All language subtitles for T.N.F.S05E09.1080p.WEB.h264-VOYAGES_track3_[eng]

(ambient music)

- [Narrator] Black holes,
where time and space converge

under gravity's immutable power.

These extremes of nature,
once considered improbable,

are now giving up their secret.

In fact, scientists have been able

to imagine the impossible,

the black hole at the
center of our galaxy.

We can now peer into the abyss.

(dramatic upbeat music)

(spacecraft whooshing)

(satellite whooshing)

(rocket rumbling)

(particles hissing)

(graphic whooshing)

(graphic whooshing)

(dramatic music)

The concept of black
holes was first proposed

by the German astronomer and
physicist Karl Schwarzschild,

barely a year after Albert
Einstein had published his works

on the field equations
of gravitation in 1915.

Schwarzschild wrote to Einstein
from the German trenches

of the First World War, detailing
his mathematical results

of his gravitational equations.

Sadly, the brilliant scientist
later succumbed to a skin

disease he contracted in the
trenches at the age of 42.

The existence of these so-called
frozen stars was written

about and debated for 50 years.

In 1967, physicist John
Wheeler coined the term

black hole to describe
these impossible objects

and the conditions that would create them.

New Zealander Roy Kerr
advanced the concept

by publishing a solution to the equations

which would require that black hole spin,

like all other astronomical bodies.

Then Stephen Hawking and Roger Penrose

theorized that black holes
could emit radiation,

now called Hawking radiation.

The theory; if a black hole
had no material to absorb

and grow, then a black
hole could evaporate,

effectively shrink, and die.

All scientists had to do
was find one to study.

Quasars, the tremendously
bright distant objects,

were factored in as a strong
case for black hole accretion,

the only imaginable energy source

capable of such incredible luminosity.

In 1964 astronomers discovered
one of the brightest

X-ray sources in the sky,

in the constellation Cygnus,
and labeled Cygnus X-1.

The powerful source didn't coincide with

any bright optical
(rumbling)

or radio source, leaving
it in the mystery basket

of observations.

Before long, with advancements
in computers and space-based

telescopes like Hubble,
black holes were eventually

detected, or their effect on
their surrounds were detected,

as black holes, by their
nature, can't be seen.

- Black holes are these
incredibly fascinating

but mysterious objects, we
know they sit at the hearts

of galaxies, and they drive
how those galaxies grow,

and how those galaxies die.

They swallow gas and stars up.

They're also these incredibly
enigmatic and mysterious

objects that live at the
boundary between our two great

theories of physics; general relativity,

which describes gravity,
and quantum mechanics,

which describes the smallest
things in the world.

- Black holes are
literally gravity run amok,

they are purely gravitational
objects predicted

by Einstein's theory
of general relativity.

And their most notable
and terrifying feature is

that things go in and
they never come back out.

- Wonder comes to my mind first.

Such objects were never expected

to exist in nature until very recently.

As a matter of fact, I
was a complete skeptic

about black holes as
recently as 20 years ago.

- Black holes are places
where Einstein's theory

of general relativity is the whole story,

not merely a perturbation
on top of Newton's theory,

which explains the dynamics of
planets in our solar system.

As a result, black holes
provide a unique environment

in which to probe general
relativity, specifically,

and strong gravity, generally,

and its implications across the cosmos.

- If you want to make a test
of the fundamental theories

of the universe, you want
to go to the most extreme

laboratories in the universe,
and a black hole is that.

- Seeing a black hole
actually allows us to

not only know they exist,

and not only know an event horizon exists,

it also allows us to test some
of the very basic predictions

of the theory of general
relativity of Albert Einstein,

which really describes space and time

in its completeness, and that
has never been tested before.

- If you like Einstein's
theory of gravity,

then black holes are, you know,

one of the most interesting
examples of this theory,

and this is my role within this project,

I am a theorist, I work with, you know,

equations and simulations,
and my role is to

try and understand whether
the image that we produce

corresponds to the predictions
of Einstein's theory,

or maybe to something else.

- From the physics side

I find that more an interesting
question, that this is

basically some kind of rent or
terror, maybe, in space time,

and a place where we don't
understand the physics and

have a lot of serious questions
about information theory.

- I was very excited the first
time I saw the first image.

For a long time this
was purely theoretical.

We were predicting that we
would see certain features

in the image, but we didn't
really know was it really there,

and now we know.

And it was exciting that
all of that uncertainty

collapsed in that moment.

(dramatic music)

- So as the magnetized gas is
falling onto the black hole,

it heats up, and therefore
generates the light

that we then see.

Now, from our daily experience,
we expect that light travels

on straight paths and
straight trajectories,

we call them rays.

Here, the situation is very different,

we have a black hole sitting right there.

So what the black hole is doing,

it is deflecting and bending
the light rays away from the

straight paths that we
understand in our daily life.

(particles fizzing)

And in fact, it can be so strong

that we can see things that
are behind the black hole

that we thought are obstructed by it,

just because the black hole
is bending the light rays

into our line of sight.

(dramatic music)

- [Narrator] Scientists began running

simulations on supercomputers.

Multiple computational
models were visualized

to better understand what they might find

in the data collected
from their observations.

- After we computed
the radiative signature

of our simulations

we have to compare them
to the observations,

and this can be imagined
as you are in a stadium

during a football match,
and you have an image,

and you want to figure out
if this person, or whatever

is on this image, is among
the spectators in the stadium,

so what you do is, you take
this image and try to match it

with all the 60,000
spectators in the stadium,

and you do this while you
rotate it, you scale it,

you increase the contrast, and
you try to figure out first

what is on your image;

is it a person, is it a cat, or whatever?

And try to match this to the spectators.

And this seems trivial, but it's not.

It's a highly computational,
demanding process.

So we need a super computer,
which we have in Frankfurt,

and we developed a
so-called genetic algorithm,

which is a very smart way
running through these images

and try to adjust them.

And this takes roughly a month.

And after this calculation time

we have maybe 10 of those
spectators which match your image.

And this is very similar
to what we do in the EHD.

So we try to compare and
match our observations

with the theoretical predictions.

- So what is most surprising
of this experience

is that we managed to get a
very good image the first time

we tried to synchronize
all of these telescope

at the same time.

It is not so surprising
that we obtained the image

that we had predicted through simulations,

because while we believe
our simulations are correct,

and because we believe that the theory

of Einstein's general
relativity is the correct one.

(dramatic music)

- In 2019, they achieved their result,

an image of the shadow
of a massive black hole

in the distant M87 galaxy.

It was a world first achievement

celebrated around the globe.

- I think we had been extremely lucky.

I'd expected that we have
to work for years and years

through many observations
until we get a final image.

And then we look at our first
source and we see that ring,

we see the event horizon,
and we see that shadow,

that dark region, and
you know immediately,

we are looking at an event horizon,

at a black hole from all
sides at once in this thing,

we see at a region where time stops.

This is very different
part of the universe

that we're seeing for the very first time.

- We want you to take an
image of a black hole.

And the problem with black holes is

that they are very small.

So you want to take a very big black hole,

which unfortunately is
very far of away from us,

and so you need a big telescope.

This telescope is a
hundred meter in diameter,

but is not enough, you
want a bigger telescope,

and of course it's impossible to build.

But you can create a virtual telescope

by joining different telescope
in different locations.

And so you can build a telescope

which is as big as the Earth.

And in fact, that's
exactly what we've done,

we joined telescope like this

with telescope on the United States,

and in one even in the South Pole

to get a very sharp image.

Actually, an image is comparable

to seeing an orange on the moon.

(dramatic music)

Black holes tell you that
are regions inside them

that cannot be explored.

And for a physicist,
this is very disturbing

and attractive at the same time because,

you know, we don't like to have
doors which we cannot cross.

And in particular, inside black holes,

physics is even expected
to to fail completely.

And so, this even adds
fascination to these objects.

- The future of the project
will hopefully going towards a

new understanding of more
fundamental questions in physics.

If this is true, that black
holes are the extreme objects

where we can study gravity,

and we know that general relativity,

which describes black
holes in the outer part,

up to the event horizon, breaks
down at the event horizon.

So the big hope is that with
more data we might be be able

to study the physics
beyond general relativity.

So maybe there might be
quantum physics ruling

beyond the event horizon,
or the combination

of quantum physics and general relativity,

which would be the theory
of quantum gravity,

which is nonexistent at the moment,

but we might learn more about this

with the help of studying black holes.

(people chattering)

- Our experiments are like an
arctic expedition; we have to

plan for months, and months,
and months in advance,

gather our equipment, and then
we have this great migration

of people to observatories
all around the world.

We stay up all night,
we run our telescopes,

and then we have this
terrible period of waiting

where we don't know if it's all worked.

We send all of our data together,

and only when it's truly combined
do we know if it's worked.

And then the even harder
part begins of analyzing

that data, and being very, very careful,

doing all the checks and balances

to know that we got it right.

(dramatic music)

- Data analysis, imaging black holes,

and doing simulations is very exciting,

it's also very difficult and
requires a lot of patience,

it's a very long process,

but seeing the final
product is very satisfying.

- The Event Horizon
Telescope Collaboration

is this amazing group of fantastic people

from all around the world,
Americans, Europeans,

people from Asia, who've come together

with all their technical
expertise and scientific expertise

to make this image of a
ring around the black hole.

(people chattering)

The future of this project
is amazing, because now that

we've seen what we're after,
we have so many more questions

to ask about it, to
push into the regime of,

can we decide, is Einstein right?

Can we study how gas really gets swallowed

by the black hole?

Can we see a giant eruption of radiation,

of particles coming out of the system?

So many things to do, we've
really only just begun.

- Now we wanna make the first movie.

Now we want to understand how spacetime

rotates around the black hole.

We'll do that by putting more
telescopes around the world

to make our virtual lens even better.

- It was a fantastic way

of combining talent from different people

in a way that otherwise
would have not been possible.

In order to take this picture
you need the cooperation,

the simultaneous observations,

of many radio telescopes
across the planet.

You need to have the
largest possible network

of telescopes taking the
same image at the same time.

(dramatic music)

- [Narrator] New goals for
the Event Horizon Telescope

were quickly set.

The M87 massive black hole
is far away from earth.

Scientists wanted to get a closer look,

and decided to image another black hole

at the center of a
galaxy, one much closer,

but also much smaller, and
shrouded in gas and dust.

(dramatic music continues)

- So if you try to look
into the center of galaxies

it's usually blocked from
you by dust and other stuff,

and the radio you can look through.

Like here, today we can look through rain,

you can look through clouds,
and we can look through dust.

And with combining radio
telescope like this together

with other telescopes in the world,

you can peer right into
the center of the galaxy

and see this black hole.

(dramatic music)

- The science result, it's
just one point in time,

in the project, and we
are always learning more

about how the instrument
works, how people work,

how new theories come about.

And so this is an evolution,
in my perspective.

It's not just one point

in time where you say,
"This is it, that's done."

It always continues.

- So we still have a lot
of mysteries to be solved,

you know, problems to be tackled.

There are still many
questions about black holes.

So I would like to study
farther in the black holes.

(dramatic music continues)

- [Narrator] The Event
Horizon Telescope targeted

the black hole in Sagittarius
A, which is the location

of the center of our very
own Milky Way galaxy.

- The long term future of experiments like

the Event Horizon Telescope
is moving this kind

of instrument into space and
starting imaging black holes

from space, which improves a
lot this kind of observation,

because it allows us to have
even higher angular resolution

than what we have now.

So we will be able, maybe
in 20 years, 30 years,

make a very accurate images

of the event horizon of a black hole.

(ethereal music)

- Not only did scientists
image the black hole,

they sampled the radio emissions

from the surrounding hot gases

giving us an audio impression;
the sounds of a black hole.

(black hole whirring)

(dramatic music)

- So far we've been looking at

the closest massive black hole,

but quasars, they are
very distant from us.

With gravity, we can
see the motion of gas,

and resolve the sizes of these regions,

and thereby measure
then the mass precisely.

So if you can do this
for many, many quasars,

many distant objects, then you
can solve perhaps the riddle

how massive black holes play the role

in the evolution of galaxies.

We now know that basically
every galaxy has at its center

a massive black hole of different masses.

We'd like to understand that in detail.

There is, if you like, a symbiosis

between these black holes and galaxies,

and we need to understand
that in order to understand

the evolution of the universe.

(eerie music)

- Studying the data from
the Event Horizon Telescope

continues to reveal more detail.

In this case, X-ray emissions reveal

magnetic lines of force through
the orbiting gas clouds.

Further study of the X-ray
emissions is currently underway

with a new space based X-ray observatory,

the imaging X-ray polar
imagery explorer, or IXPE.

(IXPE whirring)

Launched in 2021, IXPE
is designed to observe

extreme cosmic objects,
like pulsars, neutron stars,

and black holes.

This satellite is able
to study X-ray radiation

which is polarized or oscillating
in a particular direction.

This reveals more detail of the physics

of these high temperature environments,

particularly around black holes.

- But there are two other
parameters that we could

look at if we only had
the tools to do that,

and those have to do
with the polarization,

the degree of polarization,
and the position angle,

the angle associated
with the polarization.

So by doing this mission, we're opening up

two more degrees of freedom to
be able to try to understand

how are the X-rays produced,
what are the models

we have to be able to predict

the polarization that we
will turn out to measure.

So it's really exciting.

Our science working
group has studied it all.

We have seven different teams
studying different classes.

So for example, the the radio pulsars,

supernova remnants, et cetera.

And so we have, we're gonna
be looking at seven different

classes, and several
examples of those classes,

so that we get a good preliminary survey

of what polarization is out there.

(upbeat music)

(star whirring)

(star exploding)

- [Narrator] The extreme
environments created by black holes

are an opportunity to
study many other phenomena.

Neutrinos, the most abundant
particles in the universe,

have almost no mass, and very
rarely interact with matter.

They seem to be generated
in extreme objects

like exploding stars and
the fast particle jets

ejected by super massive black holes.

(jets hissing)

Colliding black holes are
another event closely watched,

as they generate gravity waves

that ripple through space time

and can be detected here on Earth.

Another recent event
detected, was the flipping

of the magnetic field
surrounding a massive black hole.

The reversing polarity
caused the visual brightening

of the material
surrounding the black hole,

and the reduction of its X-ray emissions,

during this time, the
X-ray corona disappeared,

and only when the flipped
magnetic field gained strength

did the X-ray's emissions recover.

Another black hole has
been observed devouring

a star that wandered too close,

(black hole crackling)

The ejected super fast jets of material

interacting with nearby dust clouds,

and aiding to form planets
within the material.

These singularities appear
to be an intrinsic part

of both the destruction and
creation of stars and planets.

While we don't have all the answers

discoveries like this one set us on a path

to understanding more about the universe.

(spacecraft whirring)

(graphic whooshing)