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00:00The Earth is in danger. Future cosmic events will blast, burn, or rip us to shreds.
00:10The universe is incredibly violent. There are huge events going on all the time.
00:16One day, life on Earth will become impossible.
00:19There will be disasters in the future, and one of them will destroy us.
00:25To save mankind, we'll need to find other places to call home.
00:31It really has to be our destiny to move off the Earth if we are going to survive. It's as simple as that.
00:38We need an insurance policy.
00:41We must do it, and we must get started now.
00:43We'll need a lifeboat and new homes amongst the stars.
00:49This is how we can do it.
00:54The Earth. As far as we know, it's the only home to life in the universe.
01:13Earth is such an ideal environment for life.
01:17Everything about our bodies, our biology, our chemistry evolved here on Earth.
01:23We literally are on the perfect spaceship.
01:28But our perfect spaceship is hurtling through a cosmic minefield.
01:35Every 30 million years or so, a natural or cosmic disaster hits the Earth so hard that millions of creatures go extinct.
01:46Extinction events tend to kill off the dominant species.
01:54And right now, that's us.
01:59It's certainly true that in an extinction event, it's the large and powerful that get wiped out. They go.
02:06So you know that if there's an extinction event on Earth, we humans are vulnerable.
02:10We're in the category of large and powerful.
02:13The only way for humankind to survive global extinction is to spread our genes to more than one planet.
02:21We have no choice. It's a law of evolution, geology, and physics.
02:27The alternative is death and extinction.
02:32We'll have to build a giant spacecraft capable of crossing interstellar space.
02:38You will essentially need a new Noah's Ark.
02:42But it's going to be a space ark, and it has to encapsulate all of the diversity of Earth inside this one ship.
02:50The space ark will have to be huge, big enough to house the thousands of people needed to create a healthy planet.
02:59Too massive to construct on Earth, the giant craft will have to be built in space, far from the pull of Earth's gravity.
03:07But building a shipyard in the sky is no small challenge.
03:14NASA is tackling the challenge of building a giant spacecraft capable of crossing interstellar space.
03:21Building a shipyard in the sky is no small challenge.
03:27NASA is tackling it head-on with a new generation of heavy lift rockets called SLS.
03:37I see the SLS as a capability that's going to allow us to put an industrial base between the Earth and the Moon.
03:43After we do that, and we're out there routinely working in space, that's when we'll assemble the craft that will take us to the stars.
03:52Les Johnson's job is to plan the future of space exploration.
03:59Today, he's observing a test firing of a 1-20th scale model of SLS.
04:05When the real deal takes off in 2032, the SLS will become the most powerful rocket ever launched.
04:15The SLS is big. It's going to give us a capability to take lots of stuff up with each launch.
04:20And it can be big volume.
04:21And you could potentially launch three of these big rockets versus perhaps 15 or 20 of the other rockets we have available today to get the same amount of material out into space.
04:32Les envisions SLS rockets taking prefabricated units beyond Earth's orbit, where space engineers will assemble them in a colossal industrial workshop.
04:44Miners will then fly out to different bodies in the solar system to collect the raw materials needed to build the space ark.
04:53We'll have factories on the Moon, and perhaps even beyond that, on giant rocks inside the asteroid belt.
05:02Asteroids have a fraction of Earth's gravity.
05:05Here, it will be much easier to build massive sections and lift them to the ark as it begins to take shape.
05:14The inner solar system will provide all we need to make the giant superstructure of the space ark.
05:23But to colonize a different world will require a propulsion system faster than anything we've ever built before.
05:32Space is huge. Our solar system is huge. Even to get to Mars would take almost a year.
05:36But that's nothing compared to exploring the distance between stars.
05:42The nearest stars to our sun are several light years away.
05:45Even light, the fastest thing in the universe, takes several years to get there.
05:50The sun's closest neighbor is a triple star system called Alpha Centauri.
05:57A spaceship burning conventional fuel would take tens of thousands of years to get there.
06:03The crew would die of old age long before the ship arrived.
06:08So what fuel to use?
06:13Science fiction appears to have the solution, but it sounds too good to be true.
06:20Every Trekkie in their heart of hearts knows that it's antimatter.
06:23Antimatter is the fuel for an interstellar ship.
06:31Antimatter is real.
06:33We create a few atoms of antimatter every year in high-energy particle colliders.
06:40It's a mirror image of all the matter that we see around us.
06:44And it has an explosive property that would make it the most efficient rocket fuel ever created.
06:51Here's the cool thing about antimatter.
06:53When antimatter and matter meet, they annihilate each other.
06:59That means that the matter ceases to exist.
07:04They convert into pure energy.
07:08It's a 100% efficient process.
07:12Scientists have calculated that a rocket powered by antimatter could reach 15% of the speed of light.
07:20That's fast enough to get to the moon in eight and a half seconds.
07:25We will have almost unlimited power. We could travel anywhere in the universe we wanted to.
07:31Our space ark could reach Alpha Centauri in just over 28 years.
07:37Well within the lifetime of its human payload.
07:41Now this sounds like a great idea, right?
07:43Let's get together a lot of antimatter. Let's create some antimatter.
07:46And let's combine it with regular matter and we have this outstanding energy source.
07:51But antimatter has a huge problem.
07:54And that is exactly what its advantage is.
07:57When it meets matter, it's going to annihilate and create energy.
08:02Fill a conventional fuel tank with a single pound of antimatter.
08:06And you'll get an explosion more powerful than a thousand Hiroshima bombs.
08:13Antimatter is just too hot to handle.
08:17We need a reliable energy source that can power our starships for years at a time.
08:24And there are only a few candidates that can do this.
08:26Among them, fusion power, harnessing the power of the sun itself.
08:36In the sun's hot, dense core, hydrogen atoms collide.
08:43Smashing into each other with such force, they fuse, releasing enormous amounts of energy.
08:49This is nuclear fusion.
08:56What we want to do in space travel is miniaturize it and put it in a spacecraft
09:00and use that as your power system and as your propulsion system for deep space exploration.
09:09A fusion rocket is still two-thirds the speed of one powered by antimatter.
09:14And best of all, its fuel, hydrogen gas, can be found in vast clouds between stars.
09:22It would simply automatically fire in outer space using interstellar gas.
09:28And in principle, it would never require refueling.
09:32Our fusion-powered space ark heads for its first target, Alpha Centauri,
09:38at 10% the speed of light.
09:41It will take 42 years to complete the journey,
09:45and its precious load of human pioneers must be delivered safe and well.
09:51But the crossing may be deadly.
09:54Our violent cosmos has a million ways to kill.
10:09A giant space ark fires its fusion rockets.
10:14Inside the ship are thousands of human volunteers.
10:18They're on a one-way mission to colonize a distant planet.
10:23We will one day have to make this journey.
10:28It's inevitable that we go off planet.
10:30I think we're going to have to do it to survive as a species.
10:33The ark's first target is the closest star system to the sun, Alpha Centauri.
10:39And the journey will be long, around 40 years.
10:43Keeping the crew fit and healthy is imperative.
10:47But it won't be easy.
10:49A lot of things happen to the human body when you go into space.
10:53The moment you become weightless, you instantly get kind of a shock.
10:56You get dizzy. That can make you feel nauseous.
11:00Leroy Chao spent six months on the International Space Station,
11:04long enough to experience the damaging effects of zero gravity.
11:10Your bones aren't feeling any impact, so your body decides it doesn't need bones anymore,
11:14and it'll begin to demineralize your bones.
11:16And it'll begin to demineralize your skin.
11:18It'll begin to demineralize your skin.
11:20It'll begin to demineralize your skin.
11:22And it'll begin to demineralize your skin.
11:24And it'll begin to demineralize your skin.
11:26And then your muscles, through disuse, of course, they'll naturally atrophy very quickly.
11:33The human body evolved to live with Earth's gravity.
11:37Without it, bones lose 2% of their mass for every month spent in space.
11:44The cardiovascular system suffers too.
11:47Body fluids pool.
11:50Heart rates and blood pressures rise.
11:54Resistance training helps reduce the symptoms.
11:58We're scheduled for two hours of exercise a day on the space station
12:01to keep our cardiovascular system fit, to keep our muscles and our bones fit.
12:06Exercise can hold off the dangerous wasting process.
12:10But a 42-year journey to Alpha Centauri without gravity would be fatal.
12:17Obviously, we need a permanent solution to weightlessness.
12:21There's nothing to prevent us in the near future from creating artificial gravity.
12:30Centrifugal force is the answer.
12:34It's the force that sticks daredevil bikers to vertical walls
12:38and keeps thrill-seekers glued to their seats in theme parks.
12:44Rotation produces this outward force,
12:47and it would be relatively simple to create in a spaceship.
12:53Why do we need centrifugal force?
12:55Well, it's the force of gravity.
12:57And it would be relatively simple to create in a spaceship.
13:03By rotating a space capsule,
13:06it means that the astronauts inside will experience artificial gravity.
13:12Spinning the living quarters at just the right speed
13:15will hold off bone and muscle wasting.
13:19But low gravity is the least of the dangers our pioneers will face
13:24as they journey deep into space.
13:27Radiation is probably the biggest challenge.
13:30We're going to be exposed to much harsher levels, much higher levels of radiation.
13:35The sun's surface shoots out a constant stream of dangerous charged particles,
13:41protons and electrons, traveling at close to a million miles per hour.
13:47These things will break your DNA,
13:49they'll cause cancer,
13:51and they will kill you.
13:54The Earth's magnusphere and the atmosphere above our heads
13:58protects us from the worst of this radiation.
14:01But far from the Earth, the pioneers will face radiation head-on.
14:07That really is the biggest technical barrier
14:10to mankind sending people out farther and deeper into space.
14:14It's not propulsion, it's not computers or navigation,
14:17it's how do we keep people healthy.
14:20Beyond the boundary of our solar system,
14:22the radiation threat gets worse.
14:25Charged particles come at you even faster.
14:29In some cases, there are single protons
14:32that actually pack as much of a punch
14:35as a hundred mile an hour fastball.
14:38These cosmic rays are joined by an even deadlier force,
14:42gamma rays spewed out by violent cosmic events.
14:48All the cosmic phenomena, from stars exploding
14:54to black holes eating up large parts of galaxies,
15:00produce radiation and particles that are incredibly energetic.
15:06You've never seen these particles before,
15:08your body's not adapted to them.
15:10And they come at you all the time,
15:12and they're very high energy.
15:15Galactic cosmic radiation will rip through the cells
15:19of our human cargo, liquefying their bodies.
15:28The only hope is to somehow shield the spacecraft.
15:33In science fiction, starships create a protective magnetic bubble
15:37similar to the magnetic field that protects the Earth.
15:42But a deflector shield would take a huge amount of energy to sustain.
15:47And, like any electrical device, it would be prone to failure.
15:52The safest option is to go low-tech,
15:55coating the ship with a thick layer of physical shielding.
16:00Shielding is not a simple problem.
16:01It's not just a matter of bringing a bunch of lead or anything like that.
16:04In fact, what you find is that if you do something like that,
16:07it absorbs the radiation,
16:09and then it re-emits it in a more dangerous form.
16:16Metals won't work, but scientists have come up with a brilliant alternative.
16:24In fact, one of the best shields from cosmic rays is something simple, water.
16:30And it's actually something you need to bring with you
16:32as you venture into interstellar space.
16:35The hydrogen atoms in water absorb high-energy particles,
16:40and in sufficient volume, water can also block gamma rays.
16:46The living quarters of the ark will have a thick outer skin
16:49filled with the ship's water,
16:51and outside that, a second skin
16:54filled with the ship's hydrogen supply for its fusion engines.
17:00Our astronauts are now safe from radiation sickness,
17:04and with artificial gravity, their bodies will stay strong.
17:10The deadliest threat now is their crewmates.
17:24A cosmic catastrophe will one day wipe us from the face of the Earth.
17:29To save mankind, we'll need to escape to the stars
17:32in a giant space ark in search of new homes.
17:37Its precious human cargo will be kept in top physical condition
17:42with artificial gravity and hydrogen-rich shielding.
17:47But what about their mental health?
17:50One of the biggest challenges for people in space are the people.
17:53Taking people, putting them in a tin can,
17:55in an incredibly dangerous environment,
17:57having them get along with each other for months or years
18:00and stay alive through the journey
18:03is going to be an enormous challenge.
18:06We know when people go on submarines
18:08that they have to be very carefully tested,
18:10and those submarines go out for missions
18:13that certainly don't last years.
18:16We can't start a new civilization
18:18with a crew ravaged by cosmic boredom,
18:21infighting and mental illness.
18:24It would help if the entire crew were unconscious.
18:29One possibility, which, of course, again,
18:31is a possibility in science fiction,
18:33is to have people be asleep during most of it.
18:37Could you put people into an induced coma
18:39and then wake them up in time to go do their science mission?
18:42It might be an easier thing to do than to say,
18:45well, now you just sit still for the next ten years.
18:49The closest we come to surviving on Mars
18:52The closest we come to suspended animation in today's world
18:56is storing human embryos in liquid nitrogen.
19:00But could we really save the human race
19:03with test tube babies?
19:06Because of the enormous hurdles facing space travel,
19:09some people have advanced the idea,
19:11well, why do we have to send humans into outer space?
19:15Why not send embryos or sperm and egg cells?
19:19In theory, we could transport frozen embryos
19:22across the vast distances of space,
19:25sidestepping the need for food or complex life support systems.
19:30They could withstand the rigors of space travel and weightlessness,
19:34but how would they be socialized?
19:36You put a baby in a single place alone,
19:39they don't know how to read, they wouldn't survive.
19:41In fact, we're very dependent. We are social beings.
19:45We would have to develop intelligent robots
19:48to hatch the embryos and then teach them to be human.
19:54It's conceivable that perhaps a hundred years into the future,
19:57we will have robot nannies
19:59that can incorporate the laws of social interaction.
20:04Could a robot really raise a child?
20:07Or in our rush to save humanity,
20:10will we end up forgetting what it means to be human?
20:15Raising human embryos may be too much of a gamble,
20:19so could we freeze adults instead without affecting their health?
20:24It's a much bigger challenge, but nature has almost solved it.
20:30A lot of animals on Earth will go into suspended animation
20:33or hibernation when conditions get bad,
20:36and in some cases, they can stay that way for a long time.
20:41The Alaskan wood frog survives whole winters frozen in ice.
20:49At sub-zero temperatures,
20:51its metabolism slows and effectively shuts down.
21:01When the ice thaws, the frogs reanimate
21:06and hop off as though nothing happened.
21:10Could humans ever do the same thing?
21:14When you freeze somebody alive,
21:17there are ice crystals which form which begin to expand,
21:20rupturing the cells and turn cells into mush.
21:26So how do the frogs survive the deep freeze?
21:31The answer is they have an antifreeze in their blood,
21:34and that is glucose.
21:37So even though their surrounding environment is solid ice,
21:41inside their cells are liquid.
21:45The problem with humans is that amount of antifreeze would kill us.
21:54Deep freezing humans isn't going to work,
21:58but we may not have to chill that low to hibernate.
22:04In Pittsburgh, surgeons have developed a groundbreaking technique
22:09using chilled saline solution
22:11to rapidly lower their patients' body temperature
22:14to just a few degrees above freezing.
22:17At this temperature, cellular activity stops.
22:25Just like the wood frogs,
22:27the patients are effectively in suspended animation.
22:35In operating rooms, we can cool people down
22:37and put them in an artificial coma for a while.
22:40So it sounds good, and like everything else, it's worth exploring.
22:45Whether through freezing embryos
22:47or putting adults into a cold, deep sleep,
22:51suspended animation may be the best bet
22:54for keeping our precious human cargo alive
22:57on the long trip to Alpha Centauri.
23:01But what if they get there
23:03and there's no place like home?
23:15A spaceship filled with human volunteers
23:18approaches the triple star system, Alpha Centauri.
23:24The crew hopes to find the first of many new worlds
23:27for mankind to call home.
23:30But which, if any, of these stars
23:33will have the right kind of planets?
23:36We want to find a home that's as similar to Earth
23:39as we can possibly find,
23:41because we're fine-tuned for this planet.
23:43We're fine-tuned for this surface gravity.
23:45We're fine-tuned for this atmosphere,
23:47this radiation environment.
23:50The stars fill the spacecraft's displays,
23:53and soon the outline of planets will be visible.
23:58The brightest of the trio is Alpha Centauri A.
24:03It's slightly bigger and slightly brighter than our sun,
24:07throwing more heat into the space around it.
24:13Its smaller, cooler neighbor, Alpha Centauri B,
24:17lies so close, gravity pulls the two stars
24:21into a wide, slow binary orbit,
24:25rotating once every 80 years.
24:29That's bad news for our pioneers.
24:36Planets rarely form stable orbits
24:39around wide binary systems,
24:42so there's little chance of finding a place to settle here.
24:50But the third star in the trio offers hope.
24:55Proxima Centauri is a red dwarf, or M-dwarf star,
25:00too small and dim to be seen from Earth with the naked eye.
25:04Yet astronomers have found Earth-like planets
25:07around this type of star throughout the Milky Way galaxy.
25:14We're finding that red dwarfs are ideal in a number of ways.
25:18In particular, they seem to be absolutely teeming
25:21with Earth-sized planets.
25:23Astronomers have already discovered
25:25one Earth-sized planet around Proxima Centauri.
25:29It orbits too close to the star to sustain human life,
25:33but there's a good chance it may have a sister planet that can.
25:37If we were to look up into the night sky
25:40and look at the nearest M-dwarf star, say Proxima Centauri,
25:44I would expect to see a system of three to six very small planets
25:50in extremely compact orbits,
25:52meaning orbital periods of only a few days.
25:59Proxima Centauri may well be home to a rocky planet ideal for life,
26:04with a thick atmosphere, warm liquid oceans,
26:08and a strong magnetosphere to protect it.
26:12A perfect refuge for mankind to set up our first new home.
26:18But what if we find a planet that's a little less than perfect?
26:24Too cold, perhaps, with too much gravity,
26:28or maybe the wrong kind of atmosphere?
26:33We are genetically programmed to thrive on the planet Earth
26:36with a specific amount of oxygen,
26:38a specific amount of carbon dioxide in a certain weight.
26:42However, once we land on a distant planet,
26:45we're going to have to change our bodies
26:47so that we can thrive in different environments.
26:51We're going to have to be able to engineer ourselves.
26:53We're going to have to be able to evolve ourselves rapidly.
26:57That may mean taking genes from other life forms
26:59to give ourselves some property that we need.
27:02That might just be the best solution.
27:05Scientists have searched high and low
27:07to find the ultimate genes for survival in space.
27:11And they may have found them in a creature no bigger than a grain of sand.
27:20Right now at NASA, we're doing experiments
27:22on tiny little animals called tardigrades.
27:26Tardigrades are tough.
27:28They can survive a range of temperatures
27:30from freezing to boiling point.
27:32They can live without food or water for a decade or more.
27:36And, crucially, when their DNA gets damaged by radiation,
27:41it repairs itself.
27:43A tiny little microscopic thing can survive more radiation
27:46than would kill a herd of elephants.
27:48Somehow the DNA knows how to repair itself.
27:51We're trying to figure out how we could modify human DNA
27:54to do the same thing.
27:57One day, DNA from these tiny creatures
28:00may allow us to set foot on a planet
28:03battered by radiation from its parent star.
28:07And genetic tinkering may hold the key to much more,
28:11allowing us to colonize a multitude of hostile alien worlds.
28:18If the planet has a larger gravitational field,
28:21we may have to increase the strength of our bones
28:24and the strength of our muscles
28:26so we don't collapse every time we walk
28:28on the surface of a large planet.
28:35We could even adapt to different atmospheres.
28:39If we were to arrive on a planet that has a different oxygen level,
28:42different carbon dioxide level,
28:44we may have to alter our metabolism rate.
28:48We are beginning to take control of our own evolution.
28:51We are designing gene therapies.
28:53We are finding ways to modify our biology.
28:56There's a wonderful chance here
28:58to really take control of our own destiny
29:01and drive ourselves to the stars.
29:05Who knows what the future astronaut will look like,
29:07but I strongly suspect that they won't look like you or me.
29:14If we find habitable worlds around Proxima Centauri,
29:18a shuttle full of genetically altered pioneers
29:21will be dispatched to the surface
29:23in order to start a new human civilization.
29:28But this is just the first stage of a much bigger plan.
29:32We must continue to get more worlds
29:35traveling deeper and faster into the Milky Way.
29:54One day, a cosmic event will hit the Earth so hard
30:00it will wipe out every human on the planet.
30:03If we're going to live on indefinitely into the future,
30:06human beings are going to have to leave planet Earth.
30:09Our only hope is to build a space ark
30:12that will take us to new worlds around distant stars.
30:17Life is fragile, and that's why I believe
30:20we should be at least a two-planet species.
30:25The first target was by far the easiest.
30:32It took 42 years for our space ark to reach Proxima Centauri
30:38using fusion-powered engines.
30:41But now the ark must move on to find even more distant worlds.
30:47The crew can be held in suspended animation,
30:50but they'll still deteriorate with each passing year.
30:54We need to go faster, closer to the speed of light.
30:59But there's a small problem.
31:01The laws of physics.
31:04What Albert Einstein figured out is that
31:06if you start traveling near the speed of light,
31:09things get a little bizarre.
31:12As you get near the speed of light,
31:15As you get near the speed of light, your mass increases,
31:18meaning that you have to have more energy to keep you going.
31:22By the time you get to near the speed of light,
31:24all the fuel turns into increasing the mass.
31:27So all the fuel that before would have increased the speed a lot
31:30doesn't increase the speed at all, it just increases the mass.
31:33Eventually, you don't speed up at all,
31:35you just get heavier and heavier as you shoot out propellant.
31:40Physics won't let us travel through space
31:42at the kind of speeds we need.
31:45But there's a loophole that may allow us to cut through hyperspace
31:49and reach distant planets a whole lot faster.
31:53Einstein showed us that space itself
31:55can expand faster than the speed of light.
31:58Space and time is not nothing.
32:01There's a substance to it, a fabric, if you will.
32:04And you can stretch it, and you can bend it.
32:08In science fiction, galactic travelers manipulate
32:11the fabric of space-time using warp drives,
32:15crossing the cosmos in minutes, not millennia.
32:20Imagine you're in a room and there's a carpet,
32:22and you need to get to the other side of the room.
32:24One thing you can do is you can take the carpet and fold it up
32:28and bring all of it close to you, then step over the folded carpet
32:32and then let it unfold behind you,
32:34and now you've moved across the room really quickly.
32:36It would take a colossal amount of energy
32:39to warp all the space between you and your destination,
32:43far more than we could ever hope to generate.
32:46But modern physics says the warp drive is possible
32:50if you only warp the space surrounding the ship.
32:54So we know that space expands, and space can also contract.
32:57So if you have a ship and you contract space in front of you
33:01and expand space behind you, you can create a warp bubble,
33:05and it's been theoretically shown that you can move
33:08to up to 10 times the speed of light.
33:12This new generation warp drive creates a wave in space-time
33:17that travels faster than the speed of light,
33:20carrying the ship along with it like a surfer riding a wave.
33:25Mathematicians have looked at the numbers,
33:28and a new generation warp drive would work on paper.
33:32Now NASA wants to try it in the lab.
33:38Is it impossible or is it plausible?
33:40I think we're in that category of starting to think about,
33:43we've got some plausibilities here.
33:45Let's go see if we can't do some scientific efforts
33:48and see validation of the math and physics.
33:52Harold White is planning a future experiment
33:55to see if he can warp space on a microscopic scale.
33:59He hopes to concentrate energy in a single point in space
34:03and then measure the progress of laser light crossing it.
34:07If the light completes the journey faster than normal,
34:11he'll have succeeded in warping space-time.
34:16Everybody always asks me about when's this going to be ready
34:18to bolt onto a spacecraft,
34:20and there's a lot of science we need to do first.
34:23We're only just now starting to look into this.
34:25We don't know if it's going to work or not.
34:27We might as well figure it out.
34:28If it does, boom.
34:29And if it doesn't, well, we've learned something interesting
34:31about math and science and the way the universe works.
34:34A warp drive would fire us to Proxima Centauri
34:38in just five months
34:41and to the 50 stars beyond in just a few years.
34:46But that's still just our galactic backyard.
34:51A warp trip to the far side of the Milky Way
34:54would take 10,000 years
34:57and a trip beyond it to the closest galaxies
35:00hundreds of thousands of years.
35:03Even a warp drive seems pitifully slow
35:07on the scale of the universe.
35:09But there is one last hope.
35:14Another way to go faster than the speed of light
35:17is to drill a hole in the fabric of space and time.
35:24This is called a wormhole.
35:30A wormhole is a theoretical tunnel,
35:33a rip through space-time connecting two distant points.
35:38It's created by huge concentrations of mass
35:41warping space-time.
35:46Think of Alice's looking glass.
35:48You put your hand through the looking glass
35:50and your hand winds up on the other side of the galaxy.
35:56If our spacecraft could enter this cosmic shortcut,
36:00we could jump thousands of light years in an instant.
36:04The only trouble is astronomers have never seen one
36:08and attempting to make one would be fatal.
36:12To bend space at either mouth of the wormhole to make a tunnel,
36:16you have to produce huge amounts of mass.
36:18That mass is attractive.
36:19And we can prove that if normal mass is all you have,
36:23that either end of the wormhole will collapse to form a black hole
36:28in a time scale shorter than it would take you to go through the wormhole.
36:35I don't think wormholes are ever going to work
36:37as a way of transportation.
36:39But you know what, typically those people who said
36:41that something couldn't happen in science turned out to be wrong.
36:45So I take that back.
36:47It's unlikely, but it may happen.
36:50Warp drives and wormholes are distant dreams.
36:54For now, fusion is the likely fuel to take us to the stars.
36:58But it may take millions of years for a giant space ark
37:02to colonize enough planets to guarantee our survival.
37:07The only way to go faster with fusion is to make our space ark much smaller.
37:13Small in fact, there'd be no room for people inside.
37:17So is that really game over?
37:20Or could we save humanity without humans?
37:32Not so long ago, astronomers weren't sure
37:35if the stars they saw in the night sky had planets orbiting them.
37:40Perhaps the sun was unique, and the Earth alone in the Milky Way.
37:47But over the last 20 years, we've revealed a mind-blowing truth.
37:53It seems that a large fraction of stars in the galaxy have planets.
37:58And in fact, many of those stars have multiple planets.
38:02These exoplanets range in size from gas giants bigger than Jupiter
38:08to rocky worlds like Earth.
38:10And they're everywhere we look.
38:13Our planet Earth is not unique.
38:16It's not even rare.
38:18There are tons, hordes, flocks, if you will,
38:22of other Earth-like planets out there fluttering around the other stars.
38:27Some stars probably have multiple Earths orbiting them.
38:30That's how common Earth-like planets are.
38:34Look into the night sky and count five stars.
38:38One of those stars has an Earth-sized planet around it,
38:41maybe our next home.
38:44Apply what we've found to the rest of the Milky Way,
38:47and the results are staggering.
38:51Around sun-like stars, up to 11 billion warm, wet Earths.
38:57Around red dwarf stars, another 22 billion.
39:02And gas giant exoplanets may be home to tens of billions more potential Earths
39:08in the form of habitable exomoons.
39:12There are many Earth-like planets that we're going to have as options of places to go,
39:17almost sort of a menu spread out in front of us.
39:20Clearly, locating new Earths isn't the problem.
39:23The problem is getting there.
39:26The universe is actually kind of tantalizing us.
39:28Earth-like planets are common. They're all over the place.
39:31But they're so far away that with our current technology,
39:34we cannot imagine how to get there.
39:38A giant space ark powered by fusion engines
39:41and filled with thousands of human volunteers
39:44should allow us to colonize habitable worlds near our sun.
39:49But to go beyond that, to the far reaches of the Milky Way,
39:53we need Plan B.
39:57One radical solution would be to send miniature robots instead of humans.
40:05When I think about how much we're learning about the human brain and how it works,
40:09and there's still a long way to go,
40:11it does seem to me fairly inevitable that someday we'll be able to put all of ourselves into a robot.
40:17Now you might say, that's so sad because we want to get humans on those planets.
40:21Well, one, if you really want to think science fiction,
40:24why not ultimately take a machine that can build a human at the other end?
40:30Plants spread their genes by sowing huge numbers of tiny mobile seeds into the wind.
40:36Many seeds will be lost to the elements,
40:40but those that find warm, wet Earth come to life.
40:47Imagine firing tiny nanorobots into space like seeds,
40:52with human genomes burned into their hard drives.
40:59If they fall through the atmosphere of a wet, warm planet suitable for humans,
41:04they spring into action.
41:06They'll land and make shelters from the materials they find on the planet,
41:11and somehow also make the humans to live inside them.
41:17Maybe we'll send thousands of these nano-ships, as they're called,
41:21maybe millions of them, like seeds, to a nearby star,
41:25hoping that just a few of them, a few of them actually reach their destination.
41:32The technology to create a human from scratch is clearly a long way off,
41:37but it raises intriguing philosophical questions.
41:42Why should we only save humans?
41:45There are 8.7 million species on Earth.
41:49Aren't they all worth saving?
41:53And if we can't send all life on Earth,
41:56why not simply send bacteria to distant worlds,
42:00and leave evolution to do the rest?
42:03And who knows?
42:05Maybe an alien species has already done that on the Earth.
42:08Maybe in your backyard there's a nano-ship from a distant star system,
42:14and you would never know.
42:17Wherever we end up, whatever we become,
42:21the time to start planning for our survival is now.
42:26The human imagination is taking us in some truly amazing paths,
42:31and they may lead us to find a way where interstellar travel could really work.
42:39Our fate is in many ways in our own hands.
42:42We're not dinosaurs.
42:44We don't have a space program. We're smart.
42:47If we have colonies on other planets, the Earth can be wiped out,
42:51and humanity won't be.
42:53In that sense, our future, our long-term future, that's in our own hands.