Barry Barish: Gravitational Waves and the Most Precise Device Ever Built

Barry Barish (03:40.160)

questions. My father generally could answer them at that age. And the first one I remember that he

Barry Barish (03:46.880)

couldn't answer was not a very original question, but basically that ice is made out of water,

Lex Fridman (03:56.320)

and so why does it float on water? He couldn't answer it. It may not have been the first

Barry Barish (04:05.680)

question. It's the first one that I remember. And that was the first time that I realized that

Barry Barish (04:11.040)

to learn and answer your own curiosity or questions, there's various mechanisms. In

Barry Barish (04:17.840)

this case, it was going to the library or asking people who know more and so forth. But

Barry Barish (04:23.600)

eventually, you do it by what we call research. But it's driven by, hopefully, you ask good

Barry Barish (04:33.200)

questions. If you ask good questions and you have the mechanism to solve them, then you do what I

Barry Barish (04:37.920)

do in life, basically, not necessarily physics. And it's a great quality in humans, and we should

Barry Barish (04:45.040)

nurture it. Do you remember any other kind of in high school, maybe early college, more basic

Lex Fridman (04:52.320)

physics ideas that sparked your curiosity or mathematics or science in general?

Barry Barish (04:57.360)

I wasn't really into science until I got to college, to be honest with you. But

Barry Barish (05:02.960)

just staying with water for a minute, I remember that I was curious what happens to water. It rains

Lex Fridman (05:14.320)

and there's water in a wet pavement, and then the pavement dries out. What happened to this

Barry Barish (05:19.120)

water that came down? And I didn't know that much. And then eventually, I learned in chemistry or

Barry Barish (05:24.960)

something, water is made out of hydrogen and oxygen. Those are both gases. So how the heck

Barry Barish (05:29.840)

does it make this substance? It's liquid. Yeah, so that has to do with states of matter.

Barry Barish (05:39.440)

I know perhaps LIGO and the thing for which you've gotten the Nobel Prize and the things

Barry Barish (05:46.480)

much of your life work perhaps was a happy accident in some sense in the early days. But

Barry Barish (05:53.040)

is there a moment where you looked up to the stars and also, the same way you wondered about water,

Lex Fridman (05:57.840)

wondered about some of the things that are out there in the universe?

Barry Barish (06:01.600)

Oh, yeah, I think everybody looks and is in awe and is curious about what it is out there. And

Barry Barish (06:10.240)

as I learned more, I learned, of course, that we don't know very much about what's there. And the

Barry Barish (06:17.280)

more we learn, the more we know we don't know. I mean, we don't know what the majority of anything

Barry Barish (06:22.720)

is out there. It's all what we call dark matter and dark energy. And that's one of the big

Barry Barish (06:27.840)

questions. When I was a student, those weren't questions. So we even know less, in a sense,

Barry Barish (06:33.280)

the more we look. So of course, I think that's one of the areas that almost it's universal.

Barry Barish (06:43.200)

People see the sky, they see the stars and they're beautiful and see it looks different

Lex Fridman (06:49.040)

on different nights. And it's a curiosity that we all have.

Lex Fridman (06:54.160)

What are some questions about the universe that in the same way that you felt about the ice

Barry Barish (07:01.600)

that today? You mentioned to me offline, you're teaching a course on the frontiers of science,

Barry Barish (07:07.040)

frontiers of physics. What are some questions outside the ones we'll probably talk about that

Barry Barish (07:12.800)

kind of, yeah, fill you with the, get your flame of curiosity up and firing up, you know,

Barry Barish (07:23.520)

fill you with awe? Well, first, I'm a physicist, not an astronomer. So I'm interested in the

Barry Barish (07:29.280)

physical phenomenon, really. So the question of dark matter and dark energy, which we probably

Barry Barish (07:36.960)

won't talk about, our recent last 20, 30 years, certainly dark energy. Dark energy is a complete

Barry Barish (07:45.360)

puzzle. It goes against what you will ask me about, which is general relativity and Einstein's

Barry Barish (07:53.280)

general relativity. It basically takes something that he thought was what he called a constant,

Barry Barish (08:00.400)

which isn't. And if that's even the right theory, and it represents most of the universe. And then

Barry Barish (08:09.760)

we have something called dark matter, and there's good reason to believe it might be an exotic form

Barry Barish (08:14.480)

of particles. And that is something I've always worked on, on particle accelerators and so forth.

Lex Fridman (08:22.800)

And it's a big puzzle, what it is. It's a bit of a cottage industry in that there's lots and lots

Barry Barish (08:28.320)

of searches, but it may be a little bit like, you know, looking for a treasure under rocks or

Barry Barish (08:34.320)

something. You don't, it's hard to, we don't have really good guidance, except that we have very,

Barry Barish (08:40.640)

very good information that is pervasive and it's there. And that it's probably particles, small,

Barry Barish (08:49.520)

that the evidence is all of those things. But then the most logical solution doesn't seem to work,

Lex Fridman (08:57.200)

something called supersymmetry. And do you think the answer could be something very complicated?

Barry Barish (09:06.400)

You know, I like to hope that, think that most things that appear complicated are actually

Barry Barish (09:12.560)

simple if you really understand them. I think we just don't know at the present time, and it isn't

Barry Barish (09:19.440)

something that affects us. It does affect, it affects how the stars go around each other and so

Barry Barish (09:26.480)

forth, because we detect that there's missing gravity, but it doesn't affect everyday life at

Barry Barish (09:32.960)

all. I tend to think and expect maybe, and that the answers will be simple. We just haven't found

Barry Barish (09:42.480)

it yet. Do you think those answers might change the way we see other sources of gravity, black holes,

Barry Barish (09:49.280)

the way we see the parts of the universe that we do study? It's conceivable. The black holes that

Barry Barish (09:57.280)

we've found in our experiment, we're trying now to understand the origin of those. It's conceivable,

Lex Fridman (10:06.000)

but doesn't seem the most likely that they were primordial, that is, they were made at the

Barry Barish (10:11.360)

beginning. And in that sense, they could represent at least part of the dark matter.

Lex Fridman (10:16.800)

So there can be connections, dark black holes or how many there are, how much of the mass they

Barry Barish (10:23.040)

encompass is still pretty primitive. We don't know. So before I talk to you more about black holes,

Barry Barish (10:28.560)

let me take a step back to, I actually went to high school in Chicago and would go to

Barry Barish (10:34.720)

take classes at Fermilab, watch the buffalo and so on. So let me ask about, you mentioned that Enrico

Barry Barish (10:43.120)

for me was somebody who was inspiring to you in a certain kind of way. Why is that? Can you speak

Barry Barish (10:50.080)

to that? Sure. He was amazing, actually. He's the last, I'll come to the reason in a minute, but

Barry Barish (11:00.960)

he had a big influence on me at a young age. But he was the last physicist of note that was both

Barry Barish (11:11.200)

an experimental physicist and a theorist at the same time. And he did two amazing things within

Barry Barish (11:17.680)

months in 1933. We didn't really know what the nucleus was, what radioactive decay was,

Lex Fridman (11:29.360)

what beta decay was when electrons come out of a nucleus. And near the end of 1933, the neutron had

Barry Barish (11:42.880)

just been discovered. And that meant that we knew a little bit more about what the nucleus is, that

Barry Barish (11:47.680)

it's made out of neutrons and protons. The neutron wasn't discovered till 1932. And then once we

Barry Barish (11:54.640)

discovered that there was a neutron and proton and they made the nucleus and then their electrons

Barry Barish (12:00.160)

that go around, the basic ingredients were there. And he wrote down not only just the theory,

Barry Barish (12:08.240)

a theory, but a theory that lasted decades and has only been improved on of beta decay, that is,

Barry Barish (12:16.560)

the radiation. He did this, came out of nowhere, and it was a fantastic theory. He submitted it

Barry Barish (12:24.480)

to Nature magazine, which was the primary best place to publish even then. And it got rejected

Barry Barish (12:33.040)

as being too speculative. And so he went back to his drawing board in Rome where he was,

Barry Barish (12:42.800)

added some to it, made it even longer, because it's really a classic article, and then published

Barry Barish (12:48.720)

it in the local Italian journal for physics and the German one. At the same time, in January of

Barry Barish (12:58.720)

1932, Giulio and Curie, for the first time, saw artificial radioactivity. This was an important

Barry Barish (13:07.360)

discovery because radioactivity had been discovered much earlier. They had x rays and you

Barry Barish (13:14.080)

shouldn't be using them, but there was radioactivity. People knew it was useful for medicine.

Lex Fridman (13:21.440)

But radioactive materials are hard to find, and so it wasn't prevalent. But if you could make them,

Barry Barish (13:26.960)

they had great use. And Giulio and Curie were able to bombard aluminum or something with alpha

Barry Barish (13:35.440)

particles and find that they excited something that decayed and had some half life and so forth,

Barry Barish (13:44.720)

meaning it was artificial version, or let's call it not a natural version, an induced version of

Barry Barish (13:51.520)

radioactive materials. And Fermi somehow had the insight, and I still can't see where he got it,

Barry Barish (14:05.440)

that the right way to follow that up was not using charged particles like alphas and so forth,

Lex Fridman (14:12.400)

but use these newly discovered neutrons as the bombarding particle. It seemed impossible

Barry Barish (14:19.840)

they barely had been seen. It was hard to get very many of them. But it had the advantage that

Barry Barish (14:26.640)

they're not charged, so they go right into the nucleus. And that turned out to be the experimental

Barry Barish (14:35.840)

work that he did that won him the Nobel Prize. And it was the first step in fission, discovery

Barry Barish (14:42.880)

of fission. And he did this two completely different things, an experiment that was a great

Barry Barish (14:50.000)

idea and a tremendous implementation, because how do you get enough neutrons? And then he learned

Barry Barish (14:58.080)

quickly that not only do you want neutrons, but you want really slow ones. He learned that

Barry Barish (15:04.000)

experimentally, and he learned how to make slow ones, and then they were able to go through the

Barry Barish (15:09.680)

go through the periodic table and make lots of particles. He missed on fission at the moment,

Lex Fridman (15:16.960)

but he had the basic information, and then fission follows soon after that.

Barry Barish (15:21.760)

Forgive me for not knowing, but is the birth of the idea of bombarding with neutrons,

Barry Barish (15:29.200)

is that an experimental idea? Was it born out of an experiment? Did he just observe something,

Lex Fridman (15:35.760)

or is this an Einstein style idea where you come up from basic intuition?

Barry Barish (15:40.160)

I think it took a combination, because he realized that neutrons had a characteristic

Barry Barish (15:46.560)

that would allow them to go all the way into the nucleus when we didn't really understand

Lex Fridman (15:53.760)

what the structure was of all this. So that took an understanding or recognition of the physics

Barry Barish (16:00.640)

itself of how a neutron interacts compared to, say, an alpha particle that Julio and Curie had

Barry Barish (16:06.320)

used. And then he had to invent a way to have enough neutrons, and he had a team of associates,

Lex Fridman (16:16.640)

and he pulled it off quite quickly. So it was pretty astounding.

Lex Fridman (16:21.920)

And probably, maybe you can speak to it, his ability to put together the engineering aspects

Barry Barish (16:28.640)

of great experiments and doing the theory, they probably fed each other. I wonder,

Lex Fridman (16:33.440)

can you speak to why we don't see more of that? Is that just really difficult to do?

Barry Barish (16:38.400)

It's difficult to do. Yeah, I think in both theory and experiment in physics anyway,

Barry Barish (16:47.920)

it was conceivable if you had the right person to do it, and no one's been able to do it since. So

Lex Fridman (16:52.960)

I had the dream that that was what I was going to be like, Fermi.

Lex Fridman (16:56.480)

But you love both sides of it, the theory. Yeah, I never liked the idea that you did

Barry Barish (17:01.680)

experiments without really understanding the theory, or the theory should be related

Barry Barish (17:05.760)

very closely to experiments. And so I've always done experimental work that was closely related

Lex Fridman (17:11.600)

to the theoretical ideas. I think I told you I'm Russian,

Lex Fridman (17:16.640)

so I'm going to ask some romantic questions. But is it tragic to you that he's seen as the

Barry Barish (17:23.440)

architect of the nuclear age, that some of his creations led to potentially, some of his work

Barry Barish (17:30.560)

has led to potentially still the destruction of the human species, some of the most destructive

Barry Barish (17:38.080)

weapons? Yeah, I think even more general than him, I gave you all the virtues of curiosity a few

Barry Barish (17:47.120)

minutes ago. There's an interesting book called The Ratchet of Curiosity. A ratchet is something

Barry Barish (17:52.320)

that goes in one direction. And that is written by a guy who's probably a sociologist or philosopher

Barry Barish (17:59.520)

or something. And he picks on this particular problem, but other ones. And that is the danger

Barry Barish (18:06.080)

of knowledge, basically. You're curious, you learn something. So it's a little bit like

Barry Barish (18:11.040)

curiosity killed the cat. You have to be worried about whether you can handle new information that

Barry Barish (18:16.320)

you get. So in this case, the new information had to do with really understanding nuclear physics.

Lex Fridman (18:22.960)

And that information, maybe we didn't have the sophistication to know how to keep it under

Barry Barish (18:30.240)

control. And Fermi himself was a very apolitical person. So he wasn't very driven by, or at least

Barry Barish (18:41.200)

he appears in all of his writing, the writing of his wife, the interactions that others had with

Barry Barish (18:46.080)

him. Either he avoided it all or he was pretty apolitical. I mean, he just saw the world through

Barry Barish (18:52.000)

kind of the lens of a scientist. But he asked if it's tragic. The bomb was tragic, certainly on

Barry Barish (19:01.120)

Japan. And he had a role in that. So I wouldn't want it as my legacy, for example. But brought

Barry Barish (19:08.640)

it to the human species that it's the ratchet of curiosity that we do stuff just to see what

Barry Barish (19:19.200)

happens. That curiosity, that in sort of my area of artificial intelligence, that's been a concern.

Barry Barish (19:27.840)

On a small scale, on a silly scale, perhaps currently, there's constantly unintended

Barry Barish (19:33.760)

consequences. You create a system and you put it out there and you have intuitions about how

Barry Barish (19:40.240)

it will work. You have hopes how it will work, but you put it out there just to see what happens.

Lex Fridman (19:44.960)

And in most cases, because artificial intelligence is currently not super powerful,

Barry Barish (19:49.680)

it doesn't create a large scale negative effects, but that same curiosity as it progresses might

Barry Barish (19:58.240)

lead to something that destroys the human species. And the same may be true for bioengineering.

Barry Barish (1:00:08.560)

right. So we also work at this frequency. So we basically, why don't we have to do anything other

Barry Barish (1:00:18.080)

than shock absorbers? So we made the world's fanciest shock absorbers, okay? Not just like in

Barry Barish (1:00:26.400)

your car where there's one layer of them. They're just the right squishiness and so forth. They're

Barry Barish (1:00:30.480)

better than what's in the cars. And we have four layers of it. So whatever shakes and gets through

Barry Barish (1:00:35.760)

the first layer, we treat it in a second, third, fourth layer. So it's a mechanical engineering

Barry Barish (1:00:40.880)

problem. Yeah, that's what I said. So it's not, there's no weird tricks to it, like a chemistry

Barry Barish (1:00:46.640)

type thing. No, no. Just, well, the right squishiness, you need the right material inside.

Lex Fridman (1:00:51.840)

And ours look like little springs, but they're. Springs? They're springs? So like legitimately,

Barry Barish (1:00:58.720)

like shock absorbers. Yeah. What? Okay. Okay. And this is now experimental physics at the,

Barry Barish (1:01:06.640)

at its limit. Okay. So you do this and we make the world's fanciest shock absorbers,

Barry Barish (1:01:11.120)

just mechanical engineering. Just mechanical engineering, this is hilarious. But we didn't,

Barry Barish (1:01:16.800)

we weren't good enough to discover gravitational waves. So we did another, we added another

Barry Barish (1:01:25.360)

feature and it's something else that you're aware of, probably have one. And that is to get rid of

Barry Barish (1:01:33.920)

noise. You've probably noise, which is, you don't like. And that's the same principle that's in

Barry Barish (1:01:40.160)

these little Bose earphones. Noise canceling? Noise canceling. So how do they work? They

Barry Barish (1:01:48.240)

basically, you go on an airplane and they sense the ambient noise from the engines

Lex Fridman (1:01:53.600)

and cancel it. Cause it's just the same over and over again. They cancel it. And when the stewardess

Barry Barish (1:01:59.360)

comes and asks you whether you want coffee or tea or a drink or something, you hear, you're fine

Barry Barish (1:02:03.760)

because she's not ambient. She's the signal. So. Are we talking about active canceling? Like where

Barry Barish (1:02:09.040)

are the. Active canceling. So. This is, okay. So another. Don't tell me you have active canceling

Barry Barish (1:02:16.160)

on this. Yeah. Besides the shock absorbers. So we had this, so inside this array of shock absorbers.

Barry Barish (1:02:22.480)

Yeah. We, you asked for some interesting. This is awesome. So inside this, it's harder than the,

Barry Barish (1:02:29.600)

the earphone problem, but it's just engineering. We have to see measure, not just that the

Barry Barish (1:02:36.320)

engine still made noise, but the earth is shaking. It's moving in some direction. So we have to

Barry Barish (1:02:42.880)

actually tell not only that there's noise and cancel it, but what direction it's from. So we

Barry Barish (1:02:48.240)

put this array of seismometers inside this array of shock absorbers and measure the residual motion

Lex Fridman (1:02:58.320)

and its direction. And we put little actuators that push back against it and cancel it.

Barry Barish (1:03:07.040)

This is awesome. So you have the actuators and you have the thing that is sensing the,

Barry Barish (1:03:11.920)

the vibrations and then you have the actual actuators that adjust for that and do so in

Barry Barish (1:03:16.080)

perfect synchrony. Yeah. What if it all works right. And so how much do we reduce the shaking

Barry Barish (1:03:22.080)

of the earth? I mean, one part in 10 to the 12th. One part in 10. So what gets through us is one

Barry Barish (1:03:31.440)

part in 10 to the 12th. That's pretty big reduction. You don't need that in your car,

Lex Fridman (1:03:39.040)

but that's what we do. And so that's how isolated we are from the earth. And that was the biggest,

Lex Fridman (1:03:43.200)

and that was the biggest, I'd say technical problem outside of the physics instrument,

Barry Barish (1:03:49.040)

the interferometer. Can I ask you a weird question here? You make it very poetically

Lex Fridman (1:03:54.480)

and humorously is saying it's just a mechanical engineering problem, but is this one of the

Barry Barish (1:04:01.360)

biggest precision mechanical engineering efforts ever? I mean, this seems exceptionally difficult.

Barry Barish (1:04:09.760)

It is. And so it took a long time. And I think nobody seems to challenge the statement that

Barry Barish (1:04:16.960)

this is the most precision, precise instrument it's ever been built, LIGO.

Lex Fridman (1:04:22.640)

I wonder what like listening to Led Zeppelin sounds on this thing,

Barry Barish (1:04:25.680)

because it's so isolated. I mean, this is like, I don't know.

Lex Fridman (1:04:30.080)

No background. No, no back. It's wow. Wow. Wow. So when you were first

Barry Barish (1:04:37.520)

conceiving this, I would probably, if I was knowledgeable enough,

Lex Fridman (1:04:44.240)

kind of laugh off the possibility that this is even possible.

Lex Fridman (1:04:48.080)

I'm sure, like how many people believe that this is possible? Did you believe this is possible?

Barry Barish (1:04:54.880)

I did. I didn't know that we needed, for sure that we needed active. When we started,

Barry Barish (1:05:00.320)

we did dispassive, but we were doing the tests to develop the active to add as a second stage,

Barry Barish (1:05:08.320)

which we ended up needing. But there was a lot of, you know, now there was a lot of skepticism.

Barry Barish (1:05:15.680)

A lot of us, especially astronomers, felt that money was being wasted,

Barry Barish (1:05:20.400)

because we were also expensive. Doing what I told you is not cheap. So it was kind of

Barry Barish (1:05:26.160)

controversial. It was funded by the National Science Foundation. Can you just linger on this

Barry Barish (1:05:32.240)

just for a little longer? The actuator thing, the act of canceling. Do you remember like little

Lex Fridman (1:05:41.280)

experiments that were done along the way to prove to the team themselves that this is even possible?

Barry Barish (1:05:49.120)

Because I work with quite a bit of robots, and to me, the idea that you could do it this precisely

Barry Barish (1:05:54.080)

is humbling and embarrassing, frankly. Because like, this is another level of precision that I

Barry Barish (1:06:01.520)

can't even, because robots are a mess. And this is basically one of the most precise robots ever.

Barry Barish (1:06:12.800)

Right. So like, is there, do you have any like small scale experiments that were done that just

Barry Barish (1:06:18.240)

be like, this is possible? Yeah, and larger scale. We made a test, that also has to be in vacuum too,

Lex Fridman (1:06:27.040)

but we made test chambers that had this system in it, our first mock of this system, so we could test

Barry Barish (1:06:33.280)

it and optimize it and make it work. But it's just a mechanical engineering problem. Okay.

Lex Fridman (1:06:41.040)

And humans are just ape descendants. I gotcha. I gotcha. Is there any video of this? Like some kind

Barry Barish (1:06:49.280)

of educational purpose visualizations of this act of canceling? I don't think so.

Barry Barish (1:06:58.160)

I mean, does this live on? Well, we work for parts of it, for the active canceling,

Barry Barish (1:07:04.560)

we worked with, for the instruments, for the sensor and instruments, we worked with a small

Barry Barish (1:07:11.680)

company near where you are, because it was our MIT people that got them that were, you know,

Barry Barish (1:07:17.600)

interested in the problem because they thought they might be able to commercialize it for

Barry Barish (1:07:22.240)

making stable tables to make microelectronics, for example, which are limited by how stable the table

Barry Barish (1:07:28.400)

is. I mean, at this point, it's a little expensive. So you never know, never know where this leads.

Lex Fridman (1:07:36.400)

So maybe on the, let me ask you, just sticking it a little longer, this silly old mechanical

Barry Barish (1:07:45.200)

engineering problem. What was to you kind of the darkest moment of what was the hardest

Barry Barish (1:07:53.520)

stumbling block to get over on the engineer side? Like, was there any time where there's a doubt,

Barry Barish (1:07:58.320)

where it's like, I'm not sure we would be able to do this, a kind of engineering challenge that was

Barry Barish (1:08:03.920)

hit? Do you remember anything like that? I think the one that my colleague at MIT,

Barry Barish (1:08:11.680)

Ray Weiss, worked on so hard and was much more of a worry than this. This is only a question if you're

Barry Barish (1:08:18.720)

not doing well enough, you have to keep making it better somehow. But this whole huge instrument has

Barry Barish (1:08:26.400)

to be in vacuum. And the vacuum tanks are, you know, this big around. And so it's the world's

Barry Barish (1:08:34.720)

biggest high vacuum system. And how do you make it? First of all, how do you make this four meter

Barry Barish (1:08:42.720)

long sealed vacuum system? It has to be made out of four kilometers, four kilometers long. Would I

Barry Barish (1:08:48.640)

say something else? Meters. Four kilometers long. Big difference. Yeah. And so, but to make it,

Barry Barish (1:08:55.360)

yeah, we started with a roll of stainless steel, and then we roll it out like a spiral so that

Barry Barish (1:09:04.480)

there's a spiral weld on it. Okay, so the engineering was fine. We did that. We worked through

Lex Fridman (1:09:14.160)

very good companies and so forth to build it. But the big worry was, what if you develop a leak?

Barry Barish (1:09:25.280)

This is a high vacuum, not just vacuum system. Typically, in a laboratory, if there's a leak,

Barry Barish (1:09:31.200)

you put helium around the thing you have, and then you detect where the helium is coming in.

Lex Fridman (1:09:40.000)

But if you have something as big as this, you can't surround it with helium. So you might not

Barry Barish (1:09:44.080)

actually even know that there's a leak and it will be affecting it. Well, we can measure how

Barry Barish (1:09:51.280)

good the vacuum is so we can know that, but a leak can develop and then we don't, how do we fix it

Barry Barish (1:09:58.080)

or how do we find it? And so that was, you asked about a worry. That was always a really big worry.

Barry Barish (1:10:04.880)

What's the difference, you know, high vacuum and a vacuum? What is high vacuum? That's like some

Barry Barish (1:10:11.840)

delta close to vacuum? Is it some threshold? Well, there's a unit. High vacuum is when the vacuum

Lex Fridman (1:10:20.640)

and the units that are used, which are tors, there's 10 to the minus nine. And there's high

Barry Barish (1:10:27.040)

vacuum is usually used in small places. The biggest vacuum system period is at CERN in this

Barry Barish (1:10:35.600)

big particle accelerator, but the high vacuum where they need really good vacuum so particles

Barry Barish (1:10:40.080)

don't scatter in it is smaller than ours. So ours is a really large high vacuum system.

Barry Barish (1:10:47.520)

I don't know. This is so cool. I mean, this is basically by far the greatest listening device

Barry Barish (1:10:53.600)

ever built by human. The fact that like descendants of apes could do this, that evolution started with

Barry Barish (1:10:59.680)

single cell organisms. I mean, is there any more, I'm a huge theory is like, yeah, yeah. But like

Barry Barish (1:11:07.200)

bridges, when I look at bridges from a civil engineering perspective, it's one of the most

Barry Barish (1:11:11.360)

beautiful creations by human beings. It's physics. You're using physics to construct objects that

Barry Barish (1:11:17.200)

can support huge amount of mass and it's like structural, but it's also beautiful.

Lex Fridman (1:11:21.760)

And that humans can collaborate to create that throughout history. And then you take this

Barry Barish (1:11:26.480)

on another level. This is, this is like, it's exciting to me beyond measure that humans can

Barry Barish (1:11:35.040)

create something so precise. But another concept lost in this, you just said, you started talking

Barry Barish (1:11:41.600)

about single cell. Yeah. Okay. You have to realize this discovery that we made that everybody's

Barry Barish (1:11:47.120)

bought off on happened 1.3 billion years ago, somewhere. And then the signal came to us 1.3

Barry Barish (1:11:55.360)

billion years ago, we were just converting on the earth from single cell to multi cell life.

Lex Fridman (1:12:01.440)

So when this actually happened, this collision of two black holes, we weren't here. We weren't

Barry Barish (1:12:07.360)

even close to developing single. Yeah, we were had, we're going from single cell to multi cell

Barry Barish (1:12:14.000)

life at that point. All to meet up at this, at this point. Yeah. Wow. That's like, that's almost

Barry Barish (1:12:20.720)

romantic. It is. Okay. So on the human side of things, it's kind of fascinating because you're

Barry Barish (1:12:32.560)

talking about over a thousand people team for LIGO. Yeah. They started out with, you know,

Barry Barish (1:12:39.040)

around a hundred and you've for parts of the time at least led this team. What does it take to lead

Barry Barish (1:12:48.400)

a team like this of incredibly brilliant theoreticians and engineers and just a lot of

Barry Barish (1:12:56.160)

different parties involved? A lot of egos, a lot of ideas. You had this fun, funny example,

Barry Barish (1:13:03.200)

I forget where, where in publishing a paper, you have to all agree on like, you know, the phrasing

Barry Barish (1:13:10.720)

of a certain sentence or the title of the paper and so on. That's a very interesting, simple

Barry Barish (1:13:15.040)

example. I'd love you to speak to that, but just in general, how, what does it take to lead this

Barry Barish (1:13:20.080)

kind of team? Okay. I think that the general idea is one we all know. You want to, you want to,

Barry Barish (1:13:28.800)

you want to get where the, the sum of something is more than the individual parts is what we say,

Barry Barish (1:13:37.040)

right? Yeah. So that's what you're trying to achieve. Yes. Okay. How do you do that? Actually,

Barry Barish (1:13:42.640)

mostly if we take multiple objects or people, I mean, you put them together, the sum is less.

Barry Barish (1:13:49.280)

Yes. Why? Because they overlap. So you don't have individual things that, you know, this

Barry Barish (1:13:56.400)

person does that, this person does that, then you get exactly the sum. But what you want is to

Barry Barish (1:14:02.320)

develop where you get more than what the individual contributions are. We know that's

Barry Barish (1:14:07.120)

very common. People use that expression everywhere. And it's the expression that has to be kind of

Barry Barish (1:14:14.160)

built into how people feel it's working. Because if you're part of a team, and you realize that

Barry Barish (1:14:21.440)

somehow the team is able to do more than the individuals could do themselves, then they buy on

Barry Barish (1:14:27.440)

kind of in terms of the process. So that's the, that's the goal that you have to have is to, to

Barry Barish (1:14:36.000)

achieve that. And that means that you have to realize parts of what you're trying to do that

Barry Barish (1:14:45.840)

require not that one person couldn't do it, it requires the combined talents to be able to do

Barry Barish (1:14:52.240)

something that neither of them could do themselves. And we have a lot of that kind of thing. And I

Barry Barish (1:14:57.200)

think, I mean, build into the some of the examples that I gave you. And so, how do you then, so, so

Barry Barish (1:15:06.320)

the key almost in anything you do is the people themselves, right? So in our case,

Barry Barish (1:15:12.400)

the first and most important was to attract to spend years of their life on this. And the best

Barry Barish (1:15:20.880)

possible people in the world to do it. So the only way to convince them is that somehow it's

Barry Barish (1:15:28.800)

better and more interesting for them than what they could do themselves. And so that's part of

Barry Barish (1:15:34.080)

this idea. Yeah, that's powerful. But nevertheless, there's best people in the world, there's egos. Is

Barry Barish (1:15:42.240)

there something to be said about managing egos? Oh, that's the human problem is always the hardest.

Lex Fridman (1:15:47.840)

And so there's, that's an art, not a science, I think. I think the fact here that combined,

Barry Barish (1:15:56.080)

there's a was a romantic goal that we had to, you know, do something that people hadn't done before,

Barry Barish (1:16:06.240)

which was important scientifically and, and a huge challenge, enabled us to say, take and get, I mean,

Lex Fridman (1:16:19.600)

what we did just to take an example, we use the light to go in this thing comes from lasers.

Barry Barish (1:16:24.320)

We need a certain kind of laser. So the kind of laser that we use, there were three different

Barry Barish (1:16:32.560)

institutions in the world that had the experts that do this, maybe in competition with each other.

Lex Fridman (1:16:38.240)

So we got all three to join together and work with us to work on this as an example. So that

Barry Barish (1:16:45.040)

you had, and they had the thing that they were working together on a kind of object that they

Barry Barish (1:16:51.680)

wouldn't have otherwise. And we're part of a bigger team where they could discover something

Barry Barish (1:16:57.280)

that isn't even engineers. These are engineers that do laser. So, and they're part of our laser

Barry Barish (1:17:03.520)

physicists. So could you describe the moment or the period of time when finally this incredible

Barry Barish (1:17:14.480)

creation of human beings led to a detection of gravitational waves? It's a long story. Unfortunately,

Barry Barish (1:17:22.160)

this is a part that we started failures along the way kind of thing or all failures. That's all

Barry Barish (1:17:28.560)

that's built into it. If you're not, if you're not mechanical engineering, you build on your failures,

Barry Barish (1:17:36.080)

that's expected. So we're trying things that no one's done before. So it's technically not just

Barry Barish (1:17:41.360)

gravitational waves. And so it's built on failures. But anyway, we did before me, even

Barry Barish (1:17:48.480)

there, the people did R&D on the concepts. But starting in 1994, we got money from the National

Barry Barish (1:17:57.920)

Science Foundation to build this thing. It took about five years to build it. So by 1999, we had

Barry Barish (1:18:06.240)

built the basic unit. It did not have active seismic isolation at that stage, didn't have some

Barry Barish (1:18:13.920)

other things that we have now. What we did at the beginning was stick to technologies that we had

Barry Barish (1:18:27.360)

at least enough knowledge that we could make work or had tested in our own laboratories. And so then

Barry Barish (1:18:33.840)

we put together the instrument. We made it work. It didn't work very well, but it worked. And we

Barry Barish (1:18:41.040)

didn't see any gravitational waves. Then we figured out what limited us. And we went through this

Barry Barish (1:18:45.600)

every year for almost 10 years, never seeing gravitational waves. We would run it, looking for

Barry Barish (1:18:55.520)

gravitational waves for months, learn what limited us, fix it for months, and then run it again.

Barry Barish (1:19:06.320)

Eventually, we knew we had to take another big step. And that's when we made several changes,

Barry Barish (1:19:13.280)

including adding these active seismic isolation, which turned out to be a key. And we

Barry Barish (1:19:21.600)

fortunately got the National Science Foundation to give us another couple hundred million dollars,

Barry Barish (1:19:27.520)

100 million more. And we rebuild it or fixed or improved it. And then in 2015, we turned it on.

Lex Fridman (1:19:42.080)

And we almost instantly saw this first collision of two black holes.

Lex Fridman (1:19:53.600)

And then we went through a process of, do we believe what we've seen?

Barry Barish (1:19:58.560)

Yeah, I think you're one of the people that went through that process. It sounds like some people

Barry Barish (1:20:02.400)

immediately believed it. And then you're like...

Lex Fridman (1:20:05.600)

So as human beings, we all have different reactions to almost anything. And so

Barry Barish (1:20:10.080)

quite a few of my colleagues had a eureka moment immediately. I mean, the figure that we put in our

Barry Barish (1:20:20.160)

paper, first is just data. We didn't have to go through fancy computer programs to do anything.

Lex Fridman (1:20:27.840)

And we show next to it the calculations of Einstein's equations. It looks just like what

Barry Barish (1:20:36.080)

we detected. And we did it in two different detectors halfway across the US. So it was

Barry Barish (1:20:42.000)

pretty convincing, but you don't want to fool yourself. So being a scientist, for me, we had

Barry Barish (1:20:53.920)

to go through and try to understand that the instrument itself, which was new, I said we had

Barry Barish (1:20:58.000)

rebuild it, couldn't somehow generate things that look like this. That took some tests. And then the

Barry Barish (1:21:06.240)

second, you'll appreciate more, we had to somehow convince ourselves we weren't hacked in some

Barry Barish (1:21:12.080)

clever way.

Lex Fridman (1:21:12.800)

Cybersecurity question.

Barry Barish (1:21:14.320)

Yeah. Even though we're not on the internet, but...

Barry Barish (1:21:18.000)

Yeah. No, it can be physical access too. Yeah. That's fascinating. It's fascinating that you

Barry Barish (1:21:23.520)

would think about that. I mean, not enough. I mean, because it matches prediction. So the chances

Lex Fridman (1:21:34.560)

of it actually being manipulated is very, very low. But nevertheless...

Barry Barish (1:21:38.320)

We still could have disgruntled all the graduate students who had worked with us earlier that...

Barry Barish (1:21:43.520)

Who want you to... I don't know how that's supposed to embarrass you. I suppose, yeah. I suppose I

Barry Barish (1:21:48.880)

see. But about what I think you said, within a month, you kind of convinced yourself officially.

Barry Barish (1:21:55.360)

Within a month, we convinced ourselves. We kept a thousand collaborators quiet during that time.

Barry Barish (1:22:01.520)

Then we spent another month or so trying to understand what we'd seen so that we could do the

Barry Barish (1:22:10.080)

science with it instead of just putting it out to the world and let somebody else understand that it

Barry Barish (1:22:14.480)

was two black holes and what it was. The fact that a thousand collaborators were quiet

Barry Barish (1:22:20.480)

is a really strong indication that this is a really close knit team. Yeah. And they're around

Barry Barish (1:22:25.600)

the world. Either strong knit or tight knit or had a strong dictatorship or something. Yeah.

Barry Barish (1:22:35.200)

Either fear or love. You can rule by fear or love. Yeah, right. You can go back to Machiavelli.

Barry Barish (1:22:39.120)

Yeah. All right. Well, this is really exciting that that's a success story because it didn't

Barry Barish (1:22:51.760)

have to be a success story, right? I mean, eventually, perhaps you could say it'll be an

Barry Barish (1:22:56.720)

event, but it could have taken over a century to get there. Oh, yeah. Yeah. And it's only downhill

Barry Barish (1:23:06.160)

now. What do you mean? You mean with gravitational waves? Yeah. Well, now we're off because of the

Barry Barish (1:23:18.240)

pandemic, but when we turned off, we were seeing some sort of gravitational wave event each week.

Barry Barish (1:23:26.880)

Now we're fixing, we're adding features where it'll probably be when we turn back on next year,

Barry Barish (1:23:32.560)

it'll probably be one every couple days. And they're not all the same. So it's

Barry Barish (1:23:38.160)

learning about what's out there in gravity instead of just optics. So it's all great.

Barry Barish (1:23:45.840)

We're only limited by the fantastic thing other than that this is a great field and it's all new

Lex Fridman (1:23:54.880)

and so forth is that experimentally, the great thing is that we're limited by technology and

Barry Barish (1:24:04.000)

technical limitations, not by science. So another really important discovery that was made before

Barry Barish (1:24:16.400)

ours was what's called the Higgs boson made on the big accelerator at CERN. This huge accelerator,

Barry Barish (1:24:23.200)

they discovered a really important thing. We have Einstein's equation, E equals MC squared.

Lex Fridman (1:24:29.920)

So energy makes mass or mass can make energy and that's the bomb. But the mechanism by which that

Barry Barish (1:24:37.040)

happens, not vision, but how do you create mass from energy was never understood until there was

Barry Barish (1:24:48.560)

a theory of it about 70 years ago now. And so they discovered it's named after a man named Higgs.

Barry Barish (1:24:58.400)

It's called the Higgs boson. And so it was discovered, but since that time, and I worked

Barry Barish (1:25:05.120)

on those experiments since that time, they haven't been able to progress very much further,

Barry Barish (1:25:09.920)

a little bit, but not a lot further. And the difference is that we're really lucky

Barry Barish (1:25:14.240)

we're in what we're doing in that there you see this Higgs boson, but there's tremendous amount

Barry Barish (1:25:22.880)

of other physics that goes on and you have to pick out the needle in the haystack of physics.

Barry Barish (1:25:28.080)

You can't make the physics go away, it's there. In our case, we have a very weak signal, but once we

Barry Barish (1:25:34.480)

get good enough to see it, it's weak compared to where we've reduced the background, but the

Barry Barish (1:25:40.080)

background is not physics, it's just technology. It's getting ourselves better isolated from the

Barry Barish (1:25:47.600)

Earth or getting a more powerful laser. And so since 2015, when we saw the first one,

Barry Barish (1:25:56.160)

we continually can make improvements that are enabling us to turn this into a real science

Barry Barish (1:26:03.040)

to do astronomy, a new kind of astronomy. It's a little like astronomy. Galileo started the field.

Barry Barish (1:26:12.560)

He basically took lenses that were made for classes and he didn't invent the first telescope,

Lex Fridman (1:26:20.080)

but made a telescope, looked at Neptune and saw that it had four moons. That was the birth of

Barry Barish (1:26:28.880)

not just using your eyes to understand what's out there. And since that time, we've made better and

Barry Barish (1:26:34.880)

better telescopes, obviously, and astronomy thrives. And in a similar way, we're starting to

Barry Barish (1:26:41.920)

be able to crawl, but we're starting to be able to do that with gravitational waves. And it's

Barry Barish (1:26:49.920)

going to be more and more that we can do as we can make better and better instruments because,

Barry Barish (1:26:55.600)

as I say, it's not limited by picking it out of others. Yeah, it's not limited by the physics.

Lex Fridman (1:27:02.400)

So you have an optimism about engineering that as human progress marches on,

Lex Fridman (1:27:11.040)

engineering will always find a way to build a large enough device,

Barry Barish (1:27:17.280)

accurate enough device to detect the same thing. As long as it's not limited by physics,

Barry Barish (1:27:21.360)

yeah, they'll do it. So you, two other folks and the entire team won the Nobel prize for this big

Barry Barish (1:27:34.720)

effort. There's a million questions I can ask for, but looking back, where does the Nobel prize

Barry Barish (1:27:49.680)

fit into all of this? If you think hundreds of years from now, I venture to say that people

Barry Barish (1:27:57.920)

will not remember the winners of a prize, but they'll remember creations like these.

Barry Barish (1:28:03.360)

Maybe I'm romanticizing engineering, but I guess I want to ask how important is the Nobel prize in

Barry Barish (1:28:10.880)

all of this? Well, that's a complicated question. As a physicist, it's something if you're trying

Barry Barish (1:28:22.240)

to win a Nobel prize, forget it because they give one a year. So there's been 200 physicists

Barry Barish (1:28:30.960)

who have won the Nobel prize since 1900. And so things just have to fall right. So your goal cannot

Barry Barish (1:28:40.240)

be to win a Nobel prize. It wasn't my dream. It's tremendous for science. Why the Nobel prize for a

Barry Barish (1:28:51.600)

guy that made dynamite and stuff is what it is. It's a long story, but it's the one day a year

Barry Barish (1:28:58.400)

where actually the science that people have done is all over the world and so forth. Forget about

Barry Barish (1:29:04.720)

the people again. It is really good for science. It celebrates science for several days, different

Barry Barish (1:29:14.080)

fields, chemistry, medicine and so forth. And everybody doesn't understand everything about

Barry Barish (1:29:21.280)

these. They're generally fairly abstract, but then it's on the front page of newspapers around

Barry Barish (1:29:27.760)

the world. So it's really good for science. It's not easy to get science on the front page of the

Barry Barish (1:29:32.080)

New York Times. It's not there. Should be, but it's not. And so the Nobel prize is important in that

Barry Barish (1:29:41.760)

way. Otherwise, I have a certain celebrity that I didn't have before. And now you get to be a

Barry Barish (1:29:53.520)

celebrity that advertises science. It's a mechanism to remind us how incredible, how much credit

Barry Barish (1:30:01.280)

science deserves and everything. Well, it has a little bit more. One thing I didn't expect,

Barry Barish (1:30:06.240)

which is good, is that we have a government. I'm not picking on ours necessarily, but it's true of

Barry Barish (1:30:16.720)

all governments are not run by scientists. In our case, it's run by lawyers and businessmen.

Barry Barish (1:30:23.040)

Yep. Okay. And at best they may have an aide or something that knows a little science. So

Lex Fridman (1:30:33.120)

in all countries hardly take into account science in making decisions.

Barry Barish (1:30:42.640)

Yes. Okay. And

Barry Barish (1:30:44.320)

having a Nobel prize, the people in those positions actually listen. So you have more

Barry Barish (1:30:53.200)

influence. I don't care whether it's about global warming or what the issue is. There's some

Barry Barish (1:30:58.160)

influence, which is lacking otherwise. And people pay attention to what I say. If I talk about

Barry Barish (1:31:05.120)

global warming, they wouldn't have before I had the Nobel prize. Yeah, this is very true. You're

Barry Barish (1:31:12.160)

like the celebrities who talk. Celebrity has power. Celebrity has power. And that's a good

Barry Barish (1:31:20.000)

thing. That's a good thing. Singling out people, I mean, on the other side of it, singling out

Barry Barish (1:31:24.880)

people has all kinds of, whether it's for Academy Awards or for this, have unfairness and

Barry Barish (1:31:32.320)

arbitrariness and so forth and so on. So that's the other side of the coin. Just like you said,

Barry Barish (1:31:39.920)

especially with the huge experimental projects like this, you know, it's a large team and it

Barry Barish (1:31:45.280)

does the nature of the Nobel prizes. It singles out a few individuals to represent the team.

Barry Barish (1:31:49.760)

Yeah. Nevertheless, it's a beautiful thing. What are ways to improve LIGO in the future,

Barry Barish (1:31:57.440)

increase the sensitivity? I've seen a few ideas that are kind of fascinating. Are you interested

Barry Barish (1:32:03.520)

in them? I'm not speaking about five years. Perhaps you could speak to the next five years,

Lex Fridman (1:32:09.680)

but also the next hundred years. Yeah. So let me talk to both the instrument and the science.

Barry Barish (1:32:16.080)

Sure. So they go hand in hand. I mean, the thing that I said is if we make it better,

Barry Barish (1:32:21.920)

we see more kinds of weaker objects and we do astronomy. Okay. We're very motivated to make

Barry Barish (1:32:29.760)

a new instrument, which will be a big step, the next step, like making a new kind of telescope or

Barry Barish (1:32:36.240)

something. And the ideas of what that instrument should be haven't converged yet. There's different

Barry Barish (1:32:44.400)

ideas in Europe. They've done more work to kind of develop the ideas, but they're different from

Barry Barish (1:32:52.480)

ours and we have ideas. But I think over the next few years, we'll develop those. The idea is to make

Barry Barish (1:32:59.840)

an instrument that's at least 10 times better than what we can do with this instrument, 10 times

Barry Barish (1:33:06.240)

better than that. 10 times better means you can look 10 times further out. 10 times further out

Barry Barish (1:33:13.600)

is a thousand times more volume. So you're seeing much, much more of the universe. The best way to

Barry Barish (1:33:21.680)

look at it is to look further out. The big change is that if you can see far out, you see further

Barry Barish (1:33:29.280)

back in history. Yeah, you're traveling back in time. Yeah. And so we can start to do what we

Barry Barish (1:33:36.080)

call cosmology instead of astronomy or astrophysics. Cosmology is really the study of the evolution of

Barry Barish (1:33:44.160)

the universe. And so then you can start to hope to get to the important problems having to do with

Lex Fridman (1:33:53.920)

how the universe began, how it evolved and so forth, which we really only study now with

Barry Barish (1:34:02.160)

optical instruments or electromagnetic waves. And early in the universe, those were blocked because

Barry Barish (1:34:12.320)

it was, basically it wasn't transparent. So the photons couldn't get out when everything was too

Barry Barish (1:34:18.960)

dense. What do you think, sorry on this tangent, what do you think an understanding of gravitational

Barry Barish (1:34:24.240)

waves from earlier in the universe can help us understand about the Big Bang and all that kind

Barry Barish (1:34:28.560)

of stuff? Yeah. But it's a non, it's another perspective on the thing. Is there some insights

Barry Barish (1:34:37.120)

you think could be revealed just to help a layman understand? Sure. First, we don't understand. We

Barry Barish (1:34:43.040)

use the word Big Bang. We don't understand the physics of what the Big Bang itself was.

Lex Fridman (1:34:50.320)

So I think, and in the early stage, there were particles and there was a huge amount of gravity

Lex Fridman (1:34:58.160)

and mass being made. So I'll say two things. One is, how did it all start? How did it happen? I'll

Barry Barish (1:35:10.240)

give you at least one example that we don't understand what we should understand. We don't

Barry Barish (1:35:16.000)

know why we're here. Yes. No, we do not. I don't mean it philosophically. I mean it in terms of

Barry Barish (1:35:24.000)

physics. Now, what do I mean by that? If I go into my laboratory at CERN or somewhere and I

Barry Barish (1:35:30.720)

collide particles together or put energy together, I make as much anti matter as matter. Anti matter

Barry Barish (1:35:38.480)

then annihilates matter and makes energy. So in the early universe, you made somehow a lot of

Barry Barish (1:35:49.120)

matter and anti matter, but there was an asymmetry. Somehow there was more matter and anti matter.

Barry Barish (1:35:55.520)

The matter and anti matter annihilated each other. At least that's what we think.

Lex Fridman (1:35:59.520)

And there was only matter leftover. And we live in a universe that we see this all matter.

Barry Barish (1:36:05.840)

We don't have any idea. We have ideas, but we don't have any way to understand that at the

Barry Barish (1:36:12.640)

present time with the physics that we know. Can I ask a dumb question? Does anti matter have

Barry Barish (1:36:19.600)

anything like a gravitational field to send signals? So how does this asymmetry of matter

Lex Fridman (1:36:29.040)

and anti matter could be investigated or further understood by observing gravitational fields or

Barry Barish (1:36:35.520)

weirdnesses in gravitational fields? I think that in principle, if there were anti neutron stars,

Barry Barish (1:36:45.360)

instead of just neutron stars, we would see different kinds of signals, but it didn't get

Barry Barish (1:36:51.280)

to that. We live in a universe that we've done enough looking because we don't see anti matter,

Barry Barish (1:36:56.960)

anti protons anywhere, no matter what we look at, that it's all made out of matter.

Barry Barish (1:37:01.280)

Hmm. There is no anti matter except when we go in our laboratories.

Lex Fridman (1:37:06.400)

So, but when we go in our laboratories, we make as much anti matter as matter.

Lex Fridman (1:37:11.280)

So there's something about the early universe that made this asymmetry. So we can't even

Barry Barish (1:37:16.320)

explain why we're here. That's what I meant. Physics wise, not in terms of how we evolved

Lex Fridman (1:37:25.360)

and all that kind of stuff. So there might be inklings of some of the physics that gravitational

Lex Fridman (1:37:36.080)

So gravitational waves don't get obstructed like light. So I said light only goes to 300,000 years.

Lex Fridman (1:37:42.720)

So it goes back to the beginning. So if you could study the early universe with gravitational waves,

Barry Barish (1:37:47.520)

we can't do that yet. Then it took 400 years to be able to do that with optical, but

Lex Fridman (1:37:54.240)

but then you can really understand the very, maybe understand the very early universe.

Lex Fridman (1:38:00.400)

So in terms of questions like why we're here or what the big bang was, we should be, we can,

Barry Barish (1:38:10.400)

in principle, study that with gravitational waves. So to keep moving in this direction,

Lex Fridman (1:38:15.360)

it's a unique kind of way to understand our universe.

Lex Fridman (1:38:20.400)

So you think there's more Nobel prize level ideas to be discovered in relation to

Barry Barish (1:38:25.200)

I'd be shocked if there, if there isn't, not even going to that, which is a very long range problem.

Lex Fridman (1:38:31.680)

But I think that we only see with electromagnetic waves, 4% of what's out there.

Barry Barish (1:38:39.280)

There must be, we looked for things that we knew should be there. There should be,

Barry Barish (1:38:48.240)

I would be shocked if there wasn't physics, objects, science, and with gravity that doesn't

Barry Barish (1:38:58.960)

show up in everything we do with telescopes. So I think we're just limited by not having

Barry Barish (1:39:06.480)

powerful enough instruments yet to do this.

Lex Fridman (1:39:10.400)

Do you have a preference? I keep seeing this E. Lisa idea.

Barry Barish (1:39:17.200)

Yeah.

Lex Fridman (1:39:18.240)

Is it, do you have a preference for earthbound or space faring mechanisms for?

Barry Barish (1:39:26.960)

They're complimentary. It's a little bit like, it's completely analogous to what's been done

Barry Barish (1:39:32.880)

in astronomy. So astronomy from the time of Galileo was done with visible light.

Barry Barish (1:39:42.000)

The big advances in astronomy in the last 50 years are because we have instruments that look

Barry Barish (1:39:46.560)

at the infrared, microwave, ultraviolet and so forth. So looking at different wavelengths

Barry Barish (1:39:54.160)

has been important. Basically going into space means that we'll look at instead of the audio

Barry Barish (1:40:00.240)

band, which we look at, as we said on the Earth's surface, we'll look at lower frequencies.

Lex Fridman (1:40:05.680)

So it's completely complimentary and it starts to be looking at different frequencies just

Lex Fridman (1:40:10.960)

like we do with astronomy.

Barry Barish (1:40:14.320)

It seems almost incredible to me, engineering wise, just like on earth to send something

Lex Fridman (1:40:18.960)

that's kilometers across into space. Is that harder to engineer?

Barry Barish (1:40:25.360)

It actually is a little different. It's three satellites separated by hundreds of thousands

Barry Barish (1:40:32.880)

of kilometers and they send a laser beam from one to the other. And if the triangle changes

Barry Barish (1:40:42.960)

shape a little bit, they detect that from a graph.

Barry Barish (1:40:45.360)

Did you say hundreds of thousands of kilometers? Yeah. Sending lasers to each other. Okay.

Barry Barish (1:40:56.160)

It's just engineering.

Lex Fridman (1:40:59.920)

Is it possible though? Is it doable?

Barry Barish (1:41:02.160)

Yes.

Barry Barish (1:41:03.520)

Okay. That's just incredible because they have to maintain, I mean, the precision here

Barry Barish (1:41:11.040)

is probably, there might be some more, what is it? Maybe noise is a smaller problem. I

Barry Barish (1:41:16.800)

guess there's no vibration to worry about like seismic stuff. So getting away from earth,

Barry Barish (1:41:22.880)

maybe you get away from seismic stuff.

Barry Barish (1:41:23.680)

Yeah. Those parts are easier. They don't have to measure it as accurately at low frequencies.

Lex Fridman (1:41:29.200)

But they have a lot of tough engineering problems.

Barry Barish (1:41:33.200)

In order to detect that the gravitational waves affect things, the sensors have to be

Lex Fridman (1:41:44.000)

what we call free masses, just like ours, are isolated from the earth. They have to

Barry Barish (1:41:48.400)

isolate it from the satellite. And that's a hard problem. They have to do that pretty,

Barry Barish (1:41:54.080)

not as well as we have to do it, but very well. And they've done a test mission and

Barry Barish (1:42:00.080)

the engineering seems to be at least in principle in hand. This will be in the 2030s.

Lex Fridman (1:42:06.880)

2030s?

Lex Fridman (1:42:07.920)

Yeah.

Barry Barish (1:42:09.600)

This is incredible. This is incredible. Let me ask about black holes.

Lex Fridman (1:42:17.200)

So what we're talking about is observing orbiting black holes. I saw the terminology of like

Barry Barish (1:42:27.440)

binary black hole systems.

Lex Fridman (1:42:28.880)

Binary black holes.

Barry Barish (1:42:29.680)

Is that the one that's when they're dancing? Okay.

Lex Fridman (1:42:33.040)

They're both going around each other, just like the earth around the sun.

Lex Fridman (1:42:36.080)

Okay. Is that weird that there's black holes going around each other?

Lex Fridman (1:42:40.080)

So the finding binary systems of stars is similar to finding binary systems of...

Barry Barish (1:42:45.840)

Of black holes.

Barry Barish (1:42:46.560)

Well, they were once stars. So we haven't said what a black hole is physically yet.

Lex Fridman (1:42:55.760)

Yeah. What's a black hole?

Lex Fridman (1:42:56.880)

So black hole is first, it's a mathematical concept or a physical concept. And that is

Barry Barish (1:43:03.840)

a region of space. So it's simply a region of space where the curvature of space time,

Barry Barish (1:43:10.640)

meaning the gravitational field is so strong that nothing can get out, including light.

Lex Fridman (1:43:19.040)

And there's light gets bent if the space time is warped enough.

Lex Fridman (1:43:26.320)

And so even light gets bent around and stays in it. So that's the concept of a black hole.

Lex Fridman (1:43:33.200)

And maybe you can make... So that's a concept that didn't say how they come about.

Lex Fridman (1:43:40.400)

And there could be different ways they come about. The ones that we are seeing,

Barry Barish (1:43:48.480)

we're not sure. That's what we're trying to learn now is what they...

Lex Fridman (1:43:52.480)

But the general expectation is that they come... These black holes happen when a star dies.

Lex Fridman (1:44:02.000)

So what does that mean that a star dies? What happens? A star like our sun

Barry Barish (1:44:08.880)

basically makes heat and light by fusion. It's made up. And as it burns, it burns up the hydrogen

Lex Fridman (1:44:17.600)

and then the helium and slowly works its way up to the heavier and heavier elements that are

Barry Barish (1:44:24.240)

in the star. And when it gets up to iron, the fusion process doesn't work anymore.

Lex Fridman (1:44:30.560)

And so the stars die and that happens to stars. And then they do what's called a supernova.

Lex Fridman (1:44:37.200)

What happens then is that a star is a delicate balance between an outward pressure from fusion

Lex Fridman (1:44:43.760)

and light and burning and an inward pressure of gravity trying to pull the

Barry Barish (1:44:51.120)

masses together. Once it burns itself out, it goes and it collapses and that's a supernova.

Barry Barish (1:44:57.760)

When it collapses, all the mass that was there is in a very much smaller space. And if a star,

Barry Barish (1:45:05.440)

if you do the calculations, if a star is big enough, that can create a strong enough

Barry Barish (1:45:11.680)

gravitational field to make a black hole. Our sun won't. It's too small.

Lex Fridman (1:45:17.920)

Too small.

Lex Fridman (1:45:19.200)

And we don't know exactly what, but it's usually thought that a star has to be at least three

Barry Barish (1:45:26.400)

times as big as our sun to make a black hole. But that's the physical way there.

Barry Barish (1:45:32.160)

You can make black holes. That's the first

Lex Fridman (1:45:34.800)

explanation that one would give for what we see,

Lex Fridman (1:45:41.840)

but it's not necessarily true. We're not sure yet.

Lex Fridman (1:45:45.440)

What we see in terms of, for the origins of black holes?

Barry Barish (1:45:48.560)

No, the black holes that we see in gravitational waves.

Lex Fridman (1:45:52.320)

So the, but you're also looking for the ones who are binary solar systems.

Lex Fridman (1:45:56.720)

So they're binary systems, but they could have been made from binary stars. So there's binary

Barry Barish (1:46:01.760)

stars around. So that's, so that's the first explanation is that that's what they are.

Barry Barish (1:46:07.520)

Gotcha.

Barry Barish (1:46:09.760)

Other explanations, but what we see has some puzzles. This is kind of the way science works,

Barry Barish (1:46:16.800)

I guess. We see heavier ones than up to, we've seen one system that was 140 times the mass of

Barry Barish (1:46:29.280)

our own sun. That's not believed to be possible with the parent being a big star because big

Barry Barish (1:46:39.760)

stars can only be so big or they are unstable. It's just the fact that they live in an environment

Barry Barish (1:46:49.120)

that makes them unstable. So the fact that we see bigger ones, they may be come from something else.

Barry Barish (1:46:55.920)

It's possible that they were made in a different way by little ones eating each other up or maybe

Barry Barish (1:47:04.800)

they were made or maybe they came with the big bang. The prime, what we call primordial, which

Barry Barish (1:47:11.600)

means they're really different. They came from that. We don't know at this point if they came

Barry Barish (1:47:16.160)

with a big bang, then maybe they account for what we call dark matter or some of it.

Barry Barish (1:47:21.040)

Hmm. Like there was a lot of them if they came with it because there's a lot of dark matter.

Lex Fridman (1:47:26.080)

Yeah.

Lex Fridman (1:47:27.360)

But will gravitational waves give you any kind of intuition about the origin of these oscillating?

Barry Barish (1:47:34.240)

We think that if we see the distributions enough of them, the distributions of their

Barry Barish (1:47:40.320)

masses, the distributions of how they're spinning, so we can actually measure when they're going

Barry Barish (1:47:45.760)

around each other, whether they're spinning like this or whether the whole system has any wobbles.

Barry Barish (1:47:55.680)

What? So this is now. Okay.

Lex Fridman (1:48:00.400)

We're doing that.

Lex Fridman (1:48:01.280)

And then you're constantly kind of crawling back and back in time.

Lex Fridman (1:48:04.400)

And we're crawling back in time and seeing how many there are as we go back. And so do they

Barry Barish (1:48:09.920)

point back.

Lex Fridman (1:48:10.480)

So you're like, what is that discipline called, cartography or something? You're like mapping

Barry Barish (1:48:15.920)

this, the early universe via the lens of gravitational waves.

Lex Fridman (1:48:21.920)

Not yet the early universe, but at least back in time.

Barry Barish (1:48:24.080)

Earlier.

Barry Barish (1:48:24.720)

Yeah. So black holes are this mathematical phenomenon, but they come about in different

Barry Barish (1:48:32.960)

ways. We have a huge black hole at the center of our galaxy and other galaxies. Those probably

Barry Barish (1:48:39.600)

were made some other way. We don't know when the galaxies themselves had to do with the

Barry Barish (1:48:44.160)

formation of galaxies. We don't really know. So the fact that we use the word black hole,

Barry Barish (1:48:50.240)

the origin of black holes might be quite different depending on how they happen. They just have

Barry Barish (1:48:56.480)

to in the end have a gravitational field that will bend everything in.

Lex Fridman (1:49:01.200)

How do you feel about black holes as a human being? There's this thing that's nearly

Barry Barish (1:49:06.720)

infinitely dense, doesn't let light escape. Isn't that kind of terrifying? It feels like

Lex Fridman (1:49:13.680)

the stuff in nightmares.

Barry Barish (1:49:14.960)

I think it's an opportunity.

Lex Fridman (1:49:19.040)

To do what exactly?

Lex Fridman (1:49:21.360)

So like the early universe is an opportunity. If we can study the early universe, we can

Barry Barish (1:49:26.800)

learn things like I told you. And here again, we have an embarrassing situation in physics.

Barry Barish (1:49:32.720)

We have two wonderful theories of physics, one based on quantum mechanics, quantum field

Barry Barish (1:49:39.920)

theory. And we can go to a big accelerator like at CERN and smash particles together

Lex Fridman (1:49:46.000)

and almost explain anything that happens beautifully using quantum field theory and

Barry Barish (1:49:51.840)

quantum mechanics. Then we have another theory of physics called general relativity, which

Barry Barish (1:49:57.200)

is what we've been talking about most of the time, which is fantastic at describing the

Barry Barish (1:50:02.160)

things at high velocities, long distances, and so forth. So that's not the way it's

Barry Barish (1:50:12.000)

supposed to be. We're trying to create a theory of physics, not two theories of physics.

Lex Fridman (1:50:18.480)

So we have an embarrassment that we have two different theories of physics. People have

Barry Barish (1:50:22.960)

tried to make a unified theory, what they call a unified theory. You've heard those

Barry Barish (1:50:28.080)

words for decades. They still haven't. That's been primarily done theoretically or tried.

Barry Barish (1:50:36.560)

People actively do that. My personal belief is that like much of physics, we need some

Barry Barish (1:50:44.640)

clues. So we need some experimental evidence. So where is there a place? If we go to CERN

Lex Fridman (1:50:51.280)

and do those experiments, gravitational waves or general relativity don't matter. If we

Barry Barish (1:50:56.160)

go to study our black holes, elementary particle physics doesn't matter. We're studying these

Lex Fridman (1:51:02.560)

huge objects. So where might we have a place where both phenomena have to be satisfied?

Barry Barish (1:51:09.120)

An example is black holes. Inside black holes. Yeah. So we can't do that today. But when

Barry Barish (1:51:15.920)

I think of black hole, it's a potential treasure chest of understanding the fundamental problems

Barry Barish (1:51:24.160)

of physics and maybe can give us clues to how we bring to the embarrassment of having

Barry Barish (1:51:32.800)

two theories of physics together. That's my own romantic idea. What's the worst that could

Barry Barish (1:51:38.960)

happen? It's so enticing. Just go in and look. Do you think, how far are we away from

Lex Fridman (1:51:45.040)

figuring out the unified theory of physics, the theory of everything? What's your sense?

Barry Barish (1:51:50.880)

Who will solve it? Like what discipline will solve it? Yeah. I think so little progress

Barry Barish (1:52:02.080)

has been made without more experimental clues, as I said, that we're just not able to say

Barry Barish (1:52:16.080)

that we're close without some clues. The most popular theory these days that might lead

Barry Barish (1:52:26.320)

to that is called string theory. The problem with string theory is it solves a lot of beautiful

Barry Barish (1:52:34.440)

mathematical problems we have in physics. It's very satisfying theoretically, but it

Barry Barish (1:52:46.720)

has almost no predictive, maybe no predictive ability because it is a theory that works

Barry Barish (1:52:53.840)

in 11 dimensions. We live in a physical world of three space and one time dimension. In

Barry Barish (1:53:02.080)

order to make predictions in our world with string theory, you have to somehow get rid

Barry Barish (1:53:08.720)

of these other seven dimensions. That's done mathematically by saying they curl up on each

Barry Barish (1:53:15.280)

other on scales that are too small to affect anything here. That's an okay argument, but

Lex Fridman (1:53:23.400)

how you do that is not unique. That means if I start with that theory and I go to our

Barry Barish (1:53:30.320)

world here, I can't uniquely go to it. And if I can't, it's not predictive. And that's

Barry Barish (1:53:37.280)

actually a killer. That's a killer. And string theory is, it seems like from my outsider's

Barry Barish (1:53:42.480)

perspective has lost favor over the years, perhaps because of this very idea. It's a

Barry Barish (1:53:46.920)

lack of predictive power. I mean, that science has to connect to something where you make

Barry Barish (1:53:52.440)

predictions as beautiful as it might be. So I don't think we're close. I think we need

Barry Barish (1:53:59.960)

some experimental clues. It may be that information on something we don't understand presently

Barry Barish (1:54:07.520)

at all, like dark energy or probably not dark matter, but dark energy or something might

Barry Barish (1:54:12.680)

give us some ideas. But I can't envision right now in the short term, meaning the horizon

Barry Barish (1:54:26.160)

that we can see how we're going to bring these two theories together.

Barry Barish (1:54:31.760)

A kind of a two part question, maybe just asking the same thing in two different ways.

Barry Barish (1:54:38.560)

One question is, do you have hope that humans will colonize the galaxy? So expand out, become

Barry Barish (1:54:47.760)

a multi planetary species. Another way of asking that from a gravitational and a propulsion

Barry Barish (1:54:53.080)

perspective, do you think we'll come up with ways to travel closer to the speed of light

Barry Barish (1:54:57.160)

or maybe faster than the speed of light, which would make it a whole heck of a lot easier

Lex Fridman (1:55:02.280)

to expand out into the universe?

Barry Barish (1:55:06.120)

Yeah. Well, I think that's very futuristic. I think we're not that far from being able

Barry Barish (1:55:17.800)

to make a one way trip to Mars. That's then a question of whether people are willing to

Lex Fridman (1:55:29.720)

send somebody on a one way trip.

Barry Barish (1:55:31.640)

Oh, I think they are. There's a lot of the explorers burned bright within our hearts.

Lex Fridman (1:55:36.840)

Yeah, exactly.

Barry Barish (1:55:37.840)

There's a lot of people willing to die for the opportunity to explore new territory.

Lex Fridman (1:55:42.920)

So this recent landing on Mars is pretty impressive. They have a little helicopter. They're going

Barry Barish (1:55:51.280)

to fly around. You can imagine in the not too distant future that you could have, I

Barry Barish (1:55:57.920)

don't think civilizations colonizing, I can envision, but I can envision something more

Barry Barish (1:56:04.520)

like the South Pole. We haven't colonized Antarctica because it's all ice and cold and

Lex Fridman (1:56:12.000)

so forth. But we have stations. So we have a station that's self sustaining at the South

Barry Barish (1:56:19.000)

Pole. I've been there. It has.

Lex Fridman (1:56:22.000)

Wow, really?

Barry Barish (1:56:23.000)

Yeah.

Lex Fridman (1:56:24.000)

What's that like? Because there's parallels there to go to Mars.

Barry Barish (1:56:30.080)

It's fantastic.

Lex Fridman (1:56:31.080)

What's the journey like?

Barry Barish (1:56:33.480)

The journey involves going. The South Pole station is run in the US by the National Science

Barry Barish (1:56:41.640)

Foundation. I went because I was on the National Science Board that runs the National Science

Barry Barish (1:56:48.160)

Foundation. And so you get a VIP trip if you're healthy enough to the South Pole to see it,

Barry Barish (1:56:56.120)

which I took. You fly from the US to Australia to Christchurch in Southern Australia. And

Barry Barish (1:57:08.840)

from there you fly to McMurdo Station, which is on the coast. And it's the station with

Barry Barish (1:57:13.840)

about a thousand people right on the coast of Antarctica. It's about a seven or eight

Barry Barish (1:57:20.600)

hour flight and they can't predict the weather. So when I flew from Christchurch to McMurdo

Barry Barish (1:57:28.040)

Station, they tell you in advance, you do it in a military aircraft, they tell you in

Barry Barish (1:57:32.980)

advance that they can't predict whether they can land because they have to land on ice.

Lex Fridman (1:57:37.840)

And reassuring.

Barry Barish (1:57:38.840)

Yeah. And so about halfway the pilot got on and said, sorry, this is a, they call it a

Barry Barish (1:57:46.760)

boomerang flight. You know, boomerang goes out and goes back. So we had to stay a little

Barry Barish (1:57:52.360)

while in Christchurch, but then we eventually went to McMurdo Station and then flew to the

Barry Barish (1:57:59.560)

South Pole. The South Pole itself is, when I was there, it was minus 51 degrees. That

Barry Barish (1:58:07.920)

was summer. Zero humidity. And it's about 11,000 feet altitude because it's never warm

Barry Barish (1:58:26.840)

enough for anything to melt. So it doesn't snow very much, but it's about 11,000 feet

Barry Barish (1:58:32.040)

of snowpack. So you land in a place that's high altitude, cold as could be, and incredibly

Barry Barish (1:58:41.480)

dry, which means you have a physical adjustment. The place itself is fantastic. They have this

Lex Fridman (1:58:52.360)

great station there. They do astronomy at the South Pole. Nature wise, is it beautiful?

Barry Barish (1:59:00.320)

What's the experience like? Or is it like visiting any town? No, it's very small. There's

Barry Barish (1:59:05.160)

only less than a hundred people there. Even when I was there, there were about 50 or 60

Barry Barish (1:59:13.120)

there. And in the winter, there's less, half of that. Their winter. Yeah. It gets real

Barry Barish (1:59:18.800)

cold. It gets really cold, yeah. But it's a station. And I think, and that's, I mean,

Barry Barish (1:59:28.640)

we haven't gone beyond that. On the coast of Antarctica, they have greenhouses and they're

Barry Barish (1:59:33.920)

self sustaining in McMurdo Station, but we haven't really settled more than that kind

Barry Barish (1:59:40.840)

of thing in Antarctica, which is a big country or a big plot, a big piece of land. So I don't,

Barry Barish (1:59:55.440)

I can't envision kind of colonizing at people living so much, as much as I can see the equivalent

Barry Barish (20:04.720)

There's people that engineer viruses to protect us from viruses to see how close is this to

Barry Barish (20:15.760)

mutating so it can jump to humans or engineering defenses against those. And it seems exciting and

Barry Barish (20:25.520)

the application, the positive applications are really exciting at this time, but we don't think

Barry Barish (20:30.320)

about how that runs away in decades to come. Yeah. And I think it's the same idea as this

Barry Barish (20:36.720)

little book, The Ratchet of Science, The Ratchet of Curiosity. I mean, whether you pursue,

Barry Barish (20:46.240)

take curiosity and let artificial intelligence or machine learning run away with having its

Barry Barish (20:53.280)

solutions to whatever you want, or we do it, it's, I think, a similar consequence.

Barry Barish (20:59.120)

I think from what I've read about Enrico Fermi, he became a little bit cynical about the human

Lex Fridman (21:07.040)

species towards the end of his life, both having observed what he observed.

Barry Barish (21:12.560)

Well, he didn't write much. I mean, he died young. He died soon after the World War. There was

Barry Barish (21:20.160)

already, you know, the work by Teller to develop the hydrogen bomb. And I think he was a little

Barry Barish (21:26.880)

cynical of that, you know, pushing it even further and rising tensions between the Soviet Union and

Barry Barish (21:32.960)

the U.S. and looked like an endless thing. So, but he didn't say very much, but a little bit,

Barry Barish (21:38.320)

as you said. Yeah, there's a few clips to sort of maybe picked on a bad mood, but in a sense that

Barry Barish (21:45.520)

almost like a sadness, a melancholy sadness to a hope that waned a little bit about that perhaps we

Barry Barish (21:55.440)

can do, like this curious species can find the way out. Well, especially, I think, people who

Barry Barish (22:02.640)

worked like he did at Los Alamos and spent years of their life somehow had to convince themselves

Barry Barish (22:08.800)

that dropping these bombs would bring lasting peace and that it didn't. Yeah. As a small,

Barry Barish (22:18.240)

interesting aside, it'd be interesting to hear if you have opinions on this. His name is also

Barry Barish (22:23.600)

attached to the Fermi Paradox, which asks if there is a, you know, it's a very interesting question,

Barry Barish (22:30.960)

which is if it does seem if you sort of reason basically that there should be a lot of alien

Barry Barish (22:37.520)

civilizations out there. If the human species, if Earth is not that unique by basic, no matter the

Barry Barish (22:46.080)

values you pick, it's likely that there's a lot of alien civilizations out there. And if that's the

Barry Barish (22:52.400)

case, why have they not at least obviously visited us or sent us loud signals that everybody can

Barry Barish (22:59.840)

hear? Fermi's quoted as saying, sitting down at lunch, I think it was with Teller and Herb York,

Barry Barish (23:09.200)

who was kind of one of the fathers of the atomic bomb. And he sat down and he said something like,

Barry Barish (23:15.520)

where are they? Which meant, where are these other? And then he did some numerology where he

Barry Barish (23:25.280)

calculated, you know, how many, what they knew about how many galaxies there are and how many

Barry Barish (23:31.680)

stars and how many planets then are like the Earth and blah, blah, blah. That's been done much

Barry Barish (23:37.120)

better by somebody named Drake. And so, people usually refer to the, I don't know whether it's

Barry Barish (23:42.240)

called the Drake formula or something, but it has the same conclusion. The conclusion is it would

Barry Barish (23:47.440)

be a miracle if there weren't other, you know, the statistics are so high that how can we be

Barry Barish (23:53.760)

singular and separate? So, probably there is, but there's almost certainly life somewhere. Maybe

Barry Barish (24:04.160)

there was even life on Mars a while back, but intelligent life, probably. So, you know, the

Barry Barish (24:13.840)

statistics say that communicating with us, I think that it's harder than people think. We might not

Barry Barish (24:25.440)

know the right way to expect the communication, but all the communication that we know about

Barry Barish (24:34.160)

travels at the speed of light. And we don't think anything can go faster than the speed of light.

Barry Barish (24:41.040)

That limits the problem quite a bit. And it makes it difficult to have any back and forth

Barry Barish (24:48.560)

communication. You could send signals like we try to or look for, but to have any communication,

Barry Barish (24:54.640)

it's pretty hard when it has to be close enough that the speed of light would mean we could

Barry Barish (25:00.880)

communicate with each other. And I think, and we didn't even understand that. I mean, we're

Barry Barish (25:06.400)

an advanced civilization, but we didn't even understand that a little more than a hundred

Barry Barish (25:11.520)

years ago. So, are we just not advanced enough? Maybe to know something about that's the speed

Barry Barish (25:22.160)

of light. Maybe there's some other way to communicate that isn't based on electromagnetism.

Barry Barish (25:26.880)

I don't know. Gravity seems to be also have the same speed. That was a principle that Einstein

Barry Barish (25:33.760)

had and something we've measured actually. So is it possible? I mean, so we'll talk about

Barry Barish (25:39.520)

gravitational waves and in some sense, there's a brainstorming going on, which is like,

Lex Fridman (25:48.400)

how do we detect the signal? Like what would a signal look like and how would we detect it? And

Barry Barish (25:52.880)

that's true for gravitational waves. That's true for basically any physics phenomena. You have to

Barry Barish (25:57.840)

predict that that signal should exist. You have to have some kind of theory and model why that signal

Barry Barish (26:02.080)

should exist. I mean, is it possible that aliens are communicating with us via gravity? Like why

Barry Barish (26:09.200)

not? Well, yeah, it's true. Why not? For us, it's very hard to detect these gravitational effects.

Barry Barish (26:18.960)

They have to come from something pretty that has a lot of gravity like black holes, but we're

Barry Barish (26:24.880)

pretty primitive at this stage. There's very reputable physicists that look for a fifth force,

Barry Barish (26:36.560)

one that we haven't found yet. Maybe it's the key. What would a fifth force of physics look

Barry Barish (26:44.320)

like exactly? Well, usually they think it's probably a longer range force than we have now.

Lex Fridman (26:50.080)

But there are reputable colleagues of mine that spend their life looking for a fifth force.

Lex Fridman (26:56.480)

So longer range than gravity? Yeah. Super long? It doesn't fall off like one over r squared,

Lex Fridman (27:02.240)

but maybe separately. Gravity, Newton taught us, goes like inversely one over the square of the

Barry Barish (27:10.480)

distance apart you are. So it falls pretty fast. That's okay. So now we have a theory of what

Barry Barish (27:14.400)

consciousness is. It's just the fifth force of physics. Yeah. There we go. That's a good hypothesis.

Barry Barish (27:24.640)

Speaking of gravity, what are gravitational waves? Let's maybe start from the basics.

Barry Barish (27:32.720)

We learned gravity from Newton, right? When you were young, you were told that if you jumped up,

Barry Barish (27:39.920)

the earth pulls you down. And when the apple falls out of the tree, the earth pulls it down.

Lex Fridman (27:47.920)

And maybe you even asked your teacher why, but most of us accepted that. That was Newton's

Barry Barish (27:55.440)

picture, the apple falling out of the tree. But Newton's theory never told you why the apple

Barry Barish (28:00.400)

was attracted to the earth. That was a missing in Newton's theory. Newton's theory also

Barry Barish (28:07.920)

Newton recognized at least one of the two problems. I'll tell you one of them is there's more than

Barry Barish (28:12.720)

those, but one is why does the earth, what's the mechanism by which the earth pulls the apple or

Barry Barish (28:20.080)

holds the moon when it goes around, whatever it is. That's not explained by Newton, even though he

Barry Barish (28:25.920)

has the most successful theory of physics ever went 200 and some years with nobody ever seeing

Barry Barish (28:31.040)

a violation. But he accurately describes the movement of an object falling down to earth,

Lex Fridman (28:38.960)

but he's not answering why that what's yeah, because it's a distance. He gives a formula,

Barry Barish (28:45.120)

which it's a product of the earth's mass, the apple's mass inversely proportional to the square

Barry Barish (28:51.760)

of the distance between and then the strength he called capital G, the strength he couldn't

Barry Barish (28:57.280)

determine, but it was determined 100 years later. But no one ever saw a violation of this until a

Barry Barish (29:03.840)

possible violation, which Einstein fixed, which was very small that has to do with

Barry Barish (29:08.800)

mercury going around the sun, the orbit being slightly wrong if you calculate it by Newton's

Barry Barish (29:16.400)

theory. But so like most theories then in physics, you can have a wonderful one like Newton's theory.

Barry Barish (29:25.280)

It isn't wrong. But you have to have an improvement on it to answer things that it can't answer. And

Barry Barish (29:34.000)

in this case, Einstein's theory is the next step. We don't know if it's anything like a final theory

Barry Barish (29:41.040)

or even the only way to formulate it either. But he formulated this theory, which he released in 1915.

Barry Barish (29:51.440)

He took 10 years to develop it, even though in 1905, he solved three or four of the most important

Barry Barish (29:56.960)

problems in physics in a matter of months. And then he spent 10 years on this problem before he

Barry Barish (2:00:04.640)

of the South Pole Station. Well, in the computing world, there's an idea of backing up your

Barry Barish (2:00:10.400)

data and then you want to do offsite backup, to make sure that if the whole thing burns,

Barry Barish (2:00:16.520)

if your whole house burns down, that you can have a backup offsite of the data. I think

Barry Barish (2:00:21.520)

the difference between Antarctica and Mars is Mars is an offsite backup. That if we have

Barry Barish (2:00:28.260)

nuclear war, whatever the heck might happen here on earth, it'd be nice to have a backup

Barry Barish (2:00:32.800)

elsewhere. And it'd be nice to have a large enough colony where we sent a variety of people

Barry Barish (2:00:38.000)

except a few silly astronauts in suits, have an actual vibrant, get a few musicians and

Barry Barish (2:00:48.160)

artists up there, get a few, maybe like one or two computer scientists, those are essential.

Lex Fridman (2:00:53.920)

Maybe even a physicist, but I'm not sure.

Barry Barish (2:00:56.320)

Yeah, maybe not. So that comes back to something you talked about earlier, which is the paradox,

Barry Barish (2:01:02.200)

Fermi's paradox, because you talked about having to escape. And so one number you don't

Barry Barish (2:01:10.360)

know how to use in Fermi's calculation or Drake, who's done it better, is how long do

Barry Barish (2:01:15.760)

civilizations last? We've barely gotten to where we can communicate with electricity

Lex Fridman (2:01:24.320)

and magnetism and maybe we'll wipe ourselves out pretty soon.

Barry Barish (2:01:28.040)

Are you hopeful in general? Like you think we've got another couple of hundred years

Lex Fridman (2:01:32.480)

at least? Or are you worried?

Barry Barish (2:01:35.680)

Well, no, I'm hopeful, but I don't know if I'm hopeful in the longterm. If you say, are

Barry Barish (2:01:47.480)

we able to go for another couple of thousand years? I'm not sure. I think we have where

Barry Barish (2:01:55.720)

we started, the fact that we can do things that don't allow us to kind of keep going

Barry Barish (2:02:00.760)

or there can be, whether it ends up being a virus that we create or ends up being the

Barry Barish (2:02:06.560)

equivalent of nuclear war or something else. It's not clear that we can control things

Barry Barish (2:02:11.480)

well enough.

Lex Fridman (2:02:13.120)

So speaking of really cold conditions and not being hopeful and eventual suffering and

Barry Barish (2:02:20.520)

destruction of the human species, let me ask you about Russian literature. You mentioned,

Barry Barish (2:02:26.120)

how's that for transition? I'm doing my best here. You mentioned that you used to love

Barry Barish (2:02:30.960)

literature when you were younger and you even were hoping to be a writer yourself. That

Barry Barish (2:02:36.760)

was the motivation. And some of the books I've seen that you listed that were inspiring

Barry Barish (2:02:43.760)

to you was from Russian literature, like Tolstoy, Dostoevsky, Solzhenitsyn. Maybe in general

Barry Barish (2:02:52.960)

you can speak to your fascination with Russian literature or in general what you picked up

Barry Barish (2:02:57.840)

from those.

Barry Barish (2:02:58.840)

I'm not surprised you picked up on the Russian literature, your background, but that's okay.

Barry Barish (2:03:08.320)

You should be surprised I didn't make the entire conversation about this. That's the

Lex Fridman (2:03:12.040)

real surprise.

Barry Barish (2:03:13.040)

Yeah. When I didn't really become a physicist or want to go in science until I started college.

Lex Fridman (2:03:24.280)

So when I was younger, I was good at math and that kind of stuff, but I didn't really,

Barry Barish (2:03:29.680)

I came from a family, nobody went to college and I didn't have any mentors. But I liked

Barry Barish (2:03:36.400)

to read when I was really young. And so when I was very young, I always carried around

Barry Barish (2:03:42.440)

a pocket book and read it. And my mother read these mystery stories and I got bored by those

Barry Barish (2:03:49.280)

eventually. And then I discovered real literature. I don't know what age, but about 12 or 13.

Lex Fridman (2:03:55.500)

And so then I started reading good literature and there's nothing better than Russian literature,

Lex Fridman (2:04:00.640)

of course.

Barry Barish (2:04:01.640)

Thank you.

Barry Barish (2:04:02.640)

Reading good literature. So I read quite a bit of Russian literature at that time. And

Lex Fridman (2:04:16.240)

so you asked me about, well, I don't know, I'll say a few words, Dostoevsky. So what

Barry Barish (2:04:22.840)

about Dostoevsky? For me, Dostoevsky was important in two, I mean, I've read a lot of literature

Barry Barish (2:04:33.200)

because it's kind of the other thing I do with my life. And he made two incredible,

Barry Barish (2:04:39.160)

in addition to his own literature, he influenced literature tremendously by having, I don't

Barry Barish (2:04:46.960)

know how to pronounce polyphony. So he's the first real serious author that had multiple

Barry Barish (2:04:53.720)

narrators. And he absolutely is the first. And he also was the first, he began existential

Barry Barish (2:05:05.440)

literature. So the most important book that I've read in the last year when I've been

Barry Barish (2:05:12.440)

forced to be isolated was existential literature. I decided to reread Camus, The Plague.

Barry Barish (2:05:20.960)

Oh, yeah. That's a great book.

Lex Fridman (2:05:23.880)

It's a great book and it's right now to read it. It's fantastic.

Barry Barish (2:05:26.400)

I think that book is about love, actually. Love for humanity.

Barry Barish (2:05:30.960)

It is, but it has all the, if you haven't read it in recent years, I had read it before,

Barry Barish (2:05:37.080)

of course, but to read it during this, because it's about a plague. So it's really fantastic

Barry Barish (2:05:43.080)

to read down. But that reminds me of, he was a great existentialist, but the beginning

Barry Barish (2:05:48.000)

of existential literature was Dostoevsky.

Lex Fridman (2:05:50.800)

Dostoevsky, yeah.

Lex Fridman (2:05:51.940)

So in addition to his own great novels, he had a tremendous impact on literature.

Lex Fridman (2:06:00.280)

And there's also for Dostoevsky, unlike most other existentialists, he was at least in

Barry Barish (2:06:06.300)

part religious. I mean, religiosity permeated his idea. I mean, one of my favorite books

Lex Fridman (2:06:12.360)

of his is The Idiot, which is a Christlike figure in there.

Lex Fridman (2:06:16.720)

Well, there's Prince Mishkin, is that his name?

Lex Fridman (2:06:19.280)

Prince Mishkin, yeah.

Barry Barish (2:06:20.280)

Yeah, Mishkin.

Lex Fridman (2:06:21.280)

Yeah, Mishkin.

Barry Barish (2:06:22.280)

Yeah.

Lex Fridman (2:06:23.280)

That's one thing about, you read it in English, I presume.

Barry Barish (2:06:25.960)

Yeah, yeah.

Barry Barish (2:06:26.960)

Yeah. So the names, that's what gets a lot of people. There's so many names, so hard

Barry Barish (2:06:30.500)

to pronounce. You have to remember all of them. It's like you have the same problem.

Lex Fridman (2:06:35.700)

But he was a great character.

Barry Barish (2:06:38.320)

I kind of have a connection with him, because I often, the title of the book, The Idiot,

Barry Barish (2:06:47.240)

is I kind of, I often call myself an idiot, because that's how I feel. I feel so naive

Barry Barish (2:06:52.620)

about this world. And I'm not sure, I'm not sure why that is. Maybe it's genetic or so

Lex Fridman (2:06:59.600)

on. But I have a connection, a spiritual connection to that character.

Barry Barish (2:07:05.160)

To Mishkin.

Lex Fridman (2:07:06.160)

To Mishkin, yeah.

Lex Fridman (2:07:07.160)

But he was far from an idiot.

Barry Barish (2:07:10.160)

No, in some sense, in some sense. But in another sense, maybe not of this world.

Barry Barish (2:07:17.400)

In another sense he was. I mean, he was a bumbler, a bunker.

Lex Fridman (2:07:23.020)

But you also mentioned Solzhenitsyn, very interesting.

Lex Fridman (2:07:28.160)

And he always confused me. Of course, he was really, really important in writing about

Barry Barish (2:07:36.800)

Stalin, and first getting in trouble, and then later he wrote about Stalin in a way,

Barry Barish (2:07:48.480)

I forget what the book was, in a way that was very critical of Lenin.

Barry Barish (2:07:55.640)

Yeah, he's evolved through the years, and he actually showed support for Putin eventually.

Barry Barish (2:08:00.640)

It was a very interesting transition he took, no, journey he took through thinking about

Barry Barish (2:08:08.480)

Russia and the Soviet Union. But I think what I get from him is basic, it's like Viktor

Barry Barish (2:08:17.920)

has this man's search for meaning. I have a similar kind of sense of the cruelty of

Barry Barish (2:08:25.640)

human nature, cruelty of indifference, but also the ability to find happiness in the

Barry Barish (2:08:31.520)

small joys of life. That's something, there's nothing like a prison camp that makes you

Lex Fridman (2:08:37.720)

realize you could still be happy with a very, very little.

Barry Barish (2:08:41.760)

Yeah, his description of how to go through a day and actually enjoy it in a prison camp

Lex Fridman (2:08:50.160)

is pretty amazing. And some prison camp, it's the worst of the worst.

Lex Fridman (2:08:56.760)

And also, I do think about the role of authoritarian states in hopeful idealistic systems somehow

Barry Barish (2:09:09.440)

leading to the suffering of millions. And this might be arguable, but I think a lot

Barry Barish (2:09:16.760)

of people believe that Stalin, I think, genuinely believed that he's doing good for the world.

Lex Fridman (2:09:24.240)

And he wasn't. It's a very valuable lesson that even evil people think they're doing

Barry Barish (2:09:32.280)

good. Otherwise, it's too difficult to do the evil. The best way to do evil is to believe

Barry Barish (2:09:38.360)

about framing it in a way like you're doing good. And then this is a very clear picture

Barry Barish (2:09:44.000)

of that, which is the gulags. And Solzhenitsyn is one of the best people to reveal that.

Barry Barish (2:09:53.400)

The most recent thing I read, it isn't actually fiction, was the woman, I can't remember

Barry Barish (2:09:58.880)

her name, who got the Nobel Prize about within the last five years. I don't know whether

Lex Fridman (2:10:04.280)

she's Ukrainian or Russian, but there are interviews. Have you read that?

Barry Barish (2:10:09.840)

Interview of Ukrainian survivors of...

Barry Barish (2:10:12.680)

Well, I think she may be originally Ukrainian. The book's written in Russian and translated

Barry Barish (2:10:18.560)

in English, and many of the interviews are in Moscow and places. But she won the Nobel

Barry Barish (2:10:23.920)

Prize within the last five years or so. But what's interesting is that these are people

Barry Barish (2:10:31.080)

of all different ages, all different occupations and so forth, and they're reflecting on their

Barry Barish (2:10:39.040)

reaction to basically the present Soviet system, the system they lived with before.

Barry Barish (2:10:45.560)

There's a lot of looking back by a lot of them with, well, it being much better before.

Barry Barish (2:10:57.400)

Yeah. I don't know what... In America, we think we know the right answer, what it means

Barry Barish (2:11:05.680)

to be, to build a better world. I'm not so sure. I think we're all just trying to figure

Lex Fridman (2:11:11.440)

it out.

Barry Barish (2:11:12.440)

Yeah, there's...

Lex Fridman (2:11:13.440)

We're doing our best.

Barry Barish (2:11:14.440)

I think you're right.

Barry Barish (2:11:17.600)

Is there advice you can give to young people today, besides reading Russian literature

Barry Barish (2:11:23.760)

at a young age, about how to find their way in life, how to find success in Korea or just

Lex Fridman (2:11:29.920)

life in general?

Barry Barish (2:11:37.080)

My own belief, it may not be very deep, but I believe it. I think you should follow your

Barry Barish (2:11:43.080)

dreams and you should have dreams and follow your dreams if you can, to the extent that

Barry Barish (2:11:48.600)

you can. And we spend a lot of our time doing something with ourselves. In my case, physics,

Barry Barish (2:11:55.800)

in your case, I don't know, whatever it is, machine learning and this. Yeah, you should

Barry Barish (2:12:04.720)

have fun.

Lex Fridman (2:12:05.720)

What was... Wait, wait, wait. Follow your dreams. What dream did you have? Because there's...

Barry Barish (2:12:12.120)

Well, originally, I was...

Barry Barish (2:12:14.720)

Because you didn't follow your dream. I thought you were supposed to be a writer.

Barry Barish (2:12:16.720)

I changed along the way. I was gonna be, but I changed.

Lex Fridman (2:12:20.400)

What happened?

Barry Barish (2:12:21.400)

That was... What happened? Oh, I read... I decided to take the most serious literature

Barry Barish (2:12:28.460)

course in my high school, which was a mistake. I'd probably be a second rate writer now.

Barry Barish (2:12:34.800)

And...

Lex Fridman (2:12:35.800)

Could be a Nobel Prize winning writer.

Lex Fridman (2:12:37.520)

And the book that we read, even though I had read Russian novels, I was 15, I think, cured

Lex Fridman (2:12:50.080)

me from being a novelist.

Lex Fridman (2:12:53.080)

Destroyed your dream?

Lex Fridman (2:12:54.080)

Yes.

Lex Fridman (2:12:55.080)

Cured you. Okay. What was the book?

Lex Fridman (2:12:56.800)

Moby Dick.

Barry Barish (2:12:57.800)

Okay.

Lex Fridman (2:12:58.800)

So, why Moby Dick?

Lex Fridman (2:13:00.360)

Yeah, why?

Barry Barish (2:13:01.360)

So, I've read it since, and it's a great novel. Maybe it's as good as the Russian novels.

Barry Barish (2:13:07.680)

I've never made it through. It was too boring. It was too long.

Lex Fridman (2:13:11.280)

Okay. Your words are gonna mesh with what I say.

Barry Barish (2:13:14.400)

Excellent.

Lex Fridman (2:13:15.400)

And you may have the same problem at older ages.

Barry Barish (2:13:17.880)

That's why I'm not a writer.

Barry Barish (2:13:19.520)

It may be. So, the problem is, Moby Dick is... What I remember was there was a chapter that

Barry Barish (2:13:27.120)

was maybe 100 pages long, all describing this, why there was Ahab and the white whale, and

Lex Fridman (2:13:34.080)

it was the battle between Ahab with his wooden peg leg and the white whale.

Lex Fridman (2:13:39.520)

And there was a chapter that was 100 pages long in my memory, I don't know how long it

Barry Barish (2:13:43.460)

really was, that described in detail, though, great white whale and what he was doing and

Lex Fridman (2:13:49.960)

what his fins were like and this and that.

Lex Fridman (2:13:52.360)

And it was so incredibly boring, the word you used, that I thought, if this is great

Barry Barish (2:13:58.280)

literature, screw it.

Lex Fridman (2:14:00.280)

Fascinating.

Barry Barish (2:14:01.280)

Okay. And now, why did I have a problem? I know now in reflection, because I still read

Barry Barish (2:14:06.800)

a lot, and I read that novel after I was 30 or 40 years old, and the problem was simple.

Barry Barish (2:14:18.600)

I diagnosed what the problem was. That novel, in contrast to the Russian novels, which are

Lex Fridman (2:14:25.600)

very realistic and point of view, is one huge metaphor.

Barry Barish (2:14:32.960)

At 15 years old, I probably didn't know the word, and I certainly didn't know the meaning

Lex Fridman (2:14:37.200)

of metaphor.

Lex Fridman (2:14:38.200)

Yeah, like, why do I care about a fish? Why are you telling me all about this fish?

Barry Barish (2:14:42.160)

Exactly. It's one big metaphor. So, reading it later as a metaphor, I could really enjoy

Barry Barish (2:14:47.600)

it. But the teacher gave me the wrong book, or maybe it was the right book because I went

Barry Barish (2:14:51.480)

into physics. But it was truly, I think, I may oversimplify, but it was really that I

Barry Barish (2:14:59.320)

was too young to read that book. Not too young to read the Russian novels, interestingly,

Lex Fridman (2:15:04.360)

but too young to read that because I probably didn't even know the word, and I certainly

Barry Barish (2:15:08.840)

didn't understand it as a metaphor.

Barry Barish (2:15:10.800)

Well, in terms of fish, I recommend people read Old Man and the Sea, much shorter, much

Barry Barish (2:15:15.400)

better. It's still a metaphor, though. But you can read it just as a story about a guy

Barry Barish (2:15:21.920)

catching a fish, and it's still fun to read. I had the same experience as you, not with

Barry Barish (2:15:29.560)

Moby Dick, but later in college, I took a course on James Joyce. Don't ask me why. I

Barry Barish (2:15:34.640)

was majoring in computer science, I took a course on James Joyce. And I was kept being

Barry Barish (2:15:38.980)

told that he is widely considered, by many considered, to be the greatest literary writer

Barry Barish (2:15:46.640)

of the 20th century. And I kept reading, I think, so his short story is The Dead, I think

Barry Barish (2:15:52.520)

it's called. It was very good. Well, not very good, but pretty good. And then Ulysses.

Lex Fridman (2:15:57.360)

It's actually very good.

Barry Barish (2:15:58.360)

It is very good. Only The Dead, the final story, it still rings with me today. But then

Barry Barish (2:16:02.640)

Ulysses was, I got through Ulysses with the help of some Cliff Notes and so on. And so

Barry Barish (2:16:09.400)

I did Ulysses and then Finnegan's Wake. The moment I started Finnegan's Wake, I said,

Barry Barish (2:16:14.760)

this is stupid. That's when I went full into like, I don't know, that's when I went full

Barry Barish (2:16:22.440)

Kafka, Bukowski, like people who just talk about the darkness of the human condition

Barry Barish (2:16:28.480)

in the fewest words possible and without any of the music of language. So it was a turning

Barry Barish (2:16:36.520)

point as well. I wonder when is the right time to appreciate the beauty of language.

Barry Barish (2:16:45.200)

Like even Shakespeare. I was very much off put by Shakespeare in high school and only

Barry Barish (2:16:49.040)

later I started to appreciate its value in the same way. Let me ask you a ridiculous

Barry Barish (2:16:55.440)

question. Okay. I mean, because you've read Russian literature, let me ask this one last

Barry Barish (2:17:04.640)

question. I might be lying. There might be a couple more, but what do you think is the

Barry Barish (2:17:10.560)

meaning of this whole thing? You got a Nobel prize for looking out into the, trying to

Barry Barish (2:17:17.980)

reach back into the beginning of the universe, listening to the gravitational waves, but

Barry Barish (2:17:24.800)

that still doesn't answer the why. Why are we here? Beyond just the matter and anti matter,

Barry Barish (2:17:33.840)

the philosophical question.

Barry Barish (2:17:35.360)

The philosophical question about the meaning of life, I'm probably not really good at.

Barry Barish (2:17:42.960)

I think that the individual meaning, I would say it rather simplistically is whether you've

Barry Barish (2:17:56.600)

made a difference, a positive difference, I'd say for anything besides yourself. Meaning

Barry Barish (2:18:05.160)

you could have been important to other people or you could have discovered gravitational

Barry Barish (2:18:11.340)

waves that matters to other people or something, but something beyond just existing on the

Barry Barish (2:18:16.300)

earth as an individual. So your life has meaning if you have affected either knowledge or people

Barry Barish (2:18:27.440)

or something beyond yourself. It's a simplistic statement, but it's about as good as I can

Barry Barish (2:18:35.960)

say. In all of its simplicity, it may be very true. Does it make you sad that this ride

Lex Fridman (2:18:46.480)

ends? Do you think about your mortality? Are you afraid of it?

Barry Barish (2:18:55.360)

Not exactly afraid of it, but saddened by it. I'm old enough to know that I've lived

Barry Barish (2:19:06.520)

most of my life and I enjoy being alive. I can imagine being sick and not wanting to

Barry Barish (2:19:14.960)

be alive, but I'm not.

Lex Fridman (2:19:17.560)

It's been a good ride.

Barry Barish (2:19:23.040)

I'm not happy to see it come to an end. I'd like to see it prolong, but I don't fear the

Barry Barish (2:19:35.720)

dying itself or that kind of thing. It's more, I'd like to prolong what is I think a good

Barry Barish (2:19:44.320)

life that I'm living and still living.

Barry Barish (2:19:51.240)

It's sad to think that the finiteness of it is the thing that makes it special. And also

Barry Barish (2:20:01.600)

sad to me, at least it's kind of, I don't think I'm using too strong of a word, but

Barry Barish (2:20:08.520)

it's kind of terrifying the uncertainty of it. The mystery of it, the mystery of death.

Barry Barish (2:20:15.960)

The mystery of it, yeah, of death. When we're talking about the mystery of black holes that's

Lex Fridman (2:20:20.120)

somehow distant, that's somehow out there and the mystery of our own.

Lex Fridman (2:20:25.120)

But even life, the mystery of consciousness, I find so hard to deal with too. I mean, it's

Barry Barish (2:20:31.400)

not as painful. I mean, we're conscious, but the whole magic of life we can understand,

Lex Fridman (2:20:37.640)

but consciousness where we can actually think and so forth. It's pretty.

Barry Barish (2:20:43.560)

It seems like such a beautiful gift that it really sucks that we get to let go of it.

Barry Barish (2:20:48.520)

We have to let go of it. What do you hope your legacy is? As I'm sure they will. Aliens

Barry Barish (2:20:54.080)

when they visit and humans have destroyed all of human civilization. Aliens read about

Lex Fridman (2:20:59.320)

you in an encyclopedia that we'll leave behind. What do you hope it says?

Barry Barish (2:21:03.520)

Well, I would hope they, to the extent that they evaluated me, felt that I helped move

Barry Barish (2:21:12.280)

science forward as a tangible contribution and that I served as a good role model for

Lex Fridman (2:21:22.520)

how humans should live their lives.

Lex Fridman (2:21:25.680)

And we're part of creating one of the most incredible things humans have ever created.

Lex Fridman (2:21:31.840)

So yes, there's the science. That's the Fermi thing, right?

Lex Fridman (2:21:36.920)

And the instrument, I guess.

Lex Fridman (2:21:38.240)

And the instrument. The instrument is a magical creation, not just by a human, by a collection

Barry Barish (2:21:43.960)

of humans. The collaboration is, that's humanity at its best. I do hope we last quite a bit

Barry Barish (2:21:58.720)

longer, but if we don't, this is a good thing to remember humans by. At least they built

Barry Barish (2:22:05.560)

that thing. That's pretty impressive. Barry, this is an amazing conversation. Thank you

Lex Fridman (2:22:10.320)

so much for wasting your time and explaining so many things so well. I appreciate your

Barry Barish (2:22:14.840)

time today.

Lex Fridman (2:22:15.840)

Thank you.

Barry Barish (2:22:17.960)

Thanks for listening to this conversation with Barry Barish. To support this podcast,

Barry Barish (2:22:22.760)

please check out our sponsors in the description. And now let me leave you with some words from

Barry Barish (2:22:28.280)

Werner Heisenberg, a theoretical physicist and one of the key pioneers of quantum mechanics.

Barry Barish (2:22:35.840)

Not only is the universe stranger than we think, it is stranger than we can think. Thank

Barry Barish (2:22:43.500)

you for listening and hope to see you next time.

Barry Barish (30:02.480)

let it out. And this is called general relativity. It's a new theory of gravity.

Barry Barish (30:07.120)

1915. In 1916, Einstein wrote a little paper where he did not do some fancy derivation.

Barry Barish (30:18.720)

Instead, he did what I would call he used his intuition, which he was very good at too. And that

Barry Barish (30:30.000)

is he noticed that if he wrote the formulas for general relativity in a particular way,

Lex Fridman (30:37.200)

they looked a lot like the formulas for electricity and magnetism.

Barry Barish (30:40.800)

Being Einstein, he then took the leap that electricity and magnetism, we discovered only

Barry Barish (30:46.800)

20 years before that in the 1880s, have waves. Of course, that's light and electromagnetic waves,

Barry Barish (30:54.560)

radio waves, everything else. So he said, if the formulas look similar, then gravity probably has

Barry Barish (31:01.440)

waves too. That's such a big leap, by the way. I mean, maybe you could go back to the 1880s,

Barry Barish (31:10.400)

maybe you can correct me, but that just seems like a heck of a leap.

Barry Barish (31:15.120)

Yeah. And it was considered to be a heck of a leap. So first that paper was, except for this

Barry Barish (31:22.080)

intuition, was poorly written, had a serious mistake. It had a factor of two wrong in the

Barry Barish (31:30.320)

strength of gravity, which meant if we use those formulas, we would... And two years later,

Barry Barish (31:37.200)

he wrote a second paper. And in that paper, it turns out to be important for us because in that

Barry Barish (31:43.680)

paper, he not only fixed his factor of two mistake, which he never admitted, he just wrote it,

Barry Barish (31:50.480)

fixed it like he always did. And then he told us how you make gravitational waves, what makes

Barry Barish (31:58.640)

gravitational waves. And you might recall in electromagnetism, we make electromagnetic waves

Barry Barish (32:05.200)

in a simple way. You take a plus charge and minus charge, you oscillate like this, and that makes

Barry Barish (32:10.160)

the electromagnetic waves. And a physicist named Hertz made a receiver that could detect the waves

Lex Fridman (32:16.320)

and put it in the next room. He saw them and moved forward and backward and saw that it was wave like.

Lex Fridman (32:22.160)

So Einstein said, it won't be a dipole like that, it'll be a four pole thing. And that's what it's

Barry Barish (32:30.400)

called, it's called a quadrupole moment that gives the gravitational wave. So that again, by insight,

Barry Barish (32:36.880)

not by derivation. That set the table for what you needed to do to do it. At the same time,

Barry Barish (32:43.360)

in the same year, Schwarzschild, not Einstein, said there were things called black holes. So

Barry Barish (32:49.520)

it's interesting that that came the same. So what year was that? 1915. It was in parallel...

Barry Barish (32:56.640)

Well, I should probably know this, but did Einstein not have an intuition that there

Barry Barish (33:01.920)

should be such things as black holes? That came from Schwarzschild. Oh, interesting.

Barry Barish (33:07.200)

Yeah. So Schwarzschild, who was a German theoretical physicist, he got killed in the war,

Barry Barish (33:14.400)

I think, in the First World War, two years later or so. He's the one that proposed black holes,

Barry Barish (33:21.520)

that there were black holes. That feels like a natural conclusion of general relativity, no? Or

Barry Barish (33:27.120)

is that not? Well, it may seem like it, but I don't know about a natural conclusion. It's a result

Barry Barish (33:34.560)

of curved space time though. Right. But it's such a weird result that you might have to...

Barry Barish (33:40.560)

It's a special... Yeah, it's a special case. Yeah. So I don't know. Anyway, Einstein then,

Barry Barish (33:48.960)

an interesting part of the story is that Einstein then left the problem. Most physicists,

Barry Barish (33:54.000)

because it really wasn't derived, he just made this, didn't pick up on it or general relativity

Barry Barish (34:01.120)

much because quantum mechanics became the thing in physics. And Einstein only picked up this

Barry Barish (34:10.080)

problem again after he immigrated to the US. So he came to the US in 1932. And I think in 1934 or

Barry Barish (34:18.000)

1935, he was working with another physicist called Rosen, who he did several important works with,

Lex Fridman (34:24.400)

and they revisited the question. And they had a problem that most of us as students always had,

Barry Barish (34:32.880)

that study general relativity. General relativity is really hard because it's four dimensional

Barry Barish (34:37.680)

instead of three dimensional. And if you don't set it up right, you get infinities,

Barry Barish (34:42.800)

which don't belong there. We call them coordinate singularities as a name. But if you get these

Barry Barish (34:49.520)

infinities, you don't get the answers you want. And he was trying to derive now general relativity

Barry Barish (34:57.440)

from general relativity, gravitational waves. And in doing it, he kept getting these infinities.

Lex Fridman (35:04.240)

And so he wrote a paper with Rosen that he submitted to our most important journal,

Barry Barish (35:10.880)

Physical Review Letters. And that when it was submitted to Physical Review Letters,

Barry Barish (35:17.840)

it was entitled, Do Gravitational Waves Exist? A very funny title to write 20 years after he

Barry Barish (35:24.400)

proposed they exist. But it's because he had found these singularities, these infinities. And so

Barry Barish (35:32.240)

the editor at that time, and the part of it that I don't know, is peer review. We live and die by

Barry Barish (35:43.440)

peer review as scientists send our stuff out. We don't know when peer review actually started

Barry Barish (35:49.520)

or what peer review Einstein ever experienced before this time. But the editor of Physical

Barry Barish (35:55.520)

Review sent this out for review. He had a choice. He could take any article and just accept it.

Barry Barish (36:02.000)

He could reject it, or he could send it for review. I believe the editors used to have much

Barry Barish (36:07.760)

more power. Yeah, yeah. And he was a young man. His name was Tate. And he ended up being editor

Barry Barish (36:13.360)

for years. So he sent this for review to a theoretical physicist named Robertson, who was

Barry Barish (36:22.320)

also in this field of general relativity, who happened to be on sabbatical at that moment at

Barry Barish (36:27.840)

Caltech. Otherwise, his institution was Princeton, where Einstein was. And he saw that the way they

Barry Barish (36:37.280)

set up the problem, the infinities were like I make it as a student, because if you don't

Barry Barish (36:42.320)

set it up right in general relativity, you get these infinities. And so he reviewed the article

Lex Fridman (36:48.320)

and gave an illustration that if they set it up in what are called cylindrical coordinates, these

Barry Barish (36:54.640)

infinities went away. The editor of Physical Review was obviously intimidated by Einstein.

Barry Barish (37:03.280)

He wrote this really not a letter back like I would get saying, you're screwed up in your paper

Barry Barish (37:08.800)

instead. It was kind of, what do you think of the comments of our referee? Einstein wrote back,

Lex Fridman (37:17.840)

and it's a well documented letter, wrote back a letter to Physical Review saying, I didn't send

Barry Barish (37:24.640)

you the paper to send it to one of your so called experts. I sent it to you to publish. I withdraw

Barry Barish (37:31.600)

the paper. And he never published again in that journal. That was 1936. Instead, he rewrote it

Barry Barish (37:42.000)

with the fixes that were made, changed the title and published it in what was called the Franklin

Barry Barish (37:49.920)

Review, which is the Franklin Institute in Philadelphia, which is Benjamin Franklin

Barry Barish (37:56.960)

Institute, which doesn't have a journal now, but did at that time. So the article is published.

Barry Barish (38:01.920)

It's the last time he ever wrote about it. It remained controversial. So it wasn't until

Barry Barish (38:08.080)

close to 1960, 1958, where there was a conference that brought together the experts in general

Barry Barish (38:19.760)

relativity to try to sort out whether it was true that there were gravitational waves or not.

Lex Fridman (38:29.360)

And there was a very nice derivation by a British theorist from the heart of the theory that gets

Barry Barish (38:40.240)

gravitational waves. And that was number one. The second thing that happened at that meeting is

Barry Barish (38:46.160)

Richard Feynman was there. And Feynman said, well, if there's typical Feynman, if there's

Barry Barish (38:53.200)

gravitational waves, they need to be able to do something, otherwise they don't exist. So they

Barry Barish (38:58.320)

have to be able to transfer energy. So he made an idea of a gedankenexperiment that is just a bar

Barry Barish (39:05.920)

with a couple of rings on it. And then if a gravitational wave goes through, it distorts the

Barry Barish (39:11.120)

bar and that creates friction on these little rings and that's heat and that's energy. So that

Barry Barish (39:19.440)

meant... Is that a good idea? That sounds like a good idea. Yeah. It means that he showed that

Barry Barish (39:24.960)

that with the distortion of space time, you could transfer energy just by this little idea.

Lex Fridman (39:31.440)

And it was shown theoretically. So at that point, it was believed theoretically then

Barry Barish (39:39.360)

by people that gravitational waves should exist. No, we should be able to detect them.

Barry Barish (39:45.440)

We should be able to detect them, except that they're very, very small.

Lex Fridman (39:49.200)

And so what kind of, there's a bunch of questions here, but what kind of events

Barry Barish (39:55.280)

would generate gravitational waves? You have to have this, what I call quadrupole moment.

Barry Barish (40:01.200)

That comes about if I have, for example, two objects that go around each other like this,

Barry Barish (40:08.400)

like the earth around the sun or the moon around the earth, or in our case, it turns out to be two

Barry Barish (40:14.960)

black holes going around each other like this. So how's that different than basic oscillation

Barry Barish (40:19.680)

back and forth? Is it just more common in nature to have... Oscillation is a dipole moment. So it

Barry Barish (40:24.080)

has to be in three dimensional space kind of oscillation. So you have to have something

Barry Barish (40:27.600)

that's three dimensional that'll give what I called a quadrupole moment. That's just built

Barry Barish (40:32.160)

into this. And luckily in nature you have stuff... And luckily things exist. And it is luckily

Barry Barish (40:38.400)

because the effect is so small that you could say, look, I could take a barbell

Lex Fridman (40:43.120)

and spin it, right? And detect the gravitational waves. But unfortunately, no matter how much I

Barry Barish (40:50.640)

spin it, how fast I spin it, so I know how to make gravitational waves, but they're so weak,

Barry Barish (40:56.560)

I can't detect them. So we have to take something that's stronger than I can make. Otherwise we

Barry Barish (41:01.520)

would do what Hertz did for electromagnetic waves. Go in our lab, take a barbell, put it on

Barry Barish (41:07.040)

something, spin it. Can I ask a dumb question? So a single object that's weirdly shaped,

Barry Barish (41:13.120)

does that generate gravitational waves? So if it's rotating? Sure. But it's just a much weaker signal.

Barry Barish (41:20.480)

It's weaker. Well, we didn't know what the strongest signal would be that we would see.

Barry Barish (41:26.880)

We targeted seeing something called neutron stars actually, because black holes we don't

Barry Barish (41:31.040)

know very much about. It turned out we were a little bit lucky. There was a stronger source,

Lex Fridman (41:35.680)

which was the black holes. Well, another ridiculous question. So you say waves. What does a wave mean?

Barry Barish (41:43.680)

Like the most ridiculous version of that question is, what does it feel like to ride a wave as you

Barry Barish (41:52.320)

get closer to the source? Or experience it? Well, if you experience a wave, imagine that this is

Lex Fridman (42:00.320)

what happens to you. I don't know what you mean about getting close. It comes to you. So it's like

Barry Barish (42:06.320)

this light wave or something that comes through you. So when a light hits you, it makes your eyes

Barry Barish (42:12.400)

detect it. I flashed it. What does this do? It's like going to the amusement park, and they have

Barry Barish (42:20.560)

these mirrors. You look in this mirror and you look short and fat, and the one next to you makes

Barry Barish (42:25.040)

you tall and thin. Imagine that you went back and forth between those two mirrors once a second.

Barry Barish (42:32.560)

That would be a gravitational wave with a period of once a second. If you did it 60 times a second,

Barry Barish (42:38.480)

go back and forth. And then that's all that happens. It makes you taller and shorter and

Barry Barish (42:43.520)

fatter back and forth as it goes through you at the frequency of the gravitational wave. So the

Barry Barish (42:50.320)

frequencies that we detect are higher than one a second, but that's the idea. And the amount is

Lex Fridman (42:57.520)

small. Amount is small, but if you're closer to the source of the wave, is it the same amount?

Barry Barish (43:07.200)

Yeah, it doesn't dissipate. It doesn't dissipate. Okay, so it's not that fun of an amusement ride.

Barry Barish (43:14.880)

Well, it does dissipate, but it's proportional to the distance.

Lex Fridman (43:22.400)

Right. It's not a big power.

Barry Barish (43:24.720)

Right. Gotcha. But it would be a fun ride if you get a little bit closer or a lot closer.

Barry Barish (43:31.840)

I mean, I wonder what the... Okay, this is a ridiculous question, but I have you here.

Barry Barish (43:36.320)

I mean, the getting fatter and taller, I mean, that experience, for some reason,

Barry Barish (43:44.640)

that's mind blowing to me because it brings the distortion of space time to you. I mean,

Barry Barish (43:51.520)

space time is being morphed, right? Like this is a wave.

Lex Fridman (43:56.000)

That's right.

Barry Barish (43:57.200)

That's so weird.

Lex Fridman (43:59.760)

And we're in space, so we're affected by it.

Barry Barish (44:01.200)

Yeah, we're in space and now it's moving.

Lex Fridman (44:03.520)

It's moving. I don't know what to do with it. I mean, does it... Okay.

Lex Fridman (44:08.480)

How much do you think about the philosophical implications of

Barry Barish (44:13.440)

general relativity? Like that we're in space time and it can be bent by gravity.

Barry Barish (44:21.280)

Like, is that just what it is? Are we supposed to be okay with this? Because like Newton,

Lex Fridman (44:27.840)

even Newton is a little weird, right? But that at least like makes sense.

Barry Barish (44:31.120)

That's our physical world. When an apple falls, it makes sense. But the fact that

Lex Fridman (44:37.680)

entirety of the space time we're in can bend, that's really mind blowing.

Barry Barish (44:47.840)

Let me make another analogy.

Lex Fridman (44:49.360)

This is a therapy session for me at this point.

Barry Barish (44:50.880)

Yeah, right. Another analogy.

Lex Fridman (44:52.880)

Thank you.

Lex Fridman (44:53.520)

So imagine you have a trampoline.

Lex Fridman (44:56.000)

Yes.

Lex Fridman (44:56.240)

Okay. What happens if you put a marble on a trampoline? It doesn't do anything, right?

Lex Fridman (45:02.240)

No. Just a little bit, but not much.

Barry Barish (45:04.720)

Yeah. I mean, just if I drop it, it's not going to go anywhere.

Lex Fridman (45:08.320)

Now imagine I put a bowling ball at the center of the trampoline.

Lex Fridman (45:12.640)

Now I come up to the trampoline and I put a marble on, what happens?

Lex Fridman (45:18.000)

It'll roll towards the bowling ball.

Barry Barish (45:20.560)

Okay. All right. So what's happened is the presence of this massive object distorted the space

Barry Barish (45:28.880)

that the trampoline did. This is the same thing that happens to the presence of the earth,

Barry Barish (45:36.080)

the earth and the apple. The presence of the earth affects the space around it,

Lex Fridman (45:40.160)

just like the bowling ball on the trampoline.

Barry Barish (45:43.840)

Yeah. This doesn't make me feel better. I'm referring from the perspective of an

Barry Barish (45:47.280)

ant walking around on that trampoline. Then some guy just dropped a ball and then not only dropped

Barry Barish (45:55.760)

the ball, right? It's not just dropping a bowling ball. It's making the ball go up and down or doing

Barry Barish (46:02.640)

some kind of oscillation thing where it's like waves. And that's so fundamentally different from

Barry Barish (46:08.480)

the experience on being on flatland and walking around and just finding delicious, sweet things

Barry Barish (46:13.360)

as ant does. And it just feels like to me from a human experience perspective, completely,

Barry Barish (46:20.000)

it's humbling. It's truly humbling.

Lex Fridman (46:22.800)

It's humbling, but we see that kind of phenomenon all the time.

Barry Barish (46:26.800)

Let me give you another example. Imagine that you walk up to a still pond.

Lex Fridman (46:32.880)

Yes.

Barry Barish (46:33.440)

Okay. Now I throw, you throw a rock in it, what happens? The rock goes in, sinks to the bottom,

Barry Barish (46:41.360)

fine. And these little ripples go out and they travel out. That's exactly what happens. I mean,

Barry Barish (46:48.400)

there's a disturbance, which is these, say, the bowling ball or black holes. And then the ripples

Barry Barish (46:55.440)

that go out in the water, they're not, they don't have any, they don't have the rock, any part,

Barry Barish (47:01.520)

pieces of the rock.

Barry Barish (47:02.480)

See, the thing is, I guess what's not disturbing about that is it's a, I mean, I guess a flat

Barry Barish (47:10.000)

two dimensional surface that's being disturbed. Like for a three dimensional surface, a three

Lex Fridman (47:16.640)

dimensional space to be disturbed feels weird.

Barry Barish (47:19.840)

It's even worse. It's four dimensional because it's space and time.

Lex Fridman (47:23.120)

Time, yeah.

Lex Fridman (47:24.880)

So that's why you need Einstein is to make it four dimensional.

Lex Fridman (47:28.080)

To make it okay?

Barry Barish (47:29.440)

No, to make it.

Lex Fridman (47:30.640)

To make it four dimensional?

Barry Barish (47:31.680)

Yeah.

Barry Barish (47:32.320)

Yeah, to take the same phenomenon and look at it in all of space and time. Anyway,

Barry Barish (47:39.120)

luckily for you and I and all of us, the amount of distortion is incredibly small.

Lex Fridman (47:47.600)

So it turns out that if you think of space itself, now this is going to blow your mind too,

Barry Barish (47:54.240)

if you think of space as being like a material, like this table, it's very stiff. You know,

Barry Barish (48:00.000)

we have materials that are very pliable, materials that are very stiff. So space itself is very stiff.

Lex Fridman (48:06.480)

So when gravitational waves come through it, luckily for us,

Lex Fridman (48:09.520)

it doesn't distort it so much that it affects our ordinary life very much.

Barry Barish (48:16.240)

No, I mean, that's great. That's great. I thought there was something bad coming.

Barry Barish (48:19.920)

No, this is great. That's great news. So I mean, that, I mean, perhaps we evolved

Barry Barish (48:24.160)

as life on Earth to be such that for us, this particular set of effects of gravitational waves

Lex Fridman (48:32.800)

is not that significant. Maybe that's why.

Barry Barish (48:36.160)

It is. You probably used this effect today or yesterday.

Lex Fridman (48:41.760)

Did what?

Lex Fridman (48:42.960)

So it's pervasive. Well, because...

Lex Fridman (48:45.440)

You mean gravity or the way, or external? Because I only...

Barry Barish (48:49.440)

Curvature of space and time.

Barry Barish (48:50.720)

Curvature of space. How? I only care, a person is a human, right? The gravity of Earth.

Lex Fridman (48:56.000)

But you use it every day, almost.

Lex Fridman (48:59.360)

Oh, it's curving.

Barry Barish (49:00.240)

Uh huh.

Lex Fridman (49:00.720)

No, no, no.

Barry Barish (49:01.760)

No, no, no. It's in this thing. Every time it tells you where you are,

Lex Fridman (49:07.840)

how does it tell you where you are? It tells you where you are because we have

Barry Barish (49:11.520)

24 satellites or some number that are going around in space and it asks how long it takes

Lex Fridman (49:18.240)

the beam to go to the satellite and come back, the signal, to different ones.

Lex Fridman (49:24.320)

And then it triangulates and tells you where you are. And then if you go down the road,

Barry Barish (49:28.560)

it tells you where you are. Do you know that if you did that with the satellites and you

Lex Fridman (49:32.880)

didn't use Einstein's equations?

Lex Fridman (49:34.800)

Oh no.

Barry Barish (49:36.560)

You won't get the right answer. That's right. And in fact, if you take a road that's, say,

Barry Barish (49:42.400)

10 meters wide, I've done these numbers, and you ask how long you'd stay on the road if

Barry Barish (49:46.640)

you didn't make the correction for general relativity, this thing you're poo pooing,

Lex Fridman (49:52.160)

because you're using every day, you'd go off the road in about a minute.

Barry Barish (49:56.400)

Well, actually, that might be my problem.

Lex Fridman (49:57.200)

So you use it. So don't poo poo it.

Barry Barish (50:00.480)

Well, I think I'm using an Android, so maybe, and the GPS doesn't work that well, so maybe

Barry Barish (50:04.320)

I'm using Newton's physics. So I need to upgrade to general relativity. So gravitational waves

Lex Fridman (50:11.280)

and Einstein had, wait, Feynman really does have a part in the story?

Lex Fridman (50:16.720)

Yeah.

Lex Fridman (50:17.280)

Was that one of the first kind of experimental proposed to detect gravitational waves?

Lex Fridman (50:22.080)

Well, he did what we call a Godonkin experiment. That's a thought experiment.

Barry Barish (50:25.360)

Yes.

Barry Barish (50:25.680)

Okay. Not a real experiment. But then after that, then people believe gravitational waves

Barry Barish (50:31.760)

must exist. You can kind of calculate how big they are. They're tiny. And so people

Barry Barish (50:37.280)

started searching. The first idea that was used was Feynman's idea, and the very end of it.

Lex Fridman (50:44.080)

And it was to take a great big, huge bar of aluminum and then put around, and it's made

Barry Barish (50:51.360)

like a cylinder, and then put around it some very, very sensitive detectors so that if a

Barry Barish (50:57.360)

gravitational wave happened to go through it, it would go, and you'd detect this extra strain

Barry Barish (51:03.760)

that was there. And that was this method that was used until we came along. It wasn't a very

Barry Barish (51:10.080)

good method to use.

Lex Fridman (51:12.160)

And what was the, so we're talking about a pretty weak signal here.

Barry Barish (51:16.960)

Yeah, that's why that method didn't work.

Lex Fridman (51:19.280)

So what, can you tell the story of figuring out what kind of method would be able to detect

Lex Fridman (51:26.480)

this very weak signal of gravitational waves?

Lex Fridman (51:30.080)

So remembering what happens when you go to the amusement park, that it's going to do something

Barry Barish (51:38.320)

like stretch this way and squash that way, squash this way and stretch this way. We do

Barry Barish (51:44.400)

have an instrument that can detect that kind of thing. It's called an interferometer.

Lex Fridman (51:50.880)

And what it does is it just basically takes, usually light, and the two directions that

Barry Barish (51:58.720)

we're talking about, you send light down one direction and the perpendicular direction.

Lex Fridman (52:04.240)

And if nothing changes, it takes the same, and the arms are the same length, it just

Barry Barish (52:10.720)

goes down, bounces back. And if you invert one compared to the other, they cancel so

Barry Barish (52:16.080)

that nothing happens.

Lex Fridman (52:17.680)

But if it's like the amusement park and one of the arms got shorter and fatter, so it

Barry Barish (52:24.080)

took longer to go horizontally than it did to go vertically, then when the light comes

Barry Barish (52:30.480)

back, that comes back somewhat out of time. And that basically is the scheme. The only

Barry Barish (52:37.280)

problem is that that's not done very accurately in general, and we had to do it extremely

Lex Fridman (52:44.880)

accurately.

Lex Fridman (52:45.840)

So what's the difficulty of doing so accurately?

Barry Barish (52:52.160)

Okay. So the measurement that we have to do is a distortion in time. How big is it? It's

Barry Barish (53:00.960)

a distortion that's one part in 10 to the 21. That's 21 zeros and a one. Okay.

Lex Fridman (53:08.720)

So this is like a delay in the thing coming back?

Barry Barish (53:13.520)

One of them coming back after the other one, but the difference is just one part in 10

Barry Barish (53:17.920)

to the 21. So for that reason, we make it big, let the arms be long. Okay, so one part

Barry Barish (53:26.560)

in 10 to the 21. In our case, it's kilometers long. So we have an instrument that's kilometers

Lex Fridman (53:33.040)

in one direction, kilometers in the other.

Lex Fridman (53:34.880)

How many kilometers are we talking about? Four kilometers.

Barry Barish (53:37.360)

Four kilometers in each direction. If you take then one part in 10 to the 21, we're

Barry Barish (53:44.640)

talking about measuring something to 10 to the minus 18 meters.

Lex Fridman (53:54.720)

Okay.

Barry Barish (53:55.040)

Now, to tell you how small that is, the proton thing we're made of, which you can't go

Lex Fridman (54:01.520)

and grab so easily, is 10 to the minus 15 meters. So this is one one thousandth the

Barry Barish (54:07.200)

size of a proton. That's the size of the effect. Einstein himself didn't think this

Barry Barish (54:13.920)

could be measured. We've never seen, actually, he said that. But that's because he didn't

Barry Barish (54:19.760)

anticipate modern lasers and techniques that we developed.

Barry Barish (54:27.200)

Okay. So maybe can you tell me a little bit what you're referring to as LIGO, the Laser

Barry Barish (54:34.240)

Interferometer Gravitational Wave Observatory. What is LIGO? Can you just elaborate kind

Lex Fridman (54:40.560)

of the big picture view here before I ask you specific questions about it?

Barry Barish (54:44.160)

Yeah. So in the same idea that I just said, we have two long vacuum pipes, four kilometers

Barry Barish (54:54.400)

long. We start with a laser beam and we divide the beam going down the two arms. And we have

Barry Barish (55:03.200)

a mirror at the other end, reflects it back. It's more subtle, but we bring it back. If

Barry Barish (55:09.920)

there's no distortion in space time and the lengths are exactly the same, which we calibrate

Barry Barish (55:14.800)

them to be, then when it comes back, if we just invert one signal compared to the other,

Barry Barish (55:20.720)

they'll just cancel. So we see nothing. Okay. But if one arm got a little bit longer than

Barry Barish (55:26.800)

the other, then they don't come back at exactly the same time. They don't exactly cancel.

Barry Barish (55:31.760)

That's what we measure. So to give a number to it, we have the change of length to be

Barry Barish (55:42.320)

able to do this 10 to the minus 18 meters to one part in 10 to the 12th. And that was

Barry Barish (55:48.480)

the big experimental challenge that required a lot of innovation to be able to do.

Barry Barish (55:55.920)

You gave a lot of credit to, I think, Caltech and MIT for some of the technical developments

Barry Barish (56:02.560)

within this project. Is there some interesting things you can speak to at the low level of

Barry Barish (56:10.240)

some cool stuff that had to be solved? I'm a software engineer, so I have so much more

Barry Barish (56:17.600)

respect for everything done here than anything I've ever done. So I'll give you an example

Barry Barish (56:25.440)

of doing mechanical engineering at a better, basically mechanical engineering and geology

Lex Fridman (56:35.840)

and maybe at a level. So what's the problem? The problem is the following, that I've given

Barry Barish (56:42.480)

you this picture of an instrument that by some magic, I can make good enough to measure

Barry Barish (56:47.920)

this very short distance. But then I put it down here, it won't work. And the reason it

Barry Barish (56:54.000)

doesn't work is that the Earth itself is moving all over the place all the time. You don't

Barry Barish (56:59.600)

realize it, it seems pretty good to you, but it's moving all the time. So somehow it's

Barry Barish (57:05.680)

moving so much that we can't deal with it. We happen to be trying to do the experiment

Barry Barish (57:10.320)

here on Earth, but we can't deal with it. So we have to make the instrument isolated

Barry Barish (57:16.160)

from the Earth at the frequencies we're at. We've got to float it. That's an engineering

Lex Fridman (57:23.040)

problem, not a physics problem.

Lex Fridman (57:24.720)

So we're having a conversation on a podcast right now, and people who record music work

Barry Barish (57:32.160)

with this, how to create an isolated room. And they usually build a room within a room,

Lex Fridman (57:39.040)

but that's still not isolated. In fact, they say it's impossible to truly isolate from

Barry Barish (57:43.200)

sound, from noise and stuff like that. But that's like one step of millions that you

Barry Barish (57:51.760)

took is building a room inside a room, because you basically have to isolate all.

Barry Barish (57:56.800)

No, this is actually an easier problem. You just have to do it really well. So making

Barry Barish (58:02.000)

a clean room is really a tough problem because you have to put a room inside a room. This

Barry Barish (58:07.920)

is really simple engineering or physics. Okay, so what do you have to do? How do you isolate

Barry Barish (58:14.080)

yourself from the Earth? First, we work at, we're not looking at all frequencies for

Barry Barish (58:21.600)

gravitational waves. We're looking at particular frequencies that you can deal with here on

Barry Barish (58:26.560)

Earth. So what are frequencies would those be? You were just talking about frequencies.

Barry Barish (58:34.000)

We know by evolution, our bodies know, it's the audio band. Okay, the reason our ears

Barry Barish (58:40.800)

work where they work is that's where the Earth isn't going, making too much noise.

Barry Barish (58:45.040)

Okay, so the reason our ears work the way they work is because this is where it's quiet.

Barry Barish (58:48.720)

That's right. So if you go to one Hertz instead of 10 Hertz, the Earth is really moving around.

Lex Fridman (58:59.520)

So somehow we live in what we call the audio band. It's tens of Hertz to thousands of Hertz.

Barry Barish (59:06.320)

That's where we live, okay? If we're going to do an experiment on the Earth, it's the

Barry Barish (59:14.000)

same frequency. That's where the Earth is the quietest. So we have to work in that frequency.

Lex Fridman (59:18.000)

So we're not looking at all frequencies, okay? So the solution for the shaking of the Earth

Barry Barish (59:25.440)

to get rid of it is pretty mundane if we do the same thing that you do to make your car drive

Barry Barish (59:33.840)

smoothly down the road. So what happens when your car goes over a bump? Early cars did that,

Lex Fridman (59:39.760)

they bounced. Right.

Barry Barish (59:41.280)

Okay, but you don't feel that in your car. So what happened to that energy? You can't just

Barry Barish (59:47.120)

disappear energy. So we have these things called shock absorbers in the car. What they do is they

Barry Barish (59:53.840)

take the thing that went like that, and they basically can't get rid of the energy, but they

Barry Barish (59:58.880)

move it to very, very low frequency. So what you feel isn't, you feel it go smoothly, okay? All