Earth's history is marked by one cosmic disaster after another, forging the path of human evolution; now, experts explore how the Earth has teetered on the verge of destruction.
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Thanks for watching. Follow for more videos.
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LearningTranscript
00:01The Earth is over 4.5 billion years old.
00:06Its history is shaped by disaster after disaster.
00:14Asteroid and comet collisions, flares from the sun.
00:18Mass extinctions, supernova explosions, cosmic ray bombardment.
00:24You name it, we've experienced it.
00:26Kind of a miracle we're here at all.
00:30These violent events could be why Earth has life.
00:35We tend to think of disaster as a bad thing.
00:38But out of chaos can come possibility.
00:41When we destroy something, we can also create something new.
00:46Earth has walked the line between survival and destruction.
00:52It's tipping that fine balance of luck between a good disaster and a bad disaster.
00:57Could catastrophe and chaos be the essential ingredients for life?
01:03It's a long-hidden clue to our violent past.
01:18It's a long-hidden clue to our violent past.
01:22Scientists investigate something mysterious buried deep inside the Earth.
01:29It's a long-hidden clue to our violent past.
01:32Deep down, 1,800 miles below the surface of the Earth, our core is surrounded by fluid rock.
01:41But inside that, 600 miles high and thousands of miles across are two denser regions.
01:47And they kind of cup the core of our planet like two hands.
01:50One of them is, you know, half the size of Australia, for crying out loud.
01:55So, I mean, there are big lumps down there.
01:57There's no reason they should be there.
01:59It's a mystery to us.
02:02To solve this mystery, scientists need to examine the rocks buried over 1,000 miles beneath the surface.
02:10We don't really know what these two big rocks are made of sitting there on the core.
02:16However, we've been able to sample them.
02:18How in the world is that possible?
02:21Well, these blobs are actually feeding mantle plumes that are rising up through the mantle.
02:27So, volcanoes in Iceland and Samoa, for instance, will dredge up some of these lumps of rock from the mantle.
02:33It's a precious chance for us to sample some of that deep rock that we'd normally not get a chance to see.
02:41These rocks are old, very old.
02:45It turns out that the samples in the lava that we think came from these blobs of rock in the mantle are 4.5 billion years old.
02:53That is as old as the age of the Earth.
02:55So, they tell us something about, you know, how the internal structure of our planet was arranged in the earliest days of the formation of our planet.
03:05So, getting samples from that time is very, very important.
03:08The age of the rocks may be a clue to their origin.
03:13They date back to a time of monstrous cosmic mayhem.
03:16Four and a half billion years ago, the solar system was still a pretty wild place.
03:27We're approaching the end of the formation of planets.
03:30Earth would still be growing.
03:34Back then, you wouldn't necessarily recognize the Earth.
03:39In fact, you wouldn't recognize the Earth at all.
03:41For example, no moon.
03:42The Earth did not have a moon when it first formed.
03:46The young Earth orbits the sun with other infant planets.
03:52One of them is an object scientists call Thea.
03:57And it's on a collision course with our home.
04:07The Thea collision would have been a spectacular event.
04:10It would have been one of the coolest things you could possibly witness in the origin of the solar system.
04:14It's certainly the biggest event in the history of the Earth.
04:21The Thea event is something that completely reshaped the Earth.
04:26The planet that the Earth was before the Thea event is gone forever.
04:31The impact melts rock and throws out over a billion, billion tons of debris.
04:40During this incredible collision, these two planets were literally broken apart and combined into one big planet.
04:47Huge chunks of Thea stayed together as the now molten Earth began to form anew.
04:52Now we can kind of paint a picture of where these big lumps of rock might have come from.
04:57They're very old.
04:59They're in fact the same age as that large impact event.
05:03They could be pieces of Thea.
05:05The giant slabs of Thea sink down into our planet and lie undiscovered for billions of years.
05:22Earth reforms from the ruins of both planets.
05:26Now you might think that a collision like this is just devastating.
05:31There's no upside at all.
05:32But there are some things that came out of this collision that may have led to the possibility of life.
05:39When these two planets combine, parts of Thea's iron core merge with Earth's.
05:46So that means that Earth collected a much bigger core than it might have possessed on its own.
05:51This is good news for us because the core is the source of the magnetic field that protects us.
05:56Liquid metal flowing around in the outer core generates Earth's magnetic field.
06:03A protective shield from the sun.
06:08The sun can actually output billions of tons of high energy protons and electrons in a single burp.
06:16That eventually would have stripped away our atmosphere.
06:19If it weren't for that active core in that magnetic field, we would look like Mars.
06:23Just sort of a bare and barren desert.
06:25Thanks to Thea's extra iron, Earth's molten outer core is large.
06:32So it cools slowly, staying molten.
06:36And keeps on generating a strong magnetic shield.
06:42Because of that collision, the extra iron, the extra heat, we've stayed active.
06:47We have a magnetic field.
06:49We are protected.
06:50And in fact, that's why we're here talking about it.
06:52The catastrophic impact helped life in other ways.
06:58The Thea event was absolutely huge.
07:01Not an impact like a hundred mile asteroid making a big crater in the desert.
07:05But a planet hitting a planet.
07:08Causing a huge disk of debris spread out from the Earth, out of which formed the Moon.
07:14After the collision, the Earth tilts on its side and spins incredibly fast.
07:26A day only lasts a few hours.
07:29The Earth itself rotates slightly on its side.
07:35And if left to its own devices, would in fact experience unpredictable chaotic wobbling.
07:44The fact that the Moon is there stabilizes the Earth, stabilizes our climate.
07:50The Moon's gravitational pull on our oceans creates tides and slows down the Earth's spin.
08:00Creating a world primed for life.
08:03We actually owe quite a bit to the Moon and Thea, its progenitor, for making Earth a hospitable planet for life.
08:14A giant collision four and a half billion years ago sounds like a catastrophe, but it was probably the best thing to happen to the Earth.
08:23Thea, I would shake your hand because we have a lot to owe you.
08:27We also owe the science of chance, because we lucked out with a one-in-a-million impact.
08:37If the impact from Thea had been a little bit harder, the Earth may not have recovered as well as it did, and we may not be here to talk about it right now.
08:45If it had been a little bit less forceful, then the impact of it may not have made the changes that we think were needed for us to be here now.
08:53We got lucky.
08:54Most planets don't get to survive a collision like that and get a bonus moon out of the deal.
09:04Earth's huge collision with Thea was not our planet's first brush with danger.
09:11An earlier explosive event could have stopped the solar system from sparking into life.
09:18And the Earth from forming.
09:24Supernovas are one of the universe's most destructive events.
09:38Releasing in one second as much energy as our sun will in its entire lifetime.
09:46But rather than wipe us out, supernovas may have kick-started the solar system.
09:544.6 billion years ago, the solar system was not even really the solar system.
09:58It's the precursor of the solar system.
09:59So what we had was a cloud of gas and dust collapsing in on itself, forming the sun in the center, a big flat disk around it, out of which all the planets were forming.
10:12There are all kinds of vast clouds of dust and gas floating around the galaxy.
10:18What actually causes them to start collapsing and forming new stars?
10:23Well, you have to give that cloud a push.
10:25Scientists think this push could be a stellar blast.
10:32A supernova.
10:34Supernova are some of the most powerful events in the universe.
10:42One explosion can light up brighter than a galaxy.
10:47So not only do they eject elements and material, they also eject a lot of light and energy.
10:53A supernova explosion sends a shockwave racing out into space at 18,000 miles per second.
11:05The shockwave from a nearby supernova compresses material together until it begins to collapse under its own gravity.
11:15Was this how our solar system started?
11:17So far it's been really difficult to find evidence that there was some supernova or point to something that happened that really kick-started the solar system.
11:28The ancient supernova blast faded away a long time ago.
11:36Imagine a crime scene.
11:38Now imagine waiting 4.6 billion years after the crime is committed and looking at it and going, there's nothing here, what are we doing?
11:46That's kind of what we're trying to do here.
11:50Researchers from the University of Minnesota tried to solve this ancient crime by studying asteroids that fell to Earth as meteorites.
12:01Asteroids are critical for understanding the early solar system.
12:04And this is because they have frozen in place all the conditions that existed in that very early solar nebula right at 4.5 billion years ago.
12:13The asteroids contain information about the time leading up to the birth of the sun and the solar system.
12:23When a massive star ends its life as a supernova, it undergoes what we call nucleogenesis.
12:27In fact, we call it explosive nucleogenesis.
12:31Literally, the explosion is generating new types of nuclei, new elements, heavier elements.
12:37Well, it turns out the types of elements it makes depends on the star that blew up.
12:47The Minnesota team ran computer simulations to investigate which elements form when a star, up to 12 times the mass of the sun, explodes.
12:58Then, they compared the results with analysis of elements found in asteroids dating back to the birth of the solar system.
13:10They match.
13:11So, the remains of this supernova was actually under our noses all along in the elements that have been in our solar system for ages.
13:23And perhaps in the Earth as well.
13:26The Earth has lots of rocks that's made of silicon.
13:31That's only produced in supernova explosions.
13:34And the very core of our Earth, the thing that keeps us alive, that's iron, nickel.
13:39Again, you only get that in supernova explosions.
13:41In February, 2021, scientists shed light on the supernova explosions that helped seed our solar system and provide the materials to build our planet.
13:56The researchers examined fragments blasted off the giant space rock, Vesta, 4.5 billion years ago and later landed on Earth.
14:07These asteroid fragments contained the fingerprints of not one, but at least two supernova explosions.
14:19Our solar system was seeded, was enriched by at least two separate supernova explosions.
14:27That's incredibly lucky because that is what delivers the ingredients necessary for life.
14:32Scientists believe that these two supernovas may have enriched different parts of the infant solar system.
14:42One provided the materials that helped form the outer gas planets.
14:49The other supernova seeded the inner solar system with elements that built the rocky planets, including the Earth.
14:58Once again, our fate came down to pure chance.
15:05A series of extraordinarily violent supernova blasts gave the solar system the kickstart it needed and the elements to build the planets without destroying our future home.
15:18It's a fine line between being too close to a supernova, which will just shred your pre-stellar cloud.
15:24And not too far away that you don't get any of the good stuff.
15:28Supernovae play both creation stories and destruction stories.
15:35They play both roles.
15:37We lucked out.
15:39This chapter of the story ends well.
15:43The solar system gets the ingredients it needs to build planets.
15:47Earth forms in a good location, close to its star.
15:51Earth forms in a good place.
15:51Earth forms in a good location, close to its star.
15:53The future looks bright.
15:54But then, the biggest bombardment in history smashes into the Earth.
16:01From the moment our planet formed, we've been under fire.
16:222021, a fireball streaks across the night sky in Europe.
16:272018, a 1,500-ton meteor explodes over the Bering Sea, with ten times the energy of an atomic bomb.
16:392013, an asteroid explodes over Russia, injuring over a thousand people.
16:48The Earth is hit by quite a few asteroids every day. You see them as shooting stars, meteors in the sky.
16:56These events are violent and destructive, but these space invaders also brought something every living planet needs, volatiles.
17:08When we say volatiles, what we mean are elements that are really light and easily moved around, often they're gases.
17:14So that's oxygen and water and carbon dioxide and just all those light elements that are really important building blocks for life.
17:22These elements are abundant on our planet today, but were not when it first formed.
17:29From observing other solar systems forming all around us in space, we know that planets as close to their stars as we are to the sun, when they form, they're very hot and dry.
17:38There's probably some little bit of water around there, but really not very much.
17:43So what this means is any volatiles will basically be boiled away.
17:48If you have a molten surface, anything like water is going to get boiled away.
17:53Young Earth was a dry planet, devoid of all the precious volatiles needed for life.
18:03These materials must have been delivered to Earth after its formation.
18:08We think volatiles arrived in the early days of the solar system, when the giant planets, including Jupiter, moved around and stirred up the contents of the solar system.
18:27As Jupiter moves, its gravity is pulling on all the objects in there, basically speeding them up.
18:32There's a little bit of chaos there in the first place, but now Jupiter is basically supercharging it.
18:37Jupiter's path sends countless asteroids and comets on a collision course with the Earth.
18:45It would have been utterly chaotic.
18:47This is a rain of large objects onto all of the inner planets, but these objects that came screaming into Earth were gigantic.
18:58Four billion years ago, a storm of giant asteroids and comets hits the Earth.
19:04Some are tens of miles wide.
19:08They bring the volatiles that help fill the Earth's oceans and fill its atmosphere.
19:14But cosmic deliveries can both give and take.
19:18The importance of impacts for atmosphere could go either way.
19:24You could have a really big, really powerful impact that blows away the atmosphere of a small fledgling planet.
19:32Or you could have a bunch of small impacts of water-rich asteroids that are simply contributing water and volatiles and new chemicals to the surface that might help the atmosphere that's already there.
19:43When you think about an object coming to Earth, is it going to land on Earth?
19:48And if it does land, is it going to be an erosive event where material is lost from the Earth?
19:56Or is it going to be an accretion event where the Earth gains material?
20:00Well, the devil's in the details.
20:04Details like the size of the impactor.
20:08One study suggests that asteroids between 60 feet and 3,300 feet wide add more to the atmosphere than they take away.
20:17And speed at the point of impact also matters.
20:30Asteroids are orbiting the Sun.
20:32And when they fall towards the Sun, they are gaining speed.
20:35They're gaining velocity.
20:37Imagine dropping a coin into one of those spiral wells.
20:40As the coin gets closer and closer to the middle, it spins up faster and faster.
20:48The closer an asteroid gets to the Sun, the stronger the Sun's gravitational pull.
20:54And the faster the asteroid travels.
21:00So proximity to your star is a vital factor in how intense any impacts will be.
21:04It's possible that the Earth is the right distance from its host star.
21:18So that when an impact happens, the energy isn't insanely high.
21:23It's just the right amount that is the right speed to make everything work.
21:28Supernovas seed the solar system with the elements to build the planets.
21:32Asteroids and comets deliver volatile chemicals to the surface of the Earth.
21:40Together, they create a habitable environment.
21:44So we need those impacts to happen to have life on Earth.
21:49Disasters created a planet primed for life.
21:53But it appears that even more mayhem and chaos are needed to trigger life itself.
22:02An asteroid tears through the solar system, hurtling through space at 40,000 miles an hour.
22:17Its destination? Earth.
22:18Will this space rock inflict unimaginable damage?
22:28Or will it bring the spark of life?
22:30The spark of life.
22:31This idea of a spark of life, we've all kind of seen it in the Frankenstein movies, right?
22:39It's alive!
22:41This comes from legend, from myth, from history, that there's some sort of a spark that differentiates cold, inanimate matter from living stuff.
22:50And in some sense, it's kind of true.
22:56On Earth, we think this spark may have arrived over 4 billion years ago.
23:02The Hadean Eon was the time from the Earth's formation about 4.6 billion years ago to about 4 billion years ago.
23:11It's named after literally Hades, so the conditions on Earth were literally hellish.
23:21It was hot and soupy, a lot of water vapor around, high pressure atmosphere, very intense heat.
23:27You wouldn't survive. The planet would literally kill you back then.
23:31It's shocking, and I mean really shocking, that the evidence of first life that we have on Earth dates to the Hadean Eon.
23:43This was a terrible place, molten and poisonous and awful, and yet life somehow arose in all of that mess.
23:52June 2020. Japanese scientists simulate the conditions of this hellish planet, and then try to recreate the spark of life.
24:07So what the scientists were trying to do was mimic those conditions and see what would happen if you smash a meteorite into the ocean back then.
24:15Could it produce sort of the same chemicals that we see life using today?
24:18They use a mix of carbon dioxide, nitrogen, water, and iron to replicate the Hadean environment.
24:30Firing a mini meteor at 2,000 miles an hour into this chemical soup triggers a reaction between the basic organic elements,
24:40creating amino acids.
24:44We call amino acids the building blocks of life.
24:48Really, they're the building blocks of proteins, and life needs proteins to exist.
24:53But that's why they're so important.
24:55Without amino acids, there's no proteins. Without proteins, no life as we know it.
25:01The experiment proves that meteorite impacts can help build the components for life.
25:06But for these building blocks to come together and create life, we need more.
25:16It's like making a cake. You can put together the oil and the flour and the butter and the sugar, but if you don't put it in an oven, you're not going to end up with a cake.
25:25You're going to end up with something else.
25:26We thought that the violence of asteroid impacts prevented life from forming.
25:35Now, we think they could be an essential ingredient.
25:39If the asteroid impact is big enough and fast enough, it can punch right through the crust.
25:46Then you're getting geothermal heat, heat that bubbles up from the mantle.
25:52And it is certainly possible to get an asteroid impact that big.
25:56Large meteorite impacts can create hydrothermal vents, which some scientists believe were the cradles of life.
26:06They provide warm, wet environments and bring up chemicals from deep inside the Earth's crust.
26:15The perfect place for life to begin.
26:18As bad as those conditions seem to us, to the molecules that are beginning to combine and do their thing, that was a wonderful place to be.
26:31It could actually be that the conditions that are best for early life might actually be those just after an impact.
26:38So you have sort of this petri dish environment in which life could really thrive.
26:43These vents might be similar to those we see in the oceans today.
26:52These hydrothermal vents provide a little window into what conditions on the primordial Earth would have been like.
27:01And the sort of chemistry that goes on in those hydrothermal fluids seems to be the right kind of chemistry for creating life.
27:10Once again, Earth got lucky.
27:16Impacts that could have destroyed everything may have helped spark life into existence.
27:27I once heard this quote from Confucius that creation is quiet, but destruction is loud.
27:34Well, these impacts were both destructive, but they also may have been creators.
27:44Earth leaves behind the Hadean age.
27:48The planet calms and life takes hold.
27:52But disaster is our constant companion as we prepare to face a storm of deadly cosmic bullets.
28:00The universe is a dangerous place for life.
28:16There are asteroid impacts.
28:19Black holes.
28:23Black holes.
28:26And exploding stars.
28:30But public enemy number one.
28:32Cosmic rays.
28:36Lethal, energetic particles born in violent events.
28:40Cosmic rays are incredibly small, but travel so fast near the speed of light that they can tear through our DNA and damage it.
28:50You're full of DNA.
28:52If that DNA gets broken apart, guess what happens?
28:55That could lead to cancer and death.
28:58At first glance, these cosmic rays are the worst things for life.
29:02They're terrible.
29:04Despite their frightening rap sheet, cosmic rays may have played a crucial role in the evolution of life.
29:102020.
29:12Scientists at New York and Stanford Universities investigate biological molecules that have a twin.
29:23Mirror image versions called chiral molecules.
29:28The concept of chirality in chemistry is when you have two molecules, two chemicals, that are physically the same.
29:36They're made of exactly the same things, but their structure is different.
29:40And they're not just different.
29:41They're reflections of each other.
29:43It's literally called handedness.
29:45Because look, here's my right hand with my thumb over here and my fingers over here.
29:49Here's my left hand with my thumb over here and my fingers over here.
29:51I can't wear a left glove on my right hand.
29:54There's nothing I can do to make these guys the same.
29:58And it turns out this is true not just for hands, but also for a large number of simple organic compounds.
30:06Things like amino acids or sugars, which are the building blocks of all life on Earth.
30:12Billions of years ago, early life may have had both left and right handed DNA and RNA.
30:22But life chose to use mostly right handed molecules.
30:27The reason may have been cosmic rays.
30:35When cosmic rays hit Earth's atmosphere,
30:37they degrade into even smaller subatomic particles called muons.
30:44Most muons spin in one direction.
30:49So we have these little muons, which are very energetic and they're spinning a certain way.
30:54And when they hit a molecule, they interact with it.
30:57They can disrupt it. They can change it.
31:00Some scientists believe these spinning muons interact more readily with right handed DNA.
31:07And RNA.
31:10Triggering mutations.
31:13Some mutations are beneficial, but they have to get a chance.
31:17So if you have right handed molecules and left handed molecules and they're both being hit by muons,
31:22the one that's hit more gets more chances to have a beneficial mutation.
31:27Cosmic rays may have given right handed life an evolutionary advantage.
31:32Left handed life could not compete.
31:37It's like throwing dice.
31:40If you're trying to get double sixes and the left hand only gets to throw ten times,
31:44and the right hand gets to throw a hundred times,
31:47more likely to get double sixes with the right hand than the left hand.
31:50But the dice don't always land in our favor.
31:56359 million years ago, Earth's luck ran out.
32:01And cosmic rays may have lived up to their reputation as the baddest particle on the block.
32:07Earth's oceans were teeming with marine life.
32:16And by this period as well, plants had started to colonize onto the continents and land masses,
32:23attracting animal life, insects, millipedes.
32:26And it's in this environment that Earth experienced one of the greatest mass extinctions in the history of life.
32:39Something killed off 97% of all vertebrate species.
32:44We call this wipeout the end Devonian extinction.
32:54One possible explanation? A supernova.
32:59When some dying stars explode, they fire out cosmic rays.
33:03This radiation bombards the upper atmosphere of the Earth and drives the chemistry of nitrogen turning into nitrogen dioxide.
33:16A gas which itself then reacts with the ozone layer and destroys it.
33:21Without the protective ozone layer, ultraviolet radiation from the sun bombards Earth.
33:27Radiation rains down for thousands of years, damaging the DNA of plants and animals.
33:37Many species die out.
33:43The end Devonian mass extinction mostly affected marine life.
33:50This is where we see the greatest percentage of deaths.
33:54The oceans, once populated by fish the size of school buses,
34:01now host fish no bigger than a sardine.
34:05These smaller fish reproduce quickly.
34:10In the challenging environment, they adapt and diversify faster than larger species.
34:17Mass extinctions not only wipe the slate clean,
34:20and provide other animals and other life forms an opportunity.
34:25It creates the sort of chaotic and complex environment that drives natural selection and evolution.
34:35If a supernova was to blame for this extinction event,
34:39scientists believe that the culprit was 65 light years away.
34:43Any closer and Earth's luck would have run out completely.
34:51It seems the existence of life is always balanced on a knife edge.
34:55One exploding star goes off a little bit too close to us.
35:00And we are all destroyed.
35:02So there's this wonderful balance between just violent enough and too violent.
35:11And we have been lucky enough to dance on that edge for four and a half billion years.
35:15This mass extinction reset life on Earth and paved the way for four-legged creatures, our distant ancestors.
35:29Cataclysmic events go hand in hand with human evolution.
35:34Some knocked us back and others, like the event 66 million years ago, gave us a push forward.
35:4266 million years ago, a massive asteroid crashes into the Earth.
35:58It triggers a huge extinction event.
36:02Without it, humans may have never evolved.
36:06At this time in Earth's history, we had these enormous plants and gigantic insects.
36:11That actually would be incredibly terrifying if we saw them today.
36:17Pterosaurs sail through the air.
36:20Huge marine reptiles dominate the oceans.
36:23And the T-Rex is the king of the world.
36:30Then, a glowing object appears in the sky.
36:33I'm sitting on the beach, what was then going to be the Yucatan of Mexico, enjoying a drink with an umbrella.
36:46But up there in the sky, all of a sudden, approaching me at 40,000 miles an hour is Mount Everest, glowing thousands of times more intensely than the sun.
37:00And it's just seconds away from dropping on my head.
37:03A six-mile-wide asteroid slams into the Earth.
37:10The impact throws trillions of tons of rock and dust into the air.
37:20The rocks heat up as they fall back to Earth, setting the planet on fire.
37:33That beach holiday suddenly turns into absolute nightmare.
37:38The impact also throws up soot, choking the atmosphere.
37:44Now the skies are blotted out by all these materials, so the sun is no longer shining brightly on the surface.
37:52Plants need sunlight to photosynthesize.
37:57Without this vital energy source, many species die out.
38:02With their food source gone, plant-eating dinosaurs starve to death.
38:10Followed by their predators.
38:13It was a huge disruption to all of life on Earth.
38:17The dinosaurs have been around for 160 million years at this point.
38:21That's no small amount of time.
38:23And in one event, they're gone.
38:25Again, the dice roll is in our favor.
38:28Most dinosaurs become extinct, paving the way for the evolution of mammals.
38:35Leading, eventually, to humans.
38:39Without the asteroid impact, we wouldn't be here.
38:44As a furry primate on this planet, I kind of like the KPG impact, right?
38:48I'm here because of it.
38:50We all are.
38:52Some plants benefited from the asteroid strike.
38:55To learn how plants changed after the impact, Smithsonian scientists examined thousands of tropical plant fossils from the time of the die-off.
39:07This disaster opened the way for new types of plants to develop.
39:13It transformed the plant kingdom, producing a richer and more diverse global ecosystem.
39:22Before the asteroid strike, conifers and ferns dominated the tropical forests of South America.
39:29But afterwards, falling ash from the impact enriched the soil, and fast-growing flowering plants took over.
39:39The impact was very hard to recover from, but it actually opened the opportunity for a greater diversity of plant life, which ultimately has benefited us as humans, because it has allowed us to have more food sources.
39:52This new world order eventually gave rise to the modern Amazon rainforest, home to 10% of all species on Earth.
40:06It really destroyed and remade our entire environment.
40:12The world grew back, of course it did, here we are, but it changed everything.
40:17And another age, maybe, just around the corner.
40:21We should absolutely expect that at some point in the future, and I'm not saying you should lose sleep over it, but at some point there will be another mass extinction.
40:37Maybe that will be the end of our days.
40:40The intriguing question is, what might come after humans on planet Earth?
40:46Catastrophe may be the universe's recipe for life throughout the cosmos, one that every planet must follow.
40:58Looking at our own history, life thrives on catastrophes.
41:03We need these disasters for evolution to work.
41:06So hopefully, and I hate saying this, I know how it sounds,
41:10hopefully these other planets have had terrible disasters as well.
41:13Think about the word disaster.
41:17It means bad star.
41:18It means that something has gone wrong, something that's dangerous.
41:22We are children of disasters.
41:26There's no way you get us without planets colliding.
41:31Without asteroids and comets streaming through the atmosphere.
41:38Without even stars exploding in supernovas.
41:40You are a child of that violence.
41:46That's part of the environment that we grew up in, in a cosmic way.
41:50And I think that is tremendously beautiful.
41:52Between
42:17Yes, happily.