All language subtitles for The Science of Interstellar with the Science Advisor, Kip Thorne

Here's Einstein predicting gravitational
waves, laying the foundation for a

laser, and 100 years later, his
gravitational waves are found with

Einstein was kind of smart from the time
I first started working on

gravitational waves until we succeeded
with 50 years.

Some things take a long time. We do
build on each other. None of them by

themselves are smart enough.

This Nobel Prize really belongs to a
thousand people.

If I can see farther than others, it's
because I've stood on the shoulders of

giants who have come before me. And
that's the nature of science.

It's very promising, but it's going to
continue on into the next generation

before the ultimate success is had very,
very, very probably.

This is StarTalk.

I'm your host, Neil deGrasse Tyson, your
personal astrophysicist. And today,

we're featuring one of our one -on -one
conversations.

This time with Professor of Theoretical
Physics, Kip Thorne. Kip Thorne, welcome

to StarTalk.

Pleasure to be with you, Neil. Oh my
gosh, we are coming from your home

in Pasadena, California.

son designed this part of the house and
built it, and my brother designed and

built all the furniture.

These are really useful people to have
in the family.

It's a wonderful family to be in.

They're the practical ones.

I've actually known you for some time,
not that we were beer drinking buddies,

but... I think we've drunk beers
together in the Canary Islands. Yes, we

Okay, okay.

I stand corrected.

But... My first exposure to you was you
were one of the three authors of this

book called Gravitation.

And we used to joke, of course, it was
the only book where you learned about it

just by carrying it around.

And I think we probably wrote it before
you were born.

Possibly. Possibly.

Although I'm older than you might think.

This book is a graduate level treatise
on basically Einstein's general.

Theory of relativity.

At the time I acquired the paperback of
it, which this is, it's tough making a

paperback this thick, but this has the
exact proportions of what was then the

Manhattan Yellow Page.

So we used to call it the phone book.
Yes.

Just affectionately, may I add. It was
brilliantly conceived because I don't

know if you can notice on camera, there
are tabs are different.

The color is white and black.

And they represent two different paths
through the book.

One is sort of the elementary path and
one the more advanced path, except it

looked advanced to me at the time. So
whose idea was this to come up with this

book? Coming up with the book, I think
it was sort of grew out of discussions

that Charlie Misner, John Wheeler, my
PhD advisor, and I had.

A few years after I got my PhD. Those
are the three co -authors there. Those

the three co -authors. And so it sort of
grew organically.

That's the best kind of projects they
have. In the 1960s and early 1970s.

Yes, I was born before the 60s.

Oh, really?

So on here is Charlie Misner, who was at
the University of Maryland.

Yes. And so my copy of this, I had you
sign it.

And then I spent a year teaching at the
University of Maryland. So I quickly

went over to his office and had him sign
it. But before then, I started out in

graduate school at the University of
Texas where John Archibald Wheeler had,

they stole him from Princeton, I think
is what that, or lured him from

Princeton, I think. Yeah, that's
inaccurate.

And so I had all three of them sign it.
In fact, John Wheeler's.

course that he taught in general
relativity is where I met my wife.

Wow. She has a PhD in mathematical
physics. So we met in relativity class.

thought I'd say that.

Very romantic place to meet.

Very romantic.

Very romantic.

And John Wheeler used to give out a
penny if you caught an error that he

committed on the front board. So I have
one of his pennies.

I don't remember.

It was not a big day. It was like.

It was a typo or something, the written
version of a typo.

So anyhow,

it's just a delight to meet again with
you.

And what prompted this was our, you
know, you have a lot of

accolades, of course, including the
Nobel Prize.

Okay. But more importantly than that,
you were science advisor on the film

Interstellar. Well, I was more than
science advisor. Yes, you were. You were

executive producer.

I was more than executive producer. It
grew out of a treatment that Linda Ope's

an ex -girlfriend of mine. Oh, Linda
Ope's a big producer of sci -fi films.

Yeah, a big producer of films of a wide
variety. But Linda and I dated in 1979,

80.

She was too high strung for me and I was
too nerdy for her, but we became close

friends. Wow.

Who knows this? Why didn't I know this?

No, stop.

Where would one learn this?

We need a physicist gossip column. Is
that right? It was some years later

Carl Sagan, who set us up on a blind
date, by the way, we met. Okay.

Some years later.

And Linda called me up and said, would
you like to brainstorm with me for a

movie? Wow.

And we did. And that's how Interstellar
was born.

So was that at the time? It really was
the creation of the Nolan brothers

because they took what we had given
them, which was basically a structure

a venue for the movie, the warped side
of the universe.

And they ran with it and changed our
story almost completely.

And made it into a great film.

All the seeds came out of Linda and me.

At the time, I mean, you're a professor
at Caltech, the Richard Feynman

professor at Caltech, now emeritus.

Caltech is a pretty high -level place.

How was it viewed for you to say, guys,
hold on, I'm going to make a movie now?

How is that received by your colleagues?

I think they were all enthusiastic.

Caltech is a different kind of a place
than some other more stuffy university.

Oh, okay. Okay. I never hung out much at
Caltech. I couldn't judge the mood or

the tone.

Yeah. No, look, we're on the edge of
Hollywood.

The Hollywood folks come over and, you
know, Big Bang Theory was based on

Caltech. Right. They didn't call it
Caltech. What did they call it? They did

call it Caltech in the first few.

Okay. And then they stopped using the
Caltech name because the shirts, that's

Hollywood speak for the attorneys.

Oh, yeah, the stiff shirts, yeah, up in
the office. The shirts got scared that

they might do something on screen that
the Caltech shirts wouldn't like and the

Caltech shirts might sue the Hollywood
shirts. Okay. And so they stopped using

Caltech name. And in the film, which I
adored.

What was it called? Real Genius?

Yeah. Real Genius. They were at Pacific
Tech, all right? That was where all the

smart kids were.

So, of course, Pasadena is in, like, I
can't say foothills of Hollywood, but

have a proximal awareness of this huge
industry.

Yeah. And you know that science fiction
matters as a genre.

Well, and some of us love it.

I love it. I sign up every time.

Interstellar, I think it introduced many
people to authentic gravitational

physics for the very first time.

Well, Interstellar was unlike almost any
other film. I think there were

precursors in 2001 and in Contact.

Yeah, Carl Sagan's Contact.

Carl Sagan's Contact.

And the point is that science...

Lots of science was baked into that film
from the very beginning because of the

way it was born and because of the
close, close collaboration I had with

Nolan brothers.

And built in right from the very
beginning.

Baked in.

Baked in. And a science in which the
guideline that we worked from is

that nothing in the movie would violate
well -established physical laws and all

the wild things would at least spring.

from science in some manner.

As any good science fiction story should
be, but there's not enough.

Well, there's nothing wrong with fantasy
films, the Harry Potter style, for

example. It's just a different genre.

By the way, that film, you...

You must have known. You said, okay,
we're going to have to help people out.

Give a guy a break, okay?

They're trying to see the movie. They're
trying to follow what's going on. What

the hell is happening?

Why did the guy get old?

Why is he younger than his mother?
What's going on?

And you upped and said, let's help a
person out. Yeah, well, I would put it a

little differently.

I saw it as a superb opportunity to use
this film as a motivator

interested or intrigued in science.

And then there would be a bridge to the
science through this book. Admit it, you

created a gateway film. It was a gateway
film, yes. So The Science of

Interstellar, New York Times bestseller,
Kip Thorne, with a foreword written by,

of course, Christopher Nolan.

And spoiler alert, this book explains
the fantastic climax and ending

of Interstellar. And so let me tell you
how this issue came about.

Chris said to me early on, I would like
to make a film where the ending is as

mysterious as the ending of 2001, Space
Odyssey.

That's a high bar.

That's a high bar. But he greatly
admires Stanley Kubrick and that film.

And so somewhat later on, as we were
talking about the ending and we had lots

conversations about the ending, he said,
well, you can explain the ending in

this book that you're.

planning to write.

So he volunteered you to write the book.

Well, no, I was already planning to
write the book, but he identified that

the place where the ending will get
explained. He was not going to explain

ending. He would leave it mysterious.
Not in this film. He was pulling a

on us. That's right.

In fact, we interviewed Christopher
Nolan. If you're an archive diver, we've

a whole episode with Christopher Nolan,
even before Interstellar was...

And as we know, so many of his movies he
plays with time in some kind of

interesting way. If I remember
correctly, he talks about how

Space Odyssey was to him back in 1968.

That would have been.

So let me ask you just a couple of
things about the storyline.

And I have an issue with it, if I may.

I don't know if I ever went public on
this, but I figure...

I'm in front of the man himself, so if I
have an issue, it would be here and

now. You're going to get turned into a
journalist who's challenging me? I don't

know. Going to give me a tough time?
Yeah.

This can't be just all, okay, softball.
Let's play a little hardball.

So I guess my issue, we're looking for a
planet.

Again, this is in the themes of the
movie.

We're looking for a planet like Earth,
similar enough to Earth, That we can

people there to continue our
civilization and our species.

Is that a fair characterization of a
plot line? The plot line. Okay. And it

turns out there's like a wormhole that
can make that happen a little faster.

Because otherwise you don't live long
enough to travel the distances with the

rockets available to hit those
destinations. Okay.

I'm just thinking, this blight on the
crops.

that was starving everyone on Earth,
requiring that we jump ship, literally

ship to go find another ship, another
spaceship planet.

It seems to me that whatever effort it
takes to find another Earth, travel

through a wormhole, ship a billion,
terraform it, ship a billion people

whatever that effort is, seems to me to
be a bigger effort.

than just telling the biologists, come
up with a serum that could fix the

Even today, we have full knowledge of
crop genomes. Just fix it.

Whatever it is, just go in there, nip
-tuck the DNA, fix it.

Isn't that cheaper, easier, faster than
wormholing your way off this planet?

That's where I'm coming from.

So you think that all problems can be
solved by humans with human technology

a time scale?

You have such faith in humans.

Come on. So I'm the optimist here. Okay,
so let me describe.

This characterizes how this movie was
done.

So when it was Jonah Nolan, Chris's
brother, who came up with the idea that

wanted a blight or something like that.

And so we said, okay, we will bring
together.

The best biologists we can, who are
experts on these kinds of things, put

together, mostly Caltech biologists, and

we had a dinner, and we brought out very
expensive wine for them to drink, and

we set up a recording.

In vino veritas, okay? In truth, there
is wine. In wine, there is truth, yes.

And so we...

I had a conversation that lasted about
three or four hours at the Caltech

Faculty Club, the Athenaeum, about what
would be the best backstory here. There

are two types of blights.

There are generalized blights that
attack lots of crops.

Lots of different species of crops. Lots
of different species of crops.

But they are generally fairly benign
blights. And then there are...

Blights that are very specific to a
particular crop, and they can be very

blights that may totally wipe out that
species on Earth even. But basically for

Earth and life on Earth to survive, you
better not have a vicious generalized

blight.

But according to the biologists that I
discussed this with, they didn't know of

anything that would prevent the
development.

of a very vicious generalized blight.

So that's what occurs in this movie. And
it's something that biologists have

never seen, but they cannot rule it out.

Okay, so let me repeat what I think you
said. They have vicious lethal blights

that attack a species, less lethal
generalized blights that cross species

boundaries, and they can't rule out a
lethal...

that would cross species.

That's right. And so that's what's
happening in this film.

That's what's happening in the film.
Okay. And that's what they just,

biologists, are on Earth in the back.

Okay, I'll give you that. Okay. Okay, so
anyway, this film is full of

backstories because of the way we did
it. As I say again, it's unlike almost

other film in that these issues were...

Like that. We're vetted. We're vetted by
the world's best experts in the process

of the writing of the screenplay.

Okay. As we're diving into Kip Thorne's
impressive work, one thing is clear.

His theories have reshaped our
understanding of the universe.

So you might think the latest Nobel
Prize for physics would go to someone

Thorne, but it went to computer
scientists instead.

Their contributions to machine learning
is... undeniable, but still a surprise

for the world of physics.

Some reports focus on the godfather of
AI regretting his invention, while

don't exactly see the problem.

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and the way we consume information and
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Now, back to the show.

Well, I got another one.

Okay, you're one for one. All right.
When they're on the black hole planet.

Okay? And then they see this wave
coming.

Okay, it's Miller's planet. Miller's
planet, sorry. That's the water planet.

planet orbiting gargantuan.

Gargantua. Okay?

The strength of tidal forces are highly
sensitive to the distance you are to

that which is causing the tides.

Highly sensitive.

Okay? But every illustration I've drawn
or taught about tides, they're not so

peaky. They're much...

broader in their representation on a
planet.

And so there they are, wading in water,
but then they see this

single wave come. And if it is a single
wave, as we've seen with tsunamis, it

actually takes water away from what's
ahead of it.

Because it can't just be water out of
nowhere. It's drawing water from its

vicinity. So my two issues was, if it's
tidal, would it be that peaky?

And if it's any kind of wave, how could
it still leave the water laying around

its vicinity and then just be that big
as it came by?

There is a type of wave called a
solitary wave on water.

You could tell me you brought wave
people together and had that lunch.

No.

This particular kind of wave was
discovered in the 1700s by, I've

who, a...

physicist in England who saw a boat that
was being pulled by horses.

And it was just starting up. And it
created this wave that traveled down a

channel, a canal.

And it was peaked like the wave in
Interstellar. Though the wave in

Interstellar, I have to admit, it was
exaggerated.

I don't mind exaggeration. There was
some exaggeration in the peak. But it

traveled down the channel. It never
broke.

Most waves at the ocean, they break.

Okay, just so we can get the picture
because we're talking about centuries

When you say a channel, that would be a
channel or a canal.

A canal. And then there's a towpath on
the side. And then people and more

beasts of burden would drag things
through the canal. Because they

don't typically have current. Drag a
barge down the canal. A barge, exactly.

And so this barge was dragged down the
canal.

And it was just starting up and it
created this wave.

On the startup.

On the startup. And it just headed out
and just took off and went down the

channel. And this guy got on his horse
and he followed down the channel.

You've got to love curious physics.

Nothing gets by. And it went down the
channel for, I don't know, a mile or two

without changing its shape, without
breaking. Without breaking.

And so the theory of these waves is that

there are two different effects that
cause a wave to steepen or

disperse, and the two can balance each
other out in a stable sort of a way. And

give it longer life. And give it long
life.

Aside from the issue of friction, if
there were no friction, it would just

forever and keep propagating in a very
stable way.

There's a mathematics behind it,
something called the Cordevec -DeVries

that this is a solution of. But anyway,
these waves then... So that equation,

I presume, has both kinds of waves in
equilibrium somehow represented as a

static wave. The dispersion...

And the steepening. The steepening is
due to nonlinearities. The dispersion is

due to the fact that the higher parts of
the water travel faster than the lower

parts of the water.

I didn't know that.

Up here at the ocean, you see a little
tiny wave. It travels quite slowly. You

see a big wave. It travels quite fast.

And that's why the crest of the wave
will actually break before the rest of

wave gets there. Yeah, that's right. Is
that part of the reason? That's right.

Unless that's being balanced out.

Cool. By dispersion, which is – Cool.

Anyway. I love it. No, it's good. Good.
No, I'm loving it. I'm getting this

slightly confused. But anyway, the two
effects balance each other to produce

this very stable solitary wave.

And so in the movie – but for this
stable solitary wave, the height of the

is – and I've forgotten the number, but
it's something like six times higher

than the depth of the water. Got it.

So there's a problem now in the movie
because they're walking around in

water, and this wave is high, and so
it's got to be deep water.

Okay. But they're on an island.

This is the back story. Again, there's
always a back story. So they're on a

subterranean, a subsurface island.
You've got to read it in my book. Okay.

They're on an island.

They're on an island, and this wave
diffracts around the island. They hardly

notice the island at all.

So, again, it's all explainable, except
there is a bit of exaggeration.

The CTI wave was made somewhat more

peaked. We'll give you that.

It's a movie, and it's Hollywood.

What you're saying is this wave might
have been caused by some effect other

the tidal forces of the black hole.
Yeah, well, this wave is caused, in

the fact that time has much slowed on
this planet. So the

planet has been put into the orbit
around Gargantua not that long ago as

the planet, though it's a long, long
time ago as seen from far away.

It's like Mercury, like the moon keeps
one face toward Earth or Mercury keeps

one face toward the sun due to tidal
effects.

This planet is distorted by tidal
effects and it's swinging back and

has not yet settled down to one face
toward the planet. And that swinging

and forth is generating this wave.

It's all in the book. He weaseled out of
another one. Okay.

There's an enormous amount of science in
that book.

I must admit that when I went through
the book. And one last point. You didn't

study it carefully enough.

One last point. We took our show to
Oxford recently, and I

interviewed at Oxford, I think it was a
postdoc, and his name was Andrew

Mummery.

And he showed us a recent paper he
published. I don't know if you've seen

recently, like within the past 18
months.

And he's a theoretical physicist.

And he alerted me to something I'd never
knew.

I love the field, but it's not my active
professional field. That in the

vicinity of a black hole, there is an
innermost orbit.

Because, of course, you can orbit any
source of gravity, even if it's a black

hole.

For black holes in particular, there's
an orbit within which the orbit is no

longer stable and it will spiral into
the black hole itself. And according to

his calculation, to get the time
dilation necessary in the scene with the

hole planet, which was huge. Remember,
they were on the planet for like 15

minutes or whatever. One hour on the
planet is seven years.

Seven years up in their spaceship, okay?

And the guy where they left there, he's
like gray and unshaven and everything.

And we're like, oh my gosh, there's some
serious Einsteinian physics going on

here. His calculations show that for
that difference, for that extreme

difference in time dilation, requires
that planet orbit so close to the black

hole there would be in the unstable
zone.

And so I just thought I'd... Tell you
that.

My calculation says otherwise.

And where's his Nobel Prize? The other
guy's? The formula is in the book.

In this book? Yeah. So we don't have to
go to your graduate textbook for that?

Well, not for the answer. Okay.

If you want to derive the formula,
that's a lot of work.

So let me tell you the story behind
this. Oh, so everyone's got a story.

Christopher Nolan says to me one day, he
says, I want the hero in

Cooper, the hero in this movie, to go
down onto this planet.

Cooper played by Matthew McConaughey.
That's right.

Professor Brand's daughter is played by
Jessica Chastain.

Christopher Nolan says to me, he says, I
want in this movie that one hour on

Miller's planet is seven years.

up at very high orbit or back on Earth.

He prescribed that?

Yes, and I said to him, that's
impossible because the planet will fall

black hole.

He said, go do a real calculation. I've
already learned that your off -the -cuff

reactions can be wrong, and I should not
trust you unless you do a real

calculation. There's a good Hollywood
producer.

Go back and give me the answer I'm
looking for.

Well, and so I went back home, and I did
a real calculation, and I was amazed.

that the last stable circular orbit,
which is what we're talking about, is

if the planet spins fast enough, the
last circular stable orbit can

have as high a redshift, as high a time
difference

as you might wish.

It requires that this black hole spin
extremely close to the maximum

possible spin.

And so in the book, I give the formula
for what is the spin of the black hole

that is required to produce a given
amount of slowing of time. I did not

that. And so it's an approximate
formula. But it's a formula that can be

derived.

Or a bit of algebra. Okay, so the one
one would just learn about would

be the lowest stable orbit around a non
-rotating black hole. That's right. And

that's a clean... That's a clean
problem.

Clean problem. That's what I was
thinking when I said I want this. When I

that if I made the black hole spin, that
it would get closer, but I couldn't

imagine. I could not imagine that nature
would provide it an

orbit.

For a black hole, it spins fast enough
that it can provide this much of a

slowing of time. But it does. It does.
At least, unless I made a mathematical

error. But I don't think that's likely
because I use Mathematica.

Okay. You had tools to help you do this.

To check my calculations. Because it's
not just an analytic solution.

Well, it is an analytic solution.

But it's very complicated. But it's very
complicated.

Okay. Well, it's a power series
solution.

In the end.

I think our hero character is inside the
black hole. We come to understand this.

And he has access to a timeline that
wouldn't otherwise be available to him.

he sees his daughter's bookshelf.

Well, he's no longer inside the black
hole.

Where is he when he's doing this? So
this is the key thing that's not

that you only understand if you read my
book.

You didn't read it well enough.

Busted. No, I read a lot of it. I read
some of the biology. And it was a long

time ago, too. Yes, okay.

So when he gets inside the black hole,
he is scooped up

by a spacecraft that was built by this
advanced

civilization that provided the wormhole
to him and to humanity.

And it's called the Tesseract.

And the Tesseract is a four -dimensional
cube, four spatial dimensions. And

that's why in there you saw, I guess,
the past and future all kind of

simultaneously. It felt very higher
dimensional.

Yeah, that's right. So the Tesseract, so
let me back up. I'll tell you a story.

So early on when we were working on the
film,

And Christopher Nolan said to me he
wanted to take his hero

back to Earth, Cooper back to Earth, by
a different route than the wormhole, 10

billion light years away from the Earth.
How's he going to do it if it doesn't

go through a wormhole?

He said, well, I want to take him back
faster than the speed of light.

And, of course, I say to Chris.

You can't do that. It violates the laws
of physics. He says, go do a real

calculation.

I said, I don't have to do a real
calculation.

And so we discussed this for a week. And
then he threw in the towel. He said,

okay, I believe you.

And so what do we do? And so I said,
well, you put him, he goes inside the

hole.

He gets deposited on the three
-dimensional surface of a four

sphere. And this four -dimensional
sphere,

is a spacecraft that can go into the
bulk, into the higher dimension.

And it goes out of the black hole, not
through the horizon. It can't do that.

goes up through the fourth dimension. Up
through the fourth space dimension, or

what's called the fifth dimension in the
movie. Time is the fourth dimension.

And goes back to Earth. And the distance
back to the Earth is less than the

distance between the Earth and the sun.

Even though it's 10 billion light years
inside of our universe.

Up in the bulk, it's a very short
distance. And so he can get back very

This is the higher dimensional space
-time in which we are now having this

event. So he gets back very quickly,
riding on the surface of this four

-dimensional sphere. He said, I like it
all entirely, except I'm going to use a

four -dimensional cube instead of a four
-dimensional sphere. That's a

tesseract. Yes. And so that's what
happens.

And when you see Cooper out there sort
of...

Flailing around at the beginning of the
Tesseract scene.

He's being carried by the Tesseract back
to Earth. But you don't know that's

what's happening until you read my book.
By agreement between Chris and me.

That's the only way anyone's ever going
to know. So anyway, he's carried back to

Earth. And then everything is happening
when the Tesseract is docked in the

higher dimension.

Giving access to his life.

In that past time. That's right. So it's
docked in his home in his daughter's

bedroom. Okay, so now he's pushing books
off the shelves that land

on the floor, and through some clever
cryptographic judgment, he's spelling

words with the first letter of the title
of each book.

Okay, here's my issue.

I had no problems with Tesseract, Black
Hole.

Fourth dimension, five dimensions.

How does he know the title of each book
from the other

side of the book?

Well, I don't remember. That's how he's
actually.

He's pushing books. I know he's pushing.
I know he's pushing books out from this

side. Yeah. Yeah. And all he sees is the
other side of the library. I guess I

had forgotten that he was spelling
things out based on.

The first word.

Oh, you forgot.

I forgot or I didn't know.

Or you're wrong.

So that was one of my issues there.

That one, I don't know.

Oh, okay.

Okay. I don't know. Okay. So you're
three for four.

He probably has a photographic memory. A
photographic memory of the other side

of the book. Yeah.

What's this I hear?

that you can use a wormhole to travel
backwards in time. Does the math check

out? Does the Einsteinian physics check
out? And does that mean I will just show

up a younger version of myself and shake
my own hand? Is that what you mean by

that? Or do I no longer exist in the
time that I left for my younger version

myself to see that?

And wasn't there, didn't Hawking put
forth a...

time travel prevention conjecture or
something?

What's going on there?

So this is all an outgrowth of my phone
conversation with Carl Sagan

when he was working on the novel for
Contact,

where he triggered me to start thinking
about wormholes.

And then having started to think about
wormholes, it became pretty obvious to

rather quickly that if I give my wife,
Sarah Lee,

one mouth of a wormhole, and she carries
it at high speed in a rocket ship out

into space and then back, and I keep the
other mouth at home.

If she sees me age by 50 years back on
Earth, well, she ages only one year

out and coming back.

But if we look through the wormhole at
each other, we see each other aging at

the same rate.

Just imagine we hold hands and we look
at each other's wristwatches. They're

ticking away at the same rate. So
through the wormhole, we've aged at the

rate. We're the same age.

But looking through outside the
wormhole. Through a normal universe.

She's aged one year and I'm aged 50
years. Something weird has happened. The

wormhole has become a time machine.

If I just go over and go into her mouth,
wormhole mouth, and come out, I'll meet

my younger self.

Okay, now Hawking said, no, we're not
going to allow this. There's some

conjecture.

yet to be discovered, that'll tell you
you can't do that. Well, so we get

You're going too fast. I'm going too
fast. Sorry.

So then I talked to friends at the
University of Chicago.

It's crucial to talk to friends.

They tell you where you're all at. They
tell you when you made a mistake.

They straighten you out. And they
pointed out to me that...

It might be that when the time machine
is turned on, it'll self -destruct,

basically, they said.

I said, I don't understand.

They said, go do a calculation. So I
went and did a calculation.

And the issue is, and they had guessed,
and basically, it's

oversimplified, but Bob Garoach and
Robert Wald at Chicago.

Anyway, it turns out that...

At the moment that you can first time
travel, the first thing that goes

it can be vacuum fluctuations of light,
say, that enter her mouth or the

wormhole, come out of my mouth and go
back and arrive back at her mouth at the

very moment they started out. Now you
have twice as much at the same place in

space and time.

So this is a runaway.

So it's a runaway.

You now have twice as much, and then it
goes around again. Now you have four

times as much. It goes around again. So
this runaway builds up.

Just like the feedback between a
microphone and a speaker.

Precisely. And it just runs away. It
just runs away. It runs away. And this

runaway shows up in the quantum
mechanical calculation that I did.

You're bumming me out. Together with
Sung Won Kim, a Korean postdoc of mine.

Okay, I want to be a movie director and
say, go home and figure out how to do

this.

Pull another rabbit out of the hat here.

Well, anyway, we discovered this.

Stephen, I think, and one of his,
Stephen Hawking, and a student of his, I

think, had more or less the same
discovery at the same time.

Except Stephen probably just did it all
in his head.

That's the way Stephen is.

Anyway, so.

And then Stephen and I started
corresponding about it by email and

the phone about it and so forth. It
appeared to me, looking at the details

the calculation, that in fact the
explosion, if I designed the time

right, the details of the explosion
would not be strong enough to destroy

wormhole.

And Stephen then showed me that I was
wrong.

And we argued back and forth for a
while. Finally, we came to agree that

explosion becomes strong enough that
quantum gravity enters in and then holds

the answer tightly in its grip.

And so we won't know whether the time
machine self -destructs until we

understand the laws of quantum gravity.
So let me be fun and obscure here. But

then we come to the Hawking.

Cosmic censorship conjecture. That's
what it's called.

Yeah. The conjecture that, in fact, in
the end, the laws

of quantum gravity won't save the day.
The wormhole will be destroyed.

And any time machine that any advanced
civilization makes will be destroyed

they try to turn it on by these vacuum
fluctuations.

And thereby, as Hawking says, Keeping
the universe safe for historians of all

species.

It reminds me of the ultraviolet
catastrophe where you run the

is going to blow up. How does this even
work? And then out comes the discovery

of the quantum, which saves the day.

Right. And this is, it could be a
calculation waiting for another branch

physics to open or another progress in
the known branches of physics to

The LIGO team has, has perfected a
technique called quantum precision

measurement, which is based on
manipulating vacuum fluctuations in

circumvent the uncertainty principle.

And so this business of manipulating
vacuum fluctuations is something we do

modern physics.

If memory serves, Carl Sagan came up to
you and said, for contact, I want to go

far distances quickly.

How am I going to do it? Can you cook up
a wormhole for me?

Carl phoned me back in the 80s.

When he's writing the novel, because
obviously the novel predated the movie.

That's right.

And he said that he wanted, that he has
written, he'd already

written the book, the novel.

It was already in page proof.

And he said, I've got this novel. It's
in page proof. The publisher's not going

to be happy if I change it, but I really
need some help to see what the truth

is, and then we'll figure out how to
deal with this.

And he said that I have my heroine
traveling through a black

hole to get to the Star Vega.

And I said, that's...

Rather dangerous.

There's a singularity in there.

There's a singularity in there and you
can't get through to the Star Vega.

So what you actually need is a wormhole.

But there is an issue that wormholes
implode. They collapse so quick that

nothing can get through.

But I'll see if I can figure out how to
hold a wormhole open just for you, Carl.

And so I was going with – It's like rent
-a -physicist.

It's like whatever your needs are. So I
was getting in a car that morning to

ride with my former wife to our
daughter's graduation up at Santa Cruz.

And so Linda said, I'll drive and you
calculate.

Okay. So she drove and I calculated and
I fiddled around and then it became

fairly obvious.

Turns out some other physicists figured
this out sooner, but that's the usual

thing with me.

I figure it out, and then I go see if
people know this before or not.

So anyway, I figured out that if you had
what I

like to call exotic matter that repels
gravitationally, and you put it inside

the throat of a wormhole, that can hold
the wormhole open. It would be like

pushing it.

Yeah, that's right. It basically repels
the walls of wormhole to hold them open.

And it turns out that that will do it.
But you have to have

enough exotic matter to hold the
wormhole open. And I

deduced a formula for how much you had
to have. And it basically says the

following.

If you move through the wormhole... Let
the record show he's about to describe.

How to make a wormhole. No, no. Only how
much you thought it mattered.

That sounds like a recipe to me.

So you travel through the wormhole as
close to the speed of light as you

possibly can.

Just as close to the speed of light.

And you add up all the energy density

all the way through the wormhole of
stuff that's in the wormhole.

The net has to be negative, and then you
can hold the wormhole open. So it

basically means you've got more negative
energy in there than positive energy.

We have nothing known as exotic matter.

Oh, yes, we do.

What? Yeah.

Oh, is this in your basement?

What?

What do you mean, oh, yes, we do?

Okay, what?

What is our exotic matter that would
fulfill this purpose?

Should we turn off the camera now?

Is the government going to show up in
your driveway?

Okay, go.

Men in black. I learned about this from
Yakov Borisovich Zeldovich in Moscow.

Zeldovich. Zeldovich was one of the
inventors of the Russian hydrogen bomb.

Okay. And I learned this from him. All
right. He was really brilliant. I

about vacuum fluctuation.

And how important they can be and how
powerful it can be if you can manipulate

them.

And so if you take a box and you remove
everything that can possibly

be removed from the box, you're left in
the end with tiny

fluctuations of everything that possibly
could have been in the box.

So electric fields.

You have fluctuating electric fields,
fluctuating magnetic fields, fluctuating

protons, electrons, fluctuating Neal
Tysons across Tysons.

So this creates a form of pressure
inside the box? Well, so there's

pressure and not vanishing energy due to
renormalization.

Now that's a nasty word in physics.

You can measure energy by whether it
produces gravity or not.

And although these fluctuations that are
there, you can think of them as

particles, say particles of light,
flashing in and out of existence

why is this not... The virtual particles
that people speak of.

So it's virtual particles.

It is that. Okay. We've spoken about
those on our show before. Okay. So you

virtual particles. With Brian Greene, in
fact. So you have virtual particles in

the vacuum. Popping in and out of
existence.

Popping in and out. And you can't stop
it. You can't prevent it.

However, you can take fluctuations from
one region and borrow them and put them

in another adjacent region for a little
while.

Or if you put an electrically conducting
sheet, say a sheet of

superconducting metal here, then that
will suppress the fluctuating

electric fields parallel to the metal
because they would create an infinite

current flowing in that metal. And that
would wipe out the

electric field parallel to the metal.

Is that the effect?

An element of the Casimir effect? Yes,
that's the Casimir effect. It is, yeah,

where you have two parallel plates
evacuated between them. That's right.

there's a point where they actually feel
a whole other force attracting them.

And so what that force really is, is in
the region between them, the

vacuum fluctuations are suppressed.

And so you have negative energy in
between.

That negative energy is sucking them
together.

And you have...

They can do work on you. If you're
holding on to these plates and they

each other. You have to put energy to
resist it.

You put energy in. As they go together,
they do work on you.

The electromagnetic field between two
plates in the Casimir effect is exotic.

Okay. So you have this in your basement
is what you're telling me. I don't have

it in my basement, but physicists do
this.

Let me just say as a side remark.

Having learned a lot about vacuum
fluctuations, we in LIGO and our gravity

project. I'll just make the remark that
the LIGO team

has perfected a technique called quantum
precision measurement, which is based

on manipulating vacuum fluctuations in
order to circumvent the uncertainty

principle.

The business of manipulating vacuum
fluctuations is something we do in

physics. And it is something then that
you can imagine, you can ask,

can a very advanced civilization
manipulate vacuum fluctuations

adequately in order to make enough
exotic matter inside a

wormhole to hold the wormhole open?

And so I pose this as a question to my
physicist colleagues,

stimulated by Carl Sagan, him wanting to
send his

heroin through a black hole. I said, no
use a wormhole.

And so we've got to hold it open. And
so, physicist colleagues, please help

figure out, can an advanced civilization
do this? And the answer is we still

don't know.

Forty years later now, we still don't
know. Right. Well, we're doing magic

compared to what anyone thought was
possible 50 years ago. Certainly the

quantum physics. We're on the centennial
of the decade of quantum discovery.

Back in the 1920s. Well, I was very
close friends with Carl Sagan, and I

developed close friendship with
Christopher Nolan.

Chris has a very different background.

He knows a lot of science, but he's
learned it all by browsing the web.

And he knows it well enough to ask me
hard questions, just like

you do.

But he asked them first, so I have the
answers now.

And it has inspired me to ask questions.

And then I sort of translate to and give
to colleagues because my colleagues are

smarter than I am.

My role is to pass on interesting
questions. You're the conduit for this.

Conduit for interesting questions for my
colleagues to work on. So, dude, you

can't leave well enough alone.

Einstein says maybe there are
gravitational waves emanating.

from major gravitational disturbances in
the universe, and you've got to go up

and find them.

But you're not the first to have
attempted this, right? At the University

Maryland, there was Weber, I think.

What's his first name? Joe. Joe Weber,
of course, who had a cylinder, if I

remember correctly, where he was trying
to measure whether if a gravitational

wave washed over it, he could detect a
distortion in the shape of the cylinder,

I think, was the goal.

The gravitational wave would drive
vibrations of the cylinder, end -to -end

vibrations. Okay. And so he instrumented
it to search for changes

in the amplitude and phase of vibrations
of the cylinder. The cylinder is at a

finite temperature, so it's always
vibrating a little bit because it's a

temperature. And so he instrumented it
with what's called...

piezoelectric transducers, transducers
that he glued around the middle of the

cylinder, that when they were squeezed,
they would generate an electrical

voltage that he could measure.

And they're amazing things, these
piezoelectric transducers, just

amazing. You squeeze them a tiny, tiny
bit and you get a big voltage out.

Joe Weber was tremendously creative.

I think he was working on that while I
was at the University of Maryland. I was

there in the 80s. I think he was still
working on it. Yeah, that's right. So he

began working on it in the late 60s,
early 70s, and

announced that he was seeing possible
evidence for gravitational waves.

There was a lot of skepticism at the
time. Yeah, that's right.

I'm sorry.

He started working on it in the late
50s, early 60s, announced in 69 that he

seeing some possible evidence of
gravitational waves.

And a number of other physicists around
the world built similar detectors.

And the bottom line in the end, after a
period of shaking out, was that others

were not seeing gravitational waves. And
that's the only way science works.

One person's result is not a result
until somebody else, a competitor,

else who uses different wall current,
somebody from another country. You need

multiple verifications. But on the other
hand, Weber, Joe, he

started the field.

He triggered this work.

The approach that he invented for
searching for gravitational waves was

dominant approach.

From then until the 2000s. And a number
of other research groups built similar

detectors and improved them better and
better and better over that period of

time. On that model. On that model.

So, I mean, I have enormous respect for
what he did.

Now you decided to, you and others,
decided to look differently for them.

well, so Ray Weiss, Reiner.

Ray, his friends call him, at MIT was
the primary inventor of an alternative

technique. It was the technique that
ultimately succeeded.

He wrote a technical paper about the

technique that identified all of the
kinds of noise that you would have to

with and explained how you might deal
with them.

and did an analysis of how good this
detector could be.

And he put it all in this paper. So
there's the recipe. Oh, my gosh. It was

recipe for how to go forward. And he
wrote this in 1972.

And Ray, being Ray, didn't publish this
because I think he figured you don't

publish until you have built one and
seen a gravitational wave.

However,

Ray sent...

copies of this around all his
colleagues.

And he put it into quarterly reports of
the MIT laboratory

in which he worked.

And so it is probably the most
influential non -published paper,

that I know of, in physics.

I mean, it was a tour de force, and it
triggered...

The next generation. That actually
succeeded.

I was fortunate enough to visit because
there are two LIGO experiments, one in

Louisiana and the other one is in
Hanford, Washington.

Why do you have two?

Because you can't just have one result.

You're looking for an effect that is so
small that you wouldn't believe it

unless you see it on two independent
instruments. There you go.

You've got these pathways.

Are they a kilometer long?

Four kilometers long. Four kilometers
long.

Evacuated. You send a beam of light that
is split from a laser that's split.

These are at 90 -degree angles.

And they go to the end. They get
reflected back.

And you rejoin them.

And you want to see if their waves line
up.

And if they line up, then each direction
is identical.

You can go home.

If they're slightly different, then one
of these legs experienced a different

encounter with the fabric of the space
-time continuum than the other did.

So actually what you want to do is you
make them slightly different in the

place. So that means you send your laser
light in from this direction.

there's a beam splitter where the light
gets split in two to go down the two

arms.

So the laser light goes in like that.
There's this beam splitter, so the light

gets split in two into one arm in that
direction and the other arm in this

direction.

And then it comes back and recombines in
the beam splitter. The laser light was

coming in from this direction, but when
it recombines, a

little bit of light goes out in a
perpendicular direction.

So you have a laser here and you have an
output over there. And the output

direction is the direction it has a
signal. And if the length of one

arm is shortened and the length of the
other arm is lengthened.

And that would only happen because a
gravitational wave washed over that arm.

That's right.

you get a change in how much light is
coming out to the output.

All right, so you're trying to find a
length difference, and

if I remember the materials from the
press releases, that is equivalent to

-tenth the diameter of a proton?

No, it's equivalent to, it's 10 million
times smaller than an atom.

And a hundred times smaller than a
proton. One one hundredth the diameter

proton. Meanwhile, all the world is
vibrating because everything is at a

temperature. And cool it as much as you
want, there's still vibrations.

And somebody is walking down the street.
I remember being on campus there. Can I

call it a campus? That's what it was.

And you can detect.

Cars on the road a mile away.

You have to insulate this.

That's half the science done for the
experiment.

You should get a Nobel Prize for that.

Well, that's what the Nobel Prize was
given for.

To have successfully insulated the
effect you're trying to measure.

So the way I like to describe it is
you're bouncing light off these mirrors.

And you're looking for a motion of the
mirrors that is 10 million times smaller

than the atoms of which the mirrors are
made.

And, well, the mirrors, the atoms in the
mirrors themselves are vibrating

because they're at finite temperature.

A finite amount is about the same as
their size.

So 10 million times smaller than the
atoms and 10 million times smaller than

vibrations the atoms are undergoing.

So once again, in physics, there's a
phenomenon we're trying to measure, but

it's kind of buried, and you need a way
to get to it.

And it seems like half, if not more than
half, of the effort is how brilliant

is your engineer that you've brought on
to the task to accomplish this?

How good are your tools?

It's not just the idea.

It's now you've got to make the damn
measurement.

And it's not obvious. You need very
talented people assembled for this.

Absolutely. And so that was the issue is
how good a team can you put together?

So when I learned of Ray Weiss's idea
and I saw and I knew roughly

how strong the strongest gravitational
waves would be, I knew already then that

it would be necessary to.

This would be the collision of two black
holes.

Collision of two black holes. And you
can't just summon that up. There has to

real things in the universe that might
produce that. That's right. You can't

just wish for it. But based on what we
knew about the universe at the time, I

was estimating a wave strength that was
roughly correct.

And it was at that level that you would
have to monitor the motion of these

mirrors at 10 million times smaller than
the atoms in the mirrors.

And I thought to myself, that's crazy.

And so in this book, which was published
in 1973,

we went to press just after Ray Weiss
wrote his seminal paper.

I had not yet really studied that paper
fully, but I just

knew that this was crazy.

It describes in a few words Ray's idea
in here. And then it says, I

think there's an exercise where it says,
show why this is not very promising.

Just a mild, gentle. Because it is a
textbook, right? You get to declare

Students challenged to show. Well, it
could not be a very good idea in 1973.

But fast forward a half a century.

So it is.

In 1853, flying is not a good idea,
right? That's why flying isn't a good

But that was the central issue.

If we worked for a few decades, did we
have a shot at success?

In 1973, I thought, no, no way.

But by 1975, I had turned around.

I'd had long conversations with Ray.

I'd had long conversations with Vladimir
Brzezinski, a colleague in Moscow.

I had done lots of calculations of my
own, and I came to the conclusion that

had a real shot at success if you put
together a superbly strong team and

you worked at it for a few decades.

And you need money, and you were well
-supported, I think, by the National

Science Foundation. Well, not yet. So at
that point, NSF had given Ray $60

,000 to get started.

And that's how much he had in the 1970s
from the National Science Foundation.

He also had some money from the Air
Force Office of Scientific Research. I'm

sure how much he had, or he had had that
until in the Vietnam era, they stopped

supporting science due to something
called the Mansfield Amendment, American

politics. And that's when NSF picked him
up and gave him $60 ,000.

That was a drop in the bucket compared
to what was needed.

And NSF wasn't about ready to put big
money in.

This required some members of your team
to appear in front of Congress to defend

this. That's correct.

But that was much later. The issue was
getting started.

And so how did we get started? Caltech
is a very different kind of an

institution than any other I've ever
dealt with.

At Caltech, I was able to propose to my
colleagues.

We get into this field that we build a
experimental program in parallel with

Ray Weiss's program at MIT.

So the chair of the Division of Physics,
Mathematics, and Astronomy at Caltech

set up a committee to look at it.

Committee looked at it for about six
months, detailed study, came back

enthusiastic, said, let's go ahead.

And so Caltech put private money.

about $2 million of its own private
money to get started.

And that inflates to about $12 million
today.

Private money when nobody else is
putting anything in.

You're right. That's a very different
culture at Caltech, as you described.

once that had happened, and we had
brought Ron Drever from Scotland to

experimental effort, then NSF.

And NSF stood up and took notice.

They did their own study of this and
came up with the same conclusion. They

started funding us and Ray Weiss, and it
became a Caltech -MIT collaboration.

Let's fast forward to 2016, where you
make the first detection.

You announce it in 16. You announce it
in 16. By the way, I would later learn

that when I visited the facility, in
Louisiana, you already had made the

detection.

And you'd be happy to know that everyone
was completely zip -mouthed about it

until it was official. Because I have
this huge internet following, right? And

people were totally zip -mouthed. I
swear I didn't know about it until the

release came. We were all sworn to
secrecy. Yes, yes. And so the

a first detection came from the second
facility built in Hanford.

And at that point, you have a time delay
because gravitational waves move at the

speed of light, correct? And Earth is a
finite size. And so all that worked out.

Yeah, yeah. And so it was just seven
milliseconds.

Time difference.

A second time difference because the
waves came up from the south. They

the Earth around the tip of the
Antarctic Peninsula, traveled through

It came up through the Earth in
Louisiana first, and in Washington State

second, seven milliseconds later.

And then the waves were unaffected by
all the matter of the Earth.

And they couldn't see the difference
between Earth and no Earth.

And they couldn't see the difference
between detector and no detector. They

very hard to detect. They were doing
their thing.

So what impresses me greatly, is here we
have a prediction made by Albert

Einstein in 1916 or 15, whatever. Albert
Einstein, in a little -known fact, I

mean, physicists know this, but I don't
think the public knows, Einstein laid

out the equations for the stimulated
emission of radiation, which is the

physical foundation of a laser.

He wrote that down first.

And a laser would take a few decades to
actually be built into the 1950s.

And I'm just saying, here's Einstein
predicting gravitational waves, laying

foundation for a laser, and 100 years
later, his gravitational waves are found

with lasers.

So these are crumbs spilling off his
plate.

Einstein was kind of smart.

And lo and behold, nobody's surprised,
the Nobel Prize goes to this project.

And you, along with Ray Weiss and Barry
Barish.

share the Nobel Prize. What year was
that?

2017.

So they apologized to us that they
didn't give us in 16 because we didn't

announce it until past their deadline
for nominations.

They delay anyway.

They said it obviously.

It was obvious the prize was going for
this. It was just obvious.

Hey, StarTalk fans, I don't know if you
know this, but the audio version of the

podcast,

actually posts a week in advance of the
video version. And you can get that in

Spotify and Apple Podcasts and most
other podcast outlets that are out

Multiple ways to ingest all that is
cosmic on StarTalk.

You can't be a general relativity
Einstein guy without being a black hole

So forgive me for asking you to...

retell a story you've probably told a
thousand times.

But there's some famous bet you made,
was it with Preskill, with some other

physicist? Preskill and Hawking. And
Stephen Hawking.

By the way, I was at the University of
Texas when Preskill was there. I think

was like a postdoc or something. He was
just starting out.

That's how old I am. I'm an old guy.

You're a young kid. I'm an old man.

So you made a bet.

And let me see if I can.

set the table here.

A black hole, once we all agree that
they exist, we can ask other questions.

When you have something outside the
black hole and it falls in, what happens

that information that was contained in
that object?

Is it gone forever and is that okay?

Because information theory was a whole
branch of science, shall I call it

science, that was rising up at around
the same time and entropy.

became a buzzword among many.

So what was the bet and how was it
ultimately resolved?

The bet was between Stephen Hawking and
me on one side and John Preskill

on the other side.

It was over whether or not information
does get lost in black holes.

And why is that so bad?

Okay, so it's bad because

the fundamental laws of quantum
mechanics as they are normally

Physicists are widely agreed that
quantum physics is fundamental

and that quantum physics underlies all
of physics.

It's the most successful theory ever put
forth of the universe. And classical

physics, where there are not these
quantum fluctuations, there are not

probabilities.

That arises from quantum physics as an
approximation under ordinary everyday

circumstances. There are many people who
caricature science, physics in

particular, by saying, well, we used to
think classical physics was it, but now

we discard it in favor of quantum
physics. But that's not true.

No, quantum physics absorbed, as well as
relativity, general relativity,

absorbing Newtonian gravity.

It's not discarded. It's a bigger
understanding, a deeper understanding.

I just want to emphasize that. Many
people get that confused.

So quantum physics is normally
formulated, is almost

universally viewed, has built right into
it from the very beginning

the fact that information cannot be
lost.

Now, these words, information cannot be
lost, are a translation into everyday

language of something else, which is not
everyday language, which says that the

evolution of everything in the universe
is unitary.

And so those are buzzwords that are not
part of the normal lexicon. But I want

to say, just to say that, to indicate
that there's...

Some very, very extremely precise
version of this, of which information is

lost, is a colloquial way of saying it.
Okay. But it would represent a violation

of some fundamental tenets of quantum
theory. That's right.

Stephen Hawking, back when he was
visiting Caltech.

Who, by the way, we've interviewed for
StarTalk in our archives.

Check it out.

In 1974, 70.

He spent a year in my research group at
Caltech.

We were very close friends.

And during that period, he having
discovered something called Hawking

which is a very slow evaporation of a
black hole that emits radiation and

evaporates.

He then, while he was here, began to
look much more deeply at quantum theory

black holes.

And he came up with a prediction that
information really is lost.

And when black holes evaporate, you
could form a black hole.

If you waited long enough, much longer
than the age of the universe for normal

black holes, the black hole would
evaporate and all the information that

into the black hole would be gone. The
black hole would be gone. You just

lost the information that no longer is
there.

And that was...

Complete violation of the normal tenets
of quantum mechanics.

And yet he was claiming that that was
true.

He wrote a paper on this with all the
technical details.

He couldn't get it published.

It was so obvious. It had to be wrong,
but nobody could see anything wrong in

his calculation.

And so he had to fight for more than a
year to get it published. If you look at

this paper.

You see the submission date. As all
research papers give you. Yeah, they

you a submission date, and then you
usually have a revised date, and then

published. There's no revised date.
There's a submission date, and the

publication date is like nearly a year
and a half later.

He fought for a whole year, more than a
year, to get this thing published.

And physicists have struggled with this
ever since.

And those of us whose roots are in
relativity tended to believe Hawking.

And those of us whose roots were in, who
grew up with quantum mechanics instead

of relativity first, those of us who
were enamored of relativity tended to

believe Hawking. And so Hawking and I
made this bet with Preskill, whose roots

were in.

And he's the junior of you both, right?
He's the junior of us all. He's a young

whippersnapper coming up. He is now the
Richard P. Feynman Professor of

Theoretical Physics at Caltech.

I'm the Richard P. Feynman Professor of
Theoretical Physics Emeritus.

Emeritus, okay.

I'm a young whippersnapper. Oh, man,
don't take your job in a minute. So I

turned the chair over to John.

I mean, John is brilliant. He's a hell
of a lot smarter than I am.

A hell of a lot smarter. Anyway, so.

So we made this bet, and this was in a
period when Hawking was starting to

Caltech for typically three to six weeks
every year. Was he yet wheelchair

-bound? Oh, yeah. He was wheelchair
-bound going way back to about 1970.

Okay. And this is 1990.

Oh, whoa. Much later. Okay.

We made the bet around 1990.

So the stage is set.

The cage match is set. You and Stephen
Hawking, titans in your field, in your

subject, conclude, yeah, information is
lost.

Especially if Hawking radiation, you can
evaporate the black hole and everything

is gone. There's no memory of what was
there. Preskill is declaring that

information is not lost and his roots
are deep in quantum physics, which we

has never been shown to be wrong.

And they're both smarter than I am, and
they both know a lot more about quantum

physics than I do.

Because we'll return to this, but let me
just explain that through my whole

career, I've thought that quantum
gravity, combining general relativity

quantum physics, was the most important
area of physics of all. But I also made

a decision when I was very young, I will
never work in quantum gravity because

the field is too crowded.

There are too many smart people there.

I'm smart enough to pick really
important problems that I can solve that

else is working on.

And they'll only figure out later that
I'm right, that those problems are

important. But I won't touch a problem
wherever it is. We've got a million

people in the room. There's just too
many smart people in the room.

So anyway, so they have now agreed that
information is not lost.

So Hawking conceded, and by association
with you, or have you still a holdout on

this? I'm still a holdout.

Okay. And what led to this concession,
if I understand correctly?

So he, Stephen, together with a student,
was working on an

idea for how the information might be
recovered.

And he basically said that...

In quantum physics, if you form a black
hole and then it evaporates, there's

also a tiny probability the black hole
never formed in the first place, and the

information sneaks out through the root
where it didn't form in the first place.

I'm sorry, that sounded like a cop -out.

Yeah, it does sound like a cop -out, but
it's very clever, and it's in keeping

with how physics works.

But it's not obvious that it's right.
But it's conceivable that this is what

happened. What about the idea?

So maybe I've misunderstood.

So I've got to go back to see where I've
said this, even publicly.

I thought as the black hole evaporates,
because the energy, the gravitational

energy in the vicinity of a black hole
can spontaneously make a pair of

particles. And one particle escapes, the
other one falls into the black hole.

And this just keeps going until there's
no black hole left.

But the particle that escapes, if you
inventory those particles, they're real

particles. And don't you recover all the
particles that went in in the first

place? You recover all the energy.

But not the inventory of particles. You
don't get the same particles

necessarily. Okay, then I misunderstood
that.

I think I've been wrong.

I thought you get particle for particle.
They come out, which blew my mind.

I don't think, certainly there's no
proof that that's the case. Certainly no

proof that that's the case, and I don't
think it is the case. Okay, so you guys

lost the bet.

Well, no.

Hawking concedes the bet. Hawking
concedes the bet. And what was at stake

this? The loser will give the winner an
encyclopedia filled with information.

that somehow escaped the black hole.

So information is the penalty gift.
That's right.

Stephen Hawking conceded the bet at a
big international conference on general

relativity and gravitation in Dublin,
Ireland, in early 2000.

Were there gaffes in the audience? There
were rumors that he was going to

concede. And so there was a big ceremony
that I played some role in the

ceremony, but I didn't concede myself.

And so Stephen gave Preskill, who's a
big baseball fan, an encyclopedia

of American baseball.

Oh, any kind of encyclopedia. Well, that
was his idea.

That's clever.

And less expensive.

Yeah. I didn't concede for a peculiar
reason.

there is an alternative formulation of
quantum mechanics in which information

could be lost. It's due to Feynman,
called a sum -over -histories

And as I say, I don't work in quantum
theory in

any deep sort of way. I do in terms of
quantum technology, which we needed for

LIGO, but that's a separate story.

Two of the very deepest physicists in
working in

quantum theory of my lifetime were
Murray Gelman and

Jim Hartle.

Jim Hartle at Santa Barbara, Gelman at
Caltech, and then he moved to the Santa

Fe Institute in retirement.

Gelman is credited with...

proposing quarks as the fundamental
particle of... The giants of theoretical

physics when I was a young physicist at
Caltech were Gelman and Feynman.

Two colleagues of mine that I enormously
respect.

So Gelman and Hartle took Feynman's

path integral or some of our history's
approach to quantum mechanics and they

developed it further in a form that they
could apply it to to the universe.

And then they, Hartle has used that to
study quantum

cosmology, the quantum mechanical
description of the birth of the universe

how it has evolved.

That particular approach to quantum
mechanics, Hartle took it and he showed

that approach can deal perfectly well
with information loss.

And it deals with it, it arises because
of what we call closed time like curves.

There's a certain probability for
backward time travel in quantum physics.

In this Feynman -Galman -Hardell
approach,

there's a certain probability for
backward time travel. And if you can

backward time travel at the quantum
level, then you lose information.

And there's sort of an elegant
mathematical formulation here. Quantum

so weaselly this way. Well, that's not
the standard version of quantum

mechanics, but that was the version that
Feynman and that Hartle and Gelman

needed in order to do the quantum
mechanics of the entire universe and the

of the universe.

So we're getting into this issue of the
birth of the universe and quantum.

quantum gravity here.

And I am rather enamored of this
approach, although I don't

do it. I just look on the sidelines and
admire these people who are smarter than

I am and who have the courage to work in
a crowded field.

But I'm just so impressed with this and
with the fact that within that

formulation you can lose information.

Is that the start of a formulation that
will one day marry general relativity

and quantum physics? Well, it does do
that.

It's not... It's knocking on the door.
It's knocking on the door.

So remind me, now, you're Professor Horn
in this

question, what is the problem with
general relativity not melding together

quantum physics?

What is the real holdup there?

Well, the real holdup is that they are
logically incompatible with each other,

and so something has to give.

And that's because general relativity
requires space to be continuous.

You have a continuum space, and it's a
very definite space. It's not a space

where you have a certain probability
that space is warped in this way and

another probability it's warped in that
way. In fact, there are no probabilities

at all. Yeah, there are classical
probabilities, but not.

Quantum. Not quantum probabilities. And
so at the smallest scale, they're

incompatible. The smallest scale,
they're incompatible in any place where

gravity becomes extremely strong,
they're incompatible. So the smallest

they're incompatible even here in this
room, but also they're incompatible in

the birth of the universe when gravity
was extremely strong. They're

incompatible in the core of a black
hole.

Our gravity is extremely strong.

They're incompatible.

If you try to make a time machine,
Hockey and I independently with our

have identified a process whereby if a
very advanced civilization tries to make

a time machine, it will quite possibly
explode at the moment you try to turn it

on.

And that's also controlled by these laws
of quantum gravity.

So that's why we haven't seen any.

time travelers yet. That may be the
reason. They're all dead trying to turn

the machine. That's right.

What you're saying is Einstein puts
forth the general theory of relativity,

which is so successful in so many
realms, and it picked up where Newtonian

gravity failed, yet we must confess or
concede that there's a limit to

how far general relativity goes,
although we've yet to find a limit to...

quantum physics so the betting the
betting pool will say general relativity

going to succumb to quantum physics in
some way yeah that that's one way to say

it they certainly there is the s
incompatibility between the two and

theorists are trying to be the they're
like performing the shotgun wedding

between the two branches of physics
somehow yeah and i i do think again

in from the outside since i've chosen
not to work in this field String theory

likely to be a successful route into the
correct laws of quantum gravity. Yeah,

but they've been at it for 50 years. Oh,
yeah. 40, 40 years. That's not very

long. Come on. I'm 84 years old. Come
on.

That's just a drop in the bucket. Come
on. Wait, but Einstein went from special

relativity to general relativity in 10
years.

Kepler went from weird nested solids to…
The Kepler's three laws of motion

in 10 years. And that's lone scientists.
We've been working to try to do

controlled fusion for a lot longer than,
more than 50

years. LIGO took 50 years from the time
I first started working on gravitational

waves until we succeeded. It was 50
years.

Some things take a long time.

Yeah, but LIGO is a machine.

The merging of quantum physics and
general relativity are ideas.

Could it be, and I've said this, I don't
want to say this to you because you're

Kip Thorne, but I've said this to Brian
Green, okay? Because Brian Green is like

my generation.

I said to Brian Green, I said, Brian,
you've been working on string theory for

decades.

Maybe all of you are just too stupid to
figure it out and we're waiting for

someone else to be born into this field
to then solve it and went into the ways

none of the rest of you can.

None of them are saying, I'm too stupid
to figure this out.

Let me choose another profession.

No, they're saying the problem is too
hard. And if you go 40 years of really

smart people not figuring something out,
that tells me either they're barking up

the wrong tree or none of them are smart
enough.

Am I overreacting here? I think you have
to remember that we do build on each

other. None of them by themselves are
smart enough.

Okay. But the community, again, it's
like...

This Nobel Prize really belongs to a
thousand people. It doesn't belong to

With the genesis in Joe Weber.

With the genesis in Joe Weber.

Newton spoke of standing on the
shoulders of giants, and that really is

If I can see farther than others, it's
because I've stood on the shoulders of

giants who have come before me.

And that's the nature of science.

The struggles that our colleagues have
been having with string theory and M

-theory and quantum gravity, we've
learned an enormous amount.

It shows it's very promising, but it's
going to continue on into the next

generation before the ultimate success
is had very, very, very probably.

Those are like final words right there.

I've heard rumor that whichever faculty
of Caltech gets a Nobel

Prize, they get a parking spot with
their name on it.

Is that true?

At Caltech, a Nobel Prize does not get
you a parking spot with your name on it.

You have to pay for the parking spot
just as much as you do without a Nobel

Prize. That was such a fun rumor,
though. I heard that.

That's true at USC, but it's not true at
Caltech.

Okay. Because there's just too many of
you all running around with Nobel

The parking spots are too valuable.

So true at USC. Yeah, it's true at USC.
All right. So you're 84. You have 84

years of wisdom.

coursing in your veins and arteries. Are
there any projects you're working on in

the next several years?

So I made a gradual transition,
conscious, away from science,

away from scientific research, beginning
around 15 years ago.

Oh.

I would like to believe I can live to
110.

That's my...

intended goal.

And so for the next remaining decades, I
wanted

to do things that I really enjoyed. And
I've enjoyed science.

I've been a conventional Caltech
professor for half a century.

Enormously enjoyed it. Enormously
enjoyed working with students.

I trained over 50 PhD students who did
far more important research than I

did.

Been there, done that.

And I have worked in all these areas of
science, and I've had enormous fun, but

I've turned them over to the younger
generation, and they're smarter than I

Okay, so what are you, surfing now, or
skydiving? Okay, you're taking up

other... So I decided that I would like
to spend a few

decades doing creative work at the
interface between science and the arts.

Oh. So Interstellar is an example. That
was going to be released in September,

and then they delayed it to the holiday
season in December.

So the re -release of Interstellar. The
re -release to December 2024.

That's right. That's right.

That was enormously enjoyable.

From that, I learned how great it can be
to collaborate with

somebody as brilliant and as completely
different than I am, Christopher Nolan.

So my most recent collaboration has been
a book of poetry and paintings with

Leah Halloran about the warped side of
the universe and my poetry, my

attempts at poetry and her paintings,
but just trying to see whether it's

possible by tightly integrating
paintings with verse to convey

the essence of issues in science.

the essential features without conveying
the precise details.

No, that's not the right genre for
precise details.

But anyway, so I've been enjoying that.

By the way, I've always felt that way
about Van Gogh's Starry Night. Yes.

Where you look at that painting and you
say, this is clearly not what he saw,

but it's definitely what he felt.

Yes, yes. And you get to experience the
universe through his own lens.

Yes. And so I've always appreciated art
when it plays that role.

I have a second movie that's been in the
works for more than a decade. Can you

tell? Well, it's just something that I
started with Stephen Hawking and Linda

Obst, who is my partner on starting
Interstellar.

It is wonderful to work with.

That movie might never get made. I'm not
going to tell you what it's about,

aside from the fact that it's sci -fi.

And it's solid sci -fi. That's how it's
built in from the outset.

So if that does not work out in the end,
then I may try turning it into a

novel. I've never tried to write a
novel. I don't know whether I can, but

would be fun to try.

And actually, the thing that I have put
almost...

A large fraction of my effort and the
lion's share of my effort since the

beginning of the pandemic is a history
of the LIGO project, the LIGO

gravitational wave project, because that
is, I think, pretty clearly the

technically most difficult thing that's
ever been done by physicists.

By anybody.

By anybody. Yeah, probably by anybody.

One one -hundredth the diameter of a
proton? That's anybody.

And success.

required both amazing, developing
amazing technology, new technologies.

It required developing computer
simulations of

colliding black holes, required
developing quantum precision measurement

technology that is now in LIGO and
playing a major role where you

what's called the Heisenberg uncertainty
principle.

My mind is still partly blown by having
By you having said that, you're

bypassing Heisenberg's uncertainty
principle. Yeah, that's right. By

manipulating vacuum fluctuations, just
like advanced civilizations

might do as a routine thing. So we
developed this new

area of technology for Eichel.

But it was also a very political thing.
How do you get a billion dollars of

taxpayer money?

for a field that didn't exist when you
began.

And should they bet on you and not
someone else? That's right. And plus, I

you even had naysayers, if I remember
correctly.

Colleagues would say, this is a pipe
dream.

We had political battles in Washington.

Yeah. Tell me who the naysayers were. I
got people to take care of them. They

were some of the leading astronomers.

I got people to take care of them. You
want my people to...

No, they've come around.

You think? Okay.

They've come around because this is so
exciting now that LIGO succeeded.

But the sociology of the transition from
small science to big science is a very

rocky process. And that's the right
word, sociology, because that's what it

I don't like working in a big science
project. It's not for me.

It's like working in a crowded field.
It's not for me.

But this had to make the transformation.
It wouldn't have happened otherwise. It

wouldn't have happened otherwise.

The genius of Barry Barish in making
that happen and the genius of Robbie

in getting us partway there at the very
beginning is our initial director, who

was the one that sold it to Congress and
really got us going.

It's a very complicated story, and I
have a set

of...

five collaborators that have been
working on this history.

We just finished draft six and sent it
out to like a colleague to comment on.

And I have been getting back huge
numbers of comments and it'll take me

years, I think.

So anyway, this history, because of the
nature of this project, it's a very

interesting, complex history that is
quite important for the history of

Especially when you consider Most people
knew nothing of LIGO until they see the

headline that it discovered
gravitational waves.

And why would they have any thought of
what challenges preceded that?

You know, they just read the result. Oh,
scientists discover this.

Well, how about the, like you said, the
politics, the sociology.

The genesis, who's standing on whose
shoulders, who are the naysayers, all

has to be overcome.

The international collaboration, key
input from the Soviet Union in the

of the Cold War.

And it's just a fascinating story and

enormous fun.

You know, Arthur C.

Clarke said, he said, in space where
there is no air.

A flag will not wave.

So maybe the universe is not a place
where we should be waving flags.

Collaboration is what gets you there. I
like that.

So Kip, this has been a delight. Thanks
for making time.

A lot of fun.

For StarTalk.

I look forward to the release of, the re
-release of Interstellar.

We were recording this before that has
come out.

You already know this, but let me
reaffirm that that film just took people

ride far beyond anything they had
imagined.

It had kind of an impact on people in
the way 2001 A Space Odyssey did. It was

mysterious, it was modern, it was the
future, but it was still relevant.

But it left you with more questions to
ask than questions answered. And you

want that, I think. Yeah, and that
was...

Really, the genius of Christopher Nolan
taking some science that

he and I had put together, but combining
it with a human story that was

powerful.

And with marquee director and marquee
actors that made sure it would get

noticed. And music.

Yes. I went to a concert by Hans Zimmer.
That was Hans Zimmer, yes.

Just, I think, the night before last.

And he, but I didn't know there, but he
basically said that certain

pieces of the music in Interstellar were
as close to perfection as he has

achieved. Wow. I'm going to give it
another listen. Because there is no 2001

without its musical track. With the
Strauss waltzes, the... This is very

different. I mean, it's all Zimmer's.

original music and it's a remarkable
score uh just amazing i'd look forward

to your next 25 years when you live to
110 uh maybe we can do a reprise of this

conversation we'll check in on that see
how you've been coming along dude thanks

a lot thanks great to see you again
thanks this has been a special

exclusive one -on -one between star talk
and hip thorn Nobel

laureate, even let me touch his medal.

First time I've ever touched a Nobel
Prize.

Well, the medal that really belongs to a
thousand.

The medal earned by a huge team, as he
humbly declares.

And as we enter a new era of science,
where collaborations are really how this

works, especially where you have
international collaborations, you have

scientists getting along, even at times
when the leaders of their countries are

in conflict. That's just messed up.

That's messed up. I'm Neil deGrasse
Tyson, your personal astrophysicist for

StarTalk. As always, I bid you to keep
looking up.