All language subtitles for AB23B75CA3AE259276A3B5F812339C67_eng

Must we die?

Are there beings in the cosmos
who live forever...

afloat on an endless journey
down the river of time?

Our ancestors marked the passage
of time by the moon and stars.

But it was the people who once
lived here, around 5000 years ago...

who first started chopping up time into
smaller bite-sized portions of hours...

and minutes. They call
this place Uruk. We call it Iraq.

It's a part of Mesopotamia...

the land between the Tigris
and the Euphrates rivers.

The city was invented here.

And one of humanity's
greatest victories was

won in the ceaseless
battle against time.

It was here that we learned
how to write.

Death could no longer silence us.

And writing gave us the power
to reach across the millennia...

and speak inside
the heads of the living.

No one had ever spoken across
a longer stretch of time's river...

than this Akkadian princess,
daughter of the first emperor in history...

and priestess of the moon. Enheduanna.

For not only did she write poetry...

but Enheduanna did something
no one before her had ever done.

She signed her name to her work.

She's the first person for whom we can say
we know who she was and what she dreamed.

She dreamt of stepping through
the Gate of Wonder.

Here's a thought Enheduanna
sent across more than 4000 years to you.

It's from her work entitled
Lady of the Largest Heart.

Innana, the planet Venus,
goddess of love...

will have a great destiny
throughout the entire universe.

Throughout the entire universe.

And Uruk is also the
place where the epic tale

of the hero's journey
was first written down.

Before Batman, Luke Skywalker,
Odysseus, before them all...

there was a man named Gilgamesh
who left home on a quest to vanquish time.

Gilgamesh was searching for immortality.

He looked everywhere,
gained complete wisdom...

uncovered what was hidden.

He brought back a tale of times
before the Great Flood.

He built the wall of Uruk,
which no future king will ever match.

Read the story of that man, Gilgamesh,
a hero born of Uruk...

who went through all kinds of sufferings...

who crossed the ocean, the broad seas...

as far as the sunrise...

who inspected the edges of the world,
searching for eternal life.

On his travels, Gilgamesh encountered
a wise man named Utnapishtim...

who told him the story of a flood
that destroyed the world...

and how one of the gods
instructed Utnapishtim...

to build an ark
to rescue his family and the animals.

The earliest surviving account of the flood
legend was written down in Mesopotamia...

a thousand years before it was retold
as the story of Noah in the Old Testament.

So you could say Gilgamesh
fulfilled his quest for immortality.

We still read the Epic of Gilgamesh,
and with every reader...

he lives again.

And all those heroes and superheroes who
have come since follow in the footsteps...

of the first hero's journey...

another kind of immortality.

A story sent from one civilization
to another across thousands of years.

But life itself sends its own stories
across billions of years.

It's a message that every one of us
carries inside...

inscribed in all the cells of our bodies in
a language that all life on Earth can read.

The genetic code is written in an alphabet
consisting of only four letters.

Each letter is a molecule made of atoms.
Each word is three letters long.

Every living thing
is a masterpiece...

written by nature
and edited by evolution.

The instructions for running...

and reproducing
the intricate machinery of life.

The essential message of life
has been copied...

and recopied
for more than 3 billion years.

But where did that message
come from?

Nobody knows.

Perhaps it began in a shallow,
sunlit pool...

just like this.

Somehow, carbon-rich molecules began using
energy to make crude copies of themselves.

Some varieties were better
at making copies, and left more offspring.

The competing molecules
became more elaborate.

Evolution and life itself
was underway.

Or life could've started
in the searing heat

of a volcanic vent
on the deep sea floor.

Or is it possible that life came to Earth
as a hitchhiker?

Let me tell you a story about a traveler
from another world.

The peace of the Egyptian
village of Nakhla, near Alexandria...

was abruptly shattered
on a June morning in 1911.

Written in this meteorite
was a message from another planet.

But 70 years would pass
before anyone could read it.

In 1976, NASA landed two Viking
spacecraft on Mars.

Carl Sagan took us there on our original
journey through the cosmos.

We found that the Martian air
was less than 1 percent as dense as ours...

and made mostly of carbon dioxide.

There were smaller amounts of nitrogen,
argon, water vapor and oxygen.

A few years later, when scientists
thought to analyze the gasses...

trapped inside the Nakhla meteorite,
and other members of its class...

they found a striking similarity.

The vast majority of meteorites
are fragments of asteroids.

But the kind that hit Nakhla on Earth
could only have come from one place.

Mars.

Welcome to Mars.

Over a billion years ago,
a volcano erupted here...

and its lava cooled into solid rock.

Hundreds of millions of years later,
this area was flooded with water.

And long after that flood, an asteroid
the size of the Rock of Gibraltar...

crashed into the Martian surface,
blasting out a huge crater.

Much of the debris
was ejected back out into space...

where it orbited the
sun until a gravitational

tug from its home
planet, Mars...

diverted one of
the boulders into a

collision course with
Earth. It's arrival...

shook up the little village
of Nakhla. Meteorites...

of the type that hit Nakhla...

are the vehicles of a natural
interplanetary transit system...

that sends rocks between the planets.

Such a meteorite can safely shelter
microscopic cargo...

the seeds of life,
an interplanetary ark.

Most rocks are porous,
full of tiny nooks and crannies...

where life can stow away.

We know that some microbes can survive
the hostile environment of space.

Take these guys, for instance.

These microbes spent a year and a half
riding on the outside...

of the International Space Station,
exposed to the extreme temperatures...

vacuum, and radiation of space.

And some of them
were still alive and

kicking when they were
brought back to Earth.

Even more astonishing
are these creatures...

awakened from a death-like sleep
of 8 million years.

They were frozen in
the Antarctic ice millions

of years before our
species even existed.

And they're still alive.

If life can withstand the hardships
of space and endure for millennia...

then it could ride the
natural interplanetary

transit system
from world to world.

It's a good bet that our microbial
ancestors spent some time in space.

Why do we think so?

The Earth is 4 and a half billion
years old.

For the first half of its lifetime...

large asteroids were bombarding
the planet every few million years.

The most violent impacts vaporized the
oceans and even melted the surface rock.

Each such collision
would have completely

sterilized the planet
for thousands of years.

But we know from fossils in the rocks
that bacteria were evolving on Earth...

during this formative period.

So how could life have survived
such a lethal series of blows?

Whenever one of those big asteroids
hit the Earth...

the explosion would blast out a crater,
launching millions of boulders into space.

Many of those rocks
carried living bacteria inside.

Some of the bugs
would have survived in space...

while all those left behind on Earth
would have been fried.

A few thousand years after each impact...

the Earth would have cooled down enough
for water to condense into oceans.

The planet would again be habitable.

Meanwhile, most of the rocks launched into
space would have been orbiting the sun.

Some of them would encounter
the Earth again...

reenter the atmosphere as meteorites...

and deliver their precious cargo of life
to re-seed the planet...

like Noah's ark.

What this means is that life
doesn't have to start over again...

from scratch after each catastrophe.

It can pick up where it left off.

When the solar system
was young...

Venus was probably more like Earth,
with oceans and maybe even life.

Venus, Earth, and Mars were all
exchanging rocks with each other...

due to asteroid impacts.

Does life on Earth carry any traces
of interplanetary voyages...

made in the distant past?

Why is it that some microbes can survive
the intense radiation and vacuum of space?

These conditions don't naturally exist
on Earth.

Maybe those bugs are telling us
that their ancestors survived...

those same conditions in space,
a few billion years ago.

So we know that microbes can stow away
in rocks and survive the voyage...

from planet to planet.

But what about a trip from star to star,
an interstellar odyssey?

The dandelion.

Around 30 million years ago...

it evolved another way to send its
own message of life through space and time.

Each seedling is a little paratrooper,
floating on the wind...

risking everything for
a safe place to land.

Updrafts can carry
them higher into the air.

A dandelion can travel dozens...

possibly hundreds of kilometers...

even crossing over mountain ranges.

Evolution has shaped it
into an exquisite flying machine.

The seed is another kind of ark...

ensuring the survival
of its species by riding

the currents of the
atmosphere to safe harbors.

Each seed, in its DNA,
carries a story...

the character and destiny
of the next dandelion.

Life propagates by retelling its story.

Is it possible that life could survive
the journey from star to star?

The stars are about a million times farther
apart from each other than are the planets.

Space is so vast that
it would take billions

of years for a rock
ejected from the Earth...

to collide with a planet
circling another star.

Any stowaway microbes would never survive
the cosmic radiation for that long.

But there's a plausible
scenario for how life

could spread from one
solar system to another.

The stars of the Milky Way are drawn
by gravity...

in their own enormous orbits
around its center.

Our sun, for example...

takes some 225 million years
to complete a single orbit.

During each revolution around the galaxy...

our solar system will pass through two
or three gigantic interstellar clouds...

each of them many light-years across.

Galaxies are world-making machines.

Our Milky Way has more than 100
of these vast clouds...

places where gas and dust condense
to form new stars and planets.

In its travels through the Milky Way...

our sun is accompanied
not only by its planets...

but also by a trillion distant comets.

When our solar system
passes through an interstellar cloud...

the gravity of the massive cloud
stirs up the outermost comets.

Some comets will be hurled out
into the space between the stars.

Others will plunge inward...

"falling towards the sun."

And some of them
may collide with the planets.

The high-speed impact of a comet
with a rocky planet...

will launch boulders
like rockets into space.

If that planet should happen
to be inhabited...

many of those rocks
will carry passengers...

living microbes.

After thousands of years...

fragments of the rocks ejected
from Earth can fall as meteors...

into the atmospheres of newborn planets
in the interstellar cloud.

If the stowaway microbes should happen
to come in contact with liquid water...

they can revive and reproduce.

This may be how life
comes barreling into the barren places.

The sun emerges from the cloud...

having scattered the seeds of life
among the newborn worlds of other stars.

Those new worlds, now touched by life...

will then leave their birth cloud
and go their separate ways.

Eventually, their stars will carry them
through other interstellar clouds...

where they may seed
still more new worlds.

Imagine this process repeated
from world to world...

each one bringing life to others.

Life would then propagate,
like a slow chain reaction...

through the entire galaxy.

This could be how life came to Earth.

We do not know for sure.

Are there any beings out there like us?

Do they ask the same questions?
Do they share our fears?

Do they have heroes and adventurers?

If they do exist, where are they?

How might they make
their presence known?

How did we first announce our presence
to the galaxy?

It was 1946, the year after
the Second World War ended.

The imaginations of H. G. Wells
and Buck Rogers never cooked up...

a more fantastic experience...

than the Army engineers
at their laboratory in Be/mar, New Jersey.

It opens up unlimited possibilities
for interstellar experiment.

American engineers bounced
a beam of radio waves off the moon...

and were able to detect its echo.

They called this experiment Project Diana.

It was the first interstellar message
ever sent by our species.

An eerie tolling bell.

If one allows the imagination free rein...

many future possibilities appear.

Spaceships, carrying passengers
at thousands of miles per hour...

can be controlled...

and communication established
with their passengers.

For we now know that the
Earth's atmosphere can be penetrated.

Traveling at the speed of light...

it takes just over one second for a
radio wave to reach the lunar surface.

But the expanding wave front
is much bigger than the moon.

Most of the wave passes right by it...

but the central part gets bounced back.

After a round-trip travel time of two
and a half seconds, it hits our planet.

Project Diana transmitted
a series of powerful radio waves...

one every four seconds,
to ping the moon.

The parts that missed the moon
are traveling still.

It was just the beginning.

After World War II...

television stations cropped up
all over the United States...

and other parts of the world.

The Project Diana message...

and the FM radio, television
and radar signals of the 20th century...

all move outward at the speed of light.

These transmissions make up
a vast sphere of radio waves...

expanding away from the Earth
in all directions.

You could say that
our world is radiating stories.

Our ancestors etched the story
of Gilgamesh into clay tablets...

sending that epic tale into the future.

We've encoded our stories in radio waves
and beamed them into space.

They cover one light-year of distance...

that's 6 trillion miles, for every
year of time since they were sent.

We've been sending our stories into space
for over 70 years.

The leading edge of these signals
has already washed over...

thousands of planets of other stars.

If any of these worlds are home
to a civilization with radio telescopes...

they could already know that we're here.

What if other worlds
are sending their stories into space?

Since 1960, we've been listening
for extraterrestrial radio signals...

without hearing so much as a tolling bell.

But our search has been sporadic
and limited to certain parts of the sky.

For all we know,
we may have just missed an alien signal...

looking in the wrong
place at the wrong time.

We've only listened to a miniscule fraction
of the stars in our galaxy.

And there may be another problem.

We are, to some extent, prisoners
of our own moment in time...

and the limits of our technology.

Radio and television broadcasting...

may be only a brief passing phase
in our technological development.

When we imagine
alien civilizations

broadcasting signals
with radio telescopes...

are we any different
from earlier generations...

who imagined riding cannon shells
to the moon?

Civilizations even slightly
more advanced than ours...

may have already moved on
to some other mode of communication...

one that we have yet to discover
or even imagine.

Their messages could be swirling
all around us at this very moment...

but we lack the means to perceive them...

just as all of our ancestors,
up to a little more than a century ago...

would have been oblivious to the most
urgent radio signal from another world.

But there's another,
more troubling possibility.

Civilizations, like other living things...

may only live so long
before perishing due to natural causes...

or violence, or self-inflicted wounds.

Whether or not we ever make contact
with intelligent alien life...

may depend on a critical question:

What is the life
expectancy of a civilization?

By the time of Enheduanna, the first
person to ever get a writing credit...

civilization was already
more than 1000 years old.

But today, her glorious city
is a barren wasteland.

What went wrong?

One problem was
the almost ceaseless

warfare between the
cities of Mesopotamia...

which continually destroyed
their achievements.

They glorified military conquest,
and ultimately...

became its victims.

Another cause of decline was that...

their technical know-how
overran their understanding of nature.

The ingenious irrigation system...

that was the basis for the great
civilizations of Mesopotamia...

had an unintended consequence.

The water channeled
into their farmlands every year...

evaporated and left its salt behind.

Over generations, the salt accumulated
and began to kill the crops.

And then, about 2200 B. C...

not long after the time of Enheduanna,
disaster struck.

A drought of truly epic proportions,
lasting for many decades.

The rains stopped, crops withered,
there was famine and anarchy.

Barbarians invaded.

The streets of many cities
were littered with dead.

There could be only one explanation.

Enlil, the supreme god, was angry...

because one of his temples
had been destroyed.

The people of Mesopotamia could not know...

that the same drought was crushing
the dawning civilizations of Egypt...

Greece, India, Pakistan and China.

All the gods of the Earth must have
been really angry about something.

For all their brilliance...

the people of those civilizations
had no inkling...

they were experiencing
abrupt climate change.

Three thousand years later...

the climate would change abruptly
for another glorious civilization...

this one in Central America.

At its peak,
the Mayan civilization perished...

wiped out by a series of severe droughts
over the course of a century.

We still carry within
us the echoes of these

extinct civilizations,
in our languages...

and our myths.

Today, we have a
single global civilization.

How long will it live?

There are so many ways
for a civilization to die.

Let's start with the ones that
we wouldn't be able to do much about.

That supernova is 1000 light-years away.

If it were much closer,
say less than 30 light-years from Earth...

its cosmic radiation would shred
the atmosphere's protective ozone layer...

and destroy our civilization.

Lucky for us, none of the
stars close enough to harm us...

are likely to go supernova any time
in the next few hundred million years.

Every million years or so,
a supervolcano erupts somewhere on Earth.

The last time it happened
was 74,000 years ago...

on the island of Sumatra
in what is now Indonesia.

It spewed hundreds of times more
rock, ash and toxic gas...

than any single volcano
in recorded history.

The molten rock that erupted
from Earth's crust left this caldera...

100 kilometers long,
now filled with a lake.

The Toba volcano sent
more than 600 cubic miles...

of pulverized rock soaring skyward.

The westward wind
carried the volcanic ash over India...

where it fell out in a smothering blanket
over the subcontinent.

The eruption loaded the upper atmosphere
with sulfur gases.

The result was a global haze
that blocked most of the sunlight...

from reaching the surface
for at least five years.

It was like one five-year-long cloudy day.

This so-called volcanic winter
resembled a nuclear winter...

but without the radiation.

Temperatures fell everywhere.

Plants and animals froze,
even in the tropics...

dying in enormous numbers.

But life is hardy. Only a few species
were driven to extinction.

One of our ancestors in central India
sharpened this stone blade...

in the years before the Toba eruption.

And this blade was one of dozens
that were found in the soil layer...

above the volcanic fallout.

This tells us that some toolmakers...

even in the area
directly affected by the volcano...

managed to survive the cataclysm.

But the global human population
must have plummeted before rebounding.

If an eruption like this
were to happen tomorrow...

our civilization would be
brought to its knees...

although the human species
would survive.

I can imagine that our technology
of a few hundred years from now...

would allow us to siphon off the energy
of a threatening supervolcano...

before it explodes.

We could then use that energy
for our own purposes.

About once every million years,
a small asteroid collides with the Earth...

causing a similar amount of devastation.

With our science and technology...

we already know how
to prevent an asteroid impact.

We would see it coming years in advance...

and could send a spacecraft there
to deflect it into a harmless orbit.

With the technology
of a thousand years from now...

we might even be able to mitigate
the deadly effects of a nearby supernova...

on Earth's atmosphere.

But what happens when
the danger to a civilization is invisible?

When no one can see it coming?

Beginning with Columbus,
the European invaders of the Americas...

had a secret weapon
that even they knew nothing about.

They were carrying bacteria and viruses
for deadly diseases, such as smallpox...

that the original Americans
had never been exposed to.

The Europeans like
to believe that it was

their valor and superior
weapons and culture...

that won them the New World.

The real conquistadors
were the armies of the pathogens...

that raced on ahead
to infect and kill nine out of 10...

of all the Indians of North,
Central and South America.

The great civilizations of the New World
crumbled...

under the onslaught of invading microbes.

Without his invisible army...

Cortez and those who followed
might never have stood a chance.

But what about civilizations
that self-destruct?

Our economic systems were formed
when the planet and its air...

rivers, oceans, lands, all seemed infinite.

They evolved
long before we first saw the Earth...

as the tiny organism that it actually is.

They're all alike in one respect.

They're profit-driven, and therefore,
focused on short-term gain.

The prevailing economic systems,
no matter what their ideologies...

have no built-in mechanisms
for protecting our descendants...

of even 100 years from now,
let alone 100,000.

In one respect, we're ahead
of the people of Ancient Mesopotamia.

Unlike them, we understand
what's happening to our world.

For example, we're pumping
greenhouse gases into our atmosphere...

at a rate not seen on Earth
for a million years.

And the scientific consensus
that we're destabilizing our climate.

Yet, our civilization seems to be
in the grip of denial...

a kind of paralysis.

There's a disconnect between
what we know and what we do.

Being able to adapt our behavior
to challenges...

is as good a definition
of intelligence as any I know.

If our greater intelligence
is the hallmark of our species...

then we should use it,
as all other beings use their advantages...

to help ensure that their offspring
prosper, and their heredity is passed on...

and that the fabric of nature
that sustains us is protected.

Human intelligence is imperfect, surely,
and newly arisen.

The ease with which it can be sweet-talked,
overwhelmed, or subverted...

by other hard-wired tendencies...

sometimes themselves disguised
as the light of reason, is worrisome.

But if our intelligence is the only edge,
we must learn to use it better.

To sharpen it. To understand
its limitations and deficiencies.

To use it, as cats use
stealth before pouncing.

As walking sticks use camouflage.

To make it the tool of our survival.

If we do this...

we can solve almost any problem
we are likely to confront...

in the next 100,000 years.

And now we've arrived at the place
where our ancient dreams of immortality...

and modern astrophysics converge.
Giant elliptical galaxies...

are something like Florida...

where the oldest stars
in the universe may be found.

This is a red dwarf star,
smaller and fainter than our sun.

Red dwarfs are by far
the most plentiful stars in the cosmos.

Unlike the sun, which is halfway through
its 10-billion-year lifetime...

red dwarfs will continue to provide light
and warmth to their planets...

for trillions of years.

That's hundreds of times longer
than the present age of the universe.

What would intelligent beings do...

if they had an eternity to develop
their understanding of the universe?

Perhaps they would learn how to open
shortcuts in the fabric of space-time...

to travel between galaxies
faster than the speed of light.

Maybe they would create
whole new universes...

as artistic or scientific experiments.

Of course no one,
or at least nobody on Earth...

knows what the immortals
might do.

If one allows the imagination free rein...

But what about us?

What is our own future?

What would the cosmic calendar
of the next 14 billion years look like?

If the original cosmic calendar
includes all of the time...

from the birth of the universe
until this very moment...

what would the cosmic calendar look like
for the next 14 billion years?

Just as with the cosmic calendar
of the past...

every month on the future calendar
equals about a billion years...

every day, some 40 million.

Science makes it
possible for us to foretell...

certain astronomical events
in the unimaginably distant future.

The death of the sun, for example.

In some 5 billion years...

our star will have exhausted its hydrogen,
the nuclear fuel that powers it...

becoming a red giant.

I know that sounds depressing,
but if we apply our intelligence...

our descendants of that distant future...

will have long departed
from the lost worlds of the sun.

Who knows?

Human events entail too many variables,
too many uncertainties...

to make scientific statements
about our future.

But we can still dream.

The next golden age of human achievement
begins here and now.

New Year's Day of the next cosmic year.

In the first tenth of a second...

we take the vision
of the pale blue dot to heart...

and learn how to share this tiny world
with each other.

The last internal combustion engine
is placed in a museum...

as the effects of climate change
reverse and diminish.

A fifth of a second into this future...

people will stop dying
from the effects of poverty.

The planet is now a completely

self-sustaining,
intercommunicating organism.

A half-second from now...

the polar ice caps are restored
to the way they were in the 19th century...

and the forecast is mild and pleasant
for the next cosmic minute and a half...

40, 000 years.

By the time we are ready to settle
even the nearest other planetary systems...

we will have changed.

The simple passage of so many generations
will have changed us.

Necessity will have changed us.

We are an adaptable species.

It will not be we who
reach Alpha Centauri...

and the other nearby star systems
on our interstellar arks.

It will be a species very like us...

but with more of our strengths
and fewer of our weaknesses.

More confident, far-seeing,
capable and wise.

For all our failings,
despite our flaws and limitations...

we humans are capable of greatness.

What new wonders,
undreamt of in our time...

will we have accomplished
in another generation...

and another?

How far will our nomadic species
have wandered...

by the end of the next century
and the next millennium?

Our remote descendants...

safely arrayed on many worlds
throughout the solar system and beyond...

will be unified by their common heritage...

b y their regard for their home planet...

and by the knowledge that
whatever other life there may be...

the only humans in all the universe
came from Earth.

They will gaze up and strain
to find the blue dot in their skies.

They will marvel at how vulnerable the
repository of all our potential once was...

how perilous our infancy,
how humble our beginnings.

How many rivers we had to cross...

before we found our way.