Barry Barish is a theoretical physicist at Caltech and the winner of the Nobel Prize in Physics. Please support this podcast by checking out our sponsors:
- MUD\WTR: https://mudwtr.com/lex and use code LEX to get 5% off
- GiveDirectly: https://givedirectly.org/lex to get gift matched up to $300
- BiOptimizers: http://www.magbreakthrough.com/lex to get 10% off
- Four Sigmatic: https://foursigmatic.com/lex and use code LexPod to get up to 60% off
- Magic Spoon: https://magicspoon.com/lex and use code LEX to get $5 off

EPISODE LINKS:
Barry's Nobel Prize entry: https://www.nobelprize.org/prizes/physics/2017/barish/facts/
Barry's Caltech profile: https://pma.caltech.edu/people/barry-c-barish
LIGO's Website: https://www.ligo.caltech.edu/
LIGO's Twitter: https://twitter.com/LIGO

PODCAST INFO:
Podcast website: https://lexfridman.com/podcast
Apple Podcasts: https://apple.co/2lwqZIr
Spotify: https://spoti.fi/2nEwCF8
RSS: https://lexfridman.com/feed/podcast/
Full episodes playlist: https://www.youtube.com/playlist?list=PLrAXtmErZgOdP_8GztsuKi9nrraNbKKp4
Clips playlist: https://www.youtube.com/playlist?list=PLrAXtmErZgOeciFP3CBCIEElOJeitOr41

OUTLINE:
0:00 - Introduction
1:08 - Early math and physics questions
10:42 - Enrico Fermi
17:14 - Birth of the Nuclear Age
22:22 - The Fermi Paradox
27:26 - Gravity
44:08 - Philosophical implications of general relativity
51:14 - Detecting gravitational waves
54:28 - LIGO
1:27:25 - Nobel Prize
1:42:14 - Black holes
1:54:34 - Space exploration
2:02:28 - Books
2:11:17 - Advice for young people
2:17:13 - Meaning of life

SOCIAL:
- Twitter: https://twitter.com/lexfridman
- LinkedIn: https://www.linkedin.com/in/lexfridman
- Facebook: https://www.facebook.com/lexfridman
- Instagram: https://www.instagram.com/lexfridman
- Medium: https://medium.com/@lexfridman
- Reddit: https://reddit.com/r/lexfridman
- Support on Patreon: https://www.patreon.com/lexfridman

The following is a conversation with Barry Barish, a theoretical physicist at Caltech, and the winner of the Nobel Prize in Physics for his contributions to the LIGO detector and the observation of gravitational waves.

LIGO, or the Laser Interferometer Gravitational-Wave Observatory, is probably the most precise measurement device ever built by humans.

It consists of 2 detectors with 4 kilometer long vacuum chambers situated 3,000 kilometers apart, operating in unison to measure a motion that is 10,000 times smaller than the width of a proton.

It is the smallest measurement ever attempted by science, a measurement of gravitational waves caused by the most violent and cataclysmic events in the universe, occurring over tens of millions of light years away.

To support this podcast, please check out our sponsors in the description.

This is the Lex Friedman Podcast, and here is my conversation with Barry Barish.

You've mentioned that you were always curious about the physical world, and that an early question you remember stood out where you asked your dad, why does ice float on water?

Maybe you can speak to what are some early questions in math and physics that really sparked your curiosity?

Yeah, that memory is kind of something I used to illustrate something I think that's common in science, is that people that do science somehow have maintained something that kids always have.

A small kid, 8 years old or so, asks you so many questions usually, typically that you consider them pests, you tell them to stop asking so many questions.

And somehow our system manages to kill that in most people.

So in school we make people do study and do their things, but not to pester them by asking too many questions.

And I think, not just myself, but I think it's typical of scientists like myself that have somehow escaped that.

Maybe we're still children, or maybe we somehow didn't get it beaten out of us, but I think it's, I teach in college level, and it's, to me, 1 of the biggest deficits is the lack of curiosity, if you want, that we've beaten out of them, because I think It's an innate human quality.

Is there some advice or insights you can give to how to keep that flame of curiosity going?

I think it's a problem of both parents and the parents should realize that's a great quality we have, that you're curious and that's good.

Instead, we have expressions like curiosity killed the cat.

And more, but I mean, basically it's not thought to be a good thing, curiosity killed the cat means if you're too curious you get in trouble.

I don't like cats anyway, so maybe it's a good thing.

That, to me, needs to be solved, really, in education and in homes.

That realization that there's certain human qualities that we should try to build on and not destroy, 1 of them is curiosity.

I was a pest and asked a lot of questions.

My father generally could answer them at that age.

And the first 1 I remember that he couldn't answer was not a very original question, but basically that ice is made out of water, and so why does it float on water?

And it may not have been the first question.

And that was the first time that I realized that to learn and answer your own curiosity or questions, there's various mechanisms.

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

But eventually you do it by what we call research.

But it's driven by, if you're, hopefully you ask good questions, if you ask good questions and you have the mechanisms to solve them, then you do what I do in life, basically.

Not necessarily physics, but, and it's a great quality in humans and we should nurture it.

Do you remember any other kind of, in high school, maybe early college, more basic physics ideas that sparked your curiosity, or mathematics or science in

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

But just staying with water for a minute, I remember that I was curious what happens to water?

It rains and there's water in a wet pavement, and then the pavement dries out.

What happened to this water that came down?

And then eventually I learned in chemistry or something, water's made out of hydrogen and oxygen.

Those are both gases, so how the heck does it make this substance this liquid?

Yeah, so that has to do with states of matter.

You've, I know perhaps LIGO and the thing for which you've gotten the Nobel Prize and the things much of your life work, perhaps was a happy accident in some sense in the early days, but is there a moment where you looked up to the stars and also the same way you wondered about water, wondered about some of the things that are out there in the universe?

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

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

And the more we learn, the more we know we don't know.

I mean, we don't know what the majority of anything is out there.

It's all what we call dark matter, dark energy, and that's 1 of the big questions.

When I was a student, those weren't questions.

So we even know less in a sense the more we look.

Of course, I think that's 1 of the areas that almost it's universal.

People see the sky, they see the stars and they're beautiful and see it looks different on different nights and it's a curiosity that we all have.

What are some questions about the universe that in the same way that you felt about the ice, that today, you mentioned to me offline, you're teaching a course on the frontiers of science, frontiers of physics.

What are some questions, outside the ones we'll probably talk about, that kind of, Yeah, fill you with, get your flame of curiosity up and firing up, you know, fill you with awe.

Well, first I'm a physicist, not an astronomer, so I'm interested in the physical phenomenon, really.

So the question of dark matter and dark energy, which we probably won't talk about, are recent, they're the last 20, 30 years, or certainly dark energy.

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

It basically takes something that he thought was what he called a constant, which isn't, and if that's even the right theory, and it represents most of the universe.

And then we have something called dark matter, and there's good reason to believe it might be an exotic form of particles, and That is something I've always worked on particle accelerators and so forth.

It's a bit of a cottage industry and that there's lots and lots of searches.

But it may be a little bit like, you know, looking for a treasure under rocks or something.

You don't, it's hard to, we don't have really good guidance except that we have very, very good information that is pervasive and it's there.

And that it's probably particles, small, that evidences all of those things.

But then the most logical solution doesn't seem to work, something called supersymmetry.

do you think the answer could be something very complicated?

You know, I like to hope that, think that most things that appear complicated are actually simple if you really understand them.

I think we just don't know at the present time and it isn't something that affects us.

It does affect, it affects how the stars go around each other and so forth, because we detect that there's missing gravity, but it doesn't affect everyday life at all.

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

Do you think those answers might change the way we see other sources of gravity, black holes, the way we see the parts of the universe that we do study?

The black holes that we've found in our experiment and we're trying now to understand the origin of those.

It's conceivable but doesn't seem the most likely that they were primordial, that is they were made at the beginning.

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

So there can be connections, dark black holes, or how many there are, how much of the mass they encompass is still pretty primitive, we don't know.

So before I talk to you more about black holes, let me take a step back to, I was actually went to high school in Chicago and would go to take classes at Fermilab, watch the Buffalo and so on.

So let me ask about, you mentioned that Enrico for me was somebody who was inspiring to you in a certain kind of way.

He's the last, this is not the, I'll come to the reason in a minute, but he had a big influence on me at a young age.

But he was the last physicist of note that was both an experimental physicist and a theorist at the same time.

And he did 2 amazing things within months.

In 1933, we didn't really know what the nucleus was, what radioactive decay was, what beta decay was when electrons come out of a nucleus.

And near the end of 1933, the neutron had just been discovered.

And that meant that we knew a little bit more about what the nucleus is, that it's made out of neutrons and protons.

The neutron wasn't discovered until 1932.

And once we discovered that there was a neutron and proton and they made the nucleus and then there are electrons that go around.

And he wrote down not only just the theory, a theory, but a theory that lasted decades and has only been improved on, of beta decay, that is the radiation.

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

He submitted it to Nature magazine, which was the primary best place to publish even then, And it got rejected as being too speculative.

And so he went back to his drawing board in Rome where he was, added some to it, made it even longer, because it's really a classic article, and then published it in the local Italian journal for physics and the German 1.

At the same time, in January of 1932, Giulio and Curie for the first time saw artificial radioactivity.

This was an important discovery because radioactivity had been discovered much earlier.

They had x-rays and You shouldn't be using them, but there was radioactivity.

But radioactive materials are hard to find, and so it wasn't prevalent.

But if you could make them, then they had great use.

Giulio and Curie were able to bombard aluminum or something with alpha particles and find that they excited something that decayed and had some half-life and so forth, meaning it was artificial version, or let's call it not a natural version, an induced version of radioactive materials.

Fermi somehow had the insight, and I still can't see where he got it, that the right way to follow that up was not using charged particles like alphas and so forth, but use these newly discovered neutrons as the bombarding particle.

It was hard to get very many of them, but it had the advantage that They're not charged, so they go right into the nucleus.

And that turned out to be the experimental work that he did that won him the Nobel Prize.

And it was the first step in fission, discovery of fission.

And he did this 2 completely different things, an experiment that was a great idea and a tremendous implementation because how do you get enough neutrons?

And then he learned quickly that not only do you want neutrons, but you want really slow ones.

He learned that experimentally, and he learned how to make slow ones, and then they were able to make, go through the periodic table and make lots of particles.

He missed on fission at the moment, but he had the basic information and then fission follows soon after that.

Forgive me for not knowing, but is the birth of the idea of bombarding neutrons, Is that an experimental idea?

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

I think it took a combination because he realized that neutrons had a characteristic that would allow them to go all the way into the nucleus when we didn't really understand what the structure was of all this.

So that took an understanding or recognition of the physics itself of how a neutron interacts compared to say an alpha particle that Giulio and Curie had used.

And then he had to invent a way to have enough neutrons and he had a team of associates and he pulled it off quite quickly.

And probably, maybe you can speak to it, his ability to put together the engineering aspects of great experiments and doing the theory, they probably fed each other.

I wonder, can you speak to why we don't see more of that?

I think in both theory and experiment, in physics anyway, was it was conceivable if you had the right person to do it, and no one's been able to do it since.

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

So you loved both sides of it, the theory and

Yeah, I never liked the idea that you did experiments without really understanding the theory or the theory should be related very closely to experiments.

And so I've always done experimental work that was closely related to the theoretical ideas.

I think I told you I'm Russian, so I'm gonna ask some romantic questions, but is it tragic to you that he's seen as the architect of the nuclear age, that some of his creations led to potentially, some of his work has led to potentially still the destruction of the human species, some of the most destructive weapons.

I think even more general than him, I gave you all the virtues of curiosity a few minutes ago.

There's an interesting book called The Ratchet of Curiosity.

You know, a ratchet is something that goes in 1 direction.

And that is written by a guy who's probably a sociologist or philosopher or something.

And he picks on this particular problem, but other ones, and that is the danger of knowledge, basically.

So it's a little bit like curiosity killed the cat.

You have to be worried about whether you can handle new information that you get.

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

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

Yeah, And Fermi himself was a very apolitical person.

So, he wasn't very driven by, or at least he appears in all of his writing, the writing of his wife, the interactions that others had with him as either he avoided it all or he was pretty apolitical.

I mean, he just saw the world through kind of the lens of a scientist.

The bomb was tragic, certainly on Japan, and he had a role in that.

So I wouldn't want it as my legacy, for example.

I mean, but brought it to the human species that it's the ratchet of curiosity that we, We do stuff just to see what happens.

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

There on a small scale, on a silly scale perhaps currently, there's constantly unintended consequences.

You create a system and you put it out there and you have intuitions about how it will work, you have hopes how it will work, but you put it out there just to see what happens.

And in most cases, because artificial intelligence is currently not super powerful, it doesn't create large-scale negative effects.

But that same curiosity, as it progresses, might lead to something that destroys the human species.

And the same may be true for bioengineering.

There's people that engineer viruses to protect us from viruses, to see how close is this to mutating so it can jump to humans or engineering defenses against those.

And it seems exciting and the positive applications are really exciting at this time, but we don't think about how that runs away in decades to come.

Yeah, and I think it's the same idea as this little book, The Ratchet of Science, The Ratchet of Curiosity.

I mean, whether you pursue, take curiosity and let artificial intelligence or machine learning run away with having its solutions to whatever you want or we do it, is I think a similar consequence.

I think from what I've read about Enrico Fermi, he became a little bit cynical about the human species towards the end of his life, about having observed what he observed.

There was already the work by Teller to develop the hydrogen bomb, and I think he was a little cynical of that, pushing it even further, and the rising tensions between the Soviet Union and the US and looked like an endless thing.

But he didn't say very much, but a little bit, as you said.

Yeah, there's a few clips to sort of maybe picked on a bad mood, but in a sense that, almost like a sadness, a melancholy sadness to a hope that waned a little bit about that perhaps we can do, this curious species can find the way out.

Well, especially I think people who worked like he did at Los Alamos and spent years of their life somehow had to convince themselves that dropping these bombs would bring lasting peace.

As a small interesting aside, it'd be interesting to hear if you have opinions on this.

His name is also attached to the Fermi paradox, which asks if there is a, you know, it's a very interesting question, which is, it does seem if you sort of reason basically that there should be a lot of alien civilizations out there.

If the human species, if Earth is not that unique, by basic, no matter the values you pick, it's likely that there's a lot of alien civilizations out there, and if that's the case, why have they not at least obviously visited us or sent us loud signals that everybody can hear?

Fermi's quoted as saying, sitting down at lunch, I think it was with Teller and Herb York, who was kind of 1 of the fathers of the atomic bomb.

And he sat down and he says something like, where are they?

And then he did some numerology where he calculated, you know, how many, what they knew about how many galaxies there are and how many stars and how many planets there are like the earth and blah, blah, blah.

That's been done much better by somebody named Drake.

And so people usually refer to the, I don't know whether it's called the Drake formula or something, but it has the same conclusion.

The conclusion is it would be a miracle if there weren't other, you know, the statistics are so high that how can we be singular and separate?

That, so probably there is, but there's almost certainly life somewhere.

Maybe there was even life on Mars a while back, but intelligent life, probably.

Statistics say that communicating with us, I think that it's harder than people think.

We might not know the right way to expect the communication, But all the communication that we know about travels at the speed of light, and we don't think anything can go faster than the speed of light.

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

You can send signals like we try to or look for, but to have any communication, it's pretty hard when it has to be close enough that the speed of light would mean we could communicate with each other.

I mean, we're an advanced civilization, but we didn't even understand that a little more than a hundred years ago.

So are we just not advanced enough maybe to know something about that's the speed of light?

Maybe there's some other way to communicate that isn't based on electromagnetism?

Gravity seems to be also have the same speed.

That was a principle that Einstein had, and something we've measured actually.

So is it possible, I mean, so we'll talk about gravitational waves, and in some sense there's a brainstorming going on, which is like, how do we detect the signal?

Like, what would a signal look like, and how would we detect it?

And that's true for gravitational waves, that's true for basically any physics phenomena.

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

I mean, is it possible that aliens are communicating with us via gravity?

For us, it's very hard to detect these gravitational effects.

They have to come from something pretty that has a lot of gravity, like black holes.

But we're pretty primitive at this stage.

There's very reputable physicists that look for a fifth force, 1 that we haven't found yet.

What would a fifth force of physics look like exactly?

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

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

It doesn't fall off like 1 over r squared, but maybe separately.

Gravity, Newton taught us, goes like inversely, 1 over the square of the distance apart you are.

That's okay, so Now we have a theory of what consciousness is.

Speaking of gravity, What are gravitational waves?

You and you were young, you were told that if you jumped up, the earth pulled you down.

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

Maybe you even asked your teacher why, but most of us accepted that, that was Newton's picture, the apple falling out of the tree.

But Newton's theory never told you why the apple was attracted to the earth.

Newton's theory also, Newton recognized at least 1 of the 2 problems I'll tell you.

1 of them is, there's more than those, but 1 is why does the Earth, what's the mechanism by which the Earth pulls the apple or holds the moon when it goes around, whatever it is?

That's not explained by Newton, even though he has the most successful theory of physics ever went 200 and some years with nobody ever seeing a violation.

But he accurately describes the movement of an object falling down to Earth, but he's not answering why that, what's, yeah, because it's at a distance, right?

He gives a formula, which it's a product of the Earth's mass, the apple's mass, inversely proportional to the square, the distance between, and then the strength, he called capital G, the strength he couldn't determine, but it was determined 100 years later.

But no 1 ever saw a violation of this until a possible violation which Einstein fixed, which was very small, that has to do with mercury going around the sun, the orbit being slightly wrong if you calculate it by Newton's theory.

But so, like most theories then in physics, you can have a wonderful 1 like Newton's theory, it isn't wrong, but you have to have an improvement on it to answer things that it can't answer.

And in this case, Einstein's theory is the next step.

We don't know if it's anything like a final theory or even the only way to formulate it either.

But he formulated this theory, which he released in 1915.

He took 10 years to develop it, even though in 1905, he solved 3 or 4 of the most important problems in physics in a matter of months, and then he spent 10 years on this problem before he let it out.

And this is called general relativity, it's a new theory of gravity, 1915.

In 1916, Einstein wrote a little paper where he did not do some fancy derivation.

Instead he did, what I would call, he used his intuition, which he was very good at too.

And that is he noticed that if he wrote the formulas for general relativity in a particular way, they looked a lot like the formulas for electricity and magnetism.

Being Einstein, he then took the leap that electricity and magnetism, we discovered only 20 years before that, in the 1880s, have waves.

Of course, that's light and electromagnetic waves, radio waves, everything else.

So he said if the formulas look similar, then gravity probably has waves too.

I mean, maybe you can correct me, but that just seems like a heck of a leap.

See all Lex Fridman transcripts on Youtube

Barry Barish: Gravitational Waves and the Most Precise Device Ever Built | Lex Fridman Podcast #213