Through the Wormhole

There are monsters out in the cosmos that can swallow entire stars

that can destroy space itself.

Black holes.

For decades, they remained completely hidden.

But now,

scientists are venturing into their uncharted territory.

They've discovered that black holes

don't just rule the realm of stars and galaxies.

They impact all of us here on Earth,

because black holes just might be the key

to understanding the true nature of reality.

Space, time, life itself.

The secrets of the cosmos lie through the wormhole.

Take planet Earth

and squeeze it down to the size of a marble.

You'll create an object so dense

that not even light, traveling at 186,000 miles per second,

can escape its extraordinary gravitational pull.

Its name --

a black hole.

Astropsicists think that black holes might form

when giant stars run out of fuel

and collapse under their own weight.

We're not really sure. Why?

Because black holes are places

where the accepted laws of physics break down.

A few bold thinkers are now making giant strides

towards understanding what goes on inside black holes.

And the new laws of physics that emerge

have an astonishing implication --

you, me, and the world we live in

may be nothing more than an illusion.

In my hometown in Mississippi, there was a well.

It fascinated me to gaze into its murky depths

to try and see what lay at the bottom.

I would sit there, throwing pebbles into it

and trying desperately to hear a faint splash of water.

But all I got was silence.

One day, I took a dime-store toy soldier,

made a parachute for it out of an old handkerchief,

and watched it float down.

I wondered what would happen to him when he hit the bottom

or if he would just keep on falling forever

into that impenetrable blackness.

Today, theoretical physicists are drawn to black holes

like I was to that old well,

trying to understand how they really work

and what they can tell us about the universe.

It's one of those things that sounds like science fiction,

only it's better because, you know, it's real.

A black hole is the window into a world

that we don't have the concept --

we don't even have the mental architecture yet

to be able to envision properly.

You're in this strange world of strong gravity,

where there are no straight lines anymore.

You can't even see it.

That is disturbing and exciting at the same time.

The notion of a black hole

is a natural extension of the laws of gravity.

The closer you are to a massive object,

the more the pull of its gravity

slows down anything trying to escape from it.

The surface of the Earth

is 4,000 miles away from its center.

So the force of gravity up here is not very strong.

Even a kid can resist it for a second or two.

But if you could squeeze the Earth down

so that all of its mass is really close to the center,

the force of gravity would grow incredibly strong.

Nothing could move fast enough to leave its surface.

Not just a jumping boy --

even the beams of light speeding out from his shoes

would be trapped.

So, if you're trying to imagine

creating something so dense that not even light can escape,

you're trying to get a system so compact

that the speed that it takes to escape from that object

is greater than the speed of light.

Now, the speed of light is 186,000 miles per second,

so that's going really fast.

Gravity's quite weak. I think it's surprising, you know.

The whole Earth is pulling on a rocket ship,

and all it has to do is go 7 miles per second

to escape from the Earth.

And to get all the way to a black hole,

you'd have to crunch down the entire sun

to be less than a few kilometers across.

Now it would take something

traveling greater than the speed of light to escape,

so nothing can escape, and the whole object goes dark.

Christian Ott, an astrophysicist

at the California institute of Technology,

has been trying to understand

how such strange entities as black holes

might really form in the cosmos.

He studies what goes on

when giant stars run out of fuel and start to shrink,

a process comparable to the collapse

of an exhausted marathon runner.

So, sometimes you can compare a star at the prime of its life

to a runner who's just starting out real fresh,

consuming oxygen aerobically.

And it's the same with stars.

They burn hydrogen into helium slowly,

and they're getting a lot of energy

out of every single hydrogen nucleus they burn.

After they're done fusing hydrogen into helium,

they go on to more and more heavy elements,

and that fuel goes fast and fast.

So, at the end, they end up with iron,

and that's when their -- when their fuel is over,

their fuel is out.

And it's basically like a marathon runner

hitting a wall in a marathon.

But, unlike a runner

who can restore his energy with food and drink,

a dying star has no way to come back from the brink.

Ugh.

There's no more heat generation,

no more energy generation happening at its core.

So, gravity keeps on pulling in,

and when there's nothing

producing pressure to sustain it,

it will just collapse.

You get a shock wave, and the shock wave moves out.

And it actually blows up the entire star,

and that's the phenomenon we call supernova.

The death throes of giant stars

are the most dramatic events astronomers have ever witnessed.

Chinese stargazers saw one explode in 1054.

It was so bright, they could even watch it by day.

Another two blew up around 400 years ago.

These colossal explosions

leave debris fields of gas and dust

hundreds of light-years across,

still visible and still expanding today.

But what interests black-hole researchers

is not the explosion.

It's what happens at the very center of the dying star.

Modern astronomers

have never witnessed a star in our own galaxy explode.

But theoretical physics predicts that if a star is large enough,

its collapsing core

should shrink down to form a black hole.

So, imagine the balloon is a star.

And the star stays alive by burning thermonuclear fuel,

and as it does so,

you get heavier elements like the sponge

and all that energy released,

like the energy released in a bomb.

So, as a star runs out of fuel, it begins to cool.

And as it cools, it's no longer supported by all that pressure,

and so it starts to collapse under its own weight.

And it will continue to collapse until it gets so small

that now you're running up against the essure

of crushing the matter together.

And at this stage,

it's a little bigger than the size of the Earth,

and it's supported by pushing all of the electrons

in the atoms closer and closer together.

Now, if it's more massive than a couple of times the mass of the sun,

it will start to collapse even further.

And there is no form of pressure that can resist this collapse.

And it will continue to collapse down

until it forms a black hole.

But do such strange crushed corpses of stars

really exist out in the cosmos?

Could they be lurking at the center

of some of those clouds of gas and dust

thrown off in a supernova?

Christian Ott and his theoretical-astrophysicist group

at caltech

are trying to discover whether exploding stars

really do form black holes.

Well, I just generally -- you know,

I'm really excited about stars that blow up, actually.

First of all, to get a black hole,

you need low, specific angular momentum.

To have a critically spinning black hole,

you need a lot of angular momentum, so...

There are two ways to find out

whether black holes really form when stars blow up.

One is to wait for a supernova to go off in our galaxy

and use every tool of modern astronomy to pick it apart.

A galactic supernova would provide us so much information,

we wouldn't sleep for weeks.

But, unfortunately, it happens

only maybe once or twice per century.

So, Christian and his team are trying a different approach --

blowing up stars inside powerful supercomputers.

This is no easy task.

In fact, no one has pulled it off.

But Christian is on his way to being the first.

So, simulating supernovae stellar collapse

and black-hole formation

is so hard because it brings together a lot of physics.

It's general relativity for gravity.

It's fluid dynamics for the gas that collapses.

It's particle physics.