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00:00Our galaxy, a billion years from now, a planet shrouded in turbulent, dense clouds, buried
00:20deep below an alien landscape, the surface scorched, the temperature sky high, the pressure
00:36unbearable.
00:39This is not a distant extraterrestrial world.
00:44This is Earth.
00:48This is our future.
00:50We know it to be true because Earth has a twin, Venus.
00:57And Venus has already descended into hell.
01:16The solar system.
01:20Eight planets orbit a central star, the sun.
01:26Among them, Earth and its neighbor, Venus.
01:30Earth is an oasis for life.
01:35Venus, the stuff of nightmares.
01:43Venus and Earth couldn't be more different.
01:46Earth is this beautiful planet and there's water everywhere.
01:49It's ice at the poles, it's water in the ocean, it's in the atmosphere, it's water vapor.
01:55But then you look at Venus, it is the worst place imaginable.
01:59It is so hot on the surface, crushing pressures.
02:02It couldn't be any less supportive of life.
02:08To me, the planet Venus is sort of a classic definition of the word hell.
02:14If you were to transport to Venus and experience the environment there, you'd quickly want
02:20to return back to Earth.
02:23The conditions on Venus are amongst the most inhospitable in the solar system.
02:28It's just a horrible place, it's so hot and there's no water and the atmosphere is so
02:32thick.
02:33And it rains sulfuric acid.
02:37It's going to be a competition between whether or not you're going to be cooked to death
02:40or crushed to death.
02:49Earth and Venus may seem like very different worlds, but they shouldn't be.
02:59They're roughly the same size, the same mass and made from the same ingredients.
03:05At first, they were twins.
03:08Early Venus and early Earth were very similar.
03:11They're twins, probably nearly identical twins at their earliest stages.
03:17Given that Venus is so Earth-like in so many ways, it's really odd that it is so different
03:22than the Earth.
03:23And this makes it one of the biggest mysteries in the solar system.
03:28Somewhere in their two histories, the Earth and Venus took two very different paths.
03:36The results, two totally different worlds.
03:40Their paths were so different, you could hardly believe that one would be related to the other.
03:44But now the opposite thing's going to happen.
03:46We're going to catch up with our twin.
03:48We're going to evolve to be a lot more like Venus in the future.
03:54In the future, the two planets' paths will converge and they will become twins once more.
04:02Like Venus, Earth will descend into hell.
04:08The oceans will vaporize.
04:11The land will melt.
04:13Our hospitable blue planet will vanish, replaced by a fiery, molten world.
04:21We are actually on the Earth at a time when there's water and rain and it was so easy
04:25for life to take hold.
04:26But that's going to change.
04:28Take a look in at Venus and have a look at our future.
04:34Earth will even surpass the horrors of Venus.
04:38A billion years from now, Earth could be an unimaginably terrible place.
04:47But how will this happen?
04:49And can we stop it?
04:55The roots of our home world's destruction are buried deep in the past of our twin planet.
05:03It's very much true that in studying the past of Venus, we are also studying the distant
05:08future of Earth.
05:11Both planets shared a violent birth, scarred by brutal planet formation, giant cosmic impacts
05:20and rampant volcanism.
05:23We're trying to reconstruct things that happened in the ancient, ancient past.
05:26It's almost like forensic planetary geology.
05:304.6 billion years ago, hundreds of infant planets began to form around the new sun.
05:44Among them, the baby Venus and Earth.
05:48As they hurtled around the sun, collisions were inevitable.
05:56Planet formation is like a demolition derby.
05:59In a derby, the cars are racing around a track, going around in circles at different speeds.
06:03Well, it's the same thing with planets.
06:06The material is orbiting the sun.
06:07It's going around and they're all going at different speeds, at different angles, different
06:10trajectories, and sometimes, boom!
06:18In the chaos, planets collide.
06:26The scale of the impact is unimaginable, as two planets become one.
06:33You have these large bodies that are hitting each other at really high velocity.
06:42It's really a very hot, violent mess.
06:48The amount of energy released in these impacts is huge.
06:51It completely dwarfs all of the nuclear weapons on Earth combined.
06:56And yet, somehow, on these scales, you wind up forming gigantic objects that we call planets.
07:06Earth and Venus became voracious planet-eaters.
07:12But two spectacular collisions set the twins on very different paths.
07:19That was the moment Venus and Earth went through this divergence to what has now become these
07:24really dramatically different worlds.
07:29The divergence began when a Mars-sized object hit Earth.
07:40The impact made our planet spin faster.
07:47The spinning core generated a powerful magnetic field around the Earth.
07:55The field fended off the worst of the sun's radiation and would go on to protect life
08:00on Earth.
08:05At around the same time, Venus took a head-on hit from another infant planet.
08:11But this impact had an unusual side effect.
08:18Venus is actually rotating in the wrong direction.
08:21How could that be?
08:22Well, what if it got hit really hard by some object?
08:26That could do it.
08:29An object so huge that it didn't only stop Venus in its tracks, it actually made the
08:35planet spin backwards.
08:37If you think about how much energy and what size you need to change a planet's spin, that
08:44is an incredibly large hit.
08:50But the backspin was slow.
08:52243 times slower than Earth's.
09:00Without a fast spin, Venus' core couldn't generate a strong magnetic field.
09:06It had no protection from the deadly stream of particles blasted from the sun.
09:13Venus does not have a strong magnetic field, and so it has suffered the full brunt of this
09:19wind blasted out from the sun.
09:25This is where the story of the two planets split radically.
09:32Venus was destined to roast under a violent, suffocating atmosphere, while the Earth would
09:38give birth to oceans, life and intelligence.
09:44But ultimately, these twins' fates will be the same.
09:48Venus' present is Earth's future, pure hell.
10:07Venus is a vision of hell, and one day will meet our twins' fate.
10:14It turns out that what Venus went through in its distant past is what Earth is going
10:20to go through in its distant future.
10:25The clues to the fate of our blue planet are locked inside the superheated wastelands of
10:30Venus.
10:34Something happened to Venus long in its past to make it a completely different planet with
10:39a completely different personality than the Earth as we know it today.
10:49The first probe was sent to our sister planet in 1967.
10:54We've been sending them ever since.
10:58What they found was incredible.
11:03Rocks that looked like granite.
11:09What makes that interesting is that to make granite, you need water.
11:15That means that there must have been abundant water for it to have formed in the first place.
11:27Venus once harboured oceans.
11:35Dr Lewis Dartnell thinks you can get a glimpse of what it was like here, in Iceland.
11:43It's the possibility that maybe in the early solar system, there were not one but two planets
11:50with oceans, two water worlds, Earth and Venus.
11:55And if Venus did once have oceans, maybe they would have looked a lot like this here, with
12:01a raw volcanic landscape descending down into the ocean with waves lapping against the coastline
12:09and maybe an overcast, misty, hazy atmosphere, not unlike what we're seeing here today.
12:18If there were oceans, there might even have been life.
12:24If Venus did have an early ocean, maybe something a bit like this, around four billion years
12:29ago when life was getting started on Earth, then maybe life got started on Venus as well.
12:35Maybe some kind of microbial life got started in the Venusian oceans.
12:41Just like Earth, Venus could have been a habitable, wet planet.
12:48But Venus couldn't hold on to its water.
12:54All of that water is gone.
12:56It's just gone.
12:58Where did it go?
12:59Something happened, either catastrophically or over time, to basically dry out this twin
13:05of the Earth.
13:08The culprit was the sun.
13:12Since its birth, it's grown stronger.
13:15Our sun, when we look out at it during the day, seems the same today as it was yesterday.
13:19But that's on a human timescale.
13:21On cosmic timescale, the sun has been getting hotter and hotter.
13:26Every billion years, the sun gets 10% hotter, slowly turning up the temperature on Venus.
13:37Not only that, Venus formed 42 million kilometers nearer the sun than the Earth.
13:44As it turns out, that distance to the sun was critical.
13:49It's just an unfortunate circumstance of being in the wrong place at the wrong time.
13:56Earth is far enough from the sun to hold on to its water.
14:02But Venus is slightly too close.
14:05The intensity of the sunlight got sort of just a little bit too much.
14:09It passed this threshold where Venus couldn't hold its water on the surface anymore.
14:17As temperatures rose, the oceans started to evaporate.
14:22All of that water in the oceans, all of those millions of cubic miles of water would become
14:27water vapor, basically steam clouds covering the entire planet, hiding the surface from
14:32the outside.
14:35Water vapor traps the sun's heat.
14:39As the clouds start to engulf Venus, the temperature rises, which in turn causes more water to
14:45evaporate and more clouds to form, which raises the temperature even higher.
14:55But the process can't go on forever, because the clouds of water vapor in the atmosphere
15:01start to disappear, ripped away by the solar wind.
15:06Venus does not have a strong magnetic field.
15:09And so the full brunt of the solar wind has been slamming into Venus for billions of years.
15:14Over time, if a water molecule was in the upper part of Venus's atmosphere, light from
15:18the sun could break it apart into oxygen and hydrogen.
15:22And then the solar wind could blow that stuff away.
15:27Over billions of years, this torrent of subatomic particles blasted out from the sun has stripped
15:32the water out of the atmosphere of Venus and has desiccated it.
15:41Venus Express was the most recent mission to the planet.
15:46Surfing the atmosphere, it found hydrogen and oxygen streaming from the top, confirming
15:51that water was leaking into space.
15:58We see sort of a tale of these atoms being stripped off and blown away from the planet
16:04itself.
16:05And really the only way that could happen is if there was a little bit of water left
16:09that is still being destroyed, picked up and swept away.
16:15Wisps of water are all that remain of Venus's oceans.
16:24It's a terrifying vision of our own future.
16:29So if Venus were in the past a lot more Earth-like, then that tells us that having a habitable
16:39world is something that is actually very precious and maybe is transient.
16:43It's not something that lasts forever.
16:49By losing the clouds that trap the heat, you might think that Venus's temperature would
16:53have simmered down.
16:57But in fact it was about to rise to astonishing new heights.
17:03It would become so hot that metal snow would fall on its mountains.
17:11Clues to how this happened can be found on Earth.
17:16In Hawaii, planetary geologist Janie Radeva studies the island's volcanoes.
17:27These volcanoes are a perfect model for early Venus.
17:31What we're seeing out here are lava flows that come all the way down from the Pu'u
17:40O'o event, which is about 15 miles away.
17:45Oh, there's hot.
17:46You can see that hot stuff.
17:47You can see hot.
17:48Quick, quick, quick, quick.
17:49Right there.
17:50It's really beautiful.
17:54Hawaii's volcanic lava fields look like Venus in miniature.
18:03Both produce the same kind of runny lava, building flat, shield-like volcanoes.
18:10The big difference is there are only five active volcanoes on Hawaii, whereas Venus
18:20is covered in them.
18:24One thing that really jumps out all around the planet is the number and variety of volcanoes.
18:29I mean, Venus could almost be nicknamed Volcano World.
18:32Venus has tens of thousands of volcanoes all over the planet.
18:43It's not the erupting lava that turns up the heat.
18:46It's what comes out with it.
18:48If we think back to the histories of Venus, I think we must have seen a landscape very
18:53similar to this one.
18:54You have massive amounts of lava flowing out of the surface, dumping huge amounts of gases
18:59into the atmosphere, carbon dioxide, tons of gas into the atmosphere every single day.
19:04It would have been amazing to see.
19:14On the surface, the source of the gases is revealed.
19:19If we look behind us, we can see volcanic gases gushing out of steam vents.
19:25We've got carbon dioxide being delivered to the atmosphere.
19:28It's exactly like what has happened on Venus.
19:33Carbon dioxide has been delivered out of volcanoes over and over and over again throughout its
19:37history so that now we have just a tremendously thick, dense atmosphere.
19:46The net result of all of these volcanic gases pouring out of volcanoes, major greenhouse
19:51gases, is that they've been absorbing heat for the billions of years of the history of
19:56Venus.
19:57This heat has been gradually creeping up until today, the surface of Venus is 900 degrees.
20:02It's like if you go into your kitchen and set your oven to broil, wait a couple of minutes
20:09and stick your head in it, and even that's not quite hot enough.
20:14It's a crazy, horrible, hellish spot.
20:23It's hard to imagine such extreme temperatures.
20:28But probes orbiting the planet reveal just how incredibly hot it is.
20:36Scientists studying the images notice something strange on the planet's mountains.
20:42It looks like on the mountains that there's apparently snow-like structures.
20:48But this is not like any snow found on Earth.
20:53So if you look at the White Peak Mountains of Venus, you would think that it was snow,
20:59but it's actually metals that have rained down and deposited on the top of those mountains.
21:07Metals like bismuth and lead melt.
21:11Then they evaporate into the atmosphere.
21:15As they rise, they cool, until they finally fall like snow on the mountaintops.
21:26I'm not sure even the imagination of science fiction authors would have come up with something
21:30as weird as Venus.
21:31I mean, just think about that.
21:32You have possibly metal frost on the top of mountains.
21:35I mean, how weird is that?
21:38It's pretty insane.
21:39Raining metals.
21:40Where would you ever think about that existing on Venus?
21:48In the future, metallic snow is forecast for Earth, too.
21:52And our scorching mountain caps will glitter like Venus's.
21:57But that's not all.
22:00Venus tells us that things will get even worse.
22:05Our atmosphere will grow heavy enough to crush cars.
22:24Earth and Venus were born twins, but they took different paths.
22:31Earth slowly evolved into a habitable world.
22:37Venus was covered in thick volcanic gases, trapping the sun's heat.
22:43Temperatures rose to over 450 degrees Celsius.
22:50But Venus wasn't just blighted by high temperatures.
22:57The volcanoes kept spewing gas up into the atmosphere, forming a 250 kilometer deep cloud
23:04of carbon dioxide around the planet.
23:08We don't think about gases as weighing anything, but they actually do.
23:13Trillions and trillions of tons of gas pressed downwards.
23:18There is simply so much air on Venus that on the surface it's pushing down with a huge
23:23amount of force.
23:25Atmospheric pressure on Venus is a monster.
23:27Think about it this way.
23:28All right, car.
23:29It's time for you to be crushed, baby.
23:30If you're on Venus, you're going to have 155 miles of atmosphere above your head.
23:46As a result, atmospheric pressure is 90 times that on Earth.
23:50So on Earth, it's about 14.6 pounds per square inch.
23:56On Venus, we're talking about 1,300 pounds per square inch.
24:00So if you're driving your car in Venus, this is what might happen.
24:10The crusher delivers the same force as the weight of Venus's atmosphere.
24:15This is pretty serious stuff.
24:24And this is why it's so hard on Venus.
24:26You get down to the surface, you have the crushing atmosphere to deal with.
24:30A spaceship tasked with landing on Venus must first survive the violent weather on
24:45the way down.
24:47The extreme heat powers a vortex the size of Europe over the South Pole.
24:53As the Earth heats up, we see storms that are more violent.
24:56You can only imagine the level of storms on Venus.
25:00The upper atmosphere of Venus is whipping around hundreds of miles per hour.
25:06Wind speeds reach 400 kilometers per hour.
25:10That's faster than most hurricanes on Earth.
25:13It must be a weatherman's paradise, in a sense.
25:17There are also huge lightning strikes.
25:22But these bolts are not formed in water clouds like on Earth.
25:26They form in something much more toxic.
25:31Venus's volcanoes release sulfur dioxide gas, which mixes with water vapor, creating sulfuric
25:40acid.
25:41You have clouds that are raining sulfuric acid.
25:43It rains sulfuric acid.
25:46Sulfuric acid in your lungs, your eyes, your mouth, your nose, that would be deeply uncomfortable.
25:55The extreme pressure and heat make Venus nearly impossible to explore.
26:03Only one nation has ever succeeded in getting a probe to the planet's surface.
26:08Truly one of the engineering triumphs of the human race was the Soviet Union's Venera
26:12program.
26:13The Russians sent over a dozen probes to the planet Venus, and only a few of them were
26:18able to survive long enough to even be able to take pictures from the surface.
26:24The Venera missions were incredible.
26:26It's such a hostile environment on the surface for electronics.
26:30And they were able to land on the surface and survive.
26:34The probe that sent back these images was crushed and burnt out in 90 minutes.
26:40Someday in the future, there are going to be interplanetary tour guides taking people
26:45to every planet in the solar system.
26:47You can imagine going to Saturn and seeing the rings, and Jupiter and its panoply of
26:51moons.
26:52There are all these great tourist attractions in the solar system.
26:55At the very bottom of that list is Venus.
26:59That is the last place in the solar system I would ever want to visit.
27:06The sun's heat and volcanic gases have transformed Venus into a vision of hell.
27:15The most lethal rocky planet in our solar system.
27:22Suppose you decided that you were going to put me in a starship transporter beam and
27:26transport me to the surface of Venus.
27:29What would happen?
27:30Well, the pressures there are incredibly intense.
27:33And the rain there, as I say, is acidic.
27:35The atmosphere is acidic.
27:37So I would be unaffected.
27:39But the average man would be crushed and melted.
27:42If you could imagine standing on Venus, it would be a torture in the extreme.
27:48Your feet would be burning from the molten fire below you.
27:52And your head would be hurting from the incredible pressure pushing you down.
27:57You probably wouldn't survive long enough to even notice it, actually.
28:02So why hasn't Earth followed the same path?
28:09Our volcanoes also spew out carbon dioxide.
28:13And we orbit around the same sun.
28:17But we are not being crushed and broiled.
28:22One reason is, Earth fawned farther away from the sun.
28:27And stayed cool enough to hold on to its oceans.
28:31Oceans do a lot of things for us on Earth.
28:34Because not only, obviously, are we water creatures and we depend on the water cycle
28:38for our existence in so many ways, but people don't realize the oceans also help to regulate
28:43the climate of Earth.
28:49Our oceans are full of tiny creatures that eat carbon dioxide.
28:59Richard Zebe, from the University of Hawaii, is diving on the island's coral reefs.
29:07He's studying how tiny marine organisms turn carbon dioxide into rock.
29:23What you see here is this white stuff.
29:25This is what we call calcium carbonate.
29:28And on top of this, what you see, these brown layers, this is essentially the living organism.
29:32This is the coral itself.
29:35It takes calcium out of the seawater and takes carbonate out of the seawater, combines
29:39them and makes this piece of calcium carbonate.
29:47There's over 70 million billion tons of carbon, locked up in carbonate rocks.
29:56This helps regulate carbon dioxide levels in the atmosphere, keeping temperatures from
30:01rising.
30:03If all the carbon that is being locked up in carbonate rocks and these corals would
30:08be put into the atmosphere as CO2, that would be certainly bad news for us.
30:17Currently our carbon cycle helps stabilize our climate.
30:22But in the future, this won't be able to save us.
30:30Forces far greater than the ones at work on Earth will overpower our natural defenses.
30:38Like Venus, our oceans will burn off.
30:43Temperatures will rocket as our life-giving sun starts to kill the Earth.
30:53Right now we live just the right distance from the sun, where it's just the right temperature
30:59for water to exist as a liquid.
31:03But that's going to change, just as it did for Venus.
31:09Venus started off probably in the habitable zone and then the inner limit to the habitable
31:13zone crossed the distance of Venus's orbit.
31:17Well it's going to cross the distance of Earth's orbit too.
31:20There is an expiration date to the Earth, and that's due to the sun's evolution.
31:28Ever since its birth, the sun has been getting hotter.
31:32That increased heat devastated Venus, and in the future, it will destroy Earth.
31:41In 1.1 billion years, the sun will be 10% hotter than it is today.
31:49The oceans will start to evaporate into thick clouds, which will trap more of the sun's
31:56heat.
31:56Catastrophically, very rapidly on a geological time scale, the oceans will put so much water
32:02vapor into the atmosphere that we will get a runaway greenhouse effect.
32:08The clouds forming in the atmosphere will trap more and more heat, driving temperatures
32:13even higher.
32:21Spiraling temperatures will cause even more evaporation, so the clouds will get thicker.
32:29Which led to more heating, which led to more evaporation, and you can see where this is
32:32going. It's a vicious cycle, it's a positive feedback.
32:37All of the ocean's water will boil away, millions of cubic miles of it.
32:42We have all of this water that will go into the atmosphere, covering the Earth and shrouding
32:47it in basically steam.
32:55Earth has had oceans for billions of years, but will take just 10,000 years to lose them.
33:04All of the water in the Earth's oceans will be in the atmosphere, we'll have an incredibly
33:07dense cloud-covered system where the temperatures on Earth will be approaching 1,000 degrees.
33:15Like Venus in the past, Earth will get hotter and hotter.
33:20But unlike Venus, which plateaued at 500 degrees Celsius, temperatures on Earth will keep climbing.
33:31Venus lost its water to space, blasted away by the solar wind.
33:37But Earth will hold on to its water, because it's protected by our magnetic shield.
33:43However that is no longer a good thing.
33:51Unlike Venus, Earth has a strong magnetic field, which protects it from the erosion
33:55of the solar wind. That water will stay with us.
33:58The Earth could have a thicker, hotter greenhouse atmosphere than Venus does today, much worse.
34:06This huge volume of water vapor will push down on the surface, increasing the surface
34:14pressure by 270 times.
34:19If by some miracle a human stepped out onto the surface, they would instantly be crushed
34:25by the atmosphere. Its weight would be more than a fully armored tank pushing down on
34:30their head.
34:32It is ironic to think that the water on Earth will one day help contribute to its demise.
34:38After all, the water has been the source of life on Earth.
34:41But in the far future, it will become our enemy.
34:47And with no oceans and their microscopic creatures to absorb the carbon dioxide, there's nothing
34:53to hold back the rising temperatures.
34:57Earth is doomed.
35:15In 1.2 billion years, a probe visiting Earth would see an alien world.
35:22A scorched, barren landscape.
35:27The pressure is crushing.
35:32Temperatures reach 650 degrees Celsius.
35:37Molten metal snow down on the mountaintops.
35:41It's so hot, granite rock melts.
35:46The surface liquefies.
35:52At that point, the Earth will become a molten ball, very similar to what it was at the very
35:57beginning.
36:01Earth and Venus started as twins. Venus was destroyed by rampant global warming.
36:09Earth will follow the same path, then overtake it.
36:13It is inevitable that the Earth will someday not only be like Venus, but actually put it
36:19to shame.
36:25In 1.3 billion years, Earth could hit 2,000 degrees Celsius.
36:31Four times hotter than Venus.
36:34It'll be the hottest and deadliest planet in our solar system.
36:40For Earth and its inhabitants, it's the end of the road.
36:47Maybe we'll escape to space and send probes back to study our former home.
36:53A billion years from now, Earth could be an unimaginably terrible place.
37:00Right now, today, Venus is the evil twin of Earth, but in the distant future,
37:05Earth's surface temperature will be far hotter,
37:10and its surface pressure far greater than Venus's.
37:15At these kind of temperatures, where rock on the surface of the Earth is molten,
37:20it's hard to imagine any place there could be life.
37:25But there is hope.
37:32Astrobiologist Louis Dartnell thinks that some forms of life
37:36could survive such terrible conditions.
37:39We're here on top of a volcanic outcrop in Iceland,
37:43with this howling gale, whistling through the air.
37:47It's like a hurricane.
37:50We're on top of a volcanic outcrop in Iceland,
37:53with this howling gale whistling past our ears,
37:56the stench of hydrogen sulphide, of sulphurous fumes filling our nostrils.
38:01And this is about as close as we can get on Earth
38:04to high up in the Venusian atmosphere,
38:07about 30, 35 miles above the surface of the planet Venus.
38:11The air pressure is about the same as on Earth's surface.
38:15The temperature is pretty similar as well.
38:18But the cloud droplets are full of concentrated sulphuric acid,
38:22many, many times more concentrated than battery acid.
38:26It's a hostile, horrible environment.
38:30But bizarrely enough, there's good reasons to think that there may be life,
38:34Venusian life, high up in the clouds there,
38:37a kind of high-altitude aerial biosphere.
38:43If life can live up there,
38:45then perhaps it might survive high up in the clouds of future Earth.
38:51You can easily imagine these microorganisms evaporating in water particles
38:56and being transported to the upper atmosphere.
38:59Even though it turned into this toxic greenhouse planet,
39:03life could potentially still survive in that upper atmosphere.
39:10But what about us?
39:13We couldn't survive the high temperatures or pressures at the surface.
39:18And a life in the clouds doesn't seem likely.
39:22What's our future?
39:24If there was this life on Venus,
39:26clearly they weren't advanced enough to stop the changes in their atmosphere
39:31that led to Venus' current state.
39:33The question is, are we?
39:43Perhaps we'll leave our planet and find a new home.
39:53As the sun gets brighter, Earth will go the way of Venus,
39:57but then the worlds further out will get warmer and warmer.
40:01It'll be a progression outward of habitability.
40:06First, the polar ice caps on Mars will melt into oceans.
40:12Then, even further out,
40:14the sun's heat will unlock the water on Jupiter's moon Europa,
40:18transforming it into a water world.
40:23If we do this right, we could maybe just sort of hop from world to world
40:27and move farther out from the sun as the sun warms.
40:30Because these are going to be slow transitions.
40:33So there'd be like plenty of time to kind of engineer the right environments
40:37and sort of hop from world to world farther from the sun.
40:40So that might be one way that, you know,
40:42if there is intelligent life on a solar system where this is happening,
40:46it might just be a matter of sort of skipping from world to world
40:49and like following the habitable zones as they move outward in your solar system.
40:55But there is another solution.
40:58Stay and move the Earth further from the sun.
41:03Moving the Earth is at least imaginable,
41:05because in fact, as objects exchange gravitational energy,
41:09they move in or out in the solar system.
41:11It's happened to our planet.
41:13So I could imagine engineering things
41:15where we directed large asteroids and comets close to the Earth,
41:19but not to hit it.
41:23The gravity from these large objects
41:25would slowly alter our orbit.
41:28Gravitational energy would be exchanged
41:30and the Earth could slowly move out.
41:36Each gravitational jolt would only move Earth a short distance.
41:43But do it thousands or millions of times
41:46and we could push the Earth away from the sun.
41:50In theory, at least.
41:52Over a billion year period, it's possible to imagine
41:54it would require incredible technology
41:56and incredible coordination.
41:58The technology is possible.
42:00Whether humanity as a species could ever coordinate it
42:03is something I'm a little more skeptical about.
42:07It sounds like science fiction.
42:09But if we don't do something, the Earth will die.
42:13And we'll become just like Venus.
42:16Earth and Venus were probably born together as identical twins,
42:19but then their paths diverged.
42:21But now, lifetime is going to send that cycle all the way back
42:24and they'll die as identical twins again.
42:31In the grand scheme of things,
42:33they'll just be two charred twins, spinning in a circle.
42:39The Earth will die,
42:41and we'll become just like Venus.
42:45We're heading to oblivion in a backwater of the universe.
42:50On the cosmic scale, life is short.
42:56When you look at how Earth evolved and how Venus evolved,
43:00you can see the difference,
43:02even though it's two almost twin planets,
43:05how life and habitability could change over time.
43:09So habitability isn't always a permanent thing.
43:15On human scales, the universe seems the same every single day.
43:20But of course, that's because human life and human civilization
43:24is but a brief instant in cosmic time.
43:28On cosmic scales, the universe evolves and changes,
43:32and that makes the history of the universe remarkable.
43:40Our tale of two planets converges in the end.
43:44A cautionary tale about forces beyond our control.
43:50Perhaps a billion years of learning from Venus
43:53will ultimately save us from the same terrible fate.