45x12 - Black Hole Apocalypse

[bunniefuu]

♪♪

JANNA LEVIN: Of all
the objects in the cosmos

Planets

Stars

Galaxies

[expl*si*n echoes]

LEVIN: None are as strange,

mysterious,

or powerful

as black holes

♪♪

NEIL DEGRASSE
TYSON: Black holes are

the most mind-blowing
things in the universe

PRIYAMVADA NATARAJAN:
They can swallow a star

completely intact

FERYAL OZEL: Black
holes have these powerful jets

that just spew matter out

LEVIN: First discovered on paper

PETER GALISON On
the back of an envelope,

some squiggles of the pen

LEVIN: the bizarre solution

to a seemingly
unsolvable equation

A mathematical enigma

LEVIN: Einstein himself

could not accept
black holes as real

People didn't even believe
for many years that they existed

Nature doesn't work that way

♪♪

LEVIN: Yet slowly, as
scientists investigate black holes

by observing the
effect they have

on their surroundings,

evidence begins to mount

ANDREA GHEZ: That is
the proof of a black hole

TYSON: Millions of
times the mass of the sun

LEVIN: Cutting-edge
discoveries show

We did it!

[applause]

LEVIN: black holes are very real

I thought it was crazy

I said, "Holy [bleep]!"

♪♪

LEVIN: But what
exactly are they?

If we could visit one,
what might we see?

With their immense power,
do black holes somehow shape

the very structure
of the universe?

Is it possible we might
not exist without them?

It's quite a journey

♪♪

LEVIN: "Black Hole Apocalypse"

Right now on "NOVA"

♪♪

LEVIN: There are apocalyptic
objects in the universe:

engines of destruction,

menacing and mysterious

Black holes

Even scientists who study them

find them astonishing

EILAT GLIKMAN: Black
holes can sort of blow your mind

I'm amazed that these
objects actually exist

LEVIN: Black holes defy
our understanding of nature

Black holes are the greatest
mystery in the universe

LEVIN: They're
completely invisible,

yet powerful beyond imagining

They can tear a star to shreds

OZEL: Black holes actually

will eat anything that
comes in their path

You really want to
avoid them at all cost

LEVIN: Black
holes even slow time

Once thought too
strange to be real

[glass shatters]

black holes shatter our
very understanding of physics

But we're learning they
may somehow be necessary

for the universe
we know to exist

They might well be the
key players in the universe

LEVIN: What are these
strange, powerful objects,

outrageous and surprising?

Where are they, and how
do they control the universe?

The search for black holes is on

And it will be a wild
ride across the cosmos

to places where everything you
think you know is challenged...

Where space and
time, even reality,

are stranger than fiction

♪♪

And we're starting that
journey at a very unlikely place:

here, at a remote location
in Washington state,

where... for the first time...

A radical new experiment
has detected black holes

It originated over 50 years ago,

when a few visionary scientists

imagine a technology that
hasn't yet been invented

♪♪

Searching for something
no one is certain can be found

The experiment
is daring and risky

Failure could mark
their lives forever

But they don't fail

Right here, in these facilities,

they make a remarkable discovery

In the early hours of
September 14, 2015,

they record a message

It looks and sounds like this

[chirp]

Just a little chirp

But that chirp is
epic, monumental

The signal traveled over a
billion light years to reach us

♪♪

It started far, far away

And what it tells us is this:

somewhere in the cosmos,
over a billion years ago,

two massive black holes circle
each other in a fatal encounter

Closer and closer they come,

swirling faster and faster,

until finally, they
slam together

[drum beats]

The black holes create
waves that spread outward

[drum beats]

Just like vibrations on a drum,

a ringing in the
fabric of space itself

The collision creates
a massive blast,

putting out 50
times as much power

as the entire visible universe

It sends out a wave not
of heat, or light, or sound,

but of gravity

This gravity wave is moving
its way through the universe

at the speed of light

♪♪

LEVIN: The wave races by stars

On the young Earth,
supercontinents are forming

Microscopic organisms
have just appeared

TYSON: Washing over one galaxy

after another, after another

LEVIN: Dinosaurs roam the Earth

The wave is still moving

LEVIN: It zooms
through clouds of dust

And then it nears
the Milky Way Galaxy

LEVIN: The Ice
Age is just beginning

We're troglodytes,
drawing in caves

LEVIN: The wave
reaches nearby stars

Albert Einstein is
in the sixth grade

The wave approaches
as close as Alpha Centauri

At midnight on
September 13, 2015,

it is as close as Saturn

Finally, over a billion years
after the black holes collide,

the wave reaches us

It strikes a pair

of revolutionary
new observatories...

The sites of the
daring experiment

[faint chirp]

This is LIGO,

the Laser Interferometer
Gravitational Wave Observatory

The experiment 50
years in the making

has finally hit the jackpot...

And opened an entirely new
way of exploring the universe

For 400 years, almost
everything we've observed in space

has come to us in some
form of electromagnetic energy

[chirp]

That little chirp is different

What hits the Earth
in September 2015

is a gravitational wave...

A squeezing and stretching
of the very fabric of space

It produced no light;

no telescope could
ever see the collision

We needed an entirely new
kind of observatory to detect it

That wave is new
and direct evidence

of one of the strangest
mysteries in our universe:

black holes

♪♪

Most of us have
heard of black holes

They're invisible, powerful

NATARAJAN: We
are talking about things

that are a billion times
the mass of the sun

LEVIN: Bizarre

GLIKMAN: A physical entity

with infinite density

No beginning, no end

LEVIN: They pull things in

And warp light

Approach one, and time
itself begins to change

NATARAJAN: The gravity is
so intense that a moving clock

will tick slower

TYSON: Time will
become so slow for you

that you will watch the
entire future of the universe

unfold before your very eyes

LEVIN: Fall in, and you'd be
squeezed as thin as a noodle

TYSON: You'll be extruded
through the fabric of space and time

like toothpaste through a tube

♪♪

LEVIN: Today, we know more
about black holes than ever before

But the more we learn, the
more mysterious they become

GHEZ: They're the most
exotic objects in the universe

We don't have the
physics to describe them

NATARAJAN: No matter
how well you understand them,

they remain unreachable
in some sense

ANNOUNCER [on film]:
Now man is about to enter

the black hole!

[machine beeping]

So black holes have a
pretty fierce reputation

And if you want a villain for a
sci-fi movie, cast a black hole

But in reality, what
exactly is a black hole?

And where do they come from?

You might think a black
hole is like this... an object

But it's not

It's a hole in the
fabric of space

A place where there is
nothing; nothing except gravity,

gravity at its most
intense and overwhelming

♪♪

So if black holes
are all about gravity...

Gravity at its most extreme...

What exactly is gravity?

♪♪

[bell rings]

[people chatting]

We're all familiar with gravity

[plates crash]: Yep, it's Friday

LEVIN: It rules our lives

But even so, for
a very long time,

how gravity actually works

was one of the
greatest mysteries

Over 300 years ago,

Isaac Newton was fascinated

with the behavior
of moving objects

Eventually he figured
out his laws of motion

They work so well,
we still use them today

MAN [on film]: Lift-off,
we have lift-off at 9:34 a m

But Newton's laws can only
describe gravity's effects,

not explain what it is

NEWTON [dramatized]: Hm

And here's where
Albert Einstein comes in

[camera clicking]

Like Newton, he thinks
about objects in motion

And he wonders
what gravity actually is

Is it a force?

Or could it be something else?

Here's what concerns Einstein

Take this apple

I can't move it
without touching it

But if I drop the apple, it
moves toward the Earth

But what if I take my hand away,

and the floor, and the basement,
and the floor below that?

Then what happens?

The apple just keeps falling

Einstein realized that gravity

had something to do with falling

Now, if I throw the apple,

it falls along a curved path

But imagine I could get the
apple moving much faster

[cannon firing]

Eventually, if I get the apple
moving really, really fast...

Say, 17,000 miles an hour...

Its curved path matches
the curve of the Earth

The apple is in
orbit, falling freely,

just like the International
Space Station

and the astronauts inside it

According to
Einstein, the apple...

And the space station,
and the astronauts...

Are all falling freely along
a curved path in space

And what makes that path curved?

The mass of the Earth

GALISON: Einstein came up
with a supremely simple concept,

and that is that space and
time is bent by the Earth,

and by the sun, and by
all the objects in the world

So according to Einstein,

the mass of every object causes
the space around it to curve

GALISON: And that
was Einstein's conception

There are no forces anymore

There's just objects
bending space-time

and other objects following
the straightest line through it

LEVIN: All objects in motion
follow the curves in space

So how does the Earth move
the apple without touching it?

The Earth curves space,

and the apple falls
freely along those curves

That, according to Einstein's
general theory of relativity,

is gravity: curved space

And that understanding
of gravity...

That an object causes the
space around it to curve...

Leads directly to black holes

But it's not Albert Einstein
who first makes the connection

between gravity and black holes

It's another scientist

MARCIA BARTUSIAK:
Karl Schwarzschild

was a German astronomer,

head of the Potsdam
Observatory in Germany

Ever since he was a teenager,
he had been calculating

complicated features
of planetary orbits

LEVIN: As Einstein unveils
his theory of gravity in 1915,

Karl Schwarzschild
is in the German army,

calculating a*tillery
trajectories in World w*r I

BARTUSIAK: And just weeks
after Einstein presented his papers,

Schwarzschild, then
on the Russian front,

quickly got a copy
and was mapping

the gravitational
field around a star

GALISON: Einstein
had gotten at it

through a series
of approximations

But Schwarzschild,
sitting on the front

with b*ll*ts and bombs flying,

calculated an exact
solution to Einstein's theory

and sent it to Einstein

Einstein was astonished

He hadn't even imagined

that you could solve
these equations exactly

LEVIN: But
Schwarzschild isn't done

In his solution to
Einstein's equations,

he discovers something Einstein
himself had not anticipated

GALISON: Schwarzschild said,

"I can calculate
this strange distance

"from a gravitating object

that represents a
kind of boundary"

LEVIN: Schwarzschild
mathematically concentrates a mass...

For example, a star...

Into a single point

Then he calculates how
that mass would bend space

and curve rays of
light passing nearby

BARTUSIAK: As he,
through his mathematics,

aimed particles of light or
matter towards this point,

there was this boundary
surrounding the point

at which the particles
would just stop

The particles disappeared

Time stopped

LEVIN: Schwarzschild
has discovered

that a concentration
of mass will warp space

to such an extreme

that it creates a
region of no return

Anything that enters
that region will be trapped,

unable to escape... even light

GALISON: It's like
those roach motels

You can check in,
but you can't check out

Once you go
across that boundary,

even if you can sail through,

there's nothing you
can do to get out,

there's nothing you
can do to signal out

It becomes this strange,
cut-off portion of space-time

LEVIN: What Karl Schwarzschild
has discovered is that any mass,

compressed into a
small enough space,

creates what we
today call a black hole

But Albert Einstein...

Whose own theory of
gravity predicts such a thing...

Cannot believe it can
happen in the real world

BARTUSIAK: Einstein didn't think

that nature would act like this

He didn't like this idea

LEVIN: Karl Schwarzschild becomes
ill and dies before he has a chance

to further investigate
his own discovery

[crowd cheering]

LEVIN: Two-and-a-half
years later, in November 1918,

World w*r I ends

The strange theoretical sphere
discovered by Karl Schwarzschild

seems destined
to be forgotten...

Nothing but a curious
historical footnote

[expl*si*n echoes]

But in the coming decades,

physicists learn
more about the atom

and about how fusing
atoms powers stars...

A process called nuclear fusion

Some begin to wonder if
something like a black hole

could actually come from a star

But not just any star...
It would have to be big

GLIKMAN: Stars
are born in litters,

and you get a distribution
of sizes and masses;

thousands of little stars

and a few big
stars, very big stars,

incredibly massive

NIA IMARA: Stars are in many
ways similar to living creatures

Like humans, they
have life cycles

LEVIN: Investigating stars' life
cycles in the 1930s, two visionaries...

Subramanyan Chandrasekhar
and Robert Oppenheimer...

Discover that the
most massive stars

end their lives very
differently from smaller ones

The life cycle of a star
really depends on its mass

The mass of a star determines
what's going to happen

after it finishes
burning its hydrogen fuel

LEVIN: All stars start out burning
hydrogen... the lightest atom...

Fusing hydrogen
atoms into helium,

working their way up
to heavier elements

Gravity wants to crush
the entire mass of the star,

but the enormous energy
released by fusion pushes outward,

preventing the
star from collapsing

IMARA: Stars are stable because
you have an outward-moving pressure

due to nuclear fusion,

and that's balancing with
the inward force of gravity

LEVIN: Smaller stars can't fuse
elements heavier than helium

But in the most massive stars,

fusion crushes heavier
and heavier atoms

all the way up to iron

Iron is such a massive element,
it has so many protons in it,

that by the time you fuse iron,

you don't get any
energy back out

LEVIN: Iron is a
dead end for stars

Fusing atoms larger than iron

doesn't release enough
energy to support the star

And without enough
energy from fusion

keeping the star inflated,

there's nothing to fight gravity

GLIKMAN: And gravity wins

And so the entire star collapses

LEVIN: Very rapidly, trillions of
tons of material come crashing down,

hit the dense core,
and bounce back out,

blowing off the outer layers of
the star in a massive expl*si*n:

[expl*si*n roars]

a supernova

The more mass, the more gravity

So if the remaining
core is massive enough,

gravity becomes unstoppable

TYSON: There's no known force

to prevent the collapse to
an infinitesimally small dot

[expl*si*n roars]

LEVIN: Gravity crushes
the stellar core down,

smaller and smaller and smaller,

until all its mass is compressed

in an infinitely small point:

a black hole

The theory makes sense,

but most physicists remain
skeptical about black holes

NATARAJAN: Einstein and
Eddington, all the sort of, you know,

pre-eminent astrophysicists
in the 1930s through 1950s,

did not believe that
they were actually real

It remained a solution,
a mathematical enigma,

for a very long time

So it took a long
time for people

to even start looking for them

LEVIN: It's not until
the 1960s that the idea

of a supernova
creating a black hole

is taken seriously

Princeton physicist
John Wheeler,

who had originally
been a skeptic,

begins to use a
name from history

for these invisible objects:

black hole

The term "black hole"
actually originates in India

The Black Hole was the name

of an infamous
prison in Calcutta

LEVIN: Still, no one has ever
detected any sign of a black hole

Then, in 1967, graduate
student Jocelyn Bell

discovers a strange,
extremely tiny dead star

that gives off
very little light...

A neutron star

The cold remains
of a stellar collapse,

the neutron star gives
astronomers more confidence

that black holes... Much
heavier dead stars...

Might also exist

[expl*si*n roars]

A half-century after
Karl Schwarzschild

mathematically
showed that black holes

were theoretically possible,

scientists have identified
a natural process

that might create them:
the death of large stars

So these giant
supernova explosions

of extremely massive stars

make black holes

NATARAJAN: Any star
that is born with a mass

that's about ten times the
mass of the sun or higher,

will end in a black hole

So our galaxy is replete
with little black holes,

which are the stellar
corpses of generations of stars

that have come and gone

LEVIN: So what are these
invisible stellar corpses like?

Imagine I'm exploring space

with some advanced
technology for interstellar travel,

so that we could
visit a black hole...

Maybe one in our own
galactic neighborhood

This particular black
hole isn't very big,

only about ten solar masses...

Meaning ten times
the mass of the sun

And like all black holes,
it has an event horizon...

A distinct edge to the darkness

That's the boundary Karl
Schwarzschild first discovered,

where gravity is so strong
that nothing can escape...

Not even light

And that's where we're going

[engine runs, machine chirps]

♪♪

♪♪

LEVIN: As we get closer, some
very strange things begin to happen

Look at the edge
of the black hole...

See how the image
of distant stars

is distorted and
smeared into a circle?

That's gravitational lensing

The black hole's extreme gravity

bends the path
of light passing by,

so that a single point
of light, like a star,

briefly appears as a ring
around the event horizon

♪♪

I'm now deep in the
black hole's gravity well,

and we're going to start
experiencing the effects

The extreme gravity
actually slows down time

relative to the Earth

From their point of view

[audio slows]: I appear
to be slowing down

But from my point of view,
time on Earth is speeding up

Now, let's say I want
to get even closer,

by taking a spacewalk

♪♪

[machines beeping and hissing]

The way the black
hole slows down time

is about to get even
more pronounced

To keep track of the changes
I'm about to experience,

I'm turning on this strobe light

It'll blink once a second

From here, I can see the shadow
of the event horizon approaching

and my light blinking normally

But watching from the ship,

the closer I move
toward the black hole,

the more slowly I appear to move

The pulses are
nearly infinitely spaced,

so it looks as though
I'm frozen in time

For me, everything
is completely normal

Even when I reach
the event horizon

If you waited long enough...

Maybe millions or
billions of years...

The ship would finally
see me disappear

And that's the last
you'd see of me

What's inside a black hole?

That's still a mystery

And even if I find out, I can
never go back and tell you

But I can say this: black holes
may be dark from the outside,

but inside, they can be bright

I can watch the
light from the galaxy

that's fallen in behind me

And that's the last
thing I'll ever see

Unfortunately, the
fun is about to end

♪♪

Now that I've crossed
the event horizon,

I'm falling toward the center,

where all of the mass of
the black hole is concentrated

And I'm beginning
to get stretched

As I fall in, the
gravitational pull at my feet

is stronger than at my head,

and my body is starting
to get pulled apart

I'll be stretched as long
and thin as a noodle...

Spaghettified

And ultimately, I'll end up

completely disintegrating
into my fundamental particles,

which are then crushed
to an infinitely small point

A singularity, where
everything we understand

about space and time breaks down

Or maybe the black hole...

Less than 40 miles
across on the outside...

Is as big as a
universe on the inside

And as I pass through,

my particles will join
the primordial soup

of a new beginning

So that's what theory tells
us we might experience

if we could travel
to a black hole

♪♪

♪♪

But how can we know for sure?

How do you investigate
something you can't even see?

There are ways to investigate

if something is
happening somewhere,

even if I can't see
that thing directly

Take Yankee Stadium:

what's happening inside there?

Is there a game going on?

I can't see the field

I can't see any players,
or baseballs, or bats

But I can definitely tell

if there's activity
around the park

It's pretty clear
something is going on

♪♪

It might seem obvious,
but whatever it is,

I can learn a lot just by
observing the happenings

around the stadium

And these do look a
lot like baseball fans

♪♪

[bat hits ball]

[crowd cheers, organ plays]

And that's the way we
investigate black holes:

by observing the effect they
have on their surroundings

But what sort of effects?

How might a black
hole reveal itself?

Starting just
before World w*r II,

two monumental discoveries

are about to radically
change astronomy

In 1931, Bell Labs
engineer Karl Jansky

picks up mysterious radio
waves emanating from deep space

Then the sky gets
even stranger...

When scientists
mount Geiger counters

on captured German rockets

and discover the cosmos
is also full of X-rays

These discoveries give
astronomers important new tools

that will revolutionize
the hunt for black holes

and dramatically
expand our vision

[machine beeping]

BARTUSIAK: What
our eyes can perceive

is a very narrow part of the
electromagnetic spectrum

LEVIN: If the
electromagnetic spectrum

were laid out along
the Brooklyn Bridge,

the portion we can
see with our eyes

would be just a few feet wide

Electromagnetic radiation

includes waves of many
different frequencies:

radio waves, microwaves,
infrared and ultraviolet light,

X-rays, and gamma rays

Radio and X-ray
astronomy open up the sky,

revealing dim or
even invisible objects

blasting out powerful
energy no one knew was there

They began to realize

that this very placid
thing that we see out there,

all this very quiet thing that
looks like nothing is happening

and the only thing that's
moving is the planets,

found out that there was
madness going out there

It was chaos out there!

LEVIN: X-rays come from the
high-energy end of the spectrum

What is creating
all this energy?

This much is certain:
whatever the source,

it is invisible to
ordinary telescopes

And it is hot

PAUL MURDIN:
X-rays come from things

which are at temperatures
of millions of degrees

Even tens of millions

LEVIN: One of the first
of these X-ray sources

to catch the attention
of astronomers

is named Cygnus X-1

Cygnus, it was in the
constellation Cygnus;

X, it was an x-ray source;

one, it was the
first one you found

LEVIN: In 1970, Paul Murdin
is a young English astronomer

trying to secure his next job

MURDIN: I was a research fellow,

I was coming to the end
of my three-year contract,

and I thought, "What can
I contribute to finding out

what these things are?"

♪♪

LEVIN: Murdin works
in a 15th-century castle

surrounded by telescopes...

The Royal Observatory

Using the largest
telescope in England,

he begins searching the area

of the constellation
Cygnus, the swan

He decides to hunt
for pairs of stars

Pairs of stars
are called binaries

They may sound exotic, but
they're not at all uncommon

Many of the stars we
see... Perhaps half...

Are actually binaries,

pairs of orbiting stars
locked together by gravity

But Murdin wonders: Is it
possible there are binaries

where only one of
the stars is visible?

MURDIN: I thought that maybe
there was a kind of a star system

in which there was a star, one
ordinary star that made light,

and then there was another
star nearby that made X-rays

LEVIN: The telltale
sign of a binary

is that the stars are
moving around each other

So Murdin begins
searching for a visible star

that shows signs of motion

Sometimes it's coming towards
you, sometimes it's coming away

Sometimes it's coming towards
you, sometimes it's coming away

LEVIN: When the star is moving
toward us, it appears more blue,

as the wavelength
of its light gets shorter

Moving away, it
appears more red,

as the wavelength
of its light gets longer

This is known as Doppler shift

After looking for color changes

in hundreds of stars
in the area of Cygnus,

Murdin spots a
possible suspect...

A visible star whose
light is shifting,

as though moving around

MURDIN: It very clearly was
a binary star, a double star

The star was moving around
and around with a period,

going around
once, every 5 6 days

LEVIN: But whatever it's
going around can't be seen

MURDIN: There was no trace in
the spectrum of the second star

There was one star there

There wasn't the
second star there

LEVIN: Murdin has a binary pair
in which only one star is visible

The second object emits X-rays,

has enough mass and gravity
to dramatically move a star,

but gives off no light

Could it be the corpse of a star

massive enough to
become a black hole?

KIP THORNE: The
crucial issue in deciding

whether Cygnus
X-1 was a black hole

was to measure the mass
of the X-ray-emitting object

LEVIN: It would have
to be very massive,

at least three times
the mass of our sun

If not, it's probably
just a neutron star...

A collapsed star that's dense,

but not heavy enough
to be a black hole

THORNE: So the observers
needed to come up with a conclusion

that the dark object,

the X-ray-emitting
object in Cygnus X-1,

was heavier, hopefully
substantially heavier,

than three solar masses

LEVIN: From his observations,
Murdin is able to make an estimate

of the mass of the
invisible partner

And the answer came out to
be six times the mass of the sun

So there was a story, then,

that Cygnus X-1 was a black hole

And the key to the argument was

that the mass of the
star you couldn't see

was more than three solar masses

When I'd finished writing it
all out, I sat back and thought,

"It's a black hole"

♪♪

LEVIN: This would be the first
actual detection of a black hole

It's a huge claim, and Murdin
will have to convince skeptics,

starting with his boss

MURDIN: The Astronomer
Royal, Sir Richard Woolley

He didn't really
go for black holes

"It's all fanciful"

It's kind of... a lot of
people in California

were talking about this

There are a lot of funny
people in California

[chuckles]: You know, a
lot of hippie-type people

LEVIN: People like
theorist Kip Thorne

So I was nervous about it

I was nervous about
the scale of the discovery

And actually so were
other people all around me

I was working with a fellow
scientist, Louise Webster

And we were modest about
the claim that we were making

because we knew what
people would think of it

And if you look at the
paper we published,

it just mentions the word
"black hole" once, right at the end

"We think this might
be a black hole"

LEVIN: The Paul Murdin-Louise
Webster paper appears in September 1971

Other astronomers agree:
It could be a black hole

But no one knows for sure

Three years later,

Kip Thorne and the noted
British physicist Stephen Hawking

make a now-famous
wager about Cygnus X-1

We made a bet as to
whether Cygnus X-1

really was a black hole or not

LEVIN: The bet is partly in jest

Both men hope it is a black hole

But Hawking, not wanting to
jinx it, bets against his own wishes

THORNE: Stephen claims that
Cygnus X-1 is not a black hole

And I claim it is a black hole

And so we signed that
bet in December 1974

And gradually, the case
that it really was a black hole

became stronger and
stronger and stronger

So in June of 1990,
Stephen broke into my office

and he thumb-printed
off on this bet,

conceded the bet in my absence

I came back from Russia and
discovered that he had conceded

LEVIN: Now, by 1990, the
evidence of Cygnus X-1's mass

may be strong enough to
settle a bet between two friends

But the original estimate wasn't
precise enough to be definitive

In order to calculate mass,

Paul Murdin had to
rely on rough estimates

of the distance to Cygnus X-1,

which varied by a factor of ten

And the question wouldn't be
answered for another 20 years,

until astronomer Mark Reid
became intrigued by the puzzle

Reid is an astronomer

at the Harvard-Smithsonian
Center for Astrophysics

when he sets out
to conclusively prove

that Cygnus X-1 is a black hole

by measuring its precise mass

But how can you measure
the mass of an invisible object?

Using laws developed

by German astronomer
Johannes Kepler

in the 1600s,

it's possible to calculate the
mass of a celestial object...

But only if you
know its distance

REID: Distance in astronomy
is absolutely fundamental

If you don't know distance,
you don't know what the object is

It could be a very
nearby firefly-like thing

It could be a very
distant, huge star,

much, much bigger than the sun

LEVIN: So to get the true,
precise mass of Cygnus X-1...

And confirm that
it is a black hole...

Reid needs to know
how far away it is

But how can he measure
the distance to a star?

The secret lies in a familiar
phenomenon: parallax

It's what our eyes and brains
use to see in three dimensions

You can put your
finger up at arm's length,

look at it, and close one eye

I'm closing my left eye

And I'm looking at my finger

relative to the wall in
the background there

And now if I open my
eye, close my right eye,

I see my finger has
appeared to move

with respect to
the original position

And that's because
our eyes are separated,

and we view from
different vantage points

LEVIN: To use parallax

to measure distance
to an object in the sky,

astronomers let the
motion of the Earth

provide the two
different vantage points

Imagine Cygnus X-1 is right here

And the Earth and
the sun are over there

Now, the Earth goes
around the sun once a year

And in the springtime, the Earth
ends up on one side of the sun,

and we observe Cygnus
X-1 along a ray path like this

Then six months later, the
Earth goes around the sun

to the other side

We get a different vantage
point from Cygnus X-1

LEVIN: Now he has
a triangle that goes

between the Earth
at its two positions

and Cygnus X-1

We know the
base of the triangle,

the diameter of Earth's orbit

And the principles
of geometry tell us

that all we need to
calculate the distance

is the size of the
angle at the top

And we measure this
very small angle here,

at the point at Cygnus X-1

And then from direct geometry,

we can calculate the
distance to Cygnus X-1

and from that infer
a very accurate mass

LEVIN: The concept is simple

But Cygnus X-1 is so far away

that the angle to be
measured is miniscule...

A tiny fraction of one degree

It's smaller than
the angle spanned

by Abraham Lincoln's nose

on a penny in San Francisco
viewed from New York

Because the angle
is so very tiny,

it can't be measured
by any one telescope

But Reid's team has a solution

We take ten radio telescopes

that are spread across
the continental U S

and to Hawaii and to St
Croix in the Virgin Islands

We use these
telescopes simultaneously,

and we synthesize in a computer

a telescope that has a
diameter of the size of the Earth

That gives you incredible
angular resolution

LEVIN: Using this technique,
Reid's team determines

that Cygnus X-1 is


REID: With the new distance we
got, the 6,000-light-year distance,

we're able to
determine that the mass

is about 15 solar masses,

easily a black hole

LEVIN: 40 years after it
was identified as a possibility,

Cygnus X-1 is now
widely accepted

as the first
confirmed black hole

MURDIN: It's an
understated paper,

and the fact that
my name was on it

and Louise Webster's was on it,

did us a lot of
good in our careers

I think as a result
of this discovery,

I got offered a permanent job

And it was a great
celebration for the family

So it worked out
very well for me...

As well as getting the
intellectual satisfaction

of solving a problem

LEVIN: So finally, after
years of speculation,

we have a real black hole

Not only that, but a black
hole that's blasting out X-rays

and has a companion star

If we could visit in my
imaginary spaceship,

what would we see?

The distance to Cygnus X-1

has been established at


And its mass is 15 solar masses,
or 15 times the mass of the sun

And Cygnus X-1 is surrounded
by an accretion disk...

A disk-shaped cloud of gas
and dust outside its event horizon,

the point of no return

As gravity pulls matter
toward the black hole,

the cloud starts rotating,

just like water being
pulled down a drain

Within that accretion disk,

particles closest to the
black hole whip around

at half the speed of light

It's like a giant particle
accelerator in space

But why does it emit X-rays?

As those particles race
around, they collide,

which heats them up
to millions of degrees

When they get that hot,
particles blast out X-rays

And it's those X-rays that
first led astronomer Paul Murdin

to investigate this black
hole nearly five decades ago

♪♪

And there's something else
about Cygnus that's different:

It has a companion star

This blue super-giant star

orbits the black hole
once every 5 6 days

It orbits so close to Cygnus X-1

that the black hole
strips material off the star

and pulls it into
the accretion disk

Some of that material
will cross the event horizon

and get swallowed
up, but not all of it

OZEL: Some of the stuff
actually comes back out

before ever entering
the black hole

Kind of like a toddler eating:

Half the pasta
ends up on the floor,

half of it may
be on the ceiling,

and some of it in the mouth

One of the most striking

and enigmatic
features of Cygnus X-1

is its enormous jets

These beams of particles
and radiation stream outward

from Cygnus's north
and south poles,

perpendicular to
the accretion disk

♪♪

There's still a lot we don't
know about these jets,

but they are tightly focused
and extremely powerful,

blasting out at nearly
the speed of light

and extending well beyond Cygnus

OZEL: When gas gets to
these high temperatures

and produces the light,

there's also a little
bit of a magnetic field

that forms around them

And we don't
understand exactly how,

but these magnetic fields

help collimate these massive
outflows from black holes,

powerful hoses if you will,
that just spew matter out

LEVIN: So that's Cygnus
X-1, if we could see it up close...

A growing, feeding
black hole with huge jets

blasting particles way
out into the universe

NATARAJAN: They're
almost these breathing,

fire-eating demons, if you will

They flicker, they have bursts;

it's a very violent
fireball, very active

LEVIN: What was once a
bizarre mathematical curiosity

has now become quite real

[expl*si*n roars]

After decades of skepticism,

scientists now accept
that burned-out corpses

of large stars

can trap light inside them,

warp space and time around them,

attract matter, and accelerate
it to mind-boggling speeds

GALISON: Black holes
seemed like such a radical idea

that we shouldn't accept it

But bit by bit, the
evidence for black holes

has gotten stronger and stronger

And we've seen
these amazing things

♪♪

LEVIN: At least 20 black holes
have been found in our galaxy,

X-ray binaries, like Cygnus X-1

And there are
probably millions more

of these massive stellar corpses

in our galaxy alone

Still, a stunning
surprise awaits

Everything astronomers think
they know about black holes...

And much of what they
believe about the universe itself...

Will be upended by
a shocking discovery

The revelations begin when
radio telescope surveys of the sky

detect mysterious hot
spots emitting radio energy

[whirring]

They were coming from
what looked like stars

LEVIN: Because these
objects resemble stars,

but were discovered
through radio signals,

astronomers name them
quasi-stellar radio sources...

Quasars

But are they stars or not?

The first step in
investigating them

is to figure out
what they're made of

To do that, astronomers analyze

the electromagnetic
energy they emit

Every element has a
unique spectral fingerprint

For example, carbon

Helium

Hydrogen

These lines reveal the
chemical make-up of a star

But the spectrum of a quasar

turns out to be incomprehensible

BARTUSIAK: They looked
at it and it was gibberish

It didn't look like there
were any emissions

from elements that they knew

LEVIN: What are they missing?

There has to be a clue somewhere

Finally, in 1963, Caltech
astronomer Maarten Schmidt

finds it hiding in plain sight

Buried in the quasar's spectrum
is the fingerprint of hydrogen

He noticed something familiar,
but it was in the wrong place

The fingerprints of hydrogen
had been shifted way off to the red

LEVIN: It was hard to spot because
the spectral lines of hydrogen

were radically shifted toward
the lower-frequency end

of the spectrum

And that could
only mean one thing

♪♪

The quasar is moving away
from us at fantastic speed

But astronomers have
never before seen light shifted

to such an extreme

[barking, audio slowing down]

Like a familiar sound
shifting too low to understand,

the light from quasars
has shifted to such a degree

that hydrogen is unrecognizable

This extreme amount of shift

means quasars are racing
away from us at blinding speeds

The reason?

It's the legacy of an event

that occurred almost 14
billion years ago: the Big Bang

[expl*si*n roars]

The beginning of our universe

And ever since, the
universe has been expanding,

carrying with it all the objects
it contains, including quasars

GLIKMAN: No one had ever seen
anything moving away at that high speed

This made this object
the furthest-away thing

that had ever been seen,

which meant the thing
itself had to be so luminous,

and you had to account for that

BARTUSIAK: Two billion light
years away, putting out the energy

of a trillion suns each second

What could possibly create that?

No one had any idea what
could be powering these things

Where could all of
this energy come from?

If you work out
through calculations,

it can't be chemical energy

[expl*si*n roars]

They knew it couldn't
be nuclear energy

[expl*si*n roars]

LEVIN: There's no way
a quasar could be a star

No amount of nuclear fusion

could produce that
much star power

The only engine
that could possibly

put out that much
energy is gravity

LEVIN: Gravity

In everyday life, we can
overcome gravity easily

But when concentrated to
an extreme by a black hole,

gravity is
overwhelmingly powerful

A handful of scientists
start wondering:

Could quasars perhaps be
powered by gravity engines?

What if the energy
blasting out from quasars

is coming from bright accretion
disks around black holes?

NATARAJAN: To
produce that kind of energy,

that kind of brightness,

it has to involve a black hole

LEVIN: But not
just any black hole

THORNE: Whatever was the
source of the emission from a quasar

had to be massive

How massive?

Well, millions or billions of
times heavier than the sun

LEVIN: Millions or billions
of times heavier than the sun

Cygnus X-1 is only 15
times the mass of the sun

The black holes powering quasars

are an entirely different
category of black hole:

supermassives

♪♪

And they seem to be located
in the centers of galaxies

But what about our own galaxy?

Could there be any supermassive
black holes closer to home?

The center, where any
supermassive would be found,

lies in the direction of the
constellation Sagittarius,

the Archer

Now, Sagittarius isn't
just any constellation

It's in the direction
of the center

of our own Milky Way Galaxy

But since we live
inside the Milky Way,

we can't see the galaxy the
way a space traveler would

But I can use my trusted
imaginary star machine

to show us the
galaxy from the outside

Our home is a spiral galaxy,
hundreds of billions of stars,

drawn together
into a gigantic disk

It's wide, about 100,000
light years across

But it's relatively thin,

only about 1,000
light years thick

And the whole
spiral slowly rotates

Our solar system is here

And here, 26,000 light
years from the Earth,

is the center, which we see
in the direction of Sagittarius

In this dense center,
there are millions of stars,

and lots and lots
of dust and gas

So that's the view of our
galaxy from the outside,

thanks to my
imaginary technology

But since we live
inside the Milky Way,

when we look towards the center,

we're looking through
much of our own galaxy,

which means it appears to us

as a band of stars and dust
across the sky... a milky way

♪♪

Deep inside this
band of stars and dust,

could a supermassive
black hole be lurking?

GHEZ: The data
that we're getting now

LEVIN: In the 1990s, astronomers
grow determined to solve the mystery,

to peer through
the murky Milky Way

and learn what, if
anything, is at its center

One of them is Andrea Ghez

GHEZ: One in 20

LEVIN: Ghez takes
on a daunting challenge

She will try to
track individual stars

orbiting the center
of the galaxy

GHEZ: The essence of this
experiment comes from watching

stars orbit the
center of the galaxy

So you want to find the stars

that are as close to the
center of the galaxy as possible

Which means that
I want to get access

to the largest telescope I
can possibly get my hands on

LEVIN: And that
means coming here

♪♪

The summit of Mauna
Kea, a dormant volcano

almost 14,000 feet above
the beaches of Hawaii

High altitude and low humidity

make this the ideal
place for astronomy

♪♪

The instrument Ghez uses is
Mauna Kea's Keck Observatory,

one of the largest in the world

But despite its size, Keck
has the same problem

as all telescopes on Earth:

atmospheric distortion

GHEZ: Think about
looking at a pebble

at the bottom of a river

The river is moving very quickly

and your view of
that pebble is distorted

LEVIN: Like a river,

the Earth's atmosphere
is constantly changing,

bending light like
a funhouse mirror

To compensate for this,
Keck pioneers the scientific use

of a declassified
military technology

called adaptive optics

First, they shine a
laser into the sky,

creating an
artificial guide star

The turbulent atmosphere
distorts the guide star,

but the computer knows
what it should look like,

and adjusts the telescope
mirror accordingly

GHEZ: So if you look at yourself
in a circus funhouse mirror,

you look completely distorted

And the goal of the
adaptive optics system

is to introduce a second mirror
that's the exact opposite shape

and make you look flat again

LEVIN: Buried deep
inside the telescope,

the deformable
mirror changes shape

up to 2,000 times a second

to reverse the
atmosphere's distortion

GHEZ: And it has allowed
us to take the sharpest images

ever obtained of the
center of the galaxy

LEVIN: The sharpness of
those images allows Ghez

to make out individual
stars near the center...

A huge advance in astronomy

She begins recording
their positions in 1995

GHEZ: And every year since then,

we've taken an image...
Just take a picture

LEVIN: Putting those
annual snapshots together

creates a time-lapse
movie of stellar orbits

And what those movies
reveal is astounding

♪♪

The stars are whipping around
the center of the Milky Way

at phenomenal speeds

These things are moving
at several thousand,

up to 10,000
kilometers, per second,

or ten million miles per hour

They're, they're really hauling

LEVIN: To go that fast,
the stars must be orbiting

something extremely massive

GHEZ: The mass that we infer

is four million times
the mass of the sun

What could be four million
times the mass of the sun

yet be completely invisible?

That is the proof
of a black hole

LEVIN: And not
just any black hole...

A supermassive,
silent and sleeping,

right in the center
of our own galaxy

In fact, this is the
best evidence to date

that we have for the existence
of supermassive black holes,

not only in the center
of our own galaxy,

but anywhere in the universe

♪♪

A supermassive black hole

four million times
the mass of the sun,

in the very center of our
own Milky Way galaxy

From a cosmic perspective,
it's right next door

And it raises a
profound question

There are billions
of galaxies out there

If ours has a supermassive
black hole at its center,

and if quasars are
found at the centers

of their galaxies,

what about the others?

♪♪

Are there black holes at
the centers of galaxies?

If they are, how
common are they?

We simply didn't know

LEVIN: Could astronomers
ever hope to find what lurks

at the centers
of other galaxies,

millions of light years away,
as Ghez did in our Milky Way?

[engine ignites loudly]

It would take another
innovation in astronomy

to make that possible

ANNOUNCER: And lift-off of
the space shuttle Discovery,

with the Hubble Space Telescope,
our window on the universe

LEVIN: When the Hubble Space
Telescope starts delivering clear images

of distant galaxies,

a team of astronomers
gets to work

They become
known as "the Nukers"

because their focus
is galactic nuclei,

the centers of galaxies

One of them is Tod Lauer

Step one, we take a
picture of the galaxy

with the Hubble Space Telescope

It shows us where the
stars in the galaxy are

It tells us its structure
in exquisite resolution

♪♪

LEVIN: The key to finding
supermassive black holes

is to learn how fast the
stars in the galaxy are moving

Galaxies outside our
own are much too far away

to measure the speed
of individual stars

But by analyzing the way
light is shifted from blue to red

at different points
in the galaxy,

astronomers can put together
an average speed of stars

orbiting the center

It's accurate enough to
create a replica in a computer

The second step, where
the real work begins,

is to try to model
the observations

And we actually do that by
building models of galaxies

in the computer

LEVIN: It's known as
Schwarzschild's method,

developed by Princeton
astronomer Martin Schwarzschild,

son of Karl Schwarzschild,

whose mathematics
first described

the possibility of black holes

LAUER: Martin
Schwarzschild's trick was,

he would actually build
up a model of the galaxy

that not only had
where the mass was,

but it also had how
the stars were moving

♪♪

LEVIN: For each
galaxy they investigate,

the Nukers painstakingly build
a computer model and then,

using trial and error,

adjust the parameters
of mass and velocity...

Trying to make the model
match the original observations

they got from the Hubble

LAUER: And we say,
"Let's try a star here,

"let's try one over here

"Let's have it go
around this way

Let's have this one
go around that way"

And we do this thousands
and thousands of times

until we build up a library

of how stars can
orbit in this galaxy

Success is when
observations of the model

match the observations taken
with the Hubble Space Telescope

LEVIN: But that doesn't happen

The models are missing something

We try it again and
again and again,

all with no black
hole yet, and we say,

"Gee, we really can't get
the observations explained

by the model"

LEVIN: Only when they add
an enormous invisible mass

at the galaxy's center

does the model match
the Hubble observations

LAUER: Almost
always we have to put in

a black hole at the center

We can't match the observations

without a black
hole in the model

♪♪

LEVIN: Of roughly three dozen
galaxies that the Nukers investigate,

virtually all of them require
a supermassive black hole

And since then, other
observations have made us

even more certain

that supermassives
and galaxies go together

Every galaxy we've
looked for one,

we have found a supermassive
black hole in its center

LEVIN: It's a
stunning revelation

Supermassives...

Once an entirely unexpected
category of black holes...

May be common,

not only at the
center of our galaxy,

but of all galaxies

Take galaxy M31,

also known as the
Great Andromeda Galaxy

It's two-and-a-half
million light years away

On a clear night, you
can see it from Earth

But even with the
Hubble Space Telescope,

we can't make out
precise details of its center

Still, we're pretty sure

there's something extremely
massive hiding there

♪♪

What if we could
take a closer look?

What if we could visit
a galaxy far, far away?

♪♪

As we enter the outer
part of Andromeda,

we're still too far away to
see what's lurking at the center

But we can make out

a dense cluster
of stars in the core,

and that could be a sign

that there's a giant
black hole nearby

♪♪

Billions of years ago, it
would have been surrounded

by gas and stars and
other small black holes

The black hole may
have powered a quasar,

feeding mad, and blasting
out blinding radiation

Over hundreds of
millions of years,

it would have consumed

all the available gas
and the closest stars

♪♪

[screen beeping]

♪♪

These days it's relatively quiet

But it has some
distinctive features

we've never seen before

First, it's colossal

If it were dropped
in our solar system,

Mercury, Venus, Earth, and Mars

would all be trapped
inside the event horizon

That's big, but it's nothing
compared to the sheer mass:


the mass of the sun

And the destruction
won't end there

Jupiter won't last long

The gravitational field
of the supermassive

will grab hold and
swallow it whole

Eventually, Saturn
will suffer the same fate

The outer planets might
survive, but in cold and dark orbits

♪♪

This black hole rotates rapidly,

distorting and dragging
the fabric of space-time

Like all black holes,

the event horizon is
completely featureless

Remember, there's nothing there

It's just a boundary
that conceals the interior

But the accretion
disk can tell us a lot

about what's going on

That's the fiery ring of gas
and dust around the black hole

♪♪

Imagine if we could release a
swarm of autonomous robots

to explore the accretion disk

♪♪

The disk is spinning
at an incredible speed...

As much as half
the speed of light

If Jupiter moved that fast,

it would complete its
entire orbit in a few hours

The region around the
black hole is a cosmic tornado

Now our swarm is
caught in the whirlwind, too

They're like tracers
dropped into the storm

to map the movement

The middle robot
can send us images

It's following the
leader like a race car

speeding around the track

From here, the extreme
warping of space-time

around the black hole

plays crazy tricks on our eyes

It looks like there's
one accretion disk

whipping around the equator,

and another arcing
over and under the poles

But that's an illusion

The black hole's extreme
gravity bends the path of light

emitted behind the black hole,

and makes it look
like the accretion disk

is both above and below

There's actually
nothing around the poles

It's just the passing light rays

That's gravitational
lensing again

Drawing much closer
to the event horizon,

the gravitational lensing
would become so extreme

that one of my robots
could look straight ahead

and eventually see its own back,

the light forever trapped
in an eternal circle

So that's our tour of the
supermassive black hole

at the center of the
Andromeda Galaxy

Pretty amazing

Also amazing: nothing
in the mathematics

led scientists to imagine that
black holes could get that big

♪♪

As strange as they are,

ordinary stellar-mass
black holes

were at least
predicted by theory

Supermassives are
a complete surprise

♪♪

For the stellar-mass
black holes,

people thought about them
from a theoretical perspective

And then we found
them observationally

The supermassive black
holes, the story has been inverted

We actually found evidence
of them observationally first

And now we're
working on the theory

of, how did these
things come into being?

♪♪

LEVIN: We already know
that stars can collapse

to create ordinary black holes

But supermassives are bigger
by many orders of magnitude

Cygnus X-1 is 15
times as big as our sun

The supermassive at the
center of our Milky Way

is four million times
as big as our sun

The one in the Andromeda galaxy

is 100 million times
as big as our sun

And it's not the
biggest... Not even close

There are supermassives
ten, even 20 billion times

the mass of our sun

How is it possible to make
such gigantic black holes?

Could supermassives have
come from collapsed stars?

That seems very unlikely...
We don't know any stars

billions of times
bigger than the sun

TYSON: We know about black
holes you might get from a dying star

They have several
times the mass of the sun

contained within them

But millions of times
the mass of the sun

If that's the case, a dying star
cannot have possibly made it

LEVIN: So do these
supermassives...

Millions or even billions of
times heavier than the sun...

Somehow just grow, packing
it on like voracious giants?

The wild thing about
black holes is that they feed

They're constantly
devouring anything that comes

within their
sphere of influence,

so they grow

LEVIN: But how
exactly do they grow?

What do they eat, and
where do they find it?

NATARAJAN: We believe
that black holes grow

by accretion of gas

And the way this works is that
you have a lot of gas around

in the center of a galaxy,

and this gas would then
assemble and form an accretion disk

LEVIN: The accretion disk is
made up of hydrogen, helium,

and other elements
in a gaseous form

The immense gravity
of the black hole

pulls the gas in toward it

As it swirls around,

it orbits closer and
closer to the black hole,

and the feeding begins

NATARAJAN: The stuff in the inner
regions would get slowly pulled in,

sped up, will reach
the event horizon,

and then that's it

LEVIN: Whatever gas crosses
the event horizon disappears forever

The black hole has
absorbed that material

So it actually adds to
the mass of the black hole

LEVIN: So this is one
way a black hole can grow:

gradually nibbling gas and dust

But it's not the only way

Cygnus X-1 has been
slowly stripping material

off a nearby star...

A process that will likely go on

for thousands or
millions of years

But what if a black hole
could rip an entire star apart

in just a matter of
years, or even weeks?

That would be a
very violent event

And a team of space
explorers is on the lookout

This is the Operations Control
Center for a space telescope

I have you five-by-five

We show beginning
of track at 0330

LEVIN: the Chandra
X-Ray Observatory

[people talking on radio]

LEVIN: Orbiting up to


Chandra takes
high-resolution images

of objects that emit X-rays

This is one: a short-lived,
extremely violent event

called a transient,

which fascinates
James Guillochon

GUILLOCHON: Supernovae, the
destruction of planets by their host stars

Yeah, I'm just fascinated with
destroying things for science

LEVIN: James is investigating a
mystery discovered by a colleague,

Dacheng Lin

This blur on James's screen

is actually a massive
sudden burst of X-ray energy,

caught by accident

GUILLOCHON: This little smudge
popped up in the background of this image

And given its great distance,

it's actually
tremendously bright

LEVIN: Could it be a black hole
caught in the act of being born

in the violent collapse of
a huge star, a supernova?

[expl*si*n roars]

Perhaps

But the intense radiation
released by supernova

would only linger
for a few months

♪♪

So how long has this mystery
object been blasting out X-rays?

To find out, they look at images
of that same part of the sky

taken at earlier dates











No X-rays detected

But the X-rays are there
just three months later, in July

And the powerful, bright
signal has continued

for more than ten years,

from July 2005 to the present,

far too long to be a supernova

So what could it be?

A black hole that's not feeding
is quiet and completely dark

It won't show up
on any telescope

But a black hole that
is feeding is different

When it feeds, it
blasts out X-rays

So could this be a black hole

that's suddenly begun
devouring something big?

TYSON: What effect will this
have on anything that comes near?

What would it do to a star
that wanders too close?

Well, it will flay a
star layer by layer,

ultimately devouring

the entire star

♪♪

LEVIN: Unlike Cygnus
X-1, this is no mere nibbling

This is a ten-year
feeding frenzy,

a massive black hole
devouring an entire star

in a cosmic blink of an eye

It's the result of a
chance collision...

When an unlucky
star wanders too close,

and the black hole's extreme
gravity actually rips it apart

GUILLOCHON: The
gravity from the black hole

will progressively get
stronger and stronger

as the star gets near

And at that point, the
star will begin to deform

LEVIN: It's called
tidal disruption

It's similar to the way
our moon's gravity

easily moves all
the world's oceans

The tides caused by a black hole

would be billions
of times stronger

and much more violent

NATARAJAN: You have these events

where a star could be
ripped apart by the black hole

So you would see
sort of a plume of light

from the last gasp of
the material in the star

LEVIN: But there is a chance
for some part of the star to escape,

as James illustrates

As the star is elongated by
the black hole's tidal forces,

it will essentially be
feeding the black hole

at the same time as half
of it is trying to escape

So everything above
this point, approximately,

will have the chance
of leaving the galaxy

It's moving that rapidly

And everything below this point

will fall back onto
the black hole

and eventually be consumed by it

LEVIN: So this is another way
for a black hole to gain weight

Unlike the slow steady
nibbling of Cygnus X-1,

this black hole is devouring
most of an entire star

in one gulp

But whether a black
hole feeds suddenly,

by swallowing half a star,

or steadily, through accretion,

astronomers still face a problem
when they try to understand

how supermassives got so big...

The timing problem

The trouble begins with the
very oldest supermassives:

quasars, those very
bright, very distant,

and ancient objects

first discovered
in the early 1960s

The conundrum was when we
started finding these quasars,

very bright quasars, very
early on in the universe

DALE KOCEVSKI: They're
giving off so much energy

that they have to have very
massive supermassive black holes

at their center

LEVIN: But quasars
are extremely far away,

which means that they're
part of the very early universe,

which began nearly


NATARAJAN: Bright quasars,


after the Big Bang

A fraction of today's age

LEVIN: And, they're enormous

NATARAJAN: So billion-solar-mass
black holes, these behemoths,

had to be in place
when the universe

was about 550 million years old

Now you have a problem

Because you have to
grow something really big,

really fast

And you are bumping up
against sort of physical limits

♪♪

LEVIN: Whether a
black hole is nibbling

or gulping down its meal,

it turns out that accretion...
How black holes feed...

Has a speed limit

Named after English
astronomer Arthur Eddington,

the Eddington Limit
will not allow a black hole

to feed too fast

because of the
light blasting out

from its own accretion disk

♪♪

GLIKMAN: Light has a pressure

So photons can impart
a force on something

We see this in winds from
stars: Light is pushing out gas

So there's a limit to how
fast you can feed a black hole

before its own luminosity
quenches its own growth

LEVIN: So given this speed limit,
how did early supermassives...

Quasars... get so big, so fast?

Could there be a way to
bypass the speed limit entirely?

NATARAJAN: The
problem is still time itself

How do you grow them

to a billion times
the mass of the sun?

What are the conditions that
you need for that kind of growth?

LEVIN: Some scientists are
now asking: What if there's a way

to create a black hole

that's already much
more massive from birth,

giving it a head start?

NATARAJAN: If there
was a physical mechanism

that would allow you to
make a black hole seed

which was much more
massive from the get-go,

then the timing crunch is
not as much of an issue,

and the growing
problem is not as acute

LEVIN: The answer, some believe,

is to create a black hole
directly from a cloud of gas:

a scenario called
direct collapse

It starts with gas clouds
made of hydrogen, helium,

and other elements...

The same raw materials
from which stars are born

The denser clouds
will start to collapse

under their own gravity

And as they collapse,
parts that are more dense

will collapse more quickly

And so what happens
is, the cloud fragments

LEVIN: Those fragments
continue collapsing

until the hydrogen atoms
within them begin to merge

Nuclear fusion begins,
and stars are created

But what if a giant gas cloud
collapsed without making stars?

We realized that there are
a set of physical conditions

that would allow you to
form a very large gas disk

prior to the
formation of any stars

So this gas disk
starts getting unstable

That would allow the mass
to sort of flow into the center

very, very rapidly

and make a very
massive black hole

♪♪

LEVIN: It's something
we've all seen in nature,

from tornadoes to bathtubs...

A vortex

But on a supermassive scale

If you're in a bathtub
and you pull the plug out

and you see the water
flowing in a vortex,

very fast down to the center,

that's exactly what happens

LEVIN: Direct
collapse might be a way

to create very large black
holes early in the universe

from enormous gas clouds,

completely skipping
the star stage

Because they would be
so large already at birth,

these direct-collapse
black holes

would have a head start,
helping them to quickly grow

into the enormous young
supermassives we see

in the distant universe

NATARAJAN: You could potentially
have these direct-collapse black holes

So black holes
whose original masses,

seed masses, the initial masses,

are about 10,000 to
maybe 100,000 times

the mass of the sun,

and that they form from
the get-go with that mass

♪♪

LEVIN: Direct collapse may explain
how enormous early supermassives

got their start

But there's another fundamental
question about supermassives

What is their role
in the universe?

Is their existence just
a matter of chance?

Or are they connected
in some larger way

to the very structure
of the cosmos?

Supermassive black
holes don't exist in isolation

They seem to live in
partnership with galaxies

♪♪

Collections of
millions, billions,

or even trillions of stars
bound together by gravity,

galaxies are the fundamental
building blocks of our universe

So are the supermassive
black holes at their centers

somehow fundamental
to their very existence?

TYSON: We now just
assume every galaxy,

even ones we
have yet to confirm,

will have a supermassive
black hole in their center

KOCEVSKI: It could be that
instead of simply being oddities,

that they are a key
component to galaxies,

a key component to the universe

We've come in a very
short time to realize

that they likely inhabit the
centers of all the galaxies

And that can really only happen

if there's some
symbiotic relationship

between the
evolution of a galaxy

and the supermassive
black hole in its core

LEVIN: What could
that relationship be?

One intriguing
clue relates to size

CHUNG-PEI MA: The
bigger the galaxy is,

the more massive the
black hole appears to be

So these black
holes at the center

seem to know about their
larger-scale environment

LEVIN: So which comes first,

the galaxy or the
supermassive black hole?

It's not that simple

It appears they
somehow grow in tandem

GHEZ: It's hard for one to
form first and affect the other

So today we think that
whatever formed one

had to form the other as a
by-product of that process

And that there has to be
some feedback mechanism

between the black
hole and the galaxy

that keeps the growth
of the two in lock sync

♪♪

LEVIN: The way galaxies
grow is by forming new stars

from clouds of hydrogen gas

Gas is essentially the
fuel for star formation,

just like gas is
the fuel for our cars

And so if you run out of
gas, you run out of new stars

LEVIN: So are
supermassive black holes

somehow interfering
with star formation?

GLIKMAN: When a
black hole is growing,

a tremendous amount of
energy is being liberated

and sent out into the galaxy

And so we think that some of
that energy goes to warm up gas

And gas that's too warm
will not form stars anymore

♪♪

LEVIN: The heat produced
by a growing black hole

makes it impossible
for stars to form nearby

♪♪

GLIKMAN: And so one
way that a growing black hole

can influence its host galaxy

is by quenching
the star formation

LEVIN: In effect, the
growth of the supermassive

determines whether or not its
host galaxy grows or stagnates

GALISON: They have
a kind of eating phase,

and then a quiescent phase

So they seem to be involved

with the formation of
the galaxy in that way,

and then stabilizing of
the galaxy at the same time

LEVIN: So these
mysterious supermassives

may actually control the
building of the universe...

Not so much by their size,

but by the way the energy
they generate shapes galaxies

By mass, if you count up all
the black holes in the universe,

the tiny ones as well as
the supermassive ones,

the ultra-massive ones,

black holes are nothing

However, energetically, how
much power the galaxy gets

and at what time
as it assembles,

seems to be dictated
by the central black hole

So they might well be the
key players in the universe

♪♪

LEVIN: In the next two
years, NASA plans to launch

the James Webb Space Telescope

Humanity's most
powerful telescope ever,

the James Webb is
designed to look in the infrared,

allowing it to see farther
back in time than Hubble,

getting a look at the
first stars and galaxies

that formed after the Big Bang

Hopes are high that the
James Webb Space Telescope

will help solve many of
the remaining mysteries

about the earliest
supermassive black holes

TYSON: The James Webb Space
Telescope is tuned specifically

to observe the early universe
when galaxies were being born

That could give us
deeper understanding

of how you end up with a
supermassive black hole

in your galaxy to begin with

GHEZ: Technology
is moving really fast,

and as a result, we have
really fundamental new views

of the universe

I think we are really living
in a golden era of astronomy

♪♪

LEVIN: And the James
Webb Space Telescope

isn't the only new development
that promises to solve

some of the mysteries
around black holes

♪♪

WOMAN: I believe
have infrared components

LEVIN: A group of scientists

led by Shep Doeleman

is now attempting
the impossible:

to take a picture
of a black hole

DOELEMAN: It's interesting
that we can say something

about the accretion flow
near the black hole at all

OZEL: And if some of this
linear behavior survives,

maybe we'll have a
way of interpreting it

LEVIN: The project is called
the Event Horizon Telescope

DOELEMAN: The basic goal
of the Event Horizon Telescope

is really to see the unseeable

It's to bring into focus

something that science has
told us for many, many years

is precisely something
we can't observe...

The black hole

LEVIN: Their primary
target is Sagittarius A♪,

the supermassive in the
center of our Milky Way Galaxy

They're using a global
network of radio telescopes

DOELEMAN: We need good
weather at eight different telescopes

all around the world,

and that is a tall order

LEVIN: But if black
holes are invisible,

what exactly do they
hope to photograph?

What we are trying to
photograph really is the shadow

So as this gas
around the black hole

swirls inwards and actually
hits the event horizon,

it leaves a silhouette,

a very well defined shadow
on the surrounding light

So really it should
look like a donut,

with its very well defined hole

And that's the
picture that we're after

If I convert that
into frequencies,

I get two-pi-square there

LEVIN: The team has
conducted their first observing run

and is processing the data now

Okay, you're saying the velocity

LEVIN: It's hoped that
these new technologies

will give us an unprecedented
view of black holes

in our universe

But there is one new technology

that is already
delivering results

And that brings us
back here, to LIGO,

a key player in the
black hole drama,

to an idea that took root
way ahead of its time:

gravitational waves

With general relativity,
his theory of gravity,

Einstein predicts that
when an object moves,

it can create ripples
in space and time...

An actual squeezing and
stretching of space itself

One of the holy grails
of 20th-century physics

was to detect these
gravitational waves

WEISS: That was not easy to do

with general relativity,

because all the effects
that you could think of

were infinitesimally small

Very, very difficult to measure

LEVIN: The thinking was,

if gravitational waves
could be measured,

it would confirm
Einstein's prediction

And there could be
an added benefit...

It might also prove the
existence of black holes

and help solve the mystery
of how supermassives grow

But how to detect
gravitational waves?

In 1970, the problem
caught the attention

of a young experimental
physicist, Rai Weiss

[classical music playing]

Rai had the perfect background
to hunt for gravitational waves

For decades, he'd been working
with more familiar waves...

Sound waves

WEISS: We were immigrants,

we were German Jews

And a lot of our friends were
very, very interested in music

[music continues]

LEVIN: Rai devoted himself

to coaxing every
subtle nuance he could

out of recorded music

WEISS: Those records
had a terrible problem

When the music was
loud, it sounded wonderful

When the music was
real quiet and slow,

what you heard was this

[imitating hissing] like that

A hissing noise

And that was so annoying

LEVIN: The lessons he learns

trying to eliminate
noise in recordings

will pay off later,

when Rai turns his attention

to detecting gravitational waves

WEISS: You have to understand

how a gravitational
wave does its dirty work

LEVIN: As a physics problem,

gravitational waves are
not unlike sound waves

Let's suppose the wave
comes from something

that is in some way
moving and oscillating

[vibrating]

LEVIN: A sound wave
compresses and expands air

A gravitational wave
compresses and expands space

and everything in it

WEISS: If a wave
came through the Earth,

it would cause space

to expand momentarily
and then contract again

It keeps doing
it, so it's this thing

that goes blip, blip,
blip, right along like that

LEVIN: So how to measure

the extremely tiny expansion
and contraction of space?

Rai's idea was to use light

Send a beam of light

from one place to another,

and measure the time
it takes to get there

[clicks]

That's how the exact distance
to the moon was calculated:

bouncing a laser
beam from the Earth

off a mirror left behind
by Apollo 11 astronauts

♪♪

From the duration
of the round trip,

scientists could
determine the distance

♪♪

Rai came up with
an ingenious design

for an instrument that
uses lasers and mirrors

to detect the faint expansions
and contractions of space

that would be caused
by a gravitational wave

It's called a laser
interferometer

It works by firing a
laser into a splitter

Half of the light
continues straight ahead

towards one mirror,

while the other half is
sent towards another mirror

The distant mirrors bounce
the light beams back,

where they rejoin
at a photo detector

If the distances the two beams
travel are exactly the same,

the system is designed so the
two beams cancel each other out;

the detector sees nothing

You've set the trap to
measure the gravitational wave

Now comes the gravitational
wave that's coming,

let's say, at this structure

LEVIN: If a gravitational
wave passes through,

it briefly changes
the length of the arms

The light beams no longer
arrive back at the same time

to cancel each other out

A gravitational wave hits

Light appears at the detector

The trap has sprung

That's the basic idea

It's a very straightforward
measurement

LEVIN: A clever idea,
and simple in principle

But the devil...

And the Nobel Prize...

Lie in the details

The difference in length
between the two arms

would be tiny beyond imagining

How tiny?

Well, take the size of an atom

It's less than that

Go down by a factor of 100,000

That's the nucleus of an atom

It's less than that

It was 100 times below that

So we're talking about
really itsy-bitsy, teeny-weeny

I thought it was crazy

I think everybody's
initial reaction to the idea

was, this is going
to be impossible

LEVIN: In 1973, Kip Thorne
puts his skepticism on the record

in a classic textbook,

doubting it will ever work

But Kip has never
heard Rai Weiss

explain his plan in detail

And when he does

We spent the whole night talking

And so I said, "No, no,
no, it's very possible"

And within no time at all, 20
minutes, maybe half an hour,

Kip was solidly understanding
this thing and he says, "Yup!"

And I ate crow the
rest of my career,

because once I had talked
with Ray about it in detail,

I decided I would
spend a large fraction

of the rest of my career

helping the experimenters

LEVIN: But it
will take 40 years,

and enormous sums of money,

to bring Rai and
Kip's vision to reality

Getting LIGO funded

was extremely controversial

Hundreds of millions of dollars

to detect a signal that
had never been seen before

There were many
people who feared

that LIGO would suck
the money out of the room

And so there was
a lot of controversy

What everybody
could agree on was,

this was extremely difficult

LEVIN: With such a
sensitive instrument,

one of the biggest challenges

is Rai Weiss's old
hi-fi nemesis: noise

Ground motion

The seismic motion of the Earth

Acoustics' noise,

sounds [thunder crashing]

Everything would
tend to move that mirror

LEVIN: Turns out, even the
emptiness of a total vacuum

creates a potentially
crippling problem

At subatomic distances,

the weird randomness
of the quantum world

causes a ruckus in the mirrors

THORNE: This quantum noise
is due to quantum fluctuations

These mirrors are doing what
an electron does inside an atom;

they're jiggling around

♪♪

LEVIN: Exquisite sensitivity,

extreme vacuum,

hundreds of thousands
of electronic circuits

LIGO is one of the most
complex instruments

in the history of science

And as a final means of
eliminating false signals,

they build not one,

but two complete installations:

one in Washington state
and another in Louisiana

And so the LIGO
designers did it right

They designed more
than one detector,

separated from one
another by great distances,

so that if you detect something
in one and not in the other,

then, you know, go back
and check your electronics

Check to see if it
was April Fools' Day

and somebody didn't
just tweak the knobs

♪♪

LEVIN: Early fall 2015

Both locations are operating,

but the first official science
run has not yet begun

They're still testing

In the early hours of
Sunday, September 14, 2015,

a scientist in Louisiana
makes a fateful decision

♪♪

Robert Schofield has
been working all weekend

doing final calibrations

All righty, let's
take a spectrum

LEVIN: He has one last test

SCHOFIELD: So let's see where
this computer's getting its power

LEVIN: But it's late, and the
equipment is not cooperating

SCHOFIELD: It was about


and we still had about
another hour of work to do

And we were, like, "Yeah,
things aren't working so well,

"and I'm really tired

Let's not do this last
hour or so of work"

LEVIN: They call it a night

And 40 minutes later,

in the silence
of their inactivity,

they open the door to history

♪♪

[faint chirp]

A powerful gravitational wave
rumbles through both detectors,

Louisiana and Washington

Had Robert Schofield worked


with the instruments
in test mode,

a signal that had been on
its way for 1 3 billion years

would never have been recorded

SCHOFIELD: I like to say,

you know, one of my
biggest contributions to LIGO

has been my laziness that day

[indistinct conversations]

I got an email from
somebody here saying,

"Hey, look, look at
this place on the web"

[chirps]

I looked at that and
I said, "Holy [bleep]!"

♪♪

[chirps]

THORNE: It was so strong

that you could see
it by eye in the data

It was too good to be true

LEVIN: But it was true

In fact it was loud,
and surprisingly clear

And it just sang at you

There it was, standing out

LEVIN: The signal
lasted less than a second,

but in that briefest of moments

it delivered a cosmically
profound message

more than a billion
years in the making,

proving the existence
of black holes

THORNE: So what
we saw in the signal

involved oscillations of the
mirrors that were slow at first,

became faster and
faster and faster

And this was precisely
the kind of behavior

that you would expect
from gravitational waves

caused by two black holes
going around each other,

spiraling together

LEVIN: Two massive black holes,

one 29 times the
mass of the sun,

the other 36 times
the mass of the sun,

whipping around each other
hundreds of times a second,

finally completing their act of
mutual destruction by merging

Creating a single, larger
black hole of 62 solar masses

The violent merger
converts some of the mass

into an apocalyptic
release of energy

beyond anything
ever before witnessed

THORNE: The
collision, in effect,

creates a very... a veritable
storm in the fabric or the shape

of space and time,

as though you had
taken three suns,

you had annihilated
them completely,

converted it into
gravitational waves

The power was 50 times
higher than the output power

of all the stars in the
universe put together...

In a fraction of a second

But the most powerful expl*si*n

that humans have ever
had any evidence for

with the exception
of the Big Bang

♪♪

LEVIN: Since that very first
signal in September 2015,

LIGO has detected several
more collisions of black holes

In October 2017, Rai
Weiss, Kip Thorne,

and LIGO's former
director Barry Barisch

received the Nobel Prize

The LIGO discoveries prove
that black holes can merge...

One way they can
grow bigger quickly

More and more evidence of
these merging black holes tells us

there are a lot of these
stellar black holes around,

that they can find each
other and, and merge

LEVIN: And the discovery
opened an entirely new way

of observing the universe

♪♪

[chirp]

We always thought of astronomy

as an observational field

where we are
looking at radiation

We are seeing things

But this is not radiation

This is something
much more fundamental

These are sort of fundamental
tremors in space-time itself

We can now hear the universe

♪♪

LEVIN: For the first time,

astronomers have simultaneously
seen and heard a cosmic event

♪♪

In August 2017, LIGO
detected gravitational waves

from a collision of
two neutron stars

Black holes are empty space,

but neutron stars
are dense dead stars

that can crash together
and light up the skies

♪♪

When telescopes and
satellites around the globe

pointed in the
direction of the sound,

the world saw fireworks

in an expl*sive
collision and afterglow

Possibly, the collision
resulted in the creation

of a new black hole

But unless we observe
the formation of a black hole,

there is much we will never know

Because so much
about black holes

is irretrievably
out of our reach,

we can never know
where they came from,

what's inside, or their history

♪♪

[expl*si*n roars]

But we can imagine their future

The number of black holes
in the universe is increasing

And they're getting bigger

Stars collapse,

black holes feed and merge,

new ones form

Could it be that one day,

everything will
end up inside them

and they will rule the universe?

♪♪

Untold trillions upon trillions
of years after this happens,

and the last bits of matter
cross their event horizons,

black holes themselves
may radiate away

and vanish from this reality

♪♪

Their mysteries are many,
and we're just starting

to unlock the secrets of
these strange, powerful places

But one thing is certain

Black holes will
continue to intrigue us,

tantalize us,

and challenge both our
science and our imaginations

♪♪