Since the dawn of civilization, we have always wondered where the Moon came from. But until we finally managed to visit it in 1969, its origins remained a complete mystery to science. Analysis of samples brought back from the NASA Apollo missions suggest that the Earth and Moon are a result of a giant impact between an early proto-planet and an astronomical body called Theia. Here are other Moon Origin Theories - There used to be a number of theories about how the Moon was made and it was one of the aims of the Apollo program to figure out how we got to have our Moon...
Prior to the Apollo mission research there were three theories about how the Moon formed. The evidence returned from these missions gave us today's most widely accepted theory.
Capture theory suggests that the Moon was a wandering body (like an asteroid) that formed elsewhere in the solar system and was captured by Earth's gravity as it passed nearby.
The accretion hypothesis proposes that the Moon was created along with Earth at its formation.
The fission theory suggests Earth had been spinning so fast that some material broke away and began to orbit the planet.
The giant-impact theory is most widely accepted today. This proposes that the Moon formed during a collision between the Earth and another small planet, about the size of the planet Mars. The debris from this impact collected in an orbit around Earth to form the Moon.
Proto-Earth and Theia -
Before Earth and the Moon, there were proto-Earth and Theia (a roughly Mars-sized planet).
The giant-impact model suggests that at some point in Earth's very early history, these two bodies collided.
During this massive collision, nearly all of Earth and Theia melted and reformed as one body, with a small part of the new mass spinning off to become the Moon as we know it.
Scientists have experimented with modelling the impact, changing the size of Theia to test what happens at different sizes and impact angles, trying to get the nearest possible match.
Scientists are now tending to gravitate towards the idea that early Earth and Theia were made of almost exactly the same materials to begin with, as they were within the same neighborhood as the solar system was forming. If the two bodies had come from the same place and were made of similar stuff to begin with, this would also explain how similar their composition is.
A balancing influence
Having a moon as large as ours is something that's unique in our solar system. While other planets have tiny moons, the Earth's Moon is almost the size of Mars. If you look at other similar planets to ours, they wobble quite a lot in their orbit (the North Pole moves) and as a result the climate is much more unpredictable.
The Moon has helped stabilize Earth's orbit and reduced polar motion. This has aided in producing our planet's relatively stable climate.
#prehistoric #science #space
Prior to the Apollo mission research there were three theories about how the Moon formed. The evidence returned from these missions gave us today's most widely accepted theory.
Capture theory suggests that the Moon was a wandering body (like an asteroid) that formed elsewhere in the solar system and was captured by Earth's gravity as it passed nearby.
The accretion hypothesis proposes that the Moon was created along with Earth at its formation.
The fission theory suggests Earth had been spinning so fast that some material broke away and began to orbit the planet.
The giant-impact theory is most widely accepted today. This proposes that the Moon formed during a collision between the Earth and another small planet, about the size of the planet Mars. The debris from this impact collected in an orbit around Earth to form the Moon.
Proto-Earth and Theia -
Before Earth and the Moon, there were proto-Earth and Theia (a roughly Mars-sized planet).
The giant-impact model suggests that at some point in Earth's very early history, these two bodies collided.
During this massive collision, nearly all of Earth and Theia melted and reformed as one body, with a small part of the new mass spinning off to become the Moon as we know it.
Scientists have experimented with modelling the impact, changing the size of Theia to test what happens at different sizes and impact angles, trying to get the nearest possible match.
Scientists are now tending to gravitate towards the idea that early Earth and Theia were made of almost exactly the same materials to begin with, as they were within the same neighborhood as the solar system was forming. If the two bodies had come from the same place and were made of similar stuff to begin with, this would also explain how similar their composition is.
A balancing influence
Having a moon as large as ours is something that's unique in our solar system. While other planets have tiny moons, the Earth's Moon is almost the size of Mars. If you look at other similar planets to ours, they wobble quite a lot in their orbit (the North Pole moves) and as a result the climate is much more unpredictable.
The Moon has helped stabilize Earth's orbit and reduced polar motion. This has aided in producing our planet's relatively stable climate.
#prehistoric #science #space
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TVTranscript
00:0099% of all species that ever lived were wiped out in a series of global catastrophes.
00:10Disasters that push life to the edge of extinction.
00:14But without them, we simply wouldn't be here.
00:20Just after its birth, a violent event in the solar system changed the Earth forever.
00:29Two planets collided in the cold void of space, and one of them was ours.
00:35The impact nearly destroyed our world, but instead made it a home.
00:41Our planet is around four and a half billion years old.
01:00During that time, it has lurched from one terrible disaster to the next.
01:08It's tough to get a handle on the enormous timescale of the events that shaped us.
01:16To put it in perspective, imagine the whole of Earth's violent history
01:20compressed into the 24 hours of a single day.
01:28The clock started ticking at midnight, and the first catastrophe was just minutes away.
01:36Our solar system hadn't even finished forming.
01:41Twenty infant planets circled a new star, our sun.
01:46One of them was Earth.
01:50Its surface was a vision of hell.
01:55There was no water, no oxygen, and the entire planet was shrouded in toxic volcanic gases.
02:05But now, before the Earth had a chance to stabilize,
02:08it collided with another infant planet circling the sun in an impact of biblical proportions.
02:18The collision was so catastrophic that it nearly annihilated the young Earth.
02:24But instead of destroying it, it set up a chain of events that transformed the planet
02:29and triggered the birth of life itself.
02:36Without this disaster, no life, including us, would be here.
02:44But how do we know what happened?
02:46And how did this collision set the stage for life to evolve?
02:52Astronomer Bill Hartman has spent his life studying the events of the early solar system.
02:58But it's tough with so little evidence around.
03:02The record of the very first part of the Earth's history,
03:06all of that is wiped away on the Earth itself,
03:09because we have erosion and rain and continental drift
03:13and continents colliding and mountains coming up and so on.
03:17It turned out the best way to study Earth's earliest days
03:21was actually to look at the surface of neighboring planets.
03:26Like the nearby Mercury and Mars,
03:28the surfaces of the planets are covered with impact craters.
03:33The craters date back over 4 billion years
03:36and, like time capsules, gave Hartman priceless data on conditions faced by the young Earth.
03:44You start looking at those craters and you discover
03:46that there are not only 100-mile craters and 200-mile craters,
03:51but 600-mile features, some very large objects.
03:56These craters paint a picture of a very violent period,
04:01of a solar system littered with cosmic debris,
04:05where millions of asteroids and comets smashed into the young planets.
04:10Nowhere was safe.
04:12The Earth would also have been bombarded.
04:16It was a window into the early history of the Earth
04:18and it made us realize that the Earth itself
04:21has had this tremendous history of impacts,
04:24enormous impacts that could have really damaged the whole planet.
04:31It got people thinking about what would be the effects of giant impacts on the Earth.
04:39Hartman realized that it wasn't just small asteroids hitting the planets.
04:43There were much larger objects, too.
04:46And the larger the asteroid, the more dramatic the consequences.
04:53So, the impact process, it's a wonderful kind of paradox.
04:59On the one hand, the small impacts tend to make everything the same.
05:03Millions and millions of impacts averaged out.
05:05But the big impacts give individual personalities to the planets.
05:10Take our planet, for example.
05:13It tilts at an angle of 23 degrees,
05:16with a nearby orbiting satellite, the Moon.
05:22These two traits were clues to Hartman, who proposed a radical theory.
05:27He suggested the Earth had been hit by something the size of another planet,
05:32creating that tilt and the Moon.
05:36The key to our idea was that as the planets grew,
05:39you had the finished planets, but you still had leftover bodies.
05:43If one of those crashes into the Earth, just as the Earth has finished forming,
05:48that can blow out material from which the Moon could form in orbit around the Earth.
05:55Hartman built up a picture of the moment Earth collided with another planet.
06:02Imagine the scene.
06:04The newly formed Earth hurtling around the solar system
06:08and 20 other planets doing exactly the same thing.
06:14One of them, Theia, was about the size of Mars,
06:20and it was orbiting the Sun at exactly the same distance as the Earth.
06:26The two planets were on a collision course.
06:31Theia hit the Earth at 25,000 miles an hour,
06:36with the force of billions of megaton bombs.
06:54The impact ripped off huge sections of the Earth's crust.
06:59Billions of tons of debris blasted into space.
07:06A ring of red-hot dust and rock formed around the Earth.
07:17Over the next 100 years, the rocks and dust slowly clumped together
07:22into a ball 150th the size of Earth.
07:29We call it the Moon.
07:32When Hartman suggested the idea in the 1960s,
07:36people had a tough time accepting it.
07:39Scientists were thinking of everything in terms of slow geologic processes,
07:45one grain of sand at a time, you know, wearing down mountains.
07:49To think of something as colossal as the Moon
07:53forming as a result of a single event was hard for people to swallow.
08:02But Hartman's theory got a boost from NASA.
08:07In 1969, the Apollo landing craft Eagle touched down on the surface of the Moon.
08:15That's one small step for man,
08:20one giant leap for mankind.
08:24One giant leap for mankind.
08:31American astronauts made six visits to the Moon.
08:38They explored its surface, drove around its craters,
08:42and they brought back 840 pounds of moon rock.
08:48For the first time, scientists could find out what the Moon was actually made of.
08:54The results were surprising.
08:57The lunar samples had a remarkably similar chemistry
09:01to the outermost layer of the Earth's crust.
09:05Most researchers found this discovery interesting.
09:09But to Hartman, it was vital new evidence.
09:14So you have crustal rocks, you have rocks on the surface,
09:18and a big impact comes in and blows all those crustal rocks away.
09:22And that material goes into space and forms the Moon.
09:26But many scientists were still skeptical.
09:29They couldn't see how a cosmic impact could create the Moon and Earth as they are today.
09:35I actually had people telling me we should exhaust every other theory first
09:39because this was such an outlandish idea.
09:43Hartman finally got the proof he wanted
09:46after a chance meeting at a conference with astrophysicist Robin Canup.
09:51She was using computer models to study Saturn's moons.
10:00Bill Hartman came up to me after my talk and asked me,
10:03have you ever thought about applying your models about how moons form
10:07within and near Saturn's rings to the origin of the Moon?
10:11And I said no.
10:13So she tried the same modeling software to recreate the early solar system.
10:19Then she plotted a planetary collision of the kind Hartman was suggesting,
10:25one that would leave the Earth and Moon as they are today.
10:29So we're four and a half billion years ago at the end of the Earth's formation.
10:33And we're in space and we're watching as a small planet,
10:37the planet on the right, is about to hit the young Earth
10:40represented by the larger planet on the left.
10:43The collision takes place and as we see it hit, it hits in a glancing blow.
10:48And you can see the impactor is completely destroyed by the collision.
10:54Canup's models demonstrated what might have happened during the collision.
10:59Thea, the impactor, was completely annihilated.
11:04Earth survived, but only just.
11:08The impact was so powerful it distorted the planet's shape.
11:13The Earth responds to this impact like a molten blob of rock.
11:18And as the impactor comes in, in this grazing blow,
11:22it generates something like a wave that you would get when you throw a rock
11:26at an oblique angle into a lake.
11:29And that wave propagates around the surface of the Earth.
11:33The collision created a tidal wave of molten lava.
11:38Now this collision is incredibly violent.
11:40So violent that there's enough energy to completely melt the Earth.
11:44And in fact, at the end of this impact,
11:47the Earth is surrounded by an atmosphere of vaporized rock.
11:53Trillions of tons of debris blasted out into space.
11:59Here we see part of the impacting planet sheared out
12:03into this long arm of material that produces a disk
12:07that we're seeing almost edge-on in this view.
12:10And it's from that disk that the Moon later coalesces.
12:16Canup's model backs up Hartman's theory
12:19and shows that the Moon is made of debris from both Thea and Earth.
12:25So I actually called my colleague and said,
12:28you're not going to believe this, but I tried this Mars-sized impactor case
12:33with about a 45-degree impact angle, and everything worked.
12:37And he said, you better check it again.
12:39And so I did check it again and did many more of these simulations.
12:42And sure enough, that type of impact is the one
12:46that gives us the Earth-Moon system today.
12:49Canup's work was further evidence
12:52that Hartman's wild theory was right.
12:54So it was very exciting as Robin did her models
12:57and they started to say, yes, there can be Moon-forming debris
13:01left in orbit around the Earth, and the Moon would form from that debris.
13:06Hartman and Canup's work proved that our Moon
13:09was the result of a violent cataclysmic collision between Earth and Thea.
13:16The Earth narrowly escaped complete destruction.
13:20But the collision triggered a remarkable series of events
13:24that transformed the planet.
13:26It became a climate hellhole,
13:29with extreme weather conditions and giant tides.
13:33But these deadly conditions also created the building blocks
13:37for life itself to evolve.
13:41Just 10 minutes have passed on our clock of Earth's history.
13:4630 million years in real time.
13:50The single most important period in the life of our planet.
13:56The Earth started to recover from its collision with Thea.
14:01And debris from the disaster formed the Moon.
14:05The massive impact very nearly destroyed our planet.
14:11But out of this catastrophe came a new beginning.
14:16It set in motion a chain of events
14:19that would transform the Earth from a vision of hell
14:22to the blue moon.
14:25And it was this new beginning
14:27that would change the course of history.
14:30It would transform the Earth from a vision of hell
14:33to the blue-green oasis we now call home.
14:39The collision was so huge
14:41that it altered the rotation of the entire planet.
14:48To understand how, scientists set out to reconstruct those events,
14:52starting with the moments immediately after the impact.
14:57Ithaca, upstate New York.
15:01Paleontologist Judith Nagel-Meyers
15:04hunts for clues that might reveal
15:06what the Earth was like just after the impact.
15:13No evidence remains on Earth from the period just after the collision,
15:17so scientists are constantly searching for new ways to look back in time.
15:23Nagel-Meyers uses fossilized corals.
15:28This area was once an ancient sea.
15:32The fossilized corals are just 400 million years old,
15:36but they hold a vital clue to what conditions were like on Earth
15:40four and a half billion years ago, when the Moon first formed.
15:44What I personally love about fossils is that
15:47you find them and they open up a window in time.
15:50Just by looking at their remains and their skeletons,
15:53you can reconstruct the environment that was here
15:57long before humans are even on the Earth.
16:02The coral fossils have an unusual property
16:05that allows them to capture a day-by-day snapshot
16:08of conditions on early Earth.
16:12Corals build layers of limestone as shelters,
16:16a new layer for every day of the year.
16:20You can see the same process in every reef, including today's coral.
16:26If you actually look closely at these modern corals,
16:29you can see tiny lines that they built while they're growing.
16:34They're kind of similar like growth rings on trees.
16:38We know nowadays that one of these lines represents a day.
16:43The daily growth layers build up to create a larger annual ring.
16:48If you count these daily growth rings, you can actually,
16:51in modern corals, count 365 growth lines per year.
16:59And that's the key.
17:01The 400 million-year-old fossilized corals
17:04don't have 365 growth lines per year.
17:09They have 410.
17:14When these corals were alive in the ancient oceans,
17:17400 million years ago, a year didn't last 365 days.
17:23It lasted 410.
17:29But whether you measure it in days or hours,
17:32the Earth's orbit around the sun always takes the same amount of time.
17:38A year is constant.
17:42The only explanation for more days in a year
17:45had to be that millions of years ago, each day was shorter.
17:51That means that back in the day when this animal was actually living in the ocean,
17:57that the days had less hours than they have today.
18:05400 million years ago, a day lasted just 21 hours.
18:11And if days were shorter,
18:13then the Earth must have been spinning faster.
18:18Scientists used the rotation rate from 400 million years ago
18:22to figure out how fast the Earth was spinning
18:25just after the planetary collision.
18:284.4 billion years ago, a day lasted just 6 hours.
18:37The massive impact that created our Moon
18:40set the Earth spinning four times faster than today.
18:45It was the first step towards the hospitable Earth we live on today.
18:50But you'd never know it.
18:53The rapid rotation unleashed the worst weather the planet has ever seen.
18:59Megastorms and hurricanes tore across the land.
19:03It looked as though the collision with Theia
19:06had left the Earth an uninhabitable world.
19:1412 minutes past midnight on our clock, 4.5 billion years ago.
19:21Icy comets were smashing in from space.
19:26It was a savage bombardment, but it wasn't a disaster.
19:31In fact, it was a blessing.
19:34The ice melted, and combined with water condensed from inside the planet
19:39created the first oceans.
19:43But the young Earth was still a violent and hostile place.
19:48It was spinning four times faster than today.
19:52Rain and 500-mile-an-hour winds whipped across the surface.
19:57The atmosphere was a lethal cocktail of carbon dioxide and acid rain.
20:04It seemed that there was no way life could ever have started.
20:09Were it not for one thing.
20:13Overhead, the Moon rose.
20:16This was not the familiar Moon we see today.
20:19For a start, it was ten times closer.
20:22It dominated the horizon.
20:24It's another result of that huge collision.
20:27And this time it's good news.
20:33Because the Moon was so much closer,
20:35its gravitational pull on the Earth was much stronger.
20:40And the things it pulled hardest on were Earth's new oceans.
20:49Huge tides ripped across the planet at hundreds of miles per hour.
20:55You might think that made it tough for life to get going.
20:59But you'd be wrong.
21:02It actually helped life on Earth get started.
21:11This is the Bay of Fundy, Canada.
21:14It has the largest tidal range on the planet.
21:18Tides here can reach as high as 50 feet.
21:21It's like a scale model of the huge tides that swept over the early Earth.
21:27Physicist Neil Cummins is here to study what happens when the tide comes in today.
21:33And what that can tell us about tides in our planet's distant past.
21:38What I would expect to see here is a huge wave, maybe five, six feet high,
21:46called a tidal bore.
21:47Cummins believes that due to the Moon's close proximity to the Earth billions of years ago,
21:52the ancient tides would have crusted faster and higher than Fundy's.
21:58He's waiting for the tidal bore,
22:00so he can see first-hand the kind of forces that shaped the ancient landscape
22:05and created the conditions for life to begin.
22:09Right up here, actually, in the middle of the channel, you can start to see the tidal bore.
22:12You can see the wave coming in.
22:14Right up here, actually, in the middle of the channel, you can start to see the tidal bore.
22:16You can see the wave curling over.
22:19You can see the white water.
22:21It's absolutely fascinating.
22:23You can actually start to hear it a little bit.
22:27You have a feeling that there's an action here that you don't see anywhere else.
22:35Should we go and meet it?
22:44Let's go.
23:00Boy, that was something.
23:06One hundred billion tons of seawater rush in and out of the bay every 24 hours,
23:10making the tidal bore at Fundy one of the world's largest.
23:15The rushing waters smash into the edge of the bay.
23:21They rip sand, minerals and other material away from the shore and carry them out to sea.
23:28Cummins believes the erosive action here recreates in miniature
23:32what happened when the huge tides ruled the ancient oceans.
23:37The ancient tides would have been at least a thousand times higher.
23:43A tremendous amount of power in these tides.
23:47But nothing compared to what it was.
23:54This bore is traveling about 12 kilometers an hour.
23:58The ancient tides would have been traveling on the order of 100 to 300 miles an hour.
24:06And they would have gone much farther inland, much faster,
24:11and would have done much more damage.
24:18But did this damage help or hinder the dawn of evolution?
24:23Four billion years ago, when the moon was much closer,
24:27the tides would have smashed inland at hundreds of miles an hour.
24:31Each new tide tore up millions of tons of debris from the land.
24:36When it retreated, it left a devastated coastline.
24:41The young planet was being devoured by its oceans.
24:46And for us living things, that was good news.
24:53Because what the tides stripped from the land, they gave to the oceans,
24:58creating the perfect environment for the emergence of life.
25:02To get life started, you need a huge amount of minerals
25:07in the oceans that are free to mix and interact.
25:11The only way that the earth could have gotten that
25:15was from the huge tides that the moon gave when it was much, much closer.
25:21The tides ripped minerals and nutrients from the land
25:25and mixed them into the oceans, creating a primordial soup.
25:29The seas were now full of crucial chemicals, all mixed together.
25:34Scientists think that chemical interactions in that soup
25:38created the very first amino acids and basic proteins,
25:43the building blocks of life.
25:46From these ingredients, the first primitive cells would eventually emerge.
25:51So a titanic collision that nearly destroyed the planet
25:55So a titanic collision that nearly destroyed the earth
25:59in fact may be the reason all of us are here.
26:03It gave us the moon, and the moon gave us tides.
26:08And without those, life might never have evolved.
26:15If this process hadn't existed,
26:19then there would have been very little erosion
26:22of the ground near the oceans.
26:25It would have been much, much harder
26:28for debris to have gone into the oceans in enough quantity
26:32to allow the primordial soup to have been created
26:36and therefore allow life to have evolved here as early as it did.
26:46The promise of life now rested in the oceans,
26:49in the form of simple strings of molecules,
26:53the precursors of life.
26:56But the world above the surface remained hostile.
27:00The planet was spinning violently, the climate was chaotic,
27:04and the tides too brutal for life to begin.
27:07Unless the moon loosened its grip on the earth,
27:10evolution would stay on hold forever.
27:203.20 a.m. on our clock of earth's history.
27:24Half a billion years have passed since the collision created the moon.
27:30The first building blocks of life have formed deep in the oceans,
27:35thanks to the moon's monster tides.
27:39But the seas were too violent for even single-celled organisms to evolve.
27:45Something must have happened to calm the planet
27:47and allow early life to take the next step.
27:51If it hadn't, we simply wouldn't be here.
28:01This is KwaZulu-Natal in South Africa.
28:05Paleontologist Nora Nofka studies how life got its first toehold.
28:10Here in this ancient gorge,
28:13she's discovered fossils that might hold the answer.
28:16They are some of the earliest forms of life on the planet.
28:20What they reveal is astonishing.
28:23Three billion years ago, when this gorge was part of the seafloor,
28:27the waters teemed with bacteria.
28:30A billion years after the catastrophe that nearly destroyed our planet,
28:34life on earth was in full bloom.
28:37It was really one of the great moments in my career.
28:41We were searching for fossils the whole day long,
28:43and then in the late afternoon,
28:46when the sun was shining in the right angle,
28:48suddenly we saw the fossils popping out everywhere.
28:51It was just unbelievable.
28:54The fossils were the remains of vast colonies of bacteria
28:58that grew in mats in ancient shallow oceans.
29:02And they were some of the first living cells to inhabit the planet.
29:08Their bacteria almost identical, still alive today.
29:14Those are living bacterial colonies.
29:18We term them microbial mats,
29:20and you can easily see why those mats look like little greenish carpets.
29:26They occur today everywhere, the sandy beaches.
29:29The similarities between ancient and modern are striking.
29:35You can see the rock surface is greenish colored,
29:39just as the living microbial mat as well.
29:43If you follow my finger now,
29:45I show you the edge of the fossil microbial mat here.
29:50And here you see the sand underneath.
29:54It's such a microbial mat like this piece here,
29:58but it's fossilized and it's three billion years old.
30:01The rocks all over the gorge were packed with an astonishing diversity of microbial communities.
30:08Ecosystems of bacteria as complex then as they are today.
30:16But the rocks reveal something else.
30:19They show not only when bacterial life took hold,
30:23but also how it became possible.
30:26Etched into their surface is evidence of the ancient seas,
30:31but not the violent oceans left behind by the collision with Theia.
30:35This was calm, shallow water.
30:39I came first here into this outcrop, into the site.
30:42I saw all those different ripple marks and they look just as they do nowadays.
30:47If you walk along a beach, you can see the same structures in the sand.
30:51So the preservation of those structures is just outstanding here.
30:56It looks as if the tide has just gone out,
31:00except these ripples are three billion years old.
31:05The fossilized snapshot of an ancient ocean,
31:09gently lapping the shore with no sign at all of giant tides or hurricane winds.
31:24The site shows that at least three billion years ago,
31:28the living conditions were normal.
31:30This is a peaceful environment here.
31:32So life could evolve.
31:36Something had changed the planet's extreme climate and brutal tides,
31:44making it hospitable for life.
31:47And again that something was the moon and its gravitational effect on the oceans.
31:57The tides, since they started forming, have acted as a brake
32:02to slow the earth's spin.
32:04You can almost think of it as the brakes on a car pressing on the tire
32:10and causing the two to slow down together.
32:13That's what's happening and has happened from the tides.
32:17It's a process called tidal friction.
32:21When the tides and the continents meet,
32:25the water pushing against the land creates friction.
32:28And that friction is literally slowing the earth down.
32:35Over millions of years, tidal friction slowed down the spin of the earth.
32:40As a result, the days became longer and the chaotic hurricane winds subsided.
32:47It was a step in the right direction,
32:50but on its own it wasn't enough to create the calm seas we saw fossilized in KwaZulu-Natal.
32:57The moon was still too close to the earth,
33:01its gravitational pull on the oceans too strong.
33:05For the oceans to calm to a gentle ripple, something major must have happened.
33:11The evidence to what did can be found in NASA's Apollo program,
33:17in the final leg of man's mission to the moon.
33:26The McDonald Observatory in West Texas.
33:30Here, 40 years after man first landed on the moon,
33:34the Apollo mission is still going strong.
33:40NASA engineer Jerry Wyant makes a daily commute to his laser telescope
33:46to continue the job begun by astronauts decades ago.
33:50His mission, to measure the moon's distance from earth.
33:55We're the last living piece of the Apollo project.
34:00Most of the public thinks that all the Apollo projects, they're dead and gone.
34:04And so they're surprised when I tell them what I do and send a laser to the moon.
34:09When astronauts landed on the moon, they left behind the American flag and something else.
34:15Reflectors.
34:18Almost daily, Jerry Wyant and his colleague aim their laser at one of the lunar reflectors.
34:24They're measuring the precise distance between the moon and the earth.
34:31This is a 1 billion watt laser.
34:35We direct it at the reflector on the moon,
34:38and we measure how long it takes for this light to go from here to the moon.
34:42And that's our data.
34:56The laser measures the time it takes light to travel to the moon and back,
35:01to a trillionth of a second.
35:04But first, they've got to find the reflector.
35:10Each panel is about the size of this map right here.
35:15So, if you think about it, we're trying to hit something this size,
35:20about 240,000 miles away.
35:23It's not easy.
35:24They need a clear night.
35:26Then they need to locate the target.
35:34Yeah, they all look alike, don't they?
35:36Yeah, it's easy to get lost.
35:38Sometimes it takes up to four hours to pinpoint the reflector.
35:43Well, that right there, that would be the reflector on the moon, right there.
35:49Tonight, the laser beam takes 2.3967 seconds
35:54to travel to the moon and back.
35:57It's a long time.
35:59It's a long time.
36:01It's a long time.
36:03It's a long time.
36:05It's a long time.
36:07It's a long time.
36:09It's a long time.
36:10It's a long time.
36:12It's a long time.
36:14When I see the moon in the sky, instead of thinking romantic thoughts,
36:18I think, gee, I hope the laser is working okay.
36:21It may not be romantic, but it is amazing.
36:25Each year, Wyant's laser beam takes a little longer to bounce back,
36:30because each year, the moon is a little further away.
36:34One of the reasons that scientists want our data
36:37is to confirm their suspicion that the moon really is moving away from the Earth.
36:42And they've used our data to report back to us
36:45the value of that, in fact, is yes, it really is.
36:51The moon is spinning away from us by one and a half inches per year.
36:56And it's this that holds the key to understanding
37:00why the oceans calmed and life emerged.
37:03Three and a half billion years ago,
37:05the moon was only 15,000 miles from Earth,
37:09resulting in mountainous tides.
37:12But these tides were pushing the moon away.
37:16They were so huge, they had a gravitational pull of their own.
37:21And that began to affect the moon that had created them.
37:25The gravity from the water is acting back on the moon,
37:30which raised the water up in the first place.
37:33And this water is pulling the moon forward, giving the moon energy.
37:39As the Earth spins, it slings the moon further away,
37:43like an athlete throwing a hammer.
37:47You can think of the Earth-moon system as waltzing together.
37:52As the moon creates the tides on Earth,
37:55the Earth is slowing down.
37:57And the tides are causing the moon to gain energy and spiral away.
38:04The two have been doing this dance for four and a half billion years.
38:10So the catastrophe that nearly ripped our planet apart
38:14before life even started actually ended up making life possible.
38:21Violent tides filled the sea with vital chemicals.
38:24Then the Earth's spin slowed, and the moon drifted away.
38:30The nutrient-rich seas calmed, and life got started.
38:37But just as life started to flourish, it faced a new disaster.
38:42It was a catastrophe that would wipe out much of the life on the planet.
38:47But without it, we would not be here.
38:50But without it, we would not be here.
38:54Some bacteria started to release a deadly poisonous gas.
39:01Oxygen.
39:088.10 a.m. on our planetary clock of Earth's history.
39:13Over a billion years since a violent collision with another planet
39:17came close to destroying the Earth.
39:28The impact created the moon and triggered a chain of events
39:32that led to bacterial life taking hold in the seas.
39:39Some of these bacteria developed a new process
39:42that would affect all life on Earth.
39:47It would wipe out many species.
39:50But without it, complex life wouldn't be here at all.
40:11This barren landscape is the high desert in northern Mexico.
40:16It's a window into the past.
40:19It's one of the only places in the world
40:22where we can get a glimpse of what the Earth might have been like
40:25two billion years ago.
40:28A planet at the crossroads of evolution.
40:33Biologist Janet Seifert studies the bacteria that live in these pools.
40:38They give her a unique insight
40:40into how ancient bacteria changed the Earth forever.
40:44You can walk out to the pools and you can see evidence
40:47of microbial communities with the naked eye.
40:50Now that's very similar to what early Earth was like.
40:53Early Earth was certainly dominated by bacteria.
40:55There were no large animals or plants.
40:57So we can use this as a proxy for early Earth.
41:02Seifert is interested in these curious lumps of limestone.
41:14So this is actually quite remarkable.
41:17I know it doesn't look remarkable.
41:19This looks like just a rock
41:21found in the bottom of this little river here.
41:23But this is actually a complex community of microbial life.
41:27These lumps are called stromatolites.
41:30They're made of bacteria that deposit limestone,
41:33building up to form these mini-reefs.
41:39It was organisms almost identical to these
41:41that populated the early Earth.
41:45These fossilized stromatolites
41:47in the Flinders Ranges in southern Australia
41:50are three billion years old.
41:52There's virtually no difference between these
41:55and the structures Seifert finds in Mexico today.
42:00Each stromatolite contains millions of blue-green organisms
42:04called cyanobacteria.
42:06And three billion years ago,
42:07their ancestors evolved an ingenious means of obtaining energy.
42:13One branch of bacteria actually learned how to do one thing.
42:18They just used the sunlight for energy.
42:21But as it turned out, when they did that,
42:24they did it in such a way that they could split water
42:27and create and give off as a byproduct
42:30something they didn't want, oxygen.
42:32These ancient microscopic cyanobacteria
42:35evolved a chemical process called photosynthesis.
42:40It converts sunlight into chemical energy,
42:43with oxygen as a byproduct.
42:51It was a biological revolution,
42:54and it changed the planet forever.
42:57Cyanobacteria pumped oxygen into the oceans,
43:00then the atmosphere.
43:01If they hadn't evolved photosynthesis three billion years ago,
43:05there would be almost no oxygen in today's atmosphere at all.
43:10Without cyanobacteria, we could never have evolved.
43:14They are the reasons why we breathe oxygen today.
43:18Once the cyanobacteria figured out
43:21how to produce oxygen as a byproduct,
43:24it changed our planet forever.
43:27It changed the way biology was going to evolve.
43:29And it changed the atmosphere completely.
43:32The production of oxygen three billion years ago
43:35changed the planet forever,
43:37and the bacteria that started the process
43:40are still doing it today.
43:42I remember the first time I was swimming around down here,
43:46and you could see the small little bubbles
43:49accumulating underneath the ledge of the stromatolite.
43:53It was quite amazing to think that that process,
43:56that we were actually visualizing in that way,
43:59is what's creating the atmosphere today.
44:03And those ancient cyanobacteria
44:06are the ancestors of every plant in the world today.
44:10Photosynthesis was incredibly successful.
44:13The bacteria flourished and evolved.
44:17We always think about microbes being something bad
44:20and giving you strep throat.
44:22But if bacteria hadn't been able to harm us,
44:24if bacteria hadn't been able to harness the sun
44:27and then as a byproduct produce oxygen,
44:30you and I probably wouldn't be here now,
44:33because it's what allowed complex animal evolution to occur.
44:38But for those organisms unable to adapt,
44:42oxygen was a death sentence.
44:45When it first happened,
44:48that byproduct, oxygen,
44:51was poison to most of the life on the planet.
44:54It was a devastating thing that happened.
44:57All of life had to actually acclimate
45:00to the fact that there was oxygen in the atmosphere.
45:04But a few bacteria learned how to handle it.
45:08And it's those survivors that led to things like us.
45:16Actually, I feel pretty lucky
45:19because that bad poisonous gas
45:21that cyanobacteria had as a byproduct,
45:24if it hadn't accumulated in the atmosphere,
45:27then I wouldn't be here.
45:30So as far as one of the major biological innovations
45:34that happened in 3.8 billion years,
45:37it has to be up at the top of the list
45:40of one of the best ones for us as humans.
45:43By 8.12 in the morning on our clock,
45:47the atmosphere had oxygen
45:49and the oceans were teeming with bacteria.
45:52Evolution, life, had begun.
45:56And it all started with a catastrophe.
45:59It all seems so logical, so inevitable.
46:03In fact, it's anything but.
46:06That impact is perhaps the only reason life ever evolved.
46:10But if it had been even slightly different,
46:13there might be no one here at all.
46:16If you consider all the different types of impacts
46:20that could have happened and have left Earth-Moon systems
46:23that weren't nearly as habitable as our own,
46:26it's really quite something to think that
46:29we got lucky in a sense.
46:32And that's the point. We did get lucky.
46:36Not just with that first huge impact,
46:39but in countless ways over billions of years.
46:42What we're realizing now is that
46:44catastrophes have played a much larger role
46:47in the evolution of life on Earth than anybody believed earlier.
46:53You have to realize that we are at the end
46:56of this long chain of unique events.
46:59Had they played out differently,
47:02this guy wouldn't be sitting on this rock here.
47:05There's only one conclusion.
47:08We're not here because we did something right.
47:11We're here because we're lucky.
47:14Theodora Thea was just the first
47:17of many random rolls of the dice.
47:20It really makes you think about this
47:23completely unique sequence of random events
47:26that were all necessary to give us the Earth we know today.
47:30And if any one had just been a little different,
47:33the whole world around us would be different.
47:36We wouldn't even be here.
47:39It gives you an appreciation that a catastrophe
47:41like this could have happened.
48:11You