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Speaker 1

00:00

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 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.

Speaker 1

00:56

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? And he couldn't answer.

Speaker 1

01:19

And this was very surprising to you. So you went on to learn why. Maybe you can speak to what are some early questions in math and physics that really sparked your curiosity?

Speaker 2

01:31

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.

Speaker 2

02:09

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.

Speaker 1

02:47

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

Speaker 2

02:51

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.

Speaker 1

03:18

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

Speaker 2

03:21

Yeah, yeah. 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.

Speaker 2

03:35

Anyway, back to me and 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?

Speaker 2

04:00

And he couldn't answer it. And it may not have been the first question. It's the first 1 that I remember. And that was the first time that I realized that to learn and answer your own curiosity or questions, there's various mechanisms.

Speaker 2

04:17

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.

Speaker 1

04:46

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

Speaker 2

04:57

general? 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.

Speaker 2

05:19

What happened to this water that came down? And I didn't know that much. 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?

Speaker 1

05:37

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?

Speaker 2

06:03

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.

Speaker 2

06:21

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.

Speaker 2

06:38

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.

Speaker 1

06:55

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.

Speaker 2

07:26

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. Dark energy is a complete puzzle.

Speaker 2

07:48

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 big puzzle what it is.

Speaker 2

08:26

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.

Speaker 2

08:55

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

Speaker 1

09:03

do you think the answer could be something very complicated?

Speaker 2

09:08

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.

Speaker 2

09:35

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

Speaker 1

09:45

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?

Speaker 2

09:56

It's conceivable. 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.

Speaker 2

10:14

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.

Speaker 1

10:28

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

Speaker 1

10:50

Why is that? Can you speak to that?

Speaker 2

10:52

Sure. He was amazing, actually. 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.

Speaker 2

11:16

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.

Speaker 2

11:51

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. The basic ingredients were there. 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.

Speaker 2

12:19

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.

Speaker 2

13:07

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. People knew it was useful for medicine. But radioactive materials are hard to find, and so it wasn't prevalent.

Speaker 2

13:26

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 seemed impossible.

Speaker 2

14:21

They barely had been seen. 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.

Speaker 2

14:45

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.

Speaker 1

15:21

Forgive me for not knowing, but is the birth of the idea of bombarding neutrons, Is that an experimental idea? Was it born out of an experiment? He just observed something?

Speaker 1

15:35

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

Speaker 2

15:40

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.

Speaker 2

16:18

So, you know, it was pretty astounding.

Speaker 1

16:22

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

Speaker 2

16:38

It's difficult to do, yeah. 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.

Speaker 1

16:56

So you loved both sides of it, the theory and

Speaker 2

16:58

the experiment. 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.

Speaker 1

17:15

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.

Speaker 2

17:38

Yeah. 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.

Speaker 2

17:54

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. You're curious, you learn something. So it's a little bit like curiosity killed the cat.

Speaker 2

18:12

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. Yeah, And Fermi himself was a very apolitical person.

Speaker 2

18:37

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. But you asked if it's tragic. The bomb was tragic, certainly on Japan, and he had a role in that.

Speaker 2

19:03

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

Speaker 1

19:07

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.

Speaker 1

19:35

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.

Speaker 1

20:04

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.

Speaker 2

20:34

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.

Speaker 1

21:00

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.

Speaker 2

21:13

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

Speaker 2

21:20

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.

Speaker 1

21:39

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.

Speaker 2

22:01

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. And it didn't. And that it didn't, yeah.

Speaker 1

22:17

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?

Speaker 2

23:00

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? Which meant where are these other.

Speaker 2

23:21

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?

Speaker 2

23:58

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. Why are we so? Statistics say that communicating with us, I think that it's harder than people think.

Speaker 2

24:22

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. And we didn't even understand that.

Speaker 2

25:05

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? I don't know.

Speaker 2

25:28

Gravity seems to be also have the same speed. That was a principle that Einstein had, and something we've measured actually.

Speaker 1

25:36

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.

Speaker 1

25:57

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? Like, why not?

Speaker 2

26:10

Well, yeah, it's true, why not? 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.

Speaker 2

26:24

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. Maybe it's the key. So, you know, it's- What would

Speaker 1

26:41

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

Speaker 2

26:45

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.

Speaker 1

26:58

So longer range than gravity? Yeah. Super long.

Speaker 2

27:01

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. So it falls pretty fast.

Speaker 1

27:14

That's okay, so Now we have a theory of what consciousness is. It's just the fifth force of physics. Yeah, there we go.

Speaker 1

27:21

That's a good hypothesis. Speaking of gravity, What are gravitational waves? Let's maybe start from the basics.

Speaker 2

27:34

We learned gravity from Newton, right? 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.

Speaker 2

27:50

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

Speaker 2

28:13

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.

Speaker 1

28:34

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?

Speaker 2

28:42

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.

Speaker 2

29:33

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.

Speaker 2

30:05

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.

Speaker 2

30:45

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.

Speaker 1

31:08

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

Speaker 2

31:15

Yeah, and it was considered to be a heck of a leap. So first that paper was, except for this intuition, was poorly written, had a serious mistake. It had a factor of 2 wrong in the strength of gravity, which meant if we use those formulas, we would.

Speaker 2

31:34

And 2 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 2 mistake, which he never admitted, he just wrote it, fixed it like he always did. And then he told us how you make gravitational waves, what makes gravitational waves. And you might recall in electromagnetism, we make electromagnetic waves in a simple way.

Speaker 2

32:06

You take a plus charge and minus charge, you oscillate like this, and that makes an 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 Einstein said it won't be a dipole like that, it'll be a four-pole thing.

Speaker 2

32:29

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 what you needed to do to do it. At the same time, in the same year, Schwarzschild, not Einstein, said there were things called black holes.

Speaker 2

32:49

So it's interesting that that came the same.

Speaker 1

32:51

So what year was that? 1915. It was in parallel.

Speaker 1

32:58

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

Speaker 2

33:04

That came from Schwarzschild. Oh, interesting. Yeah, so Schwarzschild, who was a German theoretical physicist, he got killed in the war, I think, in the First World War, 2 years later or so.

Speaker 2

33:19

He's the 1 that proposed black holes, that there were black holes.

Speaker 1

33:22

It feels like a natural conclusion of general relativity, no, or is that

Speaker 2

33:28

not? Well, it may seem like it, but I don't know about a natural conclusion. It's a result of curved space-time, though.

Speaker 1

33:36

Right, but it's such a weird result that you might have to, it's a special.

Speaker 2

33:41

Yeah, it's a special case. Yeah. So, I don't know.

Speaker 2

33:46

Anyway, Einstein then, an interesting part of the story is that Einstein then left the problem. Most physicists, because it really wasn't derived, he just didn't pick up on it or general relativity much, because quantum mechanics became the thing in physics. Einstein only picked up this problem again after he immigrated to the US. He came to the US in 1932.

Speaker 2

34:15

I think in 1934 or 5, he was working with another physicist called Rosen, who he did several important works with. And they revisited the question. And they had a problem that most of us as students always had that studied general relativity. General relativity is really hard because it's four-dimensional instead of three-dimensional.

Speaker 2

34:39

And if you don't set it up right, you get infinities, which don't belong there. We call them coordinate singularities as a name. But if you get these infinities, you don't get the answers you want. And he was trying to derive now general relativity from general relativity, gravitational waves.

Speaker 2

35:00

And in doing it, he kept getting these infinities. And so, he wrote a paper with Rosen that he submitted to our most important journal, Physical Review Letters. And that when it was submitted to Physical Review Letters, it was entitled, Do Gravitational Waves Exist? A very funny title to write 20 years after he proposed they exist.

Speaker 2

35:26

But it's because he had found these singularities, these infinities. And so, the editor at that time, and part of it that I don't know, is peer review. We live and die by peer review as scientists send our stuff out. We don't know when peer review actually started or what peer review Einstein ever experienced before this time, but the editor of Physical Review sent this out for review.

Speaker 2

35:58

He had a choice. He could take any article and just accept it. He can reject it or he can send it for review.

Speaker 1

36:05

Right, I believe the editors used to have much more power.

Speaker 2

36:08

Yeah, yeah. And he was a young man, his name was Tate. And he ended up being editor for years.

Speaker 2

36:15

So he sent this for review to a theoretical physicist named Robertson who was also in this field of general relativity who happened to be on sabbatical at that moment at Caltech. Otherwise, his institution was Princeton where Einstein was. And he saw that the way they set up the problem, the infinities were like I make it as a student, because if you don't set it up right in general relativity, you get these infinities. And so he reviewed the article and gave an illustration that if they set it up on what are called cylindrical coordinates, these infinities went away.

Speaker 2

36:57

The editor of Physical Review was obviously intimidated by Einstein. He wrote this really not a letter back like I would get saying you're screwed up in your paper. Instead, it was kind of, what do you think of the comments of our referee? Einstein wrote back, it's a well-documented letter, wrote back a letter to Physical Review saying, I didn't send you the paper to send it to 1 of your so-called experts, I sent it to you to publish.

Speaker 2

37:30

I withdraw the paper. And He never published again in that journal. That was 1936. Instead, he rewrote it with the fixes that were made, changed the title, and published it in what was called the Franklin Review which is the Franklin Institute in Philadelphia, which is Benjamin Franklin Institute, which doesn't have a journal now, but did at that time.

Speaker 2

38:00

So the article is published. It's the last time he ever wrote about it. It remained controversial. So it wasn't until close to 1960, 1958, where there was a conference that brought together the experts in general relativity to try to sort out whether there was, whether it was true that there were gravitational waves or not.

Speaker 2

38:30

And there was a very nice derivation by a British theorist from the heart of the theory that gets gravitational waves. And that was number 1. The second thing that happened at that meeting is Richard Feynman was there, and Feynman said, well, if there's, typical Feynman, if there's gravitational waves, they need to be able to do something, otherwise they don't exist. So they have to be able to transfer energy.

Speaker 2

39:00

So he made a idea of a Gedanken experiment that is just a bar with a couple of rings on it. And then if a gravitational wave goes through it, distorts the bar. And that creates friction on these little rings. And that's heat and that's energy.

Speaker 2

39:19

So that meant- Is

Speaker 1

39:20

that a good idea? That sounds like a good idea.

Speaker 2

39:22

Yeah, it means that he showed that with the distortion of space-time, you could transfer energy just by this little idea. And it was shown theoretically. So at that point, it was believed theoretically then by people that gravitational waves should exist.

Speaker 1

39:43

No, we should be able to detect them. We

Speaker 2

39:45

should be able to detect them, except that they're very, very small.

Speaker 1

39:50

And so what kind of, there's a bunch of questions here, but what kind of events would generate gravitational waves?

Speaker 2

39:58

You have to have this, what I call quadrupole moment. That comes about if I have, for example, 2 objects that go around each other like this like the Earth around the Sun or the Moon around the Earth, or in our case, it turns out to be 2 black holes going around each other like this.

Speaker 1

40:17

So how's that different than basic oscillation back and forth? Is it just more common in nature to have?

Speaker 2

40:22

Oscillation is a dipole moment. So it

Speaker 1

40:24

has to be in 3 dimensional space in a kind of oscillation.

Speaker 2

40:26

So you have to have something that's 3 dimensional that'll give what I call a quadrupole moment that's just built into this.

Speaker 1

40:32

And luckily in nature you have stuff.

Speaker 2

40:35

And luckily things exist. And it is luckily because the effect is so small that you could say, look, I can take a barbell and spin it, right? And detect the gravitational waves.

Speaker 2

40:49

But unfortunately, no matter how much I spin it, how fast I

Speaker 1

40:53

spin it,

Speaker 2

40:54

so I know how to make gravitational waves, but they're so weak, I can't detect them. So we have to take something that's stronger than I can make. Otherwise, we would do what Hertz did for electromagnetic waves.

Speaker 2

41:05

Go in our lab, take a barbell, put it on something, spin it.

Speaker 1

41:08

Can I ask a dumb question? So a single object that's weirdly shaped, does that generate gravitational waves? So if it's rotating?

Speaker 1

41:18

Sure. But it's just much weaker signal.

Speaker 2

41:22

It's weaker, well, we didn't know what the strongest signal would be that we would see. We targeted seeing something called neutron stars, actually, because black holes, we don't know very much about. It turned out we were a little bit lucky.

Speaker 2

41:34

There was a stronger source, which was the black holes.

Speaker 1

41:38

Well, another ridiculous question. So you say waves. What does a wave mean?

Speaker 1

41:46

Like The most ridiculous version of that question is, what does it feel like to ride a wave as you get closer to the source? Or experience it?

Speaker 2

41:57

Well, if you experience a wave, Imagine that this is what happens to you. I don't know what you mean by getting close. It comes to you.

Speaker 2

42:06

So, it's like this light wave or something that comes through you. So, when the light hits you, it makes your eyes detect it. I flashed it. What does this do?

Speaker 2

42:17

It's like going to the amusement park and they have these mirrors. You look in this mirror and you look short and fat and the 1 next to you makes you tall and thin. Okay, imagine that you went back and forth between those 2 mirrors once a second. That would be a gravitational wave with a period of once a second.

Speaker 2

42:37

If you did it 60 times a second, go back and forth, and then that's all that happens. It makes you taller and shorter and fatter back and forth as it goes through you at the frequency of the gravitational wave. So the frequencies that we detect are higher than 1 a second, but that's the idea. So, and the amount is small.

Speaker 1

42:59

Amount is small, but if you're closer to the source of the wave, is it the same amount?

Speaker 2

43:08

Yeah, it doesn't dissipate.

Speaker 1

43:10

It doesn't dissipate. Okay, so it's not that fun of an amusement ride.

Speaker 2

43:16

Well, It does dissipate, but it doesn't, it's proportional to the distance.

Speaker 1

43:22

Right, it's not a-

Speaker 2

43:23

It's not a big power.

Speaker 1

43:24

Right, gotcha. So, but it would be a fun ride if you get a little bit closer, or a lot closer. I mean, like I wonder what the, okay, this is a ridiculous question, but I have you here.

Speaker 1

43:38

Like the getting fatter and taller, I mean, that experience, for some reason that's mind blowing to me because it brings the distortion of space-time to you. I mean, space-time is being morphed, right? Like this is a way. That's right.

Speaker 1

43:57

That, how, that's so weird.

Speaker 2

43:59

And We're in space, so

Speaker 1

44:01

we're affected by it. Yeah, we're in space and now it's moving. I don't know what to do with it.

Speaker 1

44:06

Okay, how much do you think about the philosophical implications of general relativity? Like that we're in space-time and it can be bent by gravity. Like, is that just what it is? Are we supposed to be okay with this?

Speaker 1

44:26

Because like Newton, even Newton is 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.

Speaker 1

44:36

But like the fact that entirety of the space-time we're in can bend. That's really mind-blowing.

Speaker 2

44:47

Let me make another analogy. This

Speaker 1

44:49

is a therapy session for me at

Speaker 2

44:51

this point. Yeah, right, another analogy. Thank you.

Speaker 2

44:53

So imagine you have a trampoline.

Speaker 1

44:56

Yes.

Speaker 2

44:56

Okay. What happens if you put a marble on a trampoline? Doesn't do anything, right? No.

Speaker 2

45:03

Maybe a little

Speaker 1

45:04

bit, but not much.

Speaker 2

45:05

Yeah, I mean, just if I drop it, it's not gonna 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?

Speaker 1

45:19

They'll roll towards the bowling ball.

Speaker 2

45:21

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 bowling ball on the trampoline.

Speaker 1

45:43

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 not only dropped a ball, right, it's not just dropping a bowling ball, it's making 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.