All language subtitles for How the Universe Works - 7X04 How Black Holes Made Us

Black holes...

Long considered
the bullies of the cosmos,

but are they really so bad?

Black holes aren't violent.
They are elegant.

They're incredibly
powerful objects,

but they're beautifully simple.

Simple but unpredictable.

Black holes rip planets
to shreds,

but they also
give birth to stars.

Black holes are like
the ultimate

recycling-trash-bin combination.

They build galaxies

and may have lit up
the dark infant universe.

It's one of the biggest
changes that happened.

Someone switched the lights on
and transforms our universe.

They come in all sizes,

from microscopic
to ultramassive,

controlling the fate
of everything around them.

The story of the
universe and how it's arranged

is the story of black holes.

Black holes are the master
architects of the universe,

and without them,
we would not exist.

Black holes...

We're riveted
by their destructive power.

Black holes are dangerous.

Black holes are hazards.

Black holes are not friendly
for their environments.

There's just no good end
to anything

that falls into a black hole.

Perhaps one of the most
frightening objects

in the universe.

But what exactly are
these scary objects?

Black holes are created
when you get enough matter

in a small region of space.

This happens
when a massive star dies

and collapses in on itself...

...a supernova.

A black hole is the ultimate
consequence of gravity.

It's an object
that has so much mass

crushed into such a small space
that its escape velocity

becomes greater
than the speed of light.

They are a one-way street.

You go in.

Nothing escapes, not even light.

But do black holes
really deserve their bad rap?

In some ways,
I think we set up black holes

to be more villains
than they actually are.

Black holes suffer a bit
of a P.R. Problem.

I think they're a lot more
menacing in science fiction

and popular media
than they really are.

There are trillions of
galaxies in the known universe.

And most of them have
a supermassive black hole

at their center.

These monsters are millions
of times the mass of our sun.

Their immense gravity
can send stars flying.

They're instrumental
in choreographing

the dance of stars
in their vicinity.

Supermassive
black holes shoot out torrents

of lethal radiation
and violent cosmic winds

and gobble up anything
that comes close.

Now scientists are beginning
to realize these cosmic giants

may also have a creative side.

Most people think of black holes

as being like giant
vacuum cleaners in space,

and basically everything
falls into them,

but that's not
actually the case.

They're better thought of
as the engines of cosmic change.

Although black holes
are the end states of stars,

they can actually influence
the formation of stars,

as well, in a bunch
of different ways.

A galaxy's job is to make stars,

but uncontrolled star growth
isn't healthy.

Too many stars can drain
a galaxy's gas supply.

Black holes are very important.

It appears that galaxy evolution
is tied to black-hole evolution.

We don't know exactly how yet,

but the marriage
appears certain.

One idea is that
supermassive black holes

act as cosmic
control mechanisms.

Black holes can act like
a thermostat in your house.

If your house gets too hot,

the thermostat will kick on
the air conditioner,

and if it gets too cold,
it'll kick on the heater.

Black holes do the same things
for galaxies.

Supermassive black holes
regulate star formation

by pulling gas in and shooting
it back out into the galaxy.

When these black holes
are consuming matter,

they're drawing matter
into themselves,

but they're also
spewing stuff out.

Basically, black holes eat
like little babies...

Very sloppily,

so a lot of what they eat
comes flying back out again.

They eat stars.
They eat planets.

But most often,
they eat giant clouds of gas.

The black hole drags
gas and dust

into an accretion disk
around it.

This disk spins faster
and faster.

Magnetic energy builds up.

With the accretion disk
swirling around the black hole,

there are also magnetic fields
that are going on.

The material is moving
so rapidly

that the magnetic field
sort of winds up, coils up,

and forms a vortex
like a tornado.

Astronomers call them jets.

These jets propagate outward
like freight trains

plowing through the galaxy

over hundreds and thousands
of light-years.

These are like death rays.

The jets disrupt
the star-forming gas clouds,

limiting excess star formation
in the main body of the galaxy,

but in the very outer reaches
of the galaxy,

they can spark star birth.

Things are more gentle
out there.

You're not as close
to the energetic heart,

so stars, planets, and life
can form out there

partially because of
the material

that the black hole
has moved out there.

So black holes can
have outsize influence

on the regions
that they inhabit.

Right around them, they can
prevent the formation of stars

whereas,
on very, very large scales,

they can actually instigate
the formation of stars.

2018... black holes
hit the front page.

Scientists discovered
black holes gobbling up gas

so fast that they seem to be
outgrowing their host galaxies.

It naturally makes
the question come up...

How big can a black hole get?

Now we have the answer.

They can reach size triple-XL,

becoming ultramassive
black holes.

Ultramassive
black holes are so cool

because it's just mind-boggling

that black holes so large
can exist.

Ultramassive
black holes are very rare

and typically have masses
of more than 10 billion times

the mass of the sun.

10 billion solar masses...

That's a 10
followed by nine zeros.

Ultramassive black holes
are real beasts.

The black hole at the center
of our galaxy

is 4 million solar masses.

Imagine black holes
that are 2,500 times bigger.

That's what
we're talking about here.

An ultramassive
black hole this big

would be as wide
as the solar system...

...and weigh as much as
all the stars in the milky way.

They're inside galaxies
that aren't a whole lot bigger.

That really surprised the hell
out of everybody.

And in 2018, scientists discover

a 20-billion-solar-mass
ultramassive black hole

growing faster
than any other black hole.

This ravenous behemoth devours
the mass of our sun

every two days.

These big black holes
are really good

at gobbling up other things.

They'll literally eat anything.

They're monsters
of the universe.

This kind of voracious eating

can have
devastating consequences.

It blasts so much energy
and turbulence into the galaxy

that stars no longer form,

and the bigger the black hole,
the faster the galaxy dies.

The primary thing these
ultramassive black holes

do to galaxies is they shut down
all star formation,

and so in that sense,
they kind of kill galaxies.

And so these things

could even wipe out
their host galaxies.

Ultramassive black holes are
a problem for scientists, too.

They might be
the fastest eaters,

but that doesn't explain
how they got so large.

With these ultramassive
black holes,

these black holes that are
10s of billions of times

more massive than our sun,
you can't just grow them

from the slow accretion
of gas over time.

There's just not enough gas,

and there's just
not enough time.

It gives us
a new mystery to solve.

How do you make black holes
that are just that big?

There's not a clear answer
so far

as to how these ultramassive
black holes were formed.

People wonder if there's
some other mechanism

by which you could make
black holes.

A mechanism so violent
it also throws

supermassive black holes
clean out of galaxies.

We now know that
ultramassive black holes

billions of times
the mass of the sun exist,

but we have no idea
how they got so big.

We've detected
lightweight stellar-mass

black holes colliding.

They merged into a new
larger black hole

and generated
huge amounts of energy.

But what about
supermassive black holes?

When galaxies merge,

their central
supermassive black holes

will fall to the center
of the newly formed galaxy.

Could these
supermassive black holes

caught up in galactic mergers

combine to form
an ultramassive black hole?

In 2017, the Hubble
space telescope spotted

something strange in
a distant galaxy called 3c186.

It detected
an incredibly bright spot

thousands of light-years
from the galaxy center.

Scientists suspect
it's a quasar.

A quasar is an incredibly
bright, active galactic nucleus

that's powered by
a supermassive black hole.

We regularly spot
black-hole-powered quasars,

but always at the centers
of galaxies,

until now.

When we actually got
this data from Hubble,

we were absolutely stunned
to discover

that the quasar that
we've long known to exist

in the center of this galaxy
wasn't actually at the center.

This black hole is offset
from the center of the galaxy

by about 35,000 light-years.

That's really weird.

What is an incredibly
rare and bizarre event

to find a quasar,
a supermassive black hole,

that is not
at the center of the galaxy.

When scientists looked closer,

they discovered that the quasar
is hurtling through space

away from the center
of the galaxy.

Now, mind you,
this is a black hole

with the mass of about
a billion times the sun,

and it's screaming away
at 4 million miles an hour.

This black hole,

which was probably originally
in the galaxy center,

has somehow been shot out
at high velocity

by some incredibly
violent event.

It's hard to imagine
what kind of event

would pump that much energy
into such a huge object

to shoot it away
from the center of a galaxy.

Who kicked it out, how, and why?

Scientists have an idea.

3c186 may be the remnant
of a galaxy merger.

The merged galaxies'
supermassive black holes

circle each other,

sending out blasts of energy in
the form of gravitational waves.

Gravitational waves
are all around us.

They're ripples in the fabric
of space-time.

Every time mass moves,

gravitational waves
are produced,

so if I wave my hand,
I am making gravitational waves.

A hand produces
imperceptible waves.

When objects as huge

as supermassive black holes
collide,

the energy released
as gravitational waves

is phenomenal.

Scientists think
these black holes

might have been different sizes.

It's possible that
if one of the black holes

is really massive

and the other one
isn't quite as massive,

that when they spiral around
and merge,

they send out gravitational
waves in an asymmetric way.

This asymmetry has
a catastrophic effect.

As the two black holes collide
and merge,

they shoot out a huge blast
of gravitational waves,

but only in one direction.

This blast of energy kicks
the newly combined black hole

out of the galactic center.

Think of a shotgun recoil,
but supersized.

And there's so much
energy in that emission

that it acts like a rocket,

and it actually pushes
the merged black hole away.

It would have been one of
the most energetic events

ever witnessed.

They're so energetic,

they are literally shaking
the fabric of space.

We didn't witness
the actual collision,

but 3c186 could be evidence

that supermassive black holes
can collide and merge,

building even larger
black holes.

This would be a mechanism
by which you would create,

ultimately,
an ultramassive black hole.

As for the ejected black hole,

the gravitational recoil sent it

on a one-way ride to oblivion.

So gravitational waves kicked
this supermassive black hole

and sent it
flying through space.

In 20 million years, it's
expected to exit its galaxy.

The ejected
supermassive black hole

may eventually hit
another galaxy

and merge with
its supermassive black hole.

These largest of black holes

seem to throw their weight
around,

bullying galaxies
and other black holes.

Now researchers have discovered
a vampire black hole

that's draining the lifeblood
of its neighbor.

Ultramassive black holes

seem to destroy their galaxies,

while supermassive black holes
seem to regulate star formation.

But are all supermassive
black holes forces for good?

Hundreds of galaxies
surround the milky way,

large and small,

but most of
the largest galaxies are red.

This is not a good omen.

In space, red means danger.

If you have active
ongoing star birth,

then you have massive stars,

and massive stars
tend to be blue,

but they don't live very long,
and they blow up.

Once you stop star formation,
after some amount of time,

the galaxy turns red.

The only stars left alive

are small, long-lived red stars
called red dwarfs.

A red galaxy with only
red dwarfs

is a dying galaxy.

The Sloan digital sky survey
found an entire population

of these luminous red galaxies

that were no longer
forming stars

that were dead.

One galaxy around 340 million
light-years away stood out.

It was named after a Japanese
anime character, Akira.

It's very red.

All the stars in it are red,
and that means they're old,

so we know that Akira
has not had

any active star formation
in a long time.

The Akira galaxy
doesn't form stars

because it doesn't have
the cool, calm gas

needed to build them.

Something is heating the gas,
making it turbulent.

One of the ways in which
a black hole can drive

the evolution of the galaxy
in which it resides

is by simply powering a wind.

These are winds that are
literally driven by light.

When a black hole feeds,

it drags gas
into an accretion disk.

The disk heats up
and gives off light radiation.

The radiation pressure from the
accretion disk around this black hole

couples to
the ambient gas and dust

and pushes it outwards
at very high velocity.

These winds that are driven
out by the black hole

essentially warm up the gas
in the galaxy,

preventing further
star formation.

However, whatever's
fueling the black hole in Akira

is a mystery.

Here's a weird thing...
There is an outflow,

a wind coming out
of this galaxy,

and that means
there's gas feeding

that black hole in the center,
and it's blowing it out.

Where is this gas coming from?

Ah, it's stealing it.

It has a small companion galaxy,
which is nicknamed Tetsuo,

and that has gas in it.

Akira's supermassive
black hole pulls gas from Tetsuo

and drags it
into the center of the galaxy.

The black hole is taking the gas
from this companion galaxy,

and that's what's falling
around the black hole

and creating this wind,

so Akira is actually
sort of a dead galaxy,

but it's being rejuvenated
by its companion, Tetsuo.

Like a cosmic vampire,

Akira's supermassive black hole
feeds off Tetsuo.

The black hole drags gas and
dust into its accretion disk,

which spins faster and faster.

When these particles
are rubbing against each other,

well, that generates friction.

Friction may not seem like
that big of a deal.

I mean, you can rub
your hands together

on a cold day to get warm,

but imagine rubbing
your hands together

at very nearly
the speed of light.

How much friction is
that gonna generate?

It's gonna make a lot of heat.

Over a million degrees
Fahrenheit...

So hot the accretion disk
lights up.

Its temperature goes up,
and he starts emitting light.

It becomes incredibly bright.

Even though there's a black hole
in the core,

its surroundings
are intensely bright.

This heats up
the surrounding gas,

generating a hot wind,

which extends thousands of
light-years from the black hole.

And those winds carry
with them a lot of energy,

and that energy, if it couples
to the gas in the galaxy,

can blow that gas out.

They inject energy
into nearby gas clouds

and heat them up and prevent
them from forming stars.

Stars don't form...
The galaxy dies.

These dying galaxies
are called red geysers.

Scientists think around 10%
of the red galaxies

we see around us
died this way...

...heated up
by this galactic warming.

We think that the source
of some of this galactic warming

is in the growth of supermassive
black holes themselves

because when you grow
a supermassive black hole,

you must liberate
an enormous amount of energy.

You can't grow a black hole
for free,

and that energy gets dumped back
into the ambient surroundings

and keeps this halo of gas hot.

It prevents it from cooling
and forming stars.

Sagittarius a-star,

the supermassive black hole
at the heart of our galaxy,

the milky way,
could turn into a red geyser.

If you were suddenly to dump
an enormous amount of gas

onto Sagittarius a-star,

you could have what is
effectively a red-geyser effect,

a very powerful wind
driven by all of this energy.

Star formation would stop,

and our milky way would become
another dying red galaxy.

Now new research suggests
that Sagittarius a-star

has already affected
the inner region of our galaxy,

not by killing stars,

but by transforming planets from
gas giants into super-earths.

At the center of our galaxy

lies a supermassive black hole,
Sagittarius a-star.

We think it's calm,
dormant, safe.

Relative to other
supermassive black holes

in the universe,
ours is relatively quiet.

It's been active in the past,

and it could flare up
in the future.

It could be active
tomorrow, for all we know.

All you need to do
to light it up

is start dumping some gas on it,

and there is almost certainly
a giant cloud of gas

that we don't currently know of

on its way
to the center of our galaxy,

and it will find itself one day
in the vicinity

of our supermassive black hole,

and it will start to light up
like a Christmas tree.

In February of 2018,
scientists at Harvard

simulated Sagittarius a-star
during a feeding frenzy

to understand the impact of an
active supermassive black hole

on its local environment.

They found that,

as Sagittarius a-star
gobbled up gas and dust,

it belched out bright flares
of high-energy radiation,

which radically affected the
region around the black hole.

The environment near
the center of a galaxy

that has an actively
feeding black hole

is the worst place
in the universe.

You've got
this tremendous object

which is heating up this gas
to millions of degrees.

This is no place
that you want to be.

The model revealed
what would happen

to any planets
in the line of fire.

Think about being in the way

of one of these
black-hole burps.

All of a sudden, there's
a tremendous wind of radiation

that comes through
your solar system.

That could actually strip away
the outer layers of gas

of a planet like Neptune.

The high-energy radiation

from the supermassive
black holes

would hit the gas planets
and heat up their atmospheres.

Maybe this would actually
strip away the outer layers,

leaving the solid material
in the middle.

You could actually turn
a gas-giant planet

into a terrestrial solid planet

all because you're close
to a black hole.

This radiation strips away
the gas, leaving the core,

now a new rocky planet

but a giant one...
A super-earth.

Normally, you think
of rocky planets

being about the size
of the earth,

but this would be a way of
making so called super-earths.

Super-earths are
one of the most common

type of planets
discovered in our galaxy.

It's possible
that any super-earths

close to Sagittarius a-star

were created
by these blasts of energy.

Away from our galactic center,

a much smaller
stellar-mass black hole

is also radically transforming
its environment.

January 2017...

Researchers discover
something strange

in a cloud of gas called W44.

W44 is a supernova remnant.

It's the debris... the expanding
cloud from a star that blew up.

The explosive
shock wave from a supernova

pushes gas and dust
out from the dead star,

forming a huge nebula.

We see a lot of these.

I mean, they're catastrophic,
amazing, incredible events,

but as far as they go,

this one appears to be
pretty standard,

except for one weird thing.

In the heart of it,

there's something
very mysterious going on.

There seems to be something
shooting out

of the very center
of this explosion.

A thin protrusion
trillions of miles long

streams out from the cloud.

It's moving at
over 60 miles a second

against the flow of the galaxy.

It's very strange
that it's moving backwards

against the rotation
of the milky way.

When you see a giant,
giant, very massive cloud of gas

that is moving counter to
the rotation of the milky way,

it needed to be like
a bullet from a gun

fired against a headwind
in the opposite direction.

So what is that gun?

You know, what fired
that bullet of gas?

The tip of
the bullet cloud is expanding

at 75 miles a second.

That's 270,000 miles an hour,

over 150 times faster
than a bullet.

What in the cosmos has the power
to accelerate gas

to such high speed?

Could that actually be
a black hole

moving very, very quickly?

Researchers think
a stellar-mass black hole

hidden in the bullet cloud

is powering
the movement of the gas.

Gravity from this black hole
is incredibly strong,

and so it will
latch onto this gas cloud

as it passes through it,

and it can completely disrupt
the motions of this cloud.

This is a very
interesting stream of gas

that's somehow connected
to a black hole,

and we don't know
whether it's there

because the black hole
is moving through the gas,

and it's creating a wake,

or whether somehow
this black hole

is spitting out a stream
of material in some way.

The black hole
could be dragging gas

into an accretion disk
around it.

The gas heats up and expands,

giving the initial supernova
explosion, W44, an extra kick,

driving this bullet-like cloud
out in front of it.

Or the black hole could be
racing away from the nebula,

dragging the gas behind it
like a wake.

Ultramassive, supermassive,
and stellar-mass black holes

all play a role
in shaping the cosmos,

but there may be
another type of black hole

even more dangerous
than the rest...

A microscopic black hole.

We have so far
detected triple-XL

ultramassive black holes,
large supermassive black holes,

medium-sized
intermediate black holes,

and small stellar-mass
black holes.

Now scientists have another
to add to the roster...

Microscopic black holes.

We know there are
supermassive black holes

at the centers of galaxies.

We know there are
star-sized black holes

from the deaths of stars.

That's what we know for sure.

It's possible there are
much smaller black holes,

microscopically
small black holes.

Microscopic black holes
are virtually invisible

to the naked eye,

but magnified, they look like
regular stellar-mass black holes

the definition of a black hole

is an object
that has so much mass

crushed into such a small space
that its escape velocity

becomes greater
than the speed of light,

so it could be something
the size of a star,

the size of a galaxy.

It could also be
the mass of a planet.

If you could crush
the earth down far enough,

it could become a black hole.

The density of a black hole

is something
that the human brain

really doesn't wrap itself
around very easily.

When you think about something
the size of the earth,

how small would the earth
have to be to be a black hole?

And the answer is something
on the order of a marble.

So think about taking
the entire earth

and compressing it down
to the size of just a marble.

So where do these strange
little black holes come from?

These very small black holes
can only be formed

in the exotic conditions of
the incredibly early universe.

Our universe might get flooded
with these small black holes

that simply persist
to the present day.

It's the only time
in the history of the universe

where you could take
a small amount of matter

and crush it down so tightly

that it could become
a black hole.

Those conditions don't exist
anymore,

so if these things exist,
they would be primordial.

They would be as old
as the universe itself.

These primordial
black holes may be ancient,

but they still pack a punch.

When it comes to black holes,

the smaller black holes
are actually more dangerous

because their mass
is concentrated

into such a small volume.

In fact, a tiny
black hole would be lethal.

If it were to pass
in front of me, very quickly,

almost instantly, I would be
ripped apart head to toe,

stretched into a long, thin
stream of fundamental particles

that would then wind their way
into the black hole.

It would actively feast on me
in a matter of seconds.

But if Paul
or an interstellar robotic probe

visited a supermassive
black hole

or even an ultramassive
black hole,

they wouldn't be immediately
ripped to shreds.

One of the most fun questions
about black holes is,

how close could you get
to a black hole

before the gravity
would rip you apart?

And that actually depends
on the volume of the black hole.

If the black hole is very large,
you could get very, very close.

The more massive they are,

the slightly softer they are
in how they tear things apart,

so a supermassive black hole,
actually...

You can cross within
the event horizon

and not really notice it.

You're never gonna get back out,

but you won't necessarily
be stretched to your death

while you cross inside.

So a probe could visit
a supermassive black hole

and not be destroyed...

...until it crossed
the event horizon

and traveled deep inside.

Then it would be torn to pieces.

But microscopic black holes
are currently just a theory.

Microscopic
black holes have been the focus

for some researchers
for many years,

but currently
there's no evidence

to support their existence.

Microscopic primordial
black holes may or may not

have been around
since the big bang.

Now scientists have discovered
supermassive black holes

from the very early universe.

They're shedding light on one of
the most mysterious eras,

the cosmic dark ages.

Black holes don't just
shape the universe now.

They've been shaping it
from almost the dawn of time.

Scientists think black holes
may have triggered

one of the universe's
greatest transformations...

Turning from dark and foggy
to transparent and light.

At the beginning of time,

the universe was a tiny ball
of super-hot energy...

The big bang.

Shortly after our big bang,
our universe was shining bright

because it was full of
hot, glowing gas.

Then it cooled off and entered
the so-called dark ages

until eventually something
lit it up again.

It's one of the biggest changes
that happened in our universe.

Someone switched the lights on
and transformed the universe.

During the dark ages,

the universe was blanketed
in a thick fog.

Then something lit it up

in a process called
reionization.

We still don't really know
for sure

whether reionization
was mainly caused by young stars

or whether it was mainly
black holes that ate stuff

and spewed out
a bunch of radiation.

Then in December of 2017,

researchers in Chile scan
a region of space so far away

it takes light
13 billion years to reach us.

They spot an object
from just 690 million years

after the big bang

when the universe was only 5%
of its current age.

It's called quasar J1342+0928.

The thing that's so amazing
about this farthest quasar

is we may actually have seen
the boundary of these dark ages.

This particular supermassive
black hole/quasar tells us

something about the formation
of the early universe.

It's thought that
quasars helped drag the universe

out of the dark ages.

They gobbled up
so much hydrogen gas

and belched out jets of energy

and cleared up the fog.

Those jets could have actually
put so much energy

into the universe
that it made it clear again.

We may actually be seeing
the moment

where something punches through
this boundary of the dark ages.

Pockets
of reionization opened up

throughout the early universe.

They came in different sizes,
depending on what created them.

While our universe
was being reionized,

there was kind of, like,
all these holes

that kept growing.

If the reionization was made by
a large number of little stars,

you would have
many, many small holes,

much like a sponge,

whereas if you had
a small number

of monster black holes doing it,

you'd have a lot of big holes,
like in Swiss cheese.

At present, we can't
measure the ionized pockets

to determine if
it was stars or black holes

that lit up the early universe.

Perhaps it was both...

Black holes and stars
working together.

The more we investigate
black holes,

the more we learn
about their role

as architects of the universe.

I think scientists
of my generation are very lucky

to be able to be at the
beginning of this revolution.

We used to portray
black holes as monsters.

Now we know that, without them,

the universe would be
a very different place.

They made life possible.

Without black holes,
we probably wouldn't exist.

We're discovering

just how black holes
shaped the universe,

but the more we learn,
the more questions they pose.

I've spent my career
studying black holes,

and I want to spend the rest of
my career studying black holes,

and I guarantee you that,
at the end of my career,

on the day I retire,
I will probably have

more questions about black holes
than I do today.

This is an incredibly
exciting time

for black-hole science.

Who knows what
we're gonna discover?