Original subtitles

A superannuated giant star finally explodes.

This is a massive event that entails a rapid shrinking

of the dead star's core.

In the end, it almost seems that nothing is left

but concentrated gravitational force, a black hole.

It's pole is so powerful, it swallows up even light.

But if neither emits nor reflects light,

how can a black hole be found?

In 2011, Japanese imaging equipment

aboard the International Space Station

detected the moment when a black hole gulped down a star

as large as our Sun.

This is the image.

On the left, a picture taken on March 21, 2011.

On the right, the same area eight days later.

A small blue dot has appeared,

an intense burst of x-rays.

At the moment when a star is engulfed by a black hole,

its temperature exceeds 10 million degrees Celsius,

and it emits intense x-rays.

The blue dot in the image we just saw

represents that final burst of x-rays

as the star was engulfed by the black hole.

Such an event is one way in which the presence

of a black hole can be inferred.

But for a long time, scientists debated

the very existence of black holes.

Were there really objects in space

that could swallow up light itself?

The opposition was, much of it was motivated

by the view that this object is so bizarre,

so strange, that it's unphysical.

And it's not likely that the true laws

of physics will be predict such a thing.

Now, at the leading edge of astrophysics,

the cosmic front, scientists are busy determining

the exact shapes and properties of black holes.

How far have scientists succeeded

in locating these invisible phenomena

and revealing their amazing forms?

This is a quest to find and evaluate objects

of endless fascination, black holes.

A jet of water spouting 140 meters into the air.

This is Switzerland's second largest city, Geneva.

In 2008, underneath this city,

and extending into neighboring France,

a gigantic experimental facility,

27 kilometers in circumference was built.

That's 50 times the circumference of The Colosseum.

It was operated by CERN,

the European Organization for Nuclear Research

with the participation of some 20 countries

including also, the United States and Japan.

This is where experiments took place

to define a black hole by creating one.

Pipes were laid 100 meters underground.

Protons were accelerated through it at high speed.

When we get up to top energy,

the protons are going 99.9999991

times the speed of light.

So very, very, very close to the speed of light.

And then we're, down the way,

we're gonna collide them inside the big experiments

and see what we can see.

When protons traveling

at such blinding speed collide,

they are smashed into infinitesimal bits.

And at the moment of impact,

it was thought microscopic black holes would be produced.

Producing black holes is certainly a possibility.

In many ways, a very exciting possibility.

However, lawsuits were filed

in Germany and the United States,

demanding an injunction against

such an allegedly dangerous experiment.

The lawsuits argued that no matter how small the black hole,

once it started swallowing matter,

it would become an unstoppable force.

Eventually, so the claim went,

our entire planet would be sucked in.

The black hole.

To trace its conceptual origins,

we must go back 3 1/2 centuries

to the time of Isaac Newton.

Based on his Law of Universal Gravitation,

scientists of his era came up

with a fascinating hypothesis.

The more massive a celestial body is,

the stronger its gravity.

The lighter it is, the weaker its gravity.

So its mass determines the speed necessary

to escape from its gravitational pull.

For example, the speed necessary

to escape Earth's gravity is 11 kilometers per second.

A more massive object would require

a faster escape velocity.

Light travels at a speed of 300,000 kilometers per second.

So, the more massive a star is,

the harder it must be for its own light to escape.

Theoretically, there could exist in the universe

an object so massive, that not even light

could escape its gravitational pull.

If we could not see this star shine,

it would be effectively a black star.

That was our first conception

of what we now call a black hole.

Black holes were studied more rigorously starting

about a century ago.

That was thanks to another

of the great geniuses of physics, Albert Einstein.

It was Einstein who predicted the curvature of space-time.

This was his famous General Theory of Relativity.

Gravitational forces distort the very fabric

of the space-time continuum.

The more gravitationally powerful a star is,

the more it distorts space-time.

So that light, instead of following a straight path, curves.

A prediction confirmed by direct observation.

German physicist Karl Schwarzschild

was the first to provide exact solutions

to certain equations in Einstein's theory.

Equations that describe the effects

of gravity on space-time.

Shrink a celestial object in size but not mass.

It's density and the curvature

of nearby space-time relative to size,

both increase.

Continue shrinking it and the space-time curvature

increases to infinity.

For example, if something the size of the Sun

were shrunk to a radius of three kilometers,

or the Earth to a radius of nine millimeters,

the curvature would be infinite.

Light itself would be unable to escape,

so the object would be invisible.

That boundary is known as the event horizon.

It is the origin of a black hole.

So the thinking was if subatomic particles

were smashed into superdense bits,

that could also create a black hole.

But then, no matter how small,

wouldn't such a black hole grow monterously

engulfing everything around it?

Eventually swallowing up the entire planet?

That's why those lawsuits sought

to stop the experiment in Geneva.

Physicist John Ellis holds that the device in Geneva,

the Large Hadron Collider, or LHC,

poses no danger at all.

There's absolutely no worry at all about black holes

that might be produced by the LHC.

If the LHC could make any black holes at all,

then cosmic rays, particles from outer space

that have been hitting the Earth for billions of years,

have been producing these black holes

and we're still here.

So, they can't be dangerous.

Countless particles are constantly

hurdling toward Earth at the speed of light.

And smashing to bits upon impact

with our atmosphere,

creating incredibly tiny black holes.

But Ellis and other physicists argued

that the life-span of these tiny black holes

is also incredibly brief.

These arguments prevailed, and the injunction was denied.

What strange properties.

The power to swallow up anything and everything,

but too short a life-span to do that in.

Black holes have an even more wondrous property.

Professor Andrew Hamilton of the University of Colorado

uses computers to create and evaluate remarkable phenomena

involving black holes.

The wonderful thing about Einstein's General Relativity

is that it is an extremely precise theory.

It's embodied in a set of equations which look well,

they're just an equation that relates curvature

to the energy momentum content of space-time.

And what does it mean?

It's a bunch of mathematics.

But the miracle of that is

that you can ask the mathematics questions.

What is the structure of the space-time

and how do things move in that space-time?

And code that up as if you were writing

a video game in software,

and see what it looks like.

This is one of Hamilton's

computer-generated black holes.

But the horizon of this so-called hole

actually has the shape of a sphere.

Map a grid of lines onto its surface,

like those indicating Earth's latitude and longitude

and two points stand out.

The black hole has a north pole and a south pole.

You can see the north pole and south pole

of the grid simultaneously.

Again, this is because the black hole

is able to bend light around it

so that you can see simultaneously

the north and the south pole.

Not something that you could see

if you looked at the Earth, for example,

from out in the solar system.

Look what happens if you simply toss

a cubicle box at a black hole.

One would expect anything at all to be sucked in,

yet the box sails on by.

Why is that so?

This is a feature of black holes is

that they do not suck.

Let's go back down to the black hole here.

They don't suck.

If you want to throw something into a black hole,

you have to aim and aim carefully.

So this time, a box

is pitched directly at the center.

The box twists under the stress

of powerful gravitational forces.

It falls towards the black hole.

But strange phenomena continue to occur.

One expects the box to disappear instantly

into the black hole, but instead it stays visible

as it slowly falls.

When it's finally reached the black hole,

it seems to rest there stuck on the surface.

What's the explanation for that?

As an object approaches a black hole,

the gravitational attraction increases rapidly.

And according to the Theory of Relativity,

the stronger the gravity, the slower the passage of time.

At the event horizon, time actually freezes.

As the box falls towards the black hole,

it accelerates rapidly.

But from the outside, time appears

to slow down the closer the box gets.

So eventually, the speed of the box seems

to let up gradually.

Finally, when it reaches the event horizon,

the box seems to stop moving.

As the probe approaches the horizon,

it appears to slow down and freeze.

Now in reality, the image would not only

slow down and freeze, but also become very dark.

We would see very few photons emerging

from this probe.

So it would appear to fade to black.

But, for the sake of seeing what's happening here,

I've kept it bright so that you can see

the probe has become frozen on the horizon.

A black hole is truly a strange object in space.

It may collapse as soon as it forms,

yet it's powerful enough to stop time.

So how is the existence of black holes verified?

Doctor, what are you doing?

I'm making a black hole.

So a black hole of this size would weigh roughly

10 times what the Earth weighs.

So this would be a very, very heavy black hole.

Kip Thorne is a physicist

whose search for black holes

is based on Einstein's General Theory of Relativity.

But he also pursues original topics

such as time to find wormholes and time machines.

His interest in the subject was first aroused

by the intense scholarly debates

over the very existence of black holes.

The controversy raged for more than half a century.

Thorne was in direct touch with the principle figures

in those debates.

He researched the entire controversy in detail

for the benefit of future generations of scholars.

There was great resistance to the idea of black holes.

The opposition was, much of it was motivated

by the view that this object

is so bizarre, so strange that it's unphysical.

And it's not likely that the true laws of physics

will predict such a thing.

This is Chennai on the east coast of India.

At a college in this city in 1929,

a young scientist first argued for the actual existance

of black holes in our universe,

Subrahmanyan Chandrasekhar,

his work at the age of 19

on the internal structures of stars

won him admission to the University of Cambridge

for post-graduate studies.

Onboard the ship to England,

Chandrasekhar gave some thought

to white dwarf stars nearing the end

of their life cycle.

One could say that modern black hole studies began

with ancient white dwarfs.

A star normally burns furiously,

balancing gravitational forces that could collapse it

and explosive forces that could blow it up.

But as its nuclear fuel is used up, the star cools.

And with those expansionary pressures relenting,

it begins to contract.

Conventional theory held that a star contracts

to about twice the size of the Earth, then it stops.

That is what is called a white dwarf star.

The reason why the contractions stops

lies in the star's very atoms.

As the star shrinks, its atoms are compressed.

Conventional theory held that there are limits

to that compression beyond which

further shrinkage is impossible.

This is a white dwarf star surrounded

by an expanding nebula.

The star, maximally compressed,

is clearly recognizable within a cloud of gas and dust.

A white dwarf star is compact and very heavy.

In size, it may be comparable to Earth,

but its mass is more like the Sun's.

As if a lump of sugar weighed several tons.

At the time of Chandrasekhar's passage to England,

it was thought that all stars ended

their lives as white dwarfs.

Chandrasekhar based his arguments

on his calculations of the changes undergone

by white dwarfs as their density increased.

His results were astounding.

Beyond a certain mass, the white dwarfs

shrink to infinity.

Previous calculations held that the limit

of a star's shrinkage would be a radius

of 10,000 kilometers.

But Chandrasekhar reckoned that if a star were

at least 1.4 times the mass of our Sun,

it would be unable to resist

its own gravitational pressures.

It would completely collapse,

and shrinkage would continue infinitely.

This is precisely what we now call a black hole.

The black hole had emerged accidentally

from a consideration of white dwarfs.

Soon after arriving in Cambridge,

Chandrasekhar presented a paper on his findings.

Cambridge was then the academic home

of Sir Arthur Eddington, one of the world's foremost experts

on the internal structure of stars.

Eddington was also famous as an explicator

and defender of Albert Einstein's just published

General Theory of Relativity.

All stars ended up as white dwarfs, thought Eddington.

Surprisingly, he nonetheless praised Chandrasekhar's paper

and promised to support it.

But then...

The time came when Chandra was to present the results

that he had to a meeting of I think it was the,

it may have been either Royal Astronomical Society

or the Royal Society of London.

I don't recall which.

And when he, right after he presented the results,

Eddington got up and criticized them very severely.

Eddington's rebuttal was caustic indeed.

The eminent scientist asserted that a star

might collapse to a few kilometers radius,

but no smaller.

"I think there should be a law of nature," he said.

"To prevent a star from behaving"

"in this absurd way."

Why exactly did Eddington criticize

Chandrasekhar so harshly?

Thorne believes that Eddington was simply being fierce

in his pursuit of scientific truth.

It's my suspicion,

I think that it is likely that in fact,

Eddington was treating Chandra at that time

as a colleague.

And then, in England at the time there were

serious intellectual battles between colleagues.

But Chandra had not yet grown up to the point

that he felt like he was a colleague of Eddington's.

He felt it was an unequal match.

But Eddington, I think, I suspect

that Eddington admired Chandra.

He always said he did.

After that, Chandrasekhar

changed his workplace from England

to the United States.

Later, Thorne invited him to come to Caltech,

and they developed a close relationship

lasting until Chandrasekhar's death in 1995.

In 1932, the black hole controversy again ignited.

The spark was provided by a new theory in physics.

It was known that an atomic nucleus

was comprised of protons and neutrons.

But under extreme compression,

protons and electrons could combine forming neutrons.

And these could be compressed even further.

That meant that the remaining mass of an exploded star,

1.4 times larger than our Sun or greater

could turn into a neutron star.

Neutron stars can now actually be observed.

The Crab Nebula is the remnant of a supernova explosion.

A special camera can peer into its depths.

The bright celestial body at the center

of that gaseous disk is a neutron star.

It is small, but incredible heavy as if a lump

of sugar weighed hundreds of millions of tons.

Scientists at the time thought

that dense stars must be either white dwarf stars

or neutron stars.

They denied the existence of black holes.

At this point however, a dissenting voice was raised,

that of J. Robert Oppenheimer.

A brilliant mathematician himself,

Oppenheimer, like Chandrasekhar,

calculated the mass of a neutron star.

He found that a star at least triple the mass

of our Sun would not stop at the neutron star stage,

but would suffer complete gravitational collapse,

contracting infinitely.

This constituted the reappearance

of the theory that black holes actually can exist

in our universe.

But a counter-argument was put forward

by John Wheeler, one of Oppenheimer's colleagues

at Princeton University.

When Kip Thorne was in graduate school,

Wheeler was his mentor.

As to why a massive star could not become a black hole,

Wheeler argued as follows,

he said that a dying star would discharge gases

in a process that actually made it lighter.

So every star would merely become a neutron star.

We can actually observe an aging giant star

emitting huge volumes of gas.

The controversy between the two experts continued

for over a decade.

Wheeler was fierce in his refutations

of Oppenheimer's thesis.

But as he rechecked his calculations,

he came to have doubts about his own position.

So John Wheeler, like Albert Einstein,

had very deep physical intuition and insights.

And like Einstein, he was usually right,

and sometimes wrong.

Finally, even Wheeler accepted the existence

of black holes.

He then pushed forward the study

of black holes even further than Oppenheimer.

In fact, it was actually Wheeler

who gave the strange infinitely contracting celestial bodies

the name of black holes.

With Wheeler's conversion, a half century

of controversy among scientists was concluded.

It was now accepted as indisputable

that dying giant stars unable

to withstand their own gravitational forces

would contract infinitely, forming black holes.

It was Subrahmanyan Chandrasekhar who set scientists

on the path that led them to acknowledge

the existence of black holes in our universe.

In 1983, Chandrasekhar's work on the structure of stars

and their evolution was recognized

when he was named as co-recipient

of the Nobel Prize for Physics.

And I sent him a note of congratulations,

and he acknowledged it.

But I think we never discussed the Nobel Prize.

But he was among scientists I have known,

he was one of the most self-critical,

and the most intensely driven.

But driven from within and not driven

to receive acknowledgement from other people

for his discoveries.

The result, not only were

black holes acknowledged as existing,

but light was shed even on the processes

by which they were born.

And yet, they existed only in theory.

Actually discovering a black hole

was a dream of many a scientist.

Among them, a young Japanese enthusiastic.

Boston, Massachusetts, USA.

A certain Japanese man regularly stopped

by this pet shop in 1963.

He seemed to like watching mice

and other small animals there.

Little did anyone suspect, that their activities

concealed a key to the development of black holes.

Minoru Oda was at that time a visiting faculty member

at the Massachusetts Institute of Technology.

An MIT research group had launched

cutting edge imaging equipment by rocket

to obtain x-ray images from outer space.

Bruno Rossi was in charge of these observations.

He was also the one who had invited Oda

to the United States.

It was known that the sun emitted x-rays.

However, x-radiation from other celestial bodies

is absorbed by the Earth's atmosphere.

Hardly any of it could be detected

by Earth-based observation.

Rossi's group, working on the hypothesis

that there must be other x-ray emitting celestial bodies,

used a rocket to detect this radiation.

They found even stronger x-rays

than they had expected.

The equipment they used however,

could not tell them much

about the direction the x-rays came from.

Oda and Rossi talked it over at the beach one summer.

The area marked in red they knew, emits x-rays.

And they knew it was in the constellation Cygnus.

But they did not know whether the radiation

emanated from particular stars were more generally

from that sector.

So how could one pinpoint the source of those x-rays?

Oda got a clue from the pet shop he'd been going to.

Oda was fascinated by seeing

something alternately hidden and revealed.

When he got back to Japan, he applied his insight

to the development of an imaging device.

Here are Oda's prototypes.

Looking at the arrays of fine wires,

he called his invention a screen collimator.

When two or more of these screens

were placed in front of a detector,

even slight differences in the origin of x-rays

would cause some to pass through,

some to be blocked.

The concept was that that could

help refine estimates of directionality.

At the time however, Japan had no rocket

with which to launch such a device.

So Oda, determined to pinpoint

the source of that x-radiation,

devised another way to provide his device

with a space-based platform.

There is archival video of his effort.

The experiment took place in Fukushima, Japan in 1966.

Oda sent his screen collimator aloft in a balloon.

When its observations were done,

it descended by parachute for recovery

at sea or in the mountains.

Observational missions using Oda's collimator

continued for four years.

This helped narrow down the source of the x-rays.

The yellow oval marks the area identified

by the collimator as containing the source.

It was limited area.

In 1970, the US launched Uhuru, the world's first satellite

for the detection of x-rays.

It's very first observations were

of those mysterious x-rays.

Oda was a guest investigator for this project.

Uhuru refined further the calculations

regarding the source of the x-rays.

Even more detailed observations followed.

April 1971, at last the origin

of the x-rays was pinpointed.

It had taken seven years to solve the riddle.

Near the source of the x-rays was a blue supergiant star

some 30 times the mass of our Sun.

Analysis of the light from that star

produced a startling discovery.

The color of the star was changing slightly.

That indicated movement.

Further analysis showed that the star

was circling some other object

in a brief cycle lasting 5.6 days

for one revolution.

It would take a massive object indeed

to keep a supergiant star in its orbit.

From the blue supergiant star's movement and spectra,

the mass of its unseen partner was estimated

as being equivalent to 10 of our Suns.

But that celestial body could not be found

at the expected location.

A star 10 times the mass of the Sun,

and yet invisible to us,

emitting powerful x-rays as well.

It had to be a black hole.

The first actual black hole ever discovered

though observation.

It was named Cygnus X-1.

Kip Thorne was one of many scientists delighted

by this discovery.

Oh, it was very exciting when Cygnus X-1 was observed.

There had been predictions

by several astrophysicists

that if you had a black hole,

and it captured matter from star,

it would produce x-rays.

When Cygnus X-1 was found to be the source

of those intense x-ray emissions,

Thorne made a bet with his friend,

theoretical physicist Stephen Hawking

as to whether it was a black hole or not.

This is the wager as written.

Thorne bet that Cygnus X-1 was a black hole.

Hawking bet against that proposition.

At stake, were magazine subscriptions.

After the initial discovery of Cygnus X-1,

it was observed further.

Examination of data on its mass

and on variations in its x-ray emissions

led to a broad scientific consensus

that this was indeed a black hole.

In 1990, 16 years after the wager was made,

Hawking's concession was duly noted

on the original betting contract.

He bet that Cygnus X-1 was not a black hole,

and he hoped that he was wrong.

And I bet that it was a black hole.

No one was more cautious than Hawking

in interpreting observational data.

And now, even he acknowledged Cygnus X-1

to be a black hole.

After the initial discovery of Cygnus X-1,

Japan launched a series of satellites

for x-ray observation,

making significant contributions to the study

of black holes.

Asuka, launched in 1993, undertook further observations

of Cygnus X-1 obtaining a wealth of detailed data.

The first black hole ever discovered,

it's location around the middle

of the neck of the constellation Cygnus, the Swan

7,500 light years from Earth.

The black hole and its companion star

are paired in what is called a binary system.

They are only 30 million kilometers apart.

That's less than the distance between the Sun and Mercury.

Gases from the blue supergiant stream

to the black hole.

The gases, heated by friction, reach temperatures

as high as 10 million degrees Celsius,

and generate powerful x-rays.

The mass of the black hole is equal

to more than 13 our Suns,

yet it's radius is a mere 40 kilometers.

Above and below the black hole are two jets.

The discovery and elucidation of this system

has ended 50 years of scientific controversy.

Minoru Oda contributed to the first ever discovery

of a black hole.

His concepts and inventiveness turned the impossible

into the possible.

That legacy continues to inspire.

Can one see a black hole with the naked eye?

Scientists on the cosmic front are now trying

to undertake direct observations of black holes.

But can that be done?

With formulas derived from the General Theory of Relativity,

Rohta Takahashi tried to deduce mathematically

what a black hole would look like when directly observed.

It took him four years to arrive at a solution.

This is how Cygnus X-1 is currently imagined

based on observed data.

The black hole is deep in the bottom

of that dark center area.

If one could see it with a sufficiently powerful telescope,

this is what it would look like.

The gases that have been sucked

into the black hole are superheated

by that violent friction and shine brightly.

That bright light makes the invisible black hole

appear to take the form of a black ball.

This phenomenon is called a black hole shadow.

The bright light to the left of the ball

is from the superheated gases

which are forming a disc, spinning at high speed.

Even some background light is visible at the fringes,

despite the gravity induced invisibility

of the black hole itself.

Unfortunately, says Takahashi,

Cygnus X-1 is too small a black hole

to be observed more directly

with today's technology.

A black hole that is easier to view

has been found however, right in the middle

of our own Milky Way Galaxy.

Equivalent in mass to four million of our Suns,

this is a monster black hole.

Its event horizon radius exceeds 10 million kilometers,

so large that it would look quite different

from a small black hole like Cygnus X-1.

Assuming it could be observed from Earth,

Takahashi envisions it as looking like this.

Takahashi has calculated

just how strong a telescope would be needed

to observe this black hole from Earth.

It would have to be powerful enough

so that from Tokyo, one could make out

the baby hairs on the face of someone standing

on the summit of Mount Fuji, 100 kilometers away.

The attempt has already begun.

MIT's Haystack Observatory in the suburbs of Boston.

Sheperd Doeleman has been cooperating

with the National Astronomical Observatory of Japan

in the effort to observe a black hole directly.

Here, data from radio telescopes all over the world

are combined and analyzed.

They may not have a telescope capable

of seeing from Tokyo, the baby hairs

on someone standing on Mount Fuji,

but they can emulate that power.

Actually I think it's running now, so you can see.

And to get the high angular resolution

that you need to see the event horizon,

the boundary of the black hole,

we create an Earth-size virtual telescope

using radio telescopes spread all around Earth.

And we tie them together to make a picture

as though we had a telescope as large

as the Earth itself.

At the US National Radio Astronomy Observatory,

they have an array of 27 parabolic antennas,

each 25 meters in diameter.

The diameter of the remote telescopes

is determined by the desired resolution of the image.

By combining data from multiple remote telescopes,

one can emulate the capabilities

of one giant telescope,

and obtain high-resolution images.

To obtain the highest possible resolution,

in their effort to capture a black hole shadow,

Doeleman and his colleagues

used submillimeter telescopes.

This technology is called Very Long Baseline Interferometry.

The plan calls for linking three submillimeter telescopes

in Hawaii, California and Chile

to emulate one gigantic Earth-size telescope.

We really hope that in five years,

we have started to make a very good progress

on actually making an image of the black hole itself.

In the near future,

we will be able to peer directly into a black hole.

The invisible black hole,

at first it was a theoretical proposition,

but its reality has been confirmed

and a consensus has emerged.

Actual observations have produced scientific proof

that black holes exist in our universe.

The same inexhaustible curiosity

that led to the discovery of black holes,

powers an ongoing quest to view them directly

and to behold the wonders they will surely reveal.