All language subtitles for Cosmos Carl Sagan - 1x10 - The Edge of Forever.HDTV.en

(HEART BEATING)

SAGAN: There is one experience
that every human shares...

...of every language and culture:

The experience of birth.

Our recollections of birth are
hazy at best.

They have the feel and aura
not so much of memories...

...as of mystical transfigurations.

It would be astonishing if
this profound early experience...

...did not influence
our myths and religions...

...our philosophy and our science.

The birth of a child evokes
the mystery of other origins...

...the beginnings and ends
of worlds...

...infinity and eternity.

How did the universe arise?

What was around before that?

Might there have been no beginning?

Could the universe be infinitely old?

Are there boundaries to the cosmos?

The current scientific story
of the origin of the universe...

...begins with an explosion
which made space itself expand.

About 15 billion years ago...

...all the matter and energy that
make up the observable universe...

...were concentrated into a space
smaller than the head of a pin.

The cosmos blew apart in one
inconceivably colossal explosion:

The big bang.

The stuff of the universe, together
with the fabric of space itself...

...began expanding in all directions
as they do today.

We can visualize this process
with a three-dimensional grid...

...attached to the expanding fabric
of space.

The early cosmos was
everywhere white-hot.

But as time passed,
the radiation expanded and cooled...

...and in ordinarily visible light,
space became dark as it is today.

But then little pockets of gas
began to grow.

Tendrils of gossamer clouds formed...

...colonies of great, lumbering,
slowly spinning things...

...steadily brightening,
each a kind of beast...

...composed of a hundred billion
shining points.

The largest recognizable structures
in the universe had formed.

We see them today. We ourselves
inhabit some lost corner of one.

We call them the galaxies.

We inhabit a universe of galaxies.

There are unstructured blobs,
the irregular galaxies...

...globular or elliptical galaxies...

...and the graceful blue arms
of spiral galaxies.

We've been investigating
the galaxies...

...their origins, evolution and
motions for less than a century.

These studies extend
our understanding...

...to the farthest reaches
of the universe.

Our ship of the imagination carries us
to that ultimate frontier.

We view the cosmos
on the grandest of scales.

The majesty of the galaxies
is revealed by science.

There are many different ways in which
stars are arrayed into galaxies.

When, by chance, the face of a spiral
galaxy is turned toward us...

...we see the spiral arms,
made luminous by billions of stars.

When, in other cases, the edge
of a galaxy is towards us...

...we see the central lanes
of gas and dust...

...from which the stars are forming.

In barred spirals,
a river of star stuff...

...extends through
the galactic center...

...connecting opposite spiral arms.

Elliptical galaxies come
in giant and dwarf sizes.

There are many mysterious galaxies...

...places where something has gone
terribly wrong...

...where there are
explosions and collisions...

...and streamers of gas and stars...

...bridges between the galaxies.

The galaxies look rigid, unmoving.

But we see them only for
a single frame of the cosmic movie.

Their parts are dissipating
and reforming...

...on a time scale of
hundreds of millions of years.

A galaxy is a fluid made
of billions of suns...

...all bound together by gravity.

These giant galactic forms exist
throughout the universe...

...and may be a common source
of wonderment and instruction...

...for billions of species
of intelligent life.

Their evolution is governed everywhere
by the same laws of physics.

We need a computer to illustrate...

...the collective motion
of so many stars...

...each under the gravitational
influence of all the others.

A billion years is here compressed
into a few seconds.

In some cases, spiral arms form
all by themselves.

In other cases...

...the close gravitational encounter
of two galaxies...

...will draw out spiral arms.

But when two nearby galaxies
collide...

...like a bullet through
a swarm of bees...

...the stars hardly collide at all.

But the shapes of the galaxies
can be severely distorted.

A direct collision of two galaxies can
last a hundred million years...

...and spill the constituent stars...

...careening through
intergalactic space.

When a dense, compact galaxy runs
into a larger one face-on...

...it can produce one of the loveliest
of the rare irregulars:

A ring galaxy.

Thousands of light-years across...

...a ring galaxy is set...

...against the velvet
of intergalactic space.

It's a temporary configuration
of disrupted stars...

...a splash in the cosmic pond.

Galaxies sometimes blow themselves up.

The quasars, probably billions
of light-years away...

...may be the colossal explosions
of young galaxies.

But we're not sure.

Quasars are a mystery still.

The galaxies reveal
a universal order, beauty...

...but also violence on a scale
never before imagined.

The universe seems neither
benign nor hostile...

...merely indifferent to the concerns
of such creatures as we.

Quasars may be monster versions
of rapidly rotating pulsars...

...or due to multiple collisions
of millions of stars...

...densely packed
in the galactic core...

...or a chain reaction of supernova
explosions in such a core.

Some astronomers think a quasar is
caused by millions of stars...

...falling into an immense black hole
in the core of a galaxy.

Something like a black hole...

...something very massive,
very dense and very small...

...is ticking and purring away...

...in the cores of nearby galaxies.

Even a well-behaved galaxy
like the Milky Way...

...has its stirrings and its dances.

The stars of the Milky Way move
with systematic grace.

The sun takes 250 million years...

...to go once around the core.

The outer provinces of the galaxy...

...revolve more slowly
than the inner regions.

As a result, gas and dust
pile up in spiral patterns.

These places of greater density
are where...

...young, hot, bright stars form...

...the stars which outline
the spiral arms.

These hot stars shine for only
10 million years or so...

...and then blow up.

But as the stars which outline
a spiral arm burn out...

...new, young stars are formed
from the debris just behind them...

...and the spiral pattern persists.

The sun, marked here with a circle...

...has been in and out
of spiral arms often...

...in the 20 times it has
gone around the Milky Way.

In this epoch, we live
at the edge of a spiral arm.

We've looked at internal galactic
motion on a small scale...

...across a million light-years
or less.

But the motion of the galaxies
themselves...

...across billions of light-years
is different.

That motion is a relic
of the big bang.

The key to cosmology,
the study of the entire universe...

...turns out to be
a commonplace of nature...

...an experience of everyday life.

Imagine a moving object
sending out waves.

It could be light waves...

(WHISTLE BLOWS)

...it could be sound waves,
it could be any kind of wave.

When that moving object passes us...

...we sense a change in pitch.

That's called the Doppler effect.

If you're the engineer in the cab...

...the pitch of the whistle
always sounds the same to you.

That's because you're moving along
with the source of the sound.

But if you're standing alongside
the track when the train passes...

...you hear that familiar
shift in pitch:

The Doppler shift.

The reason this happens
is easy to understand...

...once you visualize the waves.

A stationary train sends out
sound waves in perfect circles...

...like the ripples on a pond.

Let's start the train again.

Now, the waves spreading out ahead
of it get squashed together...

...and those spreading out behind it
get stretched apart.

The compressed waves have
a higher frequency or pitch...

...than the stretched-out waves.

The same thing is true
for light waves.

Color is to light
precisely what pitch is to sound.

Compressed light waves are made bluer.
They're blue-shifted.

Stretched-out light waves are
made redder. They're red-shifted.

At the speed of a train...

...you can sense the change of pitch
for sound, but not for light.

The train is traveling about
a million times too slow for that.

It turns out that the Doppler effect
for light waves...

...is the key to the cosmos.

The evidence for this was
gathered unexpectedly...

...by a former mule-team driver
who never went beyond the eighth grade.

During the second decade
of this century...

...the world's largest telescope was
being assembled on Mount Wilson...

...overlooking what were then
the clear skies of Los Angeles.

Large pieces of the telescope were
hauled to the mountaintop...

...a job for mule teams.

One of the drivers was
a young man named Milton Humason...

...the ne'er-do-well son
of a California banker.

But he was bright and naturally
curious about the equipment...

...he had carted up Mount Wilson.

And after the telescope was
completed in 1917...

...he managed to stay on here
as janitor and electrician.

One evening, so the story goes, the
observatory night assistant was ill.

Humason was asked to fill in.

Humason was a gambling man...

...celebrated for his skill at poker
and at the pool table.

But his touch with the telescope was
admired even more.

He discovered he had a talent
for using astronomical instruments.

He became the virtuoso
of the 100-inch telescope.

In this instrument,
light from distant galaxies...

...is focused on
a glass photographic plate...

...by a great encased mirror
100 inches across.

By the late 1920s, Humason was
making observations himself.

Mr. Nelson?

NELSON:
I'm in the coud� room, sir.

SAGAN: Humason by now had
his own night assistant...

...to help him with the observations.

HUMASON: Afternoon, Mr. Nelson.
-Good afternoon, Mr. Humason.

We'll start at 6.

I'll be making a spectrogram
at the Cassegrain focus.

Yes, sir.

SAGAN: The telescope must be able
to point with high accuracy...

...to a designated region of the sky,
and to keep on pointing there.

A machine weighing about 75 tons,
as massive as a locomotive...

...must move with a precision greater
than that of the finest pocket watch.

Everything must be checked
thoroughly.

The electrical power system
must work flawlessly.

Hours before observations are
to begin, the dome is opened...

...to allow the temperature inside
and outside to be equalized.

Humason prepared the sensitive
photographic emulsions...

...sheathed in their metal holders...

...to capture with
the giant telescope...

...the faint light
from remote galaxies.

This was part of
a systematic program...

...which Humason and his mentor,
the astronomer Edwin Hubble...

...were pursuing to measure
the Doppler shift...

...of light from the most distant
galaxies then known.

But the most distant galaxies are
very faint.

That's why even with the largest
telescope in the world...

...it was necessary to take very long
time exposures...

...often lasting all night...

...and sometimes requiring
several successive nights.

Humason would give the night assistant
the celestial coordinates...

...of the target galaxy.

Through the long, cold night,
he'd have to make fine adjustments...

...so the telescope would precisely
track the target galaxy.

The galaxy itself was too faint
to see through the telescope...

...although it could be recorded
photographically...

...with a long time exposure.

So the telescope would be pointed
at a nearby bright star...

...and then offset to
a featureless patch of sky...

...from which, over the long night...

...the light from the unseen galaxy
would slowly accumulate.

The telescope focused the faint
light from a galaxy...

...into the spectrometer...

...where it was spread out into
its rainbow of constituent colors.

The spectrum would be recorded on
the little glass plates.

Would you clamp in the drive and slue
to the focus star, please?

Are you clear?

NELSON: I'm going to slue to the east.
-Yes. I think I'm clear.

HUMASON:
Just take it easy.

All right, I have it.

Now, let's go to NGC 7-6-1-9.

I'm clear.

Going to do a 10-hour exposure.

What time is it?

7:15.

HUMASON:
Lights out, please.

The dark slide is open.

SAGAN: A large telescope views
only a tiny patch of sky.

As the Earth turns,
a guide star or a galaxy...

...would drift out of the telescope's
field of view in only a few minutes.

Humason had to stay awake,
tracking the galaxy...

...while elaborate machinery moved
the telescope...

...slowly in the opposite direction,
to compensate for Earth's rotation.

The telescope is a kind of clock.

HUMASON:
How's the dome?

You're clear.

SAGAN: This work was difficult,
routine, tedious...

...but although they
didn't yet know it...

...Hubble and Humason were
meticulously accumulating...

...the evidence for the big bang.

They had found that
the more distant the galaxy...

...the more its spectrum of colors was
shifted to the red.

HUMASON:
All right, clear the telescope.

I'm coming down now.

If this red shift were due to
the Doppler effect...

...the distant galaxies must be
running away from us.

At the end of his vigil...

...Humason would retrieve
the tiny galactic spectrum...

...and carefully carry it down
to be developed.

Thank you, Mr. Nelson.

I'm going to the darkroom now.

-Good day.
-Good day, sir.

In this way...

...Humason found a red shift
in almost every galaxy he examined...

...like the Doppler shift in
the sound of a receding locomotive.

And the farther away from us they
were, the faster they were receding.

Tied to the fabric of space,
the outward rushing galaxies...

...were tracing the expansion
of the universe itself.

An awesome conclusion had been
captured on these tiny glass slides.

Humason and Hubble had discovered
the big bang.

At top and bottom are
calibration lines...

...that Humason had
earlier photographed.

In the middle is the spectrum
of a relatively nearby galaxy.

Every element has a characteristic
spectral fingerprint...

...a set of frequencies
where light is absorbed.

Prominent here are
two dark lines in the violet...

...due to calcium
in the atmospheres...

...of the hundreds of billions
of stars...

...that constitute this galaxy.

Nearby galaxies show very little
Doppler shift.

But when he recorded the spectrum of
a fainter and more distant galaxy...

...he found the same
telltale pair of lines...

...but shifted farther right
toward the red.

And when he examined a remote galaxy
4 billion light-years away...

...he found the lines were
red-shifted even more.

This galaxy must be receding
at 200 million kilometers an hour.

The painstaking observations
of Milton Humason...

...astronomer and former
mule-team driver...

...established the expansion
of the universe.

In discussing the large-scale
structure of the cosmos...

...astronomers sometimes say
that space is curved...

...or that the universe is
finite but unbounded.

Whatever are they talking about?

Let's imagine that we are
perfectly flat...

...I mean, absolutely flat...

...and that we live,
appropriately enough, in Flatland...

...a land designed and named
by Edwin Abbott...

...a Shakespearean scholar
who lived in Victorian England.

Everybody in Flatland is,
of course, exceptionally flat.

We have squares, circles, triangles...

...and we all scurry about...

...and we can go into our houses
and do our flat business.

Now, we have width and length...

...but no height at all.

These cutouts have some height,
but let's ignore that.

Let's imagine that these
are absolutely flat.

That being the case, we know,
us Flatlanders...

...about left-right
and about forward-back...

...but we have never heard of up-down.

Let us imagine that into Flatland...

...hovering above it...

...comes a strange
three-dimensional creature...

...which, oddly enough,
looks like an apple.

The three-dimensional creature...

...sees an attractive
congenial-looking square...

...watches it enter its house...

...and decides in a gesture
of inter-dimensional amity...

...to say hello.

"Hello," says
the three-dimensional creature.

"How are you? I am a visitor
from the third dimension."

Well, the poor square looks around
his closed house...

...sees no one there...

...and what's more, has witnessed
a greeting coming from his insides:

A voice from within.

He surely is getting
a little worried about his sanity.

The three-dimensional creature...

...is unhappy about being considered
a psychological aberration...

...and so he descends to
actually enter Flatland.

Now, a three-dimensional creature
exists in Flatland only partially...

...only a plane, a cross section
through him can be seen.

So when the three-dimensional creature
first reaches Flatland...

...only its points of contact
can be seen.

And we'll represent that by stamping
the apple in this ink pad...

...and placing that image in Flatland.

And as the apple were
to descend through...

...slither by Flatland...

...we would progressively see
higher and higher slices...

...which we can represent...

...by cutting the apple.

So the square, as time goes on...

...sees a set of objects
mysteriously appear...

...from nowhere,
and inside a closed room...

...and change their shape
dramatically.

His only conclusion could be
that he's gone bonkers.

Well, the apple might be a little
annoyed at this conclusion...

...and so not such a friendly gesture
from dimension to dimension...

...makes a contact with
the square from below...

...and sends our flat creature...

...fluttering and spinning
above Flatland.

At first, the square has
no idea what's happening.

He's terribly confused. This is
utterly outside his experience.

But after a while, he comes
to realize...

...that he is seeing inside
closed rooms in Flatland.

He is looking inside
his fellow flat creatures:

He is seeing Flatland
from a perspective...

...no one has ever seen it before,
to his knowledge.

Getting into another dimension
provides, as an incidental benefit...

...a kind of x-ray vision.

Now our flat creature slowly
descends to the surface...

...and his friends rush up
to see him.

From their point of view, he has
mysteriously appeared from nowhere.

He hasn't walked from somewhere else.
He's come from some other place.

They say, "For heaven's sake,
what's happened to you?"

And the poor square has to say:

"Well, I was in some other
mystic dimension...

...called 'Up."'

And they will pat him on his side
and comfort him...

...or else they'll ask:

"Well, show us. Where is that
third dimension? Point to it."

And the poor square will be
unable to comply.

But maybe more interesting...

...is the other direction
in dimensionality.

What about the fourth dimension?

Now, to approach that,
let's consider a cube.

We can imagine a cube
in the following way:

Take a line segment and move it at
right angles to itself in equal length.

That makes a square.

Move that square in equal length
at right angles to itself...

...and you have a cube.

Now, this cube, we understand...

...casts a shadow.

And that shadow we recognize...

It's, you know, ordinarily drawn
in third-grade classrooms...

...as two squares with
their vertices connected.

If we look at a three-dimensional
object's shadow in two dimensions...

...we see that, in this case,
not all the lines appear equal.

Not all the angles are right angles.

The 3-D object hasn't been
perfectly represented...

...in its projection
in two dimensions.

But that's part of the cost of losing
a dimension in the projection.

Now, let's take this
three-dimensional cube...

...and project it, carry it through
a fourth physical dimension:

Not that way, not that way,
not that way.

But at right angles to
those three directions.

I can't show you that direction.

But imagine that there is
a fourth physical dimension.

In that case, we would generate
a four-dimensional hyper-cube...

...which is also called a tesseract.

I cannot show you a tesseract
because I and you...

...are trapped in three dimensions.

But what I can show you is
the shadow in three dimensions...

...of a four-dimensional hyper-cube
or tesseract.

This is it, and you can see
its two nested cubes...

...all the vertices connected
by lines.

And now the real tesseract
in four dimensions...

...would have all lines of equal
length and all angles right angles.

That's not what we see here,
but that's the penalty of projection.

So you see, while we cannot imagine
the world of four dimensions...

...we can certainly think about it
perfectly well.

Now, imagine a universe
just like Flatland...

...truly two-dimensional and entirely
flat in every direction.

But with one exception:

Unbeknownst to the inhabitants...

...their two-dimensional universe
is curved...

...into a third physical dimension.

Maybe into a sphere,
but at any rate...

...into something entirely outside
their experience.

Locally, their universe still looks
flat enough.

But if one of them,
much smaller and flatter than me...

...takes a very long walk along what
seems to be a straight line...

...he would uncover a great mystery.

Suppose he marked
his starting point here...

...and set off to explore
his universe.

He never turns around
and he never reaches an edge.

He doesn't know that
his apparently flat universe...

...is actually curved
into an enormous sphere.

He doesn't sense that he's
walking around a globe.

Why should his space be curved?

Because this universe has
so much matter...

...that it gravitationally
warps space...

...closing it back on itself
into a sphere.

But our Flatlander doesn't
know this.

After a long while, he'll find he
somehow returns to his starting point.

There must be a third dimension.

Our Flatlander couldn't imagine
a third dimension...

...but he could sure deduce it.

Increase all the dimensions
in this story by one...

...and you have something
like the situation...

...which many cosmologists think
may actually apply to us.

We are three-dimensional creatures
trapped in three dimensions.

We imagine our universe to be flat
in three dimensions...

...but maybe it's curved
into a fourth.

We can talk about a fourth physical
dimension, but we can't experience it.

No one can point to
the fourth dimension.

There's left-right and there's
forward-back. There's up-down...

...and there's some
other directions...

...simultaneously at right angles
to those familiar three dimensions.

Now, imagine this universe
is expanding.

If we blow it up like a four-
dimensional balloon, what happens?

An astronomer on a given galaxy...

...thinks all the other galaxies are
running away from him.

The more distant the galaxy,
the faster it seems to be moving.

This is just what
Humason and Hubble found.

On the surface of this curved universe,
there is no boundary or center.

The universe can be
both finite and unbounded.

The red shift of
the distant galaxies...

...seemed to imply to
Humason's contemporaries...

...that we were at the center
of an expanding universe...

...that our place in space was
somehow privileged.

But if the universe is expanding...

...whether or not it's curved
into a fourth dimension...

...observers on every galaxy will see
precisely the same thing:

All the galaxies rushing
away from them...

...as if they had made some dreadful
intergalactic social blunder.

If there's enough matter to close
the universe gravitationally...

...then it's wrapped in on itself
like a sphere.

If there isn't enough matter
to close the cosmos...

...then our universe has
an open shape...

...extending forever
in all directions.

This saddle universe is only one
of an infinite number...

...of possible kinds of
open universes.

Unlike such closed universes
as the sphere...

...open universes have in them
an infinite amount of space.

If our universe is,
in fact, closed off...

...then nothing can get out,
not matter, not light.

We would then be living inside
a black hole.

There is one possible
way out, though:

A hypothetical tunnel or wormhole
through the next higher dimension...

...a place sucking in
matter and light.

Can we find such a wormhole?
Could we survive the trip?

We might emerge in some other
place and time...

...perhaps in another universe...

...or perhaps somewhere else
in our own.

If you want to know what it's like
inside a black hole...

...look around.

But we don't yet know whether
the universe is open or closed.

More than that,
some astronomers doubt...

...that the red shift
of distant galaxies...

...is due to the Doppler effect.

They are skeptical about the expanding
universe and the big bang.

Perhaps our descendants will regard
our present ignorance...

...with as much sympathy as we feel
to the ancients...

...for not knowing whether the Earth
went around the sun.

If the general picture, however,
of a big bang...

...followed by an expanding universe
is correct...

...what happened before that?

Was the universe devoid
of all matter...

...and then the matter suddenly
somehow created?

How did that happen?

In many cultures,
the customary answer...

...is that a god or gods created
the universe out of nothing.

But if we wish to pursue
this question courageously...

...we must, of course,
ask the next question:

Where did God come from?

If we decide that this is
an unanswerable question...

...why not save a step and conclude...

...that the origin of the universe is
an unanswerable question?

Or if we say that God
always existed...

...why not save a step and conclude...

...that the universe always existed?

There's no need for a creation.
It was always here.

These are not easy questions.

Cosmology brings us face to face...

...with the deepest mysteries...

...with questions that were once
treated only in religion and myth.

"Who knows for certain?

Who shall here declare it?

Whence was it born?
Whence came creation?

The gods are later than
this world's formation.

Who then can know
the origins of the world?

None knows whence creation arose...

...or whether He has
or has not made it...

...He who surveys it
from the lofty skies.

Only He knows...

...or perhaps He knows not."

These words are 3500 years old.

They're taken from the Rig-Veda...

...a collection of early
Sanskrit hymns.

The most sophisticated ancient
cosmological ideas came from Asia...

...and particularly from India.

Here, there's a tradition
of skeptical questioning...

...and unselfconscious humility
before the great cosmic mysteries.

Amidst the routine of daily life...

...in, say, the harvesting
and winnowing of grain...

...people all over the world
have wondered:

Where did the universe come from?

Asking this question is
a hallmark of our species.

There's a natural tendency
to understand...

...the origin of the cosmos
in familiar biological terms.

The mating of cosmic deities...

...or the hatching of a cosmic egg...

...or maybe the intonation
of some magic phrase.

The big bang is our modern
scientific creation myth.

It comes from the same human need...

...to solve the cosmological riddle.

Most cultures imagined the world...

...to be only a few hundred
generations old.

Hardly anyone guessed that
the cosmos might be far older.

But the ancient Hindus did.

They, like every other society...

...noted and calibrated
the cycles in nature.

The rising and setting
of the sun and the stars...

...the phases of the moon...

...the passing of the seasons.

All over South India,
an age-old ceremony...

...takes place every January...

...a rejoicing in the
generosity of nature...

...in the annual harvesting
of the crops.

Every January, nature provides
the rice to celebrate Pongal.

Even the draft animals are given the
day off and garlanded with flowers.

(SPEAKING IN FOREIGN LANGUAGE)

Colorful designs are painted
on the ground to attract harmony...

...and good fortune
for the coming year.

Pongal, a simple porridge,
a mixture of rice and sweet milk...

...symbolizes the harvest,
the return of the seasons.

(SHOUTING)

However, this is not merely
a harvest festival.

It has ties to an elegant and
much deeper cosmological tradition.

The Pongal festival is
a rejoicing in the fact...

...that there are cycles in nature.

But how could such cycles come about
unless the gods will them?

And if there are cycles
in the years of humans...

...might there not be cycles
in the eons of the gods?

Hinduism is the only one
of the world's great faiths...

...dedicated to the idea
that the cosmos itself...

...undergoes an immense,
indeed, an infinite...

...number of deaths and rebirths.

It is the only religion in which
the time scales correspond...

...no doubt by accident, to those
of modern scientific cosmology.

Its cycles run from our
ordinary day and night...

...to a day and night of Brahma...

...8.64 billion years long...

...longer than the age
of the Earth or the sun...

...and about half the time
since the big bang.

And there are much longer
time scales still.

There is the deep
and appealing notion...

...that the universe is
but the dream of the god...

...who after 100 Brahma years...

...dissolves himself into
a dreamless sleep...

...and the universe
dissolves with him.

Until, after another
Brahma century, he stirs...

...recomposes himself
and begins again...

...to dream the great
cosmic lotus dream.

Meanwhile, elsewhere...

...there are an infinite number
of other universes...

...each with its own god...

...dreaming the cosmic dream.

These great ideas are
tempered by another...

...perhaps still greater.

It is said...

...that men may not be
the dreams of the gods...

...but rather that the gods...

...are the dreams of men.

In India, there are many gods...

...and each god has many
manifestations.

These Chola bronzes cast
in the 11th century...

...include several different
incarnations of the god Shiva...

...seen here at his wedding.

The most elegant and sublime
of these bronzes...

...is a representation of
the creation of the universe...

...at the beginning
of each cosmic cycle:

A motif known as
the cosmic dance of Shiva.

The god has four hands.

In the upper right hand is a drum...

...whose sound is
the sound of creation.

In the upper left hand
is a tongue of flame...

...a reminder that the universe,
now newly created...

...will, billions of years from now,
be utterly destroyed.

Creation, destruction.

These profound and lovely ideas...

...are central to ancient
Hindu beliefs...

...as exemplified in this
Chola temple at Darasuram.

They're a kind of premonition
of modern astronomical ideas.

Without doubt, the universe has been
expanding since the big bang...

...but it is, by no means, clear that
it will continue to expand forever.

If there is less than a certain
amount of matter in the universe...

...then the mutual gravitation
of the receding galaxies...

...will be insufficient
to stop the expansion...

...and the universe will
run away forever.

But if there is more matter
than we can see...

...hidden away in black holes, say...

...or in hot but invisible gas
between the galaxies...

...then the universe holds together...

...and partakes of a very Indian
succession of cycles...

...expansion followed
by contraction...

...cosmos upon cosmos,
universes without end.

If we live in such
an oscillating universe...

...the big bang is not
the creation of the cosmos...

...but merely the end
of the previous cycle...

...the destruction of the last
incarnation of the cosmos.

Neither of these modern cosmologies...

...may be altogether to our liking.

In one cosmology, the universe
is created somehow...

...from nothing
15 to 20 billion years ago...

...and expands forever...

...the galaxies mutually receding
until the last one...

...disappears over our cosmic horizon.

Then the galactic astronomers
are out of business...

...the stars cool and die,
matter itself decays...

...and the universe becomes...

...a thin, cold haze
of elementary particles.

In the other,
the oscillating universe...

...the cosmos has no beginning
and no end...

...and we are in the midst
of an infinite cycle...

...of cosmic deaths and rebirths
with no information...

...trickling through the cusps
of the oscillation.

Nothing of the galaxies,
stars, planets...

...life forms, civilizations...

...evolved in the previous
incarnation of the universe...

...trickles through the cusp...

...flitters past the big bang...

...to be known in our universe.

The death of the universe
in either cosmology...

...may seem a little depressing.

But we may take some solace
in the time scales involved.

These events will take tens
of billions of years or more.

Human beings, or our descendants,
whoever they might be...

...can do a great deal of good
in tens of billions of years...

...before the cosmos dies.

If the universe truly oscillates...

...if the modern scientific version
of the old Hindu cosmology is valid...

...then still stranger
questions arise.

Some scientists think
that when a red shift...

...is followed by blue shift...

...causality will be inverted...

...and effects will precede causes.

First, the ripples spread out...

...from a point
on the water's surface.

Then I throw the stone into the pond.

Some scientists wonder,
in an oscillating universe...

...about what happens at the cusps...

...at the transition from
contraction to expansion.

Some think that the laws of nature
are then randomly reshuffled...

...that the physics and chemistry
we have in this universe...

...represent only one
of an infinite range...

...of possible natural laws.

It is easy to see...

...that only a restricted range
of laws of nature...

...are consistent with galaxies
and stars, planets...

...life and intelligence.

If the laws of nature are...

...randomly reshuffled at the cusps...

...then it is only the most
extraordinary coincidence...

...that the cosmic slot machine
has this time come up...

...with a universe
consistent with us.

Do we live in a universe
which expands forever...

...or in one where there is
a nested set of infinite cycles?

There's a way to find out
the answer...

...not by mysticism,
but through science...

...by making an accurate census...

...of the total amount of matter
in the universe...

...or by seeing to the very edge
of the cosmos.

Radio telescopes are able to
detect distant quasars...

...billions of light-years away...

...expanding with
the fabric of space.

By looking far out into space...

...we are also looking
far back into time...

...back toward the horizon
of the universe...

...back toward the epoch
of the big bang.

Radio telescopes have
even detected...

...the cosmic background radiation.

The fires of the big bang
cooled and red-shifted...

...faintly echoing down
the corridors of time.

This is the very large array...

...a collection of 17 separate
radio telescopes...

...all working collectively...

...in a remote region of New Mexico.

Modern radio telescopes are
exquisitely sensitive.

A distant quasar is so faint...

...that its received radiation
by some such telescope...

...amounts to maybe
a quadrillionth of a watt.

In fact, and this is a reasonably
stunning piece of information...

...the total amount of energy
ever received...

...by all the radio telescopes
on the planet Earth...

...is less than the energy
of a single snowflake...

...striking the ground.

In detecting the cosmic
background radiation...

...in counting quasars...

...in searching for intelligent
signals from space...

...radio astronomers are dealing
with amounts of energy...

...which are barely there at all.

These radio telescopes,
rising like giant flowers...

...from the New Mexico desert...

...are monuments to human ingenuity.

The faint radio waves
are collected, focused...

...assembled and amplified,
and then converted...

...into pictures of nebulae,
galaxies and quasars.

If you had eyes that
worked in radio light...

...they'd probably be bigger
than wagon wheels...

...and this is the universe you'd see.

An elliptical galaxy, for example...

...leaving behind it a long wake
glowing in radio waves.

Radio waves reveal
a universe of quasars...

...interacting galaxies,
titanic explosions.

Every time we use another kind
of light to view the cosmos...

...we open a new door of perception.

As the murmurs from the edge
of the cosmos slowly accumulate...

...our understanding grows.

This is an exploration of
the ancient and the invisible...

...a continuing human inquiry...

...into the grand cosmological
questions.

Another important recent finding...

...was made by x-ray observatories
in Earth orbit.

Artificial satellites launched
to view the sky...

...not in ordinary visible light,
not in radio waves...

...but in x-ray light.

There seems to be an immense cloud...

...of extremely hot hydrogen...

...glowing in x-rays between
some galaxies.

Now, if this amount of
intergalactic matter...

...were typical of all
clusters of galaxies...

...then there may be just enough
matter to close the cosmos...

...and to trap us forever
in an oscillating universe.

If the cosmos is closed...

...there's a strange, haunting,
evocative possibility...

...one of the most exquisite
conjectures in science or religion.

It's entirely undemonstrated...

...it may never be proved,
but it's stirring.

Our entire universe, to the
farthest galaxy, we are told...

...is no more than
a closed electron...

...in a far grander universe
we can never see.

That universe is only
an elementary particle...

...in another still greater
universe and so on forever.

Also, every electron
in our universe, it is claimed...

...is an entire miniature cosmos...

...containing galaxies and stars
and life and electrons.

Every one of those electrons
contains a still smaller universe...

...an infinite regression
up and down.

Every human generation has asked...

...about the origin
and fate of the cosmos.

Ours is the first generation
with a real chance...

...of finding some of the answers.

One way or another...

...we are poised at
the edge of forever.

Except for planetary exploration,
the study of galaxies and cosmology...

...what this episode was about, have
undergone the greatest advances...

...since Cosmos was first broadcast.

For one thing, at last we have
a good photograph...

...of our own Milky Way galaxy...

...about 100,000 light-years across.

Here it is.

It was taken by
NASA's Coby satellite.

We see it edge on, of course,
since we're embedded...

...in the plane of the galaxy.

But you don't need
a spacecraft to see it.

If it's a clear night,
why not go out and take a look...

...at the Milky Way?

There's also new evidence
suggesting...

...that the Milky Way is not so much
an ordinary spiral galaxy...

...as a barred spiral, like this.

Important work has now been done
on mapping...

...how the galaxies are scattered
through intergalactic space.

To the surprise of
a lot of scientists...

...on a scale of hundreds
of millions of light-years...

...the galaxies turn out
not to be strewn at random...

...or concentrated in clusters
of galaxies...

...but instead, strung out...

...along odd, irregular surfaces,
like this.

Every dot in this computer animation...

...is a galaxy.

The computer lets us look at this
distribution of galaxies...

...from many points of view...

...but this is how it looks
from the Earth.

There is an odd mannequin shape...

...that is presented by
the distribution of galaxies.

This work has been done...

...mainly by Margaret Geller...

...with her collaborator
John Huchra...

...at Harvard University
and the Smithsonian Institution.

It's a little like soap bubbles
in a bathtub...

...or dishwashing detergent.

The galaxies are on the surfaces
of the bubbles.

The insides of the bubbles seem
to have no galaxies in them at all.

An average bubble is about
100 million light-years across.

And that means that we've mapped
still only...

...a very small volume
of the accessible universe...

...the galaxies nearest to us.

But pretty soon, we should be able to
extend this search out...

...to enormous distances...

...so far away in space,
that we're looking...

...back to the time that galaxies
and their structures...

...were first formed.

And this poses a real problem.

Most cosmologists hold
that the galaxies arise from...

...a preexisting lumpiness
in the early universe...

...with the little lumps
growing into galaxies.

But the background radiation
from the big bang...

...that fills all of space...

...has now been carefully measured...

...by that same Coby satellite
that took that picture.

Now, those radio waves seem almost
perfectly uniform...

...across the sky...

...as if the big bang weren't
lumpy or granular at all.

But if early radiation and matter
in the universe weren't lumpy...

...how could individual galaxies form?

How could the bubbles form?

Is there a contradiction...

...between the uniformity
of the big bang radio waves...

...and the bubble structures
formed by the galaxies?

That's the question.

When our survey of galaxies reaches
out to billions of light-years...

...we'll have the answer
to this question.

Incidentally, maybe you're thinking...

...that the bubbles imply
a bubble maker.

But then I'd have to ask you:

"Who made the bubble maker?"

There's another infinite regress
lurking here.

And to one of
the grandest questions...

...whether there's enough matter
in the universe to close it...

...the only fair answer is
that we don't know.

If it is closed...

...what is the hidden matter
that's closing it?

Is it faint stars, black holes,
massive neutrinos...

...some exotic kind of dark matter
unknown on Earth?

We don't know.

But there are reasons to think
that we'll soon find out the answers.