All language subtitles for How the Universe Works Series 9 Part 1 Journey to a Black Hole 1080p

MIKE ROWE: We're on
a journey to the heart

of the supermassive
black hole, M87 star.

Our mission, to investigate one
of the most mysterious places

in the universe.

SUTTER: M87 is a great
target for us to visit,

because one, it's close,
and two, it's active,

it's feeding.

ROWE:
Supermassive black holes are

the engines that power
the universe.

Supermassive black holes are
a key factor in

the birth, life, and eventual
death of galaxies.

ROWE:
And the more we study them,

the more puzzling they become.

They're the master key

to most of the unsolved
mysteries in physics.

The physics inside
a supermassive black hole are

beyond weird.

ROWE: They are the final
frontier of our understanding.

Your imagination can run wild.

Maybe it's even the source of
other universes.

ROWE: There's only
one way to find out,

to go where no one has gone
before and journey to the heart

of M87 star.

[explosion blasts]

We speed across M87,

a gigantic galaxy 55 million
light-years from Earth.

At its heart lies
a supermassive black hole,

M87 star.

It is the first
and only black hole

ever photographed.

We want to find out how M87 star
grew so large,

what lies inside, and how it
controls the galaxy.

5,000 light-years out from
the supermassive black hole,

we get our first sign of
the danger ahead.

We see giant holes
carved out of the galaxy,

starless voids thousands of
light-years wide.

SUTTER: As we approach,
we can see

that wreckage littered
around the vicinity.

It's like entering the lair
of the dragon and seeing

the bones of all the explorers
who came before you.

ROWE: What cataclysmic force
tore these giant

cavities in the galactic
gas clouds?

As we fly next to a brilliant
shaft of energy

thousands of light-years from
M87 star,

we get a clue.

It's a deadly stream of

radiation shooting out
across the galaxy,

a jet.

This jet looks like
a searchlight

or a beam from a lighthouse.

PLAIT: You're seeing this
monumental thing.

It's screaming out of
the black hole,

blasting out radiation.

When I first saw a photo of
a jet, I was like, "Whoa!"

Am I like, misreading the scale

of this image?
Because there was this

crazy Star Trek like beam
just coming out.

ROWE: In 1918, American
astronomer Heber Curtis

described the jets as
a curious straight ray.

A century later,
observatory images

reveal they pulsate with energy.

SUTTER: The images show knots
and clumps in these jets.

They show that it's just not
smooth and nice,

that there's been a history
of violence inside this jet.

ROWE: This violent energy pushes

the knots along the beams.

The knots reveal
the speed of the jets.

[train whistle blows]

It's like looking
at a fast-moving train.

Rail cars of the same color
blur into one continuous image.

But different-colored cars
stand out against the others.

It's the same with the knots
moving along the jets.

So we can figure out
how fast the jets are

really moving by looking at
knots of material coming out

from near the black hole.

ROWE: When astronomers measured
the speed of two knots,

they got a big surprise.

One is moving at 2.4 times
the speed of light,

and the other is moving over
six times faster than light.

How could this possibly be?

As weird as the physics
around a black hole is,

that's not actually happening,
nor is it allowed to happen.

SUTTER: Nothing can actually go
faster than the speed of light,

so obviously,
we're missing something here.

ROWE: The knots may seem
to break the speed of light,

but the universe is just
playing with us.

It's really just a consequence
of the fact that

a lot of this jet is
pointed toward us,

pointed partially toward
the observer on Earth.

That, in a sense, is
a sort of optical illusion

that tricks you into thinking
it's moving faster.

ROWE: It's a simple
trick of the light,

a bit like the way a spoon in
a glass of water looks bent

and distorted.

The impossibly fast speed
of the jet

is just an illusion
of perspective.

From our perspective,
it looks like the whole

thing is moving towards us
faster than light.

But really, it's just cruising
along very, very fast.

The jets aren't actually
breaking the laws of physics.

They're pushing up against it.

They're going at 99.999995%
the speed of light.

Imagine the energies necessary

to accelerate this entire jet
to that speed.

ROWE: So what could produce
enough energy to blast jets

across the galaxy at close
to the speed of light?

There is a clue far ahead.

The jets shoot out from

a tiny, brightly glowing object.

This is where things go nuts.

This is the center of
the action.

This is where
the real stuff happens.

ROWE: A ring of super hot gas

and dust whirls around
the supermassive black hole.

It's called the accretion disk,

and it shines a billion times
brighter than the sun.

If you had a ringside seat
next to M87 star,

you would probably be fried
very, very fast.

But if you were some, you know,
magical being and could survive

anything, and if you had,

you know, million SPF
sunscreen and really,

really great sunglasses,
what you would see is this

enormously bright vortex of
gas swirling this dark void.

ROWE: This bright vortex
spins around

the supermassive black hole,

at over two million miles
an hour.

PLAIT: So there's a tremendous
amount of friction as

material moving slower and
faster rubs against each other.

That's what's heating
the disk up,

and that's what's
causing it to glow.

ROWE: Scientists think that
the intense energy of

the accretion disk is
the source of the jets.

The hot, swirling gas

and dust produces
powerful magnetic fields.

As the disk spins,
it twists up the magnetic fields

at the poles of the black hole.

Energy builds.

Finally,
the magnetic fields can't

contain the energy any longer.

They snap and blast
the jets out into he galaxy.

Even many light-ears away
on the ship,

we can see this
violent release of energy.

It's like the universe's
biggest fireworks display.

Two jets streaking out of

M87 star's poles,

one shooting away
into the distance,

the other racing past our ship.

We're at a safe distance.

Other things are not.

So when these jets shoot
outward from the supermassive

black hole, they don't shoot
outward into nothing.

If a jet hits a gas cloud,
it annihilates it.

It just punches a hole
right through it.

It's like a train going
down a snowy track, right?

The gas is like the snow

and the jets are like this
freight train plowing across it.

ROWE: But here,

a freight train traveling at
close to the speed of light,

smashing into clouds of gas,

lighting our way to M87 star

as we follow the trail
of destruction.

There is evidence of similar
destruction across the universe.

In the Cygnus A galaxy,
supermassive black hole jets

have caused damage
on a colossal scale.

TREMBLAY: In many ways,
Cygnus A is like

a cosmic shooting gallery.

You see this crime scene,
this beautiful mess.

OLUSEYI: So when this jet comes
out of the nucleus of Cygnus A,

it's gonna encounter gas clouds.

At that point, shockwaves set
up, and this jet just rips

right through this material,

sending shock waves
in every direction,

creating absolute chaos.

It's hard to believe how much
devastation these jets

can cause... they're punching

a hole in the gas
100,000 light-years wide.

I mean, that's... that's
the scale of an entire galaxy.

ROWE: As we head towards
the center of

the M87 galaxy,
we enter hostile territory.

The closer to the supermassive
black hole we travel,

the more dangerous it gets.

As we approach
the central core of M87,

we start to feel it.

But all this energy,
all this ferociousness,

is powered by that black hole.

ROWE: Intense winds start
to buffet the ship.

They push away vital gas,
quenching star birth.

Could these winds end up killing

the galaxy and M87 star itself?

ROWE:
We're on a mission to explore

the supermassive
black hole M87 star.

First, we have to cross
the M87 galaxy.

It's 120,000 light-years across,

and it looks like
a giant puffball.

M87 is an absolute monster.

It's a giant,
elliptical galaxy, and that

means that, as you go from
the edges to the interior,

you see a higher and higher
density of stars.

ROWE: This vast galaxy contains
several trillion stars.

What's strange is that almost
all of them are the same color.

So as you see, you are...

Your sky is covered with
countless red points of light

everywhere you look.

ROWE: Most of these points
of light are small,

long living-stars
called red dwarfs.

So what happened to
the different-colored

stars that we see in
other galaxies?

When you create lots of stars,

you make lots of blue
and red stars.

But the blue ones
don't last very long.

They explode and are gone.

The red ones, the ones
that are lower mass,

those are the ones that live
for many, many billions

of years...
M87 hasn't made stars

in so long
that its stars are mostly red.

ROWE: We call galaxies
with mainly red stars,

red and dead.

So the only stars
that are left in these

red and dead galaxies
are billions of

year-old populations.

And since it's not
making new stars,

the clock is ticking on M87.

Essentially,
it's a dead galaxy walking.

ROWE: The M87 galaxy

hasn't made any new stars
for billions of years.

Something had
to make that happen.

Something had to deplete
or heat up or push away

the gas in those galaxies
that would otherwise go into

forming stars.

We think that black holes
in the centers

of galaxies are the ultimate
answer to this.

ROWE: So how did M87 star

kill off star formation
billions of years ago?

As we cruise towards
the supermassive black hole,

we get a clue from the strong
winds buffeting the ship.

So these winds can be
incredibly powerful and really,

really fast, right?

You think a hurricane
on Earth is bad?

You should see some of
these winds.

ROWE: In space,
winds were made up of gas

and superheated plasma.

The power that generates
the winds lies ahead

the bright accretion disk
surrounding M87 star.

Because it's so incredibly hot,

it liberates
an enormous amount of light,

and that light can drive a wind,

and so black holes
can power winds.

They power winds
with light itself.

And the more material

that's falling into
that accretion disk,

the bigger and hotter it gets,
and the more powerful the wind

is that the black hole blows.

ROWE: We understand that light
from the accretion disk

creates the winds,

but that is about all we know.

We don't know
that much about the wind.

Is it expanding in all
directions like a sphere?

Or is it aimed in jets,
very narrow

and only moving in two
different directions?

Now, measuring
the effect of the winds

isn't as easy
as you might think.

It's not like going outside
on a windy day

and doing one of these.

You have to infer
what's going on with the winds

by studying the light
emanating from this object.

ROWE: We wanted to find out
if black hole winds

expand like a bubble
or travel in narrow streams.

So we studied how iron dust from

the accretion disk blocks
the light driving the wind.

Astronomers found
the answer when they looked

in the X-ray light spectrum.

And what they detected was iron

absorbing those X-rays in
every direction

they looked around
the black hole.

That's only possible

if the black hole is blowing
out a wind in every direction,

which means that it is
definitely blowing out

a spherical wind, which is
expanding into that galaxy.

And so these black holes can
almost literally inflate

this growing sphere bubble

of gas that's outward flowing
from the heart of the galaxy.

These winds push out
throughout the entire

galaxy of M87,

transporting heat and energy
throughout the entire volume of

the galaxy.

PLAIT: What we found is that
it's expanding away

from the black hole
at a quarter of

the speed of light,
40,000 miles per second.

ROWE: And for the M87 galaxy,

that is bad news, because hot,

powerful winds kill off
star birth.

The winds can push away
the gas that would have normally

formed stars so they can

effectively quench star
formation in a galaxy,

causing it to gradually die.

ROWE: And it gets worse.

In order for a galaxy
to produce stars,

it needs lots of gas and dust,

and that gas and dust
needs to be incredibly cold.

ROWE: Hot winds from
the black hole heat up

gas clouds so they can't
collapse into stars.

As M87 star has grown,

it has slowly shut down
star formation.

As the black hole in
the center of the galaxy grows,

it has stronger
and stronger winds,

and this means it's gonna
drive out more and more matter.

And that's what makes it
a galaxy

that can no longer support
star formation.

MINGARELLI: So a supermassive
black hole can determine

the star formation happening
in the galaxy.

It can help to regulate
the amount of gas in the galaxy

and therefore the number of
stars that are formed

in a galaxy.

ROWE: Although M87 star is tiny

compared to
the vast galaxy around it,

it still controls its host.

When you compare it to
the size of the galaxy

it's sitting in,
it's like comparing

a grape to the size
of the Earth.

So to think that something so
relatively small compared to

the galaxy could have such
a profound effect over

effectively all of cosmic
history is

just this remarkable
illustration of how energetic

a black hole can be.

In the relationship between

a supermassive black hole
and the material surrounding it,

the black hole is in charge.

ROWE: Although M87 star
calls the shots, its past,

present, and future are
inextricably linked

to its host galaxy.

The view from our ship is
endless space,

calm and unchanging.

But the M87 galaxy
has a violent past,

a history of cannibalism,

death, and destruction.

ROWE: We've traveled
thousands of light-years

across the M87 galaxy,

but its supermassive black hole

is still far in the distance.

From our current position,

M87 star may look small,

but it's 6.5 billion times
the mass of the sun.

So how did it get so big?

One of the big mysteries
that we're still trying to

understand is what

controls how big the giant
black holes at the centers of

galaxies become.

And we know that
it's tightly correlated

with things like
how big the galaxy is.

Bigger galaxies have bigger
black holes.

ROWE: To understand how M87 star
became so big, we have to

investigate the history
of its galaxy.

We need to discover
how M87 star's host galaxy

grew so large.

M87 is huge.

It's a big galaxy
with a big black hole.

TREMBLAY:
It's really, really big.

It's what we call
the brightest cluster galaxy,

and these so-called brightest
cluster galaxies are among

the most massive galaxies in
the known universe.

Usually, a galaxy with the mass
of M87 is much smaller,

but M87 is puffed up
hugely. Why?

ROWE: One lead comes from
the layout of M87's stars.

As we travel through
the galaxy, we see

that the stars spread out
over an area 100 times larger

than expected.

So what scattered the stars?

Galaxies aren't static,
every galaxy is moving,

and sometimes galaxies get
very close

and can interact
with each other.

ROWE: Interact is a polite way

of describing something
extremely brutal.

Galaxies are colliding with
other galaxies, they're

cannibalizing smaller galaxies
or tearing each other apart.

MINGARELLI: Sometimes
they're like drive-bys,

and they'll warp
each other's structures.

Sometimes the galaxies have
head-on collisions and merge.

ROWE: Merging pulls in
new gas and stars,

so galaxies grow larger.

Galactic cannibalism is common.

Maybe the M87 galaxy ate
its neighbors.

But how can we find out?

We could try to identify stars

that came from
the consumed galaxies,

but that's not straightforward.

When you're trying to map out
a distant galaxy,

it turns out using their stars
is a really hard thing to do.

They smear in with the
foreground and the background.

It's actually
very difficult to see any

evidence that that galaxy
merger ever happened.

It's all smoothed out.

It's kind of like throwing
a bucket of water into a pond.

And then asking
after the waves go away

to separate which
molecules of water came from

the pail of water versus
which were in the pond.

All you see is just
mixed pile of water,

and it's similar to that
with the stars in a galaxy.

ROWE: So how can you spot
water from the bucket

in the pond water?

We need to detect
signs of disruption,

like ripples or distinct

streaks of sand
and mud thrown up

by the disturbance.

When galaxies merge,
they may also

leave a leftover
that stands out,

like a planetary nebula.

Planetary nebulae are these
bright beacons that you can

pick out and map out
the galaxy with great precision.

ROWE: A planetary nebula
forms when a dying,

mid-sized star blows off
its outer layers

after running out of fuel...
These outer layers of

gas expand, forming a nebula,

often in the shape
of a ring or bubble.

And you see this beautiful,
glowing blue-green blob coming

away from the star... these are
so much bigger than stars.

You can pick them out
very easily.

ROWE: One team went
planetary nebula hunting

in the M87 galaxy.

As they mapped the galaxy,

they picked out 300 distinct
glowing points.

The points are blue-green,
confirming they're

planetary nebulas.

Planetary nebulae are great.

They really stand out
like needles in

a planetary haystack.

ROWE: The nebula's
movements are distinct

from the stars in M87.

This shows they formed in
a smaller, younger galaxy,

not M87.

THALLER: Because we see
these planetary nebulae,

something must have happened
in this old, dead galaxy.

What was it? A galaxy collision.

ROWE: The discovery of
the planetary nebulas

shows that at some point
in the last billion years

M87 ate a smaller galaxy.

This galaxy strayed too close
to the much larger M87.

M87's powerful gravity
snared the smaller galaxy

and dragged it
closer and closer.

You could actually see
this galaxy getting bigger

and bigger and bigger
in the sky,

and it wouldn't stay
the same shape... as the galaxy

got closer, it would
begin to distort,

and your galaxy would distort,
as well, until the sky was

filled with rivers of stars.

M87 pulled in the small
galaxy and swallowed it whole.

Can you think of anything more

dramatic than the collision
of two galaxies?

ROWE: A violent history
of mergers explains how

the M87 galaxy grew so large.

Each event brought in many
millions of stars.

The collisions also unleashed
enormous gravitational forces,

scattering the stars
like confetti.

OLUSEYI:
After a collision like this,

the stars are probably ten to
100 times more spread out

than they were before.

ROWE: Some collisions
threw stars around.

Others changed the shape
of the entire galaxy.

PLAIT: If that galaxy merger
is violent enough,

it injects so much energy into
the galaxy that the stars

basically all move away
from the center,

and it makes the galaxy
much more puffy.

ROWE: Gradually transforming it
into the smooth, featureless,

elliptical shape.

Most galaxies have
a supermassive black hole

at their center,

including those galaxies
eaten by M87.

So what happened to
those black holes?

Did they merge with M87 star,
increasing its size?

M87, the fact that it's
an elliptical galaxy also

supports the fact that it's had

multiple supermassive black
hole mergers, which is how

M87 star could have
gained its sizable mass.

ROWE: Compared to its
violent history,

the M87 galaxy is now
relatively calm.

We think that in the past,

M87 star grew by gobbling up
other supermassive black holes

brought in by collisions
with other galaxies.

But we don't really know,
because physics

suggests that supermassive
black holes can never merge.

Instead, they lock together

in a cosmic dance for eternity.

ROWE: As we travel closer to
the supermassive black hole,

we pass the remnants

of smaller galaxies
eaten over the last

10 billion years.

They reveal how the M87
galaxy got so vast.

Most of these consumed
galaxies probably had

a supermassive black hole
of their own.

If M87 got so large
by eating galaxies,

did M87 star get supermassive

by consuming other
supermassive black holes?

So when galaxies merge,
all their stars and nebulae

mix together, and then also
there supermassive black holes

eventually find each other
and find their way down to

the center of the newly
merged galaxy.

Just like dropping
two stones into a pond,

they'll both reach the bottom.

They'll both move toward
the center,

and they will start to move
ever closer together.

ROWE: But do
the supermassive black holes

actually collide?

We've witnessed
the merging of smaller,

stellar mass black holes,

and we've seen supermassive
black holes get close together,

but we've never observed
them merge.

When galaxies merge,
their central,

supermassive black holes
should merge.

The first step
in the merger process,

they're sinking toward
the center of

this newly formed galaxy.

ROWE: As they plunge towards
the galactic center,

the supermassive black holes
plow through fields

of stars and clouds of gas.

They don't just run into
each other,

they inspiral toward each
other, so they're gonna

scatter stars everywhere,
and the closer they get

the more rapidly
they will orbit each other.

So things get even more
and more chaotic and crazy.

ROWE: In all the chaos,
something strange happens.

The supermassive black holes
stop moving

closer to each other.

This is a problem, and we call
this the final parsec problem.

ROWE: So what's going on?

Why do they stall?

MINGARELLI:
The final parsec problem

happens when two supermassive
black holes run out

of material to help them
to merge.

If there's not
enough stars or gas

that the black holes can
interact with,

it takes longer than the age of

the universe for them to lose
enough energy to merge.

And so the black holes
effectively stall

at this final parsec
of separation.

ROWE: The two supermassive
black holes lock

together in an eternal
cosmic dance,

close but forever apart.

But some supermassive
black holes must have merged.

It's highly likely that many of

the galaxies M87 swallowed
had supermassive black holes.

And yet, on our trip,

we haven't seen lots of
supermassive black holes,

just one... M87 star.

So mergers take place, but how?

In 2019, we got a clue

from a galaxy called NGC 6240.

This particular galaxy
looks like

the aftermath of a massive
galactic collision.

There are lumps
and clumps of stars,

random groups
at random directions

and random velocities.

It's all mixed up,
which is what we think

galaxies look like after
a massive merger.

ROWE: The merger aftermath
reveals a more

complex series of events
than a two-galaxy collision.

What we find in the center of
this galaxy isn't two,

but three giant black holes,

which suggests that there have
been three galaxies

colliding in recent history.

MINGARELLI: So when
this new galaxy starts to merge

with the galaxy that hosts
the stalled pair,

it brings in its own third
supermassive black hole.

Now this supermassive black
hole perturbs the system,

and it makes what's at
the center highly unstable.

ROWE: The gravity of this third
supermassive black hole steals

orbital energy from
the stalled pair,

pushing them closer together.

It's almost a thief
that comes in and takes away

some of that rotational energy
from this binary

black hole system.

ROWE: As the two
supermassive black holes

lose orbital energy,
they finally come together.

The likeliest thing to happen
is that the least massive

supermassive black hole
is ejected.

And the remaining
two merge very quickly.

ROWE: The high-speed merger will
last just milliseconds,

but it will trigger

[explosion blasts]

A gigantic explosion.

SUTTER: When these giant
black holes merge,

more energy is released in
this process than our entire

galaxy will emit

over the course of billions
of years.

ROWE: Perhaps M87 star merged

with other supermassive
black holes

in the same way...

A third black hole, helping it

to overcome the final
parsec problem.

It's possible that mergers
with other supermassive

black holes allowed M87
to reach its sizable

mass of 6.5 billion
solar masses.

ROWE: Supermassive black holes
meet their match

when they square off against
each other.

The fallout is cataclysmic,

and as we get closer
to M87 star,

our mission becomes
more dangerous.

We enter
the gravitational kill zone

surrounding
the supermassive black hole.

We know the dangers.

Any unwitting stars
that get too close are

stretched, shredded,

and torn apart,

creating one of the biggest

and brightest light shows
in the universe.

ROWE: As we get closer to M87's

supermassive black hole,

we enter dangerous territory,
not just for us,

but also for wandering stars.

If the black hole snares them,

they are toast.

But their death may solve one

of the mysteries of
supermassive black holes...

How fast they spin.

It's difficult
to calculate just how fast

a featureless black object
hidden by

a bright disc rotates.

You need a lot of patience
and a little bit of luck.

Astronomy is sometimes
a pretty opportunistic science.

You have to be looking at
the right place at

the right time to figure out
something new

that we've never seen before.

ROWE: Recently,
astronomers caught a break

when they spotted
an extremely bright flare

in galaxy PGC 043234.

It was hard to miss.

The flare was 100 billion
times brighter than the sun.

And the energy output
was absolutely ridiculous.

If this happened in the center
of our galaxy,

it would have been so bright,
we could see it during

the daytime.

[explosion blasts]

ROWE: A routine search
for supernovas,

violent deaths of giant stars,
detected the intense flash.

ASAS-SN
is this network of telescopes

designed to look for brief,

high-energy events
all around the sky,

and primarily supernova.

They saw a bright flash,
and they thought, "Oh, yay,

another supernova."

If you see a bright flash of
light coming from a galaxy,

that's kind of
your first thought.

But it didn't look like
a supernova at all.

It didn't act like
a supernova flash would.

It didn't have
the right characteristics.

It wasn't behaving
like a typical supernova.

It had to be something else.

SUTTER:
So they send out an alert to

the astronomical community,
saying, "Hey, there's something

cool happening
in this region of space."

Once an event is
flagged as real,

then what happens is other
telescopes turn their attention

to that event.

ROWE: The data revealed
something strange.

SUTTER: After the initial flash,

there are still smaller
flashes that repeat, and if

you're gonna kill
a star in a supernova,

there's nothing left
to repeat like that.

Intriguingly, it flashed on

and off about once
every 130 seconds.

ROWE: The flashes continued
for 450 days.

PLAIT: When astronomers looked
at this galaxy in detail,

they saw that this event
happened right at the center,

and there's a black hole there
with about one million times

the sun's mass, and that was...
That's it, man.

That's the smoking gun.

ROWE: What they observed was
an extremely rare phenomenon,

a tidal disruption event.

SUTTER: Catching one live
as it happens

is an astronomer's dream.

This was our first time
catching a black hole in

the act of feeding on a star.

In galaxy PGC 043234,

a star wandered too close to

a supermassive black hole.

SUTTER: As this unfortunate star
got close to the black hole,

the black hole is spinning,

and the gravity around this
monster black hole is so strong

that it could pull
the star apart.

PLAIT: The side of the star
closer to the black hole

is feeling a much, much stronger

gravitational pull toward
the black hole than

the far side of the star,
because it's farther away.

And what this does is
it stretches the star.

SUTTER: So it got ripped
to shreds, it got shredded.

It got pulled out and stretched

and whipped
around the black hole.

And this stretches the star
into some giant long arm,

and that swirls around and is
trapped as it orbits

the black hole.

ROWE: The accretion disk
snares the shredded star.

OLUSEYI: And what this means is
that that accretion disk is

gonna increase its output of
radiation, in particular,

high-energy radiation.

ROWE: As the star embeds in
the accretion disk,

a massive flare
of radiation erupts,

lighting up the universe.

After this initial burst,

the spinning star debris
sends out

a continuous stream of light.

Our telescopes only
pick up this radiation

on each rotation of the disk.

It's like seeing the beam from
a lighthouse every 130 seconds.

The flashes are the final
pulses of a dying star,

and those flashes
reveal both the width

and the rotation speed of
the supermassive black hole.

We learned that
the central massive black hole

is about 300 times wider
than the Earth,

but it's rotating
every two minutes.

It's rotating at half
the speed of light.

ROWE: That's over 300 million
miles an hour.

We don't yet know how fast
M87 star is spinning,

but we do know the accretion
disk rotates it over

two million miles an hour.

This glowing ring,
hundreds of light-years wide,

now lies directly ahead
of our ship.

It is one of
the most awe-inspiring

and deadly places
in the universe,

and we are heading
straight for it.

ROWE: After our long trek
across the galaxy,

we finally face the mighty

supermassive black hole
at its center... M87 star.

A dazzling glare confronts us.

This is the accretion disk,
a ring of hot gas and dust

spinning at over
two million miles an hour.

M87 star's accretion disk

is so bright,
the Event Horizon Telescope

photographed it from Earth
55 million light-years away.

So I remember
exactly where I was

when that image was released...
I was sitting with a bunch of

my colleagues at
the Center for Astrophysics,

and we were all watching
the press conference live and

just absolutely slack-jawed
when that image hit the screen.

OLUSEYI:
I was sitting in the airport

when I saw
this black hole image,

about to take
a flight to New York.

I got so excited that I actually

walked away from
my backpack sitting there.

TEGMARK: Seeing that picture,

it really doesn't leave room
for doubt.

Black holes are real.

ROWE: The Event Horizon
Telescope photo is

the first picture ever taken
of a black hole.

The image revealed M87 star

spins in a clockwise direction,

and it's 23.6 billion
miles wide.

That's around three million
Earths lined up in a row.

The photo also confirmed
M87 star's

membership in a very
exclusive club...

The 1% of supermassive black
holes that actively feed.

The image from the Event
Horizon Telescope

tells us that M87 is indeed

actively growing and accreting
and eating material

around it... it shows gas
swirling around that black hole

on its way to being swallowed.

ROWE: But do all supermassive
black holes consume material

in the same way that
M87 star does?

Is it possible
that different black holes

have different table manners?

Well, it turns out
that's really true.

Some are more delicate eaters.

ROWE: In 2018, we discovered
a supermassive black hole

250 million light-years from
Earth that eats on a schedule.

Now we have
this case of a black hole

that looks like it's
feeding three times a day.

It's having
three square meals a day.

ROWE: Intense bursts
of energy pulse out

from galaxy GSN 069.

We see X-ray flares and bursts

coming from the center
of this galaxy,

repeating every nine hours,
and each burst is associated

with a new feeding event.

ROWE: This supermassive
black hole not only

eats on a schedule,

it has a very healthy appetite.

Each one of these meals that
this black hole is consuming

is the equivalent of four of
our moons in a single bite.

ROWE: So what exactly
is this supermassive

black hole consuming?

The most likely contender
is a star.

We think that the star has
been ripped apart

and spread throughout
an accretion disk, and then

slowly over the course of hours,

an instability builds up,
and some material falls in.

ROWE: When the infalling
material from

the star hit the supermassive
black hole,

it triggered a burst of X-rays.

Then, the system stabilized...

until it sparked up again,

creating a nine-hour cycle of
bursts of energy.

Then, in 2020 new observations
spawned a different theory.

The star wasn't caught
on the accretion disk.

The supermassive black hole had
instead pulled it into orbit.

Its orbit takes it near that
black hole every nine hours,

and every time it encounters
the black hole,

some of its material
gets sipped off.

ROWE: Eventually,
the GSN 069 supermassive

black hole will lose
its meal ticket.

But it's luckier than many
other supermassive black holes.

Sometimes black holes just
take a little nibble on

the surrounding material
and just give

a little burp of radiation
in response.

ROWE: A black hole burp
generates strong

shockwaves that radiate out
across the universe.

We detected two of these
energy outbursts

in galaxy J1354+1327,

located 800 million
light-years away.

The huge burps suggested that
the supermassive black hole

at the core of this galaxy
was snacking.

It ate a bunch of material
one time

that caused a burst of energy
flowing outward.

Then it feasted again,
and that caused another burp.

ROWE: What caused these
separate outbursts?

The belching black hole galaxy
has a smaller companion galaxy.

A gas stream
links the two galaxies,

supplying an intermittent,
on-off food supply.

There's actually
a smaller satellite

galaxy going around
the bigger galaxy.

The black hole in the middle is

pulling streams of material
off this little galaxy.

ROWE: Clumps of material
from the companion galaxy

move toward the center of J1354.

Once there, the supermassive
black hole grabs them.

Some gas streaming from
the neighboring galaxy

reaches the center of

the bigger galaxy
when the black hole feeds

and then ejects a jet.

ROWE: When supermassive
black holes like the one in

J1354 receive
an irregular supply of food,

a cycle is established,

a routine that scientists
call feast...

burp...

nap.

The supermassive black hole
we're headed towards, M87 star,

doesn't do burp and nap.

It feasts all the time.

Stars come in
and get ripped apart,

maybe once every 10,000
or 100,000 years.

Whereas M87 has been shining
brightly for millions of years.

It clearly has a supply of gas
other than ripped apart stars

that's feeding
the accretion disk.

ROWE:
This helps explain how M87 star

grew to 6.5 billion
solar masses.

But what about the future?

Will this supermassive black
hole continue to feast,

or will it starve?

To find out,
we have to move even closer,

across the accretion disk,
to discover just

how M87 star satisfies
its insatiable appetite.

ROWE: Our ship passes over
the accretion disk of M87 star,

a blazing ring of gas and dust
hundreds of light-years across.

This is the supermassive
black hole's grocery store.

Black holes are known for
sucking in everything.

But is that really true?

Black holes don't really suck.

It's a popular misconception.

They don't just pull
anything in.

In fact, if the sun just
instantly turned

into a black hole today,

the Earth would happily
continue on in its orbit,

because all that gravity
cares about is

how massive and how far away
something is.

ROWE: Supermassive black holes
like M87 star

are a lot more massive than
a regular sun-sized black hole.

This means their gravity is
greater and extends much

farther out into the galaxy,

allowing supermassive black
holes to attract dust,

gas clouds, and stars from
billions of miles away.

But they don't gulp
down everything they pull in.

OLUSEYI: The way black holes
eat matter

isn't as straightforward
as you might imagine.

Earth gains mass every day from

objects falling to it
from space.

So you might imagine that matter

falling onto a black hole is

like meteorites
falling onto Earth.

They can come in from any
direction and land anywhere.

That's not the case around
a supermassive black hole.

The most efficient way for
a black hole to consume matter

is for it to grow
an accretion disk.

ROWE: Accretion disks
grow when gas and dust

dragged in by the supermassive
black hole's

gravity spirals inward
and piles up in a ring.

The ring starts to spin from
the combination of gravity,

and the momentum
of the gas and dust.

The spinning material
flattens into a disc.

The material
doesn't fall straight in.

It orbits its way in,

and so it gets accelerated to
incredibly fast speeds.

Sometimes, the matter ends up
inside the black hole.

Sometimes,
the matter ends up getting

kicked away from the black hole.

ROWE:
As we traveled through M87,

we witnessed jets and winds

from the supermassive black
hole blast this material

out into the galaxy.

But there may be other
things that

stop food from entering
a black hole.

HOPKINS: The black hole
at the center of

our Milky Way galaxy,
what we call

Sagittarius A star, appears to

be swallowing material or eating
at an incredibly low rate.

ROWE: To discover what's
stopping Sagittarius A star,

or Sag A star for short,
from feeding,

scientists studied infrared
light moving out from

the supermassive black hole.

To do that, they needed to fly
high in Earth's atmosphere.

The problem is, water vapor in
our atmosphere prevents

the infrared light from space
from getting down to the ground.

SOFIA is an infrared
telescope built

into the side of an airplane.

As bizarre as that is,
it's a very stable platform.

SOFIA can look at these
objects emitting infrared

in space and get really good
observations of them.

ROWE: SOFIA focuses on
the structure of the gas in

the strong magnetic fields at
the center of the Milky Way.

This high-resolution
telescope can track

the finest grains of dust.

When all the dust grains
in a cloud are aligned by

a magnetic field,

they scatter the light coming
at them in a certain way,

and we call this
polarized light.

The dust grains can actually
map out the magnetic field

embedded in that dust cloud.

ROWE: The telescope picked out

the grains arranged
in a spiral pattern

and revealed the direction
the grains were moving.

This movement reveals why
Sag A star is starving.

The magnetic field is
channeling them into

orbit around the black hole

instead of
allowing them to fall in.

So it's literally keeping
those dust grains

away from the black hole.

ROWE: The magnetic fields also
pushed clouds of gas,

Sag A star's food source,
away from

the supermassive black hole.

This is the situation now,
but that's not necessarily

the way things are
always going to be.

ROWE: Because magnetic fields
can switch directions.

PLAIT: There's a lot of other
junk out there, dust and gas

and other stars,
that as they get close,

they can change the magnetic
field, and that might allow

that dust to fall into
the black hole.

ROWE: Magnetic fields
changing direction

offers hope for Sag A star.

And magnetic fields could help
M87 star feed.

Our mission continues,
following this material

plunging down into
the supermassive black hole,

We set a course towards
the event horizon,

the boundary between the known
and the unknown universe,

where the laws of physics
no longer apply.

ROWE: Our ship crosses
the accretion disk.

Ahead, the absolute darkness of

the supermassive black hole,
M87 star.

According to black hole legend,

this is where we meet our end,
torn to shreds by gravity.

We have so much wonderful
imagery of what would happen if

you were to fall into a black
hole from science fiction.

One idea that has caught
popular attention

is the notion that

you get spaghettified when
you fall into a black hole.

This is me.
This is a black hole,

which is pulling stronger
on my feet than on my head.

And if this black hole is
a little bit heavier

than our sun, this difference

in pull is so strong that
I would actually

get spaghettified, torn apart.

ROWE: So will M87 star
spaghettify us?

The answer depends on
the black hole's mass

and volume ratio.

A stellar mass black hole
with the mass

of 14 suns is just
26 miles across.

That's about the size of
Oklahoma City.

Such an enormous mass
in a small volume

creates a very sharp increase
in gravitational tidal forces

as you approach the black hole.

With a small black hole,

the strength of gravity
changes so rapidly

with distance that your feet
could be pulled

a million times harder
than your head.

But with supermassive black
holes, that doesn't happen.

ROWE: The mass of
a stellar mass black hole

is concentrated in a small area.

A supermassive black hole's
mass spreads much wider over

an area a billion times larger,

so its gravity increases
gently as you get closer.

This means approaching
a supermassive black hole feels

more like walking down a slope

rather than jumping off a cliff,
so it won't rip you to shreds.

Supermassive black holes
have a bad reputation.

That bad reputation firmly
belongs to stellar

mass black holes that rips
things to shreds.

TEGMARK: The nice thing about
supermassive black holes is

these so-called tidal forces
are much weaker,

so I would actually be just
fine and be able to take in

this really bizarre scenery
around the black hole,

with light from distant objects
being bent out of shape.

ROWE: So we can approach
M87 star safely.

Once there, we are faced with
an awe-inspiring sight.

The supermassive black hole
distorts the light around it.

Far away from the black hole,

that warping isn't very
strong, but the closer

the light gets
to the black hole,

the more severely its path is
distorted, and the starlight

around the black hole
becomes really bizarre.

They get stretched into...
Into rings and arcs.

ROWE: We can even see
things hidden behind

the supermassive black hole.

I would see, for example,
the galaxy behind here looking

completely warped out of shape,

because light is bent
around the black hole.

Black holes can even bend
light so it comes from my face,

goes around and comes back
on the other side.

So I could, in principle,
use a black hole,

you know, as a mirror
when shaving.

SUTTER: To really understand

what's happening
around a black hole,

we need to understand gravity,
and the language of gravity is

the language of spacetime.

ROWE: Spacetime binds
the whole universe together.

If we could put on special
spacetime glasses,

we'd see stars,

planets, and galaxies floating
on a grid of spacetime.

These objects have mass,

and mass distorts
and curves spacetime.

Imagine a trapeze artist with
a flat net underneath them.

When they fall from
the trapeze onto that net,

the net distorts.
It forms a dimple

right where that trapeze
artist is.

The trapeze artist
is like a black hole.

The net is like
the fabric of space

and time distorting
because of the mass in it.

ROWE: This distortion
of the spacetime net

by objects with mass is
called gravity.

The more massive you are,

the more gravity
you have, because

the more you bend
and stretch spacetime.

So one trapeze artists may
bend the net a little bit,

but a hundred trapeze artists

will bend that net a lot,
and good luck

trying to walk across it.

ROWE: M87 star's

immense gravity bends space,
forcing light

to travel along the curves.

But what does it do to
the other half of the equation,

time?

Einstein realized that time
actually runs slower

near a black hole
than back on Earth.

ROWE: It's a process called
gravitational time dilation.

Viewed from a distance, our ship

appears to move in slow motion.

But what do we see on board
the craft

as we approach M87 star?

You would perceive
time to proceed on normally.

You'd look at your watch,
and that second hand

would be going around
the dial just like normal.

But to an outside observer,

that apparent one minute on
your watch could take millions

to even billions of years.

If I'm having a Zoom
conversation with mommy

back home,
even though I'm feeling

I'm speaking normally,
she would hear me go,

[exaggeratedly slowly]
Hi, mommy.

[normally] And this is not
some sort of illusion.

My time really is going slower.

So when I come home, she'd be
like, "Hey, Max, you look"

so good, you look so youthful,"
and I would actually

have aged less, because time
ran slower over there.

ROWE: On our final approach
into M87 star,

we reach a crucial milestone.

We are now at the innermost
stable orbit.

We go any further,
we're not getting out ever.

You have two choices.

You either escape to safety
or you fall into the black hole.

ROWE: Well, that's easy.

We detach the probe to
approach the black hole alone.

You can think of the event
horizon as being the surface of

a black hole, but that's
a little bit of a misconception.

There's not actually
anything there.

That's just the distance
from the center,

where the escape velocity is
the speed of light.

ROWE: Because nothing
can travel faster than light,

nothing can escape a black hole.

Think of the event horizon
as a waterfall.

OLUSEYI: If you imagine the flow
of water over a waterfall,

if you're a fish, you could swim

up close to that edge
and still escape.

But if you go too far,

you hit the point of no return,
and you're going over.

ROWE: At the event horizon,

the water moves faster than
the fish can swim

or our probe can orbit,

so the waterfall, or gravity,
carries them over

and into the black hole.

But what about the light
around them?

Imagine that fish
that's going over

the waterfall is carrying
a flashlight.

Say it's an alien fish.

At a black hole,

If that fish goes over that
event horizon, not only does

the fish and the flashlight
get sucked in,

but the light of
the flashlight get sucked in.

TREMBLAY: There's nothing
that can turn around.

Light, matter, cows,
elephants that passes through

the event horizon
can never come back out.

It is a one-way ticket.

ROWE: A one-way ticket through
the event horizon.

Back on the ship, though,
we don't

see the probe entered
the supermassive black hole.

Instead, from our perspective,

the probe just gets slower and
slower and slower and slower.

ROWE: Until it appears
that time simply stops

for the probe,

frozen by the enormous gravity
of M87 star.

The probe appears stuck,
glued to the surface.

But that's just our perspective.

In reality, the probe
has already crossed

the event horizon
and is inside the black hole.

ROWE: If only it was
that simple.

The two major theories that
explain how the universe works

don't work at the event horizon.

General relativity says
the probe enters

the black hole,

but quantum mechanics throws
up some major hurdles.

According to some ideas rooted
in quantum mechanics,

there may be something
called a firewall,

a wall of quantum energies
that prevents material from

actually reaching through
the event horizon.

ROWE:
The question of what happens

to anything attempting to cross

the event horizon has
challenged some of the greatest

minds in physics.

Will our probe enter
the supermassive black hole,

or will it be burnt
to a crisp in a wall of fire?

Our probe is approaching
the event horizon of M87 star,

but there's a problem.

The two major theories that
explain how the universe works

don't agree
about what happens next.

One says the probe passes
through unscathed.

The other theory says
that's impossible.

It suggests the probe hits

an impenetrable barrier
called a firewall.

How can the same event have
two different outcomes?

There's a really interesting
puzzle right now, which is

where general relativity
and quantum mechanics meet,

and it's called the Black Hole
Information Paradox.

What we have is a very
schizophrenic situation

in physics, where we have

two theories
that just don't get along.

Einstein's theory of gravity
explains all the big stuff.

Quantum field theory explains
all the small stuff.

So which one is right
and which one is wrong?

This is the mystery.

ROWE: General relativity says,

in theory, crossing the event
horizon is no big deal.

If you're passing through
the event horizon,

you wouldn't notice
anything different.

MINGARELLI: You can, in fact,
cross the event horizon

of a black hole like M87 star
in your spaceship,

without even knowing that you
have, nothing would change,

you'd just peacefully
drift inside.

ROWE: According to general
relativity, our probe crosses

the event horizon and enters
the black hole.

Quantum mechanics sees
it differently.

When it looks at the probe,

it doesn't see
a robotic spacecraft.

It sees information.

THALLER: Everything at
a quantum mechanical level

has information.

You can think of things like
a particle having a charge.

Particles have spin, angular
momentum, and that information,

as far as we understand,
can't be destroyed.

ROWE:
What do we mean by destroyed?

Well, think of burning a book.

The words are information.

As each page burns,
the words disappear.

The information is gone,
but not really.

If you could track
every single thing that

was happening,
track each smoke particle,

put everything
back together again,

in principle, that information
is still there.

ROWE: Because information
can't be destroyed,

the probe's information,
even if mangled,

should be inside
the supermassive black hole.

If the information that fell
into a black hole just stayed

locked inside of a black hole,
that'd be fine.

That doesn't violate
any physics.

ROWE: But Stephen Hawking
threw a wrench in the works

when he theorized
that, over time,

black holes evaporate, slowly
shrinking particle by particle,

emitting heat known as
Hawking radiation.

Hawking radiation itself
doesn't carry any

information out,
and Hawking radiation

eventually destroys
a black hole.

Eventually, the black hole
evaporates and disappears.

ROWE: As the black hole
vanishes, so too,

does information
about the probe.

This is a big problem for
quantum mechanics.

Can black holes really

destroy information even though

quantum physics suggests
you cannot?

So is the foundation of
quantum mechanics wrong?

This is the Quantum
Information Paradox.

ROWE: To try to prevent
this impossible situation,

scientists came up
with a workaround,

something that prevents
the probe's information

from ever entering
the black hole,

the firewall.

Quantum mechanics
says that there is this

quantum fuzz causing there to be

ridiculously high temperatures
literally burning

you up as soon as you enter.

ROWE: If the firewall
incinerates the probe,

then its information will
stay in the ashes of the ship,

just like the words from
the burning book.

So which theory is right?

Does the probe safely
enter the black hole?

Or does the probe burn up?

I've actually spent
an afternoon at Caltech arguing

with people
about whether anything

falls into a black hole or not,

and the answer is
we don't really know.

ROWE: To find an answer,

scientists have come up
with some crazy ideas.

One, called
quantum entanglement,

suggests that
the probe is both inside

and outside the black hole,

its information carried by
particles constantly popping up

on either side
of the event horizon.

And Stephen Hawking,

whose original idea that black
holes lose information through

heat, also came up with
a solution.

He suggested that black holes
have soft hair.

Traditional black hole science
says they're bald.

By which we mean that they have

no features
at all except their mass,

and their charge and their spin
that you can measure

from outside.

ROWE: Hawking's updated theory
says that black hole hair

is made from ghostly
quantum particles,

which store information.

Thermal radiation from
the evaporating black hole

carries this information away
from the event horizon.

If Hawking is right,

the probe's information will
eventually escape

into the universe.

The concept of black hole hair

would solve the Black Hole
Information Paradox

if it exists,
but we don't know if

black holes have hair
or if they're, you know, bald.

ROWE: Until we can unite
quantum mechanics

and general relativity at
the event horizon,

the Information Paradox will

remain a problem for physicists.

It's one of the most
embarrassing problems

in physics,
which is still unsolved.

I hope one of you
who watches this

will become a physicist
and solve it for us,

because physics
is far from done.

ROWE: The failure to solve
the Black Hole

Information Paradox
throws up a major obstacle

to our understanding of how
our universe works.

This is the point
where physics hits a wall.

While a search for
a solution continues,

let's assume our probe dodges

its way past
the Information Paradox.

It sails across the event
horizon towards one of the most

violent places in the universe,

the core of M87 star.

It's called the singularity,

and there are no rules.

Nothing makes sense,

and nothing escapes.

ROWE: Our probe has
crossed the event horizon.

It's on a one-way trip to

the heart of the supermassive
black hole M87 star.

OLUSEYI: Anything that crosses
the event horizon

is not coming out...
It's like Vegas.

What goes in a black hole
stays in a black hole.

ROWE: The probe leaves
the physics we understand

and enters the world
of physics we do not.

This probe is now moving
faster than light

or being carried by space
itself faster than light.

Once you cross the event
horizon of a black hole,

your future lies on
the singularity in the center of

the black hole... there's
no escaping the fact that

you will eventually join
the singularity.

OLUSEYI: The space inside
of a black hole

is like a 3D spinning vortex.

The space in there is
always moving.

This is the nightmare version
of the carousel ride.

ROWE: The whirling probe hurtles
downwards, until it hits

an even more bizarre region of
the black hole...

the inner event horizon.

You thought the firewall
was bad,

but that's peanuts compared to
the inner event horizon.

Theoretical physicist Andrew
Hamilton believes that all

light and matter that's fallen

into a black hole piles up in
a tremendous collision at

this location.

The inner event horizon would
be infinitely violent,

because it's like the meeting
point between two universes.

ROWE: This meeting point is
like water falling and smashing

into spray, shooting back up

from the rocks
at the base of the falls.

Inside the supermassive
black hole,

space races in and crashes
into rebounding space at

the inner event horizon.

SUTTER: This would be a place
of infinite energy.

It's a place where infalling
material, into the black hole,

meets outflowing material.

ROWE: Everything falling into
M87 star smashes together in

a monumental release of energy.

This energy has got to
go somewhere.

It's possible that this inner
event horizon is so energetic

that brand-new universes could
be born in this space.

But the question is, how do
you actually sort of birth

a new baby universe?

ROWE: The energy created at
the inner

event horizon could compress
down into

one tiny speck,
which suddenly ignites,

[explosion blasts]

Sparking baby universes
into life

in their very own Big Bangs.

We know that, a long time ago,
our own universe was very small,

very hot, and very dense.

It's possible that it could
have been born in

the inner event horizon of
a spinning black hole.

This is such a tantalizing

and very hypothetical idea,

but if it's correct,

it gives us insights
into the origins

of our universe itself.

Do we have strong evidence

that black holes
create baby universes? No.

Do we have strong evidence
that they don't? No.

ROWE: If the probe survives
the inner event horizon,

it then heads towards the
strangest place in the universe,

the core of
a supermassive black hole.

The singularity.

As the probe gets closer
and closer to the singularity,

the probe gets further
and further away from

known physics.

We don't know what the probe

will encounter when it reaches
the singularity.

We don't know what it will find.

We don't know what it
will experience.

We don't know.

ROWE: In other words,
there's a lot we don't know.

Like what exactly is
the singularity?

It's a hard question to answer.

Traditional science says
it's an infinitely tiny point,

but that's not the case
with M87 star.

What's interesting is that if
your black hole is spinning,

the singularity is not a point,
but it's, in fact, a ring.

ROWE:
Physics says the singularity

is infinitely dense.

A point of space
and time that is...

It's collapsed
as far as it will go,

it basically has infinite
density in zero size.

ROWE: For many scientists,
that's a big problem.

I do not like singularities.

I feel that they sound
really un-physical.

The word singularity sounds
so intimidating and scientific,

but it's honestly just
our physicists' code word for,

"Uhh, we have no clue
what we're talking about."

OLUSEYI: Where else in nature
do we find infinities?

We're talking about a region

that would have
infinite density and

infinitely small volume,
basically zero volume.

How could that exist?
I just don't see it.

We just don't know.

And frankly, we will
never know for sure.

ROWE: Perhaps the probe
breaks up and joins material

consumed by M87 star over
billions of years.

Compressed down, not just to
atoms, but to a sea of energy,

absorbed into a ring of zero
volume and infinite density.

Or there could be
another possibility.

Maybe the singularity doesn't
destroy the probe at all.

Maybe the probe travels
straight on through

and passes into
another universe.

ROWE: Our voyage to
the heart of M87 star

has been a wild ride.

We crossed the event horizon
and fell towards

the singularity,

the core of the supermassive
black hole.

Is this the end of our journey
or just the beginning?

It could be that
the singularity isn't

the end point
of the probe's journey.

It could be that the probe
passes through

the singularity and enters
into a new universe.

ROWE:
Our probe has another option,

an escape route out of M87 star.

In our universe,
we have black holes,

objects where, if you enter,
you can't escape.

It's also theoretically
possible for there to be

white holes,

objects that you can't enter,
you can only escape from.

A white hole is basically
a black hole running backwards.

ROWE: Some physicists have
theorized that white holes

may link to the singularities
of black holes,

connected by something
called a wormhole.

TEGMARK: There have been
interesting papers written

suggesting that you could have
a wormhole where

something that falls into
a black hole here comes out of

a white hole somewhere else.

ROWE: It sounds like a great way

for the probe to escape
certain death, theoretically.

A wormhole is the bridge

in spacetime between
those two things.

It's easy to create
in mathematics.

It very well might not exist
in real life and will almost

certainly live out
on our entire civilization

and never know about it.

ROWE: That's because
constructing a bridge

between a black hole
and a white hole

creates a few issues.

A, we don't know how to
build them for sure.

B, they might be unstable
and collapse on

themselves immediately,
unless you invent...

Have some new,
weird sort of matter that

can support them.

OLUSEYI: The problem is that

it's hard
to maintain this bridge open.

It's not likely
that they would ever have

any practical use because
they're just not stable.

ROWE: But if M87 star does have
a stable wormhole linked to

its singularity,
where might our probe end up?

It could be that this probe's
journey doesn't end at

the singularity,

and all the information that
it carries with it could be

deposited in some distant
corner of our own universe.

ROWE: Or perhaps
in a different universe.

One idea that
sounded like science fiction

decades ago is actually now
considered potential reality,

and that's the idea of
parallel universes.

If parallel universes exist,

then some surmise that
a black hole could be a gateway

to a parallel universe.

ROWE: If there are
parallel universes,

who knows which one our probe
may end up in.

This universe may be
just like our own, or

it might be something
completely different.

We'll never get to find out
unless we follow in after it.

It could all work out just fine,

and that probe
just sails on through

and gets to explore
new adventures.

We don't know.
Only the probe knows.

ROWE: Supermassive black holes
are some of

the strangest and most
fascinating objects in

the universe.

Ever since Einstein's
Theory of Relativity

predicted black holes
a century ago,

we've been trying to
understand how they work.

The photograph of M87 star
confirmed many theories,

but there is still much to
learn about the birth,

life, and death of
these remarkable objects,

and even more
to leave us fascinated.

This is the ultimate unknown.

This is the real Wild West.

This is the frontier of
human knowledge.

MINGARELLI: I care about
supermassive black holes

first and foremost
because they are awesome.

They stimulate my childhood

imagination and fascination.

HOPKINS: Supermassive
black holes offer us

a truly unique window into
how the laws of physics work,

especially the laws of gravity
in extreme regimes far beyond

anything that we can
possibly imagine here on Earth.

THALLER: Supermassive
black holes lurk at the heart of

almost every large galaxy
that we know of.

So in some way,
we're just sort of

all along for the ride with
the supermassive black holes.

If I could make a request
for one special favor

I would get before I die,

what I would like to do
is to get to just spend a few

hours orbiting the monster
black hole in the middle of

the galaxy... what a way to go.