- 2 days ago
Look at how geology has shaped human history. He explores the newest force, humans, whose impact is both positive and negative.
Iain Stewart教授带领观众探究几个世纪以来，地质学、地理学和气候是如何影响人类生活的。我们的星球拥有惊人的力量。本片将历史故事的讲述和炫目的摄影镜头紧密结合，呈现一幅原汁原味的人类历史图景
Iain Stewart教授带领观众探究几个世纪以来，地质学、地理学和气候是如何影响人类生活的。我们的星球拥有惊人的力量。本片将历史故事的讲述和炫目的摄影镜头紧密结合，呈现一幅原汁原味的人类历史图景
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TVTranscript
00:17Our planet has immense power, and for most of human history, it has dominated us.
00:31In the series so far, we've seen how the forces of the planet, the deep earth, wind, fire, and water,
00:45have all had major impacts on human history.
00:54But now the relationship between us and the planet is changing.
01:00We're no longer at its mercy. We have now become a major planetary force.
01:08Even in the wildest corners of the earth, you can't escape our human influence.
01:16The question is, what does that mean for our future?
01:23The answer is to give.
01:24The answer is to give.
01:51changing relationship with the planet this vast expanse of mud is the place to come
02:00this is no ordinary mud the towering column of steam shows that this mud
02:07is emerging from within the earth at boiling point
02:18this is indonesia one of the most volcanically active countries on earth
02:24a clue to the source of this unusual phenomenon
02:31this is a volcano but it's not spewing out molten lava it's a mud volcano
02:46it began erupting in 2006 and for the people who live here it's been a disaster
02:57around 30 000 people have been displaced by the mud flow
03:01and around 10 000 homes have been destroyed
03:12today there's a real sense of desolation
03:24drilling engineer harry edi arso has been following the volcano since it began erupting
03:31as you can see that this village is filled with cold water
03:37this is the cause of a very strong wind
03:41according to the opinion
03:43this village is filled with 250 000 barrels per day
03:51and it has been flooded several villages in this area
04:04Over six and a half square kilometers have now been turned to wasteland.
04:13But there's something that makes this eruption unique.
04:17And that's what it was caused by.
04:26This is a natural hazard.
04:29But from my perspective as a drilling engineer,
04:33and based on the data that I received from Jawa Timur,
04:37we concluded that this is an incident that caused a mistake in the operation.
04:47In 2006, developers were drilling in search of gas.
04:51But at around 3,000 meters, they withdrew the drill.
04:56The pressure in the well then dropped, which sucked in hot water from surrounding rock.
05:05This caused fractures in the rock.
05:08Water burst through and shot upwards, mixing with layers of mudstone
05:13to form a liquid mud that boiled to the surface.
05:25Every day, enough mud emerges to fill more than 40 Olympic-sized swimming pools.
05:40To try to contain the flow, enormous levees have been constructed.
05:46Wallowing machines are still trying to channel mud away from the surrounding villages.
05:54Concrete blocks have even been thrown into the center of the volcano in an attempt to plug it.
06:01But every effort to hold back this relentless tide has failed.
06:09This eruption symbolizes our strange relationship with the planet today.
06:15We have an incredible power over it, but often fail to control that power.
06:24It's easy to see our impact on the planet in a negative light.
06:29The story of an Eden destroyed.
06:34But our relationship with the Earth is far more intriguing and surprising than that.
06:40We have a much longer history of transforming the planet than you might think.
06:46And not all those changes have been bad news.
06:53To go back to the start of the story, we need to go to the Canadian Rocky Mountains.
07:18These dramatic peaks and deep valleys have been sculpted by one of the Earth's great cycles.
07:27It's a cycle that has transformed the surface of the planet.
07:32And has also been critically important in our history.
07:40It's the cycle of the ice ages.
07:52For around 3 million years, our planet has been swinging back and forth between long, cold periods,
07:59when these mountains were embedded in the ice,
08:01and shorter warm periods, like the one we're in now.
08:07The ice waxed and waned according to small changes in the Earth's orbit.
08:12And that influenced the amount of heat falling on different parts of the Earth's surface.
08:20When climatologist Bill Rudiman compared these past cycles to our current cycle,
08:25he noticed something different.
08:28In the last 10,000 years, we should have been moving from a time of no ice sheets
08:34in the direction of a time when the next glaciation should have begun.
08:40And I have evidence to support the idea that we should have small ice sheets present on North America
08:47and parts of northern Eurasia right now.
08:52Today, we would be heading into a new ice age.
08:56And if that were the case, the Rockies would look very different.
09:04Ice would have crept down and smothered this whole valley.
09:17In Europe, the glaciers of the Alps would have spread out across alpine meadows.
09:25These glaciers would be growing vertically and expanding outward.
09:31This would be a much colder climate, and so these masses of ice would be expanding.
09:41But fortunately for us, this ice age didn't happen.
09:49So what prevented the ice following the same rhythms it had followed in the past?
09:56There's a clue in the timing.
09:58Just when it should have been getting cooler, a major change to the planet was underway.
10:09Farming.
10:12It's thought that farming began around 11,000 years ago in the Middle East,
10:17in what's known as the Fertile Crescent.
10:23It took a while to catch on, but by 7,000 years ago it was spreading fast across Europe and
10:29Asia.
10:35Even though our numbers were still small, farming had a big impact on the planet.
10:43Fires were used to clear the forests for farmland, which increased the amount of carbon dioxide in the atmosphere.
10:52We domesticated wild animals, which produce a lot of methane.
10:58Both carbon dioxide and methane are powerful greenhouse gases.
11:06This new theory suggests that the gentle rise in greenhouse gases meant that instead of temperatures falling as they had
11:14in the past, they stayed steady.
11:18The rise of farming was enough to halt the onset of the next ice age.
11:33It's fascinating to think that as far back as 7,000 years ago, we had already made an impact on
11:40the planet at a global scale.
11:43This was the beginning of our role as a force of planetary change.
11:57Since then, human progress has been defined by our ability to find ever more inventive ways of exploiting the planet's
12:06natural systems.
12:10Around 5,000 years ago, our ancestors discovered that trapped within certain types of rock were metal ores.
12:21These mineral-rich rocks were formed deep inside the earth over millions of years.
12:27The metals they released could be transformed into tools, the foundation of civilisation.
12:40By 2,000 years ago, people had found ingenious ways to intercept the water cycle.
12:46They tapped fresh water underneath deserts and used it to create some of the first cities.
12:58Around 500 years ago, sailors learnt how to exploit the power of the earth's wind systems.
13:06They used them to develop global ocean trade routes.
13:15And more recently, we discovered that the fossilised remains of plants and animals, coal and oil, could become major sources
13:24of energy.
13:35Each of these discoveries was a landmark in our ability to use planetary systems for our own purposes.
13:58Today, the way in which we use the earth's resources can be summed up by this.
14:11For aerospace engineer Dave Rowe, aeroplanes are one of civilisation's greatest achievements.
14:24In just a little over 100 years, we have gone from not having the capability of flying at all to
14:34flying at Mach 2.
14:39But now think of these planes from a geological perspective.
14:45The primary structure of these aircraft is predominantly aluminum, which begins life in a natural sense as bauxite borer.
14:56It's the most abundant metallic element in the earth's crust, which has been concentrated within rock over millions of years.
15:06The glass in the aircraft is not really glass, it is a plastic.
15:13Perspex.
15:14In its most basic form, oil.
15:18It's made inside the earth over hundreds of thousands of years from dead organic matter.
15:25And the wiring is made of copper from a mineral called malachite.
15:39These planes are a huge conglomeration of natural resources that have all been precisely extracted, transformed, moulded and connected by
15:52us.
16:00And what's staggering is the scale on which we do this.
16:06This air base in the Arizona desert is home to over 4,000 planes.
16:11Many of them will never fly again.
16:17Effectively, this is a vast accumulation of the planet's minerals.
16:34Our impact on the planet is felt not just in what we transform,
16:39but also in what that transformation leaves behind.
16:50Rivers carry and deposit sediment.
16:53And with it, natural elements such as pollen grains, shells and plant fragments.
16:59It's this mixture that forms the rocks of the future.
17:05But in this particular river, scientist Shelley Moore is studying something quite different.
17:14Plastics go out through our storm drains and our rivers and streams.
17:19A lot of it floats, but some of it does sink and it goes into the sediment.
17:24But it's not just large bits of plastic like bags and bottles.
17:29Increasingly, Shelley's finding smaller fragments buried amongst the natural sediment.
17:35We're actually looking through the sediment to see what kinds of smaller plastic that we can find.
17:41Most people, they're familiar with the larger plastic that has an aesthetic effect on our beaches and in our waterways.
17:49But we also think that some of the smaller plastic is becoming an increasing problem.
17:57Now that may not be so surprising when you consider exactly where this river is.
18:05Right in the center of Los Angeles.
18:08Home to around 4 million people and all that goes with them.
18:15But the impact of plastics reaches much further than major cities.
18:22Globally, around 26 million tons of plastic ends up in the ocean every year.
18:28Where it becomes part of something much bigger.
18:35In the Pacific Ocean, plastic from America is swept into a large revolving ocean current known as a gyre.
18:44As this current circulates, it also picks up material from East Asia.
18:52Over time, these plastics accumulate in enormous flotillas.
19:00One of them is so big, it's even got its own name.
19:05The Eastern Pacific Garbage Patch.
19:14Eventually, the plastic is broken down by the sun's ultraviolet rays into smaller particles
19:20that sink to the seafloor where they're buried.
19:26It's the first stage in their transformation into sedimentary rock.
19:38The Grand Canyon is a striking example of the scale this process operates on.
19:48These cliffs were once an ancient seabed, formed over millions of years as layer after layer of sediment built up.
19:59Under immense pressure, these layers were cemented together to form the rock strata we see today.
20:09The plastics that lie at the bottom of the ocean will eventually form part of the rocks of the future.
20:22On a planetary scale, our enduring signature, one of the main things that will mark out mankind's time on Earth,
20:31will be the remains of millions of tonnes of plastic.
20:35Our geological legacy.
20:44Our ability to take the Earth's resources and transform and deposit them in vast quantities means we've now made an
20:52indelible mark
20:53in the planet's four-and-a-half-billion-year history.
21:15We can slice the tops off mountains and dig holes big enough to bury a city.
21:26In a single year, we now move more Earth than rock than all the natural processes of erosion put together.
21:40Our machines have transformed the planet.
21:54So great is our impact on the Earth that it has been used to define a new geological epoch.
22:06The Anthropocene.
22:08The human epoch.
22:19If you add together all the landscapes we've altered, our cities, towns, villages and farmland,
22:27then 75% of the Earth's ice-free landmass owes its appearance to us.
22:38This truly is a human planet.
22:46It's a human life.
22:51It's a human life.
22:55Sometimes, our intervention in the planet's natural processes can have surprising and far-reaching consequences.
23:06Capa, South Dakota. Founded 1907. Population, one.
23:19In the early 1900s, this was a boomtown. Farmers poured into the Great Plains of the Western USA
23:30to develop new land on the fertile soil.
23:38It can take more than 500 years to create just two centimetres of topsoil.
23:44It's kept in place by vegetation. Grasses bind it together.
23:51But here in Capa, the first settlers ploughed over those grasses
23:56and exposed the delicate soil underneath, which dried out in the sun.
24:02The town's last remaining resident, Phil O'Connor, remembers how it happened.
24:08Some of the trouble was they didn't farm like they should have.
24:12They'd leave the dirt lying on the fields without any protection
24:16and then the wind would catch that dirt and blow it.
24:19The farmers of Capa were dealing with something extremely fragile.
24:24I think they just...
24:26I probably assumed there'd be a regular degree of rain every summer,
24:31a certain pattern that would follow, and it didn't do that.
24:35When the rains failed in the 1930s,
24:38the ploughed up soil was exposed to the full force of the wind.
24:43The result was devastating.
24:46It became known as the Dust Bowl.
24:51It was dusty. It was hazy because of the...
24:53It was sort of a cloud coming up from the ground.
24:58It wouldn't blot the sun out, but it would affect it.
25:01You knew.
25:01And then there was the smell of the dust too.
25:05After 10 years,
25:08100 million acres of farmland turned to wasteland,
25:12and half a million people in the Great Plains were made homeless.
25:2380 years on from the lessons of the Dust Bowl,
25:26we still struggle to manage soils properly.
25:35In China, deforestation and overgrazing means soils are being degraded
25:4130 times faster than the planet's natural processes can replenish them.
25:49In Australia, clearing large areas of bush for farmland
25:54has allowed salt to infiltrate the topsoil,
25:57damaging around 60,000 square kilometres.
26:07In total, 25% of the world's farmland has now been degraded as an inadvertent consequence
26:15of our drive to increased food production.
26:22There's now an extraordinary contrast between the Earth's natural environments
26:28and the ones that we've created.
26:35To fully appreciate the extent of our interference in the planet's natural processes,
26:41take a look at one of the Earth's most fundamental cycles.
26:50The water cycle.
26:55Rain that falls over mountains makes its way into streams and rivers.
27:04This is the Lena River.
27:09Its headwaters are in the Baikal Mountains, where rain and snow melt set the cycle going.
27:18It travels four and a half thousand kilometres across Siberia,
27:25before it reaches a huge delta, on the edge of the Arctic Ocean.
27:33Here, it returns water to the sea, which evaporates to form clouds,
27:38and the cycle begins again.
27:48The Lena is one of the few major rivers that still completes the water cycle from source to sea,
27:55without a single man-made interruption.
28:03Today, we've created an alternative water cycle.
28:12This is part of the Colorado River system.
28:16Along its 2,000-kilometre length, it has over 20 dams.
28:23So much water is diverted to the cities and farmland of the American West,
28:28that most years, it no longer reaches the sea.
28:36The biggest city it supplies is Los Angeles.
28:42Fresh water is delivered across hundreds of kilometres of desert,
28:47via a network of aqueducts, canals and pipelines.
28:52This system delivers 90% of the city's fresh water.
28:57Without it, LA wouldn't exist.
29:04The veins and arteries of our water supply are the lifeblood of our civilisation.
29:17And the human version of this planetary cycle operates at a global scale.
29:24We have altered the planet's water cycle to such an extent,
29:28that five times as much fresh water is stored in reservoirs as flows in all the world's rivers.
29:40This change in the balance of power between us and the planet
29:45is based more than anything on our ability to exploit one particular resource.
30:05This is the Athabasca River in the heart of Alberta, Canada.
30:12It might not look like it, but today this is a new frontier,
30:17and one of our great geological quests.
30:20The hunt for oil.
30:25Oil is central to our lives.
30:29It fuels a mechanised world.
30:33It's a concentrated form of energy, easily transported.
30:39Every year we burn around 31 billion barrels of it.
30:44That's 1,000 barrels a second.
30:48The problem is, it won't last forever.
30:52The amount of oil we're burning each year
30:55takes the planet over three million years to make.
31:04Finding more oil is getting harder.
31:11Some say that oil production can no longer keep pace with demand.
31:15Others say there's still plenty of oil in the ground,
31:18and it's just a case of finding it.
31:22For those in the second camp, this is one of their prime exhibits.
31:28Petroleum engineer Mike Ranger is an expert on the geology of this area.
31:35This is an outcrop,
31:37and this is actually some of the richest bitumen deposits that we have.
31:41It may not look very interesting until you break open the surface.
31:45The surface is typically weathered grey,
31:47but when you open it up, you will see how rich this actually is.
31:53Oh, here we go.
31:55See how dark and rich.
31:56Now that's about 15% by weight oil.
32:00So we're looking here at just a mixture of oil and sand.
32:05That mixture is called tar sand.
32:10This face, this is the way we observe it in nature along the riverbanks.
32:14This is the weathered face of a resource.
32:16But when it comes to recovering the resource,
32:19the real story starts at the top of the cliff over and onto the plateau.
32:37This oil deposit is thought to contain almost a trillion barrels of oil.
32:43It covers 50,000 square kilometres.
32:50To get at the tar sands involves scraping the surface off vast tracts of land.
32:57This is strip mining for oil.
33:02Although it's at the surface, it's much harder to extract than conventional oil.
33:08To separate the oil from the sand,
33:11huge volumes of steam have to be injected into it.
33:14And that's expensive.
33:17In a traditional oil well,
33:19you'd expect around 25 barrels of oil back
33:22for every one barrel of energy you use to extract it.
33:26Here, it's more like one barrel of energy in,
33:29and only five barrels back.
33:34There's no doubt that this is messy oil.
33:36We all have our fingers stained at this point.
33:39It's messy oil, but it is an oil nonetheless,
33:42and there's a huge amount of energy tied up in these oil sands.
33:46In the future, this is what we're going to be using.
33:50This is what we're going to come down to.
33:54This may not be the ideal solution,
33:57but as far as oil's concerned,
33:59the tar sands of Western Canada are one of our best prospects.
34:08For centuries, our ingenuity has enabled us to find new forms of energy,
34:14and so it's easy to think that trend will continue.
34:22History tells us we don't tend to run out of resources.
34:25Instead, we find new ones to exploit.
34:29But that's just a lesson from human history.
34:32The planet's history has another perhaps more important lesson for us.
34:40It's a lesson about the most dramatic human influence on the planet,
34:45the speed and scale at which we're changing the atmosphere.
34:57With the Industrial Revolution came the widespread burning of fossil fuels,
35:01and this dramatically changed the composition of gases in the atmosphere.
35:09Levels of carbon dioxide and methane are higher than at any time in the last 15 million years.
35:20We can already see some of the effects.
35:24The thickness of Arctic sea ice has almost halved.
35:30Some of the extra carbon dioxide we've pumped into the atmosphere has been absorbed by the oceans.
35:37This has increased their acidity by 30%, hindering the growth of marine creatures like corals.
35:47Over the last few decades, the frequency of extreme hurricanes has doubled in some areas.
35:58We're at the beginning of a dramatic period of change.
36:02At the heart of it is the greenhouse effect.
36:05A global warming caused by the gases we release.
36:13The question is, how will the planet and our civilization respond to this change?
36:21One way to answer these questions is to look back into the Earth's past.
36:28A good place to do that is off the coast of California.
36:37The surface of the ocean here is bubbling.
36:43Ira Liefer is a physicist who has been studying this unusual phenomenon.
36:50As well as collecting and analyzing the gas coming from the bubbles,
36:54divers collect it at its source on the seabed.
37:00I've been studying the coal oil point seeps and other seeps for about half a decade now.
37:06And they're really interesting because of the bubbles, the geology, the methane that contributes to greenhouse warming.
37:17The bubbles are made of methane.
37:20And they are key to unlocking one of the Earth's great events.
37:33Today, only relatively small amounts of methane bubble out from seeps like this at the bottom of the ocean.
37:40But 55 million years ago, methane started to erupt from the ocean in massive quantities.
37:47In the past, there's evidence that processes similar to what you've seen here
37:53have occurred on a widespread nature throughout the globe.
37:56And by understanding what happened in the past and how it changed climate,
38:01we can get a better idea of what may happen in the future
38:03and how to best address our own contribution to the global climate effect.
38:14methane is 20 times more potent than carbon dioxide as a greenhouse gas.
38:20And as it burst up through those ancient oceans, it led to sudden runaway global warming.
38:33So what did that mean for life?
38:39The answer can be found nearly 8,000 kilometres away on the Svalbard archipelago.
38:48It's well within the Arctic Circle.
38:5360% of Svalbard is covered in glaciers.
39:00It's a landscape dominated by ice.
39:09But 55 million years ago, it was rather different.
39:13The clues are in the rocks, which are full of ancient leaves.
39:25These fossils originate from the time just after the methane surge in the oceans.
39:33They're from a distant relative of the beach, a broad-leafed deciduous tree.
39:40In other parts of the Arctic, whole trees are preserved in the permafrost.
39:53Following the methane surge in the ocean,
39:56global temperatures would have been 10 degrees warmer than they are today.
40:01It caused immense upheaval.
40:04Plants and animals were forced to migrate towards the poles.
40:09Back then, all of this would have been subtropical swamps and forests.
40:17Less high Arctic, more Florida Everglades.
40:26It would have been inhabited by ancestors of creatures like the hippopotamus and the crocodile.
40:35The lesson from the Earth's past is that the world we know today can change out of all recognition simply
40:42by raising the level of greenhouse gases in the atmosphere.
40:50The extraordinary warm period didn't last, though.
40:55The planet cooled and ice came to the Arctic.
40:58So what happened?
41:06What happened was the Himalayas.
41:14The creation of this mountain range helped return ice to the Arctic.
41:26When the tectonic plates of India and Eurasia collided around 50 million years ago,
41:32the result was a mountain range that grew to become the biggest on Earth.
41:49In building the Himalayas, the planet unleashed its most formidable global cooling weapon.
41:58Weathering.
42:04The process begins when carbon dioxide in the atmosphere is dissolved in rain and snow.
42:11This reacts with minerals in the rock to form a solution that's carried by rivers to the sea.
42:22Here, the carbon is absorbed by marine creatures.
42:25When these die, they sink to the sea floor, eventually becoming rock, locking the carbon away.
42:37Because the Himalayas were constantly rising, they were perpetually exposing new rock to the elements.
42:45This drew more carbon dioxide out of the atmosphere, cooling the planet,
42:52and eventually leading to the refreezing of the Arctic.
43:01So the planet had an entirely natural way of reducing greenhouse gases.
43:08But there's one obvious problem.
43:11It takes millions of years to build a mountain range.
43:16We don't have the luxury of that sort of time.
43:21The lesson from history is not entirely wasted, however.
43:28We are now developing ways to take carbon out of the atmosphere.
43:37One method is to stimulate the growth of immense blooms of algae that use photosynthesis to draw carbon dioxide from
43:46the atmosphere.
43:50On land, there are plans to create artificial trees that replicate photosynthesis.
43:58But the biggest challenge is to stop carbon dioxide reaching the atmosphere in the first place.
44:06This can be done by capturing its source, filtering it from industrial chimneys.
44:13Once it's been captured, it then has to be disposed of.
44:20And if you happen to have thousands of tonnes of carbon to get rid of,
44:24then geology can provide a solution.
44:33One disposal method is to drill shafts through impermeable rocks to reach large, deep-lying beds of sandstone.
44:43Carbon dioxide can then be pumped down into the sandstone.
44:47Here, it will be trapped in the pore space within the rock,
44:51whilst the layer of impermeable rock above will stop it from escaping.
45:03Carbon capture won't solve our greenhouse gas problem entirely,
45:08but it might at least buy us some time to develop cleaner forms of energy.
45:19Up until now, the effects of our impact on the planet,
45:23whether good or bad, have been accidental and unintended.
45:28Whether it's a mud volcano in Indonesia or altering the Earth's climate,
45:33we never set out to create these changes.
45:42Science has given us an understanding of how the planet works
45:45that allows us to protect ourselves against Earth's unpredictable nature.
45:52But today, we're on the brink of a new era.
45:57We can now take control of our impact on the planet's natural processes,
46:03and maintain the conditions for civilisation to flourish.
46:08It's a big challenge, which involves global cooperation.
46:18There's an example of just what can be achieved here on Svalbard.
46:26To protect its contents, this facility in Svalbard has been built high enough
46:32to be above any future rising sea level.
46:42It's been excavated so deep into the mountain that it would survive a nuclear explosion.
46:50This is apocalypse planning for our future survival.
46:58Plant scientist Morten Rasmussen is one of the few people in the world allowed access to this facility.
47:06It's the modern equivalent of a Noah's Ark.
47:09But instead of sheltering animals, it's preserving the future of the world's food supply.
47:16This place is the Svalbard Global Seed Vault.
47:19It's a global safety storage for gene banks for the entire planet.
47:25So in here, we have backup seeds of the entire diversity from our crop plants.
47:36There's not just one variety of each crop in here.
47:39There's thousands, each with different properties,
47:43used to different growing conditions and with resistance to different diseases.
47:52This place is preserving the diversity of crop plants.
47:57So it gives access to the genetic diversity of all the food crops we are producing in the agriculture globally.
48:03And this is what eventually secures the food production for our grandchildren.
48:11The seed vault has the potential to store every variation of every staple crop in the world.
48:20If any variety disappears from use, then there will still be seeds stored here, preserved in case they turn out
48:27to have properties that are useful in the future.
48:32This marks a crucial change in our approach to the planet.
48:37We're now taking conscious control over an uncertain world.
48:46It's a symbol of what can be achieved at a global level if we put our minds to it.
48:57In this series, we've seen how the fate of past civilizations has been shaped by the planet's natural forces.
49:06The Khmer's of Angkor Wat thrived on their ability to exploit the monsoon until their growing population outstripped their most
49:15precious resource.
49:17Water.
49:22The Anasazi of Chaco Canyon came to ruin when a change in the El Nino cycle led to a sudden,
49:29prolonged drought.
49:33The Minoans of Santorini flourished in blissful ignorance of the volcano beneath them that would one day destroy their civilization.
49:47Today, that relationship is changing.
49:52We're now a geological force that rivals the planet's natural forces.
50:01The ultimate test will be how well we use that power.
50:12As a species, we like to think we're special.
50:17This is our chance to prove it.
50:59Our infinite perception of evolving population is entirely on항.