How the Universe Works - S07E08 - Hunt for Alien Life
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00:00Earth, a planet defined by life.
00:07The amazing thing about life here on Earth is no matter where you look, you'll find it.
00:14But is Earth unique?
00:16The big question of our day is, does life exist somewhere else beside the Earth?
00:21Are we that special, or is life everywhere?
00:24The ingredients for life are spread throughout the universe.
00:28But then we started looking into space and saying, wait a second, that chemistry is everywhere.
00:35Is life inevitable?
00:38I think that there have to be planets out there that are capable of hosting life.
00:44What does life need to get started?
00:48And once started, can life spread?
00:52It's possible that life started on Mars and was transferred to Earth inside of a meteorite.
01:01Life has conquered our planet, but can life conquer the universe?
01:23The universe is a very big place.
01:27There are trillions of galaxies, each one home to millions of stars and an unimaginable
01:35number of planets.
01:38So where is everybody?
01:40One of the most basic philosophical questions is, are we alone?
01:45Are we the only ones looking out and thinking, what is all this?
01:49Is it all just for us?
01:51Or do we get to share it with anyone?
01:54I mean, that's about as fundamental a question as you get.
01:59What are the odds of life existing somewhere else?
02:04We just don't have a good insight to how probable life is anywhere in the universe.
02:12Life could possibly be forming everywhere.
02:14We don't quite know.
02:15There's a lot about life that we don't understand.
02:20All we know is that it happened at least once.
02:25But beyond this one little planet, we don't know whether or not it happened anywhere else.
02:34The universe is an unfriendly place.
02:40Planets with lava oceans circle too close to their stars.
02:45Pulsars blaze with deadly gamma rays and X-rays.
02:51Black holes consume everything in their path.
02:54Temperatures plummet close to absolute zero.
03:03It may seem impossible for life to survive in such hostile environments.
03:08But here on Earth, life exists against the odds in some very strange places.
03:16Life has actually permeated every part of our planet.
03:19There are places where you're like, how did you even get there?
03:24At first glance, a beautiful lake might seem like a good place for life.
03:29But California's Salton Sea is no paradise.
03:34The toxic salt waters are a killer.
03:41Surrounded by scorched desert and volcanic geothermal fields, it's a deadly environment.
03:53One of the last places on Earth you'd expect to find life would be in boiling mud vents.
03:59You can start to hear these vents because there's gas and there's water and mud slurry
04:08that's coming out right here.
04:10So these are active mud volcanoes.
04:12It's really hot.
04:15It's like 164 degrees Fahrenheit.
04:20But life is resilient, finding a home even here, inside volcanic vents in the California
04:26desert.
04:27We're in the middle of a really hot desert.
04:30And as the mud comes up, it's coming up hot and it's kind of acid.
04:34And yet there can be microbes in environments like this happily thriving away.
04:39This is an environment that is actually conducive to life, even though we think it might not
04:42be.
04:45Almost every inch of the Earth's surface is teeming with microscopic life forms.
04:51The thing about life on Earth is that it exists in so many different environments under
04:57such harsh and extreme conditions.
05:00It's like it hangs on no matter what you throw at it.
05:03Very dry, high pressure, very hot, even in high radiation environments, which would kill
05:09a human within seconds.
05:14Life even survives being bombed with asteroids and meteorites.
05:21We have a wonderful indirect example of just how tenacious life is.
05:25And that's the fact that it survived the late heavy bombardment.
05:30The late heavy bombardment was a violent assault on young Earth, where life had just gotten
05:35a foothold.
05:38Experts think around four billion years ago, asteroids, comets, and space debris rained
05:44down on the inner solar system.
05:47This rocky barrage would have melted parts of the Earth's crust and boiled away oceans.
05:53It was a violent time called the Hadean Period.
05:58The Hadean, named after Hades, named after the underworld, after hell.
06:03It was a brutally unpleasant place to be.
06:06It was spewing its own innards out onto the surface in this intense cycle of hot volcanism.
06:16If life on Earth overcame these hellish conditions, then perhaps life can survive anywhere.
06:24I think if it can happen on Earth, I think it can happen on other planets.
06:28I think life finds a way, and I think we need to go looking for it.
06:35The question is, what exactly are we looking for?
06:40What is life?
06:41You know, that seems like a simple question, but it's not that easy to answer.
06:46Life is incredibly hard to define, right?
06:47It's sort of like you know it when you see it, but how do you write down the rules?
06:52Every time we think we have a grasp, there's this new form that comes about and completely
06:57questions that entire definition.
06:59There's a joke in astrobiology that if you ask 200 scientists for a definition of life,
07:04you'll get 200 different answers.
07:08Life can be as intricate as us humans or as simple as single-celled organisms like bacteria.
07:15But there are some things all life forms do.
07:20In broad terms, life consumes things.
07:23It breathes, it eats, it excretes, it grows, it reproduces, it's complex.
07:32Life has transformed the Earth in all sorts of ways, but life is still just an accident.
07:43Life as I see it, it's just a chemical reaction, but it's the most important and special chemical
07:49reaction in the universe.
07:52If life is just a product of chemistry, then what are the odds of it starting anywhere
07:58in the universe?
08:00One thing we know about chemistry is that given the right conditions, the same chemical
08:05reaction will reliably occur.
08:10It's like a game of chance.
08:11For life to win, the conditions need to be just right, but to figure out the odds, we
08:17need to understand what those conditions are and how common they are.
08:22So it comes down to a numbers game.
08:25It's about statistics and probabilities and likelihoods.
08:29It's like having to roll a six for each condition for life.
08:34But how many sixes would you need?
08:37How many precise conditions does life require to get going?
08:42You might have a hundred dice, roll them all, get all sixes, only then do you get life.
08:48You could need hundreds or hundreds of thousands of dice.
08:53We just don't know.
08:54We honestly have no clue how common or rare life is in the universe.
09:01We don't know how life originated here on Earth, where we kind of understand the conditions.
09:06There are a lot of different ways life could have started.
09:11Is life rare?
09:12Is life common?
09:13We don't know where it lands.
09:16Putting odds on life existing is a waste of time until we understand it better.
09:23And maybe our answers don't lie here on Earth.
09:27One way to crack this problem is to go looking for life elsewhere.
09:32If we can find other examples of life, we can immediately begin to put a quantitative
09:37answer to how probable it is for life to happen anywhere.
09:42And the best place to look for life might be in our own backyard, Mars.
09:53If life can start here, then maybe life could conquer the universe.
10:08For life to conquer the universe, first it has to get going.
10:14When we look at life on Earth, it's possible that it all has a common ancestor.
10:19Life started at one spot, branched out, and became all the different kinds of life that
10:23we see.
10:26But how did it start?
10:28The first question to answer is, what is life made of?
10:33Top of the list are the most basic building blocks, chemical elements.
10:39Here's what I know about the universe.
10:41The laws of physics appear to be the same everywhere.
10:45The chemical composition, the elements, are the same everywhere.
10:51And the cosmos creates these elements not from the Big Bang, but from stars.
10:56Over the course of a star's life, it creates elements.
11:01And when a star dies, these elements are blasted out into space in a supernova, spreading the
11:07ingredients for life out into the cosmos.
11:12We, the Earth, our solar system, all the ingredients that make us, us, were forged
11:18in nuclear fires.
11:21So the death of stars leads to the birth of life.
11:29Those key ingredients include oxygen, nitrogen, sulfur, and phosphorous.
11:34But the element most central to life as we know it is carbon.
11:41All life as we know it on Earth is based on carbon.
11:45Carbon forms the structure, the architecture of our living molecules.
11:54Carbon is an incredibly versatile building material.
11:59It can bond with other elements to form long-chain molecules, each with different properties.
12:06As an element, it seems to be capable of producing a vast and complex chemistry.
12:15And that complex chemistry is what we find in life.
12:20We call this organic chemistry.
12:26But getting from basic organic molecules to complex life forms is a big leap.
12:32We don't really have the slightest idea, to be honest, about how life on Earth got
12:39started.
12:40A really big question is how you go from a mix of relatively simple organic molecules
12:47to a living system.
12:50We know it all starts with basic elements, created in massive quantities by the death
12:56of stars.
12:59How do you start connecting those Lego bricks together to build that first cell?
13:04The short answer is we don't know.
13:08But we have some ideas of potential steps.
13:12Chains of organic molecules become more and more complex.
13:16Amino acids form proteins.
13:19Fatty acids form phospholipids, which make cell membranes.
13:25Organic acids form DNA, the molecule that stores genetic information.
13:30Eventually, a simple cell emerges.
13:35All of the bits you need to plug together to build a cell from scratch seems to exist
13:41in outer space.
13:44We found organic compounds everywhere.
13:46They're all over the place.
13:48Planets, comets, gas clouds.
13:54Those are the very basic ingredients of life available elsewhere in our solar system.
14:01So there could be life everywhere.
14:04In 2018, NASA announces it's found organic molecules on another planet, a planet we've
14:15always suspected of harboring alien life, Mars.
14:21So whenever NASA has a press conference and they say they have some important results
14:25to report on about Mars, everyone goes nuts.
14:28The internet goes mad.
14:31Maybe we've got photographic evidence of little green men and an UFO.
14:36This time, it's the Martians.
14:37They're going to tell us they found the Martians.
14:40The world listens because everyone wants to know.
14:43Everyone asks the question, have we found evidence of life?
14:48For six years, the Mars Curiosity rover has been exploring a region called Gale Crater,
14:55hunting for signs of ancient life, a bit like fossil hunting on Earth.
15:03Gale Crater is not unlike places on Earth that can preserve fossils.
15:07So a really good example of this would be the Petrified Forest in Arizona.
15:12This looks like a piece of wood, but in fact, it is stone.
15:17It is all stone.
15:18But it used to be a tree.
15:20This fossil lived 200 million years ago.
15:25This patch of desert in Arizona once looked completely different.
15:31This landscape looks very dry right now, but 200 million years ago, it was wet swampland
15:36with trees and flowing water.
15:41Like the Petrified Forest, Mars has also changed over time.
15:46Gale Crater was once a lake bed filled with fresh water.
15:50And it was just so exciting because we knew then that we had landed right on top of an
15:57environment that once had tons of flowing water and could very well have preserved organic
16:02materials, even though it looks very barren and desolate to our eyes.
16:08In 2018, Curiosity drills into this ancient Martian lake and discovers organic molecules.
16:19Finding organics on Mars is so exciting just because, I mean, wow, that is the, those are
16:26the building blocks of life, not just the elements, but actual molecules.
16:29There was a wave of excitement after the announcement of organics found on Mars and complex organics.
16:37It's not totally indicative that life is there, but it's a really good telltale sign
16:41that there may be possibly life forms on Mars.
16:47The results aren't proof of Martians, but the ancient lake bed is evidence that the
16:53red planet once had something else crucial for life.
16:58Liquid water.
17:03It's one thing if you have all these ingredients lying around for life.
17:06You could have, you know, carbon over here and hydrogen over here, maybe methane or whatever.
17:09But you have to mix them together.
17:11So you need something for them to be in, a medium of some sort.
17:16Life needs a liquid to mix essential chemicals together.
17:22We're used to thinking of Earth as the only water world in our solar system.
17:28But new evidence says otherwise.
17:34As extraterrestrial visitors carrying liquid water from outer space reveal.
17:51It's no coincidence our blue planet is a water world.
17:55There are more than 366 million trillion gallons of water on Earth.
18:03It even makes up 60% of our bodies.
18:06I think life on Earth could be easily described as water chemistry.
18:11That is the essential feature of life on Earth.
18:15Some is locked up in ice caps or is vapor in the air.
18:20But 96% of liquid water is in our oceans.
18:25Well Earth is really special.
18:27There's no other place like it that we found.
18:30It's a pretty substantial planet with liquid water covering 70% of the surface.
18:36All life on the Earth requires bodies of water in order to survive.
18:39No water, no life.
18:43Water is what chemists call a solvent.
18:47And it's the best solvent we know of.
18:51It can dissolve more substances than any other liquid, allowing molecules to mix and interact.
18:58Wherever water goes, it transports valuable chemicals, minerals and nutrients.
19:05If there was no liquid, things would just sit around separately.
19:09You need this constant interaction and you need a different chemical mix.
19:13And water does all of that.
19:18And so a lot of our searches for life-like planets or Earth-like planets outside our
19:23solar system are based on this sort of primary assumption that we need liquid water.
19:32We've long thought Earth has liquid water because of its unique position in the solar
19:37system.
19:40It's right in this zone that we call the habitable zone where the sunlight can support liquid
19:46water on the surface of the planet.
19:52But we have now discovered that liquid water might exist in places we never expected.
20:00In 1998, a meteorite crash lands in Texas.
20:09Today scientists at Arizona State University are still studying its secrets.
20:16We had no idea that it would contain this really, really spectacular finding.
20:21It contains a mysterious purple mineral.
20:25The exotic color comes from exposure to cosmic radiation.
20:29But the compound itself is very ordinary.
20:32It's actually sodium chloride, which is essentially the same mineral as table salt.
20:39But what's really cool is that it actually contains little globules of liquid water.
20:44And that liquid water was trapped in these crystals four and a half billion years ago.
20:51In 2018, scientists re-examined the crystals and discovered the liquid water wasn't traveling
20:57alone.
20:59We've now actually found organic compounds in association with this liquid water in these
21:04salt crystals.
21:05And that's something that's really new and really spectacular.
21:13We actually found amino acids, the building blocks of all of our proteins, even our DNA.
21:18And we found liquid water, the very building blocks of life inside a meteorite.
21:25So could life exist somewhere else in our solar system?
21:33A NASA mission to Saturn turned up some shocking results.
21:37The Cassini space probe flew beneath Saturn's moon, Enceladus.
21:42Enceladus, no one cared about.
21:45It was a tiny little snowball of a world.
21:51But Enceladus surprised everyone.
21:57Geysers of liquid water, dozens of them, blast out of trenches along the moon's surface,
22:04coming from a vast subsurface ocean.
22:12Things on Earth are full of life.
22:18Could the same be true of Enceladus?
22:21I'm a big fan of Enceladus.
22:23I think it's by far and away the best place to go to search for evidence of life.
22:30In 2018, researchers analyzing the Cassini data discovered that the plumes of Enceladus
22:36contain complex organic molecules.
22:40Simple molecules, we find those, like methane.
22:43But the Cassini results are showing that there are these more complex, larger organic molecules
22:49as well.
22:50This is the first ever detection of complex organics on an extraterrestrial water world.
22:56All of a sudden, here's water jetting out, carrying organic material, all the ingredients
23:02needed for life.
23:04It was like too good to be true.
23:08But Enceladus isn't the only small world with a subsurface ocean.
23:12Other moons and dwarf planets have liquid water too.
23:17We think the most important thing for life to form is the presence of liquid water.
23:21And our solar system seems to be full of it.
23:26The discovery of liquid water in the outer solar system changes the rules of how life
23:34might originate in the universe.
23:41Across the universe, alien life could be hiding underneath the surface.
23:47Internal water oceans are far more common than surface water oceans.
23:54So if there is a lot of life out there in the universe, chances are it's in an internal
23:59ocean under miles of ice.
24:04Who knows what might be lurking inside icy exo-worlds.
24:09There may be jellyfish and octopuses all over the place in exo-moons and exoplanets under
24:15ice that have civilizations that we just don't know about.
24:19Finding liquid water oceans could open up a world of possibilities.
24:26If you're not excited about intelligent extraterrestrial octopus civilizations, I don't know what to say.
24:35The chances of finding life in our solar system just got a heck of a lot better.
24:44Building blocks in liquid water are common.
24:47But you need more than just these two conditions for life to take hold.
24:52Life needs a spark.
24:55Life appears to need some form of energy to actually get the molecules interacting.
24:59One thing that may have helped kickstart life on Earth is ultraviolet radiation from the sun.
25:04Ultraviolet light is emitted by all stars.
25:07There are billions of stars in our galaxy.
25:11Can life get started around any star?
25:15Or is our sun unique?
25:26Earth is a solar-powered planet.
25:29At the bottom of the food chain, plants use photosynthesis to convert sunlight into chemical energy.
25:36Food for the rest of us.
25:38I like eating both grass, essentially wheat, and I also fancy the odd hamburger from a cow that is eating that grass.
25:46This whole ecosystem is powered by sunshine.
25:51But recent studies have shed new light on how life developed under our sun.
25:58Specifically, the role of ultraviolet light.
26:02UV radiation is useful for breaking molecules up and triggering reactions.
26:08Maybe that played a role in the origin of life.
26:11It breaks down simple organic molecules and then they can rebuild themselves into things that are more complex.
26:17If you do that over and over again, eventually you somehow get life.
26:24Scientists think life on Earth started around 4 billion years ago.
26:32A time when Earth's atmosphere gave little protection.
26:39UV radiation levels were 100 times higher.
26:45Was UV essential for the development of life's code, DNA?
26:51We know that life on Earth stores information in DNA and then uses that information to build proteins.
26:59So we have the blueprints and the bricks.
27:02The blueprints are the DNA and the bricks are the proteins.
27:06But we think that the first life on Earth, we used a chemical which is much simpler.
27:14This simpler chemical was RNA, DNA's single-stranded forefather.
27:22RNA is almost like a two-for-one offer.
27:26It does both of the fundamental things you need for a cell in the same compound.
27:33So it was simultaneously the bricks and the blueprint.
27:38Unlike other molecules, RNA is more resistant to the high UV environment of early Earth, allowing it to flourish.
27:49RNA eventually evolved into DNA and life started.
27:55To have life on the planet, one important consideration is a certain amount of light that's going to be needed.
28:00And a certain type of light that's going to be needed.
28:07So if all stars emit some UV radiation, can life start around any star?
28:14When we think about looking for places that are conducive for life, we want to find a planet that might have enough UV radiation.
28:21So the star is bright enough or close enough that it's providing enough energy to the surface for life.
28:27But we also don't want to have too much UV radiation.
28:32It seems you need just the right amount of UV.
28:41The most common stars in the galaxy are red dwarf stars.
28:47If red dwarf stars can harbor life on planets around them, there's an awful lot of real estate like that in our galaxy.
28:58Red dwarf stars could be good for life's chance of conquering the universe in a number of ways.
29:05One, they represent over three quarters of all stars in the universe.
29:09Two, they live for over a thousand times longer than sun-like stars.
29:13And three, they seem to have rocky planets around them much more often than sun-like stars do.
29:19Those are the pros. But red dwarf stars also have cons.
29:25For instance, they might not be bright enough for life to begin.
29:30Some of the red dwarf stars that we know emit less ultraviolet light than the sun.
29:35They don't give off much UV light at all. Maybe on a planet around them there isn't enough energy to get life started.
29:42Red dwarf stars are also much more temperamental.
29:46They can go from being gentle and quiet to having violent outbursts.
29:54These types of stars have incredibly strong flares.
29:58That means they're shooting off a bunch of energetic particles and radiation and light that's baking the surface of those planets.
30:07If the star is just bombarding the surface with UV, then it will destroy all of those things necessary for life.
30:14It will actually destroy the life itself.
30:18These stellar flares could strip away a planet's atmosphere, sterilizing the surface.
30:28More research is needed. But for now, the odds of life thriving around dwarf stars are a toss-up.
30:36So far, the only thing we know is that there is one kind of star that's definitely right for life.
30:42Our sun.
30:44We know of life in one place in the universe, and that's here. That's Earth.
30:49Only 4% of stars in the universe are like our sun.
30:55So, if life can only get started, then life can only go on.
31:02So, if life can only get started around these rare, medium-sized stars, the chances are not looking good.
31:16But life may have an ace up its sleeve.
31:19What if life can start on just one planet and then spread?
31:25What if life travels across the cosmos, looking for planets to conquer?
31:40Earth is our only example of life emerging anywhere in the universe.
31:46But what if life on Earth didn't start on Earth at all?
31:51There's one idea that life on Earth actually didn't get going here, but was delivered from space.
31:56Scientists call this theory panspermia.
32:01The idea of panspermia essentially talks about the transferal of life throughout the cosmos.
32:08We know asteroids and comets carry organic molecules. But could they carry life itself?
32:16What if life starts on one planet? Can it actually get itself to a nearby planet?
32:23Is it possible that meteorites could actually transport living beings?
32:28For life to travel around the cosmos, first it needs to take flight.
32:35An asteroid is on a collision course with an inhabited planet.
32:40So what happens if there's a huge cataclysmic collision on a planet?
32:44Material is blasted off into space.
32:51The impact might kill life on the surface of that planet.
32:54But it's possible some bacteria might escape, hitching a ride on chunks of the planet's surface.
33:04A meteorite being ejected from a planet after an asteroid impact, I mean, that's not going to be an easy ride.
33:10But it turns out it's not as bad as you think.
33:13Some bacteria are very, very hard to kill. Some we even don't know how to kill.
33:18Even the impact that actually threw that rock into space, for bacteria, no problem.
33:23If those chunks of rock expelled during asteroid collisions could actually hold on to viable organisms,
33:30then it really could change the way in which we think about life spreading in the universe.
33:38If the microbes can survive takeoff, then they can start their journey to a new home.
33:44The odds of life conquering the universe seem to be getting better.
33:48The important question now is how long could that life, those bacteria, those microorganisms inside that rock, survive the space environment?
33:58Exposure to UV radiation could be fatal, killing any life on the surface of an asteroid.
34:05But experts think that microbial passengers could still survive by hiding underground.
34:12It doesn't take much to shield a microorganism from UV.
34:16Just a little bit of rock and you have enough protection to just hold on throughout a journey to the next body, to your next home.
34:26Eventually, they could arrive at an uninhabited world that's ready and waiting for life.
34:32But they're in for a bumpy landing. Would the rock burn up coming through a planet's atmosphere?
34:39It's in for a hot ride, but only for a few seconds.
34:42And only the outer layers of that rock will blow off.
34:45And then it just falls and hits the ground not that fast, a couple hundred miles an hour.
34:51If a human were in there, that would be bad. But for a bacterium, no big deal.
34:56The panspermia theory says life could start on just one planet, then spread to another planet, and possibly another.
35:06If we found alien lifeforms, would they look familiar?
35:11One of the biggest questions about finding other life in the solar system is how similar will it be to us?
35:17If it's just like us, it begs the question, did we have a common genesis?
35:22Did we originally come from another planet?
35:26One radical idea is that life on Earth came from Mars.
35:32Imagine Mars three and a half, four billion years ago.
35:36It was more Earth-like then than Earth was at that point. The Earth was still quite warm.
35:41Mars actually had cooled off faster, had a thick atmosphere, water. Life could have arisen there.
35:47Mars has been hit repeatedly by meteors,
35:51sending chunks of the planet flying off into space.
35:55And some of those chunks have landed here on Earth.
36:00So this is a really unusual meteorite. It was found near the city of Los Angeles.
36:07And we actually know that it actually came from the planet Mars.
36:12And we know that because it has gases trapped inside it that have the exact same composition as a Martian atmosphere.
36:19There's been a lot of transit between meteor strikes hitting Mars and on Earth.
36:23There's a little bit of Mars on Earth. There's a little bit of Earth on Mars.
36:27It's possible that life started on Mars and was transferred to Earth inside of a meteorite.
36:35When you think about it, maybe we're the immigrants. We are the Martians.
36:41Life on Earth started on Mars and got transferred here.
36:46Panspermia could allow life to spread from planet to planet, conquering our solar system.
36:52But what about even greater distances?
36:56In 2017, the cigar-shaped space rock, Oumuamua, appeared in our solar system.
37:03It came from interstellar space, and experts think it could be carrying organic matter.
37:09One of the fascinating things about Oumuamua is it has sort of a reddened surface.
37:13Now, that could actually partially be from the presence of organic molecules.
37:17Could life survive interstellar or even intergalactic travel?
37:22Whether or not this is an easy way to transfer life around in the universe is still an open question.
37:29The possibility of transferring life from star system to star system seems a little bit remote.
37:35The immense distances and dangers of interstellar travel would be hard to survive.
37:40Some experts think there is one way for life to conquer the universe.
37:48But it won't be life as we know it.
37:52The universe is unimaginably large.
37:55Many experts believe there is life out there.
37:59We just have to go find it.
38:02One of the things I love about being a human is the fact that I'm born with this curiosity.
38:07This curiosity drives us to explore, explore, explore, explore, explore, explore.
38:13One of the things I love about being a human is the fact that I'm born with this curiosity.
38:18This curiosity drives us to explore, explore Earth, explore our solar system and beyond, into the galaxy, look for other life forms.
38:27But with current technology, it would take thousands of years just to reach the nearest star.
38:34It's unlikely humans will ever leave our galaxy.
38:39If life one day does spread from Earth into the cosmos, it's probably not just going to be a bunch of meat bags like us,
38:48but other forms of life that are more suited for interstellar and intergalactic travel.
38:55Our fragile bodies are not suited to the distances and dangers of interstellar travel.
39:01Machine life may be more robust for traveling between planets and between stars than biological life.
39:12There are a lot of scientists who think that when we encounter aliens, we won't be encountering them,
39:17we'll be encountering their machines, because we can build machines that can last a million years, go from one star to the next.
39:23It's much easier than transporting us fragile, gloppy bags of meat.
39:27And so if we go out into space, we're more likely to find robots than we are biological life.
39:34For humanity to discover alien life, humanity itself may have to evolve from biological life to artificial life.
39:46What's really ironic here is that while we're figuring out the origin of life on Earth,
39:54we humans could be inventing a form of life on our own, and that is what we call artificial intelligence.
40:02The development of AI, self-replicating machines even, may very well be just the next key transition in our evolutionary history.
40:15Could a super-intelligent, self-replicating machine conquer the universe?
40:21Maybe this AI can fashion its own machines, create factories to create resources to replicate itself,
40:29create ships that will allow it to travel from one place in the universe to another.
40:38But would AI represent a new form of life?
40:42I think the answer is yes, and I think it actually goes on from there.
40:45I think artificial intelligence might be the next necessary stage in evolution.
40:50We made the computers. They are our children.
40:54I think of life as a process that can retain its complexity and reproduce.
41:01So bacteria are life, humans are life, and some future creation of advanced artificial intelligence that can do those things should also count as life.
41:16Life could take many forms, and in such a vast universe, it could be that life is inevitable.
41:27With all those stars and all those planets, I think, without a doubt, there is a good chance that life has developed elsewhere in our universe.
41:37Must life happen in our universe? Is it an inevitable consequence of processes in operation? Maybe, maybe not.
41:52Until we find it, we won't know for sure whether life can conquer the universe.