All language subtitles for BBC.How.to.See.a.Black.Hole.1080p.eng

The universe holds
a giant cosmic secret.

Nobody's ever seen what
a black hole really looks like.

Now a team of international
astronomers

are on a mission to find out.

Here we go. We're on!

The team's director
has dedicated his life

to take the first ever
picture of a black hole.

If you ask why this hasn't
been done before,

it's because it's really,
really hard.

For two years, our cameras
have followed these scientists

to the most hostile environments
in the world...

It's pretty cold.

The wind chill right now
is around minus 70.

..as they build a revolutionary
telescope the size of planet Earth.

If they succeed, a picture
of a black hole

will challenge the theories
of Albert Einstein

and could pave the way
to a new era of physics.

It will be one of the most thrilling
discoveries of our age.

This is the inside story
of the mission to capture

the first real picture...

..of a black hole.

Of all the wonders in our cosmos,

one object has remained hidden
to the greatest scientific minds.

The black hole.

A black hole is a region of space
where the pull of gravity

is so powerful that nothing at all
can escape if it gets too close

and, by nothing, I mean nothing,
including even light itself.

What we really mean by that is
this area called the event horizon.

It's a specific limit around
the black hole that marks

what's inside and what's outside.

Once anything crosses that boundary,
adios. It is out of contact

with the rest of the universe.

We don't know what
its ultimate fate is,

but probably it ain't very good.

Most scientists today believe
that black holes really exist...

..but nobody has ever actually
seen one.

We have identified lots of objects
that look like black holes,

but you can't prove
that they're black holes.

This is where the problem comes,
right?

If nobody has ever seen
a black hole,

can we be sure
that they really exist?

Could this fundamental notion
about our universe

and how it works be wrong?

Astronomer Shep Doeleman
is on a mission

to solve this mystery.

He's spearheading
an extraordinary experiment.

He wants to take the first ever
picture of a black hole.

The goal of the entire project
is to see what a black hole

really looks like, detect its shape,

and see what's happening
immediately surrounding it.

I mean, just saying that
gives me chills.

I've been interested in black holes
since I began doing astronomy.

It's really kind of what got me
into it in the first place.

I kind of fell in with this crowd
doing radio astronomy

in a very special way.

Here at the Haystack Observatory,

and across the world,

Shep has been developing a technique
to try and see the unseen.

Shep is targeting the very centre
of the galaxy,

where astronomers have detected
a cluster of stars...

..orbiting something strange.

The stars are orbiting so fast...

..scientists have calculated
the object must have the mass

of more than four million suns.

The best explanation,

a black hole called
Sagittarius A-star.

Shep wants to use radio telescopes
to try and see this black hole,

but there's a problem.

Although it's predicted
to be larger than the Sun,

from Earth,
it's 26,000 light years away.

This is such a small target,

there's no telescope in existence
that has the power to see it.

The entire reason this hasn't
been done up till now

is that black holes
are extremely small.

It would be the equivalent
of trying to see an orange

at the distance of the moon.

So we have to build the telescope.

We have to build a fundamentally
new instrument

that can see things
that are that small.

To achieve this unprecedented power,

for the last decade, Shep has been
working towards a master plan.

He wants to combine eight separate
telescopes in Spain,

Mexico,

Arizona...

..Hawaii,

Chile,

and the South Pole.

This network is called the
Event Horizon Telescope

and spans the face of planet Earth.

To capture the crucial image,
all eight dishes must point towards

the black hole
at exactly the same time.

We're linking telescopes
10,000km apart,

even more than that.
By spanning the globe,

you create a new kind of instrument
that can see a black hole.

That's the secret sauce,

that's the secret
of the Event Horizon Telescope.

Each of the eight telescopes
in the network

are unique and powerful
observatories.

They can detect emissions
from around the black hole,

but the team will need to combine
these signals to make an image.

Across the world,

the team will observe the black
holes simultaneously

and record the data onto hard
drives.

Then they must physically
transport the drives back

and combine the data inside
a giant supercomputer

called a correlator.

This correlator is the final
piece of the puzzle.

The first part is collecting data
at different spots around the globe.

The second piece, though,
is combining that data

and that's what the correlator does.

Only then will this new
Earth-sized telescope have a chance

to make an image of a black hole.

If the Event Horizon Telescope
manages to actually

take a high quality photo
of a black hole,

that's not an impressive feat,

it's a mind-blowing feet.

It's a technical tour de force
like we've never seen before.

But what does Shep's team hope to
see if a black hole allows nothing,

not even light, to escape?

A black hole itself is invisible...

..but matter falling into it
should give it away.

It's intense gravity
attracts interstellar gas,

and pulls it into
a faster and faster orbit.

This heats the gas
to billions of degrees

and emits a light that the
telescopes should be able to detect.

The mathematics suggests gravity
will warp these emissions

into a circular ring,

leaving in the centre
the shadow of the black hole.

It's an important
scientific prediction.

If the team sees something
that isn't circular,

it could turn the most treasured
theory in physics on its head.

Einstein's theory
of general relativity.

His theory says mass curves the
fabric of space and time,

creating an effect
that we call gravity.

Einstein's theory of relativistic
gravity is what lays the foundations

that sets all of our understanding.

Step one is just,
did Einstein get it right?

Is there some detail
that's been overlooked?

For 100 years, Einstein's
theory has passed every test.

But nobody has ever seen
its most extreme prediction.

If enough mass could be crushed
into a single point,

its gravity would be so strong
it would form a black hole.

How wonderful would it be if the
Event Horizon Telescope shows us

that, in extreme realms, Einstein is
not completely right?

It will be one of the most
thrilling discoveries of our age,

as we will then leapfrog
forward in our grasp

of how the universe works.

A challenge to Einstein's theory
and a new era of astronomy

rests on the success of the
Event Horizon Telescope team.

There are now just three months
until the team will attempt

to observe a black hole
using a network of eight telescopes,

but there's a lot to do.

Shep has come to Mexico
to oversee a crucial test run

using four of the eight telescopes
in the network.

What really gets us out of bed,

what really gets us motivated
for this,

is building a new kind of
instrument.

When you think of building
a telescope as large as the Earth,

that in and of itself
is such a crazy idea.

To link the telescopes,
the team will use a technique

called "very long baseline
interferometry" or VLBI,

but it poses a major challenge.

During the observations,

they won't see any results
in real time.

The very nature of the technique
we're using is that we're not

going to know if these observations
work until we get all the data back

to a central processing facility,

so we're here to do
what's called a dry run...

..to make sure that everything
runs like clockwork.

Scan two...

Not 0.78, it's 0.078.

We have crack ninja teams
up here in Mexico, Chile,

the South Pole, and Spain,

and they all know their business,
frankly.

They know what to do.

You check everything,
and you check it again,

and you check it three times.

During the critical observation run,
there's a lot that can go wrong.

The radio emission from the
black hole must be recorded

at each telescope

and the data stored onto
specialised hard drives.

Clouds can obscure the signal
and equipment could fail...

..knocking one or more of
the telescopes out of the network.

So the team need clear weather
and perfectly working telescopes

at every location across the globe
simultaneously.

If just one telescope fails,
they might not get an image.

After the data have been recorded,

the filled hard drives
will be shipped

to Massachusetts and Germany,

where the data must be combined,

and they will know
if their ambitious plan has worked.

Are things all set? I hope so.

In Mexico, astronomer
Gopal Narayanan is in charge.

The whole purpose of the test
observations we're doing

is to bring in a couple
of new facilities.

We're going to bring in Apex,
which is in Chile,

Pico Veleta in Europe,
and the South Pole Telescope.

The South Pole is a critical
location for the team.

Its clear, frozen skies
are perfect for observation.

But flights here will soon
stop for the winter,

which means the data from the South
Pole will be the last to return.

Instrument expert Dan Marrone
and his team have travelled

here to the ends of the Earth
to get the telescope ready.

By including the South Pole
Telescope,

we really, truly make a telescope
the size of the Earth.

It more than doubles
the resolution of the array

and gives us that last bit
of detail that we need

to make a picture of a black hole.

It's January.

The weather is a biting
36 degrees below zero.

So, it's pretty cold.

The wind chill right now
is around minus 70.

Despite the cold, the teams
still need to prepare

for the test observations.

They must install this custom
built mirror to the telescope

with submillimetre accuracy.

OK, I do believe the tertiary is
installed.

We have to have this here,

positioned so that the light
from the giant ten-metre telescope

is focused precisely
on our receiver.

So that took a little bit of doing,

but we think we have it right
about now.

The mirror is in, but, until
the observations are complete,

they won't know if it's worked.

Back in Mexico, Gopal and the
team get ready to start the trial

observation run
with the four telescopes.

They will observe bright sources
called quasars

to help test the new network.

Data specialist Lindy Blackburn
is in charge of recording the data.

One minute to go.

I'm ready to go.
Is Lindy happy with this?

Here we go!

We're on.

But, as the test observations
begin...

OK, recording.

..there's an unexpected problem.

What?

A bug in the code means the
recording lights are not coming on.

No, it's trying to record...
Oh, it's trying to record. OK.

Setting data to record,
only the very last step

in this whole fine process,

which is albeit
a very important step,

which is to record that data we've
collected all through the chain,

that is not happening right now.

Without data,

the telescope is knocked
out of the network.

Lindy is working furiously
to find a fix

and I think we're hopeful.

So the IF levels look fine?

Yeah. Tell me it's workin, Lindy.

No. No!

BLEEP

The same problem.

I changed the order when I thought
it was the initial problem...

You're hoping that we'll get
this recording this time, Lindy?

I really don't know.

One minute... Are we ready?

Ten seconds to go.

Lights! Yes!

Good job, Lindy!

It's 2:46am.

The team have succeeded
in recording the test data.

But they won't find out
if it's worked

until the data have been analysed.

Only then will the team
know if they stand a chance

on the real observation run...

..when they attempt to record

an image of a black hole.

An image of a black hole

will provide a new way
to test Einstein's

most extreme theoretical
predictions.

Einstein's equations show us
that if you spend an hour or two

at the edge of a black hole,

and then come back to Earth, for
instance,

Earth might have aged 10,000,
or a million, or a billion years.

So when we are observing the
event horizon of a black hole,

we are observing what really can be
characterised as a time machine.

Yet, despite Einstein's equations,

even he didn't think
that black holes could exist.

That nature could ever
allow them to form.

That's a sensible objection
that Einstein had.

I mean, after all, it'd be very,
very, very hard to do,

to crush all the mass
of something to a point.

Einstein naturally and reasonably
assumed

that matter just wouldn't allow
itself to be compacted that much.

But evidence of a mechanism
has been growing.

Scientists now believe a black hole

is the corpse of a giant star
that's gone supernova.

Deep inside the debris,
the surviving core collapses

to an infinitely small point.

This is called the singularity.

Its intense gravity warps space and
time so severely

that nothing can escape, forming the
black hole's event horizon.

It's possible that black holes
are ultimately a figment

of the mathematical equations
that Einstein gave us,

but how better to begin
to push this understanding

than to look and see
what's actually out there?

And that's the promise
of the Event Horizon Telescope.

The team hope to test these
theories by taking a picture

of the black hole
at the centre of our galaxy.

But they have an even bigger target,

a black hole in the centre
of a different galaxy

called M87.

There are only a couple of targets
in the universe currently

where the Event Horizon Telescope
could hope to resolve

this silhouette of a black hole, to
see the edge of the event horizon.

M87 is one of them.

This image of M87 is the closest
astronomers have come

to seeing a black hole.

But to see its edge,
Shep must zoom in much further.

If we want to image the event
horizon, we have to make an image

of what's inside this little box
here

at the very central core
of this galaxy.

That's what we've been directing
all of our efforts towards

for over a decade, to find out
what happens in this place

that has been off limits to us
since the beginning of astronomy.

If they succeed,

computer simulations show they
should see this.

Light bent into a ring
and the shadow of the black hole.

If we can see this ring,
it would be the best evidence

that we have
for the existence of black holes.

There are now just two weeks to go
until the team will attempt

to observe the black holes

and they're still working
the problems.

In Europe, Dutch astronomer
Remo Tilanus is in charge

of managing the logistics
of this global project.

Hey, morning. Morning.
How are you guys doing? Good. Good!

I like that, what you guys did.
The monitor.

It looks very good. Thank you.

It's taken two months for the team
to process the test run data,

but the results are finally in.

Hello.

Hi! Hi. Some nice results
to show you.

The data shows the telescopes
have successfully linked together.

Even though they're apart
by thousands of miles,

they actually observed the source
exactly at the same time.

But we did have problems
because the South Pole telescope,

it has moved by about 20 metres
because the whole ice sheet moves.

That's quite unusual.
I think there's no other telescope

which does that, actually.
I hope not!

I certainly hope not. We are
in trouble then, if that happens.

That doesn't mean that the job
is quite done yet.

We have a few technical
issues we need to take care of,

but the core system works.

It's good news for the team.

But Heino Falcke, one of the
project's leading physicists,

knows how difficult linking
all eight telescopes will be.

If you go to these
extreme experiments,

you have to be extremely precise
and take everything into account.

You need to know the position to a
fraction of a millimetre precisely.

If you look at Hawaii,
this is a volcanic region.

This actually shifts
due to plate tectonics

by six centimetres per year.

But, you know,
if you go to the South Pole,

there's ice and that flows,

and this can move by metres -
ten metres sometimes within years.

So this really is the Formula 1
race car of the telescopes

moving positions.

And, of course, let's not forget,
you know,

away from the Earth is the moon,

and that actually
it's affecting the entire globe.

So some of the telescopes actually
will be pulled by the gravity

of the moon into one direction.

They move half a metre up and down
every six hours.

With such incredible
precision needed,

the team need everything
to go to plan.

Any telescope you lose will
significantly compromise your
result.

It will still be interesting.

It'll just not be an image.

It'll be some data
and some plots that you show,

it will not be an image.

Some of the others are very nervous,
I believe,

that they absolutely...

..want to get the picture this year.

But I'm more relaxed.

I find it exciting

just to be at the point
that we can try to do this.

Remo has come to the Max Planck
Institute for Radio Astronomy

in Bonn to check
the team's preparations.

Here, hardware specialist
Alan Roy

is facing a problem that could
jeopardise the entire project.

Hey, Alan.

Hi. Good to see you.
Hi! How are you doing?

Had a good trip?
I had a good trip, it was fine.

Oh, man. So it's happening here.

So, more problems. Yeah.

The machines that record
the data are overheating.

The problem with the recorders
we have at the moment

is they're getting too hot inside
and they're shutting down.

If that happens in the run, then
that would stop us in our tracks.

The observations we're making

depends on having
the whole array present.

HE SPEAKS IN GERMAN

The problem is high altitude.

The thin air at the telescopes

means the cooling system
is less effective,

so Alan needs to make metal plates
to deflect more cool air

over the electronics.

No.

So, let's see if it fits.

It's...

..always a moment of tension,
even in simple things.

And, yes, perfect.

Across the hall, Helge Rottmann
is in charge of over 500

hard drive units that can store
millions of gigabytes of data.

Disk modules, they really contain
the essence of what we want to do.

The speciality about these,
they are helium-filled disks,

able to operate
at very high altitudes.

In terms of operational costs,
this is the main factor,

so buying disks is expensive.

For example, we cannot afford
to back up any data

and, if it gets lost or broken,

we practically lose that data,
which is quite catastrophic.

That's my nightmare - that we'll
have like a whole pallet of these

and they drop the pallet.
That is just going to be horrible.

Remo must send the drives
to each telescope location.

It's just one small part
of this global logistical feat.

It's now 8pm and Remo
is running a teleconference

with the rest of the team.

The next issue I think
I want to tackle is the

outstanding tickets that we have
before we get to the observations.

Just two weeks away
from the observations,

the pressures and tensions
of the project are mounting.

The schedule starts
at 3pm local time, at 0100 UTC.

There's nothing we can do
about it any more.

I mean, these were discussed
and have been discussed,

so the schedules are what they are.

Just assume that it's going
to be OK. All right.

Nothing we can do about it.
No, no, I realise that.

OK, that's it, guys. Thanks all.

We'll be in touch.

OK, bye-bye. Thank, bye.

Taking ten years
to pull all these telescopes

into the array, to equip them,

we're all motivated
by the same thing.

We want to see that black hole and
that is ultimately what drives us.

Get a glass of wine and go to bed,

seriously, that is what I now want
to do.

There's now just one day to go
before the make or break

observations
to photograph a black hole.

So move it here.

Imagine we had it kind of open...

In Massachusetts, Shep and physicist
Demetrius Soltis

are setting up
a central communications hub.

Yeah. To have space around,
something like that.

What do you say? Now you're talking.

Now you're talking.

This will be mission control.

Communication is vital
to the entire project.

I mean, we're synchronising
things to a microsecond.

We need to make sure that everything
is set up.

We need to make sure all
the tests have been run.

The team need to link eight world
leading multi-million dollar

observatories simultaneously
to capture that image.

We've got clear blue skies, so...

They have a ten-day window
at the telescopes,

but clouds at any one of them
could obscure the signal

from the black hole
and ruin the data.

So, each day,
Shep needs to make a call.

If the night is "go" or "no go".

Whether or not you energise
the Event Horizon Telescope
on any given night,

that's the biggest decision
you can make.

If you make the right one
then you've got great data.

If you make a wrong decision,

you've expended huge
amounts of resources.

Each night of observation will
not only cost thousands of pounds,

but also eat up their limited
hard drive space.

Shep needs five nights of data

to stand the best chance
of making an image.

Judging the weather conditions
across the world will be critical.

It might go above
in the next couple of days.

That looks good.

If you make the wrong "go"
or "no go" decision,

you may have jeopardised
your ability to image a black hole

and that's what consumes us
when we're in that room.

Hey, Kazu.

The communication and
weather reports are online.

Now Shep needs to make sure
the telescopes are ready.

We want to make sure that
we understand where things stand

by the end of today
because if something

is not technically ready, then we
really do have a problem.

In Hawaii, the volcano Mauna Kea
is home to two observatories

in the network.

The James Clerk Maxwell
Telescope

and the Submillimeter Array.

Remo has arrived from Europe,
but the equipment still isn't ready.

Hey, Jonathan. Oh, hi, Remo.

How's it going? Not too bad.

Lead engineer Jonathan Weintroub

is still fitting the new cooling
kits to his set of data recorders.

It was installed on Thursday
and then we were like,

"Oh, damn, it doesn't
have a cooling kit."

Yeah. So we're putting in the...

Right, so proper just in time
management, I guess.

I guess, yeah.
This is kind of last minute.

This is kind of preventative
maintenance -

we don't want to suffer
a failure due to overheating

in the middle of the run.

Yeah. Now the light turned on.
Here we go. Yeah.

And there's air blowing
out of these fans, so... Yup.

Excellent.

Remo and Jonathan
must install the recorders

and check they're all working.

All right. There we go. That's it.

Yep, all of them show up. Right.

The very act of powering down
and then powering up

is to some degree stressful.

Sometimes you power something down
and it never works again, so...

..you're always relieved
when something works.

Whilst things are back
on track in Hawaii...

..high in the Atacama
Desert of Chile...

..Alan Roy has arrived from Germany
to lead the observations at Apex.

Control, Apex boss...

Here, Alan is responsible for the
most critical part of the project -

the timing.

Timing is absolutely
important to this project -

absolutely central - it's the heart
piece of the whole experiment.

You're putting in a lot of effort,
a lot of money, a lot of time,

and it's all hinging
on getting the timing right.

The Event Horizon Telescope
network is so large,

the emission from the black hole
will arrive at each telescope

at a different point in time.

What's more, the Earth rotates.

As it spins, the position
of the telescopes in space

constantly changes.

If the team can't record
the time the signals arrive

to within a millionth of a millionth
of a second,

the telescopes will fail
to combine as one.

To sync the telescopes together,
the team have spent $2 million

on some of the most accurate
atomic clocks in the world,

called hydrogen masers.

This is the hydrogen maser.

This clock keeps time to about
a second in ten million years.

Of course, we don't wait
ten million years to measure it.

Alan must keep this clock
at a stable temperature

so it can run precisely.

But there's a problem.

The chamber used
to cool it is broken.

The bearings have seized
and we've got no cooling,

so that means the chamber overheats

and the maser is then
not very happy.

A faulty maser
could be catastrophic.

In the remote Atacama Desert,

it's too far
to call out an engineer.

Alan has only one
improvised option available.

The solution is to crack open
the door of the chamber

so the excess heat from the maser
can come out through the door.

Makes me a little nervous, but the
clock we have to take on faith, yes,

that it's running as it should.

For now, this resourceful solution

has to keep the clock running
correctly,

or the whole experiment
could be at risk.

My hat is off to the folks that can
actually undertake these experiments

and observations, and make it work.

It's real, it's tangible,

and it's extreme and abstract
at the same time.

There's always a risk with
these kind of measurements.

They're difficult things.

It requires so much care
and finesse

to bring all these pieces together.

Remarkably, the weather is clear
at all eight telescopes.

In Hawaii, Remo hears
from mission control.

So, just got the news, good to go.

So, ready to go and start observing.

This is the crucial moment

that over ten years of hard work
has been leading up to.

It's taken a long time
to get to this point

that we going to give it a real shot
to get an image of a black hole

and now, finally, the day is here.

Remo must ascend
to over 4,000 metres,

to the top of the volcano.

Here, two observatories,

the James Clerk Maxwell Telescope,

and the Submillimeter Array,

are part of the network.

Remo is up against the clock.

Right...

We have to start
tuning the receiver.

This mirror directs the radiation
into the receiver that we'll use.

It's like tuning a radio.

That's going.

Looking good.

At the Submillimeter Array,

engineer Jonathan Weintroub
is in charge of recording the data.

We have 50 minutes now
to run the checks

before we start recording

and high altitude doesn't
help your brain function.

You tend to make more mistakes
at altitude.

But, across the mountain,
Remo hits a glitch.

Oh!

What the heck?

He fell out of lock.

The receiver won't lock
onto the frequency.

Without a lock, the data from the
telescope will be ruined.

Remo has no option but to manually
adjust the receiver settings.

Done.

I need reading glasses.

I can't see the stupid dials
any more!

Yes, it stayed on lock.

Excellent.

All right.

The team is ready just in time.

We're all set. Good.

Great, it has a nice signal.

Attention!
Doors and roof will be opening!

Doors and roof will be opening.

Station 42. Station 42.

It's opening.

Remo directs the dish
onto the target.

Jonathan gets ready
to record the data.

Five, four, three, two, one.

Are we going?

The Event Horizon Telescope
is on the way.

After over ten years of work,

the teams at eight
different observatories

are finally fixing their gaze
on a black hole.

The team observe the emission
from black holes M87

and Sagittarius A-star,
and record data late into the night.

After a 14-hour shift, Remo must
leave to avoid altitude sickness.

It's getting close to our
14 hours on the mountain.

Getting tired, and I will go
down to the day facility, which is

a little bit lower,

but I will be sitting and monitoring
there for quite a few more hours.

But at least there will be more
oxygen there, so that will help.

Thank you for the support.
Good luck for the rest of the night.

We'll see you tomorrow.
All right? Cheers.

Over the first two days of the run,

the eight telescopes
around the world

record two full nights of data.

But in these extreme locations,
the physical,

as well as the mental, challenges

are taking their toll
on the team.

It's hard physical work each day,

and you feel it constantly
on your body,

the pulse rate is constantly
elevated at altitude.

Constant stress on the system.

We're tired.

You know, you wind up just being
up at all hours of the night.

People at high altitude are not
always thinking perfectly.

Where is it? Where is this?

Oh, so it's in front... Oh.

We had a problem
at one of the telescopes,

one of the bits of electronics
that we rely on

was giving us some crazy results.

We're at the maser right now.

Look at channel number 17.

And ultimately we fixed it because
we were in the room, we're working.

So far, the weather has been
perfect across the globe.

But on day three, at the Large
Millimetre Telescope in Mexico,

the outlook is beginning to change.

That's a scary, scary webcam.

The LMT is just completely
chaotic right now.

I mean, you saw the webcam. There's
fog, there's clouds rolling in,

it looks very, very dicey
up there.

It's clearly building up.

I mean, I'm not going to
candy coat it for you, guys.

The decision for tonight largely
rests with you,

whether we go or not.

It's a fool's game, right?

You can't predict the weather
ten hours from now,

especially the top
of an extinct volcano

with a big telescope on it.

We've got real solid good weather
at one, two, three, four, five,

six of our sites.

Six out of eight.

Those are tremendous,
tremendous odds.

Two of the key sites,
they're marginal.

The telescope in Mexico, the LMT,

and the telescope in Arizona,

have dicey weather

and so we're just going to wait.

Shep delays the "go",
"no-go" decision.

It's too close to call.

You guys have to explain these LMT
webcams to me - from one direction,

it just looks like
a vacation paradise.

And then these other views,

it just looks like you're heading
into a vortex maelstrom of hell,

and I don't understand how three
different views can be so different.

Shep has to decide.

But now there's news from
the ALMA observatory in Chile.

Hold on, hold on.

I want to make sure I understand
what you just said.

You think there's a chance

that the data from last night
from Alma are corrupted?

Um, there's a chance.

Their entire second night of data
could be corrupt.

This is a whole new wrinkle for us.

If you had extra time,
could you run this problem down?

Running it down
is probably not likely.

If the data are corrupt,

the team might now only have one
night out of the five they need.

With the weather set to get worse,
Shep has to take a risk.

I think we should make this a go
because we're not going to

tear the system apart, so we have
to assume that ALMA will be fine.

So I'm going to say
that we're going to go.

Over the next four days,
the team let the storm pass

and observe for another two nights.

We are observing the data.

Their hard drives fill up
with over six million gigabytes

of precious data -

more storage than 12,000
laptop computers.

If the team can make an image,

it could unravel one of the biggest
mysteries of physics today...

..what lies at the very centre
of a black hole.

Einstein's equations suggest
it's an infinitely small

and dense point -

the so-called singularity.

A singularity is
a physicist's way of saying,

"We do not know
what the heck is going on."

In reality, at the dense core
of a black hole,

Einstein's equations
don't make sense.

If you take Einstein's
mathematics seriously

and apply it right to the centre
of a black hole,

then you do have infinite density.

But there's
no meter in the world that,

when you measure something,
goes, "Infinity!"

Nature is kind of grabbing us
by the lapel and slapping us

in the face and saying, "You don't
understand what you're doing

"if infinity is cropping
up as the answer."

Right now, frankly,
the interior of a black hole

is the Wild West
of physics theorists.

But the good news is,

if you have a theory that predicts
something different from Einstein

for what happens inside, there's
a good chance it also predicts

something different from what
happens immediately outside.

It's so exciting to finally,
hopefully, start getting some clues

from the Event Horizon Telescope.

A picture of a black hole
will take theory into reality.

It could be the best
physical evidence scientists have

to figure out the mysteries
deep inside

and could pave the way to
a so-called theory of everything.

It's seven days into the run.

At mission control,

the team must now decide
on what could be

the final night of observation.

This will be our fifth night.

This way, we'll have Apex and ALMA

at one end of a very
sensitive baseline,

with really good weather
at the other end of the baseline.

The weather looks clear
around the world.

All right, so we're a go
for tonight.

Everybody, let's make it count.

For the last time,

light from around the
black holes is being recorded.

In Chile, Alan Roy and the team

finish what's been
a tiring eight days.

This is coming up to the end
of the last run.

We've got maybe three minutes.

I'm feeling weary, but content.

The team have recorded their target
of five nights of data,

but only when they combine
all the data together

will they know
if they can see a black hole.

This is the interesting part,
it's almost a game of bluff.

You've now spent
more than a week here,

the telescope's observed
through the night,

and we still don't know
if anything will come out of this.

Back at mission control,
Shep is reflecting on the team's

extraordinary accomplishment.

This is the beginning of the end,
right?

I mean, this is not the end
by any stretch of the imagination.

Even though we have all these disks,
they could get lost in the mail.

There are no back-ups.

It's very, very difficult
to copy all this data.

So, we're just a little nervous
about some of that.

You know, we have a lot of work
to do. A lot of work to do.

But we've taken this first big step.

We humans love exploring things
to the limits of what's possible

and the event horizon
is the ultimate limit.

I look at the audacity
and the bravery, frankly,

of the people who came up with a way

of actually taking
this incredible challenge

and turning it into something
that they are measuring today.

It's mind-boggling.

At the South Pole, after five months
of winter darkness,

flights resume once again.

Now the team can ship the last
remaining hard drives

holding the precious black hole data

back to Massachusetts and Germany,

and complete the processing
from all eight telescopes.

This is where
a lot of the action has been

because all the drives
that you see here

came from all over the globe,

all the sites have sent their
drives here,

and this correlator
has been crunching through

all of these drives.

Five months since the observations,

the team can finally see
if the telescopes linked together.

This one's from Spain.

This one's from Hawaii.

This one's from Mexico.

So you're really seeing, kind of,
a UN of the astronomy world here.

We're basically taking the light
that was recorded from these sites

out of the deep freeze,

re-animating it,
and then combining it

as though it was being combined
for the first time.

But data expert Vincent Fish
finds a problem with the timing.

This is... This cannot be right.

BLEEP

I'm... I'm amazed that nobody...

Hold on, hold on.

Oh, sweet Jesus.

They have discovered
one of the network's atomic clocks

in Spain was faulty.

You're really getting
just random noise here.

Yeah. OK.

We're pushing really the recording,

and the technology,

and the resolution
to its absolute limits.

And when you push something
to the limits like this,

you start uncovering these problems.

There is a fix to this.

I think we can correct for it,

so we don't face this problem again.

Wow, look at this.
This is the...

..the delay.

Whilst the team resolve
the timing glitches...

..in Cambridge, scientists
from Arizona, Europe and Japan

have come to test how to turn
the new data into images.

The big challenge that we face

in this technique of the
Event Horizon Telescope

is that we don't have all the pixels
in the image, if you will.

We have some of the pixels.

So the art is trying to figure out
what the entire image looks like

without having, you know,
everything that we'd like to have.

The team will test different
computer algorithms

to see if they can create
an accurate image,

but they won't attempt it on the
target black holes just yet.

First, we're putting on training
wheels, right?

We're taking baby steps

and we're trying to use the
algorithms that we want to use

for Sagittarius A-star and M87,

but on well-known sources
that are much brighter.

These bright sources come from
matter swirling into what's believed

to be a feasting black hole.

As the black hole accelerates
the matter, it rips it apart...

..and launches jets of radiation
into space.

These are quasars.

They can kick out more energy
than a billion stars,

leaving a signature jet
that's visible across the cosmos.

If we can get really good images
on those sources,

then we know we'll be ready
to go to the next phase.

Imaging scientist Katie Bouman
is leading one of the teams

trying to make
an image of the quasar.

It's really exciting -

the first time we're actually trying
to make an image with the data.

So here is 120...

The quasar is too far away
to see the black hole itself.

But the team know what
the jet should look like

from existing telescopes.

But, two days into this workshop,

the algorithms are not producing
one consistent image.

I can make an image that looks
like that and that's ridiculous.

We get a lot of different
kind of structures come out

from the same data -

that's not a vote of confidence
in those images, I guess.

Physicist Mareki Honma is also
not getting a clear image.

Here, it's a very bright spot,

so we believe there is something.

But the whole area,

it just looks like noise.

If the team can't get the algorithms
to work for the quasar,

they won't be able to make an image
of the black hole.

The team work for a week
adjusting the computer code.

Finally, the algorithms
start to work.

And the team can see the quasar jet
in more detail than ever before.

I see this jet-like
kind of structure shooting out.

It's... It's incredible.

Look at all the structure.

The team has produced images now,

after going through this whole
pipeline, that seem very robust.

So that's the key.

You have to be so confident
in your techniques

and your data handling that
you trust them

because for Sag A-star, or for M87,

we have no idea
what we're going to see.

After over ten years of planning...

Lights. Yes!

...over £30 million,

and the combined brainpower of over
200 international scientists...

Attention, attention!
Doors and roof will be opening.

Control, Apex boss...

..finally, the time comes to try
and make an image of a black hole.

This has been a huge process,
a very, very careful process,

and the imaging team is now getting
the first set of data they can use

to make a photo of a black hole.

It's really exciting.

We just got the data and that's, you
know, what we've been waiting for

for many years, so it's a pretty
exciting time for us.

This is the moment
when we finally get to see

what a black hole might look like.

Each member of the team
loads the data

and starts running their algorithms.

Are we going to...?
Are we doing this?

OK? OK, ready? Ready, set, go.

Going, going, going!

The algorithms are producing
some tantalising images.

This is very early stages.

This is exploratory surgery.

Patient is on the table.

Open the patient up,
we're looking inside,

we're trying to find out
what we see.

Each member of the team needs to
zero in on one consistent image.

That is interesting.

Whoa. Oh!

I'm getting something pretty
similar - a little bit.

And, with the data
for the black hole M87,

one image soon becomes clear.

I see a circular feature.

An image the likes of which
astronomers have never seen before.

What I'm seeing on the screen
here is pretty startling.

This is a case where
the signal is so clear

that it kind of hits you on the head
with a hammer.

If this holds up...

..it's going to be the discovery
of my lifetime,

and I think of many other
people's lifetime, and...

..it's really sobering to see

what a black hole looks like
for the first time.

The image shows photons of light
being bent into a ring

by the power of gravity.

In the centre, a black hole
with a mass of six billion suns

is swallowing the light
that strays too close.

It is profound evidence

that confirms
the existence of black holes

first predicted
by Einstein's theory of gravity.

This shows us that space time
is distorted

in the way that Einstein felt it
would be at the black hole boundary,

at the most extreme environment
in the universe.

These photons are struggling
to get away from this black hole...

..and the black hole is tethering
them with its immense gravity.

And, every once in a while, some
of them can just get away

from the black hole and come to us.

So we're seeing the very definition
of this surface...

..where light is lost forever.

In 2019, the Event Horizon
Telescope team verified their data

and released their results
to the world.

This is a ground-breaking
scientific result.

But, with plans for more telescopes
and even better data,

a picture of Sagittarius A-star
could soon be next.

When Galileo first proved that you
can take pictures of the sky

with telescopes,
that didn't end astronomy -

it started it.

And in the same way, the most
important scientific legacy

of the Event Horizon Telescope
is going to be

the fact that it creates
an entirely new field of science.

If I know astronomers,
when this thing is done,

they'll go, "Ooh, what else
can we do with this?"

I can certainly envision
that 10, 30, 50 years from now,

our description of black holes
are going to be

completely, radically different.

For Shep and the
Event Horizon Telescope team,

they hope this
is just the beginning.

We're not done.

We don't actually like things to be
tied up with a bow and finished.

This shows us how black holes eat
and how they feed

in the way that has been
impossible up to now.

This, most of all, signals
a whole new direction in astronomy -

and that's rare.

That is... It's really
extraordinary.