All language subtitles for How.the.Universe.Works.S11E03.Most.Violent.Event.in.the.Universe.1080p.AMZN.WEB-DL.DDP2.0.H.264-BurCyg_track3_[eng].1

You might have seen
a boxing match on TV.

Maybe you've even seen one live.
But you have never seen

a contest like this.

Take your ringside seat
to the fight of the cosmos.

This is gonna be a wonderful fight
to witness,

but you ought to be a few million,
billion light years away.

It's like being punched
by the ghost of Muhammad Ali.

You don't even see it coming.

Our fighters don't float like
a butterfly or sting like a bee.

But they can deliver
the ultimate knockout blow.

It is a soul-chilling,

mind-crushing amount of energy.
It's just unbelievable.

It's a fight between two
supermassive black holes.

Forget about the World
Heavyweight Championships,

this is the universe's
heavyweight championships.

Get ready for the heavyweight
championship of the universe.

2021. Scientists detect

a gigantic rumble deep in space.

A tsunami of gravitational waves.

Giant ripples racing
across the universe.

Gravitational waves that big
have to come from

a giant, cataclysmic event.

The universe is immense

and full of very violent events

that are happening
every single day.

The universe is a scary place.

There is violence
everywhere we look.

The growls and roars are clues

about the ultimate cosmic brawl.

The most violent event
in the universe.

But we don't know where
they're coming from.

Imagine a storm is coming
in the middle of the night.

You can't see the storm,
you can't see the lightning,

but you can hear that rumble
of the distant thunder

and you know that it's coming.

This distant rumble of
gravitational waves

is like the footwork
of heavyweights

pounding the canvas
of the boxing ring.

The waves are caused by
something massive

throwing its weight around.

It's not the first time
we've detected gravitational waves.

Our experiments have picked up
the signal

of two small stellar mass
black holes colliding.

These waves are high-pitched

and ring like a boxing bell.

The deep space growl
is a much lower frequency.

Like the roar of a crowd.

The difference in frequencies
would be even more exaggerated

than the difference between
a sparrow chirping

and the sound coming from
a blue whale underwater.

It would be orders of magnitude
more different than that.

The low frequency
of the deep-space rumble

tells us that the waves
are colossal.

Imagine throwing a stone
in the water

and watching the little ripples
come out.

Now imagine throwing in a boulder
a billion times more massive

and watching the huge waves
that come from that.

Those are the waves
that we're looking at.

These are more difficult to detect

because the waves are so big.

One of their wavelengths
is about 15 light years.

You could wait for 15 years

and only have one wavelength
go by the Earth.

The waves are too big for an
Earth-bound detector to pick up.

So, to search for the source
of these giant waves

Chiara Mingarelli and her team

use a detector already in space.

Something large enough to pick up
these galactic heavyweights.

Spinning dead stars called pulsars.

Our galaxy is awash with pulsars.

Now they're called pulsars because
they pulsate very regularly.

They're like cosmic lighthouses.

The lighthouse beams are so regular
you can set your watch by them.

But when a huge gravitational wave
hits them,

the timing
gets knocked out of whack.

That pulsar's gonna basically
rock back and forth,

and that's going to change
the timing of the pulses

that we measure from that object.

To identify the source
of the gravitational waves,

Chiara and her team
measure the wobbles

of 100 pulsars spread across
light years of space.

It's like a tsunami.

And the pulsars are like the buoys
on the surface of the ocean.

And as the tsunami passes by,

we can watch all of them moving
and shifting up and down.

So our pulsar timing array

is a gravitational wave
warning system.

The pulsar array has identified
the source of the tsunami

of gravitational waves.

The only thing we know of that can
makes these very long wavelength,

very low-pitch gravitational waves

would be the collisions
of supermassive black holes.

They're massive. They're huge.

And they know how to throw
their weight around.

Supermassive black hole binaries

produce the loudest
gravitational waves in the universe.

The gravitational waves' signal

revealed something extraordinary.

It's not just gravitational waves

coming from one black hole
binary pair,

it's actually from
the cosmic population

of supermassive
black hole binaries.

Chiara and her team think there
may be tens of thousands

of heavyweight bouts going on.

Now, the scientists want to
pick out the sound

of one single collision

between two supermassive
black holes

from the background roar.

If we were to hear
a supermassive black hole merger,

it would wound like
a very low-frequency growl,

this... whoooooooo

that would last
about 25 million years.

To date, we haven't witnessed
two supermassive black holes

trading blows in real time.

But we have seen events leading up
to the championship bout.

We've watched galaxies merge.
We've seen stars explode.

We've seen so many violent events
in the universe.

But we haven't seen this one.

It's odd if you think about it.

We haven't seen the biggest one.

We haven't seen mergers between
supermassive black holes.

But that may be about to change.

Chiara predicts
there are 112 fighters

who are pumped up
and ready to enter the ring.

In the next five years,
we should be able to detect

at least one supermassive
black hole merger.

It'll be the most violent event
in the cosmos.

Let's put that in context.

We talk about how supernova
are some of the most

explosive, energetic things
in our universe.

Well, colliding supermassive
black holes

are a billion billion billion
billion times more energetic

than a supernova.

Think about all of the light

being emitted by everything
in the universe,

every star, every galaxy.

In one instant, two supermassive
black holes colliding

could release 100 million times
that energy.

Imagine being punched in the face

by the biggest, baddest
heavyweight of all time.

Ouch.
This is way bigger than that.

Where does all this energy
come from?

Surprisingly, it originates

in the smallest atoms
in the cosmos

in a story that dates back
billions of years,

all the way to the birth
of the universe.

2020. The earthbound
gravitational wave detector, LIGO,

picks up the distinctive signal

of a stellar mass black hole merger.

What we saw was a black hole

of 85 times the mass of our sun

and another black hole of 66 times
the mass of our sun

smashing together
to create a combined black hole.

As someone who studies
black hole mergers,

this was a really exciting event.

We're talking about the largest,
the heaviest,

the most massive black holes
we have seen collide to date.

It may be the largest detection,
but on a universal scale

it's still a small fry.

Like lightweight boxers, the two
black holes circle each other

and emit low-energy
gravitational waves.

This energy loss causes
the black holes

to spiral in together.

Finally, they collide
in a cosmos-shattering event...

...forming a single black hole

and releasing a huge blast
of gravitational waves.

But when astronomers examine
the single merged black hole,

something doesn't add up.

If you take the combined mass
of the two black holes,

you get to 150 times
the mass of our sun.

But actually,
the black hole that's left

only has a mass of 142 times
the mass of our sun.

So the mass you have
before the event

does not equal the mass you have
after the event.

What happened to that missing
eight solar masses?

The way these black hole mergers
work

is very roughly five percent
of the total mass of the system

gets converted into energy.

It all comes down to E=mc2.

This is that beautiful equation
that Einstein told us, E=mc2.

E is the energy, and M is the mass.

Einstein taught us that
mass and energy are related.

In fact, much of what we call mass
is actually energy.

In this case, the violence
of the collision

transforms 18,000 trillion trillion
tons of matter

into an explosion
of gravitational waves.

In just a fraction of a second,

eight suns-worth of matter

is converted into pure,
unadulterated energy.

The amount of energy released
was so great

that if you add up all the energy
of all the stars

burning in the universe,
it was bigger than that.

This event was a collision
between relative lightweights.

Two stellar mass black holes.

To understand heavyweight bouts,
we need to scale up

to supermassive black holes.

In the universe of sports,

supermassive black holes are
the heavyweight contenders.

With these big black holes, size
matters. The bigger the better.

More mass means more energy,
which means more destructive power.

We don't need to look too far
to find this devastating muscle.

This is M87 star,

one of the largest supermassive
black holes

in our cosmic zip code.

M87 star is huge.

It weighs about six billion
solar masses,

about six billion suns, and
it's the size of our solar system.

A collision between two six billion
solar mass supermassive black holes

would release around five times ten
to the power of 56 joules.

So, what does that mean
in real-world terms?

It's hard to use words

to express how much energy
this is

and the numbers are so huge,
they're almost meaningless.

The only way I can really explain
this is... argh!

In physics, we have these
comparisons

so we can get a mental picture,

but for something like this
there is no mental picture.

That is so big!

So where does this destructive
mass and energy come from?

It starts with
the simplest ingredient, hydrogen.

Hydrogen is the basic
building block of the universe.

Each atom is tiny,
but it contains a lot of energy.

Hydrogen atoms contain
a huge amount of energy,

just like all matter does.

And if it's unlocked
in a certain way,

there can be huge explosions.

You take the mass contained
simply in my hand

and you could blow up
pretty much the entire Earth.

Matter has energy
because it formed from energy

in the early moments
of the universe.

In many ways, atoms are reservoirs

of stored energy
from the big bang.

13.8 billion years ago,

the universe ignites

in a super-hot ball
of intense energy.

Right after the big bang, there's
a tremendous amount of energy.

So much energy, in fact,
that normal atoms can't exist.

As that early energy
starts to cool,

it can start to form
primitive matter.

The universe takes that first matter
and energy

in the form of hydrogen atoms

and starts the process of creating
a supermassive black hole.

Step one, build giant stars.

So, gravity brings together

gas, dust, hydrogen,
all of that stuff,

and as the clouds become
more dense,

they attract even more material.

As they spin, they get
hotter and hotter.

And as that temperature
and pressure increase,

finally it ignites nuclear fusion
within the core

and creates an actual star.

These huge stars are like
cosmic rock stars.

They live fast and die young.

When they die, they flame out
in a huge explosion.

A supernova.

The entire star turns itself
inside out

and releases a shockwave,

going a good fraction
of the speed of light,

and releases enough energy
to just obliterate you.

If the dying star is more than
15 stellar masses,

its core collapses
into a black hole.

It's kind of astounding
what the universe is doing.

It's taking incredibly simple things
like hydrogen atoms and using gravity

to ultimately bring
all this stuff together

and make things like black holes.

I find it quite beautiful how
our whole cosmic history

is the story of

little things coming together
into bigger things.

But these stellar mass black holes
are tiny flyweights.

To step up to
the heavyweight division,

they have to grow billions of times
more massive.

But how?

How do black holes become
supermassive?

This is the age-old question.
We're not really sure.

The current stated understanding

of how black holes
become supermassive is like... uh,

we're confused,
we really don't know.

In June of 2018,

we spotted a clue.

An enormous flash of light.

AT2018cow,

nicknamed "The Cow",

was the brightest explosion
ever recorded.

A huge amount of energy
was released

and then, all of a sudden,
everything was gone.

This explosion was
incredibly violent.

At first, it was thought to just be
a supernova, a flash of light.

But over time, it became clear
that this was something

much more powerful.

It was too bright, basically,
to be a supernova.

It was extremely bright
and it didn't fit into

any of our theoretical
understandings

of how bright supernovas
should be.

One explanation is that
the light may have come from

a black hole feeding on a small,
white dwarf star,

weighing less than the Sun.

What really seemed to fit
that model

was a star getting too close
to a black hole

and getting ripped apart,

and then everything going
right down the black hole.

A black hole gains mass
every time it eats something.

That's how they grow. Whether
it's a gas cloud or a star

or another black hole,

once it gains that mass
it's gained that mass.

People often ask me,
What happens to the mass

that falls into a black hole?
Does it go to another dimension?

And the answer is no.

It's still there.
It's inside the black hole.

They get bigger. They grow.

Could this be how weak,
flyweight black holes

turn into mean and powerful
supermassive heavyweights?

The star is like protein,

and the black hole is like
a boxer.

And so, the more protein they get,
the more stars they consume,

the stronger they get,
the more destructive they can be.

But there's a problem with
the training program explanation.

Eating small stars one at a time

just doesn't add enough mass
fast enough

to grow the supermassive black holes
that we see today.

That's like boxers eating
just one egg per day.

Like them, black holes
need much bigger meals.

And in 2020, we detected one.

A sudden burst of
gravitational waves

from a black hole
gorging on the remains

of a dead star...

...called a neutron star.

For scientists, January 2020
was exciting

because it was the first time
LIGO observed

the very first black hole
neutron star merger.

Neutron stars may be small

but they are inconceivably dense.

You want to talk about an enormous
mass, talk about a neutron star.

That's one heck of a snack.

The black hole swallowed
the neutron star in one gulp.

So, this black hole
ate a whole neutron star,

which means it gained just over ten
percent of its entire body weight

in one shot.

Ten percent
doesn't sound like a lot,

but then we detected
another black hole

swallowing a neutron star
just ten days later,

suggesting that there are lots
of black holes

bulking up across the universe.

But even with this extreme
weight gain,

it's probably not enough
to get supermassive.

They need to eat even more.

If you're a black hole
and you want to get bigger,

your best bet is to merge
with another black hole.

But there's a catch.

So,
if you're a flyweight black hole,

and you try to eat

all of the other flyweight
black holes,

there's just not enough time
in the history of the universe

for you to become
a supermassive black hole.

But you can make it
to middleweight.

So, exactly how supermassive
black holes grow so large

remains an open question.

We do know that the process started
in the very early universe

with a journey
from the lightest element

to the most intimidating object
in the cosmos.

It's so interesting
how the cosmos can take something

as simple as a hydrogen atom

and build stellar-mass black holes

and intermediate-mass black holes

and even supermassive black holes

out of these really densely
compressed hydrogen atoms.

It's really a wonder.

Now, 13.8 billion years
after the big bang,

supermassive black holes
feed and flex their muscles

ready to fight for the heavyweight
championship of the universe.

These supermassive black holes

have been bulking up
since the age of the universe.

These black holes have been
getting ready for the fight.

They have been bulking up, they
have been eating entire stars

as snacks,
to get the mass they need.

So they are ready to rumble.

It's not The Rumble in the Jungle.

This is the battle
to be the boss of the cosmos.

Supermassive black hole
versus supermassive black hole.

Fought in the grandest arena.

The fighters' entourage,
their host galaxies,

escort them to the ring.

But even this journey is violent,
triggering starbursts,

jets, and carnage.

Things are about to get nasty.

Galaxies can look calm and serene,

but they can get into
pretty big scraps.

There's a lot of them that are
totally messed up,

and are clearly merging
with each other.

Eventually, even our own galaxy
will merge with another galaxy.

In a few billion years,

a timescale that I'm not
too worried about myself,

the Milky Way and
the Andromeda Galaxy will collide.

The Milky Way and Andromeda each
have supermassive black holes.

And when they collide,

their supermassive black holes
will collide too.

This is an incredibly dangerous
event for our solar system.

Our solar system could be
swept out

to be somewhere else
in this newly-formed galaxy,

or it could be completely ejected
from the galaxy.

If there's any life around
near the merger

of these supermassive black holes,
it would be obliterated.

When galaxies fight, their gravity
pulls on each other,

twisting and distorting
their structures.

The galaxy will be warped
and morphed into

different ways
that we can only imagine

how twisted it would be.

This violent cosmic tango

brings the two supermassive
black holes together.

It's elegant. It's beautiful.
It's this billion-year

choreographed dance that is entirely
conducted by gravity.

The two heavyweight fighters
approach each other.

Their feet beat out a rhythm
on the canvas,

just like circling black holes

release low-energy
gravitational waves.

You have these giant beasts

that are stalking
around each other

and as they do, they create
these gravitational waves.

June, 2021.

Astronomers photograph
a galactic collision

and witness a spectacular
pre-fight fireworks show.

One of the amazing things that can
happen when galaxies collide is

they can create tremendous
starbursts.

There is a big in-rush as all of
that gas follows that gravity.

As the gas gets hotter and denser,
it creates shockwaves.

And each shockwave actually creates
a new generation of stars

going out around the core
of the galaxy.

The sudden starburst lights up
the merging galaxies.

The in-rushing gas also fuels
the prize-fighters,

the supermassive black holes

spiraling towards
the merging galactic center.

But only if the galaxies approach
at the right angle.

It's not the case that every merger
feeds a black hole.

Sometimes it actually
strips material

away from the central regions

and then there's no food there
for the black holes to eat.

A head-on collision
with another black hole

could strip the material
around the supermassive black hole.

With nothing there,

the black holes can't power
themselves.

To get the biggest bang
requires an attacking angle

that'll help feed
a starving black hole.

With a grazing collision,

the gas pockets surrounding
the black hole survive

and gain more mass.

And that can power it even more.

It can make it
even more spectacular.

If there's a big
supermassive black hole,

that suddenly finds it
surrounded by loads of gas

and other material it can eat,

it goes on
a kind of feeding frenzy.

If you're a hungry
supermassive black hole,

then this is your lunchtime buffet.

Not all the gas falls into
the supermassive black hole.

Other parts of the matter actually
gets caught up in what we call

an "accretion disk" rotating around
the outside of the black hole.

This bright vortex spins around
the supermassive black hole

at over two million miles an hour.

The material in the disk
rubs against itself,

creating friction.

Friction generates heat.
If I rub my hands together,

they get a little bit warm.

If I rub my hands together

at hundreds of thousands of miles
per hour,

it's gonna get
very, very, very warm.

The accretion disk keeps up
blasting out intense light.

In 2020,
NASA's Hubble Space Telescope

saw two fueled-up
supermassive black holes

lighting up for the fight.

We call them quasars.

Quasars are a sub-class of
very bright black holes

that are emitting
huge amounts of power.

So these can be seen at
the far reaches of the universe.

Black holes, these so-called
dark things,

when they're growing
at a very high rate,

are some of the brightest lights
in the universe.

To date, we've detected
over 100 pairs of quasars

in the cores of merging galaxies.

We think they will all
eventually collide.

But before they do, they'll put on

a spectacular and lethal
light show...

A common theme in science fiction

are different kinds of jets
of energy or beams

that people shoot out of their eyes
or their hands.

Well, supermassive black holes
do that, too.

...firing out relativistic jets.

When those jets fire up,

that's when you're talking about
superstar.

Really, really bright lights.

And at this point, the galaxy
is lit up and ready to go.

These are the spotlights on
Madison Square Garden.

This is telling you that the event
is going down.

A single
supermassive black hole jet

will produce more energy
in a second

than the sun will produce in its
entire ten-billion-year lifetime.

Imagine a laser of radiation

that is light years in length
and across.

That's what we're talking about.
This thing would fry a planet.

This is no pre-fight hype.

In February, 2020
we saw the impact of a jet.

So in the Ophiuchus galaxy cluster,

there's an enormous void

that is 15 times wider
than the Milky Way galaxy.

And this has all been sculpted,
carved

by jets
from a supermassive black hole.

It's like this scar
on the universe.

It's a million light years across.
It's huge.

Scientists calculate the impact
of the jet hitting the cluster

was equivalent to a 20 billion
billion megaton TNT explosion

every thousandth of a second

for 240 million years.

But how does a black hole generate
so much power?

Even though
there's a lot of energy

in the accretion disk
surrounding a black hole,

there's not enough to launch
these really powerful jets.

Because we can't account for it
any other way,

there must be something else

that's contributing energy
to these jets.

We get a clue in 2021

when scientists publish
a new photo

of the supermassive black hole
M87 star.

It shows the accretion disk.

The lines represent
magnetic field lines.

The fast-spinning accretion disk
drags the magnetic field

around the supermassive black hole,

charging it up for the battle.

The accretion disk
around a black hole

isn't just swirling around
like crazy.

It's also undulating and moving
and wiggling,

and this causes the magnetic field
to fold in on itself.

And every time it folds,
it amplifies itself,

getting stronger and stronger
and stronger.

This is a dynamo that powers
this incredible magnetic field.

The magnetic field can't hold onto
the building energy any longer.

It erupts.

These magnetic field lines
then sweep up and away

like a tornado.
And that can lift material

away from the black hole
and the accretion disk

and shoot it out into
intergalactic space.

The relativistic jet's
immense power

may be a showstopper, but when
it's time to land the killer punch

supermassive black holes

draw on an even more
powerful force, gravity.

Jets are very powerful, but really
only on a relatively small scale.

When you're talking about
cosmic scale,

gravity always wins.

Nothing is as powerful as gravity.

Across the universe, supermassive
black holes duke it out

in the cosmos' version of
heavyweight superfights.

Supermassive black holes are
merging around us all the time.

It's only our ability
to detect them

that's preventing us
from seeing them.

Scientists have identified
at least a dozen pairs

of supermassive black holes
circling each other.

We have some hints
of some galaxies

where we think it might happen,

where we see two glowing black
holes that are getting very close.

But not all these matches
will end with a knockout.

Black hole collisions happen
all the time,

but they don't always go
according to plan.

When black holes come together,
really strange things can happen.

The Hubble Space Telescope
spots something strange

in a distant galaxy
called 3C186.

It's a quasar, an active
supermassive black hole.

But it's in the wrong place.

In nearly every galaxy, we see

the supermassive black hole
sits right at the center.

That makes sense.

Because that's the only place with
enough material to power them.

But in 3C186,
that's not what we see.

The supermassive black hole
is displaced from the center.

And not a little bit.
It's 35,000 light years.

So to see a quasar 35,000
light years away from the core

means something really violent
had to happen there.

The quasar is racing away
from the center of the galaxy

at over four million miles an hour.

That is insane!

The magnitude of the energy
and the forces required

are just something
unimaginable.

So what can kick

a giant black hole
out of a galaxy?

What has that kind of power?

The answer is a clash
that wasn't evenly matched.

The two supermassive black holes
were different sizes,

a middleweight boxer
taking on a heavyweight.

When humans set up a fight,
we like to make it fair

because it's sport.
Nature doesn't care about sport.

It's survival of the fittest.

This is not a fair fight.
It's over before it even begins.

One punch and it's a K-O.

As these two black holes
are merging,

there's one really small
black hole

and one much bigger black hole.

The whole system wobbles around

and it can get more of
a gravitational wave kick

in one direction than the other.

And that's momentum. That's a push.
That's enough energy

to kick the black hole out.

The lopsided gravitational punch

sends the merged
supermassive black hole

on a one-way trip to oblivion.

This tells us that
gravitational waves can be

tremendously powerful. They can
move a supermassive black hole

out from the center of a galaxy
and send it on its way.

But it just carries on drifting.
There's no way to stop it.

And who knows?
In a few million years,

it could just drift entirely
out of its galaxy

and go floating off
into deep space.

In some matches, the fighters
don't even land a punch.

Scientists spot
a supermassive black hole

named B3 1715+425.

This black hole is strange.

Stripped of all its stars,

it hurtles through empty space
at 4.5 million miles an hour.

The first thing that draws
our attention

is this faint trail of debris
across the sky.

There is actually a trail leading
back to the center of the galaxy.

It's kinda like a dump truck
that's filled with dirt

driving down the highway,
and the dirt's flying off behind it.

This is a naked black hole.

The exposed supermassive black hole
has lost its stars and galaxy.

A champion stripped of its fans
and entourage.

So what event is powerful enough

to strip a supermassive black hole
of its entire host galaxy?

That has to be something
really big.

B3 is a smallish galaxy

and it got into a scrap
with a much bigger one.

The stronger gravity
of the bigger galaxy

stripped the stars away from
that black hole and shot it out.

Typically, in the universe when
something's bigger and more massive,

it wins.
So this is true for galaxies.

A big galaxy
versus a little galaxy,

put your money on the big one.

But when two evenly-matched
heavyweights enter the ring...

...it's time for the main event.

A clash of the titans.

I grew up watching boxing
with my dad,

so I've always been a boxing fan.

And I love a great battle.
And what's a bigger battle

than a head-on collision between
two supermassive black holes?

If you're a boxing fan,
this is the big one.

We are ready.
We are on the edge of our seats.

We've got two
supermassive black holes,

each one is in their corner,
and they're getting ready

for the fight of the century.

I mean, they're just gonna
go at it, like goosh, goosh.

I would watch that.
I'd pay-per-view that.

It doesn't get any better
than this. These are prize-fighters

at the top of their game,
they're trained to a T,

they're beefed up,
they are ready to rumble.

Welcome to the heavyweight
championship of the universe.

Weighing in at eight billion
solar masses,

we have The Galactic Destroyer,

M101 star.

And in the other corner,
at a punishing 7.8 billion suns,

The Star Crusher,
NSC 47 star.

They are pumped
and ready to rumble.

So here it is. We're finally here.

The crowd is roaring.

The bell has rung and the fighters
are approaching each other.

They are ready to go at it.

Let's have a clean fight, fellas.
Touch hands

and go back to your corners.

Round One.
The two heavyweights circle,

testing the other's defenses.

The black holes are gonna do
what the boxers are gonna do.

They're gonna circle each other
and they're gonna orbit each other

and they're gonna
size each other up.

Once these two supermassive
black holes are close enough,

they're gravity inexorably is
gonna draw them together.

As the two supermassive black holes
get closer,

they throw a few
exploratory jabs...

...triggering bursts of
gravitational waves

that warp everything in their path.

These enormous
gravitational waves

are completely deforming the fabric
of space time around them.

Not just a little bit, but a lot!

It's like feeling the fighters
approach in the boxing ring

from the next town over.

Next, the supermassive
black holes' gravity

throws in a couple of right hooks

straight into the accretion disks.

What could happen is that
they start to form like

an angle grinder.
You'll see sparks flying

as they try to merge and form
a new, single accretion disk.

When those accretion disks collide,

the whole thing is gonna light up
like the 4th of July.

Spiraling in
at millions of miles an hour

the heavyweight fighters get close,

delivering punishing body blows.

The event horizons, the surface of
the supermassive black holes,

are about to touch.

In their final moments,
these two supermassive black holes

are orbiting each other
at a significant fraction

of the speed of light,

and their event horizons
will touch.

And they'll eventually merge into
one new supermassive black hole.

You might think: don't they
bump into each other

like bowling balls? No, they don't.

Because what we're calling
the edge of the black hole

is actually not a thing.
That's just the surface

around the black hole. Gravity is
so strong, nothing can come out.

The two supermassive black holes
finally merge,

releasing around five percent
of the mass they've gathered

over billions of years
in an enormous burst

of gravitational waves.

The amount of energy
we're talking about...

There's nothing to compare it to.
It's mind-crushing.

There's really almost no point
in thinking about it.

It's just not something I think
that I can wrap my head around.

Coming from where I come from,

you know, you don't show weakness.

So I'm not gonna say that
the collision of two black holes

is more powerful
than one of my punches,

but... it's close.

The gigantic and powerful
gravitational waves

race out from the collision zone,

leaving a single merged black hole.

This supermassive black hole,
after it merges,

permanently deforms the fabric
of space time around it.

And this deformation travels out
at the speed of light.

The surviving 95 percent of mass

from the two colliding
supermassive black holes

is now locked in a single
ultramassive black hole.

The undisputed super heavyweight
champion of the universe.

At least for now.

It seems the universe is always
upping the ante.

Could there be something even more
violent we haven't discovered yet?

The universe keeps wanting to give us
something more violent all the time.

Energy locked in hydrogen atoms

formed at the birth
of the universe

is finally released
in the violent collision

and builds an ultramassive
black hole.

This is one of the most beautiful
stories in our universe.

You have the most energetic
collision,

the most amount of energy released,
the most violent event

can trace its origins
to the humble hydrogen atom.

There are things constantly
being built up and then destroyed.

It's sort of the cycle of life
in our universe

that evolves various exotic
phenomenon

and makes them into something
more beautiful and transformative.

Our universe has managed to create

both these fearsome weapons
of mass destruction,

monster black holes,

and also conscious life

that can write poetry
and ponder the meaning of it all.

So, we have our champion.

Matter compressed
and then smashed together

by supermassive black holes

creates the most violent event
in the universe.

I don't think there's a contest.

The supermassive black hole
collisions

are the most energetic,
just like mind-numbingly large

amounts of energy
in these collisions.

A merger of two
supermassive black holes

is at the absolute top end
extreme of that

for all possible events
in the entire universe.

A supermassive black hole merger

is the most violent thing that
we can observe in the universe.

Subtitling by Iyuno