How the Universe Works - S08E03 - Hunt for Alien Evidence
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00:00Aliens.
00:07Little green men.
00:08A thousand eyes or one eye.
00:11Sci-fi movie monsters.
00:13Free floating with tentacles.
00:15Some unknown hyper-advanced civilization.
00:19Could science fiction ever become fact?
00:23I think it's really simple why Hollywood is fascinated with the concept of first contact
00:27with aliens, because that would be probably the greatest scientific discovery in all of
00:32human history.
00:35Problem is, our universe creates massive barriers to meeting extraterrestrials.
00:41It's almost as if the universe is deliberately stopping us from making first contact.
00:48We're searching the cosmos.
00:50Will we ever find intelligent alien life, or are we alone?
01:13Arecibo Observatory, Puerto Rico.
01:19Forty-five years ago, it sent a powerful radio message deep into space, kick-starting
01:26our efforts to make first contact.
01:30The Arecibo message was the first communication or attempt to communicate with a possible
01:37civilization out there in the galaxy or outside of our galaxy.
01:42Today that message is speeding towards the M13 galaxy cluster, 25,000 light years away.
01:51It contains information about our world, where we are, even the makeup of our DNA.
02:00The purpose of this message was, of course, like trying to say hi, and also like to light
02:06up this question about, are we alone in the universe?
02:13But what chances are there that an intelligent alien race is out there, waiting to receive
02:20our message?
02:23Do I think there's other intelligent life out there in the universe?
02:26The answer is a resounding yes, yes I do.
02:28We know that life began on Earth pretty much as soon as our planet solidified.
02:32But why wouldn't that have happened somewhere else?
02:36If life has evolved on other worlds, just how many alien civilizations are out there
02:42that we could potentially contact?
02:46Astronomer Frank Drake developed an equation to help answer this crucial question.
02:53The Drake equation is a really admirable attempt to apply some quantitative reasoning to the
02:59probability or the possibility that there is life beyond the Earth.
03:04You multiply the star formation rate for stars in our galaxy times the number of planets
03:10that each star has, times the probability that you would have life forming on that planet,
03:17times the probability that that life form becomes intelligent.
03:21And they estimated that there were about 10,000 intelligent civilizations within our galaxy.
03:29Since the Drake equation was first proposed, our understanding of the galaxy has radically
03:39transformed.
03:41We have now discovered worlds outside our solar system, exoplanets.
03:49Exoplanets are being discovered all over the place.
03:52There are about 4,000 of them now known, and techniques are finding more every day.
04:00Scientists believe what we've found is the tip of the iceberg.
04:06So if the cosmos is so good at making planets, perhaps it can produce the conditions to make
04:12life throughout the universe.
04:15When the Drake equation was devised all those decades ago, we didn't know that exoplanets
04:20existed.
04:22And now we think that there are quite literally more planets than there are stars in the universe.
04:27So even if life is really rare, there are an enormous number of chances for it to take
04:32hold in the universe.
04:34And for this reason, it is very likely that there is life relatively abundant in the universe,
04:38including an uncountable number of advanced alien civilizations.
04:42This isn't science fiction.
04:44It's just basic probability.
04:48If probability suggests a multitude of alien civilizations are out there, isn't it a little
04:55strange we haven't made first contact?
04:59I think there's every reason to believe that there are civilizations out there, but we
05:03have no evidence of them yet.
05:05Why haven't we found other civilizations out there?
05:09One answer could be the sheer vastness of the cosmos.
05:14Look at all these lights out here over the cityscape.
05:17You could think of these lights as like stars in the galaxy.
05:21Now, if there's 10,000 communicating civilizations out there in the galaxy, you might think,
05:25oh, man, look, there's one right there, right down the street.
05:29The problem is there are hundreds of billions of stars in the galaxy, which means that maybe
05:34our nearest neighbor that we can communicate with is not right there, but way across the
05:39city.
05:42We live in the suburbs of the Milky Way, 75,000 light years from the furthest edge.
05:51Radio signals travel at the speed of light.
05:57This speed limit means that any signal sent to the opposite side of the galaxy would take
06:0375,000 years to reach its destination.
06:08The thing you have to remember is the galaxy is gigantic.
06:11Even if there are 10,000 civilizations in the galaxy, it's possible that the distances
06:16between stars are just so huge that we're never going to be able to communicate with
06:20each other.
06:22So the 45-year-old Arecibo radio message could still be tens of thousands of years away from
06:28any potential alien civilization.
06:32The target was 25,000 light years from here.
06:35The message is now 45 light years from here because it's traveling the speed of light,
06:40so it's really far from the target.
06:43The vast size of the universe is a huge roadblock to making first contact, and the laws of physics
06:50prevent radio signals from overcoming it.
06:54You just cannot go faster than the speed of light.
06:57So our galaxy may be filled with life, filled with civilizations, but they're so far away.
07:03I don't want to be the bearer of bad news, but the universe is just really, really far
07:09too large.
07:12The universe may be large, but we're putting the most advanced technology on Earth into
07:17action to try and speed up the search.
07:21There really is a serious, scientifically valid way to go looking for other civilizations,
07:26and the Breakthrough Listen project is really the best thing we have right now.
07:30State-of-the-art facilities around the world, radio telescopes, optical telescopes as well,
07:35are all looking up to the sky together.
07:37Breakthrough Listen is targeting the one million stars and 100 galaxies closest to Earth.
07:44It's the most comprehensive search for intelligent extraterrestrial communications ever undertaken.
07:53If there was an aircraft giving off a radar signal, and that aircraft was around any of
07:58the 1,000 nearest stars, the Breakthrough Listen project could hear that.
08:02So if there's something out there that's actually giving off a signal, Breakthrough Listen has
08:06a chance to find it.
08:08Breakthrough has started by listening in on the nearest 1,700 stars to Earth.
08:15So far, silence.
08:17This is the wonderfully, beautifully frustrating position that we find ourselves in.
08:21We haven't heard anything yet.
08:23So we're in this position where a negative result doesn't mean there aren't civilizations,
08:27but we have no proof that there are.
08:30Breakthrough Listen is just beginning its hunt.
08:33There's much more real estate in the cosmos for it to search.
08:38It's a big job, demanding a lot of patience.
08:42If you go through Drake's equation and find this number of 10,000
08:46intelligent civilizations out there, there are something like 250 billion stars in the galaxy.
08:53So that's only one civilization per 25 million stars.
08:58That's a lot of cold calling.
09:00The size of our universe means we could be waiting a very long time to pick up any alien
09:06communication.
09:12But even if we pick up a signal, it may have arrived too late.
09:18If we do receive a message, given that it probably took years to get here,
09:21that civilization could be long gone.
09:25Are we simply too late?
09:26Have any aliens already died out?
09:34Earth has orbited the sun for over 4.5 billion years,
09:41time enough for humankind to evolve into an intelligent and technologically advanced species.
09:49But compared to the age of the universe, planet Earth is only a few years old.
09:56It's just a kid.
09:58The Earth is over 4.5 billion years old,
10:01and we think it's taken this long to create the first technological civilization, us.
10:06There are star systems out there much older than we are.
10:09The universe is 13.8 billion years old.
10:13We tend to think we're hot stuff, right?
10:16We're technologically capable.
10:17We can build rockets and we can listen to radio waves.
10:20But a typical other intelligent advanced civilization
10:24would be literally millions of years ahead of us in technology.
10:32So if an alien society has been around much longer than us,
10:36how much more technologically advanced could they be?
10:41One method of measuring is provided by the Kardashev scale.
10:45The Kardashev scale classifies potential alien civilizations into three types
10:50based on the amount of energy that they're able to harness from their local environment.
10:54A type one civilization can harness the energy of only its home planet.
10:58A type two could hypothetically harness the energy of its own solar system.
11:01And a type three could harness the energy potentially of an entire galaxy.
11:07If you're wondering where we fit on the scale, prepare for some bad news.
11:13We're somewhere between a zero and a one.
11:15We can't use all of Earth's resources.
11:18So we're at about a 0.7.
11:21An advanced species reaching Kardashev level two, or even three,
11:26could create highly advanced structures that could harness the power of a star.
11:32If you get to be an advanced enough civilization,
11:35eventually if your energy demands are so huge,
11:38you might build solar panels that you have enveloped your star.
11:43This was first thought of by Freeman Dyson.
11:45And so we call these Dyson spheres.
11:50If such epic engineering occurs in other star systems, or even other galaxies,
11:57could we pick up some evidence and then make first contact?
12:02The thing about a Dyson sphere is that you've completely blocked
12:06all the light coming out from a star, except for the infrared.
12:11Because these panels are absorbing that sunlight and warming up.
12:14When you warm up an object, it gives off what's called thermal infrared light.
12:18You can scan the skies looking for that signature
12:21to see if there are any Dyson spheres out there.
12:252015.
12:29NASA's Wide Field Infrared Survey Explorer scanned 100,000 nearby galaxies
12:35to locate advanced Kardashev civilizations
12:39by observing infrared light leaking away from Dyson spheres.
12:45They detected nothing.
12:48No such galaxy was found, so they didn't find any infrared smoking gun.
12:54Given our universe is so old, surely other civilizations should have had time to evolve.
13:00If so, maybe we've simply missed them.
13:04It's entirely possible that civilizations arose,
13:07tried to communicate with the galaxy around them.
13:09And the problem was they were asking too early for us.
13:12They're trying to knock on our door, but our house wasn't built yet.
13:17Earth has been around for under one-third of the universe's 13.8 billion year lifespan.
13:25The human race, just 300,000 years.
13:29A relatively tiny window of opportunity to make first contact.
13:34We've been looking at the sky for tens of years, something like that.
13:38What is the likelihood that at that exact moment,
13:40someone is going to be beaming a signal toward us?
13:42Perhaps the universe prevents intelligent civilizations from surviving for very long,
13:49making our chances for first contact even more unlikely.
13:54Maybe there is something out there that is filtering us from seeing them.
13:59We actually call this the great filter.
14:01Maybe there is something that says, yeah, you're not getting past here.
14:04Rocky planets like ours are ideal for hosting life, but they are fragile.
14:10And this fragility means the universe could filter out intelligent life quickly.
14:22We've discovered very violent star explosions like gamma ray bursts.
14:26These are powerful enough, they may sterilize planets even across an entire galaxy.
14:32We also see destruction in our own backyard.
14:36Take Venus, a rocky planet orbiting in the habitable zone around the sun, just like us.
14:43If I was an outside observer looking in at our solar system,
14:46I would actually target Venus and early Venus as a potential place that could be habitable.
14:52But if I was an outside observer looking in at our solar system,
14:56I would actually target Venus and early Venus as a potential place that could be habitable.
15:01Long ago, it may have supported life.
15:05But atmospheric conditions on rocky worlds like Venus
15:08can quickly transform them into death traps, with temperatures over 800 degrees Fahrenheit.
15:18Venus appears to have gone through a runaway greenhouse effect,
15:22where the amount of carbon dioxide kept on increasing in the atmosphere as the planet
15:27heated up. And without oceans and rivers and continental drift and things like that,
15:32there's no obvious way to recycle the carbon dioxide in the atmosphere.
15:37And so the outgassing and so on just keeps on increasing
15:40the concentration, and you end up with these hellishly high temperatures.
15:47And even if intelligent species survive natural phenomena,
15:52they may still be filtered out by hitting self-destruct.
15:58As we can tell from our own experience, the moment that we started developing technology,
16:03we also developed the means for our own destruction by changing the climate on our planet,
16:09by developing weapons of mass destruction. And so it's quite possible that civilizations that
16:14are advanced enough are short-lived. And if they are short-lived, that would explain why
16:19at this point in time, there are very few of them that might be around to communicate with us.
16:28Finding the relics of an extinct alien civilization
16:31could be the ultimate cosmic warning for the human race.
16:36If we were to find a civilization out there that may have destroyed themselves by pollution or
16:40conflict, it would be almost like staring into a mirror, and it would be a very grim foreshadowing
16:48and maybe a lesson to learn for us humans here on Earth.
16:51We can only hope that some advanced alien species escape the universe's deadly filter.
16:58But even if E.T. still exists out there, the odds remain stacked against First Contact.
17:13One other way that we've got this alien contact story a bit wrong
17:19is just down to the laws of physics.
17:22Every day, the physics of the cosmos makes our chances of contact worse.
17:28Because our universe is expanding, and it's expanding fast.
17:40February 2018. Astrophysicists at the University of Oklahoma find a potential series of rogue
17:48planets 3.8 billion light-years away, ranging between the size of our Moon and Jupiter.
17:58These would be the first alien worlds ever discovered outside our galaxy.
18:05And maybe the first of many.
18:09Our galaxy alone has trillions of planets.
18:12The observable universe has trillions of galaxies.
18:14It's estimated about two trillion.
18:16So trillions of trillions?
18:19Come on.
18:20But finding exoplanets is no guarantee of finding alien life.
18:25And when it comes to contacting extraterrestrials, our efforts have met with silence.
18:32Our search for life has come up empty.
18:34Do we need to change our tactics?
18:35Are we doing something wrong?
18:40I think it's going to be very, very hard to find extraterrestrial intelligence
18:43the way that we're looking for it.
18:45We would have to get really, really good at it.
18:47But I don't think we're going to get lucky.
18:49I think that if we want to know whether there's life out there in the cosmos, we have to go visit it.
18:55We've sent the New Horizons probe billions of miles across the solar system to Pluto.
19:02Perhaps one day we'll be able to send spacecraft across the universe
19:06to search for alien life on distant rogue planets.
19:11But if a craft left our galaxy to visit these new worlds,
19:15its mission would be tough, thanks to the physics of the cosmos.
19:20From our perspective here in the Milky Way,
19:24every galaxy is on average receding away from us.
19:29So we're not going to be able to find life in the Milky Way.
19:32We're not going to be able to find life in the Milky Way.
19:35Every galaxy is on average receding away from us.
19:40It looks like nobody likes us and is trying to get as far away from us as possible.
19:46This is because our giant universe is expanding.
19:52When we talk about the expanding universe,
19:55we don't mean that galaxies are doing something active to run away from one another.
20:00Actually, it's the underlying space that's expanding
20:04and the galaxies are embedded in that,
20:05and that's what causes everything to move apart from everything else.
20:10The regions of the universe within three million light years of us
20:14are expanding at around 45 miles per second, over 160,000 miles per hour.
20:23So with our current technology,
20:24do we have any chance of actually seeing what these other planets are like?
20:28Well, think about the fastest and farthest things we have right now,
20:31like the Voyager spacecraft.
20:33They've been in space for more than 30 years, going incredibly fast, 38,000 miles an hour.
20:3938,000 miles an hour is fast.
20:43But the closest galaxies to us are moving away over four times faster.
20:50And the further away a probe is sent to travel, the tougher its task.
20:55The thing about the expansion of the universe is that the farther away something is,
20:59the faster it's moving away from you.
21:02The more distant two objects are away from each other,
21:05the more space there is between them.
21:08And the more space there is between them, the more space there is to expand.
21:14The rate at which they're moving away is proportional to their distance.
21:18If it's twice as far away, it moves away twice as fast.
21:21If it's three times farther away, it moves away three times as fast.
21:26Scale it up to the planets we've discovered, 3.8 billion light years away.
21:31And thanks to the expansion of the universe,
21:34those extragalactic worlds are moving away from us at over 49,000 miles per second.
21:42Imagine that you're a runner and you see the finish line.
21:45You're getting a bit closer to it.
21:47But now, actually, the track itself is expanding.
21:50And as the track expands faster and faster, it's expanding faster than you can possibly run.
21:55All of a sudden, that finish line starts receding and you're never, ever going to reach it.
22:00Say one day we're able to build probes that travel at the fastest speed physics allows,
22:10the speed of light.
22:14Even that might not be enough because sometimes
22:18the universe itself doesn't play by the rules.
22:22It's not possible for things to travel through space faster than the speed of light,
22:27but it is possible for space to expand faster than the speed of light.
22:32Everywhere we look, we see very distant galaxies
22:34that are apparently receding or moving away from Earth at greater than the speed of light.
22:39There are distant galaxies we can see in the sky that even if we were to build the
22:42most advanced spaceship possible that could even move at the speed of light,
22:46we could never get there.
22:4897% of the galaxies that we can see in the distant sky are actually unreachable to us.
22:54For all the galaxies out there, and all the planets that could harbor life,
22:59most of them are out of our reach.
23:04The physics of the universe has dealt an immense blow to first contact.
23:09The true reality of the universe will always be hidden from us because of this,
23:13because of this expansion.
23:16The further we look out into the universe, the more unlikely first contact becomes.
23:21We might need an advanced alien race to come and visit us instead.
23:27Suppose we get that lucky, even then, would first contact actually be feasible?
23:34We think aliens are like us.
23:36They're not.
23:36We're assuming that the life is like us,
23:39and that their planetary environment is like ours.
23:42I don't think that's going to be the case for most of the life in the universe.
23:46Could extraterrestrials even survive first contact with us and our planet?
23:56July 2019.
23:59The test satellite discovered a new alien world 31 light years from us named GJ357D.
24:08At over six times the mass of our home planet, it's thought to be a super-Earth.
24:14And from our observations, super-Earths appear to be prime real estate.
24:20What we see is that the most common type of terrestrial planet
24:23is what we call a super-Earth.
24:25So that means it's a terrestrial planet, but much more massive.
24:28More massive means more gravity,
24:31creating a planetary environment completely unlike our own,
24:35and life completely unlike ours.
24:39If they're on the surface of a super-Earth,
24:41it could be that gravity is going to be way stronger.
24:44So these aliens aren't going to be very tall,
24:47but they are going to be very strong.
24:49So if they're on the surface of a super-Earth,
24:51they could be much bigger than us.
24:54And if they're on the surface of a super-Earth,
24:56they're not going to be very tall, but they are going to be very strong.
25:01Super-Earths are just one of many avenues the universe creates.
25:06There are other exoplanets orbiting red stars,
25:1010 times smaller than our sun.
25:12And others making binary systems, comprising two stars instead of one.
25:18We see planets of all shapes and sizes around stars
25:23of all shapes and sizes of all sorts of configurations.
25:27The potential for life is much more rich and varied than we ever thought before.
25:34Metro rockets, five and six, fire.
25:39Images of science fiction have fueled numerous fantasies of first contact.
25:44But our knowledge of the universe suggests reality could be far, far stranger.
25:49If anything, Hollywood has kind of constrained our imagination
25:53in terms of presenting so many aliens that basically look like,
25:57you know, humans wearing a rubber suit or something.
25:59Lower landing legs.
26:03We have to, have to let go of this obsession that they're going to be anything like us.
26:09So if we're looking for two-legged dudes, forget it.
26:12Say an intelligent alien species lives in our stellar neighborhood
26:16and wants to make first contact.
26:19If that alien evolved on a super-Earth or orbited a red star instead of a yellow one,
26:24its wildly different biology may prevent it from ever setting foot,
26:29or tentacle, on planet Earth.
26:34But if we're looking for two-legged dudes,
26:36When you look at life here on Earth, it's almost as if it was custom-made for this temperature,
26:49for these elements, for this environment.
26:52An exoplanet with conditions to support life
26:54could still be completely different than life here on Earth.
26:59What are things going to be like on an alien world which has a little bit more potassium,
27:03or is warmer than average on Earth, or has a thicker atmosphere?
27:07Each one of these small variations can mean a completely different ecosystem.
27:15So could an alien organism really adapt to our ecosystem when it lands on Earth?
27:23Maybe we haven't made first contact because they can't actually visit us.
27:28They could step through the airlock of their spaceship onto the Earth
27:32and just find something toxic with our environment,
27:35some reason they're not compatible with the surface of the Earth.
27:39It's almost as if the universe is out there deliberately trying to stop us meeting any aliens.
27:47Biology creates another obstacle for making first contact.
27:51But as planetary scientist Jamie Radebaugh finds, even life on Earth can get really weird,
27:56taking extreme measures to adapt to a potentially hostile environment.
28:02This is the Great Salt Lake.
28:03It is the remains of what used to be a much larger lake in the past.
28:07And when it evaporated away, it left behind all of the salt.
28:13The Great Salt Lake is nearly 10 times saltier than the Earth's oceans.
28:18The extreme salt content should make it an inhospitable place for life.
28:24Despite this, there are organisms thriving in the water.
28:28As we look at life in this vast lake and find that there are
28:32billions of microbes living here in this unexpected environment,
28:35then we start to realize, well, life forms in ways that we just don't expect,
28:40in places we don't expect.
28:42Microbial life, known as extremophiles,
28:45have developed an ingenious way to survive in the lake.
28:49They actually use these solar-powered pumps to pull the salt
28:53out of their cells so that they can operate more normally.
28:56But in order to do that, they have to live very close to the surface,
28:59which means they get a huge amount of UV radiation.
29:02So all this pink color that you see behind me is actually the pink of the organisms,
29:07and it's sort of like a built-in sunscreen that helps protect them against the UV radiation.
29:12Extremophiles are rewriting our expectations on where life can survive on Earth.
29:19Could alien biology be much more resilient than we think?
29:23These extremophiles should be a little reminder that we haven't been thinking big enough.
29:29Maybe they could readily adapt to our environment.
29:33Or perhaps they've got other ideas, using technology to overcome any biological barriers.
29:41Maybe the first aliens we meet will be robots.
29:46They can build much more powerful life if they don't limit themselves to just
29:50advanced aliens could have left their biological brains and bodies behind,
29:55traveling instead as mobile artificial intelligence.
30:00We tend to think of intelligence and consciousness as something mysterious
30:04that can only exist inside of biological organisms like us,
30:07and somehow, therefore, can't be copied.
30:11But what's given us the whole AI revolution, right,
30:14the idea that we can't be copied, we can't be copied,
30:17the whole AI revolution, right, the idea that no,
30:20intelligence and probably consciousness too is just information processing,
30:24and it's just the information processing that really matters.
30:27Perhaps an alien would be able to download its consciousness into some sort of computer
30:33and travel as a disembodied consciousness.
30:38In this state, you'd be essentially immortal.
30:41So it's possible an advanced species could find ways to face the challenges of first contact.
30:50But if an alien civilization is out there, and more advanced than us,
30:55could there be an even bigger issue at play?
30:59Maybe the reason that intelligent aliens haven't ever come to the Earth to visit us is
31:06maybe we're just not that interesting.
31:07Is the biggest barrier for first contact the fact that aliens don't actually want to meet us?
31:22In the movies, first contact usually leads to an alien invasion.
31:28Cities get zapped.
31:30Humanity faces annihilation.
31:34Maybe ET colon isn't such a good thing after all.
31:39Imagine if we got an intergalactic email from, you know, superioraliencivilization.org,
31:47saying, hey, we're going to show up in 30 years,
31:50and we're going to show up in 30 years.
31:51And we're going to show up in 30 years.
31:52And we're going to show up in 30 years.
31:54And we're going to show up in 30 years.
31:55And we're going to show up in 30 years.
31:57We're going to show up in 30 years.
32:00Would we just be like, oh, let's get back to watching our reality TV shows
32:04and worry about that when they get here?
32:06No, we would seriously freak out.
32:08People might freak out.
32:12But the truth is, we've been signposting our location into the cosmos for decades.
32:18The Earth has been a detectably technological world for about 100 years.
32:23We've been broadcasting signals.
32:26And yet, that apparently hasn't attracted anyone's attention.
32:31It's pretty noteworthy that none of them has shown any interest
32:35when they could have turned Earth into a parking lot if they wanted, right?
32:40Perhaps no one has redeveloped planet Earth
32:43because an advanced civilization simply doesn't want to make first contact.
32:49Frankly, if they're that intelligent, they're not going to be very interested in us.
32:53So maybe that's why they haven't bothered to make contact.
32:56And if the alien is that advanced, we're probably not very interesting to it.
33:01It's a little bit like, you know, wandering around outside and seeing ants on the sidewalk.
33:09An extraterrestrial invasion makes great science fiction.
33:13But what do we actually have on Earth that's worth all that alien effort?
33:19How realistic really are these depictions?
33:23From Hollywood.
33:25One common trope is the aliens coming to devour the human race.
33:30But the science doesn't really support this being possible.
33:34Would an alien even be able to digest the human body?
33:40When eating, enzymes in our digestive system break down molecules in food.
33:45The food we can eat, and these enzymes,
33:48are very specific to the molecules they can attack and break down.
33:52The same rules would apply to a hungry alien.
33:56To be able to digest us and for us to be nutritious for them,
34:00we'd have to have a very, very similar biochemistry
34:02to what exists on the aliens' homeworld, what their bodies have adapted to.
34:08So if it seems highly unlikely aliens would come looking for food,
34:13how about a drink?
34:15In order for life as we know it to exist, one needs liquid water.
34:20If aliens live on a barren desert planet,
34:23a water world like ours could be highly attractive.
34:28While we call ourselves the blue planet, our oceans are not unique.
34:34The universe offers far greater water resources.
34:38In our solar system, we're pretty much the same.
34:41In our solar system, we're finding that most of the liquid water
34:44exists in moons around the gas giants.
34:49We believe Jupiter's moon Europa has a layer of water ice around 15 miles thick,
34:56floating on an ocean up to 100 miles deep.
35:00This single moon may have twice as much water as all Earth's oceans combined.
35:07Europa is the water world of our solar system,
35:10not the Earth.
35:12So if you were an alien looking for water,
35:15you wouldn't bother going to a big planet like the Earth
35:19to suck it up through some kind of giant straw.
35:21You'd go to the outer solar system.
35:24You might harvest icy moons.
35:28Instead of working against the powerful gravitational pull of Earth,
35:32an alien race could draw water from Europa,
35:36where gravity is almost 10 times weaker.
35:40So what other resources have we got to offer?
35:44Maybe aliens come to strip mine the Earth's crust for metals,
35:50iron or titanium or platinum.
35:53Aliens might use these metals for exactly the same things that we do,
35:57for building spaceships, for building their technology.
36:03Such materials could be useful for any alien civilization,
36:07short on mineral resources.
36:10Problem is, a lot of our planet's metals are buried deep in the Earth's interior.
36:16When the Earth formed,
36:18the great deal of its iron sunk down into the core of our planet
36:22and took a lot of metals with it.
36:23So they're actually quite hard to mine on the Earth.
36:27An alien race would be better off prospecting
36:30for more accessible minerals situated in the asteroid belt.
36:35In the asteroid belt, there's an asteroid called Psyche,
36:38which is made up of pure iron nickel, just like the core of the Earth.
36:44Psyche provides a near 150 mile exposed strip of iron nickel.
36:50Yet another reason ET wouldn't need to bother with us.
36:55For my money, none of those reasons would draw aliens to our Earth.
37:00All these things could be found far more easily elsewhere.
37:04The possibility of first contact is beginning to sound increasingly remote.
37:09The universe throws up massive barriers,
37:12stopping us communicating with an intelligent alien race.
37:16And they might have absolutely no interest in contacting us.
37:20Unless, that is, they already have.
37:24Is it possible that there have been alien signals that we've already detected,
37:27but we didn't realize what they are?
37:29Scientists have discovered a powerful cosmic signal that they can't explain.
37:36Could this finally be first contact?
37:43July 2018.
37:46The Chime Telescope in British Columbia detected a short flash of radio energy,
37:52quicker than a blinking eye.
37:55It's called a fast radio burst.
37:58These are intensely powerful, very, very short-lived radio bursts
38:02that can be a thousand times brighter than the sun at radio wavelengths
38:06that arrive and disappear in an instant.
38:12Most fast radio bursts are one-offs, blinking into existence, then disappearing forever.
38:19But not this one.
38:21A few days later, scientists caught the flash again.
38:26The amount of energy that it takes to produce a burst like this,
38:29for us to detect it here on Earth from billions of light years, is immense.
38:34And we've run across things like this before.
38:37Exploding stars, gamma ray bursts, these are all very strange objects.
38:42But that does not explain these, because some of these fast radio bursts repeat.
38:47So whatever it is that can generate this kind of energy, it can do it more than once.
38:56Light comes in many different wavelengths.
38:59Radio waves are the longest, making them good for long-distance communications.
39:07We've used radio waves for over 100 years,
39:10from wireless radio to TV, from cell phone calls to communications with space probes.
39:18Could alien civilizations be using radio waves, but on a much larger scale?
39:24What if we already intercepted alien communications,
39:27but we just don't know it?
39:31Our radio television signals only use a very narrow band of radio spectrum.
39:37Fast radio bursts are different, and that's a problem.
39:42Here's the thing about fast radio bursts.
39:44They are emitting a broad range of wavelengths, so it's not the best way to communicate.
39:49If these are aliens, they're not very smart aliens.
39:52It turns out, broad-range wavelengths are easy to distort.
39:58There is a very thin gas out there between the stars,
40:02and when you emit radio waves, the radio waves interact with this gas.
40:06And the way they interact depends on the wavelength you're talking about.
40:11If you use a broad range of wavelengths to send a signal across interstellar space,
40:15by the time somebody receives it, it can be a little distorted and weird.
40:22If aliens are sending out radio bursts, the signal would be so degraded
40:28that by the time it reaches us, we wouldn't be able to decipher it.
40:34As a calling card, not incredibly useful.
40:40Astronomers have turned to weird natural phenomena
40:43to figure out the origin of these fast radio bursts.
40:47Like the leftovers from a massive star dying in a supernova explosion.
40:52These remnants are known as neutron stars.
40:56These weigh roughly the mass of the sun and are the size of a city,
41:00and they are formed when a massive star collapses.
41:04And a neutron star that is left behind is spinning very often,
41:09and if it has magnetic fields, it also produces beams of radiation.
41:14To create the energy of a fast radio burst,
41:17these neutron stars would need to be infants, throwing stellar tantrums.
41:23Neutron stars, when they are born, might be much more powerful in their emission.
41:28And so perhaps we're witnessing newly born neutron stars that are only decades old,
41:33and at their youth, they are so bright that we can see them in the sky.
41:40And at their youth, they are so bright that we can see them all the way to the edge of the universe.
41:47Whether these mysterious bursts really are aliens trying to say hello,
41:52or just a natural phenomenon, this isn't first contact.
41:57Just yet.
41:58I want to be careful here, right?
42:00I'm not a naysayer.
42:01I'm not going to poo-poo aliens.
42:03But, you know, let's go through the other things first,
42:05because the universe is filled with weird stuff, and let's see what that is.
42:09And if we eliminate all those, and all that's left is aliens, yeah, let's talk.
42:14If extraterrestrial species really are out there,
42:18our universe makes it extremely difficult to contact them.
42:24But in spite of all the obstacles, maybe there is still hope.
42:30We once thought there could be 10,000 intelligent civilizations in the Milky Way alone.
42:36Now we know our cosmos is filled with planets, just waiting to be found.
42:42Our technology is evolving.
42:45Searches are expanding.
42:48The truth is, when it comes to first contact, we're just getting started.
42:56I'd love for tomorrow morning some sort of interstellar tweet to be beamed at the Earth,
43:02and we would then realize that we are not alone.
43:06I'm ready to celebrate.
43:09Here we have already a champagne on ice to pop when they find it.
43:15Scientists really do hope we find evidence of extraterrestrial life someday.
43:20We have observatories and satellites that look at the sky all day, all night, every day.
43:28The discovery of alien life would simultaneously be, in a way,
43:32unsurprising, and yet the greatest discovery in all of human history.
43:36Even if life is really, really rare, the universe is really, really big,
43:40and so there could be countless alien civilizations out there.
43:43But the actual discovery or confirmation of that?
43:46I can think of no greater scientific discovery.
43:49It would quite literally change our entire civilization.