited.

00:25:16.880 | I think that's something that sometimes these movies miss,

00:25:19.080 | just the thing itself.

00:25:20.160 | You're not thinking about the overall consequences.

00:25:23.600 | And it was kind of like, in some ways,

00:25:24.920 | it was like the early Silicon Valley.

00:25:27.040 | People were just thinking, what if we did this?

00:25:28.740 | What if we did that?

00:25:30.240 | And not keeping track of what the peripheral consequences are.

00:25:35.000 | And you definitely see that happening with AI now.

00:25:37.580 | I mean, I think that was the moral of the battle

00:25:39.520 | that just happened, that it's just full speed ahead.

00:25:43.160 | - Which gives me a really great transition

00:25:46.480 | to another quote in your book.

00:25:49.000 | So you write about the experience

00:25:50.760 | of facing the sublime in physics.

00:25:53.600 | And you quote Ryan Aroque,

00:25:56.080 | quote, "For beauty is nothing but the beginning of terror,

00:26:00.920 | "which we are still just able to endure,

00:26:03.560 | "and we're so awed because it serenely disdains

00:26:07.120 | "to annihilate us."

00:26:08.920 | That's pretty intense.

00:26:10.560 | I think applies to nuclear weapons.

00:26:12.880 | - But it also, I mean, at a more mundane, perhaps, level,

00:26:17.600 | I think it applies, it's really interesting.

00:26:20.360 | One of the things I found when I wrote these books

00:26:23.000 | is some people love certainty.

00:26:26.960 | Scientists, many revel in uncertainty.

00:26:30.240 | It's not that you wanna be uncertain, you wanna solve it.

00:26:33.080 | But you're at this edge where it's really frustrating,

00:26:35.280 | because you don't really wanna not know the answer.

00:26:37.680 | But of course, if you knew the answer,

00:26:39.240 | that would be, it would be done.

00:26:41.320 | So you're always at this edge

00:26:42.960 | where you're trying to sort things out.

00:26:45.640 | And there is something scary.

00:26:47.080 | You don't know what is,

00:26:47.920 | you don't know if there's gonna be a solution.

00:26:49.160 | You don't know if you're going to find it.

00:26:50.720 | So it's not something that can destroy the Earth.

00:26:52.280 | It's just something that you do on your individual level.

00:26:55.520 | But then, of course, there are much bigger things,

00:26:57.600 | like the ones you're talking about,

00:26:59.200 | where they could actually be dangerous.

00:27:01.000 | The stuff I do, I just wanna be clear,

00:27:02.680 | I'm doing theoretical physics, not very dangerous.

00:27:05.800 | But sometimes things end up having

00:27:08.160 | bigger consequences than you think.

00:27:10.240 | - Yeah, but dangerous in a very pragmatic sense.

00:27:15.240 | But isn't it still, in part, terrifying

00:27:17.720 | when you think of just the size of things?

00:27:22.400 | Like the size of dark matter,

00:27:23.920 | like the power of this thing,

00:27:26.440 | in terms of its potential gravitational effects.

00:27:30.280 | Just this cosmological objects,

00:27:33.160 | a black hole at the center of our galaxy.

00:27:36.360 | - So this might be why I'm a physicist,

00:27:38.120 | or why I differ from other people.

00:27:39.720 | Because I'm not such a big fan of humanity in some ways.

00:27:44.480 | Some ways I am.

00:27:45.520 | But the idea that we were everything

00:27:46.880 | would be really boring to me.

00:27:48.480 | I love the idea that there's so much more out there,

00:27:50.680 | that there's a bigger universe,

00:27:51.880 | and there's lots to discover,

00:27:53.280 | and that we're not all there is.

00:27:55.400 | Wouldn't it be disappointing if we were all there is?

00:27:57.880 | - Yeah, and the full diversity of other stuff.

00:28:02.720 | It's pretty interesting.

00:28:04.160 | - We have no idea how much there is.

00:28:05.960 | We know what we can observe so far.

00:28:08.360 | So the idea that there's other stuff out there

00:28:10.440 | that we yet have to figure out, it's exciting.

00:28:13.440 | - Well, let me ask you an out there question.

00:28:16.120 | - Uh-oh.

00:28:16.960 | - Okay.

00:28:18.120 | So if you think of humans on Earth, life on Earth,

00:28:22.800 | as this pocket of complexity that emerged.

00:28:26.640 | And there's a bunch of conditions that came to be,

00:28:29.680 | and there's Darwinian evolution,

00:28:32.960 | however life originated.

00:28:34.760 | Do you think it's possible there's some pockets

00:28:38.360 | of complexity of that sort inside dark matter?

00:28:42.000 | Who can see?

00:28:42.840 | - So that's possible.

00:28:44.720 | - Chemistry and biology evolving in different ways.

00:28:49.560 | - And that's one of the reasons we suggest,

00:28:51.440 | I mean, it's not the reason,

00:28:52.440 | but it would be true if there were

00:28:54.280 | the type of interactions we'd suggest.

00:28:56.880 | I mean, it would need more complex ones.

00:28:59.200 | And we don't know.

00:29:00.400 | I will say that the conditions that give rise

00:29:04.080 | to life and complexity, they're complex, they're unlikely.

00:29:08.200 | So it's not like there's great odds that would happen.

00:29:13.000 | But there's no reason to know that it doesn't happen.

00:29:15.240 | It's worth investigating.

00:29:16.800 | Are there other forces that exist

00:29:18.360 | in the dark matter sector?

00:29:19.560 | That's exactly it.

00:29:20.400 | - So the dark matter sector doesn't have

00:29:23.360 | all the forces of the standard model of physics?

00:29:26.080 | - Right, as far as we know, it doesn't have any.

00:29:27.960 | It might have it at some low level.

00:29:29.920 | But it could have its own forces,

00:29:31.240 | just like the dark matter might not experience our light,

00:29:34.720 | maybe it has its light that we don't experience.

00:29:38.200 | - So there could be other kinds of forces.

00:29:40.720 | - I mean, there could be other kinds of forces

00:29:42.280 | even within our sector that are too weak

00:29:44.680 | for us to have discovered so far,

00:29:46.840 | or that exist at different scales than we know about.

00:29:49.660 | I mean, we detect what interacts strongly enough

00:29:53.420 | with our detectors to detect.

00:29:55.500 | So it's worth asking.

00:29:57.260 | And that's one of the reasons we build big colliders

00:29:59.740 | to see are there other forces, other particles

00:30:04.180 | that exist, say, at higher energies,

00:30:06.340 | at shorter distance scales than we've explored so far.

00:30:09.740 | So it's not just in the dark matter sector.

00:30:11.820 | Even in our sector, there could be a whole bunch of stuff

00:30:14.740 | we don't yet know.

00:30:16.660 | - So maybe let's zoom out and look at the standard model

00:30:20.140 | of particle physics.

00:30:21.740 | How does dark matter fit into, first of all, what is it?

00:30:24.300 | Can you explain what the standard model is?

00:30:27.780 | - So the standard model of particle physics

00:30:31.060 | is basically tells us about nature's most basic elements

00:30:35.700 | and their interactions.

00:30:37.380 | And so it's the substructure as far as we understand it.

00:30:41.180 | So if you look at atoms,

00:30:42.220 | we know they have nuclei and electrons.

00:30:44.800 | Nuclei have protons and neutrons in them.

00:30:47.900 | Protons and neutrons have particles called quarks

00:30:51.080 | that are held together by something called the strong force.

00:30:54.220 | They interact through the strong force,

00:30:57.860 | the strong nuclear force,

00:30:59.300 | something called the weak nuclear force

00:31:00.780 | and electromagnetism.

00:31:02.760 | So basically all those particles and their interactions

00:31:06.460 | describe many, many things we understand.

00:31:08.820 | That's the standard model.

00:31:10.720 | We now know about the Higgs boson,

00:31:13.220 | which is associated with how elementary particles

00:31:16.620 | get their mass.

00:31:17.460 | So that piece of the puzzle has also been completed.

00:31:20.620 | We also know that there are kind of a weird array of masses

00:31:23.860 | of elementary particles.

00:31:25.460 | There's not just the up and down quark,

00:31:27.460 | but there are heavier versions of the up and down quark,

00:31:30.340 | charm and strange, top and bottom.

00:31:32.420 | There's not just the electron, there's a muon and a tau.

00:31:35.340 | There are particles called neutrinos,

00:31:36.960 | which are under intense study now,

00:31:39.020 | which are partnered with the leptons

00:31:40.660 | through the weak interactions.

00:31:42.420 | So we really do know these basic elements

00:31:44.660 | and we know the forces.

00:31:46.700 | We know, I mean,

00:31:48.220 | when we're doing particle physics experiments,

00:31:50.040 | we can usually even ignore gravity,

00:31:52.140 | except in exceptional cases that we can talk about.

00:31:55.420 | So those are the basic elements in their interactions.

00:31:58.780 | Dark matter stands outside that.

00:32:00.680 | It's not interacting through those forces.

00:32:03.580 | So when we look at the world around us,

00:32:05.580 | we don't usually see the effects of dark matter.

00:32:07.800 | It's because there's so much of it that we do

00:32:10.540 | and it doesn't have those forces that we know about.

00:32:13.860 | But the Standard Model has worked spectacularly well.

00:32:16.500 | It's been tested to a high degree of precision.

00:32:19.460 | People are still testing it.

00:32:21.140 | And one of the things we do as physicists

00:32:22.820 | is we actually wanted to break down at some level.

00:32:26.060 | We're looking for the precision measurement

00:32:29.300 | or the energy or whatever it will take,

00:32:31.500 | where the Standard Model is no longer working.

00:32:35.580 | Not that it's not working approximately,

00:32:38.100 | but we're looking for the deviations.

00:32:39.500 | And those deviations are critical

00:32:41.500 | because they can tell us what underlies the Standard Model,

00:32:44.060 | which is what we really wanna see next.

00:32:45.940 | - Where can you find the places

00:32:47.500 | where the Standard Model breaks down?

00:32:49.060 | Like what are the places you can see

00:32:51.300 | those tiny little deviations?

00:32:52.940 | - So we don't know yet,

00:32:54.580 | but we know the kinds of things you wouldn't wanna look for.

00:32:57.220 | So one obvious place to look is at higher energy.

00:33:01.020 | We're looking at the Large Hadron Collider,

00:33:02.620 | but we'd love to go beyond that.

00:33:04.460 | Higher energies means shorter distances

00:33:07.060 | and it means things that we just couldn't produce before.

00:33:09.440 | I mean, E equals MC squared.

00:33:11.460 | So if you have a heavy particle

00:33:12.580 | and you don't have enough energy to make it,

00:33:14.100 | you'll never see it.

00:33:15.540 | So that's one place.

00:33:16.940 | The other place is precision measurements.

00:33:18.940 | If you, you know,

00:33:19.860 | the Standard Model has been tested exquisitely.

00:33:22.580 | So if it's been tested at 1%,

00:33:24.900 | you wanna look at a 10th of a percent.

00:33:27.180 | And there are some processes

00:33:28.300 | that we know shouldn't even happen at all

00:33:29.820 | in the Standard Model or happen at a very suppressed level.

00:33:32.620 | And those are other things that we look for.

00:33:34.940 | So all of those things could indicate

00:33:37.860 | there's something beyond what we know about,

00:33:39.720 | which of course would be very exciting.

00:33:42.480 | - When you just step back and look at the Standard Model,

00:33:45.720 | the quarks and all the different particles and neutrinos,

00:33:49.000 | isn't it wild how this like little system came to being,

00:33:55.680 | creates, underpins everything we see?

00:33:59.100 | - Absolutely.

00:33:59.940 | And that's why we'd like to understand it better.

00:34:01.920 | We wanna know, is it part of some bigger sector?

00:34:05.320 | Why are these particles,

00:34:06.280 | why do they have the masses they do?

00:34:07.720 | - Yeah.

00:34:08.660 | - Why is the Higgs boson so light

00:34:09.980 | compared to the mass it could have had,

00:34:11.660 | which we might have even expected

00:34:13.460 | based on the principles of special relativity

00:34:16.540 | and quantum mechanics?

00:34:17.740 | So that's a really big question.

00:34:19.740 | Why are they what they are?

00:34:21.220 | - And they originate, there's like some mechanism

00:34:23.460 | that created the whole thing?

00:34:24.940 | - That's one of the things we're trying to study.

00:34:26.820 | Why is it what it is?

00:34:28.540 | - I mean, even just like the mechanism that creates stuff,

00:34:32.380 | like the way a human being is created from a single cell.

00:34:37.720 | It's like embryogenesis,

00:34:39.840 | like the whole thing, you build up this thing.

00:34:42.240 | All of it, this whole thing comes to be

00:34:45.880 | from just like a tiny little--

00:34:46.720 | - But don't forget, it is interacting with the environment.

00:34:49.720 | - Sure.

00:34:50.620 | Okay, right, right, right.

00:34:51.460 | It's not, it's not, right.

00:34:52.960 | - It's important.

00:34:53.800 | - Well, that's a really good question,

00:34:54.800 | is how much of it is the environment?

00:34:56.440 | Is it just the environment acting on a set of constraints?

00:35:01.080 | And like how much of it is just the information in the DNA

00:35:05.880 | or in the information?

00:35:07.160 | How much is it in the initial conditions of the universe

00:35:10.000 | versus some other thing acting on it?

00:35:14.760 | - These are big questions.

00:35:15.920 | These are big questions in pretty much every field.

00:35:18.480 | For the universe, we do consider it,

00:35:22.800 | it's everything there is by definition.

00:35:25.300 | But people now think about it as one of many universes.

00:35:29.360 | And of course, it's a misnomer,

00:35:31.620 | but could there be other places

00:35:33.080 | where there are self-contained gravitational systems

00:35:35.340 | that we don't even interact with?

00:35:37.520 | So, but those are really important questions.

00:35:40.060 | And the only way we're gonna answer them is,

00:35:41.600 | you know, we go back as far as we can.

00:35:43.560 | We try to think theoretically,

00:35:45.060 | and we try to think about observational consequences.

00:35:48.000 | That's all we can do.

00:35:49.160 | - One interesting way to explore the Standard Model

00:35:51.480 | is to look at your fun, nuanced disagreement

00:35:56.480 | with Carlo Rovelli.

00:35:58.660 | When you talked about him writing in his book,

00:36:03.200 | electrons don't always exist,

00:36:04.760 | they exist when they interact.

00:36:06.360 | They materialize in a place

00:36:07.480 | when they collide with something else.

00:36:09.080 | And you wrote that, well, I'll just read the whole thing,

00:36:11.480 | 'cause it's kind of interesting.

00:36:13.160 | "Stocks may not achieve a precise value

00:36:15.480 | "until they are traded,

00:36:16.820 | "but that doesn't mean we can't approximate their worth

00:36:19.320 | "until they change hands.

00:36:20.860 | "Similarly, electrons might not have definite properties,

00:36:25.020 | "but they do exist.

00:36:26.620 | "It's true that the electron doesn't exist

00:36:29.500 | "as a classical object with definite position

00:36:32.120 | "until the position is measured,

00:36:33.440 | "but something was there

00:36:35.920 | "which physicists use a wave function to describe."

00:36:39.400 | It's a fascinating, nuanced disagreement.

00:36:41.640 | So do electrons always exist or not?

00:36:44.120 | Does a tree fall in the forest if nobody's there to see it?

00:36:48.160 | - So I like to think of the universe

00:36:50.120 | as being out there, whether or not.

00:36:51.600 | I mean, it would be really weird

00:36:52.960 | if the only time things came into existence

00:36:54.880 | was when I saw them or I measured them.

00:36:57.080 | - There's a lot of weird stuff.

00:36:58.040 | - I mean, I could believe that the Middle East

00:36:59.440 | doesn't exist because I'm not there now.

00:37:01.760 | I mean, that would be kind of ridiculous.

00:37:03.760 | I think we would all agree on that.

00:37:05.480 | So I think there's only so much

00:37:07.880 | that we can attribute to our own powers of seeing.

00:37:10.360 | And the whole system doesn't come into being

00:37:14.040 | because I'm measuring it.

00:37:15.640 | And so what is weird,

00:37:17.520 | and this isn't even a disagreement about the standard model,

00:37:19.680 | this is a disagreement

00:37:20.520 | about how you interpret quantum mechanics.

00:37:22.360 | I mean, I would say that those wave functions are real.

00:37:25.200 | I mean, one of the things that,

00:37:26.600 | don't forget that particle physics does

00:37:28.560 | that quantum field theory says

00:37:30.200 | that electrons can be created and destroyed.

00:37:32.680 | It's not that every electron has to be in the universe.

00:37:34.760 | I mean, that's what happens at colliders,

00:37:37.200 | particles get created and destroyed.

00:37:39.080 | But that doesn't mean that if I have an electron in an atom,

00:37:43.160 | it's not there, it's certainly there,

00:37:44.560 | and we know about it, its charge is there.

00:37:47.200 | - So physics is a kind of way to see the world.

00:37:50.040 | So what, at the bottom, what's the bottom turtle?

00:37:55.080 | Do you have a sense that there's a bottom reality

00:37:58.920 | that we're trying to approximate with physics?

00:38:01.200 | - I think we always have in our head

00:38:02.640 | maybe that we'd like to find that,

00:38:04.680 | but I have to, I mean, I might not seem so,

00:38:07.760 | but I think I'm kind of more humble than a lot of physicists.

00:38:09.640 | I'm not sure that we're ever gonna get to that bottom level,

00:38:12.800 | but I do think we're going to keep penetrating

00:38:14.640 | different layers and get further.

00:38:16.400 | - I just wonder how far away we are, you know?

00:38:20.160 | - We all wonder that.

00:38:21.680 | It's not even, like, what's even the measure

00:38:23.400 | of how far away we are?

00:38:24.760 | I mean, one way you can measure it

00:38:25.880 | is just by our everyday lives.

00:38:27.440 | In terms of our everyday lives,

00:38:28.600 | we've measured everything.

00:38:30.000 | In terms of what underlies it, there's a lot more to see.

00:38:33.360 | And so part of it has to do with how far we think we can go.

00:38:36.840 | I mean, it might be that the nature of reality

00:38:39.440 | changes so much that even these terms are different.

00:38:42.800 | Maybe we'll measure, you know,

00:38:44.800 | the notion of distance itself might break down at some point.

00:38:48.800 | - But also to push back on the we've measured everything,

00:38:51.200 | maybe there's stuff we haven't even considered

00:38:52.920 | is measurable.

00:38:54.000 | For example, consciousness, or there's,

00:38:58.400 | there might be stuff, just like you said,

00:39:00.480 | forces unseen, undetected.

00:39:02.800 | - So it's an interesting thing.

00:39:04.760 | And this is often a confusion that happens.

00:39:07.400 | So there's sort of the fundamental stuff underlying it,

00:39:10.600 | and then there's sort of the higher levels,

00:39:12.160 | what we'll call an effective theory at some level.

00:39:15.680 | So we're not always working.

00:39:17.400 | I mean, when I throw a ball,

00:39:18.480 | I don't tell you where every atom is.

00:39:20.520 | I tell you there's a ball.

00:39:22.120 | And so there might be different layers of reality

00:39:25.040 | that are built in terms of the matter that we know about,

00:39:28.200 | in terms of the stuff we know about.

00:39:30.480 | And when I say we've measured everything,

00:39:32.760 | I say that with a grain of salt.

00:39:34.880 | I mean, I measure everything about the stanomal.

00:39:37.400 | So there's lots of phenomena that we don't understand,

00:39:42.200 | but often there are complex phenomena

00:39:44.040 | that will be given in terms of the fundamental ingredients

00:39:46.800 | that we know about.

00:39:47.680 | - But that is an interesting question,

00:39:49.120 | because yes, there's phenomena

00:39:51.160 | that are at the higher level of abstractions that emerge,

00:39:54.240 | but maybe, like with consciousness,

00:39:56.880 | there is far out people that think that consciousness

00:39:59.920 | is panpsychic, right?

00:40:02.480 | There's going to be almost like a fundamental force

00:40:06.880 | of physics that's consciousness,

00:40:08.520 | that permeates all matter, right?

00:40:10.000 | - Usually when you have a crazy, sorry,

00:40:12.240 | okay, when you have a far out theory,

00:40:14.560 | the thing you do is you test all the possibilities

00:40:17.200 | within the constructs that exist.

00:40:19.640 | So you don't just jump to the most far out possibility.

00:40:22.360 | I mean, you can do that, but then to see if it's true,

00:40:24.720 | you either have to find evidence of it,

00:40:26.760 | or you have to show that it's not possible without that.

00:40:29.560 | And we're very far from that.

00:40:32.480 | - I think one of the criticisms of your theory

00:40:34.880 | on the dinosaurs was that it requires,

00:40:37.800 | if I remember correctly, for dark matter

00:40:39.400 | to be weirder than it already is.

00:40:41.480 | And then I think you had a clever response to that.

00:40:44.840 | Can you remind?

00:40:46.360 | - I'm not sure I remember what I said then,

00:40:47.720 | but I mean, we have no idea how weird dark matter is.

00:40:50.360 | I mean, it's based on everyone thinking

00:40:52.120 | they know what dark matter is.

00:40:53.560 | I mean, so weirder than it already is,

00:40:55.160 | I mean, it's not already anything.

00:40:56.520 | We don't know what it is.

00:40:57.760 | So there's no normalization here.

00:40:59.500 | - So dark matter, do we know

00:41:02.880 | if dark matter varies in density?

00:41:05.120 | - It definitely does in the universe, just like,

00:41:07.120 | I mean, so for example, there's more dark matter

00:41:09.760 | in galaxies than there is between galaxies.

00:41:12.680 | So it clumps, I mean, so it's matter.

00:41:15.720 | So it's distributed like matter.

00:41:17.240 | It is matter.

00:41:18.760 | - It does clump.

00:41:20.060 | But the full details of how it clumps,

00:41:23.880 | and the complexity of the clumping.

00:41:25.680 | - It's understood pretty well.

00:41:27.960 | People do simulations.

00:41:29.640 | I mean, where people are always looking for things,

00:41:32.800 | including us as particle physics,

00:41:34.520 | it's sort of at small scales,

00:41:36.080 | or the deviations on small scales,

00:41:37.800 | so indicating other interactions or other processes,

00:41:41.100 | or interactions with baryons,

00:41:43.520 | that is to say normal matter that we don't understand.

00:41:46.220 | But on large scales, we have a pretty good understanding

00:41:48.560 | of dark matter distribution.

00:41:50.480 | - You were part of a recent debate on,

00:41:53.080 | quote, "Can science uncover reality?"

00:41:55.840 | Let me ask you this question then.

00:41:57.720 | What do you think is the limits of science?

00:41:59.920 | - I'm smart enough to know I have no idea.

00:42:03.480 | And also, it's not even clear what science means, right?

00:42:06.480 | Because there's the science that we do,

00:42:08.160 | which is particle physics.

00:42:10.320 | We try to find fundamental things

00:42:12.040 | and figure out what their effects are.

00:42:14.200 | There's science like biology, where,

00:42:16.340 | you know, it's at a higher level.

00:42:17.880 | The kind of questions you ask are different.

00:42:19.480 | The kind of measurements are different.

00:42:21.720 | The kind of science that's going to happen

00:42:23.840 | in the sort of more numerical age, I mean, or even AI,

00:42:27.600 | or like, what does it mean to answer a question?

00:42:30.200 | Does it mean that we can predict it?

00:42:31.760 | Does it mean that we can reproduce it?

00:42:33.680 | So I think we're coming up against

00:42:35.880 | sort of the definition of what we mean by science

00:42:38.200 | as human beings.

00:42:39.800 | So in terms of the science that we can do,

00:42:43.520 | I don't think we'll know it until we get there.

00:42:46.480 | You know, we're trying to solve hard problems.

00:42:48.200 | And, you know, we've made progress.

00:42:50.160 | I mean, if you think of how much science has advanced

00:42:52.160 | in the last century or century and a half, it's incredible.

00:42:55.380 | I mean, you know, we didn't even know

00:42:56.760 | the universe was expanding

00:42:58.400 | at the beginning of the 20th century.

00:43:00.180 | We didn't know about quantum mechanics

00:43:01.440 | in the beginning of the century.

00:43:02.280 | We didn't know about special relativity.

00:43:03.600 | That's a lot in a relatively short time,

00:43:06.640 | depending on how you think of time.

00:43:09.440 | So I think it would be premature to say

00:43:12.720 | we know the limitations.

00:43:14.440 | - And at various points throughout the history,

00:43:16.080 | we thought we solved everything, or declared,

00:43:18.560 | or at least various people declared.

00:43:19.560 | - Where we was various people, exactly.

00:43:21.320 | - Yeah, yeah, yeah, declared that we've solved everything.

00:43:23.760 | So this is also a good place to maybe,

00:43:26.480 | could you describe the difference between top-down

00:43:28.600 | and bottom-up approaches to theoretical physics

00:43:31.120 | that you talked about in the book?

00:43:32.840 | - So you could try to jump in and say,

00:43:36.180 | I have a theory that I think is so perfect

00:43:38.600 | that I can predict everything from it,

00:43:43.520 | or at least predict some salient features from it.

00:43:45.920 | - Mm-hmm, that's top-down.

00:43:47.220 | - That would be top-down.

00:43:48.720 | Bottom-up is more like the questions we just asked,

00:43:52.640 | why are masses what they are?

00:43:53.760 | We measure things, we want to put them together.

00:43:56.640 | And usually a good approach is to combine the two.

00:43:58.880 | If you ask a very specific question,

00:44:01.200 | but combine it with the methods of knowing

00:44:04.360 | that there could be a fundamental theory underlying it,

00:44:07.160 | sometimes you make progress.

00:44:08.400 | I mean, the community tends to get segmented,

00:44:11.200 | or fragmented, into people who do one or the other.

00:44:14.680 | But there are definitely times,

00:44:16.000 | I mean, some of my best collaborations

00:44:17.480 | have been with people who are more top-down than I am,

00:44:20.160 | so that we come up with interesting ideas

00:44:22.320 | that we wouldn't have thought of

00:44:23.400 | if either one of us was working individually.

00:44:25.640 | - Would you say the truly big leaps

00:44:27.600 | happen top-down, like Einstein?

00:44:30.480 | - Einstein was not a top-down person in the beginning.

00:44:33.240 | Special relativity was very much him thinking about,

00:44:37.960 | you know, they were thought experiments,

00:44:39.160 | but he was very much, you know,

00:44:40.880 | the original theory about relativity

00:44:42.600 | is something like on the nature of electromagnetism.

00:44:45.520 | He was trying to understand how Maxwell's laws

00:44:49.000 | could make sense when they were, you know,

00:44:51.640 | seemed to have different symmetries

00:44:53.160 | than what we had thought they were.

00:44:54.560 | So he was very much a bottom-up person.

00:44:56.720 | And in fact, he resisted top-down for a long time.

00:44:59.600 | Then when he tried to do the theory of general relativity,

00:45:02.120 | or the general theory of relativity,

00:45:03.280 | whichever you want to call it,

00:45:05.360 | incorporating gravity into the system

00:45:07.520 | where you need some feedback,

00:45:09.320 | then he was helped by a mathematician

00:45:11.680 | who had developed some differential geometry

00:45:14.000 | and helped him figure out how to write down that.

00:45:16.240 | And after that, he thought top-down was the way to go,

00:45:18.480 | but he actually didn't make that much progress.

00:45:21.280 | But certainly, so I think it's, you know,

00:45:24.000 | naive to think it was just one or the other.

00:45:26.320 | In fact, a lot of people who made real progress

00:45:28.720 | were rooted in actual measurements.

00:45:31.120 | - Well, speaking of mathematicians,

00:45:33.600 | what to you is the difference,

00:45:35.600 | because you've had a bit of foot in both,

00:45:37.440 | between physics and mathematics

00:45:39.040 | in the way it helps us understand the world?

00:45:41.280 | - Well, there's, to be frank,

00:45:42.600 | there's a lot more overlap in physics and math,

00:45:44.880 | I think, than has been, I mean, well, maybe not more,

00:45:47.440 | but there's certainly a lot.

00:45:48.880 | But I think, again, the kinds of questions you're asking

00:45:51.720 | are usually different.

00:45:54.200 | Mathematicians like the structure itself.

00:45:57.040 | Physicists are trying to concentrate on,

00:45:59.360 | to some extent, on the consequences for the world.

00:46:02.600 | But there is a lot of overlap.

00:46:04.680 | - The string theory is an example.

00:46:06.300 | There's certain theories where there's a certain kind

00:46:09.720 | of mathematical beauty to it.

00:46:12.440 | There's also some really cool ideas

00:46:15.160 | that you get in particle physics,

00:46:16.840 | where you can describe what's going on

00:46:18.440 | and connect it to other ideas.

00:46:19.620 | That's also really beautiful.

00:46:21.040 | I think, basically, insights can be beautiful.

00:46:25.100 | They might seem simple, and sometimes they genuinely are.

00:46:30.140 | And sometimes they're built on a whole system

00:46:32.640 | that you have to understand before.

00:46:34.780 | I mean, if you actually saw Einstein's equations

00:46:36.580 | written out in components, you wouldn't think

00:46:39.000 | it's so beautiful.

00:46:39.840 | You write it in a compact way, it looks nice.

00:46:42.080 | - What do you think about the successes

00:46:45.760 | and the failures of string theory?

00:46:48.000 | To what degree do you think it succeeded?

00:46:50.440 | To what degree is it not succeeded yet, or has failed?

00:46:54.560 | - I think to talk about any science

00:46:56.760 | in terms of success and failure often misses the point,

00:46:59.720 | because there's not some absolute thing.

00:47:01.840 | And I do think that string theorists

00:47:05.840 | were a bit overly ambitious.

00:47:07.420 | Not overly ambitious, but a little bit overly arrogant

00:47:10.400 | in the beginning, thinking they could solve many problems

00:47:12.640 | that they weren't going to solve.

00:47:14.040 | That's not to say the methods and advances

00:47:16.880 | in string theory don't exist.

00:47:18.380 | But they certainly weren't able to immediately solve

00:47:22.560 | all the problems they thought they could solve.

00:47:24.520 | But it has given us tools.

00:47:27.040 | It has given us some insights.

00:47:28.880 | But it becomes almost a sociological question

00:47:32.960 | of how much it should be one or the other.

00:47:35.200 | I do think that you can get caught up

00:47:37.000 | in the problems themselves,

00:47:38.040 | and sometimes you can get caught up in the methods

00:47:40.960 | and just sort of do other examples.

00:47:43.320 | So the real physics insights often come from people

00:47:46.040 | who are thinking about physics as well as math.

00:47:49.500 | - 'Cause you mentioned AI.

00:47:51.160 | There's hope that AI might be able to help

00:47:55.840 | find some interesting insights.

00:47:59.720 | I mean, another question, another way to ask this question

00:48:02.360 | is how special are humans that we're able to discover

00:48:06.080 | novel insights about the world?

00:48:07.800 | - That's a great question.

00:48:10.300 | And it depends on what kind of insights

00:48:13.280 | and what we're going to find that out.

00:48:14.620 | I mean, because it's hard to think about something

00:48:18.480 | that doesn't quite exist yet.

00:48:20.680 | I mean, I could just think about something,

00:48:23.000 | take a step back.

00:48:24.160 | It's a little bit like trying to say in four dimensions,

00:48:26.760 | you go back to three dimensions,

00:48:28.440 | so to go to something you can imagine.

00:48:30.800 | So you can sort of say a lot of the things

00:48:34.040 | in a very different level about the internet.

00:48:36.280 | You could say, has the internet helped do things?

00:48:40.360 | And that's, it definitely took on a life of its own

00:48:42.720 | in some sense, but it's also something

00:48:44.600 | that we're able to tame.

00:48:47.320 | I know that I myself wouldn't have been able to write books

00:48:49.560 | if the internet didn't exist,

00:48:50.780 | because I wouldn't have had the time to go to a library

00:48:52.600 | and look everything up.

00:48:53.920 | And it helped me enormously.

00:48:57.040 | And in some sense, AI could be that in a very nice world.

00:49:01.520 | It could be a tool that helps us go a step further

00:49:05.920 | than we would and a lot more efficiently.

00:49:08.480 | And it's already done that to some extent.

00:49:11.280 | Or it could be like the parts of the internet

00:49:13.780 | that we can't control, that are ruining politics or whatever.

00:49:17.400 | So, and there's certainly a lot of indications

00:49:19.440 | that can do that.

00:49:20.760 | Then there are even bigger things that people speculate

00:49:24.000 | about AI being able to do its own things.

00:49:27.120 | But in terms of actually figuring things out,

00:49:31.080 | we're in the early stages.

00:49:32.440 | - Yeah, there's several directions here.

00:49:34.880 | One is like on the theorem prover side,

00:49:36.640 | so Wolfram Alpha, where everything is much more precise.

00:49:39.520 | And we have large language model type of stuff.

00:49:42.960 | One of the limitations of those is it seems to come up

00:49:47.360 | with convincing looking things,

00:49:49.520 | which we don't know if it's true or not.

00:49:52.320 | And that's a big problem for physics.

00:49:54.160 | - So large language models are more or less

00:49:55.760 | like generalizations of stuff that we have.

00:49:58.640 | So the question is, so there's still breakthroughs

00:50:03.200 | in AI waiting to happen and maybe they are happening.

00:50:05.880 | And maybe they'll be good, maybe not.

00:50:07.280 | But that's not quite the same.

00:50:09.880 | I mean, maybe just some, in some cases,

00:50:12.120 | it's just pattern recognition

00:50:13.480 | that leads to important things.

00:50:15.680 | But sometimes it could be something more insightful

00:50:18.440 | than that, that I can't even put my finger on.

00:50:20.820 | So it forces us to, I mean,

00:50:23.440 | we don't really understand how smart we are.

00:50:25.320 | We don't understand how we think about things

00:50:27.160 | all that well, actually.

00:50:28.440 | But one thing is true,

00:50:29.640 | though we're a lot more efficient right now than computers

00:50:32.760 | and coming up with things.

00:50:33.680 | We require a lot less energy to do that.

00:50:35.840 | So if computers figure out how to do that,

00:50:39.240 | then it's gonna be a totally different ball game.

00:50:41.640 | So, and so there are clearly kinds of connections

00:50:44.160 | that we don't know how we're making, but we are making them.

00:50:47.360 | And so that's going to be interesting.

00:50:50.120 | So, I say we're in early stages,

00:50:53.140 | but this is changing very rapidly.

00:50:55.740 | But right now, I don't think that it's actually,

00:50:59.460 | we've discovered new laws of physics,

00:51:03.020 | but could it in the future?

00:51:04.780 | Maybe it can.

00:51:06.240 | - It will raise big questions about

00:51:08.700 | what is special about humans that we don't quite appreciate?

00:51:13.860 | There could be things that are like

00:51:17.020 | that leap of insight that happens.

00:51:19.860 | Truly novel ideas.

00:51:22.080 | That could potentially be very difficult to do.

00:51:25.180 | - So there are sort of abstract questions like that.

00:51:28.960 | There's also questions of how is it

00:51:31.720 | that we can address to some extent,

00:51:34.400 | how will AI be used in the context of the world we live in?

00:51:37.920 | Which is based on, at least our country's based on

00:51:40.560 | capitalism and a certain political system.

00:51:43.040 | And how will global politics deal with it?

00:51:45.800 | How will our capitalist system deal with it?

00:51:48.480 | What will be the things that we focus on doing with it?

00:51:51.460 | How much will researchers get control of it

00:51:53.980 | to be able to ask different sorts of questions?

00:51:57.500 | I mean, while it was starting out,

00:51:59.500 | people were doing these kind of toy problems,

00:52:01.980 | but what will it actually be applied to

00:52:04.060 | and what will it be optimized to do?

00:52:06.220 | There's a lot of questions out there

00:52:08.400 | that it's really important we start addressing.

00:52:10.700 | - What to you is the most beautiful unsolved problem

00:52:17.960 | in physics and cosmology?

00:52:20.600 | What to you is really exciting if we can unlock

00:52:24.680 | the mystery of in the next few decades?

00:52:27.320 | - So is it what's the most beautiful unsolved problem

00:52:31.600 | or what is the most beautiful unsolved problem

00:52:33.240 | I think we can make progress on?

00:52:34.840 | - Oh boy.

00:52:37.000 | We make progress on in the next few centuries.

00:52:40.720 | - Most of the questions, the big questions,

00:52:45.560 | have to do with what underlies things,

00:52:47.100 | how things started, what's at the base of it.

00:52:49.580 | There's also just basic questions like

00:52:51.580 | that you asked earlier, how far will science take us?

00:52:54.100 | How much can we understand?

00:52:56.300 | There are questions like how we got here,

00:52:59.740 | what underlies it, are there, you know?

00:53:02.380 | But also, I mean, there's really deep questions

00:53:05.420 | like what fraction are we actually seeing?

00:53:08.420 | If there are these other forces,

00:53:09.780 | if there is another way of seeing the world,

00:53:12.060 | are there galaxies, universes beyond our own?

00:53:15.060 | If they're so totally different,

00:53:16.540 | how do we even comprehend them?

00:53:17.900 | I mean, how do we detect,

00:53:19.340 | like what would we even think about them?

00:53:21.440 | So there's a lot about trying to get beyond,

00:53:26.440 | it's always just getting beyond our limited vision

00:53:29.780 | and limited experience and trying to see what underlies it,

00:53:32.700 | both at small scales and at large scales.

00:53:35.540 | We just don't know the answers.

00:53:37.260 | I mean, I'd like to think that we understand more

00:53:39.900 | about dark matter, about dark energy,

00:53:41.860 | about are there extra dimensions,

00:53:43.260 | things that we actually work on.

00:53:44.820 | 'Cause there's probably a lot beyond what we work on

00:53:46.580 | that's yet to be discovered.

00:53:48.040 | - Yeah, understanding the extra dimensions piece

00:53:52.420 | will be really interesting.

00:53:55.980 | - Totally.

00:53:57.220 | I mean, if it is how the universe went

00:53:59.860 | from higher dimensions to what we see,

00:54:01.920 | are the extra dimensions present everywhere?

00:54:06.180 | I mean, one of the really interesting pieces of physics

00:54:09.120 | we did that I talk about in my first book, "War Passages,"

00:54:12.580 | finding out that there can be a higher dimension,

00:54:16.420 | but only locally do you think there's a gravity

00:54:18.460 | of a lower dimension.

00:54:19.860 | So it could be like only locally do we think

00:54:21.980 | we live in three dimensions,

00:54:23.020 | it could be higher dimensions, it's different.

00:54:25.060 | It's not actually the gravity we have,

00:54:26.380 | but there's all sorts of phenomena

00:54:28.420 | that might be out there that we don't know about.

00:54:30.260 | All sorts of evolution things,

00:54:31.660 | time dependence that we don't know about.

00:54:34.300 | And of course, that's from the point of view

00:54:35.460 | of particle physics.

00:54:36.300 | From the point of view of other kinds of physics,

00:54:37.740 | we're just beginning, so who knows?

00:54:40.500 | - Yeah, if the physics changes throughout,

00:54:43.060 | is not homogeneous throughout the universe,

00:54:45.260 | that would be weird.

00:54:48.420 | - I mean, for the observable universe, it's the same,

00:54:51.500 | but beyond the observable universe, who knows?

00:54:54.640 | - What advice would you give?

00:54:56.680 | You've had an exceptional career.

00:55:00.460 | What advice would you give to young people,

00:55:02.260 | maybe high school, college,

00:55:03.780 | on how to have a career they can be proud of

00:55:07.780 | and a life they can be proud of?

00:55:09.980 | - I think the weird thing about being a scientist

00:55:12.500 | or an academic in general is,

00:55:14.260 | you have to believe really strongly in what you do

00:55:15.860 | while questioning it all the time.

00:55:17.980 | You can't, and that's a hard balance to have.

00:55:20.780 | Sometimes it helps to collaborate with people,

00:55:23.140 | but to really believe that you could have good ideas

00:55:25.260 | at the same time knowing they could all be wrong,

00:55:27.100 | that's a tough tightrope to walk sometimes,

00:55:30.900 | but to really test them out.

00:55:32.920 | The other thing is sometimes, if you get too far buried,

00:55:38.220 | you look out and you think, oh, there's so much out there,

00:55:40.660 | and sometimes it's just good to bring it back home

00:55:43.340 | and just think, okay, can I have as good an idea

00:55:45.300 | as the person next to me,

00:55:46.260 | rather than the greatest physicist who ever lived?

00:55:49.500 | But right now, like you said,

00:55:51.260 | I think there's lots of big issues out there,

00:55:53.220 | and it's hard to balance that.

00:55:55.460 | Sometimes it's hard to forget the role of physics,

00:55:58.740 | but I think Wilson said it really well

00:56:00.980 | when he said, when they were building Fermilab,

00:56:03.820 | it was like, this won't defend the country,

00:56:06.040 | but it'll make it worth defending.

00:56:08.060 | It's just the idea that in all this chaos,

00:56:10.620 | it's still important that we still make progress

00:56:12.540 | in these things, and sometimes,

00:56:14.140 | when major world events are happening,

00:56:15.900 | it's easy to forget that,

00:56:17.460 | and I think those are important, too.

00:56:18.640 | You don't wanna forget those,

00:56:19.660 | but to try to keep that balance

00:56:21.500 | because we don't wanna lose what it is

00:56:22.900 | that makes humans special.

00:56:24.740 | - So that's the big picture.

00:56:25.780 | Would you also lose yourself

00:56:26.940 | in the simple joy of puzzle solving?

00:56:29.160 | - Yeah, yeah.

00:56:30.740 | I mean, we all like solving puzzles,

00:56:34.660 | and actually, one of the things that drives me

00:56:36.160 | in my research is inconsistencies.

00:56:38.540 | When things don't make sense, it really bugs me,

00:56:40.860 | and it just will go in different directions

00:56:44.220 | to see how could these things fit together.

00:56:46.260 | - So it bugs you, but that motivates you.

00:56:48.780 | - Yeah, totally.

00:56:49.660 | - Until it doesn't.

00:56:50.760 | - Because I think, 'cause I have this underlying belief

00:56:53.060 | that it should make sense,

00:56:54.100 | even though the world comes at you in many ways

00:56:56.380 | and tells you nothing should make sense,

00:56:58.460 | but if you believe that it makes sense,

00:57:00.020 | then you look for underlying logic,

00:57:02.100 | and I think that's just good advice for everything,

00:57:04.140 | to try to find why is it the way it is.

00:57:06.840 | I think, I talk about effective theory

00:57:09.160 | in my second book, "Noggin in Heaven's Door," a lot.

00:57:11.800 | It's sort of, rather than ask the big questions,

00:57:14.000 | sometimes we just ask the questions

00:57:15.340 | about the immediate things that we can measure,

00:57:18.040 | and we can, like I said, we can sometimes tell one

00:57:20.160 | that will fail, but we can have these effective theories,

00:57:22.720 | and sometimes I think when we approach these big questions,

00:57:26.080 | it's good to do it from an effective theory point.

00:57:28.760 | Why do I find this satisfying?

00:57:29.960 | Why is the world we have the way it is?

00:57:32.000 | We think things are beautiful that we live in.

00:57:34.340 | I mean, I'm not sure if we had different senses

00:57:37.660 | or different ways of looking at things,

00:57:38.880 | we wouldn't necessarily find it beautiful,

00:57:40.760 | but I have to say, it is kind of fantastic

00:57:43.680 | that no matter how many times I see a sunset,

00:57:46.120 | I will always find it beautiful.

00:57:47.420 | It's like, I don't think I'd ever see a sunset

00:57:49.340 | and say, "Uh, whatever."

00:57:51.020 | It's just always beautiful.

00:57:52.320 | And so there are things that as humans

00:57:55.500 | clearly resonate with us,

00:57:56.560 | but we were maybe evolved that way, but that's about us.

00:58:00.880 | But in terms of figuring out the universe,

00:58:02.800 | it's kind of amazing how far we've gotten.

00:58:05.220 | We have discovered many, many wonderful things,

00:58:08.780 | but there's a lot more out there,

00:58:10.440 | and I hope we have the opportunity to keep going.

00:58:13.920 | - And with effective theories, one small step at a time,

00:58:17.760 | just keep unraveling the mystery.

00:58:19.200 | - But also having in mind the big questions,

00:58:21.040 | but doing one small step at a time, exactly.

00:58:23.280 | - Yeah, looking out to the stars.

00:58:24.960 | You said the sunset.

00:58:26.320 | For me, it's the sunset, the sunrise,

00:58:29.580 | and just looking at the stars.

00:58:31.680 | It's wondering what's all out there,

00:58:35.120 | and having a lot of hope that humans will figure it out.

00:58:39.640 | - Right, I like it.

00:58:41.020 | - Lisa, thank you for being one of the humans

00:58:45.400 | in the world that are pushing it forward

00:58:48.580 | and figuring out this beautiful puzzle of ours,

00:58:51.440 | and thank you for talking today.

00:58:52.600 | This was amazing.

00:58:53.480 | - Thank you.

00:58:54.320 | - Thanks for listening to this conversation

00:58:56.680 | with Lisa Randell.

00:58:57.880 | To support this podcast,

00:58:59.000 | please check out our sponsors in the description.

00:59:01.520 | And now, let me leave you with some words

00:59:03.400 | from Albert Einstein.

00:59:05.280 | The important thing is to not stop questioning.

00:59:08.760 | Curiosity has its own reason for existence.

00:59:12.920 | Thank you for listening, and hope to see you next time.

00:59:15.620 | (upbeat music)

00:59:18.200 | (upbeat music)

00:59:20.780 | [BLANK_AUDIO]

Lisa Randall: Dark Matter, Theoretical Physics, and Extinction Events | Lex Fridman Podcast #403

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