All language subtitles for Cosmos.A.Space.Time.Odyssey.S01E04.HDTV.x264-LOL - A Sky Full Of Ghosts

NEIL DEGRASSE TYSON:
Seeing is not believing.

Our senses can deceive us.

Even the stars are not
what they appear to be.

The cosmos,
as revealed by science,

is stranger than
we ever could have imagined.

Light and time and space
and gravity

conspire to create realities

which lie
beyond human experience.

That's where we're headed.

Come with me.

Back in 1802,
on a night like this,

the astronomer William Herschel
strolled the beach

on the English coast,
with his son John.

Herschel was
the first person ever

to see into the deeper waters
of the cosmic ocean.

There he glimpsed
the magic trick

that light does with time.

Father...

do you believe in ghosts?

Why, yes, my son!

You, you do?

I would not have thought so.

Oh, no, not in the
human kind of ghost.

No... not at all.

But look up, my boy,

and see a sky full of them.

The stars, Father?

I do not follow.

Every star is a sun as big,
as bright as our own.

Just imagine how far away from
us you'd have to move the Sun

to make it appear as small
and faint as a star.

The light from the stars
travels very fast...

faster than anything...

but not infinitely fast.

It takes time for their
light to reach us.

For the nearest ones,
it takes years.

For others, centuries.

Some stars are so far away,

it takes eons for their
light to get to Earth.

By the time the light
from some stars gets here,

they are already dead.

For those stars,
we see only their ghosts.

We see their light,

but their bodies perished
long, long ago.

John, I have seen
further back in time

than any man before me--

millions of years
into the past.

DEGRASSE TYSON: William Herschel
was the first person to understand

that a telescope
is a time machine.

We cannot look out into space

without seeing back in time.

In one second, light travels
300,000 kilometers,

or 186,000 miles.

That's nearly the distance
from the Earth to the Moon.

So, the Moon is about
one light-second away.

The next time
you look at the Moon,

you'll be seeing
one second into the past.

Sync and corrections by n17t01
www.addic7ed.com

DEGRASSE TYSON:
That Sun...

it's not really there.

It won't actually be
above the horizon

for another two minutes.

The sunrise is an illusion.

Earth's atmosphere bends
the incoming rays of sunlight

like a lens
or a glass of water.

So we see the image of the Sun
projected above the horizon...

before the physical Sun
is actually there.

That Sun behind me is a mirage.

No more real
than the shimmering image

that hovers in the distance

over a desert road on a hot day.

Sunlight takes about
eight minutes to reach Earth,

so the Sun is eight
light-minutes away.

From Earth, we can
only ever see the Sun

as it was eight minutes ago.

And another thing,

the Sun doesn't really
"rise" at all.

The Earth turns
and we turn with it.

It may not look like it,
but right at this moment,

I'm moving faster
than a jet plane

and so are you
and everyone on Earth.

While I'm at it,

that horizon...

it's not really there at all.

There's no edge.

The horizon is just
another illusion.

The distance between Earth

and the outermost planet Neptune

varies as the planets
orbit the Sun.

On average, the light
makes that trip in four hours.

So for us on Earth,

the Neptune we see is always
four hours in the past--

four light-hours away.

But the distances
to the planets,

even the farthest one...

are mere baby steps
on a much grander scale

of the stars and galaxies.

As soon as we leave the Sun's
immediate neighborhood,

we need to change
the unitive distance

from light-hours to light-years.

A light-year
is the yardstick of the cosmos.

A single one is nearly
ten trillion kilometers,

or about six trillion miles.

It's a unitive distance,
just like a meter or a mile.

It's the distance
light travels in a year.

The nearest star to the Sun,
Proxima Centauri,

is a little more than four
light-years away from Earth.

How far away
is four light-years?

NASA's Voyager spacecraft moves

at more than
56,000 kilometers an hour.

Even at that astonishing speed,
it would take Voyager

more than 80,000 years
to reach the nearest star.

And the stars of the
Pleiades cluster,

400 light-years away.

The Ship of the Imagination

is equipped with a
highly unusual capability--

one-of-a-kind, actually.

It makes it possible for us
to see what was happening

when the light from a distant
star or galaxy first set out

on its long journey to Earth.

♪ ♪

DEGRASSE TYSON: When that light left
the Pleiades, about 400 years ago,

Galileo was taking his first
look through a telescope.

A few years later, he tried to
measure the speed of light,

but he couldn't do it.

He had a very clever plan,
but the technology of that era

just wasn't good enough to
measure the motion of anything

that moves as fast as light.

When we look at
the Crab Nebula from Earth,

we're seeing much farther
back in time.

The Crab Nebula
was once a giant star,

ten times the mass of the Sun,

until it exploded
in a supernova.

At its heart is a pulsar,

a collapsed star
the size of a city,

spinning 30 times a second.

This pulsar's
whirling magnetic field

whips nearby electrons
into a frenzy,

accelerating them
to almost the speed of light.

They shine with a blue glow that
lights up the tendrils of gas

still unraveling
from the supernova.

The Crab Nebula

is about 6,500
light-years from Earth.

According to some beliefs,

that's the age
of the whole universe.

But if the universe were only
6,500 years old,

how could we see the light
from anything more distant

than the Crab Nebula?

We couldn't.

There wouldn't have been
enough time for the light

to get to Earth
from anywhere farther away

than 6,500 light-years
in any direction.

That's just enough time
for light to travel

through a tiny portion
of our Milky Way galaxy.

To believe in a universe

as young as
6,000 or 7,000 years old

is to extinguish the light
from most of the galaxy,

not to mention the light
from all the 100 billion

other galaxies
in the observable universe.

The center of our own galaxy

is about 30,000 light-years
from Earth.

The light we see today

coming from the core
of the Milky Way left there...

when our ancestors
were perfecting a way

to vanquish death...

by making art with the power

to inspire those who would come
long after they were gone.

♪ ♪

The light we see
coming from the Sombrero Galaxy

is 30 million years old.

Our ancestors
were living in trees

when that light started out.

They weighed about five kilos
and had long tails.

But even 30 million
light-years away

is still in our own
cosmic backyard.

That galaxy is part
of the Coma Cluster,

320 million light-years away.

What was going on back home

when the light you are seeing
began its trip to Earth?

No familiar continents,
oceans or rivers.

Our distant ancestors were just
leaving the water for the land.

That's pretty old light,

but not nearly
the oldest light we can see.

The oldest light is very faint,

a pale ghost in the night.

See that red blob
inside the circle?

That's one of the oldest
galaxies we've ever seen.

You're looking at 13.4-billion
year-old starlight

as captured by
the Hubble space telescope.

It's coming from the very first
generation of stars.

What was happening on Earth
back then?

Absolutely nothing.

There was no Earth,
no Sun, no Milky Way.

They would not come to be
for billions of years.

When we try to look even farther
into the universe,

we come to what appears
to be the end of space...

but actually...

it's the beginning of time.

DEGRASSE TYSON:
Earth pulls on us.

Our lives are a relentless
struggle with gravity.

That little girl is trying
her best to climb out

of a gravitational well.

From our first efforts to stand
to our final surrender,

we are struggling to overcome
the Earth's pull.

We are born, live and die
in a force field--

one that is almost as old
as the universe itself.

And how old is that?

To visualize the 13.8 billion
year age of the universe,

we've compressed all
of cosmic time

into a single
year-at-a-glance calendar.

Midnight on December 31
is this very moment right now.

And January 1
is the beginning of time.

See that glowing fog out there?

It's radiation left over
from the Big Bang,

the explosion that made
the universe

13.8 billion years ago.

Right now, we're at the very
edge of known space and time.

So what happened before
the Big Bang?

Nobody knows.

No evidence survives
from before that moment.

We've got
some pretty crazy ideas

about where
the universe came from,

which we'll get to, in time.

Where are we in the universe?

At the very center.

In the observed universe,
everyone gets to feel special.

No matter which galaxy
you happen to live in,

when you look out to the
universe, you'll find yourself

at the center
of the cosmic horizon.

But this is just an illusion.

In reality, there is no center,

and the cosmic horizon
is no more real

than the horizon at sea.

It's what you get when you have
a finite speed of light

in a universe that had
a beginning in time.

A few hundred million years
after the Big Bang,

vast clouds of hydrogen
and helium condensed

into the first stars
and galaxies.

With these new sources
of light,

the long dark ages
of the universe ended.

As space continued to expand,

cosmic evolution unfolded
on grander scales.

As the first generation
of stars died,

they seeded space
with heavier elements,

making possible
the formation of planets,

and ultimately, life.

Matter and energy were formed
in the Big Bang.

But that's not all.

Space and time
were created, too,

and all the forces
that bind matter together,

including gravity.

Isaac Newton discovered
a mathematical law

that describes
how gravity works.

With that law, he could explain
the motions of the planets.

More than 100 years later,

William Herschel realized
gravity could do much more.

John, can you keep a secret?

Yes, Father.

I've made a discovery and have
yet to tell another soul.

The gravity that
holds us to the Earth--

the same gravity
that Newton showed

keeps the planets
in their orbits--

I've discovered

that it also rules
the distant stars.

Father... but how
can you know this?

Can you find the
constellation of the Lion?

There.

Well done.

Can you now find the star

that joins the Lion's
head to his body?

That one.

WILLIAM: That star
is really two stars

so close together that
they appear to be one.

I've been watching them
through my telescope

since long before
you were born.

They dance around
each other very slowly.

More slowly than any planet
moves around the Sun.

Many of the stars
we see tonight,

perhaps most of them,

dance with invisible partners.

Gravity's empire
governs all the heavens.

DEGRASSE TYSON:
A century earlier,

Isaac Newton had been haunted

by the same absence
of a mechanism for gravity.

How could distant bodies
affect each other

across empty space
without actually touching?

This "action at a distance,"
as he called it, baffled him.

In the 19th century,
Michael Faraday discovered

that we were surrounded
by invisible fields of force

that explained
how gravity works.

The apple and the Earth
don't touch each other,

but the fields between them do.

He imagined those lines
of gravitational force

radiating out into space
from every massive body--

the Earth, the Moon,
the Sun, everything.

Here was the answer
to that question

that had stumped Newton.

In 1865, James Clerk Maxwell
translated Faraday's idea

about fields of electricity
and magnetism

into mathematical laws.

He discovered that these fields
move through space in waves.

When he calculated
how fast they move,

it turned out to be
the speed of light.

We were beginning
to discover the threads

of the cosmic tapestry,

but we were not yet able
to discern the rich pattern

that time, light, space
and gravity weave.

As Albert Einstein
worked in Berlin

on his theory of gravity,

he kept the portraits
of these three men before him.

He knew he was standing
on their shoulders.

Years before, as a teenager,
he had an insight

that was as Earth-shaking
as any idea of theirs.

And it happened one summer

while he was daydreaming
in Italy.

In the summer of 1895,

Einstein's father's business
in Germany had failed,

and the family had moved here
to northern Italy.

Young Einstein
loved wandering these roads

and giving his mind
free rein to explore.

There's something timeless
about this place.

Nothing here has really changed

since the time
of Einstein's early daydreams.

One day,
he began to think about light

and how fast it travels.

In everyday life,
we always measure the speed

of a moving object with respect
to something else.

Something that's
presumably not moving.

Something in the cosmos
that's not in motion.

For example, I'm moving
about ten kilometers per hour

relative to the ground.

But as I mentioned earlier,
the ground is moving.

Earth is turning at more than
1,600 kilometers per hour

while it orbits the Sun

at more than 100,000
kilometers per hour.

And the Sun is moving
through the galaxy

at a half a million
miles per hour.

And the Milky Way is moving
through the universe

at nearly one and a half
million miles an hour.

There is no fixed place
in the cosmos.

All of nature is in motion.

It was hard even for
the young Einstein

to imagine
some absolute standard

to measure all those relative
motions against.

This is the very book

that inspired Einstein
as a young boy.

Give a kid a book
and you change the world.

In a way, even the universe.

Look at this--
the very first page,

it describes
the astonishing speed

of electricity through wires

and light through space.

Einstein remembered
what he'd learned as a child

from this book,

and perhaps,
for the first time, right here,

wondered what the world
would look like

if you could travel
at the speed of light.

The more Einstein thought
about it,

the more troubled he became.

If you imagine traveling
at the speed of light,

paradoxes seem
to pop up everywhere.

Einstein was shocked
to realize that so much

of what had been
uncritically accepted as truth

by even the greatest
authorities on the subject

was just plain wrong.

When traveling at high speeds,

there are certain rules
which must be obeyed.

Einstein called these rules
"The Principles of Relativity."

Imagine that young woman
who just blew past us

on the motorbike,

imagine she was riding her bike

through the cosmos.

Light from
a moving object travels

at the same speed,
no matter whether the object

is at rest or in motion.

Her speed is not added
to the speed of light.

The light from her motorbike

still travels
at the speed of light.

Nature commands,

"Thou shalt not add my speed
to the speed of light."

Also, no material object

can travel at or faster
than the speed of light.

There's nothing in physics
that prevents you

from traveling as close to
the speed of light as you like.

99.9% of the speed of light
is just fine,

but no matter how hard you try,

you never gain
that last decimal point.

For reality to be
logically consistent,

there must be
a cosmic speed limit.

(thumps, horse whinnies)

(whip cracks)

The crack of that whip
is due to its tip

moving faster
than the speed of sound.

It makes a shockwave,

a mini sonic boom,
in the Italian countryside.

A thunderclap works
the same way,

and so does the sound
of a passing supersonic jet.

So why is the speed of light

any more a barrier
than the speed of sound?

The answer is not just
that light travels

about a million times
faster than sound.

And it's not merely
an engineering problem,

like building
the first supersonic jet.

Instead, the light barrier

is a fundamental law of nature,

as basic as gravity.

Einstein found his absolute
framework for the world,

this sturdy pillar
among all the relative motions

within the motions
of the cosmos.

Light travels just as fast,

no matter how fast or slow
its source is moving.

Speed of light is constant,
relative to everything else.

Nothing can
ever catch up with light.

The thing
about the laws of nature

is that they're unbreakable.

The job of physicists is
to discover these commandments,

the ones that do not vary
from culture to culture

or time to time

and hold true
throughout the cosmos.

That's why, as Einstein showed,

funny things happen
close to the speed of light.

Traveling close
to the speed of light

is kind of an elixir of life

because your biological clock
slows down

relative to those
you leave behind.

This phenomenon
may provide us humans,

who only live
for a century or so,

a practical means
to travel to the stars,

where the magic show
of spacetime

really gets crazy.

DEGRASSE TYSON: The 19th-century
astronomer William Herschel

loved to share the wonders
of the universe

with his son John.

I once had a friend,
very clever fellow,

an astronomer and
a parson at Leeds,

by the name of John Michell.

Poor man died when
you were a babe,

God rest his soul.

He held that some stars

are invisible.

They really exist,
but we shall never see them.

"Dark stars,"
Michell called them.

With all due respect, Father,

surely your friend was mistaken.

If no one can see them,

then how can we possibly know
they exist?

Did you see the man
who left those footprints, John?

Why, no, Father.

I did not.

But do you know that he exists?

DEGRASSE TYSON: John Michell is
one of the greatest scientists

you've probably never heard of.

He lived and worked in England
in the 18th century.

If he ever sat for a portrait,
it no longer exists.

He was once described
by an acquaintance

as "a short little man,

of black complexion, and fat."

Michell imagined a star so big,

so massive,
that nothing, not even light,

could escape
its gravitational grip.

Can you find the dark star?

You can't see it
with your eyes, not directly,

but it may leave
a kind of footprint

on the cosmic shore.

Michell realized that we might
be able to detect

some of these dark stars because
of their extreme gravity.

If one happened to be near

a smaller,
luminous companion star,

that star would appear
to travel in a tight orbit

around nothing.

Even though we can't see it,

we know something
with a lot of mass

has to be right there.

A dark star,

or what today we call
a black hole.

What does a black hole look like

and what would it
be like inside?

We'll get there, but first,

let's make a pit stop
in my hometown,

New York City,

where it's always seemed to me

that everything
is in constant motion.

I've lived here most
of my life.

There's always
something new to see.

But one thing never changes--
gravity.

Gravity on Earth
has been the same

for the past
four and a half billion years.

But what if, today,
we could alter it?

Gravity is a distortion

in the shape of spacetime

as Einstein showed.

Space can expand and contract

and warp without limit.

If the Earth's size or density

were even a little different,

its gravity would be, too.

There's an infinite range
of possibilities.

New Yorkers feel right at home

in the gravitational pull
of the Earth,

called "one g."

Suppose we turn off the gravity
on one of its streets.

People and objects
that were already in motion

are launched into flight.

Now what if I turn
the gravity up

to, say, eight or nine g's?

Out of compassion,

let's evacuate the area.

This is about the same g-force

that a fighter pilot in
a high-speed turn would feel.

A few minutes of this
wouldn't hurt you,

but it wouldn't be comfortable.

At 100,000 g's,

even fire hydrants
become crushed

by their own enormous weight.

But at millions of g's,

even light bows to gravity.

The light still moves
at its constant speed,

but it cannot escape.

Michell's dark star...

our black hole.

And the nearest one
may be closer than you think.

Not every star can become
a black hole.

Only about one in a
thousand is massive enough.

The nearest one could be
within 100 light years of Earth.

Black holes aren't the mythic cosmic
vacuum cleaners of science fiction.

They don't go around gobbling up
unsuspecting worlds.

You've got to come to them.

But if you do,

it might be the last thing
you ever see.

(rumbling)

That was us resisting
a few million g's of gravity.

Don't forget,
that thing swallows light.

We'll keep our distance.

When giant stars exhaust
their nuclear fuel,

they can no longer
stay hot enough

to fend off the inward pull
of their own gravity.

The most massive stars
collapse into darkness,

leaving only
their gravity behind.

This black hole enshrouds
the shrunken corpse

of a supergiant star.

The star itself has shriveled
into something

even smaller
than this darkness,

only 64 kilometers wide.

This is the first black hole
ever discovered--

Cygnus X-1.

How did we on Earth
ever find something

so small and dark and far away?

We looked at it in another
kind of light. X-rays.

In X-ray light, we lost sight
of the blue star

because its surface
is a tepid 30,000 degrees.

But the disk of gas around
the black hole

glowed brilliantly in X-rays
at 100 million degrees.

As William Herschel discovered,

many stars have close companions
forming a binary star system.

But if one member of
such a pair is enormous

and the other is compact,

the smaller star can drain
and consume the atmosphere

of its larger sibling.

This neurotic relationship
can last for millions of years.

The atmosphere of the larger
star was being siphoned onto

a glowing hot accretion disk
that revolves around

and spirals into a black hole.

The overwhelming gravity was
accelerating the blue star's gas

into a death spiral,

crossing
the spacetime boundary,

never to be seen again.

The fateful boundary
that separates a black hole

from the rest of the universe
is called an event horizon.

From our point of view,
the substance in the disk

slows down as it approaches
the event horizon,

never quite reaching it.

But if you were riding
on that spiraling gas--

and I don't advise it--

you would sail past the event
horizon in a matter of seconds

into the undiscovered country
from which no traveler returns.

We have searched the hearts
of dozens of galaxies,

and in every case, we have found
a super-massive black hole.

Our own galaxy is no exception.

The stars nearest the center
of our galaxy whip around

at more than 40 million
kilometers an hour.

What could make them move
so fast?

The only logical explanation

is that something with the mass

of four million suns
lies at the center.

So where's the blazing light
of four million suns?

Since we can't see it,

it must be imprisoned
inside a black hole.

Earth is far enough away
to be perfectly safe.

Other worlds might not be
so lucky.

If you somehow survived
the perilous journey

across the event horizon,

you'd be able to look back out

and see the entire future
history of the universe

unfold before your eyes.

How?

Because when
spacetime is warped

by the extreme gravity
of a black hole,

time is stretched to the limit.

But what would be
in front of you?

Before we go there,
I should warn you

that we're entering uncharted
scientific territory.

For all we know, there may be
undiscovered laws of physics

that govern events at the center
of a black hole.

But until the next Einstein
comes along,

let's perform
a thought experiment.

That's how John Michell
first imagined dark stars

in the 18th century,

(voice distorting): and how Einstein
conceived of his theory of rela...

(rumbling, whooshing)

JOHN HERSCHEL: Father, do you
believe in ghosts?

WILLIAM HERSCHEL: Oh, no, not in
the human kind of ghosts.

No, not at all.

But look up, my boy,

and see a sky full of them.

DEGRASSE TYSON: If you could survive
the trip into a black hole,

you might emerge
in another place

and time in our own universe,

circumventing the first
commandment of relativity...

thou shalt not travel
faster than light.

Nothing can move through space
faster than light.

But space is not
mere emptiness.

Its properties can stretch
and shrink and can be deformed.

And when that happens,
time is deformed, too.

Einstein discovered that space
and time are just two aspects

of the same thing, spacetime.

Spacetime itself can
deform enough

to carry you anywhere
at any speed.

Black holes may very well
be tunnels through the universe.

On this intergalactic subway
system, you could travel

to the farthest reaches
of spacetime,

or you might arrive in
someplace even more amazing.

We might find ourselves in an
altogether different universe.

But how can a whole universe fit
inside of a black hole,

which is only a small part
of our universe?

It's another magic trick
of spacetime.

The phenomenal gravity
of a black hole

can warp the space of
an entire universe inside it.

Our local gravity might be
a drag to us,

but it's really feeble compared

with what goes on inside
a collapsed star.

As far as we know,

when a giant star collapses
to make a black hole,

the extreme density
and pressure at the center

mimic the Big Bang, which gave
rise to our universe.

And a universe inside
a black hole

might give rise
to its own black holes.

And those could lead
to other universes.

Maybe that's how
our cosmos came to be.

For all we know,

if you want to see what it's
like inside a black hole,

just look around you.

William Herschel went on
to discover that the sun

and its planets are moving
through the Milky Way.

And whatever became
of his son John?

He grew up to become
a great scientist.

His deep-space observations
built on those of his father

to become the basis for the
standard catalog of galaxies

we use today.

When William was in failing
health, John stayed with him

through the long nights
at his telescope

to help him sweep the stars.

And when his father died,
John wrote his epitaph...

"He broke through
the walls of heaven."

John often reminisced

about those summer nights
with his father.

Maybe that's why he sought
a way to preserve the past.

John Herschel was one
of the founders

of a new form of time travel,

a means to capture
light and memories.

He actually coined
a word for it,

photography.

When you think about it,

photography is a form
of time travel.

This man is staring at us
from across the centuries...

a ghost preserved by light.

It's not hard to imagine
that in the near future,

we'll be able
to capture the past

in all three dimensions.

We'll be able
to step inside a memory.

It may not be possible
to travel backward in time,

but perhaps, one day,
we can bring the past to us.

Here's a moment from my past.

Like John Herschel,

I'm remembering
a younger version of myself.

December 20, 1975.

A snowy day in Ithaca, New York.

A branchpoint on the road
that brought me

to this moment with you.

It was the day
I met Carl Sagan.

Reminds me of those
ghost stars in the sky...

you know, the ones that still
shine their light upon us

long after they're gone.

Sync and corrections by n17t01
www.addic7ed.com