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.
♪♪
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.
♪♪
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.
♪♪