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You might have seen
a boxing match on TV.

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

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a contest like this.

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Take your ringside seat
to the fight of the cosmos.

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This is gonna be a wonderful fight
to witness,

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

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

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You don't even see it coming.

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

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But they can deliver
the ultimate knockout blow.

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It is a soul-chilling,

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

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It's a fight between two
supermassive black holes.

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Forget about the World
Heavyweight Championships,

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this is the universe's
heavyweight championships.

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Get ready for the heavyweight
championship of the universe.

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2021. Scientists detect

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a gigantic rumble deep in space.

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A tsunami of gravitational waves.

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Giant ripples racing
across the universe.

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Gravitational waves that big
have to come from

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a giant, cataclysmic event.

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The universe is immense

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and full of very violent events

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that are happening
every single day.

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The universe is a scary place.

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There is violence
everywhere we look.

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The growls and roars are clues

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about the ultimate cosmic brawl.

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The most violent event
in the universe.

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

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

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

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but you can hear that rumble
of the distant thunder

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and you know that it's coming.

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This distant rumble of
gravitational waves

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is like the footwork
of heavyweights

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pounding the canvas
of the boxing ring.

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The waves are caused by
something massive

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throwing its weight around.

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

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Our experiments have picked up
the signal

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of two small stellar mass
black holes colliding.

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These waves are high-pitched

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and ring like a boxing bell.

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The deep space growl
is a much lower frequency.

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Like the roar of a crowd.

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The difference in frequencies
would be even more exaggerated

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than the difference between
a sparrow chirping

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and the sound coming from
a blue whale underwater.

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It would be orders of magnitude
more different than that.

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The low frequency
of the deep-space rumble

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tells us that the waves
are colossal.

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Imagine throwing a stone
in the water

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and watching the little ripples
come out.

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Now imagine throwing in a boulder
a billion times more massive

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and watching the huge waves
that come from that.

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Those are the waves
that we're looking at.

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These are more difficult to detect

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because the waves are so big.

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One of their wavelengths
is about 15 light years.

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You could wait for 15 years

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and only have one wavelength
go by the Earth.

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

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So, to search for the source
of these giant waves

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Chiara Mingarelli and her team

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use a detector already in space.

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Something large enough to pick up
these galactic heavyweights.

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Spinning dead stars called pulsars.

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Our galaxy is awash with pulsars.

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

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They're like cosmic lighthouses.

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

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But when a huge gravitational wave
hits them,

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the timing
gets knocked out of whack.

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That pulsar's gonna basically
rock back and forth,

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

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that we measure from that object.

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To identify the source
of the gravitational waves,

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Chiara and her team
measure the wobbles

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of 100 pulsars spread across
light years of space.

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It's like a tsunami.

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

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And as the tsunami passes by,

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

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So our pulsar timing array

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is a gravitational wave
warning system.

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The pulsar array has identified
the source of the tsunami

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of gravitational waves.

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

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very low-pitch gravitational waves

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would be the collisions
of supermassive black holes.

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They're massive. They're huge.

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And they know how to throw
their weight around.

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Supermassive black hole binaries

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produce the loudest
gravitational waves in the universe.

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The gravitational waves' signal

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revealed something extraordinary.

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It's not just gravitational waves

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coming from one black hole
binary pair,

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it's actually from
the cosmic population

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of supermassive
black hole binaries.

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Chiara and her team think there
may be tens of thousands

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of heavyweight bouts going on.

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Now, the scientists want to
pick out the sound

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of one single collision

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between two supermassive
black holes

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from the background roar.

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If we were to hear
a supermassive black hole merger,

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it would wound like
a very low-frequency growl,

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this... whoooooooo

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that would last
about 25 million years.

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

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trading blows in real time.

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

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

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

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But we haven't seen this one.

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It's odd if you think about it.

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We haven't seen the biggest one.

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We haven't seen mergers between
supermassive black holes.

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But that may be about to change.

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Chiara predicts
there are 112 fighters

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who are pumped up
and ready to enter the ring.

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

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at least one supermassive
black hole merger.

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

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Let's put that in context.

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We talk about how supernova
are some of the most

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explosive, energetic things
in our universe.

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Well, colliding supermassive
black holes

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are a billion billion billion
billion times more energetic

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than a supernova.

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Think about all of the light

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being emitted by everything
in the universe,

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every star, every galaxy.

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In one instant, two supermassive
black holes colliding

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could release 100 million times
that energy.

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Imagine being punched in the face

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by the biggest, baddest
heavyweight of all time.

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Ouch.
This is way bigger than that.

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Where does all this energy
come from?

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Surprisingly, it originates

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in the smallest atoms
in the cosmos

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in a story that dates back
billions of years,

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all the way to the birth
of the universe.

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2020. The earthbound
gravitational wave detector, LIGO,

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picks up the distinctive signal

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of a stellar mass black hole merger.

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What we saw was a black hole

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of 85 times the mass of our sun

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

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smashing together
to create a combined black hole.

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As someone who studies
black hole mergers,

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this was a really exciting event.

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We're talking about the largest,
the heaviest,

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

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

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it's still a small fry.

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Like lightweight boxers, the two
black holes circle each other

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and emit low-energy
gravitational waves.

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This energy loss causes
the black holes

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to spiral in together.

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

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...forming a single black hole

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and releasing a huge blast
of gravitational waves.

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But when astronomers examine
the single merged black hole,

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something doesn't add up.

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

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you get to 150 times
the mass of our sun.

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But actually,
the black hole that's left

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

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So the mass you have
before the event

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does not equal the mass you have
after the event.

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What happened to that missing
eight solar masses?

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The way these black hole mergers
work

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

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gets converted into energy.

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It all comes down to E=mc2.

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

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E is the energy, and M is the mass.

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Einstein taught us that
mass and energy are related.

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

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In this case, the violence
of the collision

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transforms 18,000 trillion trillion
tons of matter

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into an explosion
of gravitational waves.

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In just a fraction of a second,

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eight suns-worth of matter

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is converted into pure,
unadulterated energy.

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The amount of energy released
was so great

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

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burning in the universe,
it was bigger than that.

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This event was a collision
between relative lightweights.

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Two stellar mass black holes.

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To understand heavyweight bouts,
we need to scale up

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to supermassive black holes.

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In the universe of sports,

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supermassive black holes are
the heavyweight contenders.

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

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

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

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This is M87 star,

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one of the largest supermassive
black holes

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in our cosmic zip code.

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M87 star is huge.

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It weighs about six billion
solar masses,

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

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A collision between two six billion
solar mass supermassive black holes

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

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

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It's hard to use words

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to express how much energy
this is

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

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

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In physics, we have these
comparisons

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so we can get a mental picture,

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but for something like this
there is no mental picture.

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That is so big!

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So where does this destructive
mass and energy come from?

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It starts with
the simplest ingredient, hydrogen.

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Hydrogen is the basic
building block of the universe.

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

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Hydrogen atoms contain
a huge amount of energy,

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just like all matter does.

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And if it's unlocked
in a certain way,

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there can be huge explosions.

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You take the mass contained
simply in my hand

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and you could blow up
pretty much the entire Earth.

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Matter has energy
because it formed from energy

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in the early moments
of the universe.

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In many ways, atoms are reservoirs

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of stored energy
from the big bang.

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13.8 billion years ago,

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the universe ignites

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in a super-hot ball
of intense energy.

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

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

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As that early energy
starts to cool,

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it can start to form
primitive matter.

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The universe takes that first matter
and energy

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in the form of hydrogen atoms

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and starts the process of creating
a supermassive black hole.

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Step one, build giant stars.

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So, gravity brings together

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gas, dust, hydrogen,
all of that stuff,

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00:14:41,520 --> 00:14:43,720
and as the clouds become
more dense,

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they attract even more material.

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As they spin, they get
hotter and hotter.

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And as that temperature
and pressure increase,

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finally it ignites nuclear fusion
within the core

251
00:14:55,960 --> 00:14:58,040
and creates an actual star.

252
00:15:00,480 --> 00:15:03,760
These huge stars are like
cosmic rock stars.

253
00:15:03,840 --> 00:15:06,240
They live fast and die young.

254
00:15:07,800 --> 00:15:11,720
When they die, they flame out
in a huge explosion.

255
00:15:12,800 --> 00:15:14,680
A supernova.

256
00:15:14,760 --> 00:15:18,800
The entire star turns itself
inside out

257
00:15:18,880 --> 00:15:21,600
and releases a shockwave,

258
00:15:21,680 --> 00:15:24,160
going a good fraction
of the speed of light,

259
00:15:24,240 --> 00:15:27,720
and releases enough energy
to just obliterate you.

260
00:15:29,600 --> 00:15:33,120
If the dying star is more than
15 stellar masses,

261
00:15:33,200 --> 00:15:36,320
its core collapses
into a black hole.

262
00:15:38,040 --> 00:15:40,640
It's kind of astounding
what the universe is doing.

263
00:15:40,720 --> 00:15:44,560
It's taking incredibly simple things
like hydrogen atoms and using gravity

264
00:15:44,640 --> 00:15:47,000
to ultimately bring
all this stuff together

265
00:15:47,080 --> 00:15:49,640
and make things like black holes.

266
00:15:49,720 --> 00:15:53,480
I find it quite beautiful how
our whole cosmic history

267
00:15:53,560 --> 00:15:55,320
is the story of

268
00:15:55,400 --> 00:15:58,040
little things coming together
into bigger things.

269
00:15:58,120 --> 00:16:02,520
But these stellar mass black holes
are tiny flyweights.

270
00:16:02,600 --> 00:16:04,960
To step up to
the heavyweight division,

271
00:16:05,040 --> 00:16:08,720
they have to grow billions of times
more massive.

272
00:16:08,800 --> 00:16:11,040
But how?

273
00:16:11,120 --> 00:16:13,520
How do black holes become
supermassive?

274
00:16:14,840 --> 00:16:18,240
This is the age-old question.
We're not really sure.

275
00:16:19,280 --> 00:16:21,840
The current stated understanding

276
00:16:21,920 --> 00:16:25,400
of how black holes
become supermassive is like... uh,

277
00:16:25,480 --> 00:16:27,440
we're confused,
we really don't know.

278
00:16:27,520 --> 00:16:29,560
In June of 2018,

279
00:16:29,640 --> 00:16:31,640
we spotted a clue.

280
00:16:31,720 --> 00:16:33,720
An enormous flash of light.

281
00:16:34,720 --> 00:16:37,200
AT2018cow,

282
00:16:37,280 --> 00:16:39,040
nicknamed "The Cow",

283
00:16:39,120 --> 00:16:41,480
was the brightest explosion
ever recorded.

284
00:16:42,600 --> 00:16:44,640
A huge amount of energy
was released

285
00:16:44,720 --> 00:16:47,400
and then, all of a sudden,
everything was gone.

286
00:16:47,480 --> 00:16:50,160
This explosion was
incredibly violent.

287
00:16:50,240 --> 00:16:53,640
At first, it was thought to just be
a supernova, a flash of light.

288
00:16:53,720 --> 00:16:56,440
But over time, it became clear
that this was something

289
00:16:56,520 --> 00:16:58,400
much more powerful.

290
00:16:58,480 --> 00:17:01,360
It was too bright, basically,
to be a supernova.

291
00:17:01,440 --> 00:17:04,520
It was extremely bright
and it didn't fit into

292
00:17:04,600 --> 00:17:06,920
any of our theoretical
understandings

293
00:17:07,000 --> 00:17:09,600
of how bright supernovas
should be.

294
00:17:09,680 --> 00:17:13,200
One explanation is that
the light may have come from

295
00:17:13,280 --> 00:17:16,480
a black hole feeding on a small,
white dwarf star,

296
00:17:16,560 --> 00:17:18,600
weighing less than the Sun.

297
00:17:19,800 --> 00:17:21,800
What really seemed to fit
that model

298
00:17:21,880 --> 00:17:24,680
was a star getting too close
to a black hole

299
00:17:24,760 --> 00:17:26,240
and getting ripped apart,

300
00:17:26,320 --> 00:17:29,040
and then everything going
right down the black hole.

301
00:17:29,120 --> 00:17:32,960
A black hole gains mass
every time it eats something.

302
00:17:33,040 --> 00:17:35,920
That's how they grow. Whether
it's a gas cloud or a star

303
00:17:36,000 --> 00:17:37,360
or another black hole,

304
00:17:37,440 --> 00:17:40,120
once it gains that mass
it's gained that mass.

305
00:17:42,760 --> 00:17:45,280
People often ask me,
What happens to the mass

306
00:17:45,360 --> 00:17:48,200
that falls into a black hole?
Does it go to another dimension?

307
00:17:48,280 --> 00:17:49,440
And the answer is no.

308
00:17:49,520 --> 00:17:52,280
It's still there.
It's inside the black hole.

309
00:17:52,360 --> 00:17:54,880
They get bigger. They grow.

310
00:17:54,960 --> 00:17:58,920
Could this be how weak,
flyweight black holes

311
00:17:59,000 --> 00:18:02,920
turn into mean and powerful
supermassive heavyweights?

312
00:18:03,000 --> 00:18:05,000
The star is like protein,

313
00:18:05,080 --> 00:18:08,040
and the black hole is like
a boxer.

314
00:18:09,840 --> 00:18:13,080
And so, the more protein they get,
the more stars they consume,

315
00:18:13,160 --> 00:18:16,360
the stronger they get,
the more destructive they can be.

316
00:18:18,960 --> 00:18:22,520
But there's a problem with
the training program explanation.

317
00:18:24,320 --> 00:18:26,880
Eating small stars one at a time

318
00:18:26,960 --> 00:18:29,480
just doesn't add enough mass
fast enough

319
00:18:29,560 --> 00:18:32,760
to grow the supermassive black holes
that we see today.

320
00:18:32,840 --> 00:18:37,080
That's like boxers eating
just one egg per day.

321
00:18:38,240 --> 00:18:41,720
Like them, black holes
need much bigger meals.

322
00:18:43,160 --> 00:18:45,800
And in 2020, we detected one.

323
00:18:47,520 --> 00:18:49,960
A sudden burst of
gravitational waves

324
00:18:50,040 --> 00:18:53,040
from a black hole
gorging on the remains

325
00:18:53,120 --> 00:18:55,160
of a dead star...

326
00:18:56,560 --> 00:18:58,320
...called a neutron star.

327
00:18:59,760 --> 00:19:03,080
For scientists, January 2020
was exciting

328
00:19:03,160 --> 00:19:05,880
because it was the first time
LIGO observed

329
00:19:05,960 --> 00:19:09,280
the very first black hole
neutron star merger.

330
00:19:10,320 --> 00:19:12,600
Neutron stars may be small

331
00:19:12,680 --> 00:19:15,920
but they are inconceivably dense.

332
00:19:16,000 --> 00:19:19,000
You want to talk about an enormous
mass, talk about a neutron star.

333
00:19:19,080 --> 00:19:20,680
That's one heck of a snack.

334
00:19:20,760 --> 00:19:25,000
The black hole swallowed
the neutron star in one gulp.

335
00:19:26,560 --> 00:19:30,280
So, this black hole
ate a whole neutron star,

336
00:19:30,360 --> 00:19:34,400
which means it gained just over ten
percent of its entire body weight

337
00:19:34,480 --> 00:19:36,480
in one shot.

338
00:19:36,560 --> 00:19:38,880
Ten percent
doesn't sound like a lot,

339
00:19:38,960 --> 00:19:42,000
but then we detected
another black hole

340
00:19:42,080 --> 00:19:45,160
swallowing a neutron star
just ten days later,

341
00:19:45,240 --> 00:19:48,280
suggesting that there are lots
of black holes

342
00:19:48,360 --> 00:19:50,360
bulking up across the universe.

343
00:19:51,560 --> 00:19:53,640
But even with this extreme
weight gain,

344
00:19:53,720 --> 00:19:57,320
it's probably not enough
to get supermassive.

345
00:19:57,400 --> 00:19:59,240
They need to eat even more.

346
00:20:00,240 --> 00:20:02,880
If you're a black hole
and you want to get bigger,

347
00:20:02,960 --> 00:20:05,800
your best bet is to merge
with another black hole.

348
00:20:06,800 --> 00:20:08,800
But there's a catch.

349
00:20:08,880 --> 00:20:11,720
So,
if you're a flyweight black hole,

350
00:20:11,800 --> 00:20:13,800
and you try to eat

351
00:20:13,880 --> 00:20:16,720
all of the other flyweight
black holes,

352
00:20:16,800 --> 00:20:20,080
there's just not enough time
in the history of the universe

353
00:20:20,160 --> 00:20:22,640
for you to become
a supermassive black hole.

354
00:20:22,720 --> 00:20:25,280
But you can make it
to middleweight.

355
00:20:26,280 --> 00:20:30,440
So, exactly how supermassive
black holes grow so large

356
00:20:30,520 --> 00:20:32,680
remains an open question.

357
00:20:32,760 --> 00:20:37,120
We do know that the process started
in the very early universe

358
00:20:37,200 --> 00:20:39,520
with a journey
from the lightest element

359
00:20:39,600 --> 00:20:42,720
to the most intimidating object
in the cosmos.

360
00:20:42,800 --> 00:20:45,840
It's so interesting
how the cosmos can take something

361
00:20:45,920 --> 00:20:47,920
as simple as a hydrogen atom

362
00:20:48,000 --> 00:20:50,760
and build stellar-mass black holes

363
00:20:50,840 --> 00:20:53,400
and intermediate-mass black holes

364
00:20:53,480 --> 00:20:55,720
and even supermassive black holes

365
00:20:55,800 --> 00:21:00,360
out of these really densely
compressed hydrogen atoms.

366
00:21:00,440 --> 00:21:02,320
It's really a wonder.

367
00:21:02,400 --> 00:21:07,440
Now, 13.8 billion years
after the big bang,

368
00:21:07,520 --> 00:21:11,440
supermassive black holes
feed and flex their muscles

369
00:21:11,520 --> 00:21:15,720
ready to fight for the heavyweight
championship of the universe.

370
00:21:15,800 --> 00:21:17,800
These supermassive black holes

371
00:21:17,880 --> 00:21:20,640
have been bulking up
since the age of the universe.

372
00:21:20,720 --> 00:21:24,520
These black holes have been
getting ready for the fight.

373
00:21:24,600 --> 00:21:28,600
They have been bulking up, they
have been eating entire stars

374
00:21:28,680 --> 00:21:31,960
as snacks,
to get the mass they need.

375
00:21:32,040 --> 00:21:33,960
So they are ready to rumble.

376
00:21:34,960 --> 00:21:36,960
It's not The Rumble in the Jungle.

377
00:21:37,040 --> 00:21:40,920
This is the battle
to be the boss of the cosmos.

378
00:21:41,000 --> 00:21:46,720
Supermassive black hole
versus supermassive black hole.

379
00:21:46,800 --> 00:21:48,840
Fought in the grandest arena.

380
00:21:50,560 --> 00:21:53,600
The fighters' entourage,
their host galaxies,

381
00:21:53,680 --> 00:21:55,680
escort them to the ring.

382
00:21:55,760 --> 00:21:58,800
But even this journey is violent,
triggering starbursts,

383
00:21:58,880 --> 00:22:01,640
jets, and carnage.

384
00:22:04,240 --> 00:22:06,520
Things are about to get nasty.

385
00:22:07,640 --> 00:22:09,960
Galaxies can look calm and serene,

386
00:22:10,040 --> 00:22:12,520
but they can get into
pretty big scraps.

387
00:22:15,240 --> 00:22:17,440
There's a lot of them that are
totally messed up,

388
00:22:17,520 --> 00:22:19,320
and are clearly merging
with each other.

389
00:22:24,960 --> 00:22:29,320
Eventually, even our own galaxy
will merge with another galaxy.

390
00:22:30,320 --> 00:22:32,240
In a few billion years,

391
00:22:32,320 --> 00:22:35,080
a timescale that I'm not
too worried about myself,

392
00:22:35,160 --> 00:22:38,400
the Milky Way and
the Andromeda Galaxy will collide.

393
00:22:38,480 --> 00:22:41,560
The Milky Way and Andromeda each
have supermassive black holes.

394
00:22:41,640 --> 00:22:43,080
And when they collide,

395
00:22:43,160 --> 00:22:45,200
their supermassive black holes
will collide too.

396
00:22:49,320 --> 00:22:52,520
This is an incredibly dangerous
event for our solar system.

397
00:22:52,600 --> 00:22:55,240
Our solar system could be
swept out

398
00:22:55,320 --> 00:22:58,200
to be somewhere else
in this newly-formed galaxy,

399
00:22:58,280 --> 00:23:01,680
or it could be completely ejected
from the galaxy.

400
00:23:03,360 --> 00:23:06,280
If there's any life around
near the merger

401
00:23:06,360 --> 00:23:09,720
of these supermassive black holes,
it would be obliterated.

402
00:23:12,200 --> 00:23:15,880
When galaxies fight, their gravity
pulls on each other,

403
00:23:15,960 --> 00:23:18,600
twisting and distorting
their structures.

404
00:23:20,040 --> 00:23:22,840
The galaxy will be warped
and morphed into

405
00:23:22,920 --> 00:23:25,840
different ways
that we can only imagine

406
00:23:25,920 --> 00:23:27,920
how twisted it would be.

407
00:23:29,400 --> 00:23:31,040
This violent cosmic tango

408
00:23:31,120 --> 00:23:33,880
brings the two supermassive
black holes together.

409
00:23:35,480 --> 00:23:39,560
It's elegant. It's beautiful.
It's this billion-year

410
00:23:39,640 --> 00:23:44,200
choreographed dance that is entirely
conducted by gravity.

411
00:23:47,560 --> 00:23:50,280
The two heavyweight fighters
approach each other.

412
00:23:50,360 --> 00:23:53,680
Their feet beat out a rhythm
on the canvas,

413
00:23:53,760 --> 00:23:55,760
just like circling black holes

414
00:23:55,840 --> 00:23:58,760
release low-energy
gravitational waves.

415
00:24:00,160 --> 00:24:02,000
You have these giant beasts

416
00:24:02,080 --> 00:24:04,840
that are stalking
around each other

417
00:24:04,920 --> 00:24:09,600
and as they do, they create
these gravitational waves.

418
00:24:11,120 --> 00:24:13,080
June, 2021.

419
00:24:13,160 --> 00:24:16,480
Astronomers photograph
a galactic collision

420
00:24:16,560 --> 00:24:20,840
and witness a spectacular
pre-fight fireworks show.

421
00:24:22,120 --> 00:24:25,200
One of the amazing things that can
happen when galaxies collide is

422
00:24:25,280 --> 00:24:27,680
they can create tremendous
starbursts.

423
00:24:29,160 --> 00:24:32,760
There is a big in-rush as all of
that gas follows that gravity.

424
00:24:32,840 --> 00:24:36,880
As the gas gets hotter and denser,
it creates shockwaves.

425
00:24:38,360 --> 00:24:41,520
And each shockwave actually creates
a new generation of stars

426
00:24:41,600 --> 00:24:44,160
going out around the core
of the galaxy.

427
00:24:44,240 --> 00:24:47,400
The sudden starburst lights up
the merging galaxies.

428
00:24:47,480 --> 00:24:51,640
The in-rushing gas also fuels
the prize-fighters,

429
00:24:51,720 --> 00:24:54,160
the supermassive black holes

430
00:24:54,240 --> 00:24:57,800
spiraling towards
the merging galactic center.

431
00:25:00,520 --> 00:25:03,440
But only if the galaxies approach
at the right angle.

432
00:25:03,520 --> 00:25:07,840
It's not the case that every merger
feeds a black hole.

433
00:25:07,920 --> 00:25:11,320
Sometimes it actually
strips material

434
00:25:11,400 --> 00:25:13,920
away from the central regions

435
00:25:14,000 --> 00:25:17,240
and then there's no food there
for the black holes to eat.

436
00:25:19,040 --> 00:25:21,720
A head-on collision
with another black hole

437
00:25:21,800 --> 00:25:25,720
could strip the material
around the supermassive black hole.

438
00:25:25,800 --> 00:25:27,800
With nothing there,

439
00:25:27,880 --> 00:25:30,080
the black holes can't power
themselves.

440
00:25:32,000 --> 00:25:35,680
To get the biggest bang
requires an attacking angle

441
00:25:35,760 --> 00:25:38,360
that'll help feed
a starving black hole.

442
00:25:39,520 --> 00:25:41,640
With a grazing collision,

443
00:25:41,720 --> 00:25:45,880
the gas pockets surrounding
the black hole survive

444
00:25:45,960 --> 00:25:47,960
and gain more mass.

445
00:25:48,040 --> 00:25:49,760
And that can power it even more.

446
00:25:49,840 --> 00:25:52,320
It can make it
even more spectacular.

447
00:25:52,400 --> 00:25:55,280
If there's a big
supermassive black hole,

448
00:25:55,360 --> 00:25:58,760
that suddenly finds it
surrounded by loads of gas

449
00:25:58,840 --> 00:26:00,920
and other material it can eat,

450
00:26:01,000 --> 00:26:04,120
it goes on
a kind of feeding frenzy.

451
00:26:04,200 --> 00:26:06,760
If you're a hungry
supermassive black hole,

452
00:26:06,840 --> 00:26:09,120
then this is your lunchtime buffet.

453
00:26:10,720 --> 00:26:14,040
Not all the gas falls into
the supermassive black hole.

454
00:26:15,640 --> 00:26:18,640
Other parts of the matter actually
gets caught up in what we call

455
00:26:18,720 --> 00:26:22,280
an "accretion disk" rotating around
the outside of the black hole.

456
00:26:23,360 --> 00:26:26,960
This bright vortex spins around
the supermassive black hole

457
00:26:27,040 --> 00:26:29,200
at over two million miles an hour.

458
00:26:30,720 --> 00:26:33,800
The material in the disk
rubs against itself,

459
00:26:33,880 --> 00:26:35,880
creating friction.

460
00:26:35,960 --> 00:26:39,680
Friction generates heat.
If I rub my hands together,

461
00:26:39,760 --> 00:26:41,760
they get a little bit warm.

462
00:26:41,840 --> 00:26:43,840
If I rub my hands together

463
00:26:43,920 --> 00:26:46,560
at hundreds of thousands of miles
per hour,

464
00:26:46,640 --> 00:26:48,760
it's gonna get
very, very, very warm.

465
00:26:50,440 --> 00:26:54,880
The accretion disk keeps up
blasting out intense light.

466
00:26:57,360 --> 00:27:00,440
In 2020,
NASA's Hubble Space Telescope

467
00:27:00,520 --> 00:27:04,120
saw two fueled-up
supermassive black holes

468
00:27:04,200 --> 00:27:06,680
lighting up for the fight.

469
00:27:07,640 --> 00:27:09,360
We call them quasars.

470
00:27:11,160 --> 00:27:16,120
Quasars are a sub-class of
very bright black holes

471
00:27:16,200 --> 00:27:18,320
that are emitting
huge amounts of power.

472
00:27:18,400 --> 00:27:21,440
So these can be seen at
the far reaches of the universe.

473
00:27:24,240 --> 00:27:27,040
Black holes, these so-called
dark things,

474
00:27:27,120 --> 00:27:29,120
when they're growing
at a very high rate,

475
00:27:29,200 --> 00:27:31,880
are some of the brightest lights
in the universe.

476
00:27:33,160 --> 00:27:37,280
To date, we've detected
over 100 pairs of quasars

477
00:27:37,360 --> 00:27:39,760
in the cores of merging galaxies.

478
00:27:39,840 --> 00:27:43,680
We think they will all
eventually collide.

479
00:27:45,400 --> 00:27:47,440
But before they do, they'll put on

480
00:27:47,520 --> 00:27:50,640
a spectacular and lethal
light show...

481
00:27:52,560 --> 00:27:54,560
A common theme in science fiction

482
00:27:54,640 --> 00:27:57,240
are different kinds of jets
of energy or beams

483
00:27:57,320 --> 00:27:59,720
that people shoot out of their eyes
or their hands.

484
00:27:59,800 --> 00:28:02,800
Well, supermassive black holes
do that, too.

485
00:28:02,880 --> 00:28:05,720
...firing out relativistic jets.

486
00:28:07,840 --> 00:28:09,840
When those jets fire up,

487
00:28:09,920 --> 00:28:13,240
that's when you're talking about
superstar.

488
00:28:13,320 --> 00:28:15,040
Really, really bright lights.

489
00:28:15,120 --> 00:28:17,720
And at this point, the galaxy
is lit up and ready to go.

490
00:28:19,840 --> 00:28:24,040
These are the spotlights on
Madison Square Garden.

491
00:28:24,120 --> 00:28:27,160
This is telling you that the event
is going down.

492
00:28:29,520 --> 00:28:31,840
A single
supermassive black hole jet

493
00:28:31,920 --> 00:28:34,520
will produce more energy
in a second

494
00:28:34,600 --> 00:28:38,880
than the sun will produce in its
entire ten-billion-year lifetime.

495
00:28:43,560 --> 00:28:46,680
Imagine a laser of radiation

496
00:28:46,760 --> 00:28:49,520
that is light years in length
and across.

497
00:28:49,600 --> 00:28:53,880
That's what we're talking about.
This thing would fry a planet.

498
00:28:54,800 --> 00:28:56,400
This is no pre-fight hype.

499
00:28:57,600 --> 00:29:01,440
In February, 2020
we saw the impact of a jet.

500
00:29:03,080 --> 00:29:05,120
So in the Ophiuchus galaxy cluster,

501
00:29:05,200 --> 00:29:06,840
there's an enormous void

502
00:29:06,920 --> 00:29:09,480
that is 15 times wider
than the Milky Way galaxy.

503
00:29:09,560 --> 00:29:11,880
And this has all been sculpted,
carved

504
00:29:11,960 --> 00:29:15,680
by jets
from a supermassive black hole.

505
00:29:15,760 --> 00:29:17,800
It's like this scar
on the universe.

506
00:29:17,880 --> 00:29:21,080
It's a million light years across.
It's huge.

507
00:29:21,160 --> 00:29:25,560
Scientists calculate the impact
of the jet hitting the cluster

508
00:29:25,640 --> 00:29:30,640
was equivalent to a 20 billion
billion megaton TNT explosion

509
00:29:30,720 --> 00:29:33,040
every thousandth of a second

510
00:29:33,120 --> 00:29:35,640
for 240 million years.

511
00:29:39,520 --> 00:29:42,480
But how does a black hole generate
so much power?

512
00:29:42,560 --> 00:29:44,920
Even though
there's a lot of energy

513
00:29:45,000 --> 00:29:47,640
in the accretion disk
surrounding a black hole,

514
00:29:47,720 --> 00:29:51,400
there's not enough to launch
these really powerful jets.

515
00:29:51,480 --> 00:29:54,600
Because we can't account for it
any other way,

516
00:29:54,680 --> 00:29:56,400
there must be something else

517
00:29:56,480 --> 00:29:58,920
that's contributing energy
to these jets.

518
00:30:01,040 --> 00:30:03,400
We get a clue in 2021

519
00:30:03,480 --> 00:30:06,360
when scientists publish
a new photo

520
00:30:06,440 --> 00:30:10,560
of the supermassive black hole
M87 star.

521
00:30:11,880 --> 00:30:13,880
It shows the accretion disk.

522
00:30:13,960 --> 00:30:17,720
The lines represent
magnetic field lines.

523
00:30:19,080 --> 00:30:22,520
The fast-spinning accretion disk
drags the magnetic field

524
00:30:22,600 --> 00:30:24,680
around the supermassive black hole,

525
00:30:24,760 --> 00:30:26,760
charging it up for the battle.

526
00:30:28,160 --> 00:30:30,800
The accretion disk
around a black hole

527
00:30:30,880 --> 00:30:33,840
isn't just swirling around
like crazy.

528
00:30:33,920 --> 00:30:37,280
It's also undulating and moving
and wiggling,

529
00:30:37,360 --> 00:30:41,000
and this causes the magnetic field
to fold in on itself.

530
00:30:41,080 --> 00:30:43,640
And every time it folds,
it amplifies itself,

531
00:30:43,720 --> 00:30:46,120
getting stronger and stronger
and stronger.

532
00:30:46,200 --> 00:30:50,800
This is a dynamo that powers
this incredible magnetic field.

533
00:30:50,880 --> 00:30:55,240
The magnetic field can't hold onto
the building energy any longer.

534
00:30:56,400 --> 00:30:58,000
It erupts.

535
00:30:58,080 --> 00:31:00,480
These magnetic field lines
then sweep up and away

536
00:31:00,560 --> 00:31:03,040
like a tornado.
And that can lift material

537
00:31:03,120 --> 00:31:05,600
away from the black hole
and the accretion disk

538
00:31:05,680 --> 00:31:08,080
and shoot it out into
intergalactic space.

539
00:31:09,560 --> 00:31:11,920
The relativistic jet's
immense power

540
00:31:12,000 --> 00:31:15,720
may be a showstopper, but when
it's time to land the killer punch

541
00:31:15,800 --> 00:31:17,800
supermassive black holes

542
00:31:17,880 --> 00:31:21,680
draw on an even more
powerful force, gravity.

543
00:31:21,760 --> 00:31:26,680
Jets are very powerful, but really
only on a relatively small scale.

544
00:31:26,760 --> 00:31:29,040
When you're talking about
cosmic scale,

545
00:31:29,120 --> 00:31:30,840
gravity always wins.

546
00:31:30,920 --> 00:31:33,160
Nothing is as powerful as gravity.

547
00:31:35,680 --> 00:31:41,480
Across the universe, supermassive
black holes duke it out

548
00:31:41,560 --> 00:31:45,480
in the cosmos' version of
heavyweight superfights.

549
00:31:45,560 --> 00:31:50,400
Supermassive black holes are
merging around us all the time.

550
00:31:50,480 --> 00:31:52,760
It's only our ability
to detect them

551
00:31:52,840 --> 00:31:55,360
that's preventing us
from seeing them.

552
00:31:57,040 --> 00:32:00,160
Scientists have identified
at least a dozen pairs

553
00:32:00,240 --> 00:32:03,400
of supermassive black holes
circling each other.

554
00:32:04,560 --> 00:32:07,080
We have some hints
of some galaxies

555
00:32:07,160 --> 00:32:09,000
where we think it might happen,

556
00:32:09,080 --> 00:32:12,280
where we see two glowing black
holes that are getting very close.

557
00:32:13,800 --> 00:32:16,520
But not all these matches
will end with a knockout.

558
00:32:17,880 --> 00:32:20,280
Black hole collisions happen
all the time,

559
00:32:20,360 --> 00:32:23,000
but they don't always go
according to plan.

560
00:32:23,080 --> 00:32:26,640
When black holes come together,
really strange things can happen.

561
00:32:29,160 --> 00:32:32,320
The Hubble Space Telescope
spots something strange

562
00:32:32,400 --> 00:32:36,160
in a distant galaxy
called 3C186.

563
00:32:38,080 --> 00:32:41,360
It's a quasar, an active
supermassive black hole.

564
00:32:43,640 --> 00:32:45,640
But it's in the wrong place.

565
00:32:46,640 --> 00:32:48,560
In nearly every galaxy, we see

566
00:32:48,640 --> 00:32:51,400
the supermassive black hole
sits right at the center.

567
00:32:51,480 --> 00:32:53,120
That makes sense.

568
00:32:53,200 --> 00:32:56,680
Because that's the only place with
enough material to power them.

569
00:32:56,760 --> 00:33:00,320
But in 3C186,
that's not what we see.

570
00:33:00,400 --> 00:33:03,480
The supermassive black hole
is displaced from the center.

571
00:33:03,560 --> 00:33:06,880
And not a little bit.
It's 35,000 light years.

572
00:33:06,960 --> 00:33:10,320
So to see a quasar 35,000
light years away from the core

573
00:33:10,400 --> 00:33:13,640
means something really violent
had to happen there.

574
00:33:13,720 --> 00:33:17,720
The quasar is racing away
from the center of the galaxy

575
00:33:17,800 --> 00:33:20,240
at over four million miles an hour.

576
00:33:20,320 --> 00:33:23,200
That is insane!

577
00:33:23,280 --> 00:33:26,360
The magnitude of the energy
and the forces required

578
00:33:26,440 --> 00:33:28,880
are just something
unimaginable.

579
00:33:28,960 --> 00:33:31,360
So what can kick

580
00:33:31,440 --> 00:33:34,000
a giant black hole
out of a galaxy?

581
00:33:35,280 --> 00:33:37,280
What has that kind of power?

582
00:33:37,360 --> 00:33:41,200
The answer is a clash
that wasn't evenly matched.

583
00:33:42,200 --> 00:33:46,840
The two supermassive black holes
were different sizes,

584
00:33:46,920 --> 00:33:50,520
a middleweight boxer
taking on a heavyweight.

585
00:33:52,000 --> 00:33:54,400
When humans set up a fight,
we like to make it fair

586
00:33:54,480 --> 00:33:57,120
because it's sport.
Nature doesn't care about sport.

587
00:33:57,200 --> 00:33:58,440
It's survival of the fittest.

588
00:33:58,520 --> 00:34:03,280
This is not a fair fight.
It's over before it even begins.

589
00:34:03,360 --> 00:34:06,080
One punch and it's a K-O.

590
00:34:08,120 --> 00:34:10,640
As these two black holes
are merging,

591
00:34:10,720 --> 00:34:12,480
there's one really small
black hole

592
00:34:12,560 --> 00:34:14,400
and one much bigger black hole.

593
00:34:14,480 --> 00:34:16,240
The whole system wobbles around

594
00:34:16,320 --> 00:34:18,480
and it can get more of
a gravitational wave kick

595
00:34:18,560 --> 00:34:20,280
in one direction than the other.

596
00:34:20,360 --> 00:34:23,640
And that's momentum. That's a push.
That's enough energy

597
00:34:23,720 --> 00:34:26,200
to kick the black hole out.

598
00:34:28,200 --> 00:34:30,560
The lopsided gravitational punch

599
00:34:30,640 --> 00:34:33,600
sends the merged
supermassive black hole

600
00:34:33,680 --> 00:34:35,680
on a one-way trip to oblivion.

601
00:34:37,200 --> 00:34:39,800
This tells us that
gravitational waves can be

602
00:34:39,880 --> 00:34:43,960
tremendously powerful. They can
move a supermassive black hole

603
00:34:44,040 --> 00:34:46,880
out from the center of a galaxy
and send it on its way.

604
00:34:47,920 --> 00:34:50,520
But it just carries on drifting.
There's no way to stop it.

605
00:34:50,600 --> 00:34:53,200
And who knows?
In a few million years,

606
00:34:53,280 --> 00:34:56,080
it could just drift entirely
out of its galaxy

607
00:34:56,160 --> 00:34:58,760
and go floating off
into deep space.

608
00:35:00,560 --> 00:35:04,400
In some matches, the fighters
don't even land a punch.

609
00:35:06,400 --> 00:35:09,760
Scientists spot
a supermassive black hole

610
00:35:09,840 --> 00:35:14,200
named B3 1715 425.

611
00:35:15,440 --> 00:35:17,640
This black hole is strange.

612
00:35:19,400 --> 00:35:21,280
Stripped of all its stars,

613
00:35:21,360 --> 00:35:25,720
it hurtles through empty space
at 4.5 million miles an hour.

614
00:35:25,800 --> 00:35:28,040
The first thing that draws
our attention

615
00:35:28,120 --> 00:35:31,360
is this faint trail of debris
across the sky.

616
00:35:31,440 --> 00:35:35,880
There is actually a trail leading
back to the center of the galaxy.

617
00:35:35,960 --> 00:35:38,800
It's kinda like a dump truck
that's filled with dirt

618
00:35:38,880 --> 00:35:42,000
driving down the highway,
and the dirt's flying off behind it.

619
00:35:42,080 --> 00:35:44,080
This is a naked black hole.

620
00:35:44,160 --> 00:35:48,520
The exposed supermassive black hole
has lost its stars and galaxy.

621
00:35:48,600 --> 00:35:52,680
A champion stripped of its fans
and entourage.

622
00:35:52,760 --> 00:35:55,680
So what event is powerful enough

623
00:35:55,760 --> 00:36:00,800
to strip a supermassive black hole
of its entire host galaxy?

624
00:36:00,880 --> 00:36:03,520
That has to be something
really big.

625
00:36:05,720 --> 00:36:07,720
B3 is a smallish galaxy

626
00:36:07,800 --> 00:36:10,320
and it got into a scrap
with a much bigger one.

627
00:36:10,400 --> 00:36:12,480
The stronger gravity
of the bigger galaxy

628
00:36:12,560 --> 00:36:16,320
stripped the stars away from
that black hole and shot it out.

629
00:36:17,160 --> 00:36:20,040
Typically, in the universe when
something's bigger and more massive,

630
00:36:20,120 --> 00:36:22,800
it wins.
So this is true for galaxies.

631
00:36:22,880 --> 00:36:25,160
A big galaxy
versus a little galaxy,

632
00:36:25,240 --> 00:36:27,040
put your money on the big one.

633
00:36:28,520 --> 00:36:32,280
But when two evenly-matched
heavyweights enter the ring...

634
00:36:33,760 --> 00:36:36,120
...it's time for the main event.

635
00:36:37,880 --> 00:36:39,880
A clash of the titans.

636
00:36:41,000 --> 00:36:43,040
I grew up watching boxing
with my dad,

637
00:36:43,120 --> 00:36:45,000
so I've always been a boxing fan.

638
00:36:45,080 --> 00:36:48,920
And I love a great battle.
And what's a bigger battle

639
00:36:49,000 --> 00:36:53,080
than a head-on collision between
two supermassive black holes?

640
00:36:53,160 --> 00:36:55,840
If you're a boxing fan,
this is the big one.

641
00:36:55,920 --> 00:36:59,400
We are ready.
We are on the edge of our seats.

642
00:37:00,760 --> 00:37:02,920
We've got two
supermassive black holes,

643
00:37:03,000 --> 00:37:05,720
each one is in their corner,
and they're getting ready

644
00:37:05,800 --> 00:37:07,800
for the fight of the century.

645
00:37:09,320 --> 00:37:12,400
I mean, they're just gonna
go at it, like goosh, goosh.

646
00:37:12,480 --> 00:37:15,400
I would watch that.
I'd pay-per-view that.

647
00:37:15,480 --> 00:37:18,280
It doesn't get any better
than this. These are prize-fighters

648
00:37:18,360 --> 00:37:21,240
at the top of their game,
they're trained to a T,

649
00:37:21,320 --> 00:37:24,600
they're beefed up,
they are ready to rumble.

650
00:37:28,760 --> 00:37:32,200
Welcome to the heavyweight
championship of the universe.

651
00:37:32,280 --> 00:37:35,800
Weighing in at eight billion
solar masses,

652
00:37:35,880 --> 00:37:38,720
we have The Galactic Destroyer,

653
00:37:38,800 --> 00:37:40,800
M101 star.

654
00:37:40,880 --> 00:37:46,200
And in the other corner,
at a punishing 7.8 billion suns,

655
00:37:46,280 --> 00:37:50,480
The Star Crusher,
NSC 47 star.

656
00:37:50,560 --> 00:37:54,520
They are pumped
and ready to rumble.

657
00:37:54,600 --> 00:37:57,160
So here it is. We're finally here.

658
00:37:57,240 --> 00:37:59,560
The crowd is roaring.

659
00:37:59,640 --> 00:38:03,800
The bell has rung and the fighters
are approaching each other.

660
00:38:03,880 --> 00:38:05,880
They are ready to go at it.

661
00:38:07,680 --> 00:38:10,800
Let's have a clean fight, fellas.
Touch hands

662
00:38:10,880 --> 00:38:13,840
and go back to your corners.

663
00:38:13,920 --> 00:38:17,120
Round One.
The two heavyweights circle,

664
00:38:17,200 --> 00:38:19,160
testing the other's defenses.

665
00:38:19,240 --> 00:38:21,920
The black holes are gonna do
what the boxers are gonna do.

666
00:38:22,000 --> 00:38:25,360
They're gonna circle each other
and they're gonna orbit each other

667
00:38:25,440 --> 00:38:28,320
and they're gonna
size each other up.

668
00:38:28,400 --> 00:38:31,760
Once these two supermassive
black holes are close enough,

669
00:38:31,840 --> 00:38:35,120
they're gravity inexorably is
gonna draw them together.

670
00:38:37,320 --> 00:38:40,400
As the two supermassive black holes
get closer,

671
00:38:40,480 --> 00:38:42,960
they throw a few
exploratory jabs...

672
00:38:46,160 --> 00:38:49,360
...triggering bursts of
gravitational waves

673
00:38:49,440 --> 00:38:51,920
that warp everything in their path.

674
00:38:52,000 --> 00:38:55,000
These enormous
gravitational waves

675
00:38:55,080 --> 00:38:59,520
are completely deforming the fabric
of space time around them.

676
00:38:59,600 --> 00:39:01,760
Not just a little bit, but a lot!

677
00:39:01,840 --> 00:39:06,280
It's like feeling the fighters
approach in the boxing ring

678
00:39:06,360 --> 00:39:08,960
from the next town over.

679
00:39:14,320 --> 00:39:17,640
Next, the supermassive
black holes' gravity

680
00:39:17,720 --> 00:39:19,720
throws in a couple of right hooks

681
00:39:19,800 --> 00:39:22,600
straight into the accretion disks.

682
00:39:25,360 --> 00:39:28,320
What could happen is that
they start to form like

683
00:39:28,400 --> 00:39:30,920
an angle grinder.
You'll see sparks flying

684
00:39:31,000 --> 00:39:35,040
as they try to merge and form
a new, single accretion disk.

685
00:39:35,120 --> 00:39:37,560
When those accretion disks collide,

686
00:39:37,640 --> 00:39:40,440
the whole thing is gonna light up
like the 4th of July.

687
00:39:42,560 --> 00:39:45,200
Spiraling in
at millions of miles an hour

688
00:39:45,280 --> 00:39:47,800
the heavyweight fighters get close,

689
00:39:47,880 --> 00:39:50,200
delivering punishing body blows.

690
00:39:54,280 --> 00:39:58,720
The event horizons, the surface of
the supermassive black holes,

691
00:39:58,800 --> 00:40:00,800
are about to touch.

692
00:40:02,320 --> 00:40:05,360
In their final moments,
these two supermassive black holes

693
00:40:05,440 --> 00:40:08,040
are orbiting each other
at a significant fraction

694
00:40:08,120 --> 00:40:09,440
of the speed of light,

695
00:40:09,520 --> 00:40:11,720
and their event horizons
will touch.

696
00:40:13,440 --> 00:40:16,880
And they'll eventually merge into
one new supermassive black hole.

697
00:40:18,000 --> 00:40:20,600
You might think: don't they
bump into each other

698
00:40:20,680 --> 00:40:22,360
like bowling balls? No, they don't.

699
00:40:22,440 --> 00:40:25,040
Because what we're calling
the edge of the black hole

700
00:40:25,120 --> 00:40:28,040
is actually not a thing.
That's just the surface

701
00:40:28,120 --> 00:40:31,240
around the black hole. Gravity is
so strong, nothing can come out.

702
00:40:31,320 --> 00:40:36,200
The two supermassive black holes
finally merge,

703
00:40:36,280 --> 00:40:39,680
releasing around five percent
of the mass they've gathered

704
00:40:39,760 --> 00:40:43,640
over billions of years
in an enormous burst

705
00:40:43,720 --> 00:40:46,200
of gravitational waves.

706
00:40:46,280 --> 00:40:48,600
The amount of energy
we're talking about...

707
00:40:50,400 --> 00:40:53,360
There's nothing to compare it to.
It's mind-crushing.

708
00:40:53,440 --> 00:40:56,520
There's really almost no point
in thinking about it.

709
00:40:56,600 --> 00:41:00,240
It's just not something I think
that I can wrap my head around.

710
00:41:00,320 --> 00:41:02,320
Coming from where I come from,

711
00:41:02,400 --> 00:41:04,400
you know, you don't show weakness.

712
00:41:04,480 --> 00:41:07,320
So I'm not gonna say that
the collision of two black holes

713
00:41:07,400 --> 00:41:09,560
is more powerful
than one of my punches,

714
00:41:09,640 --> 00:41:12,200
but... it's close.

715
00:41:14,160 --> 00:41:17,040
The gigantic and powerful
gravitational waves

716
00:41:17,120 --> 00:41:20,000
race out from the collision zone,

717
00:41:20,080 --> 00:41:23,240
leaving a single merged black hole.

718
00:41:24,440 --> 00:41:27,040
This supermassive black hole,
after it merges,

719
00:41:27,120 --> 00:41:30,360
permanently deforms the fabric
of space time around it.

720
00:41:30,440 --> 00:41:33,600
And this deformation travels out
at the speed of light.

721
00:41:35,320 --> 00:41:37,800
The surviving 95 percent of mass

722
00:41:37,880 --> 00:41:40,800
from the two colliding
supermassive black holes

723
00:41:40,880 --> 00:41:45,440
is now locked in a single
ultramassive black hole.

724
00:41:46,440 --> 00:41:50,480
The undisputed super heavyweight
champion of the universe.

725
00:41:50,560 --> 00:41:52,560
At least for now.

726
00:41:53,800 --> 00:41:56,040
It seems the universe is always
upping the ante.

727
00:41:56,120 --> 00:41:59,440
Could there be something even more
violent we haven't discovered yet?

728
00:41:59,520 --> 00:42:03,360
The universe keeps wanting to give us
something more violent all the time.

729
00:42:04,960 --> 00:42:07,680
Energy locked in hydrogen atoms

730
00:42:07,760 --> 00:42:09,760
formed at the birth
of the universe

731
00:42:09,840 --> 00:42:13,280
is finally released
in the violent collision

732
00:42:13,360 --> 00:42:17,480
and builds an ultramassive
black hole.

733
00:42:20,360 --> 00:42:23,920
This is one of the most beautiful
stories in our universe.

734
00:42:24,000 --> 00:42:26,560
You have the most energetic
collision,

735
00:42:26,640 --> 00:42:29,480
the most amount of energy released,
the most violent event

736
00:42:29,560 --> 00:42:34,080
can trace its origins
to the humble hydrogen atom.

737
00:42:34,160 --> 00:42:38,000
There are things constantly
being built up and then destroyed.

738
00:42:38,080 --> 00:42:42,320
It's sort of the cycle of life
in our universe

739
00:42:42,400 --> 00:42:46,600
that evolves various exotic
phenomenon

740
00:42:46,680 --> 00:42:51,160
and makes them into something
more beautiful and transformative.

741
00:42:51,240 --> 00:42:53,240
Our universe has managed to create

742
00:42:53,320 --> 00:42:56,280
both these fearsome weapons
of mass destruction,

743
00:42:56,360 --> 00:42:58,360
monster black holes,

744
00:42:58,440 --> 00:43:01,240
and also conscious life

745
00:43:01,320 --> 00:43:04,520
that can write poetry
and ponder the meaning of it all.

746
00:43:09,440 --> 00:43:11,560
So, we have our champion.

747
00:43:11,640 --> 00:43:14,560
Matter compressed
and then smashed together

748
00:43:14,640 --> 00:43:16,640
by supermassive black holes

749
00:43:16,720 --> 00:43:20,160
creates the most violent event
in the universe.

750
00:43:21,600 --> 00:43:23,480
I don't think there's a contest.

751
00:43:23,560 --> 00:43:25,680
The supermassive black hole
collisions

752
00:43:25,760 --> 00:43:30,120
are the most energetic,
just like mind-numbingly large

753
00:43:30,200 --> 00:43:32,880
amounts of energy
in these collisions.

754
00:43:35,560 --> 00:43:38,480
A merger of two
supermassive black holes

755
00:43:38,560 --> 00:43:41,760
is at the absolute top end
extreme of that

756
00:43:41,840 --> 00:43:45,560
for all possible events
in the entire universe.

757
00:43:45,640 --> 00:43:47,960
A supermassive black hole merger

758
00:43:48,040 --> 00:43:52,000
is the most violent thing that
we can observe in the universe.

759
00:43:52,080 --> 00:43:54,080
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