Yes, this is home.
This is Earth.
Having trouble finding a familiar continent?
The past is another planet.
Actually, many.
I'm standing on the great expanse of time that has elapsed
since the Big Bang. In order to think about it,
we've compressed it all into a single year.
It's the early morning of December 23
on this Cosmic Calendar of ours,
or about 350 million years ago,
when our world was a mere four billion years old.
Earth looks so different.
You might not even know the place.
The stars wouldn't help you.
Even the constellations would have been different back then.
The dinosaurs were still
more than 100 million years in the future.
There were no birds, no flowers.
And the air was different, too.
The atmosphere had more oxygen than at any other time
in Earth's history, before or since.
This allowed insects to grow much larger than they do today.
How?
Insects don't have lungs.
Life-giving oxygen is taken in through openings
in the outside of their bodies
and transported through a network of tubes.
If an insect were too large,
the outer reaches of these tubes would absorb all the oxygen
before it could ever get to its internal organs.
But during the Carboniferous Period,
the atmosphere had almost twice the oxygen as today.
Insects could then grow much bigger
and still get enough oxygen in their bodies.
That's why the dragonflies here are as big as eagles
and the millipedes the size of alligators.
So why was there so much oxygen back then?
It was produced by a new kind of life.
What kind of life could've changed
the Earth's atmosphere so dramatically?
Plants that could reach for the sky--
trees.
In their competition for sunlight,
trees evolved a way to defy gravity.
Before trees, the tallest vegetation was
only about waist-high.
And then something wonderful happened.
A plant molecule evolved that was both strong and flexible,
a material that could support a lot of weight,
yet bend in the wind without breaking.
Lignin made trees possible.
Now life could build upward.
And this opened a whole new territory,
a three-dimensional matrix
for communities far above the ground.
Earth became the Planet of the Trees.
But lignin had a downside:
it was hard to swallow.
When nature's demolition crew, the fungi and bacteria,
tried to eat anything with lignin in it,
they got a really bad case of indigestion.
And termites wouldn't evolve
for at least another 100 million years.
What to do with all those dead trees?
It took the fungi and bacteria millions of years
to evolve the biochemical means to consume them.
Meanwhile, the trees just kept springing up,
dying, falling over
and getting buried by the mud that built up over eons.
Eventually, there were hundreds of billions of trees
entombed in the Earth,
buried forests all over the Earth.
What possible harm could come from that?
This cliff in Nova Scotia is another kind of calendar.
It tells the story of that other world
that once flourished right here.
And this is the death mask
of that 300 million-year-old tree.
It was cast by minerals that replaced the original wood
cell by cell-- in other words, a fossil.
The tree surrendered its organic molecules
to the environment long ago,
its carbon and water. Only its shape remains.
When this tree was alive, it took in carbon dioxide
and water and used sunlight
to turn them into energy-rich organic matter.
The tree gave off oxygen as a waste product.
That's what trees and other plants still do.
When plants die, they decay,
and this reverses the transaction.
Their organic matter combines with oxygen
and decomposes,
putting carbon dioxide back into the air.
This balances the books
for the chemistry of Earth's atmosphere.
But if the trees are buried before they can decay,
two things happen... they take the carbon
and stored solar energy with them
and leave the oxygen behind
to build up in the atmosphere.
That's what happened around 300 million years ago.
There was an oxygen surplus.
That's how the bugs got so big.
And what became of all that buried carbon?
It lay there for eons before dealing life on Earth
its most devastating blow of all time.
There are places on this planet where you can walk through time
and read the history written in the rocks.
This beach in Nova Scotia is one of them.
Every layer is a page.
Each one tells the story of a flood,
one after another, over millions of years.
The layer cake of flood deposits was slowly buried
and turned into rock by heat and pressure.
The same forces that built mountains
then tilted and uplifted them,
along with the entombed fossil forest.
The newer layers were always
deposited on top of the older ones.
All the pages are in the correct order,
bearing witness to what happened here
over millions of years.
Back that way
lies the more distant past.
And with every step I take,
I move about 1,000 years closer to the present
and away from the world of 300 million years ago.
50 million years later lies that way.
This was the beginning of the end of the Permian world,
an event of unequalled carnage.
The Permian is the darkest corridor
in this memorial to the broken branches on the Tree of Life--
the Halls of Extinction.
Death has never come so close
to reigning supreme on this world
in the quarter billion years since.
The eruptions, in what is now Siberia,
lasted for hundreds of thousands of years.
The lava flooded and buried more than a million square miles.
This event dwarfs any volcanic eruption
in historical times.
_
Huge quantities of carbon dioxide came pouring
out of the volcanic fissures.
This greenhouse gas warmed the climate.
And this is where the long-buried forests
of the earlier Carboniferous Period reenter the story.
During the intervening 50 million years,
those trees had turned into immense deposits of coal,
and as it happened,
one of the world's largest
accumulations of coal
was buried right there in Siberia.
The heat from the lava baked the coal,
driving methane and sulfur-rich gases out of the ground.
They were laden
with toxic and radioactive ash particles--
coal smoke.
This witch's brew polluted the atmosphere
and radically destabilized Earth's climate.
A sulfuric acid haze blocked incoming sunlight
and darkened the planet.
Global temperatures plummeted to subfreezing.
During lulls in the eruptions,
the acid haze fell back to the surface.
But the carbon dioxide remained
and built up in the atmosphere to cause global warming.
Years of frigid cold
alternating with millennia of stifling heat
battered a dwindling population of plants and animals.
They had no chance
to adapt to the drastic swings in climate.
As the global warming
continued, the surface and the bottom waters
slowly mixed, raising the temperature
of the once-frigid depths of the sea floor.
Methane-rich ices
that had been frozen in the sediments began to melt.
Newly liberated methane gas made its way to the surface
and into the atmosphere.
Methane traps heat far more efficiently
than carbon dioxide, so the climate
got even hotter.
And the methane also destroyed
the ozone layer in the stratosphere.
The natural sunscreen that protects life
from deadly ultraviolet rays was eaten away.
The circulatory system of the world ocean shut down.
These stagnant waters became oxygen-starved,
killing almost all the fish in the sea.
But one kind of life flourished in this brutal environment...
bacteria that produced deadly hydrogen sulfide gas
as a waste product.
That was the last straw.
The poison gas killed almost all the remaining plants
and animals on the land.
This was the Great Dying.
The closest life on Earth has ever come to annihilation.
Nine in ten of all species perished.
It took a long time for life to bounce back.
For a few million years, Earth could have been called
the Planet of the Dead.
We are descended from one of the few species
that managed to squeak by.
You are human and alive at this very moment
because they managed to endure, conveying
their DNA through one of the most treacherous periods
in the history of life.
This mountain was made entirely by life.
The life that flourished back in the glory days
of the Permian, before all hell broke loose.
This is part of the 400 mile-long
Guadalupe Mountain chain that runs through
Texas and New Mexico.
It's the world's largest fossil reef.
All this was once a great inland sea.
The reef flourished and grew for millions of years,
and was home to multitudes of sponges, green algae,
and animals too small to see.
When these creatures died,
they sank to the bottom and were buried in the silt.
Over millions of years,
their remains were converted into oil and gas.
Eventually, the basin
silted in and the reef died.
This marine ghost town was then buried
a mile beneath the surface.
Later, tectonic forces lifted the skeletal reef
high above sea level, where it was eroded and sculpted
over eons by wind and rain.
Just imagine what this place looked like
275 million years ago,
when it was a vibrant, tropical inland sea,
dotted with islands
and brimming with life.
Until about 220 million years ago,
New England and North Africa were next-door neighbors.
There was no such thing as the Atlantic Ocean.
Those thin blue fingers at the center-- they were lakes.
They were the first outward signs that the supercontinent
was splitting apart and that
life on Earth was due for another big shake-up.
A million years later, the lakes became a long bay,
which would grow into the Atlantic Ocean.
These profound changes at the surface
were merely symptoms of a drama that was unfolding far beneath,
in the depths of the Earth.
By the time we got here, the telltale traces
of global upheaval were buried
at the bottom of the deep blue sea.
We were completely cut off from the great story
of Earth's violent past--
a species of amnesiacs trying to find out
who we were and what happened
before we awakened.
In 1570, Abraham Ortelius created the first
modern world atlas, reflecting on the discoveries
of the previous 80 years--
the Golden Age of Exploration.
Before the ink was dry,
Ortelius stepped back from his masterpiece
and became the first of many to notice the striking
puzzle-piece fit between the continents
on either side of the Atlantic.
He later wrote that the Americas were torn away
from Europe and Africa by earthquakes and floods.
But Ortelius's observation
remained nothing more than a hunch
for the next couple of centuries...
until an early 20th century
German astronomer and meteorologist
amassed the evidence
to build the scientific case for it.
Alfred Wegener had been drafted during the First World War,
but was wounded soon after.
As he recovered in a field hospital,
he scoured scientific literature
for clues to the Earth's past.
Years before,
Wegener had happened upon an intriguing paper
in the stacks of his university library.
It puzzled Wegener
that fossils of the same species of a now-extinct fern
were reported to be found on both sides of the Atlantic.
Even more curious were the discoveries of fossils
of the same dinosaurs on both continents.
In the early 20th century,
geologists explained how life crossed the oceans
by imagining that land bridges had once existed between them.
It was thought that these land bridges gradually disintegrated
and vanished beneath the waves long ago.
But there was one piece of evidence that convinced Wegener
that the prevailing scientific view must be wrong...
the Earth itself.
Why would a mountain range cross the oceanic divide
to continue on another continent?
And why would you find the same unique pattern
in the layers of rocks in both Brazil and South Africa?
And another thing...
under what circumstances could tropical plants have flourished
in the frozen wastes of the Arctic?
Wegener concluded that there was only
one logical solution to this puzzle...
There had once been a single supercontinent on Earth.
He named it Pangaea.
So Wegener becomes the toast of the scientific world, right?
Not exactly.
Most geologists ridiculed Wegener's hypothesis
of continental drift.
They preferred their imaginary natural land bridges
to explain away Wegener's evidence.
How, they asked, could a continent plow through
the solid rock of the ocean floor?
Wegener had no convincing answer.
He became the laughingstock of the field;
a pariah at scientific conferences.
Despite this, Wegener continued to fight for his ideas,
conducting daring research expeditions to gather evidence.
On one of these, he learned that colleagues were
trapped on an ice cap without food.
On his way back from the mission,
he became lost in a blizzard.
A day or two after his 50th birthday,
he disappeared,
never knowing that, in time,
he would be vindicated and come to be viewed
as one of the greatest geologists in history.
Scientists are human.
We have our blind spots and prejudices.
Science is a mechanism
designed to ferret them out.
Problem is, we aren't always faithful
to the core values of science.
Few people knew this better than Marie Tharp.
It's 1952, and Marie is patiently enduring the slights
of her fellow members of the geology department.
Her degrees in geology and mathematics
count for little with them.
Bruce Heezen, a graduate student from Iowa,
has just returned from a lengthy expedition
to map the ocean floor using sonar.
Will you do something with these?
Bruce, look.
It's-- it's all come together.
There's this giant rift valley
that runs through the bottom of the Atlantic.
Aw, geez, Marie, come on.
This is just more girl talk.
You're not in enough trouble with everyone here already?
This sounds too much like continental drift.
You want to end up like Wegener?
But Marie would not be dissuaded.
Years later, when Marie and Bruce placed a map of oceanic
earthquake epicenters on a light table
over her seafloor map,
the earthquakes fell right along
the rift valley.
This was the smoking gun
for Wegener's moving continents.
Heezen now knew
that Marie had been right all along.
Together, they created the first true map of the Earth,
including the ocean floor.
We were at last ready to read
the autobiography of the Earth.
Let's take the Ship of the Imagination...
to a part of the world that has been off-limits
to all but a few of us.
Two-thirds of the Earth
lies beneath more than 1,000 feet of water.
It's a vast and largely unexplored frontier.
Everybody knows the Alps and the Rockies,
but some of the world's most amazing mountain ranges
are hidden from view.
Below 1,000 meters, we enter a world
where there is no sunlight.
Hidden in the darkness, a world of wonders.
This is the longest submarine mountain range in the world,
the Atlantic Mid-Ocean Ridge.
It wraps around our globe like the seam on a baseball.
The past is another planet,
but most of us don't really know this one.
We don't see the mountains for the water.
This is the world that Marie Tharp was the first to imagine.
The highest peaks of the ridge
rise over four kilometers above
the ocean floor.
There are sprawling mountain ranges and canyons, too.
We've now entered the Marianas Trench,
the deepest canyon on Earth,
more than ten kilometers deep.
It formed when tectonic forces pushed the seabed
under the adjoining continental plate.
More people have walked on the Moon
than have ever been down here.
The pressure here is a crushing eight tons per square inch.
Being this deep in the ocean
is like having 50 jumbo jets stacked on top of you.
Yet even here, life has taken hold.
The fact that sunlight can't penetrate the deep ocean
doesn't mean there isn't light down here.
Many underwater species glow in the dark,
through a process called bioluminescence.
Our long history as land mammals,
denizens of the sunlit world, hasn't prepared us
for the amazing variety of life that evolution
has crafted in the deep oceans.
Since there's no sunlight down here,
there's no photosynthesis.
That means there are no plants to feed on,
and yet, even here, in a world of permanent midnight,
there's a thriving food chain.
It begins
with a process called chemosynthesis.
These microscopic creatures have learned to eat
what's pouring out of that vent...
a noxious compound called hydrogen sulfide.
That thick
black smoke provides the chemical energy
that makes life possible here.
Tiny crustaceans eat the bacteria,
and the larger animals eat the crustaceans.
One day, on some future Earth,
these mountains could very well
end up above the water.
Tectonic forces continue to shape our planet.
The future is also another planet.
It was a volcano like this one
that created the Hawaiian islands millions of years ago.
We live on the crust of a seething cauldron.
At the center of our planet, there's an iron core.
It's nested inside of a larger, liquid iron shell.
Wrapped over this is the part called the mantle.
It's rocky but hot and viscous.
Like a pot of soup cooking on a stove, the mantle
is churning.
What keeps it moving?
Two things... the heat left over from Earth's formation,
and the decay of radioactive elements in the core.
And this outer layer-- the crust,
where you and me and everyone we know lives--
is only as thick as the skin on an apple.
The mantle
drags the solid overlying crust along with it.
The crust resists because it's cool and rigid.
From time to time, it reaches the breaking point.
When that happens, the Earth quakes.
It's not because somebody misbehaved
and is being punished.
It's due to random forces
that are governed by the laws of nature.
Our sense of the stability of the Earth is an illusion
due to the shortness of our lives.
If we could watch our planet on its own timescale,
in which big changes take millions of years to play out,
we would see it as the dynamic organism it really is.
This is the world of the late Triassic period
about 200 million years ago.
That little guy?
It's one of our distant ancestors.
He lived in Newark, New Jersey.
Wherever you walk on Earth...
lost worlds lie buried beneath your feet.
50 or 100 million years ago,
even the most seemingly ordinary places
have been the scene of epic change.
These Palisades are a monument
to the breakup of the supercontinent Pangaea.
The sequence of volcanic eruptions
that made these cliffs also led to the next mass extinction--
the one that ended the Triassic world.
But a catastrophic
extinction event for one species
is a golden opportunity for another.
The Triassic extinctions offered one group
that had been around for a while
the chance to take center stage.
The dinosaurs had a good, long run
for 170 million years.
Back then, India was an island.
It crept northward at the pace of a few inches per year
on its slow but inexorable rendezvous with Asia.
Then, once again,
the molten rock beneath Earth's surface
burst forth and flooded a huge area of western India.
The knockout punch
literally came out of the blue.
Few animals
larger than a hundred pounds
survived the catastrophes of the late Cretaceous.
The dust cloud brought night and cold to the surface for months.
The dinosaurs froze and starved to death.
But there were small creatures
who took shelter in the Earth.
And when they emerged...
they found that the monsters who had hunted
and terrorized them were gone.
The Earth was becoming the Planet of the Mammals.
And the Earth continued its ceaseless changing.
This was once a desert where nothing could grow.
It was a million square miles of sand and salt,
far more hostile than any environment on Earth today.
Daytime temperatures were hot enough to bake bread.
And it was more than a mile below sea level,
so the atmospheric pressure
was about 50% higher than what we're used to.
It would be hard to think
of a more unpromising environment on this planet.
Yet this was the basin of the Mediterranean
five and a half million years ago,
before it became a sea.
The Earth never stops moving for long.
The natural dam at the western end
of the deep basin
gave way, probably due to earthquakes.
And the deluge began.
The torrential waters rushed in at a rate 40,000 times greater
than Niagara Falls, turning a vast desert
into the Mediterranean Sea...
in less than a year.
There were as yet no humans
to witness this enormous flood,
nor to admire the beauty it created.
Meanwhile, half a world away,
a broad channel separated North and South America...
allowing ocean currents to flow
from the Atlantic into the Pacific Ocean.
Tectonic forces gradually brought
these two continents together, closing the channel
and creating the Isthmus of Panama.
This reorganized the worldwide pattern of ocean currents,
which, in turn, affected the global climate.
In Africa, the lush green forest canopy
gave way to a sparser landscape.
Some species
that were highly specialized for life in the trees
became extinct.
But the generalists, the ones that could find a way
to make a living no matter what life threw at them,
endured and evolved.
Our ancestors had once burrowed deep in the ground
to avoid predators who stalked the surface.
But when the dinosaurs perished,
they emerged into the daylight,
and over the eons, made new lives
in the branches of the trees.
They developed opposable thumbs and toes
for swinging from branch to branch,
across the broad canopy of treetops,
where all their needs were fulfilled.
They could also walk upright, but only for short distances.
With so many trees around, they didn't have to go very far.
But then it got colder,
and the trees thinned out,
broad grasslands sprang up, and our ancestors
were forced to traverse them in search of food.
You needed a totally different skill set
to make it on the savanna.
In the old days,
you could sit perched on your tree branch
and watch the big cats from a safe distance.
Now you were playing on the same dangerous field.
The survivors were those who evolved the ability
to walk great distances on their hind legs
and to run when necessary.
This changed the way
they looked at the world.
Hands and arms were no longer tied up with walking.
They were free to gather food and pick up sticks and bones.
These could be used as weapons and tools.
Think of it...
A change in the topography of a small piece of land
half a world away reroutes ocean currents.
Africa grows colder and drier.
Most of the trees can't withstand the new climate.
The primates who lived in them
have to seek other homes, and before you know it,
they're using tools to remake the planet.
The Earth has shaped the course of human destiny,
but so has the invisible pull of distant worlds.
The planets have influenced
our lives, but not in the way you think.
The gravitational pull of Venus--
small but close--
and that of Jupiter-- distant but massive--
tilted the Earth's axis this way and that...
and ever so slightly tweaked the shape of its orbit.
This periodically altered
the amount of sunlight
falling on the edge of the northern ice cap.
Sometimes it made the summers there colder,
and the glaciers advanced southward
from one year to the next,
grinding and scraping,
and crushing everything in their path.
That's what we call an ice age.
At other times, changes in Earth's axis and orbit
made the Arctic summers warmer.
And the melting glaciers began to retreat.
Imagine how resourceful our ancestors had to be
in order to survive these radical changes in climate.
With each glacial period,
the ice sheets grow at the expense of the oceans;
the world sea level falls by more than 400 feet,
uncovering wide areas of land
along the edges of the continents.
15 to 25,000 years ago,
there was a period when the ice receded,
exposing a temporary land bridge.
The gateway to the other half of the planet swings open.
Bands of wanderers crossed the land bridge
to North America and parts south.
About 10,000 years ago, the manic swings
of the climate and sea levels came to a stop.
A new and gentler climate age began.
It's the one we live in now.
When the great ice sheets melted,
the sea rose to its present height
and the rivers carried silt from the highlands
to build great delta plains where they met the sea.
On those fertile plains, we learned a new way of life...
how to grow things, to feed ourselves and more.
For most of us, this meant an end
to a million years of wandering.
The way the planets tug at each other,
the way the skin of the Earth moves,
the way those motions affect climate
and the evolution of life and intelligence--
they all combined to give us the means
to turn the mud of those river deltas
into the first civilizations.
There's nothing like an interglacial period,
one of those balmy intermissions in an ice age.
And the great news is that this one is due to last
for another 50,000 years.
What a break for our kind.
Just one problem.
We can't seem to stop burning up all those
buried trees from way back in the Carboniferous Age,
in the form of coal;
and the remains of ancient plankton,
in the form of oil and gas.
If we could, we'd be home free, climate-wise.
Instead, we're dumping carbon dioxide into the atmosphere
at a rate the Earth hasn't seen
since the great climate catastrophes of the past,
the ones that led to mass extinctions.
We just can't seem to break our addiction to the kinds of fuel
that'll bring back a climate last seen by the dinosaurs;
a climate that will drown our coastal cities and wreak havoc
on the environment and our ability to feed ourselves.
All the while, the glorious sun
pours immaculate, free energy down upon us;
more than we will ever need.
Why can't we summon the ingenuity and courage
of the generations that came before us?
The dinosaurs never saw that asteroid coming.
What's our excuse?
There's a corridor
in the Halls of Extinction that is, right now,
empty and unmarked.
The autobiography of the Earth is still being written.
There's a chance that the end of our story lies in there.
Congratulations.
You're alive.
There's an unbroken thread that stretches across
more than three billion years
that connects us to the first life
that ever touched this world.
Think of how tough, resourceful and lucky
all of our countless ancestors must have been
to survive long enough
to pass on the message of life to the next
and the next...
and the next generation,
hundreds of millions of times...
before it came to us.
There were so many rivers to cross,
so many hazards along the way.
Predators, starvation, disease,
miscalculation, long winters,
drought, flood and violence.
Not to mention the occasional upheavals that
erupted from within our planet and the apocalyptic bolts
that come from the blue. No matter where we hail from
or who our parents were, we are descended
from the hearty survivors of unimaginable catastrophes.
Each of us is a runner in the longest and most dangerous
relay race there ever was,
and at this moment, we hold the baton in our hands.
The past is another planet.
And so is the future.
Some 250 million years from now,
many geologists think that the lands of the Earth
will be united once again.
All this beauty will have vanished
and the Earth of our moment in time
will take its place among the lost worlds.
The great internal engine of plate tectonics
is indifferent to life,
as are the small changes in the Earth's orbit and tilt
and the occasional collisions
with little worlds on rogue orbits.
These processes have no notion of what has been going on
over billions of years on our planet's surface.
They do not care.
Each of us is a tiny being
riding on the outermost skin of one of the smaller planets
for a few dozen trips around the local star.
The things that live the longest on Earth
endure for only about a millionth
of the age of our planet.
So, of course, the individual organisms
see nothing of the overall pattern.
Of changing continents...
climate...
evolution.
That we understand even a little of our origins
is one of the great triumphs of human insight and courage.
Who we are and why we are here can only be glimpsed
by piecing together something of the full picture,
which must encompass eons of time...
millions of species...
and a multitude of worlds.
In this perspective, it's not surprising
that we're a mystery to ourselves and that,
despite our manifest pretension,
we are far from being masters of our own little house.
This new corridor has no name above the entrance
to designate its epoch, and we don't yet know
which failed species will be memorialized within its walls.
What happens here, in countless ways, both large and small,
is being written by us.
Right now.