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

1. 0:00 – 1:08

   Introduction

   1. LFLex Fridman0:00

      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 two detectors with four kilometer-long vacuum chambers situated 3,000 kilometers apart, operating in unison to measure 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 Fridman Podcast, and here is my conversation with Barry Barish.

2. 1:08 – 10:42

   Early math and physics questions

   1. LFLex Fridman1:08

      You've mentioned that you were always curious about the physical world, and that, uh, an early question you remember stood out where you asked your dad, "Why does ice float on water?" And he couldn't answer, and this was very (laughs) surprising to you. Uh, so you went on to learn why. Maybe you can speak to what are some early questions in math and physics that, uh, really sparked your curiosity?

   2. BBBarry Barish1:31

      Yeah. Th- that, that memory is, uh, um, kind of something I use to illustrate, uh, something I think that's common in science, is that people that do science somehow have maintained, um, maintain something that kids always have. Uh, well, a small kid, eight years old or so, uh, asks you so many questions usually, typically, that you consider them pests, you tell them to stop asking so many questions. Um, and, uh, somehow our system manages to kill that in most people. Uh, so, in school we make people do s- study and w- do their things, but not to pester them by asking too many questions. And, uh, um, I think not just myself, but I think it's typical of scientists like myself, that, uh, uh, 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, uh... I teach in college level and it's, to me, uh, one of the biggest deficits is the lack of curiosity, if you want, that we've beaten out of them, 'cause I think it's an innate human quality.

   3. LFLex Fridman2:47

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

   4. BBBarry Barish2:51

      I think it's a problem of both parents and, and, uh, that parents should be, should realize that's a great quality we have, that you're curious and that's good. Instead we have s- we have expressions like, "Curiosity killed the cat."

   5. LFLex Fridman3:05

      (laughs)

   6. BBBarry Barish3:06

      And, and, uh, and then more. But I mean that basically it's not, not thought to be a good thing. You get i- curiosity killed the cat means if you're too curious you get in trouble. And, uh, it can lead to trouble.

   7. LFLex Fridman3:18

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

   8. BBBarry Barish3:20

      Yeah. Yeah. That to me needs to be solved really in education and in homes, that, uh, realization that there's certain human qualities that we should try to build on and not destroy, one of them is curiosity. Anyway, back to me and curiosity. I was a pest and asked a lot of questions, my father generally could answer them, uh, at that age. And the first one I remember that he couldn't answer, uh, was not a very original question, but basically that, uh, ice is made out of water, and so why does it float on water? Uh, and, uh, he couldn't answer it. And it may not have been the first question, it's the first one that I remember. And, uh, 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 and, or asking people who know more and so forth. But eventually you do it by what we call research. But, but it's, um, driven by if you're... uh, 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, uh, s- and it's a great quality in humans and we should nurture it.

   9. LFLex Fridman4:46

      Do, 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 general?

   10. BBBarry Barish4:57

       I, I wasn't really into science until I got to college-

   11. LFLex Fridman5:01

       Yes.

   12. BBBarry Barish5:01

       ... to be honest with you. But just staying with water for a minute, I remember, uh, that I was curious, uh, why, uh, what happens to water? You know, it rains and there's water, and a wet pavement and then the pavement dries out, what happened to this water that came down? And I, you know, I didn't know that much. And then l- eventually I learned in chemistry or something that water's made out of hydrogen and oxygen, those are both gases, so how the heck does it make this substance, this liquid? Uh...

   13. LFLex Fridman5:36

       (laughs)

   14. BBBarry Barish5:36

       (laughs)

   15. LFLex Fridman5:37

       Yeah. It's, uh, but... So that has to do with states of matter. You've, uh, I know perhaps LIGO and all, all, uh, the, the thing for which you've gotten the Nobel Prize and the things much of your life work m- m- perhaps was a happy accident in some sense in the early days. But is, 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?

   16. BBBarry Barish6:03

       Oh, yeah. I think everybody's looks and is in awe, and is curious about what, what it is out there. And it, you know, 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 or dark energy, and that's one of the big questions 20 year, when I was a student, those weren't questions. So we even know less in a sense the more we, uh, the more we look. So of, of course, I think that's one of the areas that, um, almost it's universal. People see the sky, they see the stars and they're beautiful, and, and see it looks different on different nights, and it's a, a curiosity that we all have.

   17. LFLex Fridman6:55

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

   18. BBBarry Barish7:09

       Yeah.

   19. LFLex Fridman7:10

       What are some questions, outside the ones we'll probably talk about, that kind of, yeah, f- fill you with, uh, get your flame of curiosity up in the, firing up, uh, you know, fill you with awe?

   20. BBBarry Barish7:26

       Well, first, I'm a physicist not an astronomer, so I'm interested in physic-, the physical phenomenon really. So the question of, of, uh, dark matter and dark energy, which we probably won't talk about are rec-, are recent. They're the last 20, 30 years for certainly dark energy. Dark energy is a complete puzzle. It, it goes against what I'll, will, what you will ask me about, which is general relativity and Einstein's general relativity, it basically takes something that he thought was, uh, what he, what he called a constant, which isn't, and, and, uh, um, 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. Um, and that is something I've always worked on, on particle accelerators and so forth. And it's a big puzzle what it is. It's a bit of a cottage industry in that there's lots and lots of searches, um, 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 ha- uh, we don't have really good guidance except that we have very, very good information that it's pervasive and it's there.

   21. LFLex Fridman8:48

       Mm-hmm.

   22. BBBarry Barish8:48

       And that it's probably particles, small, that, that evidences all of those things. But then the most, uh, logical solution doesn't seem to work, something called super symmetry.

   23. LFLex Fridman9:01

       Mm-hmm. And do you think the answer could be something very complicated?

   24. BBBarry Barish9:08

       You know, I like to hope that, think that most things that appear complicated are actually simple if you really understand them, and 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, 'cause we detect that there's missing gravity, but, uh, but it doesn't affect everyday life at all. I tend to think and expect maybe, and that the answers will be simple and we just haven't found it yet.

   25. LFLex Fridman9:45

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

   26. BBBarry Barish9:56

       It's, it's conceivable. Uh, the black holes that we found in our experiment and how we are trying now to understand the origin of those, it's conceivable but not, doesn't seem the most likely that they are pre-mort, primordial. That is, they were made at the beginning, and they, in that sense, they could represent at least part of the dark matter. So there can be connections. Dark, uh, black holes or how many there are, how much of the mess they encompass is still root pretty primitive, we don't know.

   27. LFLex Fridman10:28

       So before I talk to you more about black holes, let me take a step back to-

   28. BBBarry Barish10:31

       Yeah.

   29. LFLex Fridman10:32

       I was, actually went to high school in Chicago and would go to, uh, take, uh, classes at Fermilab, uh, watch the Buffalo and so on.

   30. BBBarry Barish10:41

       Yeah. (laughs)

3. 10:42 – 17:14

   Enrico Fermi

   1. BBBarry Barish10:43

   2. LFLex Fridman10:43

      (laughs) So let me ask about the, you mentioned that Enrico Fermi was somebody who was inspiring to you in a certain kind of way. Um, why is that? Can you speak to that?

   3. BBBarry Barish10:52

      Sure. He was amazing actually. Uh, he's the last, th- this is not the re-, I'll come to the reason in a minute, but the, he had a big influence on me at a young age. Uh, he, he, uh, but he was the onl-, the last physicist of note that was both an experimental physicist and a theorist at the same time, and he did two amazing things within months. I- in 1933, he, w- it was, we didn't really know what the nucleus was, what, uh, radioactive decay was, what beta decay was when electrons come out of a nucleus, and in th- near the, near the end of 1933, um, he, 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 till 1932, and then once we discovered that there was a neutron and proton and they made the nucleus and then there are electrons that go around, the basic ingredients were there, and he, uh, wrote down not only just the theory, a theory, but a theory that lasted decades and has only been improved on, uh, of beta decay, that is the radi- radiation. He did this w-... came out of nowhere, and it was a fantastic theory. He, uh, submitted it to Nature Magazine, which was the primary, uh, pla- best place to publish even then, and it got rejected as being too, uh, speculative. And so, he went back to his, uh, drawing board in Rome, where he was, added some to it, made it even longer, uh, 'cause it's really a classic article, and then published it in the local Italian, uh, journal for physics and the German one. At the same time, in 19- January of 1932, Giulio and Curie for the first time s- div- uh, saw artificial radioactivity. This was an important discovery because radioactivity had been discovered much earlier. And, you know, we'd... They had X-rays, and you shouldn't be using them, but they- there was radioactivity. People knew it was useful for medicine. But radioactive materials were hard to find, and so it wasn't prevalent. But if you could make them, then they had great use. And Giulio and Curie were able to bombard, uh, aluminum or something with alpha particles and f- find that they excited something that decayed and gave, uh, decayed and ga- had some half-life and so forth, meaning it was an artificial version, or let's call it a, not, not a natural version, an induced version of radioactive, uh, uh, materials. And, uh, Fermi somehow had the insight, and, uh, 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, use these newly discovered neutrons as the bombarding particle. Seemed impossible. They barely had been seen. Uh, it was hard to get very many of them. But it had the advantage that they don't, um, they're not charged, so they go right into the, to the nucleus, and, uh, that turned out to be the experimental work that he did that, uh, won him the Nobel Prize. And it was the first step in fission, uh, uh, discovery of fission. And that's... He did this, two completely different things. Uh, an experiment that was a great idea, and, uh, tremendous implementation because how do you get enough neutrons?

   4. LFLex Fridman14:57

      Mm-hmm.

   5. BBBarry Barish14:57

      And then he learned quickly that not only do you want neutrons, but you want really slow ones. Uh, and he, he learned that experimentally, and he learned how to make slow ones, and then they were able to make... uh, go through the periodic table and make lots of, uh, particles. He missed on fission at the moment, but he had the basic information, and th- and then fission followed soon after that.

   6. LFLex Fridman15:22

      Forgive me for not knowing, but wha- is the birth of the idea of bombarding with nu- uh, neutrons, is that, uh, is that an experimental idea? Was it born out of an experiment, he just observed something? Or is this an Einstein-sty- style idea where you come up from basic intuition?

   7. BBBarry Barish15:40

      I think, I think, I think, uh, that 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, you know, what, how, what the structure was of all this. So, that took, uh, 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, uh, uh, you know, uh, he had a team of associates and p- and he pulled it off quite quickly. So, you know, it was pretty astounding.

   8. LFLex Fridman16:22

      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 m- more of that? Is that just really difficult to do?

   9. BBBarry Barish16:38

      It's difficult to do. Yeah, I think i- in, in both theory and experiment in physics anyway was, uh, it was conceivable if you had an- the right person to do it, and no one's been able to do it since. So, I had the dream that that-

   10. LFLex Fridman16:54

       (laughs)

   11. BBBarry Barish16:54

       ... was what I was gonna be like Fermi. But...

   12. LFLex Fridman16:56

       So, you love both sides of it, the theory and experiment?

   13. BBBarry Barish16:58

       Yeah, 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.

4. 17:14 – 22:22

   Birth of the Nuclear Age

   1. BBBarry Barish17:14

   2. LFLex Fridman17:15

      I think I told you I'm Russian, so I'm gonna ask some romantic questions. Uh, but is- (laughs)

   3. BBBarry Barish17:20

      Yeah.

   4. LFLex Fridman17:20

      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, has led to potentially still the destruction of the human species? Some of the most destructive weapons-

   5. BBBarry Barish17:39

      Yeah. Uh, I think even more general than him, I, I, I, 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 one direction. And that, that, it's written by a guy who's probably a sociologist or a philosopher or something, and he, he picks on this particular problem, but other ones, and that is the, the danger of knowledge basically. You know, you're curious, you learn something. So, it's a little bit like curiosity killed the cat.

   6. LFLex Fridman18:12

      (laughs)

   7. BBBarry Barish18:12

      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. Uh, and Fermi himself was a, 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 is, either he avoided it all (laughs) or he was pretty apolitical. I mean, he just saw s- the world through kind of the lens of a scientist. But you asked if it's tragic? Uh, the, uh, 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.

   8. LFLex Fridman19:07

      I mean that... But broader to the human species that it's the ratchet of curiosity that we, (sighs) uh, we do stuff just to see what happens. That, that curiosity, that, uh, in sort of my area of artificial intelligence, that's been a, a concern. They're kind... On a small scale, on a silly scale perhaps currently, there's constantly s- unintended consequences, that 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.

   9. BBBarry Barish19:44

      Yeah. Th-

   10. LFLex Fridman19:45

       And, uh, in most cases because artificial intelligence is currently not super powerful, it doesn't create, uh, 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, uh, that, p- you know, engineer viruses to protect us from viruses, to see, you know, how do... Uh, how close is this to mutating so it can jump to humans? Or, or going, you know... Or engineering, uh, defenses against those. And it seems exciting and the application, the positive applications are really exciting at this time, but we don't think about how that runs away in decades to come.

   11. BBBarry Barish20:34

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

   12. LFLex Fridman20:39

       Yeah.

   13. BBBarry Barish20:40

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

   14. LFLex Fridman20:59

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

   15. BBBarry Barish21:13

       Well, he didn't write much. Uh, I mean, he died young. He died d- soon after World W- the World War. Uh, there was already, you know, the work by Teller to develop the hydrogen bomb, and I think he was a little cynical of that, you know, pushing it even further and, uh, rising tensions between the Soviet Union and the US, and looked like an endless thing, so. But he didn't say very much, uh, but a little bit as you said that-

   16. LFLex Fridman21:39

       Yeah, there's a few clips. This j-

   17. BBBarry Barish21:41

       Yeah.

   18. LFLex Fridman21:41

       ... sort of, uh, maybe picked on a bad mood, but in, in a sense-

   19. BBBarry Barish21:45

       (laughs) .

   20. LFLex Fridman21:46

       ... that, uh, almost like a sadness, a m- melancholy sadness to, um, a hope that waned a little bit about that, uh-

   21. BBBarry Barish21:54

       Yeah.

   22. LFLex Fridman21:55

       ... perhaps we can do, like, s- th- the scie- this curious species can find the way out.

   23. BBBarry Barish22:01

       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-

   24. LFLex Fridman22:12

       Yes, and it didn't.

   25. BBBarry Barish22:13

       ... and, and that it didn't. Yeah.

   26. LFLex Fridman22:17

       As a small interesting aside, it'd be intere- interesting to hear if you have opinions

5. 22:22 – 27:26

   The Fermi Paradox

   1. LFLex Fridman22:22

      on this. His name is also attached to the Fermi Paradox, which asks if there's, uh, you know, which formu-

   2. BBBarry Barish22:30

      Yeah, yeah.

   3. LFLex Fridman22:30

      .... it's a very interesting question-

   4. BBBarry Barish22:31

      Yeah, yeah.

   5. LFLex Fridman22:31

      ... which is... If... It does seem if you sort of reason basically that, 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, uh, 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?

   6. BBBarry Barish23:00

      Fermi's quoted as saying, sitting down at lunch, I think it was with, uh, Teller?

   7. LFLex Fridman23:07

      Mm-hmm.

   8. BBBarry Barish23:07

      And Herb York, who was kind of the f- one of the fathers of the atomic bomb, and he sat down and he says something like, "Where are they?"

   9. LFLex Fridman23:16

      Yeah. Yeah.

   10. BBBarry Barish23:17

       (laughs) Which meant where are these-

   11. LFLex Fridman23:19

       Yeah.

   12. BBBarry Barish23:19

       ... other... And, um, b- and then he did some numerology where he calculated, you know, how many... What they knew about how many, uh, galaxies there are and how many stars and how many planets then are like the Earth and blah, blah, blah.

   13. LFLex Fridman23:36

       Yep.

   14. BBBarry Barish23:36

       That's been done much better by somebody named Drake, uh, and so people usually refer to the Dr- 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... Uh, there's... The statistics are so high that how can we be singular and separate? Uh, th- that... So probably there is l- well, there's almost certainly life somewhere, maybe there was even life on Mars a while back. But, uh, intelligent life, probably. Why are we so... So, you know, the statistics say that. Communicating with us? I think that it's harder than people think (laughs) . Uh, we might not know the right way to expect the communication, uh, but-... all the communication that we know about travels at the speed of light and we d- we don't, we don't think anything can go faster than the speed of light. That limits the problem quite, quite a bit, and it, uh, makes it difficult to have any back and forth communication. You could send signals, like we try to or look for, but to have any communication, it's pretty hard when you... it has to be close enough that the speed of light, uh, would mean we could communicate with each other. And I, I think, and we didn't even understand that. I mean, it's, we're an advanced civilization but we didn't even understand that a little more than 100 years ago.

   15. LFLex Fridman25:12

       Yeah.

   16. BBBarry Barish25:13

       So, uh, are we just not advanced enough? Maybe.

   17. LFLex Fridman25:19

       Yeah.

   18. BBBarry Barish25:20

       Uh, to know something about that's the speed of light, maybe there's some other way to communicate that isn't based on electromagnetism. I don't, I don't know. Gravity seems to be also this, have the same speed. That was a principle that Einstein had and something we've measured actually.

   19. LFLex Fridman25:36

       So is, is it possible... I mean, so w- we'll talk about gravitational waves and it, in some sense there's, um, 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, a model why that signal should exist.

   20. BBBarry Barish26:03

       Right.

   21. LFLex Fridman26:03

       I mean, is it possible that aliens are communicating with us via gravity? Like, why not?

   22. BBBarry Barish26:10

       Well, i- i- why-

   23. LFLex Fridman26:12

       (laughing)

   24. BBBarry Barish26:12

       Yeah, it's true. Why not? Uh, for us, it's very hard to detect these gravitational effects that have to come from something pretty, that has a lot of gravity like black holes. But we're pretty primitive at, at this stage. Uh, there's, uh, very reputable physicists that look for a fifth force, one that we haven't found yet. Maybe it's the key. So, you know-

   25. LFLex Fridman26:40

       It should be.

   26. BBBarry Barish26:40

       ... it's possible.

   27. LFLex Fridman26:41

       What would that look like? What- what would a fifth force of physics look like, exactly?

   28. BBBarry Barish26:45

       Well usually they think it's probably a long-range for- longer range force than we have now. Um, but, uh, there are reputable phy- colleagues of mine that spend their life looking for a fifth force.

   29. LFLex Fridman26:58

       So longer range than gravity? Is it like-

   30. BBBarry Barish27:00

       Yeah. Yeah.
6. 27:26 – 44:08

   Gravity

   1. LFLex Fridman27:26

      speaking of gravita- uh, of gravity, uh, what are gravitational waves? Let's maybe start from the basics.

   2. BBBarry Barish27:34

      We learned gravity from Newton, right? You, you when you were young, you were told that if you jumped up, the Earth pulls you down. And when the apple falls out of the tree, the Earth pulls it down. And, um, 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. That was, uh, missing in Newton's theory. Uh, Newton's theory also... Newton recognized at least one of the two problem solves tell you, one of them is, there's more than those, but one 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? Uh, that's not explained by Newton even though he has a most successful theory of physics ever. Went 200 and some years with nobody ever seeing, uh, violation.

   3. LFLex Fridman28:35

      But he accurately describes the movement of an object falling down to Earth, but he's not answering why that, what's the act-

   4. BBBarry Barish28:41

      Yeah. Yeah. He, he-

   5. LFLex Fridman28:42

      ... 'cause it's a distance, right?

   6. BBBarry Barish28:43

      He gives a formula-

   7. LFLex Fridman28:44

      Right.

   8. BBBarry Barish28:44

      ... which e- which it's a product of the Earth's mass, the apple's mass inversely proportional to the square of the distance between.

   9. LFLex Fridman28:53

      Mm-hmm.

   10. BBBarry Barish28:53

       And then the strength he called capital G. The strength he couldn't determine, but it was determined 100 years later. But no one ever saw a violation to 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 s- wrong if you calculate it by Newton's theory. But, so, um, like most theories then in, in physics, you can have a wonderful one like Newton's theory. It isn't wrong, um, but you have to have a, 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 wa- which he released in 1915. He took 10 years to develop it even though in 1905, he solved three or four of the most important problems in physics in a matter of months, and then he spent 10 years on this problem before he, uh, let it out. And this is called general relativity, it's a new theory of gravity. 1915. And 1916, Einstein, um, wrote a little paper where he did not do some fancy derivation. Instead he did, um, what I would call, used his intuition which he was very good at too. Uh, and that is he noticed that if he form- 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, uh, have waves. Of course, that's light and electromagnetic rays, radio waves, everything else. So, he said, "If the formulas look similar, then gravity probably has waves too."

   11. LFLex Fridman31:08

       That's such a big leap, by the way. I mean, maybe you can correct me, but that just seems-

   12. BBBarry Barish31:13

       So that-

   13. LFLex Fridman31:13

       ... that seems like a heck of a leap.

   14. BBBarry Barish31:15

       Yeah, and so that, and it was considered to be a heck of a leap. So first, that paper was, except for this intuition, was, uh, poorly written, had, had a serious mistake. It had the fa- a factor of two wrong in the strength of gravity, which meant if we used those formulas, we would...

   15. LFLex Fridman31:34

       (laughs) .

   16. BBBarry Barish31:34

       And, uh-

   17. LFLex Fridman31:36

       Yeah.

   18. BBBarry Barish31:36

       ... two years later, he wrote a second paper, and in that paper, it turns out to be important for us because in that paper, he not only fixed his factor of two mistake, which he never admitted. He just wrote it, fixed it like he always did, and, and then he, uh, told us how you make gravitational waves, what, what makes gravitational waves. And you might recall, in electromagnetism, we make electromagnetic waves in a simple way. You take a plus charge, a minus charge, you oscillate like this, and that makes electromagnetic waves. And a physicist named Hertz made a receiver that could detect the waves and put it in the next room. He saw them and moved forward and backward and saw that it was wave-like. So, uh, Einstein said, "It won't be a dipole like that. It'll be a four-pole thing." And that's what it's called a quadrupole moment that gives the gravitational wave. So, he saw that again by insight, not by derivation. That set the table for which you need it to do, to do it. At the same time, in the same year, Schwarzschild, not Einstein said there were things like called black holes. So, it's interesting that that came the same-

   19. LFLex Fridman32:51

       So what year was that? So that was-

   20. BBBarry Barish32:54

       1915.

   21. LFLex Fridman32:55

       It, it was in parallel...

   22. BBBarry Barish32:57

       With-

   23. LFLex Fridman32:57

       Uh, d- did I, uh, I sh- I should probably know this, but did Einstein not have an intuition that there should be such things as black holes?

   24. BBBarry Barish33:04

       That came from Schwarzschild.

   25. LFLex Fridman33:05

       Oh, interesting.

   26. BBBarry Barish33:07

       Yeah. So, Schwarzschild, who was a, a, a German theoretical physicist, that he got killed in the war, I think, in the First World War a year, two years later or so. He's the one that proposed black holes, that there were black holes.

   27. LFLex Fridman33:22

       It feels like a natural conclusion of, uh, general relativity, no? Or is that, uh, not-

   28. BBBarry Barish33:29

       Uh.

   29. LFLex Fridman33:29

       ... if you-

   30. BBBarry Barish33:29

       Well, it may seem like it, but I don't know about a natural conclusion. It is a, it's a result of curved spacetime though.
7. 44:08 – 51:14

   Philosophical implications of general relativity

   1. LFLex Fridman44:08

      how much do you think about the philosophical implications of general relativity? Like that we're in spacetime and it can be bent by gravity. Like, is that just what it is? Are we, are we supposed to be okay with this? 'Cause like Newton, even Newton's a little weird, right? But that at least like makes sense. That's our physical world, you know, when an apple falls, it makes sense. But like the fact that entirety of the spacetime we're in can bend.

   2. BBBarry Barish44:43

      Well-

   3. LFLex Fridman44:43

      That's uh, that's a, I, I, that's really mind-blowing.

   4. BBBarry Barish44:47

      Well may, may, let me make you another analogy.

   5. LFLex Fridman44:49

      This is a therapy session for me at this point.

   6. BBBarry Barish44:51

      Yeah, right. Another analogy.

   7. LFLex Fridman44:53

      Thank you.

   8. BBBarry Barish44:53

      So, so imagine you have a trampoline.

   9. LFLex Fridman44:56

      Yes.

   10. BBBarry Barish44:57

       Okay. What happens if you put a marble on a trampoline? Doesn't do anything, right?

   11. LFLex Fridman45:03

       No.

   12. BBBarry Barish45:03

       Just sits there.

   13. LFLex Fridman45:04

       Moves it a little bit, but not much.

   14. BBBarry Barish45:05

       Yeah. I mean, just if I drop it, it's not going to go anywhere. Now imagine I put a bowling ball at the center of the trampoline. Now I come up to the trampoline and I put a marble on. What happens?

   15. LFLex Fridman45:19

       It'll roll towards the bowling ball.

   16. BBBarry Barish45:21

       Okay. All right. So what's happened is the presence of this massive object distorted the space that the trampoline did. This is the same thing that happens to the presence of the earth, the earth and the apple. The presence of the earth affects the space around it just like the, uh, bowling ball on the trampoline.

   17. LFLex Fridman45:44

       Yeah. This doesn't make me feel better. I'm referring from the perspective of an ant walking around on that trampoline. Then some guy just dropped a ball, and then not only dropped the ball, right? It's not just dropping a bowling ball. It's making the b- the ball go up and down or doing some kind of oscillation thing, where it's like waves. And that's so fundamentally different from the experience on being on flat land and walking around and just finding delicious sweet things as ant does, and just, it just feels like to me from a human experience perspective completely, it's humbling. It's truly humbling.

   18. BBBarry Barish46:22

       It, it's humbling, but we see that kind of phenomenon all the time. Let, let me give you another example. Imagine that you walk up to a, a, a still pond.

   19. LFLex Fridman46:33

       Yes.

   20. BBBarry Barish46:33

       Okay? Now I throw, like you, you throw a rock in it, what happens?

   21. LFLex Fridman46:39

       Ripples.

   22. BBBarry Barish46:39

       The rock goes in, sinks to the bottom, fine. And these little ripples go out.

   23. LFLex Fridman46:43

       Yeah.

   24. BBBarry Barish46:44

       And they travel out.

   25. LFLex Fridman46:46

       Yeah.

   26. BBBarry Barish46:46

       That's exactly what happens. I mean there's a disturbance which is these say f- the bowling ball or our black holes, and then the ripples that go out in the water, they're not r- they don't have any m- they don't have the rock, any part, pieces of the rock.

   27. LFLex Fridman47:02

       But see the thing is, I guess what's not disturbing about that is it's a, I mean it's a, a guess a, a flat two-dimensional surface that's being disturbed. Like, for a three-dimensional surface, uh, three-dimensional space to be disturbed feels weird.

   28. BBBarry Barish47:20

       It's even worse. It's four-dimensional.

   29. LFLex Fridman47:21

       Four-dimensional.

   30. BBBarry Barish47:21

       Because it's space and time.
8. 51:14 – 54:28

   Detecting gravitational waves

   1. LFLex Fridman51:14

      So we're talking about a pretty weak signal here.

   2. BBBarry Barish51:17

      Yeah, that's why that method didn't work.

   3. LFLex Fridman51:19

      So what... Can you tell the story of figuring out what kind of method would be able to detect this very weak signal of gravitational waves?

   4. BBBarry Barish51:30

      So remembering the, remembering what happens in, when you go to the amusement park-

   5. LFLex Fridman51:36

      Yeah.

   6. BBBarry Barish51:37

      ... that it's going to do something like stretch this way and squash that way, squash this way, and stretch this way. We do have an instrument that can detect that kind of thing. It's called an interferometer. And what it does is it just basically takes usually light, and the two directions that we're talking about, you send light down one direction and the perpendicular direction. And if nothing changes, it takes the same... and the arms are the same length, it just goes down, bounces back. And if you invert one compared to the other, they cancel. So there's nothing happens. But if it's like the amusement park and one of the arms got, you know, it got shorter and fatter, so it got... took longer to go horizontally than it did to go vertically. Then when they come back, when the, when the light comes back, it comes back somewhat out of time. And that basically is the scheme. The only problem is that that's not a very... done very accurately in general. And we had to do it extremely accurately.

   7. LFLex Fridman52:46

      So what, uh, what- what's the, what's the difficulty of, uh, doing so accurately?

   8. BBBarry Barish52:52

      Okay. So the measurement that we have to do is a distortion in time. How big is it? One, it's a distortion that's one part in 10 to the 21. That's 21 zeros and a one. Okay?

   9. LFLex Fridman53:08

      Wow. And this, so this is like a delay in the thing coming back.

   10. BBBarry Barish53:13

       Uh, it's a, one of them coming back after the other one, but the difference is just one part in 10 to the 21.

   11. LFLex Fridman53:19

       Wow.

   12. BBBarry Barish53:20

       So for that reason, we make it big. Let it, let the arms be long. Okay? So one part in 10 to the 21. In our case, it's kilometers long. So we have an instrument that's kilometers in one direction, kilometers in the other. So four, four-

   13. LFLex Fridman53:35

       How many kilometers are we talking about? Four kilometers?

   14. BBBarry Barish53:37

       Four kilometers in each direction. Um, if you take then one part in 10 to the 21, we're talking about measuring something to 10 to the minus 18 meters.

   15. LFLex Fridman53:53

       (laughs) . Okay. This is good.

   16. BBBarry Barish53:55

       Now to tell you how small that is-

   17. LFLex Fridman53:57

       Yeah.

   18. BBBarry Barish53:58

       ... the proton-

   19. LFLex Fridman53:59

       Yeah.

   20. BBBarry Barish54:00

       ... thing we're made of this you can't go and grab so easily is 10 to the minus 15 meters.

   21. LFLex Fridman54:05

       Okay.

   22. BBBarry Barish54:05

       So this is 1/1000 the size of a proton. That's the effect, size of the effect. Einstein himself didn't think this could be measured and ever seen. Actually, he said that. Uh, but that's because he didn't, you know, anticipate modern lasers and, and techniques that we developed.

   23. LFLex Fridman54:27

       Okay.

9. 54:28 – 1:27:25

   LIGO

   1. LFLex Fridman54:28

      So maybe can you tell me a little bit what you're referring to as LIGO, the Laser Interferometer Gravitational Wave Observatory? What is LIGO? Can you just elaborate kind of the big picture view here before I ask you specific questions about it?

   2. BBBarry Barish54:44

      (laughs) Yeah. So in the same idea that I just said, we have two long vacuum pipes, 10 to the, uh, 4 kilometers long. Okay. Uh, we start with a laser beam and we divide the beam-... going down the two arms, y- and we have a mirror at the other end, reflects it back. It's more subtle, but we s- bring it back. If there's no distortion in spacetime and the lengths are exactly the same, which we calibrate them to be, then when it comes back, if we just invert one signal compared to the other, they'll just cancel.

   3. LFLex Fridman55:22

      Mm-hmm.

   4. BBBarry Barish55:22

      So we see nothing. Okay? But if one arm got a little bit longer than the other, then they don't come back at exactly the same time, they don't exactly cancel, that's what we measure. So to give a number to it, we have to do that to, we have w- the change of length to be able to do this 10 to the -18 meters, to one part in 10 to the 12th, and that was the big experimental challenge that, uh, uh, required a lot of innovation to be able to do.

   5. LFLex Fridman55:57

      So w- what... y- you gave a lot of credit to, I think, Caltech and MIT for some of the technical developments like within this project. Is there some interesting things you can speak to, like at the low level of some cool stuff that had to be solved? Like what are, what are we talking-

   6. BBBarry Barish56:13

      Yeah. Yeah. Yeah. So-

   7. LFLex Fridman56:14

      I'm a software engineer, so-

   8. BBBarry Barish56:15

      Okay.

   9. LFLex Fridman56:16

      ... all of this-

   10. BBBarry Barish56:16

       Well, well-

   11. LFLex Fridman56:16

       I have so much more respect for everything done here than anything I've ever done.

   12. BBBarry Barish56:20

       Okay.

   13. LFLex Fridman56:20

       So it's just code when I use it.

   14. BBBarry Barish56:22

       So, so, so I'll give you an example of doing, uh, uh, mechanical engineering-

   15. LFLex Fridman56:30

       Mm-hmm.

   16. BBBarry Barish56:31

       ... at a better l- at a, at a... basically, mechanical engineering and geology-

   17. LFLex Fridman56:36

       Yeah.

   18. BBBarry Barish56:36

       ... at maybe at a level.

   19. LFLex Fridman56:38

       Geology. Okay. (laughs)

   20. BBBarry Barish56:38

       Uh, so what are we... what's the problem? The problem is the following, that I've given you this picture of an instrument that I, by some magic, I can make good enough to f- measure this very short distance.

   21. LFLex Fridman56:49

       Yeah.

   22. BBBarry Barish56:49

       But then, I put it down here, it won't work. And the reason it doesn't work is that the Earth itself is moving all over the place all the time. You don't realize-

   23. LFLex Fridman57:00

       Oh, no.

   24. BBBarry Barish57:00

       ... it. It seems pretty good to you.

   25. LFLex Fridman57:01

       Yeah. No, I get it.

   26. BBBarry Barish57:02

       But it's moving all the time. So somehow, it's moving so much that you... we can't deal with it. We happen to be trying to do the experiment here on Earth, but we can't deal with it. So, we have to make the instrument isolated from the Earth.

   27. LFLex Fridman57:17

       Oh, no.

   28. BBBarry Barish57:18

       At the frequencies we're at, we've got to float it. That's a mechanical, that's an engineering problem, not a physics problem.

   29. LFLex Fridman57:24

       So when you actually... like, uh, we're doing... we're having a conversation on our podcast right now, there's, uh... and people who record music work with this, you know, how to create an isolated room. (laughs) And they usually build a room within a room, but that's still not isolated. In fact, they say it's impossible to truly isolate from sound, uh, from noise and stuff like that. But that, that, th- that's like one step of millions that you took, is building a room inside a room, bec-... you basically have to isolate all-

   30. BBBarry Barish57:57

       No, this is actually an easier problem. It's just you have to do it really well. So the... making a clean room is really a tough problem, because you have to put a room inside a room-
10. 1:27:25 – 1:42:14

    Nobel Prize

    1. LFLex Fridman1:27:25

       So you, two other folks, and the entire team won the Nobel Prize for this-

    2. BBBarry Barish1:27:34

       Yeah.

    3. LFLex Fridman1:27:34

       ... big effort. There's a million questions I can ask for, but looking back, where does the Nobel Prize fit into all of this? You know, if you think hundreds of years from now, I venture to say that people will not remember the winners of a prize, but they'll remember creations like these. Maybe I'm romanticizing engineering, but I guess I want to ask, how important is the Nobel Prize in all of this?

    4. BBBarry Barish1:28:12

       Um, well that's a, that's a complicated question. It, it, uh ... As a physicist, it's something you, if you're, if you're (laughs) trying to win a Nobel Prize, forget it, because they give, you know, one a year. So there's, uh, there's been 200 physicists who have won the Nobel Prize since 1900. And-

    5. LFLex Fridman1:28:33

       Yeah.

    6. BBBarry Barish1:28:34

       ... and so that's, you know, it's the aim. So things just have to fall right. So your goal cannot be to win a Nobel Prize. It wasn't my dream. Uh, it's, uh, it's, uh, tremendous for science. I mean, why the Nobel Prize for a guy that made dynamite and stuff is, you know, what it is-

    7. LFLex Fridman1:28:55

       Yeah.

    8. BBBarry Barish1:28:55

       ... is a long story, but it's the one day a year where actually the science that people have done is all over the world and so forth. Forget about the people again, you know? The, it, it is really good for, for science.

    9. LFLex Fridman1:29:08

       Celebrating science.

    10. BBBarry Barish1:29:10

        It celebrates science f- for, you know, several days, different fields. Uh, you know, chemistry, uh, medicine, and so forth. And, uh, everybody doesn't understand everything about these. They're generally fairly abstract. But then it's, you know, it's on the front page of newspapers around the world. So it's really good for science. It's not easy to get science on the front page of the New York Times. It's not there. Uh, should be, but it's not. And, uh, um, so the Nobel Prize is important in that way. Uh, it's, otherwise, you know, I have a certain celebrity that I didn't have before and, um ...

    11. LFLex Fridman1:29:50

        (laughs) And now you get to be a celebrity that advertises science. It's a mechanism to, uh, to remind us how incredible-

    12. BBBarry Barish1:29:59

        Well, it-

    13. LFLex Fridman1:30:00

        ... like (laughs) how much credit science deserves in everything we have.

    14. BBBarry Barish1:30:02

        Well, it, it, it has a little bit more. One thing I didn't expect, which is good, is that, you know, we have a, a government ... I, I'm not picking on ours necessarily, but it's true of all governments, are not run by scientists. In our case it's-

    15. LFLex Fridman1:30:20

        Yeah.

    16. BBBarry Barish1:30:20

        ... run by, uh, lawyers and businessmen.

    17. LFLex Fridman1:30:23

        Lawyers. Yep.

    18. BBBarry Barish1:30:23

        Okay? Uh, and at best they may have a, an aide or something that knows a little science. So, um, so our country is, and all countries are, hardly, um, t- hardly take into account science in making decisions.

    19. LFLex Fridman1:30:42

        Yes.

    20. BBBarry Barish1:30:43

        Okay? And, um, having a Nobel Prize, the, uh, people in those positions actually listen, so you have more influence. I don't care whether it's about global warming or what the issue is, there's some influence which is lacking otherwise. And, uh, I, people pay attention to what I say if I talk about global warming and they wouldn't have, uh, before I had the Nobel Prize.

Episode duration: 2:22:55