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00:00yes this is home this is earth having trouble finding a familiar continent the past is another
00:19planet actually many i'm standing on the great expanse of time that has elapsed since the big
00:26bang in order to think about it we've compressed it all into a single year it's the early morning
00:33of december 23rd on this cosmic calendar of hours we're about 350 million years ago when our world
00:40was a mere 4 billion years old earth looks so different you might not even know the place
00:46the stars wouldn't help you even the constellations would have been different back then
00:56the dinosaurs were still more than a hundred million years in the future
01:01there were no birds no flowers and the air was different too
01:07the atmosphere had more oxygen than at any other time in earth's history
01:14before or since this allowed insects to grow much larger than they do today
01:20now insects don't have lungs life-giving oxygen has taken in through openings in the outside of
01:30their bodies and transported through a network of tubes if an insect were too large the outer reaches
01:37of these tubes would absorb all the oxygen before it could ever get to its internal organs
01:41but during the carboniferous period the atmosphere had almost twice the oxygen as today
01:48insects could then grow much bigger and still get enough oxygen in their bodies
01:53that's why the dragonflies here are as big as eagles and the millipedes the size of alligators
02:00so why was there so much oxygen back then it was produced by a new kind of life
02:06and there is no space in the human body
02:07the water is now
02:11much more besides eagles
02:14and the communal sounds
02:18so why were there simply
02:19the birds are very quickly
02:21the birds which Elena has opened in a feelings of Vietnam
02:23so it was just another animal
02:26and it's a work just to eat
02:28so why would you picture an animal
02:31more ethALK
06:04it took in carbon dioxide and water
06:06and used sunlight to turn them into energy-rich organic matter.
06:10The tree gave off oxygen as a waste product.
06:13That's what trees and other plants still do.
06:17When plants die, they decay, and this reverses the transaction.
06:23Their organic matter combines with oxygen and decomposes,
06:27putting carbon dioxide back into the air.
06:30This balances the books for the chemistry of Earth's atmosphere.
06:35But if the trees are buried before they can decay, two things happen.
06:39They take the carbon and the stored solar energy with them
06:42and leave the oxygen behind to build up in the atmosphere.
06:46That's what happened around 300 million years ago.
06:49There was an oxygen surplus.
06:51That's how the bugs got so big.
06:54And what became of all that buried carbon?
06:57It lay there for eons before dealing life on Earth its most devastating blow of all time.
07:08There are places on this planet where you can walk through time
07:12and read the history written in the rocks.
07:15This beach in Nova Scotia is one of them.
07:18Every layer is a page.
07:20Each one tells the story of a flood, one after another, over millions of years.
07:25The layer cake of flood deposits was slowly buried and turned into rock by heat and pressure.
07:32The same forces that built mountains then tilted and uplifted them along with the entombed fossil forest.
07:39The newer layers were always deposited on top of the older ones.
07:43All the pages are in the correct order, bearing witness to what happened here over millions of years.
07:50Back that way lies the more distant past.
07:53And with every step I take, I move about a thousand years closer to the present
07:58and away from the world of 300 million years ago.
08:0250 million years later lies that way.
08:06This was the beginning of the end of the Permian world.
08:18An event of unequaled carnage.
08:21The Permian is the darkest corridor in this memorial to the broken branches on the tree of life.
08:27The halls of extinction.
08:29Death has never come so close to reigning supreme on this world in the quarter billion years since.
08:35The eruptions in what is now Siberia lasted for hundreds of thousands of years.
08:41The lava flooded and buried more than a million square miles.
08:45This event dwarfs any volcanic eruption in historical times.
09:05Huge quantities of carbon dioxide came pouring out of the volcanic fissures.
09:17This greenhouse gas warmed the climate.
09:20And this is where the long buried forests of the earlier carboniferous period re-entered the story.
09:26During the intervening 50 million years, those trees had turned into immense deposits of coal.
09:32And as it happened, one of the world's largest accumulations of coal was buried right there in Siberia.
09:38The heat from the lava baked the coal, driving methane and sulfur-rich gases out of the ground.
09:44They were laden with toxic and radioactive ash particles.
09:49Coal smoke.
09:51This witch's brew polluted the atmosphere and radically destabilized Earth's climate.
09:58A sulfuric acid haze blocked incoming sunlight and darkened the planet.
10:03Global temperatures plummeted to sub-freezing.
10:07During lulls in the eruption, the acid haze fell back to the surface.
10:16But the carbon dioxide remained and built up in the atmosphere to cause global warming.
10:21Years of frigid cold alternating with millennia of stifling heat battered a dwindling population of plants and animals.
10:28They had no chance to adapt to the drastic swings in climate.
10:37As the global warming continued, the surface and the bottom waters slowly mixed, raising the temperature of the once frigid depths of the sea floor.
10:45Methane-rich ices that had been frozen in the sediments began to melt.
10:50Newly liberated methane gas made its way to the surface and into the atmosphere.
11:01Methane traps heat far more efficiently than carbon dioxide.
11:05So the climate got even hotter.
11:08And the methane also destroyed the ozone layer in the stratosphere.
11:12The natural sunscreen that protects life from deadly ultraviolet rays was eaten away.
11:18The circulatory system of the world ocean was shut down.
11:23These stagnant waters became oxygen star, killing almost all the fish in the sea.
11:29But one kind of life flourished in this brutal environment.
11:32Bacteria that produced deadly hydrogen sulfide gas as a waste product.
11:38That was the last straw.
11:41The poison gas killed almost all the remaining plants and animals on the land.
11:47This was the great dying.
11:50The closest life on Earth has ever come to annihilation.
11:54Nine in ten of all species perished.
11:57It took a long time for life to bounce back.
12:00For a few million years, Earth could have been called the planet of the dead.
12:06We are descended from one of the few species that managed to squeak by.
12:13You are human and alive at this very moment.
12:18Because they managed to endure conveying their DNA through one of the most treacherous periods in the history of life.
12:25This mountain was made entirely by life.
12:44The life that flourished back in the glory days of the Permian, before all hell broke loose.
12:48This is part of the 400 mile long Guadalupe mountain chain that runs through Texas and New Mexico.
12:55It's the world's largest fossil reef.
12:58All this was once a great inland sea.
13:01The reef flourished and grew for millions of years and was home to multitudes of sponges, green algae and animals too small to see.
13:12When these creatures died, they sank to the bottom and were buried in the silt.
13:17Over millions of years, their remains were converted into oil and gas.
13:22Eventually, the basin silted in and the reef died.
13:26This marine ghost town was then buried a mile beneath the surface.
13:31Later, tectonic forces lifted the skeletal reef high above sea level, where it was eroded and sculpted over eons by wind and rain.
13:40Just imagine what this place looked like 275 million years ago, when it was a vibrant tropical inland sea, dotted with islands, brimming with life.
13:51Until about 220 million years ago, New England and North Africa were next door neighbors.
14:01There was no such thing as the Atlantic Ocean.
14:04Those thin blue fingers at the center, they were lakes.
14:08They were the first outward signs that the supercontinent was splitting apart and that life on Earth was due for another big shakeup.
14:16A million years later, the lakes became a long bay, which would grow into the Atlantic Ocean.
14:22These profound changes at the surface were merely symptoms of a drama that was unfolding far beneath in the depths of the Earth.
14:30By the time we got here, the telltale traces of global upheaval were buried at the bottom of the deep blue sea.
14:39We were completely cut off from the great story of Earth's violent past.
14:43A species of amnesiacs trying to find out who we were and what happened before we awakened.
14:52In 1570, Abraham Ortelius created the first modern world atlas, reflecting the discoveries of the previous 80 years, the golden age of exploration.
15:04Before 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.
15:17He later wrote that the Americas were torn away from Europe and Africa by earthquakes and floods.
15:23But Ortelius' observation remained nothing more than a hunch for the next couple of centuries.
15:30Until an early 20th century German astronomer and meteorologist amassed the evidence to build the scientific case for it.
15:38Alfred Wagner had been drafted during the First World War, but was wounded soon after.
15:44As he recovered in a field hospital, he scoured scientific literature for clues to the Earth's past.
15:51Years before, Wagner had happened upon an intriguing paper in the stacks of his university library.
15:58It puzzled Wagner that fossils of the same species of a now extinct fern were reported to be found on both sides of the Atlantic.
16:07Even more curious were the discoveries of fossils of the same dinosaurs on both continents.
16:14In the early 20th century, geologists explained how life crossed the oceans by imagining that land bridges had once existed between them.
16:23It was thought that these bridges gradually disintegrated and vanished beneath the waves long ago.
16:29But there was one piece of evidence that convinced Wagner that the prevailing scientific view must be wrong.
16:36The Earth itself.
16:39Why would a mountain range cross the oceanic divide to continue on another continent?
16:44And why would you find the same unique pattern in the layers of rocks in both Brazil and South Africa?
16:50And another thing, under what circumstances could tropical plants have flourished in the frozen wastes of the Arctic?
16:57Wagner concluded that there was only one logical solution to this puzzle.
17:03There had once been a single supercontinent on Earth.
17:07He named it Pangaea.
17:10So, Wagner becomes the toast of the scientific world, right?
17:14Not exactly.
17:16Most geologists ridiculed Wagner's hypothesis of continental drift.
17:21They preferred their imaginary natural land bridges to explain away Wagner's evidence.
17:28How, they asked, could a continent plow through the solid rock of the ocean floor?
17:34Wagner had no convincing answer.
17:37Became the laughing stock of the field, a pariah at scientific conferences.
17:43Despite this, Wagner continued to fight for his ideas, conducting daring research expeditions to gather evidence.
17:52On one of these, he learned that colleagues were trapped on an ice cap without food.
17:57On his way back from the mission, he became lost in a blizzard.
18:02A day or two after his 50th birthday, he disappeared.
18:06Never knowing that, in time, he would be vindicated and come to be viewed as one of the greatest geologists in history.
18:13Scientists are human.
18:21We have our blind spots and prejudices.
18:24Science is a mechanism designed to ferret them out.
18:28Problem is, we aren't always faithful to the core values of science.
18:33Few people knew this better than Marie Tharp.
18:38It's 1952, and Marie is patiently enduring the slights of her fellow members of the geology department.
18:49Her degrees in geology and mathematics count for little with them.
18:53Bruce Heason, a graduate student from Iowa, has just returned from a lengthy expedition to map the ocean floor using sonar.
19:01Will you do something with these?
19:06Bruce, look. It's all come together. There's this giant rift valley that runs through the bottom of the Atlantic.
19:19Ah, jeez, Marie, come on. This is just more girl talk. You're not in enough trouble with everyone here already?
19:25This sounds too much like continental drift. You want to end up like Wegner?
19:29But Marie would not be dissuaded.
19:35Years 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.
19:46This was the smoking gun for Wegner's moving continents.
19:51Heason now knew that Marie had been right all along.
19:55Together, they created the first true map of the Earth, including the ocean floor.
20:01We were at last ready to read the autobiography of the Earth.
20:08Let'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.
20:20Two thirds of the Earth lies beneath more than a thousand feet of water.
20:39It's a vast and largely unexplored frontier.
20:42Everybody knows the Alps and the Rockies, but some of the world's most amazing mountain ranges are hidden from view.
20:52Below a thousand meters, we enter a world where there is no sunlight.
20:59Hidden in the darkness, a world of wonders.
21:04This is the longest submarine mountain range in the world.
21:09The Atlantic Mid-Ocean Ridge.
21:12It wraps around our globe like the seam on a baseball.
21:20The past is another planet.
21:23But most of us don't really know this one.
21:26We don't see the mountains for the water.
21:29This is the world that Marie Tharp was the first to imagine.
21:33The highest peaks of the ridge rise over four kilometers above the ocean floor.
21:38There are sprawling mountain ranges and canyons too.
21:42We've now entered the Marianas Trench, the deepest canyon on Earth.
21:47More than ten kilometers deep.
21:49It formed when tectonic forces pushed the seabed under the adjoining continental plate.
21:54More people have walked on the moon than have ever been down here.
21:59The pressure here is a crushing eight tons per square inch.
22:04Being this deep in the ocean is like having 50 jumbo jets stacked on top of you.
22:10Yet even here, life has taken hold.
22:14The fact that sunlight can't penetrate the deep ocean doesn't mean there isn't light down here.
22:22Many underwater species glow in the dark through a process called bioluminescence.
22:28Our 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.
22:43Since there's no sunlight down here, there's no photosynthesis.
22:48That means there are no plants to feed on.
22:51And yet even here, in a world of permanent midnight, there's a thriving food chain.
22:57It begins with a process called chemosynthesis.
23:00These microscopic creatures have learned to eat what's pouring out of that vent.
23:05A noxious compound called hydrogen sulfide.
23:10That thick black smoke provides the chemical energy that makes life possible here.
23:16Tiny crustaceans eat the bacteria.
23:19And the larger animals eat the crustaceans.
23:27One day on some future Earth, these mountains could very well end up above the water.
23:32Tectonic forces continue to shape our planet.
23:37The future is also another planet.
23:40It was a volcano like this one that created the Hawaiian Islands millions of years ago.
24:02We live on the crust of a seething cauldron.
24:11At the center of our planet, there's an iron core.
24:14It's nested inside of a larger liquid iron shell.
24:17And wrapped over this is the part called the mantle.
24:21It's rocky, but hot and viscous.
24:24Like a pot of soup cooking on a stove, the mantle is churning.
24:29What keeps it moving?
24:31Two things.
24:32The heat left over from Earth's formation.
24:34And the decay of radioactive elements in the core.
24:38And this outer layer, the crust, where you and me and everyone we know lives,
24:43it's only as thick as the skin on an apple.
24:47The mantle drags the solid overlying crust along with it.
24:51The crust resists because it's cool and rigid.
24:54From time to time, it reaches the breaking point.
24:58When that happens, the Earth quakes.
25:02It's not because somebody misbehaved and is being punished.
25:06It's due to random forces that are governed by the laws of nature.
25:10Our sense of the stability of the Earth is an illusion due to the shortness of our lives.
25:16If we could watch our planet on its own time scale, in which big changes take millions of years to play out, we would see it as the dynamic organism it really is.
25:30This is the world of the late Triassic period, about 200 million years ago.
25:40And that little guy is one of our distant ancestors.
25:46He lived in Newark, New Jersey.
25:50Wherever you walk on Earth,
25:54lost worlds lie buried beneath your feet.
25:5850 or 100 million years ago, even the most seemingly ordinary places have been the scene of epic change.
26:06These palisades are a monument to the breakup of the supercontinent Pangea.
26:12The sequence of volcanic eruptions that made these cliffs also led to the next mass extinction.
26:18The one that ended the Triassic world.
26:20But a catastrophic extinction event for one species is a golden opportunity for another.
26:30The Triassic extinctions offered one group that had been around for a while the chance to take center stage.
26:40The dinosaurs had a good long run for 170 million years.
26:45Back then, India was an island.
26:49It crept northward at the pace of a few inches per year on its slow but inexorable rendezvous with Asia.
26:57Then, once again, the mulch and rock beneath Earth's surface burst forth and flooded a huge area of Western India.
27:13The knockout punch literally came out of the blue.
27:17SQUARE!
27:18This is a new ingredient of the two cities that we've been coming up!
27:19This is a new ingredient in the region.
27:20The
27:46Few animals larger than a hundred pounds survived the catastrophes of the late Cretaceous.
28:00Dust cloud brought night and cold to the surface for months.
28:04The dinosaurs froze and starved to death.
28:07But there were small creatures who took shelter in the earth.
28:10And when they emerged, they found that the monsters who had hunted and terrorized them were gone.
28:17The earth was becoming the planet of the mammals.
28:21And the earth continued its ceaseless changing.
28:27This was once a desert where nothing could grow.
28:30It was a million square miles of sand and salt.
28:34Far more hostile than any environment on earth today.
28:37Daytime temperatures were hot enough to bake bread.
28:41And it was more than a mile below sea level.
28:44So the atmospheric pressure was about 50% higher than what we're used to.
28:48It would be hard to think of a more unpromising environment on this planet.
28:53Yet this was the basin of the Mediterranean five and a half million years ago, before it became a sea.
29:00The earth never stops moving for long.
29:02The natural dam at the western end of the deep basin gave way, probably due to earth breaks.
29:10And the deluge began.
29:13The torrential waters rushed in at a rate 40,000 times greater than Niagara Falls,
29:18turning a vast desert into the Mediterranean Sea in less than a year.
29:24There were as yet no humans to witness this enormous flood, nor to admire the beauty it created.
29:33Meanwhile, half a world away, a broad channel separated North and South America,
29:39allowing ocean currents to flow from the Atlantic into the Pacific Ocean.
29:43Tectonic forces gradually brought these two continents together, closing the channel and creating the Isthmus of Panama.
29:52This reorganized the worldwide pattern of ocean currents, which in turn affected the global climate.
29:58In Africa, the lush green forest canopy gave way to a sparser landscape.
30:07Some species that were highly specialized for life in the trees became extinct.
30:13But the generalists, the ones that could find a way to make a living no matter what life threw at them,
30:18endured and evolved.
30:20Our ancestors had once burrowed deep in the ground to avoid predators who stalked the surface.
30:30But when the dinosaurs perished, they emerged into the daylight,
30:34and over the eons, made new lives in the branches of the trees.
30:38They developed opposable thumbs and toes for swinging from branch to branch
30:42across the broad canopy of treetops, where all their needs were fulfilled.
30:46They could also walk upright, but only for short distances.
30:50With so many trees around, they didn't have to go very far.
30:54But then it got colder, and the trees thinned out.
30:58Broad grasslands sprang up, and our ancestors were forced to traverse them in search of food.
31:03You needed a totally different skill set to make it on the savannah.
31:07In the old days, you could sit perched on your tree branch and watch the big cats from a safe distance.
31:12Now, you were playing on the same dangerous field.
31:19The survivors were those who evolved the ability to walk great distances on their hind legs,
31:25and to run when necessary.
31:28This changed the way they looked at the world.
31:31Hands and arms were no longer tied up with walking.
31:34They were free to gather food and pick up sticks and bones.
31:38These could be used as weapons and tools.
31:40Think of it.
31:43A change in the topography of a small piece of land half a world away reroutes ocean currents.
31:50Africa grows colder and drier.
31:52Most of the trees can't withstand the new climate.
31:55The primates who lived in them have to seek other homes.
31:59And before you know it, they're using tools to remake the planet.
32:02The Earth has shaped the course of human destiny.
32:07But so has the invisible pull of distant worlds.
32:10The planets have influenced our lives.
32:39Not in the way you think.
32:41The gravitational pull of Venus, small but close.
32:46And that of Jupiter, distant but massive.
32:50Tilted the Earth's axis.
32:53This way and that.
32:54And ever so slightly tweaked the shape of its orbit.
33:03This periodically altered the amount of sunlight falling on the edge of the northern ice cap.
33:07Sometimes it made the summers there colder.
33:14And the glaciers advanced southward from one year to the next.
33:17Grinding and scraping and crushing everything in their pad.
33:20That's what we call an ice age.
33:25At other times, changes in Earth's axis and orbit made the Arctic summers warmer.
33:30And the melting glaciers began to retreat.
33:36Imagine how resourceful our ancestors had to be in order to survive these radical changes in climate.
33:42With each glacial period, the ice sheets grow at the expense of the oceans.
33:46The world's sea level falls by more than 400 feet, uncovering wide areas of land along the edges of the continents.
33:5515,000 to 25,000 years ago, there was a period when the ice receded, exposing a temporary land bridge.
34:02The gateway to the other half of the planet swings open.
34:07Bands of wanderers cross the land bridge to North America and parts south.
34:11About 10,000 years ago, the manic swings of the climate and sea levels came to a stop.
34:18A new and gentler climate age began.
34:22It's the one we live in now.
34:25When the great ice sheets melted, the sea rose to its present height.
34:29And the rivers carried silt from the highlands to build great delta plains where they met the sea.
34:36On those fertile plains, we learned a new way of life.
34:40How to grow things, to feed ourselves, and more.
34:44For most of us, this meant an end to a million years of wandering.
34:50The way the planets tug at each other, the way the skin of the Earth moves,
34:54the way those motions affect climate, and the evolution of life and intelligence,
35:00they all combined to give us the means to turn the mud of those river deltas into the first civilizations.
35:09There's nothing like an interglacial period, one of those balmy intermissions in an ice age.
35:15And the great news is that this one is due to last for another 50,000 years.
35:24What a break for our kind.
35:28Just one problem.
35:29We can't seem to stop burning up all those buried trees from way back in the Carboniferous Age,
35:35in the form of coal,
35:37and the remains of ancient plankton in the form of oil and gas.
35:41If we could, we'd be home-free, climate-wise.
35:47Instead, we're dumping carbon dioxide into the atmosphere,
35:50at a rate the Earth hasn't seen since the great climate catastrophes of the past,
35:55the ones that led to mass extinctions.
35:58We just can't seem to break our addiction
36:01to the kinds of fuel that'll bring back a climate last seen by the dinosaurs,
36:05a climate that will drown our coastal cities
36:08and wreak havoc on the environment and our ability to feed ourselves.
36:14All the while, the glorious sun pours immaculate free energy down upon us,
36:20more than we will ever need.
36:23Why can't we summon the ingenuity and courage of the generations that came before us?
36:28The dinosaurs never saw that asteroid coming.
36:32What's our excuse?
36:44There is a corridor in the halls of extinction
36:47that is, right now, empty and unmarked.
36:51The autobiography of the Earth is still being written.
36:54Then, there's a chance that the end of our story lies in there.
37:06Congratulations.
37:09You're alive.
37:11There's an unbroken thread that stretches across more than 3 billion years
37:16that connects us to the first life that ever touched this world.
37:21Think of how tough, resourceful, and lucky all of our countless ancestors must have been
37:28to survive long enough to pass on the message of life to the next
37:33and the next
37:36and the next generation
37:38hundreds of millions of times
37:42before it came to us.
37:49There were so many rivers to cross, so many hazards along the way.
37:58Predators, starvation, disease, miscalculation, long winters, drought, flood, and violence.
38:06Not to mention the occasional upheavals that erupted from within our planet
38:10and the apocalyptic bolts that come from the blue.
38:13No matter where we hail from, or who our parents were,
38:16we are descended from the hardy survivors of unimaginable catastrophes.
38:21Each of us is a runner in the longest and most dangerous relay race there ever was.
38:26And at this moment, we hold the baton in our hands.
38:36The past is another planet.
38:41And so is the future.
38:44Some 250 million years from now,
38:47many geologists think that the lands of the earth will be united once again.
38:54All this beauty will have vanished and the earth of our moment in time will take its place among the lost worlds.
39:13The great internal engine of plate tectonics is indifferent to life,
39:18as are the small changes in the earth's orbit, tilt, and the occasional collisions with little worlds on rogue orbits.
39:26These processes have no notion of what has been going on over billions of years on our planet's surface.
39:32They do not care.
39:35Each of us is a tiny being,
39:38riding on the outermost skin of one of the smaller planets
39:41for a few dozen trips around the local star.
39:47The things that live the longest on earth endure for only about a millionth the age of our planet.
39:53So, of course, the individual organisms see nothing of the overall pattern of changing continents,
40:02climate,
40:05evolution.
40:07That we understand even a little of our origins is one of the great triumphs of human insight and courage.
40:14Who we are and why we are here can only be glimpsed by piecing together something of the full picture,
40:20which must encompass eons of time,
40:25millions of species,
40:30and a multitude of worlds.
40:40In this perspective, it's not surprising that we're a mystery to ourselves,
40:44that despite our manifest pretension,
40:47we are far from being masters of our own little house.
40:56This new corridor has no name above the entrance to designate its epoch,
41:00and we don't yet know which failed species will be memorialized within its walls.
41:05What happens here, in countless ways, both large and small,
41:11is being written by us,
41:14right now.