All language subtitles for Black.Holes.the.Edge.of.All.We.Know.2021

A black hole
is stranger than anything

dreamed up by science fiction writers.

A region of space

where gravity is so strong

that nothing can escape.

Once you are over the edge,

there's no way back.

Wow.

It never ceases to get me,
seeing these two mountains up here.

It's a bit deceptive.

It looks as though you can just hike up
there in a couple of hours.

But that is a big
elevation shift from where we are now.

I was not a boy astronomer,

I didn't have a telescope growing up...

but I do remember seeing
what a black hole was.

I thought there are
very interesting things

in the universe to be explored.

The Event Horizon Telescope
is a new instrument

that a global team is assembling...

that will have
the magnifying power to resolve

the region immediately
around a black hole.

That's never been done before.

We are chasing down
something that struggles

with all of its might to be unseen.

And we're saying "we're gonna catch you".

When you get to about 15,000 feet,

you're-you're above
quite a bit of the atmosphere.

You really need to be above
the atmosphere to see through

to the emptiness of space.

The goal of the Event Horizon Telescope

is really easy to state,

we're gonna take
the first picture of a black hole.

What I had yesterday as of noon,

was every part of the system
of the front end working...

We've come to
the LMT here in January

specifically to do
what's called a dry run.

And we're discovering problems.

Then, we tried to replace the Gunn,
now we've lost power,

and that's what we're
troubleshooting upstairs now.

Today I'm going to try to get
the Gunn working again, the old Gunn...

But if we went back
to this old Gunn...

then...
- Yeah.

we're still compatible with the EHT...

By doing a double-down conversion. Yes.
- for January and April.

April is when we're going to have
all the telescopes around the world,

the full EHT working,

and it's our best shot
at imaging a black hole.

But before we get there, we've got
to make sure that everything is working.

So the first goal is to try to get
the 232.1 gigahertz

working again with the old Gunn.
- Yeah. right.

If that doesn't work...

My plan B... My plan B...
- then what?

is that...

The larger the telescope,
the better it's able to see tiny objects.

To resolve the black hole
in the center of our galaxy

or the bigger black hole in M87,

we need a telescope
nearly the size of the earth.

Well, that's clearly impossible.

So we do the next best thing.

We take telescopes
scattered around the world

and make them all look simultaneously
at the black hole.

Imagine taking a mirror

and smashing it with a hammer

and distributing these shards
all over the world.

And then recording what happens
on each of those shards

and then bringing them together

and reconstructing that mirror
in a supercomputer.

That's what the
Event Horizon Telescope is doing.

So at every site,
everything has to work perfectly.

I think this thing took quite a hit.

In shipping?

If it turns on and it smokes then
we'll know there's something wrong.

Yeah.

We still have to make some tests.

Tomorrow we are going to trigger
a real observation.

And that's gonna involve
the South Pole, Spain, Chile,

and God willing, the LMT.

You've got a clock ticking.

I know.

Cue the Mission Impossible theme.

Look at-- That's the telescope,
buried underneath that

uh, SHIT, if I may say so.

Wait, what happened here?

What-What happened?
- Weather happened to us.

Wait, you're shitting me.

Last 16 hours it's been beautiful

and as soon as we come up,
like the gods hammer us?

That's crap.

Well we can't point and focus
through this weather right now

The schedule is supposed to start

In 40 minutes...

In, uh, 35 now.

If we're still in the clouds
and it gets really cold,

it's going to be an ice situation.
- Yeah.

That's a possibility.

That's what I'm worrying about.
- Yeah, I'm really worrying about that.

Everybody cross their fingers,
use your favorite incantations,

and we'll clear through this.

Okay, so we're gonna
set levels in the other room

and then we'll be ready to go.
- I need to adjust the power level

of the upstairs a little bit.

You realize
that we're firing this thing off

in exactly 14 minutes and 15 seconds.
- Yeah, yeah, yeah, I know but...

Ah, jeez.

Did you say 6573?

So it's RCP and LCP high, right?

We got one minute.

Here we go, people,
hold onto your hats.

Okay, we're ready.

Four, three, two, one, zero!

Blast off.

Oh boy.

What is a black hole?

It is so deep,

it's so hard to fully appreciate
all of the physics that's going on.

You can spend your life studying this.

Imagine an object
where gravity has become so strong

it has compressed all of the material

with which it started down into a point.

This object develops
what's called an event horizon.

And this event horizon
has this amazing property

that it's a one-way street.

You can go from the outside to the inside,
but nothing will ever get out.

The gravitational pull is so strong

that anything that comes close enough
to it will just vanish inside.

If something disappears
over the event horizon it's gone.

And we no longer
have any knowledge of it.

It is no longer detectable,
it's no longer knowable.

It might still exist,

it might not still exist,
we have no way of knowing.

We have a contact
with a kind of phenomenon

that we don't fully understand.

It's like a vortex
in the universe in space and time.

The darkest object we can imagine
mathematically fundamentally

emits no light, reflects no light.

But it becomes the engine

of the most powerful events
we now observe in the universe.

There's something about them

that really pushes the mind.

Can you hear me?

Yes.

It is said that fact
is sometimes stranger than fiction,

but nowhere is that more true
than in the case of black holes.

Currently I'm working
with my Cambridge colleague Malcolm Perry,

and Andy Strominger from Harvard,

on a new theory to explain the mechanism

by which information is returned
out of the black hole.

Watch this space...

I met Stephen in 1982.

Over the years we coincided on a number
of topics, a surprising number,

but the very kind of intense thing
that's grown over the last,

what is it now, three years? Yeah.
- Three years. Yeah.

Has been a whole new, wonderful level.

And quite different.
Quite different, yeah.

It was a fabulous warm day,

kind of unusual in England for April,

so we had a lecture outside.

This was in a place
called Great Brampton House.

For the last 10 years, Stephen
and friends organized a small retreat.

I had these ideas about

the structure
of the edges of infinity and...

how they could store information.

I was simply listening
to this lecture and I felt

that the phenomenon he was describing

could be happening
on the surface of the black hole.

Stephen picked up
on that immediately.

He said, this is it, this is the piece
that we've been missing.

He is very eager to unravel the paradox

that he unleashed on the world in 1975.

Something called
the information paradox,

which basically says that black holes
annihilate information,

which should not be possible.
That's the paradox.

It implies that there's a breakdown

of laws of physics
in the presence of black holes.

This is why
we're chasing this problem,

because if information is lost,
then that contradicts

almost everything we know about physics.

Something's gone wrong
understanding how black holes work.

From the outside you can't tell
what is inside a black hole.

When you look at a black hole,
all you can tell about it

are its mass, its charge
and its state of rotation.

And that's the same for any black hole
no matter what it was made out of.

This means that a black hole contains
a lot of information

that is hidden from the outside world.

That was a very weird thing people
to get to grips with and then

Stephen Hawking made
this amazing discovery

of Hawking Radiation, that says actually

stuff comes out of a black hole,

and that's where
the problem really started.

It turns out
they're not black, they radiate.

And as they radiate they lose mass
and eventually disappear.

An equivalent mass of elephants
could form a black hole,

an equivalent mass of Encyclopedia
Britannica could form a black hole.

The black hole evaporates
and what's left behind

is the same sea of Hawking Radiation.

It appears that the information
about what fell in is lost.

The particles that
come out of a black hole

seem to be completely random

and to bear no relation to what fell in.

If what Hawking said were correct,
it can spit out anything.

It can spit out a piano,
it can spit out a trombone, it--

It can-- Anything can come out.

That means that
the basic nature of the universe

is just random.

There aren't really physical laws
which govern the entire universe.

This is every physicist's nightmare.

Much of our knowledge of the universe

is grounded on

our belief that we can reliably predict
using the laws of nature.

We have a physical theory,
we make predictions using that theory,

we do experiments or observations
to see if those predictions were realized.

We understand the early universe
by using the laws of physics

to predict backwards and say
what the world must have been like.

If those laws break down,

it's about the limits of knowledge.

What sorts of things
could we possibly know about the world?

If the predictability
of the universe

breaks down with black holes,

it could break down in other situations.

Even worse, if information is lost,

we can't be sure
of our past history either.

The history books and our memories
could just be illusions.

It is the past that tells us who we are.

Without it we lose our identity.

Since I was a graduate student,
the information paradox

has been central in my thinking.

It's a sort of 24/7 thing.

I get up, I make myself a cup of coffee,
I sit down with a pad of paper.

I'm thinking about it
when I brush my teeth,

dream about it.

It is the most interesting,
well-posed question

in modern physics.

So interesting that

I was ready to devote my life
to trying to understand it.

In the 40 years
since Hawking's argument...

By the way,
while, while Malcolm's erasing...

There's certainly been
thousands of papers

about how the paradox might be avoided.

None of them has gained

universal acceptance

and they all are problematic
in one way or another.

So the magical formula I think

I could write out in excruciating detail.
- Yeah.

So while Malcolm's writing, um...

what we've done
is first of all worked out...

But now, Stephen, Malcolm
and I have found a mechanism

by which the information paradox
might possibly be resolved.

Wow. Seems very exciting.

It's the beginning of something deep,
we really quite don't know what...

Investigating this
is vigorously underway now.

But central terms of what...
- What is the super rotation?

So, the super rotations,
so ordinary BMS group

Physics is about finding the truth

about the universe.

We might not ever get all of it...

This then gives us a conservation law...

but I think
there's a good shot that, uh,

in my lifetime, we'll nail this one.

And so that's conservation
of super rotation charge.

Now, let me erase here...

Seeing is believing.

That's the most credible and the most
powerful sense that we have.

We need to see things.

We long to see things.

In my mind, like for 10 years,
there's no question there is a black hole

and there's no question it's possible.
I still want to see that stupid image.

I want to see it.

We have never actually
seen the telltale sign of the black hole

which is that virtual region, the horizon,
from which not even light can escape.

With the Event Horizon Telescope
we're going to zoom

all the way to the size of the horizon,

and see if it will cast
a silhouette, will cast a shadow.

The Event Horizon Telescope
is the culmination

of really decades of work.

Once we began
to realize that we could make an image,

that became fascinating.

So over the past years
we've gone to new sites,

and we've had to convince those
new sites that the science is worthy.

We've had to develop
and install very specialized

and expensive equipment
at all of these sites

in all of these extreme places.

We are now at the moment when
we'll be doing our first observing

with the chance of making an image.

That's still a question mark but

local wisdom is a go.
- Yeah.

SPT weather good, no-go for pointing.

Pointing issues.

SMT technically ready, weather forecast

possible of high wind
but unlikely to cause anything.

So night's outlook
is good, right?

Yes.

We set up telescopes around the earth
that can talk to each other,

that can record data in tandem,

so after the fact
we can combine these data

and make it act like
they were actually one telescope.

Right now, the Event Horizon Telescope
is an array

of eight dishes across the globe

from the South Pole
to the Arizona desert to Hawaii to Chile

creating, effectively,
an earth-sized telescope.

Weather forecast is good for Pico.

I mean, they say excellent, so...

Looks pretty good to me.
- I'm changing this to .2...

I'd like to see the LMT water vapor map.

When you have a single facility,

it's the weather above that one telescope

that has to be perfect
for a night's observing.

Now imagine you need perfect weather
at every single site around the array.

By the time we start observing,
it's going to have moved past

but we don't know
what else is going to move in.

Seems to be accelerating.

Right.
- So SMT is getting worse.

So what are the pinch points here?

It's really just LMT and SMT,

and we're gonna have to make
a decision based... at South Pole,

just based on what we know now
which is they might have pointing issues.

LMT, how worried are you
about the maser?

I'm a little worried about the maser

just because we haven't done
some of the tests that would let us...

see how good it is.

Shep, it's 3:30, we have half an hour.
- Yeah.

Should we call it?

I basically think
that we should trigger for tonight.

I think it's probably
the best weather we're gonna get,

technical issues are breaking our way.

I mean, of all the nights
to have a question mark

by South Pole this is the one to have it.

Yeah.

Um...

We'll get some pretty good
M87 scans, one hopes, right?

So let it be written, so let it be done.

I will make the decision,
I will broadcast it.

Night five, track D is a go!

May all future nights
be as good as this one.

And then, all around the world,

all the telescopes swivel at the same time

and we will begin to record photons
from the black hole.

How big a black hole looks
in the sky is a combination of its mass

and how far away it is.

The black hole at the center
of our galaxy, Sagittarius A-,

has the largest angular size in the sky
followed by M87.

M87's black hole
is a thousand times bigger

but roughly a thousand times farther away.

They turn out to have
pretty comparable sizes in the sky.

This is central command,
it's always manned 24/7.

Uh, people write in and they say
I'm having an emergency with

one of my recorders,
or my receiver, or something.

We hope to be bored.

We hope that there's nothing to do

and that everything is going smoothly
and that nothing goes wrong.

But you know, we're here just in case.

We've just finished Day Three
of the EHT observations.

It's been unprecedented.

We triggered three consecutive
nights of observing

and that's because
the weather has been phenomenal.

And the team is quite tired

because we've been working
round the clock for three days.

They're at high altitude sites,

they're paying
a lot of attention to detail,

they're under a lot of stress,

they're trying to run down problems,

and we're pushing people
to the limit at this point.

Final scan
of Sagittarius A- begins.

This is it, oh yeah,
so this is it. The final scan

of the 2017 observations

on Sagittarius A-.

♪Somewhere over the rainbow ♪

♪ Bluebirds fly ♪

Did you write that "woohoo"?
- Yup.

♪ Dreams that you dream of ♪

♪ Dreams really do come true-ooh-ooh ♪

♪ Someday I'll wish upon a star ♪

♪ Wake up where
the clouds are far behind me ♪

♪ Where ♪

I think this song just really captures
how good it is to realize something

that you've been working on for ages.

How long?

I've been working on this for...

I don't know, 20 years.

Next at every EHT site, everybody
will pack up the hard disk drives

carefully, very carefully,

ship them back
to the central processing facility.

Wait. Guys, we're done!

We just finished...
We've finished the whole thing?

We're done, it's a wrap!

We just finished the entire scan,

and the entire schedule,
and the entire campaign,

and the entire Event Horizon Telescope

observations for this year.

The great challenge
for the Event Horizon Telescope

is only when you get all the data back
to the central correlation facility

do you truly know that everything worked.

And that will take over a month.

Until then there's always this tension,

there's always this slight uncertainty
that something's been overlooked.

So May, springtime, rebirth,
imaging black holes,

it's gonna be quite a summer,
I'll tell you that.

It's been
a perennial question

in the philosophy of science,

if what we're primarily
interested in are phenomena

as they can be detected experimentally,

how, in fact,

do we come to have knowledge
about unobservable entities?

I've always had a pull
towards the invisible

and the mysterious.

I've sort of naturally gravitated
to black holes.

But a black hole is very, very hard
to understand with just the equations.

If you really want to know anything
at any level of detail,

you're not going to do it
with just, just pure mathematics,

it's not going to happen.

You need to simulate it on a computer.

You have what's called an accretion disk
that's orbiting the black hole.

It's chaotic.

It's ionized gas,
it's got magnetic fields,

the whole thing is churning.

The gas gets hot and then it radiates.

That gets a little too complicated

for a theorist to calculate
with pencil and paper.

Simulations really
help us make what is invisible,

what is unseen, seen.

It must be Andy.
- Hiya.

We have almost incredibly good news.

What?

But not quite.

There's a missing link somewhere.

If you don't worry about it
you get the right answer.

Oh well, I never worry, so...

Once a year,
Stephen Hawking and his friends

take over some house somewhere,

where we can exchange ideas,
where we can have fun,

where we can go off into
the mountains and have a hike.

Stephen arrived.

Stephen's here, great.
- So if you go

all the way that way,

you can say hello to him.
- Okay.

Stephen, Sasha, Malcolm and I found
a chink in the armor

of, uh... more than a chink,

a huge gap in the armor
of the information paradox.

Why don't we use the blackboard in there.
- All right.

The old story was...

there just wasn't any way that
a black hole could store information,

it was just a hole in space.

What we've discovered
is that the horizon

does have some properties
that encode information.

Namely, the supertranslation
and the superrotation degrees of freedom,

what we now call the "soft hair"

Okay.
- Uh oh, put it round.

The hair is spread
around the horizon of the black hole.

When you throw
something into the black hole

you change its hairdo.

So you start like this, you throw
something in, it goes like that.

We discovered there's a record
of what fell into the black hole.

Some information
is definitely transferred.

We don't know yet if all of it is.

And that's really what we are currently
trying hard to investigate

It looks like this.
- Yeah.

It only contains, um, with two derivatives

in epsilon, so that'll vanish.
- Okay.

We need to see if this soft hair
and these soft particles

can encode
all the information in a black hole.

Okay, so we're not worried
about that term.

No.
- Did you look at that term, too?

There's a formula,

by Bekenstein and Hawking
in the early '70s

for exactly how many

gigabytes of information
can be stored in a black hole.

So the very first test,
which we have not yet passed,

is counting the information
using the soft hair

and showing that it gives
exactly the right answer.

If we can get
the central charge to be 12J,

information is not lost.

Information is conserved,

and that we'll be able to trace
this information

by looking at the horizon.

And we've spent about
three months getting zero,

then another three months
getting infinity,

and the last few weeks, Malcolm

thought he got 12 and now we think
that's actually wrong again.

As of today, we have 12,

but with a dubious step.

Are you saying
that that integration by parts

was done to get this last formula?

I have a feeling.

Yeah, because there's no terms
with two derivatives on zeta.

Well, the whole point was to get rid
of two derivative terms on zeta.

But maybe they're really there.

What-- Um, let's see, uh, okay.

So I think we need to think
a little more about this. Um...

Oh, Stephen's here. Saved!

Hello, Stephen!
- Hi, Stephen.

Hello, Stephen.

Why don't we give Stephen
the executive summary.

Assuming everything is right.

To be confirmed.
- No, no,

you never assume everything is right.

To be checked, everything to be checked.
- Yeah. Everything to be checked.

You know, it's the usual roller coaster,
a few minutes ago we were very excited

because the central term
came out on the nose

exactly what it needs to be
to get the, uh, area law,

then we realized we...
we might have missed some terms.

Something good seems to be happening.

But we have our work cut out.

There's something else
we might have forgotten.

What?

There was a question
of an F plus minus term.

Yeah, I've been bothered by that.

So, it could be the F plus minus
term takes this away.

Well, what are we doing
about that, because...

Well I thought I didn't produce anything
with three derivatives of epsilon,

but...
- We better check that.

There's a number we're after.

12 times the angular momentum.

So I think that is...
- Or divergence of--

It's so hard to get the number,
it's really hard to get the number.

If you do get the number...

Up here.

...that will tell you that black
holes have the capacity to store...

...all the information
that might have been lost...

I think there's a path in there somewhere.

A giant step towards solving
the information paradox.

And Malcolm got from
that to this by integrating by parts.

Illegally.
- Yes.

But, by using divergence
of a three-form...

You can do the same thing.
- You can get to this exact equation

and you always have room for...
- How many conformal

killing vectors on the two sphere?

Three!
- An infinite number?

Six!

Stephen's a very interesting person
to work with because...

I guess he's a man of few words,
so everything he says is really important.

Globally well-defined
strict killing vectors,

there are three of them.
Globally well-defined...

He'll ask something
which might at first sight

seem to be he's just clarifying something,

and actually it turns out to be

he's got a slightly different idea or...

he just gives a bit
of his insight or intuition.

Which might then sort of confuse everybody

and then we realize
actually it's really important.

So we've been, uh...

we're religiously abiding
by your instructions to...

forget about infinity.

I was laying some groundwork first,

sort of circling the mountain,

trying to figure out
which was the best route to the top.

And Stephen was like,
"okay, we're taking this one now."

He's very daring.

He doesn't want to spend a lot of time

exploring all the subcases
and different possibilities.

He wants to go for the jugular.

Would diffeomorphism
give all the entropy?

Which diffeomorphisms
give you the entropy?

Ah, so the question is
what are the diffeomorphisms...

This problem is probably
too hard to do on your own,

but different people think
about things in different ways

and, well, each brings
their own little bit of it

to the table.

It's basically
E to the i-n-phi around the...

it's basically...
- E to the i-n-phi but somehow...

I tend to race

to the end and then try
to fill in the spaces...

Really?

...which is a methodology which
is particularly prone to making errors

because you've already decided
what answer you want.

Whereas Malcolm
would be more likely to just

start from the beginning
and systematically

work through it,
which has the other problem

that if you're not heading
in the right direction,

you'll never get there.

So I think we compliment each other well.

Sasha has been a fantastic addition.

She started as Malcolm's graduate student,

and she went from zero to sixty
in a rather spectacular way.

We had it once and it went away,
and we got it again about 10 days ago,

but it's gone away again.

We're on the right track,

but it's turning out
to be monstrously complicated.

I think let's go this way.

I think go that way.

We should've brought a helicopter.

Well do you want to go down that way?

This one, you mean?
- No.

This was a really convoluted international
shipment because of what went on in Chile.

You know this is important data, right?
- Yes.

I don't like to hear the word convoluted
in the same sentence as "your data."

The implement of destruction.

This is freshly delivered data.

All the way from Chile,

recorder three, slot two, set two.

Nicely labeled. Mm-hmm.
- Vincent?

Photons from Chile. Frozen.

When we get the data
from these different telescopes,

the amount of data is immense.

We really have to measure
every single wave,

every single trough and crest

of the waves
as they come to the telescope.

We have to record this faithfully

and then match up each wave front

with the corresponding one
from another telescope

halfway across the earth.

Okay, the latest addition from ALMA.

What else do we have here?

We are generating about
one and a half petabytes of data

per night of observation.

Okay.
- Yeah, once we cleared...

By far the largest amount of data
per night of observing

than any physics experiment
in the history of science.

I want to see...

Okay, so here's a whole ALMA set

We bring all the data back,

all these disk drives to a super computer,

one is at the MIT
Haystack Observatory,

and the other is at the Max Planck
Institute for Radio Astronomy

in Bonn, Germany.
Then between these two sites,

we process and handle all of the data.

This is how you make
an earth-size telescope.

It's like a map of the entire globe.

So up here we have
modules that were recorded in Mexico,

uh, these are also from Mexico,
this is from Arizona,

uh, this is from Spain over here,

uh, this is from Hawaii.

We cannot do any of the processing
from the South Pole.

The South Pole station is closed now.

Nothing can land or take off.

All the data's
in the deep freeze until October.

This is where all the data come together

and we get the final data products.

So, it's happening. It's hard to believe
after so long, but it's happening.

Drop it for now and let's try,
let's just put the baseline in.

Once you correct the manual phase cals...

then this will clean up...

and even the signal-to-noise ratio
will go up and the amplitude will go up.

That is really amazing.

We're getting the kind of sensitivities

and the resolution that we have been after
for about a decade.

For me, personally,

this is a moment of great anxiety.

We've worked for a long time
for this result.

And we don't know even now what we have.

Black holes are out of reach.

We do not know
if the equations we're using

actually describes a black hole.

That's what we cannot directly test,
that's-that's the dilemma we're in.

In my laboratory,

I have a model that mimics
certain features of black holes.

Of course it is not a real black hole,
it would be pretty dangerous.

What we really have is
a gigantic pool of water.

You get this nice vortex
forming right in the center.

For small fluctuations on the surface
it should look like a rotating black hole.

There is physics associated
to the horizon:

light bending,

Hawking radiation,

superradiance.

And these are the kinds
of effects we can simulate.

All the effects that happen outside
the event horizon.

And at the end, you see an effect
which has been predicted for many years

without any experimental confirmation.

That's real physics.

It has been detected.

There is a limit to what we know
about black hole now,

but I'm a scientist,

this is the best situation you can be in.

We have this universe in a Petri dish.

And it's holding fantastic new insights

waiting to be discovered.

So zeta minus

zeta-tilda-Y,

and this contains an epsilon double prime,
that contains an epsilon prime.

So that will go like
one over W plus.

This goes one over W plus,

which means you got to compute
this thing to W plus,

you're sure there's not something else?

No it doesn't.

No, it doesn't, because it's only the one
over W plus term that can contribute.

Right.

We need that one over W plus.

So you have to
compute this to order W plus.

No.

No, because you want
one over W plus in the integrand.

Oh right.

Because the range of W plus is zero.

So if we don't have one
over W plus there, we get zero.

We didn't understand this in Brinsop.

No, I guess we did not
understand that.

We thought at Brinsop that
things were relatively simple,

we didn't have to think about so much,

But since then, we've discovered
all kinds of other things

which do contribute
and complicate matters.

In Brinsop, we thought
we could do it by hand.

You know, ten pages.

Turns out to be among the most

long calculations
that any of us has done.

That's actually spot on.

One thousand and fifty terms.

1050 terms? You can't do,
you cannot add 1050 terms

without making a single mistake.

Or I can't.

I think that's even beyond Malcolm.

I think I can do
about half of that, but...

So a month ago,

we realized we were going to
have to use computers.

Essentially adding up
many thousands of terms;

if they all add up to exactly 12J,

it will mean the hair
that's on the black hole

is enough to completely reconstruct
how it was made.

That's a long way towards solving
the information paradox.

We haven't seen that
happening so far.

Which either means that we-- there's
a mistake in our computer program,

a mistake in our input,

or a mistake in our conceptual
analysis of the problem.

And we've been up and down
in our level of optimism.

We must believe that actually,
it's going to work out properly

for the very simple reason

that we would not be putting this much
effort into it if we didn't believe that.

We are putting the effort in.
- We are putting the effort in, yeah.

And the reason we're doing that is
because we believe it.

If we didn't believe it
we probably would have...

Given up months ago.
- been a bit more discouraged.

I'm optimistic.

But I think we're missing
something quite--

we're missing a term or something.

Or an idea.

Or an idea or something. We haven't just
not added things up correctly.

The information paradox says
that because of black holes,

the universe

can't be described

exactly by physical laws.

I'm putting my money on an idea that

there are physical laws
and that we can figure out what they are.

But it's not over yet.

I think it is
interesting when observations

don't conform to

our standard picture of how things behave.

And that's when people start to look for

more exotic explanations.

And that's what happened
with the black hole story.

Black holes were initially very

esoteric, mathematical,
very hard to accept,

and yet increasingly over time,

there were observations
that didn't make sense.

Black holes were the best explanation
for what was observed.

What was still quite controversial
were the supermassive black holes,

the ones that were a million to a billion
times the mass of the sun.

Maybe all galaxies harbor supermassive
black holes at their cores.

Even our own galaxy.

That was pretty controversial,

and that is certainly the idea
that I got very interested in.

And I had this technique
that I was working on,

my group and then the group in Germany,

that in principle could figure it out.

And this was just as the Keck Observatory
was opening up in Hawaii.

It's kind of amazing
that a very big telescope

let us monkey around with
the instrumentation at all.

And yet it worked.

All of a sudden you could
see the center of the galaxy,

these stars at the center of the galaxy.

And if there's a black hole there that has
a few million times the mass of sun,

these things are gonna move
really, really fast.

‘95 was our first measurement,

‘96, we saw a second picture,
and oh my goodness!

Those things were absolutely
not in the same place.

These things were hauling!

‘98, ‘99, it was already clear

that the ones that were really close,
were starting to curve.

The curvature gives you a direction
to the black hole.

And we had three stars that were curving,
so it was like three arrows

and they all intersected
at the same place.

You need something very massive

to drive that kind of short-period orbit.

It's hard to conceive of
anything else at its center

other than a supermassive black hole.

We're on our way in.

You can just taste it.

345

No, I think Kazu told me--

Yeah, but Kazu told me
to look at 120 yesterday

and that's why that we
were looking at that one.

So this is 3C345?

Yeah.
- Okay.

The fact that we're aiming
so high with the EHT

to see something you know
no one's ever seen before means

we have to develop an entirely
new set of tools.

It's a lot easier to start
with a big field of view...

We have to reconstruct an image
with sufficient fidelity

that we can trust what we're seeing.

...small and then you get
some weird structuring on there.

Yeah, anyway, I don't have it loaded on
linear scale with them all in the same

When we take a picture
on our camera, right,

you believe that picture
is exactly reality, right?

You actually saw that with your own eyes

and you can see, oh, okay, that matches.

When we take a picture of a black hole
with the Event Horizon Telescope,

we don't get to see that,

we don't know if the picture we generate

is actually what the
black hole looks like.

How do we evaluate what's the true image?

So which is right?

What I'm saying is in general...

which is right?
You know, people publish...

One way we approach the problem
is by separating the teams

into different groups
that can't talk to each other.

We generate data from
lots of different kinds of images,

realistic data like we would get
from the Event Horizon Telescope,

then release to the community
but without the true image

and we say, do your best job,
get your best image from this data.

What happens in Team One room
stays in Team One room, right?

If I see another team's image,

I might start trying to push
my imaging algorithms,

even subconsciously, in a direction
that would favor that kind of image.

Look at these amplitude error bars

We want to have many rounds of
imaging and refining that imaging process

before we actually compare the images

You look at all these different things
with the same data,

it's a cage match of love...

We should be able to cross-compare the
different algorithms between the teams.

And if we start getting
convergence on those,

then we'll know that we're in a good
position to do the same for Sag-A- and M87

And here is
low closure amplitude.

There's a really big difference.

It is three days apart.

Yeah, but the source
has not changed that much,

and you cannot change the speed of light.

But you know, orange and blue, that's
exactly same day, exactly same time

In Team Two,
I would say we had a hard time.

My feeling is that data are not yet ready,

not yet well-calibrated

for imaging.

So there is still work to be done.

I just happened to be looking
at the Guardian website

at around midnight
on the evening of the 13th,

and they announced it.

And that was it.

We had been talking
about going to see him.

Because we were worried, and because

we knew that the work
would lift his spirits.

We kept saying as soon as
we get somewhere,

we're flying straight back to the UK

to talk to him about it
and discuss the next step with him.

It would have made him so happy to realize
that we'd got somewhere with this project.

And unfortunately we just
didn't get there in time.

We all think in different ways,
- Yeah.

and he has his own
unique way of thinking about things

and we're not going to be allowed
to have access to his mind anymore.

That's a huge loss.

There's a special kind of friendship

that grows out of scientific
collaboration and discovery

that's in my experience like no other.

And to have a, you know...

scientific...

a productive scientific interaction

with somebody over many decades

and then lose them,

is very sad.

It's sad in a different way than losing
a relative or, but it's...

it's, uh...

it's a special thing and
it's very sad to lose that.

You can imagine
if you were floating

near two black holes that collided.

As they orbit, space time begins
to ring in response.

They're like mallets on a drum.

The drum is space time itself.

It begins to ring.

Gravitational waves, squeezing
and stretching space.

In principle, they would pluck
your ear drum,

you would hear them
even though it's empty space.

Gravitational waves are actually like
a sound in the medium of space time.

And that was the greatest
discovery of 2015.

The experiment LIGO recorded the collision
of two completely dark black holes.

The final one-fifth of a second

before the black holes merged
and went quiet as a bigger black hole.

And that's stunning.

The only evidence we've had
for black holes before then

was what they do to their environment.

This felt direct.

The first completely direct evidence

of not only the existence of black holes,

but the existence of
a pair of black holes.

This signal comes after traveling
over a billion years,

and they record it.

Just a spectacular, spectacular discovery.

My work very much was about
theoretically how black holes collide,

what it would sound like,
simulating those sounds,

and understanding the dynamics
of black hole orbits.

Gravitational waves are so quiet
by the time that they reach the earth,

the experiments only pick up
the final few orbits.

To dig deeper and hear the approach,

my group has been doing approximations
of the final several minutes.

Listening to the longer run-up,

we can tell if the black holes had a
more interesting dynamic,

if it was a more complicated motion.

So in this case not only are the
black holes different masses,

not only are they on
a more complicated orbit,

but they're also spinning.

The system begins to rotate in space

and you can hear it get quieter

as the gravitational waves
are beamed away from you,

and louder as they're beamed to you.

And so these are all
details we can extract

from the gravitational waves'
sound just by listening.

And then they get louder, faster,

right before they merge.

And then it goes quiet
as one big black hole.

There is a human pleasure

in being able to experience, viscerally,

a recording like that.

In some sense,
making black holes more real.

What a remarkable time to be alive:

to actually be on that cusp
of not knowing, and then discovering.

All right guys,
we're gonna release the data.

Whoo!

Big moment, let's do it then.

Okay, I'm including everybody in the
entire collaboration on this note.

The end goal is to have this snapshot
of reality: how a black hole really looks.

Black holes at the center of galaxies
are bathed in this hot glowing plasma,

and so there's light coming
from behind the black hole

and in front of it and every which way.

They curve their spacetime so much

that even light from behind the black hole

can be bent around them
to reach the observer.

You can imagine

some of the photons would be
far enough away they'd just come to you,

some of them would be close to the horizon
and they get bent inward,

and some of them would be too close
and they'd fall into the black hole.

And so the shadow of the black hole
is this circular area

of diminished brightness

with this bright ring around it.

It's really a special thing that
there's such a concrete prediction

for something that no one's ever seen.

You know, if you're making an
image, you have to come in the other room,

Okay.
- So we all start at the same time.

Team One Imagers!

Okay, which day has the best coverage
by the way?

I'm doing 3601.

I was going to do 3601 for now.
- Same.

Okay, are we ready?

I'm giddy.

Oh, my God, wait, should we close
the door, are we ready?

Wait, what is happening?

We're trying to make
an image right now!

Can we just pace things a little bit?

Well no, first of all.

Shep, close the door!

Oh, my God!

Can we start Michael?!
You don't have to start...

Let's wait for Michael

Can we just go on
our little trajectories

and you know meet up in 20 minutes?

No.

I just think it's like a big moment,

and I think for me, I'm just saying, like,

I think it'd be fun for us all
to do the first one together,

see that shit, and then go off in our
own little ways and fix it.

I think it's just so exciting that you--
do you want to do it alone?

I'd like to see it all together so
we can kind of get some idea of the data.

Are we ready?

Ready.

It's not gonna work at all!

Enhance, enhance, enhance!

Ready?

Set.

Go!

Oh, my God!
Oh, my God we pressed go!

It's just a waffle.

Ah! That looks really,
really interesting.

How's the waffling going?

Andrew's looks beautiful but...

there's no tweaking involved.

I put compactness very high.

Daniel and I were both getting
something like this, with--

That's what I get when I use only closure.

Only closure?

Oh, my God, look at the chi squareds!

That's pretty good!

And then this is,
after a few more iterations,

it smooths it out and gets rid
of some of the extended junk.

This is all on low-band?
- Yeah

Is this only one day?

This only one day?

You know what –

That's pretty suggestive.

Well, it seems--

Did you remove these outliers
in the amplitude?

I didn't touch anything.

That is very cool guys.
It's really, really cool.

Wait, which one is that?

This is Katie's image.

See it looks different though,

because you guys have a
bright spot more on this side.

Okay, seriously?!

Look, we're all getting kind of a crescent
that's about the right size--

So what is the size on that,
it's like--

This is about 40.

That's when you expect if M87
has six billion solar masses.

That's a high mass case.

You know what this is?
This is a scale to weigh black holes.

Okay, seriously if we can get
anything that looks remotely

like that on all the days--

Guys, the only way
anyone's leaving this room

is if everybody gets over there
so we take a picture.

It could have been awful!

Am I short enough
that I can just stand here?

And you got to get the thing!

We're at a point now

where things could inadvertently go south.

Okay, so I took a picture on my phone,

of something on the screen.

See you guys tomorrow, we'll do some more
imaging tomorrow.

All it's gonna take is
for one of these images

to be texted to the wrong person,

people will look at it,
they will measure it off of a screen,

they'll go write a paper.

I guarantee you.

There has to be an absolute, 100% embargo.

No one outside the EHT collaboration
can see anything,

anything that happens here

can never leave Team One.

This is pretty wild.

It's all wrong, I'm sure it's all wrong,

but if that works out,

it's pretty amazing.

Things are going well.

We think that we have managed
to do this part of the project.

We've managed to get

our target answer of 12J.

There's a little bit left to do.

I think the only thing
that matters is 3.5.

3.5?
- Yeah.

Good to see you.

Hey Sasha!

Oh hey, you're here already!

Yeah, we've already done
like five pages of calculations,

you're late!

You're allowed to put your stuff
away and go to the bathroom.

That's alright, I'm needed.

No time for that!
- Nope.

Okay, uh...

So where are we at?
Like, what still needs to be done?

The only things I see now...
- Mm-hmm.

is understanding this
G plus minus to the P.

Yep.
- Right. And the past horizon.

And the past horizon.
Does anybody see anything else?

No, that's it.

Back at Brinsop, one year on.

Last year we thought
it'd be pretty plain sailing,

we would spend a few
more weeks then we'd just

sum up all these terms
and get the answer we wanted.

And then over the course of last year,

we realized actually it's so much
more complicated than that.

Tleft, over Tright plus Tleft

We found there were millions of terms
and it was never going be a two-week job,

and we got out computers
for the first time, and that didn't work.

One over Y.

And then, what we realized is that you can
actually break this equation we had,

we could break it down into an integrable
part, and a non-integrable part.

I think that was the breakthrough.

We had to realize that

we had almost everything we needed,

but there was somehow

a few terms got lost I guess.

N, D, here

What we've discovered is that

the equation is the sum of the
variation of the inertia charge

and the variation of the
angular velocity of the horizon.

Which, when evaluated you get 12J.

Before, we just had a few of the terms

involved in the
angular velocity of the horizon.

And without the full thing,
it wasn't integrable.

Now we've found a nice physical picture

and a nice way of getting 12J

and now's the final, you know,

finishing touches, to make sure
that we really believe in it.

I'm just very sad that Stephen won't be
able to see this through to the end.

He would have been really, really excited.

It's weird how personal

physics can become.

One of the saddest things about Stephen's
passing in the middle of this is that

if it works we can't tell him.

One bottle in front...

To Stephen.

To Stephen.

One of the impressive
and wonderful things about Stephen,

was how much he really...

cared... about--
about these questions.

We know that it's somehow
very different inside a black hole.

And so the prize is a really
big one if you figure it out.

The nature of spacetime.

That's about right.

Hawking handed us
the biggest clue that we have.

If this project we're on now

works, it will be like a giant sign post,

"there's gold in this direction."

You look up in the night sky

and of course you don't see them.

But you know they're up there.

Almost mocking us:

"try and figure me out."

I just want to check my audio.

Can you hear me?

Yeah, I can hear you.

Hi Monica, can you hear us?
- I can hear you. Hello!

Okay, so I just want to start,

the first telecon actually showing
the first images of M87.

All images are very consistent,

there is a shadow-like feature.

Really really encouraging results.

Wow, it worked. I mean,
it definitely worked.

We see the ring,

and then you've got to be
very skeptical, actually.

You know, I would love to see that thing

and that's what makes me very suspicious

about myself and what I see.

I think it's okay to call that
a shadow feature, if you like,

as you see in the middle,

but we should be really careful of
what we think we see.

Are we going to see other teams' images?

No, no, no, no.

When we meet at imaging workshop
to inspect images from each team--

I could not sleep last night

because I was so excited.

I mean, I've waited for this data set
and this image for eight years.

I'm really happy that we're all getting
pretty consistent results,

and I'm excited to see
what the other teams are doing.

We all kept pretty good secrets.

Imaging Team Three has been doing
mostly the standard technique

where we use this algorithm called Clean.

We have about half a dozen individuals
on the team who are making the images.

The central part of the image
we're in general agreement on.

It'll be interesting to see what the
other teams using "maximum entropy"

and some of the other methods,

what they got next week.

We hope that they will be consistent.

We're trying to be very,
very careful about it.

The worse thing would be to say
that we've seen black hole shadow

and then find out later
it was an imaging artifact.

Right now within Team One,

we feel pretty confident in the structures
that we're getting.

We are feeling pretty good about
our consistency in our images,

but we haven't seen anything
from the other teams, so,

it's possible that everything will be...
a complete--

a complete mess when
comparing between the teams.

And I'm a little scared for:
what is our plan moving forward,

if we do get different images?
- Yeah.

Good morning!

How's it going.
- Pretty good.

Okay, I look forward to it.

Hey!
- Hey.

Nice to meet you finally.

I'm Katie.

Nice to meet you!

Thanks for coming all this way!

This is an incredibly
exciting moment.

For the first time we're gonna see if

all the teams are seeing
the same basic structure.

have not seen any of the results
from anywhere else.

So this is really a Christmas,
Hanukkah moment, right?

This is when you unpack, this is when you
open up the gifts you know.

Did you get a pony? I don't know.

And then I self-calibrated and then
amplitude plus closure phase.

Okay

I had a little bit goosebumps.

I've been waiting for this moment
for like ten years.

I've been modeling black holes
for ten years,

and finally it becomes real.

Let's see what we could do

if we were to just use
the exact same script

without changing anything,
without any fine tuning,

to see what it will do.

Okay. That would be
very interesting to see.

Just out of curiosity.
To see if we can come up with one script

that could consistently...

all on microarcsecond scale.

So it does seem like kind of filling
in the vacuum with more.

So I guess we have two options
for response to zero baseline.

And in both it's producing more or less
the same image, right?

It doesn't make any
sense to use it in that.

It does actually, they do bring
extra information.

But it could be completely
extraneous information

Michael, I still haven't received an image
from Team Three, should I bug them?

Okay.

Then it's going to be much much worse--
- Okay.

Sorry, real quick.

How much longer do you need
before you're ready?

Um, I don't know...

Like 15 minutes?

Sure, if everything goes smoothly here,
15 minutes.

How long does Team Three need?

Couple of minutes if it is working.

Let's just do that,

you can see the numbers,
if they look fine to you...

Okay.

Hey, I--

I'm ready. I'm ready, yeah.

All right, so first we did a normalized
cross-correlation comparison

between all of the images.

A value of one is going to be a perfect
consistency between two images,

zero is pretty bad.

So are we ready for the moment of truth?

Okay, I will scroll down.

Oh, my God.

Look at that.

Wow!

It's M87!

We compared, basically pixel by pixel,

you know, how close the images were.

We haven't talked at all
among the teams,

but these numbers tell us
that despite that,

we're all broadly seeing
the exact same structure,

so it's really promising.

It was surprisingly emotional.

You know it from
a mathematical point of view

and we've been looking at pictures
quite similar to that from our own models.

But when you look at it and you have to
tell yourself that it's actually data,

that you're not seeing a simulation
but you're really looking at a black hole.

I found myself just with my cell phone
staring at it for hours.

What's going to have to happen now is,

the whole collaboration has to
come together and agree.

It's the same latitude as ALMA

This is a very, very critical phase
of the project.

We have to bring very different people
with very different backgrounds

together to agree on something that

will be work representative of
200, 250 people.

That's a great question.

I think that what would be best--

It's very easy to lose your credibility.

And the Event Horizon Telescope has
built up credibility over many years.

We have to get it right.

How do you decide
what's the key essence?

What do we all agree on?

This has been a discussion
and it's been contentious.

And it's probably not fully decided.

Yes, we do want to have a...

a single image,

but we do want to show
the variations as well.

Yes, it's a compromise
we have to come up with.

Something that works.
That thing that works.

I think it's not
what we want to show,

I think we should go for the best data set

and the best image of this,

easily reproducible for anybody
who wants to do it again.

I kind of like the average image

but since it's not consistent
with any data,

are we going to use this image
to do for instance a parameter estimation?

Everybody came in with their
own funding, their own expectations,

so it is all about convincing each other

and coercing each other
to find one way forward.

I mean, do you think there are unmodeled
systematics-- in the synthetic data...

That made it very democratic,

but it's not easy,

I will not lie.

I think the dream
of any physicist who studies black holes

is to be able to go through the horizon
and to the other side.

If I could take this trip,

having decided that I've had
enough of this world,

what would I see?

Just as ancient explorers
were drawn to the sea,

we're drawn to the horizon.

We're drawn always to the limits.

The horizon of a black hole

is the edge of our knowledge,

of our understanding of the universe.

And the great exciting problem
is to go beyond that edge.

That's the ultimate.

That's the place
where there's no "beyond".

It's something that doesn't exist

as a physical, measurable part
of the universe.

But you personally could still go there
and experience it.

But you cannot tell anybody.

And you don't exist anymore
to the outside world.

People always make the link
intuitively to death.

There they are! Smiling!

It's nice to see you again.

Miss you guys, miss you guys.

So we're free.

We've finished the paper.

That's why everybody's smiling.

I'm feeling pretty good.

I must say I'm feeling amazingly good.

Simply because it has taken an amazingly
long time to actually get done.

It's a great relief.

It's nice to be able to...

to think about the
bigger picture a bit more,

I feel like, I spent a lot of time
getting really bogged down in--

You feel liberated.

Yeah, I feel liberated, to be able to
work out more what's going on,

and I feel like the result we have
is very compelling.

We've shown that
the soft hair can account

for all the information
that's stored in a black hole.

But we have to be very smart
about what to do next.

Yeah, absolutely right.

The big challenge is trying to show

not only that this could happen,

but that it does happen.
And that there's a mechanism

for the flow of information
in and out of the black hole.

That is a much more complicated problem.

That's what Stephen would
want us to be doing.

Are you coming to the--
this press release on the 15th?

I'm, I'm hesitating.

Well, good afternoon.

Welcome to the press launch of the
final book by Professor Stephen Hawking.

Now, up until his death he continued to
search for answers with his final paper,

a work with his long-time collaborators,

Professors Malcolm Perry
and Andy Strominger,

on one of the most puzzling problems
facing the scientific community today,

the information paradox.

So Malcolm, Andy, give us
a capsule summary of the paper.

Yeah, you know, it's a huge problem

that Stephen gave to us.

It took 50 years to understand

what a black hole was before you started
worrying about quantum...

It'll be a decade before we know

whether this path is gonna get us
where we want to go.

We also don't know that it can't.

And, I also have to confess,
not very scientific of me,

it has the right feel.

I'm very excited to be part
of this grand adventure.

To Stephen.
- To Stephen.

To soft hair.
- To soft hair.

And to the demise of
the information paradox.

And to the next paper.

It's a great life.

It's what life is about.

I feel the same way.

Welcome to today's press conference.

Brought to you by the National Science
Foundation and the Event Horizon--

Good afternoon.

We have very little time before the actual
announcement goes live

across the globe, in six simultaneous
press conferences, so I will--

Buenos dias a todos, today is an
extraordinary day for astronomy.

What you're seeing here is the result
of many, many people working together.

Thank you, assembled guests,

black hole enthusiasts.

Black holes are the most mysterious
objects in the universe.

Now, we are members
of a large collaboration.

We are 200 members strong,
we have 60 institutes,

and we are working in
over 20 countries and regions.

We worked for over a decade

to expose part of the universe
that was invisible to us before.

And we are delighted
to be able to report to you today

that we have seen what
we thought was unseeable.

We have seen,
and taken a picture of, a black hole.

Here it is.

We now have visual evidence
for the existence of a black hole.

We now know that

a black hole that weighs
6.5 billion times what our sun does

exists in the center of M87.