NEIL DEGRASSE TYSON: Must we die?
Are there beings in the cosmos who live forever...
...afloat on an endless journey
down the river of time?
¶ ¶
DEGRASSE TYSON: 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.
(Enheduanna speaking Sumerian)
ENHEDUANNA (translated): Innana, the planet Venus,
goddess of love, will have a great destiny
throughout the entire universe.
(echoing): ...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.
(creature growling)
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.
(thunder crashing)
(dove cooing)
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.
CARL SAGAN: 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.
DEGRASSE TYSON: 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.
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 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 or 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.
(explosion thundering)
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?
(bell tolls)
Do they have heroes and adventures?
(bell tolling)
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.
NEWSREEL ANNOUNCER: The vivid imaginations
of H.G. Wells and Buck Rogers
never cooked up a more fantastic experience
than the Army engineers
at their laboratory in Belmar, New Jersey.
It opens up unlimited possibilities
for interstellar experiment.
DEGRASSE TYSON: American engineers
bounced a beam of radio waves off the Moon,
and were able to detect its echo.
(electronic thrumming)
(electronic warbling and static)
They called this experiment Project Diana.
It was the first interstellar message
ever sent by our species...
(bell tolling)
...an eerie, tolling bell.
If one allows the imagination free reign,
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.
DEGRASSE TYSON: Traveling at the speed of light,
it takes just over one second
for a radio wave to reach the lunar surface.
But the expanding wavefront 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.
(bell tolling)
The parts that missed the Moon are traveling still.
(garbled voices, static)
It was just the beginning.
After World War II,
television stations cropped up all over the United States,
and other parts of the world.
(various overlapping voices and static)
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 six 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 sliy 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 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?
DEGRASSE TYSON: By the time of Enheduanna,
the first person to ever get a writing credit,
civilization was already more than 1,000 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 2,200 BC,
not long after the time of Enheduanna,
disaster struck:
a drought of truly epic proportions,
lasting for many decades.
The rains stopped, crops withered,
and 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
(bird screeches) abrupt climate change.
3,000 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 probably wouldn't be able to do much about.
That supernova is 1,000 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 current 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?
DEGRASSE TYSON: 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 ten 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 gasses
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 distinctive 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 spacetime,
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.
(film projector whirring)
If one allows the imagination free reign.
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 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 five 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,
by their regard for their home planet,
and by their knowledge that, whatever other life 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.
Captioned by Media Access Group at WGBH access.wgbh.org