Exploring Mysteries of the Universe | One Strange Rock MEGA Episode | National Geographic

WILL SMITH: When I was little, my grandmother gave me an old compass. She wanted me to know where I was going. I was always much more intrigued by where we came from. I mean, I knew she was from Pittsburgh, but before that, her grandmother and her grandmother's grandmother, where did they come from? You go back far enough and everyone, every living thing, we all come from the same place, a moment when a dead rock came to life. Only a few of us have been able to see just how extraordinary life is. MAN (over radio): Ignition and lift-off. WILL SMITH: Eight astronauts, with over 1,000 days in space between them, can tell us how being up there helped them to truly understand what goes on down here. MIKE: I look down and I can see where we came from. This living, breathing bubble of life in the blackness of space. CHRIS: It's hard to imagine anywhere else where everything could have fallen into place so magically. MAE: We're so used to life that we start to think of life as being really simple and easy to do. It's not. -We may never know exactly how life got started, but we do know it was a strange brew. A dash of magical liquid... A sprinkle of stardust... And a crackle of energy. Mixed together in a big bubbling cauldron to make our rock come alive. Mae Jemison sees life differently from most of us... And not just because she's an astronaut. MAE (over radio): Go on my mark, three, two, one... Okay Mae, we copy. WILL SMITH: She's also a doctor. She's spent her life studying life. Houston now controlling. Houston, Endeavour switching into roll. Roger roll Endeavour. -At an age when I was just running around writing rhymes in Philly, she was pondering life's biggest questions. MAE: As a child I was fascinated by the question, who am I? What am I? I remember once when we were driving from Chicago to Alabama we stopped on the side of the road and I looked up and there was this incredibly star-studded sky. It just made the whole universe very magical. And 30 years later, I had a ringside seat to the stars. When I was in space, I felt an incredible connection to the rest of the universe. And it's true. We're made of the stuff of stars. The carbon, the nitrogen, the oxygen, the elements that are the key components to our body were actually generated inside of stars that exploded. All of the stardust scattered across the universe, clumping together into rocks to form planets like ours. And the great mystery of Genesis is about how stardust came to life. -You, me, the dog, we're all made of the same dead dust that built the planet. It's just mixed up different. The big mystery is, what's the mixer? -Lechuguilla is probably one of the most difficult places to visit on Earth. When you're deep in Lechuguilla you're more than 1000 feet underground. Lechuguilla cave is almost 150 miles long which makes it one of the most complex maze caves in the world. BARTON: The trail's down here. It's a big pretty big drop-off into this room. Got it. That's amazing. Absolutely. Most of these formations are a couple of hundred thousand years old. We'd better not touch anything. -Yeah, let's get through without touching anything. WILL SMITH: You'd imagine these deep dark caves to be lifeless. There's no energy from the sun here, but the cave walls are not as dead as they seem. If you were to put on special glasses... You'd see this kaleidoscope of organisms, living in the caves. Billions of bacteria on every surface you look at. Lechuguilla is cut off from the surface. But there is something above all else that is essential for life. Water. It takes up to 10,000 years for water to work from the surface into the lake. You take the water out of the equation and you have no bacteria in the cave. MAE: Water is required for life as we know it here on Earth. One of the important things you learn in medicine is that bacteria are made up of just one cell. And cells are the basic units of life. Tiny bubbles or membranes filled with water. Floating around this solution, we've got the ingredients of life. Yet, it all depends on water. And when looking at our planet from space, I was struck by just how much water there is. CHRIS: It is definitely the blue planet. These bodies of water are massive around the Earth. MIKE: You're over the ocean, ocean, ocean, and then you hit a continent like Africa, like, ooh, Africa, big continent. In just a couple of minutes it's gone and you're over the ocean again. MAE: Looking at the Nile Delta from space, you can see how important water is, because all along the Nile river is this thin beautiful green strip of life. JERRY: That H2O is magic, and so when you're looking for life, the key is to find water. -We can last way longer without eating than we can without drinking. Food gives us energy. What does water give us? Turns out that plain old H2O is the universal champ at one crucial thing. (inaudible). -We've come here to Angel Falls to climb this huge overhang. biggest in the world. You just feel like you're flying when you're hanging from the wall. The sound of the waterfall is like a constant storm. (raging water) Climbing Angel Falls is very dangerous. -I want to keep climbing. -You want to take the lead? -Yeah. Of course. -Where the rock has been more exposed to the water... The Rock is crumbly. -It's very sandy, so I'm going to put one protection here. Got to be really careful in this, you know. -And the other hand, where there is no water at all, you can see the rock is completely different. It's extremely hard. -Are you going to climb (inaudible)? -Yeah, I will try. -When you get to see this landscape from above... You can see how the water is a big destroyer in a way. It dissolves the rocks. It continues, the flow of water, for millions of years, like these incredible islands in the sky. MAE: Water has special properties. You know the same water we drink can dissolve almost anything. It will even dissolve rock over time. So that means lots of different molecules can be mixed together in it. And interact with one another, making something new. And that's what makes Earth so special. With all the liquid water we have, our planet's like some type of giant chemistry lab. Water takes dust from the stars, breaks it down and shakes it up. But life isn't going to bubble up just because you stirred up some muddy stardust. If you want to brew the soup of life, you need to kick it up a notch. WILL SMITH: If you want to make stardust into life... There's a bit more to it than, just add water. A recipe is more than a list of ingredients. It also tells you how to put them all together. MAE: Imagine a big pot of all these ingredients, you throw them in, but if you throw in the celery, tomatoes and the pepper, you're not gonna get a spaghetti sauce, unless you add some heat. -I usually start my day with a hit of caffeine, but Lee Koon Yau, his job gives him all the jolt he needs. (thunder) -Lee is up top to check the lightning conductor. (singing in native language) He's testing it to make sure it conducts electricity right down to the ground. WILL SMITH: You and I may only see lightning a few times a year, but the Earth is constantly crackling with energy. To see it, you have to go way higher than a skyscraper. MAE: Viewed from space, the Earth is dynamic. It's full of energy. I remember seeing these big flashes of light that sort of come through the clouds. JERRY: You know, the lightning just propagates literally for thousands of miles across the surface of the Earth. NICOLE: It looks like its nervous system spreading across the planet. MIKE: They're spectacular. They almost seem to be communicating to each other. MAE: There are over 100 lightning strikes per second. That's eight million a day. And at the start of our planet, billions of years ago, there was even more energy on display. That's what life needed to get started. Energy. The first experiment to reveal this really captivated me as a child. I grew up in Chicago and two scientists from my hometown Urey and Miller, took the components that were believed to be Earth's primitive lifeless atmosphere. Then they subjected it to electrical charges. They were able to generate organic molecules. The basic building blocks of life. The thought that energy could make lifeless stuff come alive was just about as exciting as life could get for me. I mean, wow. Now we have a lot more knowledge about early Earth. Billions of years ago, there were many more sources of energy than just lightning. Meteors rained down. There were volcanic eruptions. Super-tides churned these seas. The Earth was a much more energy-rich, violent place. Very lively, right? Lots of things are happening. But out of this lifeless system, and over a long period of time, we actually got life. And one of the best contenders for where life started is a place we might believe nothing could ever survive at all. Deep on the floor of the oceans, something very mysterious happens. Cracks in the Earth's crust open up down there. And heated water and gases spew out. Hydrothermal vents. Chemicals, energy, water. All in one place. Some are even cooking up organic molecules today, life's building blocks. And that's why many scientists believe it's someplace like this where life first started. -So the origin of all of us, all the way back, was fired out of a chimney at the bottom of the ocean. But it would have been nothing more than hot mud if there wasn't one very special element in that stardust. MAE: Space offers an incredible platform to study life as it evolved here on Earth. It's fascinating to think that for us to be here now, the right combination of stardust, energy and water had to come together. And not just any bit of stardust... When you look at life in its most basic form, you find that there's one element that acts like a backbone and holds it all together. And you only get to see how important it is for life when you encounter death. WILL SMITH: For the Hindus of Bali, death is a part of the cycle of life. Not the end. It's up to all the members of the family to make sure the spirits of the dead get to the right place. -They burn the bodies to return the elements of the universe back to their source. The goal? To convert the body into ash. MAE: When you burn something that was once alive, and drive off all the water, what emerges in the flame is the essential bit of stardust that makes life possible. That charred black stuff, carbon. Everything is our body has carbon in it. From our bones to our muscle to our neuro-receptors. It might be hard to understand what makes carbon so great for life, but it turns out that carbon is the ultimate building block. It can connect with other elements in almost infinite ways to generate all the different molecules needed to create a living cell. -Carbon is like the coolest Lego brick you can imagine. My kids loved playing with this stuff, but if carbon was one of those blocks, it'd be the one that they'd all fight over, because you can snap it together just about any way you like. Take something with a lot of carbon in it. Spider silk. Now spider silk is finer than hair, stronger than steel, stretchy as elastic and sticky as gum. All of those qualities just depend on how you snap together that carbon. MAE: Carbon's versatility enables a construction of a miraculous molecule inside nearly every living cell. DNA. Our DNA is one of the most complex molecules in the entire universe. Billions of carbon atoms combined to help hold it together, and this beautifully tangled formation is like an organic super-computer. It contains the instruction manual for life. And every facet and every detail that makes you, you. And it's not just us humans. DNA is at the heart of almost every living cell that ever existed. And you couldn't build it without carbon. -Now hang on a sec, something doesn't add up, alright. I'm no scientist but growing up, I made a lot of instant noodles and I'll tell you one thing, if you take your flavor packet and throw it into a swimming pool, you are not going to get a nice bowl of ramen. So how are you supposed to make DNA in the middle of an endless ocean? WILL SMITH: Take a pinch of star, splash of water, turn up the heat and bam. Happy Birthday Life. Not quite. There's still something missing from our recipe. The pot you cook it all up in. Everything alive needs to be held together and protected. That's true if you're a strand of DNA... Or an astronaut. CHRIS: The space station is like a cell in a way. It's like a bubble of life. JEFF: You really have this sense of being enclosed, you know, just a few inches in front of my eyes is the vacuum of space, and if I were out there, I'd be gone in 10 seconds. LELAND: Inside we have all the ingredients and the systems to keep us alive. MAE: It's the same for living cells. Just at a microscopic level. Water is a critical solvent for life. But if there's too much water... The solution might be dilute, and the molecules of life never bump into one another. So you need something to contain them. Think of a bubble that we blow. That surrounds this pocket of air. And it keeps the air contained. There's something similar encasing all living cells. Membranes. -The holy grail for me is to find out how the first membranes formed. It could have formed in a hot spring, in an ice pool underneath an ice sheet. It's a huge mystery. I've come to Iceland because it's a fantastic natural laboratory. This is Liane, coming in. I'm heading north, I'm at 460 meters altitude and I'm heading to direction 71. It's snowing outside. I'll be there in an hour. Over. Today in Iceland you see volcanoes underneath icecaps. You also see hot springs. Bubbling pools where life could have started as well. Even in the hottest environments, if you take a sample and you analyze its DNA, there is life there. In the early Earth you can envisage these bubbling mud pools, where water dissolves the rocks and makes clay. As the gas comes out, it forms a membrane which then bursts. So think of that membrane not bursting and actually preserving at a very, very small scale... And then if you mix organic molecules inside, you all of a sudden have an organic molecule inside a membrane to form a cell. MAE: Without membranes we would be on a planet covered by a dilute ocean of the building blocks of life. But with membranes, finally there was a way to keep all those building blocks together. I believe there were many opportunities for life to arise. We may have had other types of lifeforms that came and went, but didn't take, right? They didn't hit and stick. But one of them made it. It's called LUCA, which stands for the Last Universal Common Ancestor, for all life here on Earth. LUCA could protect itself with a membrane and reproduce itself. Everything came together in just the right way to create the first living cell, with DNA at its heart. Fast forward billions of years... And we find that all life today uses the same basic chemistry. And this points to one thing, it all originated in that first primitive cell. -Alright, now my grandma, you know, she was kind of small. But LUCA, the great, great, great times a gazillion grandmother of us all, she was tinier than a dot. As far as we know, that cell was the single and only origin of all life. Well, at least on Earth. WILL SMITH: If you check out pretty much anywhere in the universe, you're going to find the same ingredients to cook up life. They're not exotic, they're staples. Now sure, mixing them up just right is hard, but the universe is vast. So does that mean there's a big piping hot serving of life somewhere else out there? That's what one group of explorers is trying to find out. Hunting for strange lifeforms, not off-planet, but right here, in parts unknown. -There's an alien world right beneath our feet. As you drop into this blackness, you have no sense that you're still on this planet anymore. It can be completely disorienting. You're spun around, and which way is up, which way is forward, which way is backwards. These underwater caves are one of the least understood parts of our planet because of the dangers of going down into them. MAE: My desire to understand how life began on Earth also reaches out to the stars, because the ingredients for life probably exist in many places. In our solar system, in our galaxy and in the universe, stardust... Water... And energy. JERRY: Out there we're finding water on different moons that surround some of the planets in our solar system. JEFF: The icy moons of Jupiter and Saturn have oceans of liquid water underneath the ice. CHRIS: Enceladus is a water-world, but with a hot rocky center and plumes of water spraying out into the universe. So maybe there's primitive life on a moon of Saturn right now. MAE: I always wondered, will we find life on other planets? Will we find life outside of our solar system? And as we look beyond the Earth and explore other rocks, I believe that it's likely we will find simple life. It'll look different, it will be different, but our rock, our planet is important to us. It's special and it's unique because it's our home. It's where we evolved. -Think of that fragile moment, billions of years ago, where you and I and all of us began. A tiny moat of life suspended in a ripple of water. The promise of everything that is alive or ever lived in our world. It's the moment nothing turned to something. That stardust sparkled to life. The moment one rock in a remote corner of the universe became most wonderfully strange. Genesis is the bright side of life. Next time, life's dark shadow... Death. (music) WILL SMITH: We sure lucked out with Planet Earth. Blue skies, rolling hills, water everywhere. I mean, this place is nice. But our home didn't come like this out of the box. Earth was a real fixer-upper, and it took some seriously hard work to build this paradise. Nearly four billion years of renovation. Some tiny, some huge... to make this house a home. And when you get up off the planet, you realize life is the one holding the hammer. Eight astronauts with over 1,000 days in space between them can tell us how being up there helped them to truly understand NICOLE STOTT: Creatures on Earth don't just live and die. They actually change the world around them. LELAND MELVIN: The diversity of life can be seen everywhere, from the coral reefs to the mountaintops. The colors of life shine out. MIKE MASSIMINO: You can just feel the life that is there as you observe it from above. When you look at the planet, you realize that it's life that formed it that way. SMITH: Land, sky, rivers, rock, all were shaped by life. But life doesn't just create. It also has the power to destroy. So this story isn't just strange, it's scary. (sirens) New York City. Home to almost nine million people... and this guy. Astronaut Mike Massimino. MASSIMINO: Right across the 59th Street Bridge, where's that? MAN: Queens. MASSIMINO: Yeah, yeah, but what's the name? What part of Queens is that? MAN: Long Island City. MASSIMINO: That's what I was thinking of. Yeah, Long Island City's right across the street there. MAN: Where did you live originally? MASSIMINO: Originally, I came from New York, and then I lived in Houston, Texas, for 22 years. I was six years old when Apollo 11 landing upon the moon. CONTROL: Eagle, we got you now, it's looking good. Over. You are go to continue powered descent. ASTRONAUT: Okay, engines stopped. CONTROL: We copy you down, Eagle. ASTRONAUT: The Eagle has landed. MASSIMINO: Probably by the time I was 8 or 9, I realized that I was no fearless test pilot like Neil Armstrong. I was kind of a scared kid. I didn't like heights, I still don't like heights. I didn't like going fast. So I thought maybe this wasn't the best job for me. SMITH: But New Yorkers don't give up so easily. After years of grueling training, Mike made it into space. And up there, his fears melted away. ASTRONAUT: Okay. Looking good. MASSIMINO: I'm coming out. Mike, you're doing good. MASSIMINO: My second spacewalk, things were going well, and I had a couple moments. I took a look at the planet and... (on radio) This is incredible. I started to become a bit emotional. And just the sheer beauty of it, I started to cry, and I could feel the tears welling up, and what I thought was, 'This must be the view from heaven.' If you could be in heaven, you look down on a planet, this is how we must look from heaven. And then I thought to myself, 'No. That's not right. It's more beautiful than that. This is what heaven must look like.' And I felt like I was looking into a paradise. SMITH: Earth is a kind of Eden, but if Mike had been orbiting way back in the day, he wouldn't be looking down at heaven. He'd be gazing straight into hell. (rumbling) All that fire and brimstone had a role to play. The inside of our planet is melted rock, churning and turning. That means that everything on the surface shifts and slides. Earth's fiery heart powers some big changes. And that's great news for dinosaur expert Omar Medina Ramírez. No need to dig down into the dirt; just stand back and take in the view. SMITH: The power of the planet can take a lakeshore and flip it into a cliff face. But these rock formations and the entire continent they're on might not even be here without a particularly weird form of life. Part algae, part fungi, it grows in the harshest places, and is a food source for Dasher and Dancer and Prancer and Vixen. ISAK MATHIS TRIUMF: Hoo-hoo! Ay! Ay! Gsh! Ay! Ay! Ho! (dogs barking) (singing) MASSIMINO: Lichen are a pretty cool form of life. They exist just about everywhere on the surface of the Earth. About 8% of our planet is covered by this stuff, and they can change the formations, the rock formations, just by their existence. As lichen grow, their fungal filaments physically break apart rock. But strange as it sounds, this process will eventually help create new land. Over thousands of years, lichen and other terrestrial life-forms break down rock. This creates huge amounts of microscopic particles. As some of these particles get washed out into the oceans, they trap water. Over time, this locked-up water is pulled deep inside the Earth, where it helps mantle rock melt and flow more easily. Ultimately, this leads to more volcanic eruptions back at the surface. But the amazing thing is that all this lava means new land is formed that wouldn't be there otherwise. Life helps create the land. SMITH: Best guess is, without life, Earth wouldn't have seven continents. There would only be enough land for about one floating in the middle of a seriously big ocean. Life helped make the ground we walk on. But it didn't do it overnight. MASSIMINO: When you're in space, you get a different appreciation of time, compared to what we have on the Earth. And what you see are changes in the Earth that took place over sometimes millions of years or, or even longer. I think life, no matter what form it is, whether it's a simple form like lichen or an animal or a more complicated form of life like us, whatever level that life-form takes, it is going to change its planet. It might just take a while to do it. CHRIS HADFIELD: From the perspective of a space station, suddenly you can see the entirety of the world's history. It changes your fundamental feel of time. Your fundamental perception of the age of the world, and even though I knew the world was 4.5 billion years old, I'd never got a sense for what that meant. SMITH: It took billions of years for life to mold a barren rock into the world we know. But things didn't just get better and better; sometimes they went wrong. (crackling) Like, almost end-of-the-world wrong. SMITH: I'm a sucker for a tropical island. I mean, I get off the plane and head straight for the beach. Cool sea breeze and sand between my toes. But get this: all of that sand down there? Most of it came out of the wrong end of a fish. CHRIS PERRY: We'll head out towards the coral reef. We'll drop down to about five meters, and we'll survey along there, I think. (air hissing) You can find parrotfish on reefs throughout the tropics. You see them active on the reef, feeding on the hard coral material continuously. (crunching) And the amazing thing is that you can hear this incredible grinding, crunching noise. (crunch) That really gives you a sense of the life on the reef. After the parrotfish have eaten the coral, they then excrete it as sand. SMITH: In one year, one fish eats enough coral to poop out a ton of sand-- literally. And there's an awful lot of fish here. PERRY: That same sand material that you find in the parrotfish poo can be found in the islands themselves. On some islands, the sand material is made up of over 70% parrotfish poo. The parrotfish are absolutely crucial to the development of these islands. SMITH: But life's not done. Fish form the fresh beach, then more life follows on. And presto, instant island paradise. HADFIELD: As you fly across, there are little light blue rings down in the water beneath you. There's the deep blue of the ocean around them, and then all the different changing blues that are possible as the water gets shallower and shallower. But what's intriguing to think is that living organisms down there created that beautiful vista that is visible from space itself. MASSIMINO: It's kind of amazing what a small creature can do. That a bunch of little fish can build an island just by going about their daily routine. That's quite an impact. SMITH: Parrotfish aren't in the business of seaside resort development. I mean, they were just snacking. These islands were a happy accident. But life's little accidents don't always work out so well. MASSIMINO: About three billion years ago, bacteria in the oceans of the early Earth produced a by-product--oxygen-- which transformed our world. But when this accidental waste gas filled the atmosphere, it reduced levels of warming methane, cooling the planet. Earth started to freeze, from the poles all the way down to the equator. It froze like a giant snowball. Billions of years ago, things weren't looking that great for us, but thanks to all the planet's water, we got a lucky break. (creaking) Ice floats on water, and underneath it is a kind of sanctuary. Life managed to cling on down there, under the ice, for millions of years until eventually the planet's volcanoes saved the day. We think that as they pumped out carbon dioxide, the planet began to warm up. (cracking) The ice melted, and life on Earth really took off. SMITH: Life almost killed itself when it messed with the atmosphere. But it survived... and put its roots down on land. The creatures that emerged, weird and wonderful and new, helped build our modern world. But not in the way you might expect. (birds chirping) SMITH: They don't walk, they can't see, they barely even move, but plants are almost unstoppable. Give them enough time, and they are Earth's ultimate transformers. (birds calling) SMITH: Roots rip through rock like slow-motion excavators. But they don't just destroy. Those plants? They shape how rivers run. MASSIMINO: Plants have had a big impact on the Earth. As plants grow, their roots spread out and intertwine. They help hold soil together, like a kind of living glue. Plant roots make riverbanks more solid, so instead of spreading outwards, plants cause rivers to get deeper, and then begin to wind and switch back on themselves. STOTT: Rivers and land formations stand out. It's almost like somebody has painted trees on the planet. MASSIMINO: These bendy rivers have become a crucial habitat for all kinds of living things, including us. JERRY LINENGER: You look down at Earth and you see the Nile River. You know, the cradle of civilization, the Tigris-Euphrates. The Yangtze over in China. And you just sort of have an appreciation of history and of mankind becoming civilized. SMITH: We've founded some of our greatest cities at a bend in the river. And plants help bend those rivers. Once we settled, we started to build. Brick by brick and rock by rock. Life gave us perfect plots of building land, but it gave us even more than that. All those rocks we built with? Some of them used to be alive. MAN: Be super careful with the rock here. It's really not so great. CAROLINE CIAVALDINI: Yeah. MAN: I'm watching you. CIAVALDINI: Oh, my God. MAN: Good job. CIAVALDINI: I'm specially aware of the landscape from a geological point of view. MAN: Can you find any gear? CIAVALDINI: Got a good hold at least. Because obviously, my first focus is the rock. SMITH: This rock wasn't made from molten lava. It's made of shells and bones. Layers and layers of life that died and sank and were squeezed into stone. Limestone. CIAVALDINI: Limestone isn't the most solid rock. MAN: Be careful. CIAVALDINI: There is always the possibility of rock falling above you. MAN: But I think I can keep on climbing across the chimney, which makes it a bit easier. CIAVALDINI: Alright. When you've got this tiny little summit where nobody's been on top of it, there is obviously something very special. Woo-hoo! MAN: Woo-hoo! MAN: Good job! Good job! CIAVALDINI: We did it! SMITH: Limestone is soft because it's made of shells. That makes it tough to climb, but easy to cut and carve and make into monuments. In places, you can still see those seashells in the monuments' walls. MAN: Can I help you? MASSIMINO: How you doing? MAN: Fine. You want a ticket? Next train to Bronxville. MAN: To Bronxville. Okay, Bronxville. Grand Central Station, you can look in the beautiful limestone that cathedral-like terminal is made out of. You can see evidence of little fossils right in the rock. Next time you're catching a train at Grand Central Station, take a look at the rock, and you'll see some evidence of the animals that once were here on Earth many years ago. It's not just building material. Almost everything we think of as being man-made has been given a helping hand by other life-forms. The tar in the road. The fiber in your clothes. The polish in your toothpaste. All these things are made from organisms that died millions of years ago. If it wasn't for those prehistoric critters, we'd struggle to turn on a light, let alone build a space station. SMITH: We've thrived with a little help from our friends. But it's not all smooth sailing. Because success brings its own problems. SMITH: Life has been shaping the Earth for billions of years. Now, it's our turn. We may be new here, but the changes we're making are pretty easy to spot. MASSIMINO: Flying over the Earth during the daytime, you can't see buildings or motion or people at all. It almost looks still and silent, almost like a painting that you're looking at. When you pass into nighttime, then wow, you know, the planet comes alive. Space becomes a very magical place at night. You can see where people are living, you can see where civilization exists, because you see their lights. If you see one of these cities, space gives you a different perspective on it. STOTT: At nighttime, the pattern of lights, you just think 'humanity' when you see that. It's so obviously man-made, because you'll see these straight lines of lights, or you know, circles of lights, where cities are just built in rings. LELAND MELVIN: Seeing the planet at night from space lets you see the footprint of human beings. The city lights at night, the byways, the highways, the homes, you see all of that. Makes you wonder how powerful the human presence is. SMITH: We have spread far and wide over this old rock, adding a whole new layer to the planet's surface. But we didn't make all of this stuff out of nothing. (jackhammering) (engine starts) SMITH: Franco Barattini helps extract some of the most beautiful natural resources on the planet, but it's a dangerous job. (beeping) SMITH: Marble has been mined here since Roman times. It's done with skill and loving care. But you know what? A showroom isn't the only place to see that gleaming white stone. MASSIMINO: Bright white marble in Italy, you can see that. It's looks like there's a snowfield in a time of year when we wouldn't have any snow. But it looks as if it's snow, because it's that white marble being taken from the Earth. And it's not just marble. When you're floating above the Earth, you see many different examples of how our desire for natural resources is changing the planet, and not always in a good way. MELVIN: There are places on the planet, when you fly over top of it, you see these vast stretches of land that have been mined for coal or mined for minerals or riches, and this leaves a blight on the surface of the planet. And it's ghastly at times to see some of this. SMITH: The scars and scratches in the Earth's surface are one thing, but the damage we can't see is the real danger. HADFIELD: Of all the changes that we're making to the Earth, I think it's changes to the atmosphere that we should be the most worried about. That's the one that could really lead to some serious problems. You just have to look at what happened in the planet's past to see how badly it could go. MASSIMINO: Our planet has always been changing. It's been changing over billions of years. We're just the latest form of life to do it here. There's a big difference between then and now, and we're making these changes, but we're aware of what's going on, and we have brains in our heads that can allow us to try to understand what's happening and control it. SMITH: We're transforming our planet every day. But it's very possible we could hurt it so badly... ...that we can no longer live here. And what if we do? What would happen if humans disappeared? SMITH: Life has created the most remarkable planet in the solar system. But there is no guarantee that humans are gonna always be here to appreciate it. Thing is, the Earth will go on spinning, life will go on living. Astronauts like Mike can see that as clear as day. MASSIMINO: There was this one particular time when I was on the space shuttle, and we were going from darkness into light. And I could feel the warmth of the sun coming. As I looked down at the Earth, there was this line that was moving, and the thought that went through my mind was, 'The sun will come up tomorrow.' This cosmic dance of our planet going around the sun and rotating as it does this, this has been going on for billions of years. It'll be going on for a long time after we are gone. SMITH: The Earth doesn't need us. Neither does life. And if humans don't make it, life will go on changing things. Even the things we leave behind. SMITH: Minoru Kinoshita left here when he was 13 years old. This is the first time he's been back in 50 years. SMITH: Hashima Island was once the most densely populated place on Earth. (children shouting in unison) People came here to mine coal. When that ran out, everybody left. This place was abandoned practically overnight. 40 years later, life has started taking Hashima back. SMITH: If humans died out, most of our man-made world would fall apart. Life would rip it up and transform it. Reclaim and remold it. Our buildings would crumble, our towers would fall, our lights would go out. But the Earth would endure. Not so different from the way we found it. A big, blue ball... ...that life made into a home. One hot dog with mustard, please. I think my concept of what I consider to be home changed over the years. Alright. Thanks very much. See ya. (wings flapping) When I was a little person, my home was my home on Long Island and Franklin Square, and my block surrounding it. You know, that was my world, I guess. Going to space and seeing where we live from above and then turning and looking to the rest of the universe... I think now I consider my home to be Earth, and that is my home. I might live in one part of it, but I think of my home now as Planet Earth. That's our home. SMITH: We moved into a populated planet, and in the short time we've been here, we have changed it. But we're not the master craftsmen. We've just been moving furniture around. Life worked on this planet for billions of years before we even walked in the door. It transformed a barren rock into a paradise. A paradise we should be careful to hold on to. Life transformed this planet, but we aren't the only rock out there. Next time... Do we have any neighbors? WILL SMITH: What do you need to win a game of chess? Patience, clever tactics, loads of imagination. You look nervous. (laughs) What makes us human is the squishy triple-pounder inside our heads. Check. It lets us checkmate our friends, build skyscrapers, and lift a special few of us into space. (roaring) Eight astronauts with over 1,000 days in space between them JEFF HOFFMAN: From space you get the big picture. You really see human civilization spread out below you. NICOLE STOTT: As far as we know, there's nobody else like us out there in the universe. JERRY LINENGER: The only reason I'm able to comprehend the incredible complexity of the Earth is because I have an incredibly complex brain inside my head. LELAND MELVIN: We are the only species on this planet that can construct realities in our mind and then go actually build it. SMITH: But for three billion years, life didn't even have a brain. MELVIN: The story of how our mind evolved on this one strange rock is one of chance, coincidence and impossible odds. SMITH: I am going to tell you about the most incredible place. The weird connections, the dynamic forces that created us. A species with a brain as complex as yours and mine. The human brain is unique. Not just because of its size, but also its ability. It can meet challenges that are dangerous, demanding. SMITH: And wonderfully absurd. (applause) (crowd chanting) SMITH: In Spain, thousands come together every year to build towers out of people. SMITH: A ten-story human tower with the youngest kids on top. Right. Claudia and Marina, they're seven. (crowd gasps) (clapping) (cheering) SMITH: Humans are like no other creature on Earth. We do these things that might seem pointless, not because we're stupid; because we're smart. And we work as one. It's that ability to link our minds together that put those girls on top of that tower and also put men and women up in space. One of them is Leland Melvin. Former NFL player, mechanical engineer, and astronaut. Strong, smart, brave, and pretty much unstoppable. But Leland nearly didn't make it to space. An accident in his training brought his dreams to a halt. MELVIN: The only way to really simulate a spacewalk on Earth is in a pool. I remember getting in the suit, putting my gloves on, my boots. MELVIN: As you're going down in the spacesuit, you have to clear your ears. MELVIN: Ten feet down, I realized that the Styrofoam block, you press your nose against it to clear your ears, was missing in my helmet. I tell the test director, turn the volume in the headset up. I was straining to equalize the pressure. And then, I immediately hear nothing but static. They were pulling me out of the water. And now I see the flight surgeon walking towards me. He reaches up and touches my right ear. He's moving his lips, but I don't hear anything he's saying. And then I can feel the blood starting to trickle down on the side of my face. I'm like, 'Wow, something's really wrong.' I was completely deaf. Somehow the connection between my brain and my ears had been severed, along with my chances of going to space. The accident gave me a profound appreciation in what we take for granted. The thing that makes us us: our brain. The human brain sets us apart from all other creatures on this planet. It might look like a lump of Jell-O, but it's the most complex thing in our universe. Inside, there's a vast network with 100 trillion connections. That's more than the number of stars in our own Milky Way. It hosts our memories. Our sensations. Our dreams. And all this depends on tiny cells firing electrical signals. There's 86 billion of them. We call them neurons. SMITH: 86 billion. Wow. I'm just glad someone else was counting. But here's the thing: most of life on Earth does just fine without a brain. I'm talking about some of Earth's oldest inhabitants. Some brainless creatures are so successful, you can even see them from space. LINENGER: On a bright, sunny day, I'm looking down, and for 1,000 miles, I see an organized city of coral. PEGGY WHITSON: They just glow. It's just like the most beautiful art in the world. MELVIN: This burst of color. I'd never seen colors that vibrant before. It's kind of amazing that corals are vast, motionless structures, that thrive without a brain. SMITH: In the country of the brainless, the tiny-brained is king. Meet this little guy. He's got more in common with us than you might think. Inside, he's got neurons, too, just not as many. About 200. Kind of a starter kit. He's a baby sea squirt looking for a home. His neurons do simple stuff, like detect light and twitch his tail. once he's found the right rock, his swimming days are over. For the rest of his life, he stays put. He dumps the tail and consumes the neurons that made it move. Then, it grows into a big, old sea squirt. Takes 'use it or lose it' to a whole new level. MELVIN: It's kind of a freaky thought that, you know, when neurons were developed, they weren't for thinking. They were for simple motion or movement. But one day, neurons like those, the ones inside our brains, would help create things like rocket ships going to space, cities and music. SMITH: Making a tail twitch to move a yard or two requires just a few neurons. However, the more advanced stuff, that needs an awful lot more. Life needs to sense its surroundings, otherwise, it's just flailing around in the dark. SMITH: There is nothing more complex than the human brain. But the more complicated something is, the more ways it can go wrong. (bird shrieks) MELVIN: After my training accident, the doctors couldn't figure out what was wrong with me. Everything looked physically intact, but they couldn't fix me. My goal of getting to space seemed to be thwarted. But all I could think about was whether I'd ever hear music that I played again. Music has been such a big part of my life. (playing piano) And so, when the music was silent... That's when I just broke down and started crying. SMITH: Leland's ears were fine. That's not where the problem was. Because you don't just hear with your ears, you also hear with your brain. It's the same for all the senses, they link our brains to the outside world. And over hundreds of generations they evolve to suit that world, no matter how harsh it is. SMITH: Hunters have lived here for thousands of years. But to survive, they borrow the senses of a creature that's been here even longer. (horse snorts) SMITH: The eagle is like a weaponized telescope. It can see a fox up to two miles away. Out here, that's a crucial tool in the fight for survival. (eagle chirps) (yells) (yelling) (chirping) SMITH: But to see like an eagle, you need more than eagle eyes; you need an eagle brain. (squawking) MELVIN: Eyes deliver masses of data about the world around us, and all that lifesaving data needed something powerful to make sense of it. Simply put, if you're an animal with eyes, you're gonna need a bigger brain than a sea squirt. Eyes were a real game changer. But it's not just the eyes. Creatures had to develop an array of senses that are each calibrated to deal with the ever-changing environment of Planet Earth. Not just barren desserts, but these very dense jungles, teeming ocean reefs, and even icy Arctic waste. The planet's varied landscapes played a significant role in how animals sense. SMITH: What goes for them, goes for us. The planet shaped our senses, too. It's something you might not notice unless you leave the planet. MIKE MASSIMINO: Our senses have evolved to operate on Planet Earth. MAE JEMISON: When you're up in space, the inner ear isn't registering an up and down. MELVIN: So, your sense of orientation only comes from your eyes. You know that weird feeling in the pit of your stomach, when you go over the top of a rollercoaster? I was basically in that moment for an entire day. STOTT: We're Earthlings. That's just who we are. MELVIN: The evolution of the senses in the primitive brain have allowed living creatures to interact with our planet in a way like never before. But looking at our planet from space, you can see it's not just varied, it's dynamic. SMITH: Sometimes, the environment changes quickly, and when that happens, you have to be just as fast to adapt. Like when the sea level rises without warning, and now, you're an island castaway. Macaques are great with their hands. They peel fruit, climb trees, and do each other's hair. But on these islands, they do something no other macaques do. They use rocks as tools to shuck oysters. Macaques don't normally eat them, but when they were stranded by the rising sea, they needed new ways to get a meal. They weren't born with this skill; a smart monkey had to work it out. This is something only complex brains can do-- not just sense and react, but learn, adapt and problem solve. But just because a macaque can learn to shuck oysters doesn't mean it's gonna open a seafood restaurant. Only a human would make that mental leap. So, how come we're so different? SMITH: Monkeys were the first primates in space, but it wasn't exactly their idea. In fact, they were probably against it. So, how come we're the apes with the big ideas? Well, it's a long story. A story about something that may not exist anywhere else in the solar system, maybe the universe. Fire. (rooster crows) SMITH: The Himba people have kept this same fire burning for generations. SMITH: As far as we know, this planet is the only one with the right conditions for fire to burn. But there's one thing that fire gives us above all else. SMITH: But cooking food does something that's way more important than just making it tasty. MELVIN: Woo! We got fire, are we ready for food? We as humans have these power-hungry brains. A big chunk of our body's energy has to be used to keep them running. Turn, baby, turn. By cooking, we're actually breaking down the cell walls of the food that releases so many more nutrients and calories, to help fuel our big brains. One of the key moments in the history of our species was when our ancestors harnessed fire. Alright, get your plates. The theory goes, cooking let us get more energy out of every bite of food. So we spent less time feeding our brain and more time using it. SMITH: Try going a day that isn't touched by fire. You couldn't imagine life without it. But a brain that could harness fire may not have evolved in the first place if it wasn't for a force so powerful, it made the highest mountains on Earth. (monks chanting) SMITH: The fossils tell us that these mountains, once at the bottom of the sea, were forced high into the sky. LINENGER: When you're in orbit, as you come over the Himalaya Mountains, you almost feel like you need to fire the thrusters a little bit. You can tell where that subcontinent just jammed into the Asian continent and thrust those mountains up. CHRIS HADFIELD: This collision between the smooth flatness of India and these rugged, crumpled mountains, it's like watching a super slow-motion train wreck. The further you get away, you can kind of see these overarching themes to the way our planet is formed. MELVIN: It was forces like these that would transform one particular corner of our rock into the cradle of humanity. The Great Rift Valley in East Africa was once a lush green forest, a paradise for apes. But the Earth's crust shifted, mountains rose, and the climate changed, making it a much tougher place to live. It's hard to really know exactly how our ancestors adapted over millions of years. The changes may have pushed apes to do things like innovate the tools. Or walk on two legs. And even harness fire. Whatever it was, we came out the other side as early humans, with bigger brains. SMITH: We took off across the planet, and there was one uniquely human skill we brought with us. Here I am, talking to you, and some of you are even listening. What you're hearing is probably the most powerful tool we've ever mastered. So, how do you get a brain that can tell a damn good story? (people speaking different languages) SMITH: We speak. (all talking) SMITH: We link signs and sounds to thoughts and things, in countless ways, creating almost infinite meanings. That takes a lot of brain power. JULIE MISAKI: Moving to Hong Kong has been amazing. I'm originally from Japan, but I've lived in Hong Kong for six years now. But it has its challenges. Even just buying dinner can get complicated. A lot of us foreigners try to learn Chinese, but it's not always easy. One word can actually have many meanings, depending on the tone you use. For example, if I say xiao, it means burn, or xiao, it means little, or xiao, it means laugh. Use the wrong tone, you could be in big trouble. MELVIN: It's only us human beings that have developed complex language. Unlike many other languages, Chinese uses the musical areas of the brain to extract meaning from all those tones. And that takes a lot of processing power. But the really big question is why we have any language at all. It's partly due to the size of our big brains. But there could be another factor at play. One theory is that it was something really tiny. There's a version of a gene, called FOXP2, that only us humans have. Take it away, and you'll struggle to talk. No one knows how we've got this mutation. (speaking Japanese) But we do know... ...it gave us more precise control over our mouth and our tongue muscles. And that let us make more sophisticated sounds, helping us turn thoughts into words. SMITH: Small genetic twists turned us from a bunch of folks who grunt to a species that can tell xiao from xiao, from xiao. Sharing ideas, communicating them, lets us do things that alone would be impossible. Something pioneers know full well. ROCKY ROBINSON: Okay, let's do it. I'm getting all kinds-- I've wiped it off, but I have all kinds of salt on me. My shield got covered in salt. MAN: Turn the water pump off. ROBINSON: We're here in Bolivia trying to break the motorcycle world land speed record. We probably don't have a better opportunity than we have right now to see just how fast this bike will go. This is a huge team effort. We communicate a lot, the team and I. Communication is a huge advantage. It takes so many people to come up with a machine of this caliber. (engine revving) You have all these people doing all this stuff for you, but once that canopy closes... MAN: You ready? ROBINSON: You're all alone. MAN: 45, hit it, Rocky! MAN ON RADIO: Full speed, 333.9. MAN ON RADIO: Roger, six. ROBINSON: Whoa, whoa, whoa! There's something wrong with the motor. MAN ON RADIO: He's coming to a...he's slowing down. Everything okay down there? MAN ON RADIO: Seems okay. ROBINSON: It is going really strong, and it's, whoa, whoa, whoa. MAN: Main off? ROBINSON: Yeah. MAN: Okay. ROBINSON: Got up to right around 378 miles an hour, and then the turbo coupler came off. It's frustrating. It's a huge team effort, and, you know, we're all trying to reach our goal. Probably 95% of the time there is something going wrong. That's why records last so long. Everything about land speed racing is learning what's new and how to improve things. We learn a lot, and I think we can put that to good use in the future. SMITH: I'm with Rocky on this. You get knocked down, you get back up again. Communicating helps you face failure without fear. But our brains adapt. So if we lose the ability to communicate, our brain might find a work-around. It's flexible. Talk to Leland about it. MELVIN: During the time of recovery from my hearing accident, there was a point when I could feel my brain rewiring itself to hear again. The brain over time can make adjustments to compensate for losses or changes. And I think that's what happened to me. My hearing started coming back about three weeks after my accident. But it took two more years for me to recover properly. Then finally, the chief medical officer for NASA pulled out a piece of paper that said, 'You are now cleared to fly in space.' That was one of the most incredible days of my life. I never took my brain for granted again. (crowd cheering) SMITH: With that flexible brain, we learn, adapt, and problem solve. Our brains give us language, allowing us to share those lessons with others. And writing lets us pass on that knowledge through time. All that human brain power, all that knowledge through written textbooks, through calculations, through mathematics. HOFFMAN: That just led to a huge explosion in the development of civilization. WHITSON: We can get a lot smarter, because we can learn a lot more from the previous generations. SMITH: Humanity is linked together by a network of minds that spans time and space. And that's helped us create things of dazzling complexity. The most complex one we've ever made is floating above us. MAN ON RADIO: Ignition sequence start. Five, four, three, two, one. MELVIN: You're lifting off of the planet. Feeling 3 Gs on your chest as you're being propelled to the cosmos. It is one heck of a ride. MELVIN: After losing the sense of hearing, it took so many years for me to get to the launchpad, but it just took a few minutes to get to orbit. Good morning, Houston. MELVIN: We got to space, I saw the planet. It just blows your mind. This burst of color. I've never seen colors And I almost had to, like, smack myself to get back to work. If you could get the other... the expedition four crew, that we have them in sight. MELVIN: And then I saw this little dot out on the horizon. And we get closer and closer and closer. The first time I saw the space station flying overhead, I never knew how complex a vehicle it was. You know, you could see the intricate design in these modules, all these things that were envisioned by the human brain. WHITSON: So, you know, when you approach it, it's just so beautiful. It's an amazing, amazing engineering marvel. HOFFMAN: There's no question that the space station is the greatest international scientific project that's ever been undertaken. LINENGER: It's like, wow, this thing is awesome. And I'm gonna get to live on that thing for four or five months. MAN ON RADIO: Coming in now and carrying the camera, mission specialist Leland Melvin. MAN: How you doing? MAN: Bull in a china shop, man. Climbing this hill to space was one of the hardest things I've ever done. I never imagined myself going deaf, I never imagined coming back and getting this opportunity after that accident. And it's really a similar story for all of humankind. Everything we've achieved as a species is the product of a lucky chain of accidents. SMITH: To get here, we needed a planet to congeal out of dust. In the right place for life to form and mold our world, allowing us to breathe and grow complex. We needed to be shielded from our sun, gifted with a moon, and granted seasons. We needed just enough bombardments and near-annihilations to let life meander through its twists and turns and evolve a species with a brain as complex as yours and mine. (baby cries) MELVIN: When I was on the space station, looking back at the planet, it gave me Humans are a wonderful, extraordinary oddity. SMITH: Good job, man, great game. With this blob of Jell-O, these 86 billion neurons, we've left the planet and looked far, far out into the universe, trying to unravel the mysteries of the cosmos. But no matter how far out we look, the most far-out thing we've ever found is right between our ears. What does it feel like when you finally come back to Earth? Is there really no place like home?