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 three thousand

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? And he couldn't answer. 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? 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, eight 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 teach it in college level and it's, to me, one 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 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. Yeah, that, to me, needs to be solved really in education and in homes. It's a 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 in curiosity, I was a pest and asked a lot of questions. My

father generally could answer them at that age. And the first one 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 he couldn't answer it. And it may not have been the first question. It's the

first one 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. In this case, it was going to a

librarian 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 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 remembered that I was curious why what happens to water,

you know, 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 I, you know, I didn't know that much. And then eventually

I learned in chemistry or something and water is made out of hydrogen and oxygen. Those are both

gases. So how the heck does it make this substances liquid?

Yeah, but 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's looks and is in awe and is curious about what it

is out there. And, 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 the more we look. So of course, I think that's one of the

areas that 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 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. Yeah. 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. Yeah, you know,

fill you with all. Well, first, I'm a physicist, not an astronomer. So I'm interested in physical

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

won't talk about our recent our recent there in the last 20, 30 years for certainly dark energy.

Dark energy is that complete puzzle. It goes against what I will 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 what he called a constant, which isn't and and in the 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 on particle accelerators and so forth. And it's a big puzzle

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

something called supersymmetry. And 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 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? 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 not doesn't seem the most likely that they're 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 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 yeah. 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.

Why is that? Can you speak to that? 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. And he did two 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 till 1932. And then once we discovered that there

was a neutron and proton and they made the nucleus and then their 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.

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 one. 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. People knew it was useful for medicine.

But radioactive materials are 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 aluminum or something with alpha

particles and find that they excited something that decayed and gave, 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. And 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.

Seemed impossible. 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. And he did this two completely different things, an experiment that

was a great idea and 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 followed soon after that.

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

is that an experimental idea? Was it born out of an experiment? He just observed something?

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 Julio 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. So it was pretty astounding.

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?

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

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 love both sides of it, the theory.

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 going to 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 one 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.

You know, you're curious, you learn something.

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

keep it under control.

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.

But he asked if it's tragic that 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 that curiosity that in sort of my area of artificial intelligence, that's been a concern.

They're 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 popular,

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, you know, engineer viruses to protect us from viruses,

to see, you know, how close is this to mutating so it can jump to humans, or going, you know,

or engineering defenses against those.

And it seems exciting in 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.

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, both having observed what he observed.

We didn't write much. I mean, he died young.

He died soon after the World War.

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

rising tensions between the Soviet Union and the U.S. and look like an endless thing.

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

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, like 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 and that it didn't.

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,

with Fermi, it's a very interesting question, which is if 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 one of the fathers of the atomic bomb.

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

Which meant, where are these other?

And then he did some numerology where he calculated what they knew about how many

galaxies there are and how many stars and how many planets then 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,

there's the statistics are so high that how can we be singular and separate?

That's 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, so the 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, we don't think anything can go faster in 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 tried 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

would mean we could communicate with each other.

And I think, and we didn't even understand that.

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, 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.

So is it possible?

I mean, so we'll talk about gravitational waves.

And it, in some sense, there's a, 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?

Like why not?

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.

But we're pretty primitive at this stage.

There's a very reputable physicists that look for a fifth force,

one that we haven't found yet.

Maybe it's the key.

What would that look like?

What would a fifth force of physics look like exactly?

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

But they're reputable for colleagues of mine that spend their life looking for a fifth force.

So longer range than gravity?

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

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

So it falls pretty fast.

That's okay.

So now we have a theory of what consciousness is.

It's just the fifth force of physics.

There we go.

That's a good hypothesis.

Speaking of gravity, what are gravitational waves?

Let's maybe start from the basics.

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.

And 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 a missing in Newton's theory.

Newton's theory also, Newton recognized at least one of the two problems I'll 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?

That's not explained by Newton.

Even though he has the most successful theory of physics ever,

went 200 in some years with nobody ever seeing violation.

But he actually describes the movement of an object falling down to earth,

but he's not answering why that, because it's a distance.

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 one 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 one 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 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 let it out.

And this is called general relativity.

It's a new theory of gravity.

In 1915 and 1916, Einstein wrote a little paper where he did not do some fancy derivation.

Instead, he did, what I would call it, 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 rays, radio waves, everything else.

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

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.

Yeah, and it was considered to be a heck of a leap.

So first, that paper, except for this intuition, was poorly written, had a serious mistake.

It had a factor of two wrong in the strength of gravity, which meant, if we use those formulas,

we would, and 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 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.

You take a plus charge and 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 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 waves.

So he saw that again by insight, not by derivation.

That's at the table for which he needed 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.

So what year was that?

1915.

It was in parallel.

I should probably know this, but did Einstein not have any intuition that there should be

such things as black holes?

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, two years later or so.

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

It feels like a natural conclusion of general relativity, no?

Or is that 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.

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

Yeah.

It's a special case.

Yeah.

So, I don't know, 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 made this, didn't pick up

on it, or general relativity much, because quantum mechanics became the thing in physics.

And Einstein only picked up this problem again after he immigrated to the US.

So he came to the US in 1932.

And I think in 1934 or five, 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.

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.

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.

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 and 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.

He had a choice.

He could take any article and just accept it.

He could reject it or he could send it for review.

Right.

I believe the editors used to have much more power.

Yeah.

Yeah.

And he was a young man.

His name was Tate.

And he ended up being editor for years.

But 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 in what

are called cylindrical coordinates, these infinities went away.

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.

And 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 one of your so called experts, I sent

it to you to publish.

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.

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 it was true that there were

gravitational waves or not.

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 one.

The second thing that happened at that meeting is Richard Feynman was there.

And Feynman said, well, if there's a 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.

So he made an idea of a Gadankan 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.

So that meant...

Is that a good idea?

That sounds like a good idea.

Yeah.

But 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.

No, we should be able to detect them.

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

So there's a bunch of questions here, but what kind of events would generate gravitational

waves?

You have to have this what I call quadrupole moment.

That comes about if I have, for example, two 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 two black holes going around each other like this.

So how's that different than basic oscillation back and forth?

Is it just more common in nature to have...

Oscillation is a dipole moment.

So it has to be in three dimensional space kind of oscillation.

So you have to have something that's three dimensional that'll give what I call a quadrupole

moment.

That's just built into this.

And luckily in nature, you have stuff out.

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 and detect the gravitational waves.

But unfortunately, no matter how fast I spin it, 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, go in our lab, take

a barbell, put it on something, spin it.

Can I ask a dumb question?

So a single object that's weirdly shaped, does that generate gravitational waves?

So if it's rotating?

Sure.

But it's just much weaker signal.

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 there was a stronger source, which was the black

holes.

Well, another ridiculous question.

So you say waves, what does a wave mean?

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?

Well, if you experience a wave, imagine that this is what happens to you.

I don't know what you mean about getting close, it comes to you.

So it's like this light wave or something that comes through you.

So when the light hits you, it makes your eyes detected.

I flashed it.

What does this do?

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 one next to you makes you

tall and thin.

Imagine that you went back and forth between those two mirrors once a second.

That would be a gravitational wave with a period of once a second.

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 one a second, but that's the idea.

And the amount is small.

Not the small, but if you're closer to the source of the wave, is it the same amount?

Yeah, it doesn't dissipate.

It doesn't dissipate.

Okay, so it's not that fun of an amusement ride.

Well, it does dissipate, but it's proportional to the distance.

It's not a big power, or something.

Gotcha.

But it would be a fun ride if you get a little bit closer, or a lot closer.

I wonder what the, okay, this is a ridiculous question, but I have you here.

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?

This is a wave that's so weird.

And we're in space.

Yeah, we're in space, and now it's moving.

I don't know what to do with the, I mean, does it, 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?

Because Newton, even Newton is a little weird, right?

But that at least makes sense.

That's our physical world, you know, when an apple falls, it makes sense.

But like the fact that entirety of the space time we're in can bend, that's really mind

blowing.

Well, let me make another analogy.

This is a therapy session for me at this point.

Yeah, right, another analogy.

Thank you.

So imagine you have a trampoline.

Yes.

Okay.

What happens if you put a marble on a trampoline?

Doesn't do anything, right?

No.

Maybe a little bit, but not much.

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?

You know, roll towards the bowling ball.

Okay.

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.

Yeah.

This doesn't make me feel better.

If I'm 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.

And it just feels like to me from a human experience perspective, completely, it's humbling.

It's truly humbling.

It's humbling, but we see that kind of phenomenon all the time.

Let me give you another example.

Imagine that you walk up to a still pond.

Yes.

Okay.

Now I throw, you like to throw a rock in it.

What happens?

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

And they travel out.

That's exactly what happens.

I mean, there's a disturbance, which is the safe, the bowling ball or our black holes.

And then the ripples, they go out in the water, they're not, they don't have any, they don't

have the rock, any part, pieces of the rock.

The thing is, I guess, what's not disturbing about that is it's a, I mean, I guess a flat

two dimensional surface that's being disturbed, like for a three dimensional surface, a three

dimensional space to be disturbed feels weird.

It's even worse.

It's four dimensional because it's space and time.

So that's why you need Einstein is to make it four dimensional.

To make it four dimensional.

Yeah.

To take the same phenomenon and look at it in all of space and time.

Anyway, luckily for you and I and all of us, the amount of distortion is incredibly small.

So it turns out that if you think of space itself, now this is going to blow your mind

too.

If you think of space as being like a material, like this table, it's very stiff.

We have materials that are very pliable, materials that are very stiff.

So space itself is very stiff.

So when gravitational waves come through it, luckily for us, it doesn't distort it so

much that it affects our ordinary life very much.

No, I mean, that's great.

That's great.

I thought there was something bad coming.

No, this is great.

That's great news.

And so, I mean, that, I mean, perhaps we evolved as a life on earth to be such that for us,

this particular set of effects of gravitational waves is not that significant, maybe.

Maybe.

That's why.

You probably used this effect today or yesterday.

So it's pervasive.

Well, you mean gravity or the way, the external, because I only curvature of space and time.

Curvature of space.

How?

I only care personally as a human, right?

The gravity of earth.

But you use it every day almost.

Oh, it's curving.

No, no, no, it's in this thing.

Every time it tells you where you are, how does it tell you where you are?

It tells you where you are because we have 24 satellites or some number that are going

around in space and it asks how long it takes the beam to go to the satellite and come back

the signal to different ones and then it triangulates and tells you where you are.

And then if you go down the road, it tells you where you are.

Do you know that if you did that with the satellites and you didn't use Einstein's equations?

Oh, no.

You won't get the right answer.

That's right.

And in fact, if you take a road that's, say, 10 meters wide, I've done these numbers and

you ask how long you'd stay on the road if you didn't make the correction for general

relativity, this thing you're poo pooing, because you're using every day, you'd go off

the road.

You'd go off the road.

Well, actually, that might be my problem.

So you use it.

Well, I think I'm using an Andreas and the GPS doesn't work that well, so maybe I'm

using Newton's physics, so I need to upgrade to general relativity.

So the gravitation waves in Einstein had, wait, Feynman really does have a part in the

story?

Yeah.

Was that one of the first kind of experimental proposed, the tech gravitation waves?

Well, he did what we call a Godonkin experiment.

That's a thought experiment.

Yes.

Okay.

Not a real experiment.

Well, after that, then people believe gravitation waves must exist.

You can kind of calculate how big they are, they're tiny, and so people started searching.

The first idea that was used was Feynman's idea, and then, oh, very end of it, and it

was to take a great big, huge bar of aluminum and then put around, and it's made like a

cylinder and then put around it some very, very sensitive detectors so that if a gravitational

wave happened to go through it, it would go, and you detect this extra strain that was

there.

And that was this method that was used until we came along.

It wasn't a very good method to use.

And what was the, so we're talking about a pretty weak signal here.

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

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?

So remembering the, remembering what happens when you go to the amusement park, 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 shorter and fatter.

So it took longer to go horizontally than it did to go vertically.

Then when they come back, when the light comes back, that comes back somewhat out of time.

And that basically is the scheme.

The only problem is that that's not done very accurately in general.

And we had to do it extremely accurately.

So what's the difficulty of doing so accurately?

Okay.

So the measurement that we have to do is a distortion in time.

How big is it?

It's a distortion.

That's one part in 10 to the 21.

That's 21 zeros and a one.

Okay.

So this is like a delay in the thing coming back?

It's one of them coming back after the other one, but the difference is just one part in

10 to the 21.

So for that reason, we make it big.

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 instruments of kilometers in one direction, kilometers in the other.

How many kilometers?

We're talking about four kilometers.

Four kilometers in each direction.

If you take then one part in 10 to the 21, we're talking about measuring something to

10 to the minus 18 meters.

Now, to tell you how small that is, the proton thing we're made of, which you can't go and

grab so easily, is 10 to the minus 15 meters.

So this is one 1,000th the size of a proton.

That's the size of the effect.

Einstein himself didn't think this could be measured, ever seen actually.

He said that.

But that's because he didn't anticipate modern lasers and techniques that we developed.

Okay.

So maybe can you tell me a little bit what you're referring to as LIGO, the laser interferometer

or 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?

Yeah.

So in the same idea that I just said, we have two long vacuum pipes, four kilometers long.

We start with a laser beam and we divide the beam going down the two arms and we have a

mirror at the other end, reflects it back.

It's more subtle, but we bring it back.

If there's no distortion in space time 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.

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 the change of length to be able

to do this 10 to the minus 18 meters to one part in 10 to the 12th.

And that was the big experimental challenge that required a lot of innovation to be able

to do.

What 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?

What do we talk?

I'm a software engineer.

So all of this, I have so much more respect for everything done here than anything I've

ever done.

So it's just code.

So I'll give you an example of doing mechanical engineering at a basically mechanical

engineering and geology and maybe at a level.

So what do we, what's the problem?

The problem is the following that I've given you this picture of an instrument that by

some magic, I can make good enough to measure this very short distance.

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 that it seems pretty good to you, but it's moving all the time.

So somehow it's moving so much that 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.

Oh no.

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.

So when you actually like we're doing, we're having a conversation on our podcast right

now, there's, and people who record music work with this, how to create an isolated

room 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, from noise and stuff like

that.

But that's like one step of millions that you took as building a room inside a room.

You basically have to isolate all.

This is actually an easier problem.

You just 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.

Yeah.

So this is this is really simple engineering or physics.

Uh huh.

Okay.

So what do you have to do?

How do you isolate yourself from the, from the earth?

Yes.

First, we work at, we're not looking at all frequencies for gravitational waves.

We're looking at particular frequencies that you can deal with here on earth.

So what are frequencies with those be?

You were just talking about frequencies.

I mean, I don't know.

We know by evolution, our bodies know it's the audio band.

Okay.

The reason our ears work where they work is that's where the earth isn't going, making

too much noise.

Okay.

So the reason our ears work the way they work is because this is where it's quiet.

That's right.

So if you go to, if you go to one Hertz instead of 10 Hertz, it's the earth is really moving

around.

So, so somehow we live in a, what we call the audio band, it's tens of Hertz to thousands

of Hertz.

That's where we live.

That's where we live.

Okay.

If we're going to do an experiment on the earth, it might as well do it.

It's the same frequency.

That's where the earth is the quietest.

So we have to work in that frequency.

So we're not looking at all frequencies, okay?

So the solution for the, for the shaking of the earth to get rid of it is pretty mundane.

If we do the same thing that you do to make your car drive smoothly down the road.

So what happens when your car goes over a bump?

Early cars did that.

They bounced.

Right.

Okay.

But you don't feel that in your car.

So what happened to that energy?

You can't just disappear energy.

So we have these things called shock absorbers in the car.

What they do is they absorb, they take the, the thing that went like that and they basically

can't get rid of the energy, but they move it to very, very low frequency.

So what you feel isn't, you feel like, oh, smoothly.

Okay.

All right.

So we also work at this frequency.

So if we, so we basically why, why do we have to do anything other than shock absorbers?

So we made the world's fanciest shock absorbers, okay?

Not just like in your car where there's one layer of them, they're just the right squishiness

and so forth.

They're better than what's in the cars.

And we have four layers of it.

So whatever shakes and gets through the first layer, we treat it in a second, third or fourth

layer.

So some mechanical engineering problem.

Yeah.

So there's not, there's no weird tricks to it, like a, like a chemistry type thing or

no, no.

Just while the right squishiness, you know, I need the right material inside and ours

looks like little springs, but they're springs.

There's springs.

So like legitimately like shock absorbers.

Yeah.

What?

Okay.

Okay.

And this is now experimental physics at the edits limit.

Okay.

So you do this and we make the world's fanciest shock absorbers.

Just mechanical engineering.

Just mechanical engineering.

This is hilarious.

But we didn't just, we weren't good enough to discover gravitational waves.

So, so we did another, we added another feature and it's something else that you're aware

of probably have one and that is to get rid of noise.

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

in these little Bose earphones.

Noise canceling.

Noise canceling.

So, so how do they work?

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

and cancel it because it's just the same over and over again.

They cancel it.

And when the stewardess comes and asks you whether you want coffee or a tea or a drink

or something, you hear her fine because she's not ambient.

She's the signal.

So are we talking about active canceling?

I think we're actually.

Active canceling.

So.

This is, okay.

So another.

Don't tell me you have active canceling on this besides the shock absorbers.

Yeah.

So we had this.

So inside this array of shock absorbers, we, you asked for some interesting.

This is awesome.

So inside this, it's harder than the, the earphone problem, but it's just engineering.

We have to see measure not just that the engine still made noise, but the earth is shaking.

It's moving in some direction.

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

it's from.

So we put this array of seismometers inside this array of shock absorbers and measure the

residual motion and its direction, and we put little actuators that push back against

it and cancel it.

That's just awesome.

So you have the actuators and you have the thing that is sensing the vibrations and

then you have the actual actuators that adjust for that and do so in perfect synchrony.

Yeah.

What if it all works right?

And so how much do we reduce the shaking of the earth?

I mean, one part in 10 to the 12th.

One part in 10, what gets through us is one part in 10 to the 12th.

That's pretty big reduction.

You don't need that in your car, but that's what we do.

And so that's how isolated we are from the earth.

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

the interferometer.

Can I ask you a weird question here?

We make it very poetically and humorously, just saying it's just a mechanical engineering

problem.

But is this one of the biggest precision mechanical engineering efforts ever?

I mean, this seems exceptionally difficult.

It is.

And so it took a long time, and I think nobody seems to challenge the statement that this

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

I wonder what listening to Led Zeppelin sounds on this thing, because it's so isolated.

I mean, this is like, I don't know.

No background.

No background.

Wow.

Wow.

Wow.

So when you were first conceiving this, I would probably, if I was knowledgeable enough,

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

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

Did you believe this is possible?

I did.

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

When we started, we did just passive, but we were doing the tests to develop the active

to add as a second stage, which we ended up needing.

But there was a lot of, you know, now there was a lot of skepticism, a lot of us, especially

astronomers, felt that money was being wasted, as we were also expensive doing what I told

you is not cheap.

So it was kind of controversial, it was funded by the National Science Foundation.

Can you just link on this just for a little longer, the actuator thing, the active cancelling?

Do you remember, like, little experiments that were done along the way to prove to the team

themselves that this is even possible?

So from our, because I work with quite a bit of robots, and to me, the idea that you could

do it this precisely is a humbling and embarrassing, frankly, because, like, this is another level

of precision that I can't even, because robots are a mess.

And this is basically one of the most precise robots ever, right?

So like, can you, is there, do you have any, like, small scale experiments that were done

that just, you know, this is possible?

Yeah.

And larger scale.

We made, we made a test, that also has to be in vacuum tube, but we made test chambers

that had this system in it, our first mock of this system, so we could test it and optimize

it and make it work.

But it's just a mechanical engineering problem.

Okay, humans are just ape descendants, I got you, I got you.

Is there any video of this, like, some kind of educational purpose visualizations of this

active cancelling?

I don't think so, I mean, does this live on?

Well, we work, for parts of it, for the active cancelling, we worked with, for the instruments,

for the sensor and instruments, we worked with a small company near where you are, because

it was RMIT people that got them that were, you know, interested in the problem because

they thought they might be able to commercialize it for making stable tables to make microelectronics,

for example, which are limited by how stable the table is.

At this point, it's a little expensive.

You never know.

You never know where this leads.

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

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

stumbling block to get over on the engineer side?

Was there any time where there was a doubt, where it's like, I'm not sure we would be

able to do this, a kind of engineering challenge that was hit?

Do you remember?

I think, though, one that my colleague at MIT, Ray Weiss, worked on so hard and was much

more of a worry than this.

This is only a question.

If you do not do it well enough, you have to keep making it better somehow.

But this whole huge instrument has to be in vacuum.

And the vacuum tanks are, you know, this big around.

And so, it's the world's biggest high vacuum system.

And how do you make it, first of all, how do you make this four meter long sealed vacuum

system?

It has to be made out of...

Four kilometers long.

Four kilometers long, would I say something else?

Meters.

Four kilometers long.

Big difference.

Yeah.

And so, but to make it, yeah, we started with a roll of stainless steel and then we roll

it out like a spiral so that there's a spiral weld on it.

Okay.

So, the engineering was fine.

We did that.

We worked through very good companies and so forth to build it.

But the big worry was, what if you develop a leak?

This is a high vacuum, not just vacuum system.

And in a laboratory, if there's a leak, you put helium around the thing you have and then

you detect where the helium is coming in.

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

So you might not actually even know that there's a leak and it will be affecting...

Well, we can measure how good the vacuum is so we can know that.

But there are leak and develop and then we don't...

How do we fix it?

How do we find it?

And so that was...

You asked about a worry.

That was always a really big worry.

What's the difference between a high vacuum and a vacuum?

What is high vacuum?

That's like some delta of close to vacuum.

Is there some threshold?

Well, there's a unit.

High vacuum is when the vacuum and the units that are used which are torsors, 10 to the

minus 9.

And high vacuum is usually used in small places.

The biggest vacuum system period is at CERN in this big particle accelerator.

But the high vacuum where they need really good vacuum so particles don't scatter and

is smaller than ours.

So ours is a really large high vacuum system.

I don't know.

This is so cool.

I mean, this is basically by far the greatest listening device ever built by humans.

The fact that descendants of apes could do this.

That evolution started with single cell organisms.

Is there any more...

I'm a huge theorist, yeah, yeah.

But like bridges, when I look at bridges from a civil engineering perspective is one of

the most beautiful creations by human beings.

With physics, you're using physics to construct objects that can support huge amount of mass.

And it's like structural, but it's also beautiful and that humans can collaborate to create

that throughout history.

And then you take this on another level.

This is like exciting to me beyond measure that humans can create something so precise.

But another concept lost in this, you just said you started talking about single cell.

Okay.

You have to realize this discovery that we made that everybody's bought off on happened

1.3 billion years ago, somewhere, and then the signal came to us 1.3 billion years ago,

we were just converting on the earth from single cell to multi cell life.

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

We weren't even close to being here.

We're both developing slowly.

Well, yeah, we were going from single cell to multi cell life at that point.

All to meet up at this point.

Yeah.

Wow.

That's almost romantic.

It is.

Okay.

So on the human side of things, it's kind of fascinating because you're talking about

a over a thousand people team for LIGO that started out with around 100, and you for parts

of the time at least led this team.

What does it take to lead a team like this of incredibly brilliant theoreticians and engineers

and just a lot of different parties involved, a lot of egos, a lot of ideas.

You had this funny example, I forget where, where in publishing a paper, you have to all

agree on the phrasing of a certain sentence or the title of the paper and so on.

That's a very interesting, simple example.

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

of team?

Okay.

I think the general idea is one we all know.

You want to, you want to, you want to get where the, the sum of something is more than

the individual parts is what we say, right?

So that's what you're trying to achieve.

Yes.

Okay.

How do you do that actually?

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

less.

Yes.

Why?

Because they overlap.

So you don't have individual things that, you know, this person does that, this person

does that, then you get exactly the sum.

But what you want is to develop where you get more than what the individual contributions

are.

We know that's very common.

People use that expression everywhere.

And it's the expression that has to be kind of built into how people feel it's working.

Because if you're part of a team and you realize that somehow the team is able to do more than

the individuals could do themselves, then they buy on kind of in terms of the process.

So that's the, that's the goal that you have to have is to, to achieve that.

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

not, that one person couldn't do it.

It requires the combined talents to be able to do something that neither of them could

do themselves.

And we have a lot of that kind of thing.

And I think, I mean, build into the, some of the examples that I gave you.

And so how do you then, so, so the key almost in anything you do is the people themselves,

right?

In our case, the first and most important was to attract, to spend years of their life

on this, the best possible people in the world to do it.

So the only way to convince them is that somehow it's better and more interesting for them

than what they could do themselves.

And so that's part of this idea.

I got you.

Yeah.

That's powerful.

If there's best people in the world, there's egos.

Is there something to be said about managing egos?

Well, that's the human problem is always the hardest.

And so there's, that's an art, not a science, I think.

I think the fact here that combined, there's a, was a romantic goal that we had to do something

that people hadn't done before, which was important scientifically and, and a huge challenge

enabled us to say take and get, I mean, what we did just to take an example, we use the

light to go in this thing comes from lasers.

We need a certain kind of laser.

So the kind of laser that we use, there were three different institutions in the world

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

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

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

that they wouldn't have otherwise, and we're part of a bigger team where they could discover

something that isn't even engineers.

These are engineers that do lasers.

So, and they're part of our laser physicists.

And so could you describe the moment or the period of time when finally this incredible

creation of human beings led to a detection of gravitational waves?

It's a long story, unfortunately, this is a part that we started failures along the

way kind of thing or all failures, that's all that's built into it.

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

So we're trying things that no one's done before.

So it's technically not just gravitational waves.

And so it's built on failures.

But anyway, we did before me, even the people did R&D on the concepts.

But starting in 1994, we got money from the National Science Foundation to build this thing.

It took about five years to build it.

So by 1999, we had built the basic unit.

It did not have active seismic isolation at that stage, didn't have some other things

that we have now.

What we did at the beginning was stick to technologies that we had at least enough knowledge that

we could make work or had tested in our own laboratories.

And so then we put together the instrument.

We made it work, it didn't work very well, but it worked, and we didn't see any gravitational

waves.

Then we figured out what limited us, and we went through this every year for almost 10

years, never seeing gravitational waves.

We would run it, looking for gravitational waves for months, learn what limited us, fix

it for months, and then run it again.

Actually we knew we had to take another big step, and that's when we made several changes,

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

And we fortunately got the National Science Foundation to give us another couple hundred

million dollars, 100 million more, and we rebuilt it, or improved it.

And then in 2015, we turned it on, and we almost instantly saw this first collision

of two black holes.

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

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

It sounds like some people immediately believed it, and then you were like...

So as human beings, we all have different reactions to almost anything, and so quite

a few of my colleagues had a Eureka moment immediately.

I mean, it's the figure that we put in our paper first is just data.

We didn't have to go through fancy computer programs to do anything, and we showed next

to it the calculations of Einstein's equations, and it looks just like what we detected.

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

So it was pretty convincing, but you don't want to fool yourself.

So being a scientist, for me, we had to go through and try to understand that the instrument

itself, which was new, I said we had rebuilt it, couldn't somehow generate things that

look like this.

That took some tests, and then the second, you'll appreciate more.

We had to somehow convince ourselves we weren't hacked in some clever way.

Cyber security question.

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

Yeah, no, it can be physical access too.

Yeah, that's fascinating.

It's fascinating that you would think about that.

I mean, not enough, I mean, because it matches prediction.

So the chances of it actually being manipulated is very, very low, but nevertheless...

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

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

I suppose, yeah, I suppose I see.

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

Within a month, we convinced ourselves.

We kept a thousand collaborators quiet during that time.

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

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

understand that it was two black holes and what it was.

The fact that a thousand collaborators were quiet is a really strong indication that this

is a really close knit team.

Yeah, and they're around the world, or either a strong knit or a tight knit or a strong

dictatorship or something.

Yeah, either fear or love, you can rule by fear or love, you can go back to Mackey Valley.

All right, well, I mean, this is really exciting that that's a success story because it didn't

have to be a success story, right?

I mean, eventually, perhaps you could say it'll be an event, but it could have taken

it over a century to get it.

Oh, yeah, yeah, and it's only downhill now, kind of.

What do you mean it's only, you mean with gravitational waves?

Well, yeah, we've now, well, now we're off because of the pandemic, but when we turned

off, we were seeing some sort of gravitational wave event each week.

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

year, it'll probably be one every couple of days, and they're not all the same.

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

So it's all great.

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

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

and technical limitations, not by science.

So another really important discovery that was made before ours was what's called the

Higgs boson, made on the big accelerator at CERN.

This huge accelerator, they discovered a really important thing.

We have Einstein's equation, E equals MC squared.

So energy makes mass or mass can make energy and that's the bomb.

But the mechanism by which that happens, not vision, but how do you create mass from energy

was never understood until there was a theory of it about 70 years ago now.

And so they discovered it's named after a man named Higgs, it's called the Higgs boson.

And so it was discovered.

But since that time, and I worked on those experiments, since that time they haven't

been able to progress very much further, a little bit, but not a lot further.

And the difference is that we're really lucky in what we're doing in that there you see

this Higgs boson, but there's tremendous amount of other physics that goes on and you have

to pick out the needle and the haystack kind of physics.

You can't make the physics go away, it's there.

In our case, we have a very weak signal, but once we get good enough to see it, it's weak

compared to where we've reduced the background.

But the background is not physics, it's just technology.

It's getting ourselves better isolated from the earth or getting a more powerful laser.

And so each time, since 2015, when we saw the first one, we continually can make improvements

that are enabling us to turn this into a real science to do a new kind of astronomy.

It's a little like astronomy, I mean Galileo started the field.

I mean, he basically took lenses that were made for classes and he didn't invent the

first telescope, but made a telescope, looked at Neptune and saw that it had four moons.

That was the birth of not just using your eyes to understand what's out there.

And since that time, we've made better and better telescopes, obviously, and astronomy

thrives.

And in a similar way, we're starting to be able to crawl, but we're starting to be able

to do that with gravitational waves.

And it's going to be more and more that we can do as we can make better and better instruments.

Because as I say, it's not limited by picking it out of others.

Yeah, it's not limited by the physics.

So you have an optimism about engineering.

As human progress marches on, engineering will always find a way to build a large enough

device, accurate enough device to detect the physics.

As long as it's not limited by physics, yeah, they'll do it.

So you two other folks and the entire team won the Nobel Prize for this big effort.

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

fit into all of this?

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?

Well, that's a complicated question.

As a physicist, it's something, if you're trying to win a Nobel Prize, forget it because

they give one a year.

So there's been 200 physicists who have won the Nobel Prize since 1900, and so things

just have to fall right.

So your goal cannot be to win a Nobel Prize, it wasn't my dream.

It's tremendous for science.

Why the Nobel Prize for a guy that made dynamite and stuff is what it is.

It's 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.

It is really good for science.

Celebrating science.

It celebrates science for several days, different fields, chemistry, medicine, and so forth.

Everybody doesn't understand everything about these.

They're generally fairly abstract, but then 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, it should be, but it's not.

So the Nobel Prize is important in that way, otherwise, I have a certain celebrity that

I didn't have before.

And now you get to be a celebrity that advertises science.

It's a mechanism to remind us how incredible, how much credit science deserves and everything

we have.

Well, it has a little bit more.

One thing I didn't expect, which is good, is that we have a government.

I'm not picking on ours necessarily, but it's true of all governments are not run by scientists.

In our case, it's run by lawyers and businessmen.

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

So our country is, and all countries are, hardly take into account science in making

decisions.

Okay.

And having a Nobel Prize, the 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 people pay attention to what I say.

If I talk about global warming, they wouldn't have before I had the Nobel Prize.

Yeah, this is very true.

You're like the celebrities who talk.

Celebrity has power.

Celebrity has power.

And that's important.

And that's a good thing.

That's a good thing, yeah.

Singling out people, I mean, on the other side of it, singling out people has all kinds

of, whether it's for Academy Awards or for this, have unfairness and arbitrariness and

so forth and so on.

So that's the other side of the coin.

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

team and it does the nature of the Nobel Prize is it singles out a few individuals to represent

the team.

Yeah.

Nevertheless, it's a beautiful thing.

What are ways to improve LIGO in the future, increase the sensitivity?

I've seen a few ideas that are kind of fascinating.

Is are you interested in them, sort of looking, I'm not speaking about five years, perhaps

you could speak to the next five years, but also the next hundred years.

Yeah.

So let me talk to both the instrument and the science.

Sure.

So that's, they go hand in hand.

I mean, the thing that I said is if we make it better, we see more kinds of weaker objects

and we do astronomy, okay?

We're very motivated to make a new instrument, which will be a big step, the next step, like

making a new kind of telescope person.

And the ideas of what that instrument should be haven't converged yet.

There's different ideas in Europe.

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

and we have ideas.

So, but I think over the next few years, we'll develop those.

The idea is to make an instrument that's at least 10 times better than what we have,

what we can do with this instrument, 10 times better than that, 10 times better means you

can look 10 times further out, 10 times further out is a thousand times more volume.

So you're seeing much, much more of the universe.

The big change is that if you can see far out, you see further back in history.

Yeah.

You're traveling back in time.

And so, we can start to do what we call cosmology instead of astronomy or astrophysics.

Cosmology is really the study of the evolution of the...

Oh, interesting.

Yeah, yeah.

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

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

optical instruments or electromagnetic waves.

And early in the universe, those were blocked because basically it wasn't transparent.

So the photons couldn't get out when everything was too dense.

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

waves from earlier in the universe can help us understand about the big bang and all that

kind of stuff?

Yeah.

But it's another perspective on the thing.

Is there some insights you think could be revealed just to help a layman understand?

Sure.

First, we don't understand.

We use the word big bang.

We don't understand the physics of what the big bang itself was.

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

mass being made.

And so the big, so I'll say two things.

One is how did it all start?

How did it happen?

And I'll give you at least one example that we don't understand, but we should understand.

We don't know why we're here.

Yes.

No, we do not.

I don't mean it philosophically.

I mean it in terms of physics.

Okay?

Now, what do I mean by that?

If I go into my laboratory at CERN or somewhere and I collide particles together or put energy

together, I make as much antimatter as matter.

Antimatter then annihilates matter and makes energy.

So in the early universe, you made somehow a lot of matter and antimatter, but there

was an asymmetry.

Somehow there was more matter and antimatter than matter and antimatter annihilated each

other.

At least that's what we think.

And there was only matter left over and we live in a universe that we see, this all matter.

We don't have any idea.

We have an ideas, but we don't have any way to understand that at the present time with

the physics that we know.

Can I ask a dumb question?

Does antimatter have anything like a gravitational field to send signals?

So how does this asymmetry of matter and antimatter could be investigated or further understood

by observing gravitational fields or weirdnesses in gravitational fields?

I think that in principle, if there were anti neutron stars instead of just neutron

stars, we would see different kind of signals, but it didn't get to that.

We live in a universe that we've done enough looking because we don't see antimatter,

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

There is no antimatter except when we go in our laboratories.

But when we go in our laboratories, we make as much antimatter as matter.

So there's something about the early universe that made this asymmetry.

But we can't even explain why we're here.

That's what I meant.

Physics wise, not in terms of how we evolved and all that kind of stuff.

So there might be inklings of the physics that gravitational waves look like?

So gravitational waves don't get obstructed like light.

So I said light only goes to 300,000 years.

So it goes back to the beginning.

So if you could study the early universe with gravitational waves, we can't do that yet.

Then it took 400 years to be able to do that with optical.

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

So in terms of questions like why we're here or what the Big Bang was, we should be, we

can in principle study that with gravitational waves.

So to keep moving in this direction, it's a unique kind of way to understand our universe.

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

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

range problem.

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

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

There should be, I would be shocked if there wasn't physics, objects, science, and with

gravity that doesn't show up in everything we do with telescopes.

So I think we're just limited by not having powerful enough instruments yet to do this.

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

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

They're complementary.

It's a little bit like, it's completely analogous to what's been done in astronomy.

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

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

look at the infrared, microwave, ultraviolet, and so forth.

So looking at different wavelengths has been important.

Basically going into space means that we'll look at instead of the audio band, which we

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

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

like we do with astronomy.

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

that's kilometers across into space.

Is that harder to engineer?

It actually is a little different.

It's three satellites separated by hundreds of thousands of kilometers.

And they send a laser beam from one to the other.

And if the triangle changes shape a little bit, they detect that from a passenger.

Sorry, did you say hundreds of thousands of kilometers sending lasers to each other?

Okay.

It's just engineering.

Is it possible, though, as a Google?

Yes.

Okay.

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

probably, there might be some more, what is it, maybe noise is a smaller problem.

I guess there's no vibration to worry about like seismic stuff.

So getting away from Earth, maybe you get away from the seismic stuff.

Yeah.

Those parts are easier.

I'm not sure it is accurately at low frequencies, but they have a lot of tough engineering problems.

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

what we call free masses, just like ours, are isolated from the Earth.

They have to isolate it from the satellite.

And that's a hard problem.

They have to do that pretty not as well as we have to do it.

Okay.

Very well.

And they've done a test mission and the engineering seems to be at least in principle in hand.

This will be in the 2030s, when it's like...

2030s?

Yeah.

This is incredible.

This is incredible.

Let me ask about black holes.

So what we're talking about is observing orbiting black holes.

I saw the terminology of like binary black hole systems.

Binary black holes.

That's when they're dancing.

We're going around each other just like the Earth around the sun.

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

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

holes.

They're one stars.

So we haven't said what a black hole is physically yet.

Yeah.

What's a black hole?

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

And that is a region of space.

So it's simply a region of space where the curvature of spacetime in the gravitational

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

And there's light gets bent in gravitational, if the spacetime is warped enough.

And so even light gets bent around and stays in it.

So that's a concept of a black hole.

So it's not a...

And maybe you can make...

Maybe that's a concept that didn't say how they come about.

And there could be different ways they come about.

The ones that we are seeing, we're not sure what we're trying to learn now is what they...

But the general expectation is that they come...

These black holes happen when a star dies.

So what does that mean that a star dies?

What happens?

A star like our sun basically makes heat and light by fusion, it's made up.

And as it burns, it burns up the hydrogen and then the helium and then slowly works its

way up to the heavier and heavier elements that are in the star.

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

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

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

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

Once it burns itself out, it goes...

And it collapses and that's a supernova.

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

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

field to make a black hole.

Our sun won't, it's too small.

And we don't know exactly what it...

But it's usually thought that a star has to be at least three times as big as our sun

to make a black hole.

But that's the physical way there.

You can make black holes.

That's the first explanation that one would give for what we see, but it's not necessarily

true.

We're not sure yet.

What we see in terms of the origin of the black holes?

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

So you're also looking for the ones who are binary solar systems?

They're binary systems, but they could have been made from binary stars, so there's binary

stars around.

So the first explanation is that that's what they are.

Other explanation, but what we see has some puzzles.

This is kind of the way science works, I guess.

We see heavier ones than up to...

We've seen one system that was 140 times the mass of our own sun.

That's not believed to be possible with the parent being a big star, because big stars

can only be so big or they are unstable.

It's just the fact that they live in an environment that makes them unstable.

So the fact that we see bigger ones, they maybe come from something else.

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

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

means they're really different.

They came from that.

We don't know at this point.

If they came with a big bang, then maybe they account for what we call dark matter or some

of it.

There was a lot of them, because there's a lot of dark matter, but gravitational waves

give you any kind of intuition about the origin of these oscillating.

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

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

around each other, whether they're spinning like this or around.

The direction of the spin?

Yeah.

Or no, the orientation.

Whether the whole system has any wobbles.

What?

So this is now, okay.

We're doing that.

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

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

And so do they point back?

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

You're like mapping this, the early universe via the lens of gravitational waves.

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

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

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

Those probably were made some other way.

We don't know when the galaxies themselves had to do with the formation of the galaxies.

We don't really know.

So the fact that we use the word black hole, the origin of black holes might be quite different

depending on how they happen.

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

How do you feel about black holes as a human being?

There's this thing that's nearly infinitely dense, doesn't let light escape.

Isn't that kind of terrifying?

It feels like the stuff of nightmares.

I think it's an opportunity to do what exactly?

So like the early universe is an opportunity.

In fact, we can study the early universe.

We can learn things like I told you.

And here again, we have an embarrassing situation in physics.

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

theory.

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

explain anything that happens beautifully using quantum field theory and quantum mechanics.

Then we have another theory of physics called general relativity, which is what we've been

talking about most of the time, which is fantastic at describing things at high velocities,

long distances, and so forth.

So that's not the way it's supposed to be.

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

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

People have tried to make a unified theory, what they call a unified theory.

You've heard those words for decades.

They still haven't.

That's been primarily done theoretically, or people actively do that.

My personal belief is that like much of physics, we need some clues.

So we need some experimental evidence.

So where is their place?

If we go to CERN and do those experiments, gravitational waves or general relativity

don't matter.

If we go to study our black holes, elementary particle physics doesn't matter.

We're studying these huge objects.

So where might we have a place where both phenomenon have to be satisfied?

An example is black holes.

Inside black holes.

Yeah.

So we can't do that today.

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

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

of having two theories of physics together.

That's my own romantic idea.

What's the worst that could happen?

It's so enticing.

Just go in and look.

Do you think how far are we away from figuring out the unified theory of physics, the theory

of everything?

I think...

What's your sense?

Who will solve it?

Like what discipline will solve it?

Yeah.

I think so little progress has been made without more experimental clues, as I said, that we're

just not able to say that we're close without some clues.

The best, the closest, the most popular theory these days that might lead to that is called

string theory.

The problem with string theory is it solves a lot of beautiful mathematical problems we

have in physics, and it's very satisfying theoretically, but it has almost no predictive,

maybe no predictive ability, because it is a theory that works in 11 dimensions.

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

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

rid of these other seven dimensions.

That's done mathematically by saying they curl up on each other on scales that are too

small to affect anything here, but how you do that, and that's okay, that's an okay argument,

but how you do that is not unique.

So that means if I start with that theory and I go to our world here, I can't uniquely

go to it.

Which means it's not predictive.

It's not predictive.

And that's actually a killer.

And string theory is, it seems like from my outsider's perspective is lost favor over

the years, perhaps because of this very idea.

Yeah, it's a lack of predictive power.

I mean, science has to connect to something where you make predictions as beautiful as

it might be.

So I don't think we're close.

I think we need some experimental clues.

It may be that information on something we don't understand presently at all like dark

energy or probably not dark matter, but dark energy or something might give us some ideas.

But I don't think we're, I can't envision right now in the short term, meaning the horizon

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

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

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

a multi planetary species?

Another way of asking that from a gravitational and a propulsion perspective, do you think

we'll come up with ways to travel closer to the speed of light or maybe faster than the

speed of light, which would make it a whole heck of a lot easier to expand out into the

universe?

Yeah.

Well, I think, you know, we're not, that's very futuristic.

I think we're not that far from being able to make a one way trip to Mars.

That's then a question of whether people are willing to send somebody on a one way trip.

Oh, I think they are.

I think there's a lot of the explorers burn bright with their hearts.

Yeah, exactly.