In our galaxy, there may be ships of other worlds
that dare to venture into the cosmic deep.
Perhaps they travel from star to star,
searching for worlds where life has taken hold.
To get a closer look at the emergent properties of life
that even they can't predict.
This particular vessel is on just such a survey mission.
Who, scanning this world, would have pronounced it a fit nursery for life?
What wild optimist could have foreseen that peonies
and eagles would one day spring from this hell hole?
In its infancy, four billion years ago,
Earth held little apparent promise.
Now, Venus, that's more like it.
Back then, it may have had oceans and land and possibly life.
This long-ago epoch was Venus' moment to flourish.
Its time in the habitable zone.
For any world, that's a period when its relationship to
its star means that it's not too hot and not too cold.
It's a time in a world's existence when it can foster and sustain life.
But the grace of the habitable zone is a fleeting thing
and, for no world, lasts forever.
We reside in our star's habitable zone,
but it is moving outwards at the rate of about three feet per year.
Earth has already passed through 70% of its most hospitable time,
but no need to worry,
that stills leaves us hundreds of millions of years
to plan and execute our exit strategy.
Where will we go when the sun's grace leave us behind
for other worlds and Earth is no longer a garden for life?
Will our species have set sail for distant islands in
the vast ocean of the Milky Way?
(theme music plays).
(waves crashing).
There is no refuge from change in the cosmos.
No safe place to hide for more than a few hundred million years.
Someday, all of this will surrender to the churning cycles of birth,
destruction and rebirth mandated by the laws of nature.
The universe evolves beautiful things then smashes
them to bits before making new ones out of the shattered pieces.
Any species that wants to survive long term on any
possible world, will have to learn how to engineer
interplanetary and ultimately, interstellar mass transit.
How do we know this?
The little we've learned about the universe allows us
glimpses of the future.
I'm not talking about the near-term where climate change
caused by human activity poses a danger to our civilization.
If we want to endure for thousands,
millions even billions of years,
we'll have to stop dumping all that carbon dioxide into
the atmosphere, right now.
But I'm gonna give us the benefit of the doubt
and take the long view.
The sun is aging.
Just like the rest of us.
Someday, it will exhaust the hydrogen fuel at its core.
Five or six billion years from now,
the zone of hydrogen fusion will slowly migrate outward,
an expanding shell of thermonuclear reactions.
Until the temperatures are less than about 10 million degrees.
It will go from being a yellow dwarf to a red giant.
Its gravitational hold on Venus and Earth will diminish
allowing them to migrate to a safer distance,
for a little while.
This red giant sun, ruddy and bloated,
will envelop and devour the planet Mercury.
The grace of the habitable zone will be moving outward,
farther and faster.
By now, the intense light and heat of the sun's expansion
will reach all the way out to the Jupiter system.
Its clouds of ammonia and water will escape and
be lost to space as vapor.
And for the first time, the more dowdy, hidden layers
down beneath Jupiter's gaudy upper atmosphere will be exposed.
Could we make a home on one of Jupiter's frozen moons?
The thick layers of ice encasing Europa and Callisto will defrost,
exposing the liquid oceans beneath to harsh sunlight,
thousands of times stronger than before.
This will liberate large amounts of water vapor,
starting a runaway greenhouse effect.
Ganymede's once thin atmosphere will become steamy and dense.
If life was swimming in those oceans all along,
here's a new chance to flourish and evolve.
Then Ganymede will belong to those beings.
It's just as well, because we'll want our next home
to be at a safer distance from the sun.
Solar evolution is inevitable,
but we have a billion years to go house hunting.
Plenty of time to seek those worlds in the cosmos
that could become our new homes.
Saturn, what has the sun done to you?
She's stolen your glory, your rings.
And Titan, she's robbed you of your atmosphere.
(thunder).
Hey.
We're running out of possible worlds here.
Just in time, Neptune's moon, Triton,
a world named for the son of the Roman God, Neptune.
First known to the Greeks as Poseidon, the God of the Sea.
No one's named this ocean yet, it only began to exist when
the heat of the red giant sun melted the ammonia and
water ices of this once frigid moon.
Our distant descendants will live to different rhythms than we do.
A day on Triton will be 144 hours long.
And the winters will be brutal.
They'll be nearly 50 years long.
But still, the Triton of a few billion years from now could
be a great home for us.
It's got everything,
an atmosphere, water oceans,
the chemical building blocks would make life possible.
Okay, it's chilly, but not much worse than upstate New York in January.
And that means, great skiing all year round.
But one day, the sun will exhaust itself completely and
the fleeting grace of the habitable zone will end here, too.
When the sun's torrid red giant phase is over,
it will strip itself naked,
revealing the small white dwarf beneath.
A star without even enough energy left to warm her surviving children.
The moons of the outer Solar System.
So, if we're looking for a long lease on a new home.
Say, more than just a couple hundred million years,
we'd have to travel even farther out.
We'll have to leave our Solar System and brave the
vast bottomless ocean of interstellar space.
I know what you're thinking,
"are we to venture to the distant stars?"
We once made a few baby steps to the moon before we lost
our will and scurried back to the safety of our mother.
What makes us think we could survive a voyage between the stars?
The nearest of which is 100 million times farther than our moon.
Wouldn't our tiny ships be swallowed up by the great unknown?
I think we can do it.
Why?
Because we've done it before.
We dream of sailing among the island worlds of the Milky Way,
catching photons with our sails.
Daring to go tetherless beyond the point of no return.
We've passed this way before.
Once, there was a people who chose the unknown.
They risked everything to go forth on uncharted seas
and their courage was rewarded.
They found paradise.
I want to tell you their story.
(singing).
We call these people, the Lapita.
But, that was never their name.
It was just the result of a misunderstanding made
decades ago when we first began to discover the
broken shards of their pottery.
To me, they're not the Lapita, they are the Voyagers.
A name far more worthy of them.
About 10,000 years ago,
when the population of settlements in Southern China began to swell,
there were those who chose to pioneer the frontier,
farther south to what is now Taiwan.
And our voyagers settled there,
happily for thousands of years,
until the place began to get too crowded again.
Just as we, of this planet,
came of age in a kind of cosmic quarantine.
Cut off from any hope of knowing about,
much less reaching the other worlds of the cosmos.
Our distant ancestors were prisoners of the land.
If you wanted to travel a great distance,
you had to walk there.
And if you walked as far as you could,
you would be hemmed in at the water's edge.
This was before the age of the great sea-faring civilizations.
The Phoenicians of the Middle-East and the Minoans of Crete.
And for most of their history, they hugged the shore.
Their fishing and trading expeditions were careful to keep land in sight.
For our ancestors, this was the edge of the cosmic ocean.
We do not know what first inspired the voyagers to
attempt the seemingly impossible.
Could they no longer trust the Earth?
(rumbling).
They were living on a tectonic plate where earthquakes
and volcanic eruptions were common.
Or did hostile neighbors there make life intolerable for them?
Did a change in climate threaten their livelihood?
Were their new population pressures?
Did they begin to exhaust the resources of their island
by overhunting and overfishing?
Or was it simply something innately human in them that
made them want to know what was out there?
To reach for the mysterious distance,
no matter how dangerous that might be?
Whatever their motives, over time,
they conquered their fear.
And made preparations to venture where no one had gone before.
(speaking in native language).
(clucking, oinking).
(chirping).
(rain).
(thunder).
(waves crashing).
(chirping).
The voyagers used the careful observations of their
ancestors over generations to develop navigational
techniques that are still viable today.
The seasonal migratory flight patterns of the birds was their GPS.
They also brought high flying frigatebirds with them,
releasing them at the proper time to find the shortest
distance to the nearest land.
They could read water, feeling the ocean currents in their
fingertips and the messages written in the clouds.
These voyagers were scientists and all of nature was their laboratory.
(speaking in native language).
(shouts).
The Philippine Islands was where they settled first.
After lingering there for 1,000 years,
they were ready to set sail again.
New generations of voyagers, Polynesians,
mounted successful missions of exploration to Indonesia.
The Melanesian Islands, Vanuatu,
Fiji, Samoa and onto the Marquesas.
And then, to the most isolated island group on Earth,
the Hawaiian Islands.
Tahiti, Tonga, New Zealand, Pitcairn and Easter Island.
Their empire of water covered nearly 20 million square miles of sea.
And they accomplished this without a single nail
or metal tool of any kind.
As contact between the islands became less frequent,
the language the Polynesians brought with them evolved into
different tongues in isolation.
Many words changed, but one word remained the same
in all the languages of the wide pacific: "Lyar,"
the world for "sail."
Where are we bound for next?
To that place where you can read the book of worlds.
The ship of the imagination is on a mission.
Not to any particular world,
but to an empty space in the interstellar ocean.
Why there?
Come with me.
We're headed to a place 50 billion miles from our sun.
What I'm about to show you is a gift of thousands
of generations of searchers.
We've been studying light for millennia and gravity for centuries.
Among Einstein's many insights was an understanding
of how one could affect the other.
The way gravity bends light makes it possible to turn
any star, including our own,
into a kind of lens for a cosmic telescope.
One 50 billion miles long.
Our most powerful space-based telescopes of the present day
can only see the worlds of other suns as mere dots.
A cosmic telescope could give us detailed images of
the mountains, oceans, glaciers and who knows?
Maybe even the cities of these worlds.
This is the cosmic telescope's detector array.
Collecting the light bouncing off a distant world.
It then sends a signal back to Earth, becoming, in effect,
the telescope's eye piece.
See that brightest star in the sky?
That's our sun.
And the lens of this telescope.
So, how can a star, which you can't see through,
be turned into a lens?
When all the rays of light from a distant planet pass
very close to the sun, the sun's gravity bends
those rays ever so slightly.
Where they converge in space is called the focal point
because that's where the object you're looking at comes into focus.
So, what can you see through a 50 billion mile long telescope?
Virtually anything you want.
Galileo's best telescope could magnify an image 30 times,
making Jupiter, say, appear 30 times closer.
Our cosmic telescope can make things appear 100 billion times closer.
And we can aim it at almost any direction.
Our detector array moves 360 degrees around the sun.
There's only one part of the cosmos that's off-limits to us
and that's the heart of our own Milky Way Galaxy,
which is just too bright.
Its radiance is blinding.
But with a telescope like this one,
so much else that has been foreclosed to us,
would be made visible.
A possible world, perhaps.
The mixture of gases in its atmosphere can tell us if life is there.
Molecules have specific color signatures.
If we look at this atmosphere through a spectroscope,
an instrument that breaks down light into its constituent colors,
we'll be able to identify the molecules that make up the atmosphere.
The presence of oxygen and methane are tell-tale signs of life.
This world is alive and our cosmic telescope could
give us a complete picture of its entire surface.
It's not just an optical telescope,
one that can only see visible light.
It's also a radio telescope.
Just as it can magnify light from distant worlds 100 billion times,
it can do the same for radio waves.
There is something astronomers call a "water hole."
It's named after that place where the lions and
the water buffalo gather to drink and bathe.
(radio static).
It's a region of the radio spectrum,
where interference is at a minimum and we can eavesdrop
on even the faintest transmissions between
far-flung civilizations.
We would need to use all of our computing power to decrypt
the signals hidden in the noise.
(radio static).
MAN (over radio): 1-4-1-5-9-2-6.
(radio chatter).
And this vast telescope is also a means for seeing back in time.
You can't look across space without seeing an object in the past.
That's because the speed of light is finite.
In the morning, look up at the sun and see it as
it was eight minutes and 20 seconds ago.
You'll never see it any other way.
That's because it takes that long for light from the
sun to travel the 93 million miles to Earth.
And when we look at any world through this telescope,
we're seeing it in the past.
Now, imagine the cosmic telescope of another civilization.
Say, one that's 5,000 lightyears from Earth.
The astronomers of that world could witness the building
of the pyramids in Egypt.
Or follow the Polynesian voyages as they bravely made their way across the Pacific.
But perhaps the most important use of the cosmic telescope,
would be our search for new Earths.
What I can't understand is, why we haven't built one.
We already know how to do it.
We have the technology right now.
When would you like the future to begin?
Okay.
We've got the biggest dreams of putting our eyes on other worlds.
Traveling to them, making them our home.
But, how do we get there?
The stars are so far apart.
We would need sailing ships that could sustain human crews
over the longest haul of all time.
The nearest star is four lightyears away.
That's 24 trillion miles to Proxima Centuri.
Just to give you some idea of how far away that point
of light really is?
If NASA's Voyager One spacecraft,
which moves at a pretty good clip,
38,000 miles an hour,
was headed for Proxima Centuri?
It would take 70,000 years to get there.
And that's only the nearest star out of
the hundreds of billions in our galaxy alone.
So, if we want to endure as a species beyond the projected
shelf life of our own planet,
we'd better act like the Polynesians.
We need to take what we know of nature and build sailing
ships that can ride the light as they once rode the wind.
These sails are enormous, miles high,
but they're very thin.
1,000 times thinner than a garbage bag.
When a photon of light strikes those magnificent sails
it gives them a little push.
This means then, in the vacuum of space,
even the tiniest push from a photon will propel them ever faster,
until they're moving at a significant fraction of the speed of light.
When you get too far from your star and the light dwindles,
lasers can do the trick.
If we were to light-sail our way to Proxima Centuri,
it wouldn't take 70,000 years.
But only 20 years.
Proxima B lies in the habitable zone of its star.
But we don't yet know if it could support life.
Does it have the kind of protective magnetic field that
has sheltered the evolution of life on the surface of our world?
Another consequence of Proxima B's close location to its
star is that the planet is probably tidily locked.
One side perpetually facing the star.
The other? Doomed to endless night.
(rumbling).
These little stars may be lukewarm,
but they have a long future ahead of them.
Trillions of years.
Think of the continuity and growth potential of
a civilization with a future measured in trillions of years?
It's always magic hour on this strip of land that lies
between day and night of this world.
If Proxima B is habitable, its life would be confined
to this twilight zone.
It could be a home for the indigenous life here or
a possible campsite for our descendants.
The gravity on Proxima B is about 10% greater than ours on Earth.
No real problem for us.
Just a little like exercising with weights on.
Remote scanning from orbit found no apparent signs of
life making Proxima B a waystation on a much grander
interstellar diaspora of Earthlings.
But for those longer trips?
We're gonna need a faster boat.
Let's say we found a system located 100 light-years from home.
One with several potentially habitable worlds.
For light-sailors, that would be a 500 year long trip.
Is it possible to build a ship that could break the cosmic speed limit?
A mathematical physicist, Miguel Alcubierre of Mexico,
inspired by the original Star Trek television series,
conceived the calculations for a ship that could
theoretically travel faster than the speed of light.
If successful, it could cut the travel time between
our sun and this distant star system down to a single year or even less.
But wait a minute, isn't it a cardinal rule of science
that "thou shalt not travel faster than light?"
It is.
But here's the thing about the Alcubierre Drive.
It doesn't move, the cosmos does.
The ship itself would be enclosed in its own space-time bubble.
Where it needn't violate any laws of physics.
Harold White of the United States ironed out some of the kinks.
Such as prohibitively enormous energy requirements to fly it.
But it remains far beyond our immediate grasp.
The Alcubierre Drive Ship is a gravitational wave making
machine, that compresses the ocean of space-time
in front of it and expands that ocean in its wake.
Jet skis for joyriding through the galaxy and beyond.
Who knows?
Maybe the entire Laniakea supercluster could one day become our pond.
That's 100,000 galaxies.
Laniakea, the phrase in Hawaiian for "immeasurable heaven."
An advanced version of our Alcubierre Drive
could do 600 trillion miles in the blink of an eye.
Before you know it, you're in the planetary system of a distant star.
Let's call it, the "Hoku" system.
A red dwarf star surrounded by a retinue of rocky and ice giant planets.
Somewhere among them is a world that we have come to call home.
Our cosmic telescope sifted through all the stars within
a radius of 100 light years and pointed the way to this one.
All seven of these planets, huddle closer to their star
than Mercury does to our sun.
Haumia is just on the outskirts of Hoku's habitable zone.
Those warm green colors seem inviting,
but we're not seeing the tops of forests.
That green comes from methane and ammonia.
Even at a distance of only 27 million miles,
the star Hoku is too weak to keep this planet warm.
We are now in the sweet spot of Hoku's habitable zone.
And this is the planet Tangaroa,
where the latest chapter of the saga of our species is playing out.
It took a few hundred years for humans to terraform this lifeless world.
But now, even the air tastes as sweet as home.
But this was only Indonesia.
One of the earlier stops on our nomadic odyssey throughout
the Milky Way.
There were still so many islands that lay ahead.
And in this dream future of ours,
with our faster than light craft?
There would come a time when we could place our cosmic telescope
far enough away from our home planet to see first-hand,
those of our nameless ancestors who first set sail on unknown seas.
(radio static).
Carl Sagan made this drawing when he was a child.
Imagining the unfolding of the next Golden Age of Exploration.
As a scientist, he played a central role in it.
And now, he speaks to us out of the past.
About our dreams of the future.
Are we to venture out into space?
Move worlds, re-engineer planets,
spread to neighboring star systems?
We, who cannot even put our own planetary home in order,
riven with rivalries and hatreds.
Despoiling our environment, murdering one another through
irritation and inattention.
As well as on deadly purpose and moreover, a species that,
until only recently, was convinced that the whole
universe was made for its sole benefit.
I do not imagine that it is precisely 'we.'
With our present customs and social conventions who will be out there.
If we continue to accumulate only power and not wisdom,
we will surely destroy ourselves.
Our very existence in that distant time requires
that we will have changed our institutions and ourselves.
How can I dare to guess about humans in the far future?
It is, I think, only a matter of natural selection.
If we become even slightly more violent, short-sighted,
ignorant and selfish than we are now.
Almost certainly, we will have no future.
If you're young, it's just possible that we will
be taking our first steps on near-Earth asteroids and
Mars during your lifetime.
By the time we're ready to settle even the nearest other
planetary systems, we will have changed.
The simple passage of so many generations will have changed us.
The different circumstances we will be living under will have changed us.
We're an adaptable species.
It will not be we who reach Alpha Centauri
and the other nearby stars.
It will be a species very like us,
but with more of our strengths and fewer of our weaknesses.
A species returned to circumstances,
more like those for which it was originally evolved.
More confident, far-seeing, capable and prudent.
The sorts of beings we would want to represent us
in a universe that, for all we know,
is filled with species much older,
much more powerful and very different.
The vast distances that separate the stars are providential.
Beings and worlds are quarantined one from another.
The quarantine is lifted, only for those with sufficient
self-knowledge and judgement to have safely traveled from star to star.
Our remote descendants safely arrayed on many worlds through
the solar system and beyond will be unified by
their common heritage, by their regard for their
home planet and by the knowledge that whatever other life may be,
the only humans in all the universe come from Earth.
("Thank you, mother" in native languages).
Thank you, mother.