Nova (1974–…): Season 48, Episode 20 - Universe Revealed: Black Holes - full transcript

Take a seat on the ultimate thrill ride to explore nature's strangest and most powerful objects. Black holes can reshape entire galaxies, warp the fabric of space and time, and may even be the key to unlocking the ultimate nature of reality. A new generation of high-energy telescopes is bringing these invisible voids to light, showing that "supermassives" millions or billions of times larger than our sun lurk at the center of nearly every galaxy, including our own.

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♪♪

Something is hiding
in the darkness.

Invisible objects
of unimaginable power

that could hold the key to
solving the mysteries of space,

time, and the universe itself.

To me, a black hole is

the greatest exhibition
of nature's mysterious powers.

You literally can't see them.

And that's what makes them
extremely mysterious.

They are bizarre quirks
of nature.

When we're studying black holes,



we're right on the edge
of human knowledge.

And yet, they are sculptors
of the cosmos.

The jets from black holes are so
powerful, they can affect

the whole shape and nature
of a galaxy.

Even shaping our own galaxy,
the Milky Way.

We had hints that black holes

were at the center of all
of galaxies, like our own.

Can we lift the veil...

Forget the one-way trip to Mars.

I'm going in the black hole.

And reveal their secrets?

Fermi revealed something
completely astonishing

and unexpected.

We've never seen anything
like it.



Finding these little pieces
of the puzzle that did not fit

is super-exciting.

But if you really want to
understand

the deepest questions
of the universe,

you have to understand
black holes.

♪♪

"Black Holes,"

right now, on "NOVA."

♪♪

♪ See me when I float
like a dove ♪

♪ The skies above are lined
with trees ♪

♪ I'm on my knees,
begging please ♪

♪ Come and take me away ♪

♪♪

As we gaze out at the Milky Way,

our eyes are drawn to the light.

Hundreds of billions of stars

serenely spinning through
the cosmos.

When we look up
at the night sky,

the stars and planets that
we see are beautiful.

But actually,
it's in the space between these,

in the dark patches,

that some of the most
fascinating things lie.

♪♪

In places where there is
no light,

objects of profound mystery
bide their time.

Awesome in their simplicity
and perfection,

we call them black holes.

A black hole

is an infinitely dense point
in space from which nothing

can escape, not even light.

It's extraordinary to think
that black holes are everywhere

in the universe,

that they have existed from very
early times in the universe.

When quiet, they are almost
impossible to detect.

We're talking about a region
of space

where, if something falls in,

we'll never know about it
ever again.

♪♪

They hold the power to shred
stars and worlds,

but also, the potential to shape
galaxies...

Black holes are one of the most
fundamentally important

singular objects that might
dictate how galaxies

form and evolve.

It's natural to fear them,

but we're learning that
they're essential.

You can't live with them,

but you also can't live without
them.

♪♪

And they may hold the secret
to the ultimate fate

of the universe.

Black holes,
on a fundamental level,

challenge our understanding
of physics,

of the way that everything
in the universe works.

Black holes are the most
mysterious objects

in the universe, fullstop.

♪♪

To understand black holes, we
have to start at the beginning.

At the moment of birth.

Black holes that are a few times
the mass of the sun

probably formed from giant stars
that were maybe about

20 to 30 times
the mass of the sun.

♪♪

Enormous stars burning bright
blue with intense heat.

But the brightest stars
are the shortest-lived.

A star is a big ball of gas,
right?

There's outward gravity
pushing in, right?

The thing wants to collapse
in on itself

under its own self-gravity.

But the fusion that's happening
within the star's core

liberates so much light that
the outward radiation pressure

prevents the collapse
of that star.

But eventually, that gives up.

A star like that can burn
through its nuclear fuel

in just a few million years.

♪♪

And when its power source runs
out,

it collapses under its own
gravitational pull.

There's so much material
that's collapsing during

their final few moments
that they create this massive

dense ball of neutrons

that continues to collapse.

A star 20 times the mass
of our sun or larger...

crushed by the force of gravity,

until the star disappears,

leaving only a ghost behind.

♪♪

A black hole.

♪♪

This transformation does not
await all stars.

Smaller, less massive stars,
like our sun,

eventually become burnt-out
dwarves when their fusion stops:

slowly fading cinders.

But it's possible that almost
all the massive stars

that dominated the early
universe formed black holes

when they died.

Because black holes are simply
what happens when enough matter

is crushed into a small enough
volume,

dramatically warping the space
around it.

A river is a great analogy
for the area right around

a black hole.

Here I am far upstream,
and the water is fairly placid.

It's not moving too fast.

If I were to get into the water
here and swim across,

I'd be able to do that
very easily.

In the same way, if you're
far away from a black hole,

you'll be able to get around
with just a normal spacecraft

without too much trouble
and simple propulsion.

♪♪

But the closer you get
to the black hole,

the stranger things become.

The collapsed massive star
crushes down

so small and so dense,

it ceases to have a physical
surface at all,

becoming an infinitely small
point in space,

exerting a profound effect
on the space-time around it.

As the water gets closer
to the waterfall,

the speed of the water
increases.

If I were to jump into the water
right here,

the speed of the current
would be so intense

that I wouldn't be able to swim
against it,

and I would be gradually pulled
closer to the edge

of the waterfall till I reach
a point of no return.

And that's the same around
a black hole.

♪♪

Just outside the black hole,
the fabric of space itself

actually stretches inward
towards the center.

Not even stars, planets, people,
even light cannot escape

the pull of a black hole.

It's like a waterfall
in the fabric of the universe.

The black hole's gravitational
reach is not infinite.

People have this idea
that black holes suck,

in the sense that they suck
everything into them,

but that's not true.

Black holes can only eat things
that are within

a certain distance away
from them.

If you're further away,

then the black hole has no way
of eating you.

But once in its grasp,
you are lost forever.

And this is the key
to their mystery.

The black hole's interior
is hidden from view,

cut off from the rest of the
universe by a boundary in space:

the event horizon.

Beyond this point,
there is no escape.

♪♪

As we approach
the event horizon,

we get our first glimpse of the
true weirdness of black holes.

Ever since Einstein,

we've viewed the fabric of the
universe

not as something static, but
instead something that's fluid,

something that bends and warps
around objects with mass.

We call this space-time,
a combination of space and time.

See, Einstein's insight was to
realize that these two things

are intimately connected.

That when an object has mass,
it not just bends space,

but changes the passage of time
itself.

In particular, the effect of a
mass is to slow time down.

In the region around
the black hole,

the warped space-time

elongates light waves,
distorting color.

The event horizon is the place
at which time stops

when seen from far away.

Someone who's outside
the black hole will see you get

redder and redder...

And your time will slow down.

And you'll kind of pass through

the horizon, disappear forever.

♪♪

♪♪

Black holes are like waterfalls
in the fabric of the universe,

where space contorts and time
itself grinds to a halt,

ensnaring light,

making them lockboxes for the
universe's ultimate secrets.

♪♪

It is said that fact is
sometimes stranger than fiction,

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

Black holes are stranger
than anything dreamed up

by science fiction writers,

but they are firmly matters
of science fact.

The vast majority of black holes
are small...

Less than 20 miles across...

And they usually wander alone
through space.

But if we turn our gaze towards
the center of the Milky Way

and journey inwards,

through the gas and dust
that shroud the galactic core,

signs of something altogether
different appear.

If you simply observe

the stars in the very heart of
our galaxy over about 20 years,

you will observe them orbiting
nothing.

At the center of this swarm of
stars is darkness.

It's a void.

Scientists name this invisible
enigma Sagittarius A-star,

although it is not a star
at all.

Can you imagine

how massive that object
has to be to be able to pull

entire stars into orbit?

They believe it to be
a black hole

more than four million times
the mass of our sun...

Many thousands of times
more massive

than any other in the Milky Way.

How did this monster

come to live at the heart
of the Milky Way?

Sagittarius A-star
is a supermassive giant

around which the entire galaxy
spins,

raising intriguing new questions
about the role of black holes

in our galaxy and the universe.

How did it get there?

How did it get so big?

And what can it tell us
about how black holes

shape the cosmos?

Would we even be here today

without Sagittarius A-star?

Just a few minutes away
from the 26th flight

of the shuttle Columbia,

with a crew of five.

♪♪

I think a night launch
is particularly exciting.

Go for engine start.

We have booster ignition
and lift-off of Columbia.

Roger roll, Columbia,
we're looking in.

Chandra is huge.

It's about the size of
a school bus.

It's the largest telescope

to ever be launched
by the space shuttle.

♪♪

SRB separation is confirmed.

You're stressed about
the astronauts onboard

that are literally risking
their lives to help us

get a better view
of the universe.

In the summer of 1999,

NASA's flagship telescope
for X-ray astronomy

sets off from the space shuttle
cargo bay.

♪♪

Even two decades into its voyage
of discovery,

Chandra remains by far
the most powerful observatory

that we have to observe
the high-energy universe.

Almost 83,000 miles
above the Earth's surface,

at its highest orbit,
Chandra scans the sky

with eight high-precision
mirrors engineered

to detect X-rays emitted
from extremely hot regions

of the universe.

For 14 years, it searches
among the exploding stars

and clusters of galaxies.

But then, on September 14, 2013,

Chandra chances on something
else entirely.

Chandra wasn't looking for this
at all...

Just happened to be looking
nearby.

So it was a total surprise.

♪♪

As the telescope gazes into the
constellation of Sagittarius,

it aims to observe a large cloud
of hot gas.

But unexpectedly,

it records a flash of X-rays
just a few pixels across

coming from the seemingly empty
space in the galactic core.

♪♪

When we see something get very
hot for a very short period

of time, we get very excited.

Something is causing it...
Something we can't see.

♪♪

Some scientists believe
the flash seen by Chandra

is caused by an asteroid...

♪♪

Ripped apart and burning up
in a blaze

hundreds of times brighter
than the sun,

releasing a burst of X-rays
that Chandra can detect

almost 26,000 light-years away.

If we see a level of X-rays
being produced that's so bright,

it can't be explained

by any other process,
then we know that there must be

a black hole there.

It's the behemoth at the center
of our galaxy.

Sagittarius A-star.

♪♪

You can take a telescope like
Chandra and watch a black hole

have a small snack,

maybe like a human might have a
little biscuit in the afternoon.

And it's something like
an asteroid.

And there will be a small
sort of X-ray signature

from that event.

So it's incredible

that we can actually observe
Sagittarius A-star,

which lies 26,000 light-years
away,

actually eating something.

But Chandra does not only look
inwards.

It also looks out,
beyond the Milky Way.

At the center of almost every
large galaxy Chandra peers into,

it finds evidence that our
galaxy is hardly unusual.

We started to spot

X-ray sources of light
everywhere around the sky,

and we started to realize
something weird was going on

in the centers of galaxies.

At the heart of most galaxies,

we think now there are
supermassive black holes,

black holes that weigh millions
or billions of times

what our sun does.

It's incredible that our modern
X-ray telescopes, like Chandra,

allow us to map out

where these fascinating black
holes are across the universe.

♪♪

Supermassive black holes seem
to be an integral feature

of the cosmos.

But these supermassive objects
raise questions.

How do they form?

And why are they so big?

These things form over millions
to billions of years.

So we can't watch this
happening.

We can only see it at various
different stages

throughout the universe.

And so we have to just piece it
together like a jigsaw puzzle.

Some scientists theorize
that the biggest and oldest

black holes did not start life
as stars at all.

In the very early universe,
we believe that

you could have formed
very massive black hole seeds

by direct collapse of gas.

So these black holes are called
direct-collapse black holes.

But the jury is still out.

It's possible that
Sagittarius A-star formed

by direct collapse of material.

What I think is more likely
is that it formed by

the death of a star.

However Sagittarius A-star was
born, one thing is certain:

it had to grow.

♪♪

The newly formed Sagittarius
A-star begins to feast,

gorging itself on not just
asteroids,

but bigger game, like stars
and massive clouds of gas.

As it snacks on these

nearby objects that wander
into its path, it gets bigger

and bigger and bigger.

The black hole gains more mass

and more gravitational power.

But black holes that are a few
times the mass of the sun

can never grow to be
a supermassive black hole

just by eating gas and stars.

How did Sagittarius A-star speed
up its growth?

On September 14, 2015,
an international team

of astronomers finds a clue,

the aftershock of a truly
titanic interaction:

two colliding black holes.

So the merger of two black
holes, as you might imagine,

is spectacularly energetic.

It is so energetic that it
causes ripples in the fabric

of space-time itself
that propagate outward

at the speed of light.

And we have detected these
ripples here on Earth

with something we call LIGO.

LIGO is an instrument that works
by sending laser beams

that bounce off of mirrors.

When a gravitational wave
passes by the Earth,

this changes the timing
of the interaction

of those laser beams.

The stretching caused by
a merger here on Earth

is absolutely minuscule.

But with advanced technology,

LIGO was able to do it.

♪♪

Many scientists now think that
mergers like this are the key

to how supermassive black holes,

like our own, grow so big.

♪♪

When another black hole wanders
towards Sagittarius A-star,

they become locked in a
gravitational embrace.

First, it is sort of
an intriguing dance.

They kind of dance around
each other,

lose energy, and slowly spiral
into each other.

♪♪

This dance gets faster and
faster and faster and faster

until they finally merge.

♪♪

Sagittarius A-star cannibalizes
its cousin...

creating ripples in the
fabric of the universe itself.

These mergers were fundamental
to making Sagittarius A-star

the monster that we see today.

They happened billions of years
ago, right at the beginning

of Sagittarius A-star's life.

♪♪

More meals follow.

Stars, gas clouds...

Whatever strays too close.

And as our black hole's mass
and influence grows,

its surroundings
are changing, too.

♪♪

The sea of stars and gas
around the black hole

continues to grow...

gradually evolving
into the familiar spiral disk

we call home:

the majestic Milky Way
with the supermassive

Sagittarius A-star at its core.

So when Sagittarius A-star

becomes a supermassive
black hole,

it really comes of age,
and it acquires the ability

to have a transformational
impact

on the evolution
of the entire galaxy.

Black holes are the ultimate
engines in the universe.

When you think about a car,

the first thing
you're interested in is,

how does it work?

You open the hood and you look
at the engine of the car.

With a black hole,
you're asking,

"I want to lift the hood up
on an entire galaxy.

How does a galaxy power itself
at its very heart?"

♪♪

The center of the young galaxy

is rich with swirling gas
and dust:

more offerings to feast on.

♪♪

This is a gluttonous period,

a new era for
Sagittarius A-star...

when the invisible giant has
the power to sculpt the galaxy.

♪♪

As Sagittarius A-star
is gorging on food,

the food that
it's waiting to eat

is swirling around the
central supermassive black hole

in this violent, energetic disk,

and the matter is ripped apart
by the gravity,

which causes the protons
and electrons to then make

these twisted
magnetic field lines.

Everything is rotating and
orbiting,

so at the center
of this black hole,

this accretion disk,

you have
a twisted magnetic field,

almost like a tornado.

Right before material

approaches that event horizon...
That,

that eternal prison,
if you will...

It can be redirected instead.

And from the blazing tumult,

the super-heated material

is thrown out
along the magnetic poles...

two high-powered jets
launched out into the cosmos.

They can reach hundreds of
thousands of light-years

from the black hole itself.

It's only recently
that we've begun to grasp

the huge influence of
Sagittarius A-star on our galaxy

and the role that those
super-powered jets

may have played.

Engines start.

One, zero, lift-off.

The Delta rocket carrying
a gamma ray telescope

searching for unseen physics
in the stars of the galaxies.

♪♪

Just over a decade ago,

astronomers made a completely
unexpected discovery.

It was
this whole piece of our galaxy

that we never knew
was there before.

It would be like finding
a brand-new continent on Earth.

The Fermi space telescope was
built to detect gamma rays,

the most energetic radiation
in the universe.

Fermi is roughly
100 times as sensitive

as previous
gamma ray telescopes.

So it has the sensitivity

to see things that we
just simply couldn't see before.

Orbiting the Earth
once every 96 minutes,

Fermi constructs
a map of the cosmos

and uncovers
an invisible landscape...

The most energetic regions
of the galaxy

highlighted across the sky.

So we pointed
the Fermi telescope

towards our very own
supermassive black hole,

and we had a picture of what
that area sort of looked like...

In our minds, at least.

But then Fermi
revealed something

completely astonishing
and unexpected.

Emerging from the plane of
the Milky Way

are two enormous bubbles,

each one stretching
25,000 light-years,

together reaching
half the width of the galaxy.

If you could see in gamma rays,

the Fermi bubbles would be about

the biggest thing
you see on the sky.

They look like huge dumbbells

going straight up
and straight back

from the center of
the black hole.

The bubbles match the imprint
scientists expect

an enormous eruption
from Sagittarius A-star

to leave on the galaxy.

We had had some clues that
the Milky Way might have had

a more energetic
and active past,

but the incredible thing about
the Fermi bubbles

was that they suddenly gave us
concrete evidence

that the Milky Way
was much more energetic

at some time in its history.

♪♪

When our black hole gorges,

it unleashes a towering inferno
of super-heated matter.

A supermassive black hole

can impart something
like a trillion,

trillion atomic bombs'
per second

worth of energy.

If we were to be
in the line of fire

of one of those jets,

it would be catastrophic for us.

We'd be vaporized.

♪♪

Every planet in the jet's path

could have its atmosphere
stripped away.

♪♪

But further out in the galaxy...

these violent outbursts from
Sagittarius A-star

may have played
a surprising role.

Because the hot gas displaced by
the supermassive black hole

has a calming effect
on the galaxy that hosts it.

In order for stars to form,

you need
very cold and very dense gas,

because stars form through
the collapse of material.

So, instead, if you have

something like
a supermassive black hole

that is sending out
these hot jets

into the galaxy around it,

those jets are going to
heat up the gas.

Now the gas is
no longer cold enough

to collapse
and then form a star.

There's a symbiotic relationship

between the supermassive
black hole at the center

and its host galaxy.

And this relationship determines

the rate at which stars form,
planets form,

and ultimately, in some sense,

why we are here.

♪♪

♪♪

After spending billions of years

consuming the gas, dust,
and stars around it,

there is little left
to feast on.

Our black hole falls dormant.

Today, the Milky Way
has entered an era of calm

and Sagittarius A-star
is a sleeping giant,

the enormous bubbles spotted by
the Fermi telescope

echoes of a lively past.

You never want to assume that

you live at a special time
in the history of the universe.

But it is kind of a special time

that, right now,
the black hole is very quiet,

and it must have been
much more active

a few million years ago.

As our understanding has grown,

our picture of black holes
has transformed,

no longer sinister monsters,

but agents of
change and creation.

Sculptors of the cosmos.

We are far from

unlocking all the secrets

of our galaxy's
supermassive black hole.

And in fact,
the stuff that remains

is probably
the most interesting:

what happens inside
a supermassive black hole

and at its event horizon.

Black holes challenge
the most basic principle

about the predictability of
the universe

and the certainty of history.

♪♪

Nothing could get out of
a black hole.

Or so it was thought.

Black holes are where

two of our greatest theories
collide and clash.

So you've got these two
primal forces in the universe:

gravity, which we all understand
and feel with our bones.

And then you've got
quantum mechanics,

which governs
the theory of the ultra-small,

how atoms
and nuclei come together.

The black hole

is where gravity and
quantum mechanics finally meet.

SYLVESTER JAMES GATES, JR.:
When we try to take the
mathematics of the very large

and try to combine that with

the mathematics of
the very small,

instead of matching...

They get into a fight.

And so we don't have a
consistent way to describe both.

We can begin to probe
this deep mystery

by investigating the heart of
Sagittarius A-star.

Scientists have studied
dozens of stars in its orbit,

some passing just
a few billion miles

from the event horizon,

a hair's width
on galactic scales.

And these fly-bys could have
catastrophic consequences...

♪♪

Because some of these stars
likely have planets in orbit.

Planets that
may stray too close.

Moths to a flame.

Pulled from their parent stars

towards the abyss.

So imagine you're some
alien civilization

looking up at your lovely
home star, S2, in the sky.

And one day, the thing starts
wandering closer and closer

to what we call
the tidal disruption radius

of Sagittarius A-star,

this four-million-solar-mass
black hole.

If you fell into a black hole,

you'd pass the event horizon,
and actually,

bizarrely, you'd see nothing.

There's no physical barrier,
there's no big line in space

saying
"point of no return."

You would just drift
very casually, gently

across the event horizon.

If we could stand on

such a planet and look outwards,

we'd see something spectacular.

♪♪

You would see a distorted
universe,

and in fact,
you'd see it distorted

in both time and space.

You'd see it playing out

at an amazingly fast speed.

The rest of time would
play out unbelievably fast

in front of your eyes.

♪♪

But eventually,
tidal and gravitational forces

become too strong...

♪♪

Stretching space
and everything in it.

Your feet would be pulled

more strongly by gravity
than your head,

so you'd be stretched out
into a giant string,

and eventually, you'd be
one long string one atom thick.

We call this spaghettification.

Boulders become rocks.

Rocks become sand,

whose very atoms

are then pulled apart.

Gravity and
the quantum world collide.

Ahead, the heart of
the black hole...

The singularity,

where all journeys in terminate.

Our idea of a singularity

is that everything is compressed

beyond what it can be
until it's nothing,

but yet still exists.

That is...

Wow.

♪♪

Over trillions of years,

all the stars around
Sagittarius A-star

will gradually fade
out of existence.

♪♪

Long after the last-ever sun
sets on any planet,

black holes will continue
to roam the universe.

♪♪

The final dark age.

If nothing can ever escape,

if this is some eternal prison,

is that the end of the story?

Perhaps not.

Because scientists
now believe that even

Sagittarius A-star will die.

And its death
will come at the hands of

what might seem an
inconsequential effect

first described
almost five decades ago.

So in 1975,

Stephen Hawking
published this amazing paper

showing that black holes aren't
absolutely, completely black.

They glow very, very faintly.

They have a temperature
associated with them.

And you can write
that temperature

very simply in an equation

that's just beautiful.

It links together so many
different parts of physics.

It's got gravity in it.

It's got the mass
of the black hole in it.

It's got the speed of light.

It's got constants relating to
atomic physics,

the microworld.

And it's putting
all of these together

and giving us a temperature.

Hawking's equation
has huge implications

for the future
of the black hole.

So if something
has a temperature,

it's glowing, it's radiating.

Like when you put your hand
close to a fire,

you can feel it.

And that losing energy,

for a black hole like
Sagittarius A-star,

over timescales
that are hugely long,

it's going to evaporate away.

It's going to disappear.

♪♪

Very gradually,

this Hawking radiation

will erode away
Sagittarius A-star

until, many trillions
and trillions of years

into the future...

in a final burst of light...

our black hole will disappear.

And then the Milky Way
will be completely dark

for all eternity.

So why does it matter

if these black holes
disintegrate

in the far distant future?

Well, the discovery of
Hawking radiation

raised some
profound questions in physics.

If I was to set fire
to this piece of paper

with Stephen Hawking's equation
written on it...

what happens to all that
information as it burns away,

as it radiates away?

Do we lose it
from the universe forever?

Maybe if I could sweep up
all the ash,

if I could find all the photons

and reconstruct them,

maybe I could reconstruct
that piece of paper,

even the equation written on it.

So does this also apply to
black holes?

What happened to
all the information

contained on all the material

that ever fell into
a black hole?

And as a black hole evaporates,
what happens to it?

Black holes ain't as black
as they are painted.

They are not the eternal prisons
they were once thought.

So if you feel you are in
a black hole, don't give up.

There's a way out.

If information somehow escapes
from Sagittarius A-star

as it evaporates away,

the implication is profound.

Scientists now believe
that every star,

asteroid,

planet...

Everything that ever fell into
Sagittarius A-star...

May live on,

every aspect and position

of every particle
encoded as information.

All that you would
theoretically need

to put the whole back together.

So the memory of
every single thing

that's "fallen into,"
become part of,

Sagittarius A-star
in the Milky Way

hasn't been lost.

It's still there.

It's just that
we can't access that now.

But maybe we might be able
to read the ashes of that memory

in the far future of
the universe.

But how can anything escape
a black hole's grip?

The defining fact of
a black hole

is that nothing
should be able to get out.

And yet when you look at
Hawking radiation,

it seems to be suggesting
that quantum physics

does connect up the inside
back to the outside.

We just don't really know how.

Black holes force us to

consider nature in entirely new
and mind-bending ways.

People aren't at all certain
about the resolution

to what happens when we
throw things into black holes,

as far as where
the information goes.

It's still an open question.

Maybe it gets sent to
a portal to another dimension,

maybe it gets pumped
into some other branch

of a larger multiverse.

Some people imagine that
black holes are really

just a kind of quantum fuzz,
a fuzzball.

Some people think that
all the information

that fell into the black hole

is somehow encoded on
its surface

in a hologram.

But we're not really privy to
any of this information.

And if we want to find out,
we'd have to go in.

Whatever the solution
proves to be,

it will have ramifications

far beyond
the black hole itself.

♪♪

This theory of quantum gravity
that's so elusive right now,

that is what we would need
to describe

what's happening
inside black holes,

could either be
the most exciting development

to happen in the next decade or
maybe even the next century,

or it could be an alarm bell
going off in our heads

that maybe
Einstein's theory of gravity

is not
the final word on gravity.

Solving the mystery of
black holes

may be our best chance to
complete the picture of nature

that has eluded us
for the last century.

So perhaps the important thing

isn't what the answer
turns out to be.

The important thing is
that we will gain

a fuller understanding of
the cosmos

by studying
these remarkable objects.

Studying the universe has
completely changed our universe.

We have to rethink everything
over and over again.

Like, it's almost, like,
tear up the universe we know

and write a new one.

We're still a long way from

fully comprehending
the secrets of black holes,

but we're beginning to
lift the veil.

Far from being
mere cosmic aberrations,

black holes fundamentally
shape our universe.

So it's extraordinary
to think that

we might be
fundamentally connected

to something that
we didn't know existed

for the vast span of
human history.

♪♪

The beautiful thing about
black holes

is that they're such a
rich source of information.

We've learned so much
about the universe

from studying black holes:

space, time,

the very fundamental nature of
reality.

Bit by bit revealing

the deepest mysteries of
the cosmos.

We're in a golden age of
discovery about black holes.

We understand how they merge,

we've discovered
their colossal jets,

and we're beginning to see them

not just as destroyers,
but also as creators

and sculptors.

And all that
is just the beginning.

Our story's happening now,

but black holes,
they're going to outlive us

by trillions of years.

Their story
is just getting started.

♪♪