Cosmos

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 5,000 years ago,

who first starting 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 has 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 4,000 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 one 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.

Its 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 deathlike sleep of eight 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 four-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.