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Cosmos (1980): Season 1, Episode 13 - Who Speaks for Earth? - full transcript

Carl Sagan considers the significance of science and discuss the importance of human survival in the nuclear age.


NARRATOR: "I call Heaven and Earth
to witness against you this day...

...that I have set before thee
life and death...

...the blessing and the curse.

Therefore choose life,
that thou mayest live...

...thou and thy seed."

SAGAN: Nearly 200 years ago,
in the Gulf of Alaska...

...at a place called Lituya Bay...

...two cultures that had never
met experienced a first encounter.

The Tlingit people...

...lived more or less as their
ancestors had for thousands of years.

They were nomads...

...moving often by canoe
between numerous campsites...

...where they caught plentiful
fish and sea otters...

...and traded with neighboring tribes.

(SPEAKS IN TLINGIT)

The creator they worshiped
was the raven god...

...whom they pictured as an enormous
black bird with white wings.

And one July day in 1786...

...the raven god appeared.

The Tlingit were terrified.

They knew that anyone looking directly
at the god would be turned to stone.

From the other side of the planet
had come an expedition...

...led by the French
explorer La Prouse.

It was the most elaborately planned
scientific voyage of the century...

...sent around the world to gather
knowledge about the geography...

...natural history and peoples
of distant lands.

But to the Tlingit...

...whose world was confined to the
islands and inlets of south Alaska...

...this great vessel could have
come only from the gods.

There was one among them who
dared to look more deeply.

He was an old warrior,
and nearly blind.

He said that his life
was almost over.

For the common good, he would
approach the raven...

...to learn whether the god really
would turn his people to stone.

He set out on his own
voyage of discovery...

...to confront the end of the world.

The old man made himself
look hard at the raven...

...and saw that it was not a
great bird from the sky...

...but the work of men like himself.

This first encounter turned
out to be peaceful.

Men of the La Prouse expedition
were under orders...

...to treat with respect
any people they might discover.

An exceptional policy
for its time, and after.

La Prouse and the Tlingit
exchanged goods...

...and then the strange ship
sailed away, never to return.

Not all encounters between nations
had been so peaceful.

Before 1519...

...the Aztecs of Mexico had
never seen a gun.

They too believed at first
that their strange visitors...

...had come from the sky.

The Spaniards under Cortez...

...were not constrained by
any injunctions against violence.

Their true nature and intentions
soon became clear.

Unlike the La Prouse expedition...

...the Conquistadors sought,
not knowledge, but gold.

They used their superior weapons
to loot and murder.

In their madness, they
obliterated a civilization.

In the name of piety...

...in a mockery of their religion...

...the Spaniards utterly
destroyed a society...

...with an art, astronomy,
and architecture...

...the equal of anything in Europe.

We revile the Conquistadors for their
cruelty and shortsightedness...

...for choosing death.

We admire La Prouse and the Tlingit
for their courage and wisdom...

...for choosing life.

The choice is with us still.

But the civilization now in
jeopardy is all humanity.

As the ancient mythmakers knew...

...we're children equally
of the Earth and sky.

In our tenure on this planet...

...we've accumulated dangerous
evolutionary baggage:

Propensities for
aggression and ritual...

...submission to leaders,
hostility to outsiders.

All of which puts our
survival in some doubt.

But we've also acquired
compassion for others...

...love for our children...

...a desire to learn from
history and experience...

...and a great, soaring,
passionate intelligence.

The clear tools for our continued
survival and prosperity.

Which aspects of our nature
will prevail...

...is uncertain.

Particularly when our visions and
prospects are bound...

...to one small part of
the small planet Earth.

But up there in the cosmos...

...an inescapable perspective awaits.

National boundaries are not evident
when we view the Earth from space.

Fanatic ethnic or religious
or national identifications...

...are difficult to support...

...when we see our planet
as a fragile blue crescent...

...fading to become an inconspicuous
point of light...

...against the bastion and citadel
of the stars.

There are not yet obvious signs of
extraterrestrial intelligence...

...and this makes us wonder whether
civilizations like ours...

...rush inevitably, headlong
to self-destruction.

I dream about it.

And sometimes they're bad dreams.

In the vision of a dream...

...I once imagined myself...

...searching for other civilizations
in the cosmos.

Among a hundred billion galaxies...

...and a billion trillion stars...

...life and intelligence should
have arisen on many worlds.

Some worlds are barren
and desolate...

...on them life never began...

...or may have been extinguished
in some cosmic catastrophe.

There may be worlds rich in life...

...but not yet evolved to
intelligence and high technology.

There may be civilizations
that achieve technology...

...and then promptly use it
to destroy themselves.

And perhaps
there are also beings...

...who learned to live with their
technology and themselves.

Beings who endure...

...and become citizens of the cosmos.

Immersed in these thoughts...

...I found myself approaching
a world that was clearly inhabited...

...a world I had visited before.

I saw a planet encompassed by light...

...and recognized the signature
of intelligence.

But suddenly...

...darkness, total and absolute.

In my dream...

...I could read the Book of Worlds.

A vast encyclopedia...

...of a billion planets
within the Milky Way.

What could the computer tell me...

...about this now-darkened world?

They must have survived
some earlier catastrophe.

Locally initiated contact:

Maybe their television broadcasts.

Their biology was different
from ours.

High technology.

I wondered what those
lights had been for.

There must have been
signs of trouble.

Probability of survival
in a century...

...less than 1%. Not very good odds.

"Communications interrupted."

Their world society had failed.

They had made the ultimate mistake.

I felt a longing
to return to Earth.

The television transmissions
of Earth rushed past me...

...expanding away from our planet
at the speed of light.

(RANDOM TELEVISION AUDIO PLAYS)

ANNOUNCER 1: The nuclear test-ban
treaty was signed today.

ANNOUNCER 2: Something's happened
in the motorcade. Stand by.

ANNOUNCER 3:
For 64,000 dollars...

ANNOUNCER 4:... bombing of Hanoi was
designed to cripple morale...

NIXON: There can be no whitewash
at the White House.

ANNOUNCER 5:... series of record oil
company profits were revealed...

ANNOUNCER 6:... if the serious course
of events continued.

Foreign ministers are at this moment...

Please stand by.

Stand by.

SAGAN:
Then, suddenly...

...silence...

...total and absolute.

But the dream was not yet done.

Had we destroyed our home?

What had we done to the Earth?

There had been many ways
for life to perish at our hands.

We had poisoned the air and water.

We had ravaged the land.

Perhaps we had changed the climate.

Could it have been a plague...

...or nuclear war?

I remembered the galactic computer.

What would it say about the Earth?

There was our region of the galaxy.

There was our world.

I had found the entry for Earth.

Humanity, third from the sun.

They had heard our
television broadcasts...

...and thought them an application
for cosmic citizenship.

Our technology had been
growing enormously.

They got that right.

200 nation states.

About six global powers.

The potential to become one planet.

Probability of survival over
a century, here also...

...less than l% .

So it was nuclear war.

A full nuclear exchange.

There would be no more
big questions.

No more answers.

Never again a love or a child.

No descendants to remember us
and be proud.

No more voyages to the stars.

No more songs from the Earth.

I saw East Africa...

...and thought a few
million years ago...

...we humans took our
first steps there.

Our brains grew and changed.

The old parts began to be
guided by the new parts.

And this made us human...

...with compassion and foresight
and reason.

But instead, we listened to that
reptilian voice within us...

...counseling fear, territoriality...

...aggression.

We accepted the products of science.

We rejected its methods.

Maybe the reptiles will evolve
intelligence once more.

Perhaps, one day, there will be
civilizations again on Earth.

There will be life.

There will be intelligence.

But there will be no more humans.

Not here, not on a billion worlds.

Every thinking person
fears nuclear war...

...and every technological nation
plans for it.

Everyone knows it's madness...

...and every country has an excuse.

There's a dreary chain of causality.

The Germans were
working on the bomb...

...at the beginning of World War II.

So the Americans
had to make one first.

If the Americans had one,
the Russians had to have one.

Then, the British, the French...

...the Chinese, the Indians,
the Pakistanis.

Many nations now collect
nuclear weapons.

They're easy to make.

You can steal fissionable material
from nuclear reactors.

Nuclear weapons have almost become
a home handicraft industry.

The conventional bombs of World War II
were called "blockbusters."

Filled with 20 tons of TNT, they
could destroy a city block.

All the bombs dropped on all the
cities of World War II...

...amounted to some
2 million tons of TNT.

Two megatons.

Coventry and Rotterdam.

Dresden and Tokyo.

All the death that rained
from the skies...

...between 1939 and 1945.

100,000 blockbusters.
Two megatons.

Today, two megatons is the equivalent
of a single thermonuclear bomb.

One bomb with the destructive force...

...of the Second World War.

But there are tens of thousands
of nuclear weapons.

The missile and bomber forces
of the Soviet Union and U. S...

...have warheads aimed at over
15,000 designated targets.

No place on the planet is safe.

The energy contained
in these weapons...

...genies of death...

...patiently awaiting
the rubbing of the lamps...

...totals far more than
10,000 megatons.

But with the destruction
concentrated efficiently...

...not over six years,
but over a few hours.

A blockbuster for every family
on the planet.

A World War II every second...

...for the length of a lazy afternoon.

(BIRDS CHIRPING)

The bomb dropped on Hiroshima...

...killed 70,000 people.

In a full nuclear exchange...

...in the paroxysm of global death...

...the equivalent of
a million Hiroshima bombs...

...would be dropped all
over the world.

In such an exchange
not everyone would be...

...killed by the blast and firestorm
and the immediate radiation.

There would be other agonies:

Loss of loved ones...

...the legions of the burned and
blinded and mutilated...

...the absence of medical care...

...disease, plague...

...long-lived radiation poisoning
of the soil and the water.

The threat of tumors and stillbirths
and malformed children.

And the hopeless sense of
a civilization destroyed for nothing.

The knowledge that we could have
prevented it and did not.

The global balance of terror...

...pioneered by the U.S.
and the Soviet Union...

...holds hostage
all the citizens of the Earth.

Each side persistently probes...

...the limits of
the other's tolerance...

...like the Cuban missile crisis...

...the testing of
anti-satellite weapons...

...the Vietnam and Afghanistan wars.

The hostile military
establishments are...

...locked in some ghastly
mutual embrace.

Each needs the other.

But the balance of terror
is a delicate balance...

...with very little margin
for miscalculation.

And the world impoverishes
itself by spending...

...a trillion dollars a year
on preparations for war.

And by employing perhaps...

...half the scientists and high
technologists on the planet...

...in military endeavors.

How would we explain all this...

...to a dispassionate
extraterrestrial observer?

What account would we give
of our stewardship...

...of the planet Earth?

We have heard the rationales
offered by the superpowers.

We know who speaks
for the nations.

But who speaks
for the human species?

Who speaks for Earth?

From an extraterrestrial perspective,
our global civilization is...

...clearly on the edge of failure...

...in the most important task it faces:

Preserving the lives and well-being
of its citizens...

...and the future habitability
of the planet.

But if we're willing to live with the
growing likelihood of nuclear war...

...shouldn't we also be willing
to explore vigorously...

...every possible means to
prevent nuclear war?

Shouldn't we consider,
in every nation...

...major changes in the traditional
ways of doing things?

A fundamental restructuring...

...of economic, political,
social and religious institutions?

We've reached a point where
there can be no more...

...special interests or cases.

Nuclear arms threaten every
person on Earth.

Fundamental changes in society
are sometimes labeled...

...impractical or contrary
to human nature...

...as if nuclear war were practical...

...or as if there were only
one human nature.

But fundamental changes can
clearly be made.

We're surrounded by them.

In the last two centuries,
abject slavery...

...which was with us for
thousands of years...

...has almost entirely
been eliminated...

...in a stirring
worldwide revolution.

Women, systematically mistreated
for millennia...

...are gradually gaining the political
and economic power...

...traditionally denied to them.

And some wars of aggression have
recently been stopped or curtailed...

...because of a revulsion...

...felt by the people in
the aggressor nations.

The old appeals...

...to racial, sexual,
and religious chauvinism...

...and to rabid nationalist fervor...

...are beginning not to work.

A new consciousness is developing
which sees the Earth as...

...a single organism...

...and recognizes that an organism
at war with itself...

...is doomed.

We are one planet.

One of the great revelations of
the age of space exploration...

...is the image of the Earth,
finite and lonely...

...somehow vulnerable, bearing
the entire human species...

...through the oceans
of space and time.

But this is an ancient perception.

In the 3rd century B. C...

...our planet was mapped and
accurately measured...

...by a Greek scientist named
Eratosthenes, who worked in Egypt.

This was the world as he knew it.

Eratosthenes was the director...

...of the great Library
of Alexandria...

...the center of science and learning
in the ancient world.

Aristotle had argued that humanity
was divided into Greeks...

...and everybody else,
who he called "barbarians"...

...and that the Greeks should keep
themselves racially pure.

He taught that it was fitting for
the Greeks to enslave other peoples.

But Eratosthenes criticized Aristotle
for his blind chauvinism.

He believed there was good and bad
in every nation.

The Greek conquerors had invented
a new god for the Egyptians...

...but he looked remarkably Greek.

Alexander was portrayed as pharaoh...

...in a gesture to the Egyptians.

But in practice, the Greeks were
confident of their superiority.

The protests of the librarian hardly
constituted a serious challenge...

...to prevailing prejudices.

Their world was as imperfect
as our own.

But the Ptolemies, the Greek kings of
Egypt who followed Alexander...

...had at least this virtue:

They supported the advancement
of knowledge.

Popular ideas about the nature of
the cosmos were challenged...

...and some of them, discarded.

New ideas were proposed...

...and found to be in
better accord with the facts.

There were imaginative proposals,
vigorous debates...

...brilliant syntheses.

The resulting treasure
of knowledge...

...was recorded and preserved
for centuries...

...on these shelves.

Science came of age
in this library.

The Ptolemies didn't merely
collect old knowledge.

They supported scientific research
and generated new knowledge.

The results were amazing.

Eratosthenes accurately calculated
the size of the Earth.

He mapped it...

...and he argued that it could be
circumnavigated.

Hipparchus anticipated that
stars come into being...

...slowly move during the course
of centuries...

...and eventually perish.

It was he who first catalogued...

...the positions and magnitudes
of the stars...

...in order to determine whether
there were such changes.

Euclid produced a textbook
on geometry...

...which human beings learned from
for 23 centuries.

It's still a great read, full
of the most elegant proofs.

Galen wrote basic works on
healing and anatomy...

...which dominated medicine
until the Renaissance.

These are just a few examples.

There were dozens of
great scholars here...

...and hundreds of fundamental
discoveries.

Some of those discoveries have
a distinctly modern ring.

Apollonius of Perga studied
the parabola and the ellipse...

...curves that we know today describe
the paths of falling objects...

...in a gravitational field...

...and space vehicles traveling
between the planets.

Heron of Alexandria invented
steam engines and gear trains...

...he was the author of
the first book on robots.

Imagine how different our world
would be if those discoveries...

...had been used
for the benefit of everyone.

If the humane perspective
of Eratosthenes...

...had been widely
adopted and applied.

But this was not to be.

Alexandria was the greatest city...

...the Western world had ever seen.

People from all nations came here...

...to live, to trade, to learn.

On a given day...

...these harbors were thronged...

...with merchants and scholars,
tourists.

It's probably here...

...that the word "cosmopolitan"
realized its true meaning...

...of a citizen,
not just of a nation...

...but of the cosmos.

To be a citizen of the cosmos.

Here were clearly the seeds
of our modern world.

But why didn't they
take root and flourish?

Why, instead, did the West slumber
through 1000 years of darkness...

...until Columbus and Copernicus
and their contemporaries...

...rediscovered the work done here?

I cannot give you a simple answer...

...but I do know this:

There is no record in the entire
history of the library...

...that any of the illustrious scholars
and scientists who worked here...

...ever seriously challenged...

...a single political or economic
or religious assumption...

...of the society in which they lived.

The permanence of the stars
was questioned.

The justice of slavery was not.

Science and learning in general...

...were the preserve
of the privileged few.

The vast population of this city
had not the vaguest notion...

...of the great discoveries being
made within these walls.

How could they?

The new findings were not
explained or popularized.

The progress made here
benefited them little.

Science was not part of their lives.

The discoveries in mechanics, say...

...or steam technology...

...mainly were applied to
the perfection of weapons...

...to the encouragement
of superstition...

...to the amusement of kings.

Scientists never seemed to grasp
the enormous potential...

...of machines to free people...

...from arduous and repetitive labor.

The intellectual achievements
of antiquity...

...had few practical applications.

Science never captured
the imagination of the multitude.

There was no counterbalance
to stagnation, to pessimism...

...to the most abject surrender
to mysticism.

So when, at long last...

...the mob came
to burn the place down...

...there was nobody to stop them.

Let me tell you about the end.

It's a story about the last
scientist to work in this place.

A mathematician, astronomer,
physicist...

...and head of the school of Neo-
Platonic philosophy in Alexandria.

That's an extraordinary range
of accomplishments...

...for any individual, in any age.

Her name was Hypatia.

She was born in this city
in the year 370 A.D.

This was a time when women
had essentially no options.

They were considered property.

Nevertheless, Hypatia was able
to move freely...

...unselfconsciously...

...through traditional male domains.

By all accounts,
she was a great beauty.

And although she had many suitors...

...she had no interest in marriage.

The Alexandria of Hypatia's time,
by then long under Roman rule...

...was a city in grave conflict.

Slavery, the cancer
of the ancient world...

...had sapped classical civilization
of its vitality.

The growing Christian Church was...

...consolidating its power...

...and attempting to eradicate
pagan influence and culture.

Hypatia stood at the focus...

...at the epicenter
of mighty social forces.

Cyril, the Bishop of Alexandria,
despised her...

...in part because of her close
friendship with a Roman governor...

...but also because she was a symbol
of learning and science...

...which were largely identified
by the early Church with paganism.

In great personal danger...

...Hypatia continued to teach
and to publish...

...until, in the year 415 A.D.,
on her way to work...

...she was set upon...

...by a fanatical mob of
Cyril's followers.

They dragged her from her chariot...

...tore off her clothes...

...and flayed her flesh
from her bones...

...with abalone shells.

Her remains were burned,
her works obliterated...

...her name forgotten.

Cyril was made a saint.

The glory you see around me...

...is nothing but a memory.

It does not exist.

The last remains of the
library were destroyed...

...within a year of Hypatia's death.

It's as if an entire
civilization had undergone...

...a sort of self-inflicted
radical brain surgery...

...so that most of its memories...

...discoveries, ideas and passions...

...were irrevocably wiped out.

The loss was incalculable.

In some cases, we know only...

...the tantalizing titles of books
that had been destroyed.

In most cases, we know neither
the titles nor the authors.

We do know that in this library...

...there were 123 different
plays by Sophocles...

...of which only seven have
survived to our time.

One of those seven is Oedipus Rex.

Similar numbers apply
to the lost works of...

...Aeschylus, Euripides, Aristophanes.

It's a little as if the only
surviving works of a man named...

...William Shakespeare...

...were Coriolanus
and A Winter's Tale...

...although we knew he had
written some other things...

...which were
highly prized in his time.

Plays called Hamlet, Macbeth...

...A Midsummer's Night Dream,
Julius Caesar, King Lear...

...Romeo and Juliet.

History is full of people...

...who, out of fear or ignorance...

...or the lust for power...

...have destroyed treasures
of immeasurable value...

...which truly belong to all of us.

We must not let it happen again.

We have considered
the destruction of worlds...

...and the end of civilizations.

But there is another perspective
by which to measure human endeavors.

Let me tell you a story
about the beginning.

Some 15 billion years ago...

...our universe began...

...with the mightiest explosion
of all time.

The universe expanded,
cooled and darkened.

Energy condensed into matter,
mostly hydrogen atoms.

And these atoms accumulated
into vast clouds...

...rushing away from each other...

...that would one day become
the galaxies.

Within these galaxies the first
generation of stars was born...

...kindling the energy
hidden in matter...

...flooding the cosmos with light.

Hydrogen atoms had made
suns and starlight.

There were in those times
no planets to receive the light...

...and no living creatures to admire
the radiance of the heavens.

But deep in the stellar furnaces...

...nuclear fusion was creating
the heavier atoms:

Carbon and oxygen,
silicon and iron.

These elements, the ash left
by hydrogen...

...were the raw materials from which
planets and life would later arise.

At first, the heavy elements were
trapped in the hearts of the stars.

But massive stars soon
exhausted their fuel...

...and in their death throes...

...returned most of their substance
back into space.

The interstellar gas became
enriched in heavy elements.

In the Milky Way galaxy...

...the matter of the cosmos was recycled
into new generations of stars...

...now rich in heavy atoms.

A legacy from
their stellar ancestors.

And in the cold
of interstellar space...

...great turbulent clouds were
gathered by gravity...

...and stirred by starlight.

In their depths...

...the heavy atoms condensed into
grains of rocky dust and ice...

...and complex
carbon-based molecules.

In accordance with the laws
of physics and chemistry...

...hydrogen atoms had brought forth
the stuff of life.

In other clouds, more massive
aggregates of gas and dust...

...formed later generations of stars.

As new stars were formed...

...tiny condensations of matter
accreted near them...

...inconspicuous motes of
rock and metal, ice and gas...

...that would become the planets.

And on these worlds,
as in interstellar clouds...

...organic molecules formed...

...made of atoms that had been
cooked inside the stars.

In the tide pools and oceans
of many worlds...

...molecules were destroyed by
sunlight and assembled by chemistry.

One day, among these
natural experiments...

...a molecule arose, that,
quite by accident...

...was able to make crude copies
of itself.

As time passed, self-replication
became more accurate.

Those molecules that copied better...

...produced more copies.

Natural selection was underway.

Elaborate molecular machines
had evolved.

Slowly, imperceptibly, life had begun.

Collectives of organic molecules
evolved into one-celled organisms.

These produced multi-celled colonies.

Their various parts became
specialized organs.

Some colonies attached themselves
to the sea floor...

...others swam freely.

Eyes evolved, and now the cosmos
could see.

Living things moved on
to colonize the land.

The reptiles held sway for a time...

...but gave way to small warm-blooded
creatures with bigger brains...

...who developed dexterity and
curiosity about their environment.

They learned to use tools and
fire and language.

Star stuff,
the ash of stellar alchemy...

...had emerged into consciousness.

We are a way for the cosmos
to know itself.

We are creatures of the cosmos...

...and have always hungered
to know our origins...

...to understand our connection
with the universe.

How did everything come to be?

Every culture on the planet
has devised its own response...

...to the riddle
posed by the universe.

Every culture celebrates
the cycles of life and nature.

There are many different ways
of being human.

But an extraterrestrial visitor...

...examining the differences
among human societies...

...would find those
differences trivial...

...compared to the similarities.

We are one species.

We are star stuff,
harvesting starlight.

Our lives, our past and our future...

...are tied to the sun, the moon
and the stars.

Our ancestors knew that
their survival depended...

...on understanding the heavens.

They built observatories
and computers...

...to predict the changing of the
seasons by the motions in the skies.

We are, all of us...

...descended from astronomers.

The discovery of order
in the universe...

...of the laws of nature...

...is the foundation on which
science builds today.

Our conception of the cosmos...

...all of modern science
and technology...

...trace back to questions
raised by the stars.

Yet, even 400 years ago...

...we still had no idea
of our place in the universe.

The long journey to
that understanding...

...required both an unflinching
respect for the facts...

...and a delight
in the natural world.

Johannes Kepler wrote:

"We do not ask for what useful
purpose the birds do sing...

...for song is their pleasure
since they were created for singing.

Similarly...

...we ought not to ask why the
human mind troubles to fathom...

...the secrets of the heavens.

The diversity of the phenomena
of nature is so great...

...and the treasures hidden
in the heavens so rich...

...precisely in order...

...that the human mind shall never
be lacking in fresh nourishment."

It is the birthright
of every child...

...to encounter the cosmos anew...

...in every culture and every age.

When this happens to us,
we experience a deep sense of wonder.

The most fortunate among
us are guided by teachers...

...who channel this exhilaration.

We are born
to delight in the world.

We are taught to distinguish
our preconceptions from the truth.

Then, new worlds are discovered...

...as we decipher the mysteries
of the cosmos.

Science is a collective enterprise...

...that embraces many cultures
and spans the generations.

In every age, and sometimes
in the most unlikely places...

...there are those who wish
with a great passion...

...to understand the world.

We don't know where
the next discovery will come from.

What dream of the mind's eye
will remake the world.

These dreams begin
as impossibilities.

Once, even to see a planet through
a telescope was an astonishment.

But we studied these worlds...

...we figured out how
they moved in their orbits...

...and soon we were planning
voyages of discovery...

...beyond the Earth...

...and sending robot explorers
to the planets and the stars.

We humans long to be connected
with our origins...

...so we create rituals.

Science is another way
to express this longing.

It also connects us
with our origins.

And it, too, has its rituals
and its commandments.

Its only sacred truth is that
there are no sacred truths.

Temperature systems...

SAGAN: All assumptions must
be critically examined.

Arguments from authority
are worthless.

FEMALE SCIENTIST:
Transducer power is on.

SAGAN: Whatever is inconsistent
with the facts...

...no matter how
fond of it we are...

...must be discarded or revised.

Science is not perfect.

It's often misused.

It's only a tool.

But it's the best tool we have...

...self-correcting, ever-changing...

...applicable to everything.

With this tool,
we vanquish the impossible.

With the methods of science...

...we have begun
to explore the cosmos.

For the first time,
scientific discoveries...

...are widely accessible.

Our machines...

...the products of science...

...are now beyond
the orbit of Saturn.

A preliminary spacecraft
reconnaissance...

...has been made of 20 new worlds.

We have learned to value
careful observations...

...to respect the facts, even
when they are disquieting...

...when they seem to contradict
conventional wisdom.

The Canterbury monks faithfully
recorded an impact on the moon...

...and the Anasazi people,
an explosion of a distant star.

They saw for us as we see for them.

We see further than they only because
we stand on their shoulders.

We build on what they knew.

We depend on free inquiry...

...and free access to knowledge.

We humans have seen the atoms
which constitute all of matter...

...and the forces that sculpt
this world and others.

We know
the molecules of life...

...are easily formed
under conditions common...

...throughout the cosmos.

We have mapped the molecular machines
at the heart of life.

We have discovered a microcosm
in a drop of water.

We have peered
into the bloodstream...

...and down on our stormy planet...

...to see the Earth
as a single organism.

We have found volcanoes
on other worlds...

...and explosions on the sun...

...studied comets from
the depths of space...

...and traced their origins
and destinies...

...listened to pulsars...

...and searched for
other civilizations.

We humans have set foot
on another world...

...in a place called
the Sea of Tranquility...

...an astonishing achievement
for creatures such as we...

...whose earliest footsteps,
3 million years old...

...are preserved in the volcanic
ash of East Africa.

We have walked far.

These are some of the things
that hydrogen atoms do...

...given 15 billion years
of cosmic evolution.

It has the sound of epic myth.

But it's simply a description...

...of the evolution of the cosmos...

...as revealed by science in our time.

And we...

...we who embody the local
eyes and ears...

...and thoughts and feelings
of the cosmos...

...we've begun, at last, to wonder
about our origins.

Star stuff, contemplating the stars...

...organized collections of 10 billion-
billion-billion atoms...

...contemplating the evolution
of matter...

...tracing that long path by which
it arrived at consciousness...

...here on the planet Earth...

...and perhaps, throughout the cosmos.

Our loyalties are to the species
and the planet.

We speak for Earth.

Our obligation to survive
and flourish...

...is owed not just to ourselves...

...but also to that cosmos,
ancient and vast...

...from which we spring.

The greatest thrill for me
in reliving this adventure...

...has been not just
that we've completed...

...the preliminary reconnaissance
with spacecraft...

...of the entire solar system.

And not just that we've discovered...

...astonishing structures in
the realm of the galaxies...

...but especially...

...that some of Cosmos' boldest
dreams about this world...

...are coming closer to reality.

Since this series' maiden voyage...

...the impossible has come to pass.

Mighty walls that maintained
insuperable ideological differences...

...have come tumbling down.

Deadly enemies have embraced
and begun to work together.

The imperative to cherish
the Earth...

...and to protect the global
environment that sustains all of us...

...has become widely accepted.

And we've begun, finally...

...the process of reducing...

...the obscene number of weapons
of mass destruction.

Perhaps we have, after all...

...decided to choose life.

But we still have light-years
to go to ensure that choice...

...even after the summits and
the ceremonies and the treaties.

There are still some 50,000
nuclear weapons in the world.

And it would require the detonation
of only a tiny fraction of them...

...to produce a nuclear winter...

...the predicted global
climatic catastrophe...

...that would result from the smoke
and dust lifted into the atmosphere...

...by burning cities
and petroleum facilities.

The world's scientific community has
begun to sound the alarm...

...about the grave dangers
posed by...

...depleting the protective
ozone shield...

...and by greenhouse warming.

And again, we're taking some
mitigating steps.

But again,
those steps are too small...

...and too slow.

The discovery that such a thing as
nuclear winter was really possible...

...evolved out of studies
of Martian dust storms.

The surface of Mars,
fried by ultraviolet light...

...is also a reminder
of why it's important...

...to keep our ozone layer intact.

The runaway greenhouse effect
on Venus...

...is a valuable reminder...

...that we must take the increasing
greenhouse effect on Earth seriously.

Important lessons about
our environment...

...have come from spacecraft missions
to the planets.

By exploring other worlds...

...we safeguard this one.

By itself, this fact
more than justifies...

...the money our species has spent...

...in sending ships to other worlds.

It is our fate...

...to live during one of
the most perilous...

...and one of the most hopeful...

...chapters in human history.

Our science and our technology...

...have posed us...

...a profound question:

Will we learn to use these tools...

...with wisdom and foresight
before it's too late?

Will we see our species safely
through this difficult passage...

...so that our children and
grandchildren will continue...

...the great journey of discovery
still deeper...

...into the mysteries of the cosmos?

That same rocket and nuclear
and computer technology...

...that sends our ships past
the farthest known planet...

...can also be used to destroy
our global civilization.

Exactly the same technology...

...can be used for good...

...and for evil.

It is as if...

...there were a god...

...who said to us:

"I set before you two ways.

You can use your technology
to destroy yourselves...

...or to carry you to the planets
and the stars.

It's up to you."