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00:00John Goodrick was a man who has permitted only the briefest glimpse of the stars, and
00:25yet it could be said that he made one of the greatest discoveries of all.
00:33He had been left completely deaf by a childhood illness, and maybe that's why he looked so carefully.
00:43On a clear summer night in 1784, he went outside to see if a particular star was still doing
00:50something that mystified him, something that no other astronomer had ever reported before.
01:00Goodrick couldn't believe his own eyes.
01:03The star, called Beta Lyrae, changed regularly in brightness over a very brief period of time,
01:09only days.
01:12What could possibly make a star do that?
01:18Even more surprising, Goodrick found that he could predict its variations with high accuracy.
01:25What could cause such a change in a star's brightness?
01:29None of the scenarios that came to mind explained the evidence before him.
01:36And then he thought of another possibility.
01:44Suppose there was something orbiting Beta Lyrae that eclipsed the star on a regular basis.
01:54But what could it be?
02:03The world, perhaps?
02:22How about a trillion?
02:23What could it be?
02:25The world, perhaps?
02:29I'm so sorry.
03:34When John Goodrick's discovery came to the attention of the prestigious British Royal Society in 1786, he was immediately made a member.
03:45Word of this honor never reached him.
03:49Days later, he was dead of pneumonia.
03:52He was only 21.
03:56It would be 150 years before another astronomer would solve Goodrick's mystery and, in the process, change our cosmos forever.
04:12Even as a child, Gerard Peter Kuyper could see farther than anyone else.
04:19He saw stars too distant and too faint for others to find without a telescope.
04:25This was in the Netherlands more than a century ago.
04:30Back then, the son of a poor tailor could not hope to become an astronomer.
04:35But the boy would not be stopped.
04:38Back then, astronomers thought that the cosmos consisted of only a handful of planets, those of our own solar system.
04:46The great multitude of other stars were just barren points of light that had never given birth to worlds.
04:55We on Earth could still feel special.
05:00Our star system, the scientists told us, was the rarest of all.
05:04One blessed by worlds and moons.
05:07Kuyper yearned to know how our sun and its planets came to be.
05:21And made his way to the University of Leiden, where he quickly distinguished himself.
05:28He was invited to join the dynamic astronomical community in the United States.
05:33But Kuyper had rough edges.
05:36He was argumentative.
05:37And easily drawn into conflict with his colleagues.
05:41The prospect of directing a remote observatory, far away from the capitals of scientific culture, must have appealed to him.
05:48And besides, you could see the stars better there than just about anywhere else.
05:55Kuyper was given an appointment at the McDonald Observatory, situated in a corner of West Texas.
06:01At the turn of the century, it had been discovered that half the visible stars were really gravitational pairs.
06:11Most binary stars are like twins, forming from the same womb of gas and dust.
06:17Others come of age separately and become gravitationally involved with each other later in their development.
06:23And the other half remain single throughout their lives.
06:27Kuyper chose to concentrate on the binary stars.
06:31He wondered if they could shed light on the way that the planets in our solar system formed and came to be gravitationally bound to our sun.
06:40Kuyper looked at the very same star that had baffled John Goodrich 150 years before.
06:56But Kuyper was looking at it with a much bigger telescope.
07:01And Kuyper was armed with an awesome power that didn't exist in Goodrich's time.
07:07Spectroscopy.
07:09Spectroscopy is a way to dissect the light of any single star to find its particular atomic and molecular composition.
07:17Kuyper looked at the spectrum produced by the light of beta-lyrae and saw that, as with all stars, there was plenty of hydrogen and helium.
07:25But there was also iron, sodium, and silicon.
07:30So far, no surprises there.
07:32Now, here comes the twist.
07:35Bright lines?
07:36Where were those bright lines coming from?
07:39At that time, no astronomer understood why bright lines would appear in the spectrum of a star.
07:45Kuyper leapt to the conclusion that the two stars were so close that they were exchanging matter.
07:52Super hot gases that would produce such a signature.
07:55In trying to understand what he had seen that night, Kuyper discovered and named the most intimate stellar relationship in the cosmos.
08:05Stars that are physically locked in everlasting oneness, bound together by gravity, and a bridge of fire made of star stuff.
08:15A bridge 8 million miles long.
08:23Connecting two stars, one three times more massive than our sun, the other 13 times greater still.
08:31A contact binary star system.
08:37Why aren't they round like our own star?
08:40They are so close to one another, tidal forces of gravity pull them together and stretch them into flaming teardrops.
08:48The beta-lyrae system is about a thousand light years from Earth.
08:55The largest telescopes of the mid-20th century were just not powerful enough to resolve them as individual stars.
09:03You needed that new power of spectroscopy to disentangle them.
09:06Kuyper imagined how the formation of the contact binary star system could have happened.
09:14He deduced that they were formed when a vast cloud of gas and dust became so dense that gravitational whirlpools formed.
09:23In thinking about these contact binaries, Kuyper couldn't help but wonder if any of these stellar courtships ever failed to catch fire.
09:38Kuyper asked himself, was our world, our moon, and all the planets of our solar system nothing more than a failed binary star system?
09:48And if that's how our solar system was created, had the same thing happened around other stars throughout the cosmos?
10:03Gerard Kuyper had a special power.
10:06He could see farther than anyone else.
10:09He was the first to envision the universe we now live in.
10:12Not a barren vastness meagerly dotted by childless stars, but one overflowing with possible worlds, countless planets and moons.
10:25In 1949, Kuyper astonished the world by declaring that our solar system was not so special after all,
10:33that every other star had its own family of worlds.
10:39A world, perhaps?
10:41But science wasn't ready for that universe.
10:47It wasn't even ready to take its first baby steps off the planet.
10:52Why not?
10:53Science was carved up into little kingdoms, the various scientific disciplines.
10:58And scientists of one discipline didn't collaborate with anyone from another.
11:03But this had to change for us to venture beyond Earth.
11:06It all came to a head in a feud between Kuyper and another great scientist.
11:13Like two stars of a contact binary system, they could not disengage.
11:18But despite their loathing for each other, they managed to create a new kind of science.
11:23And they pioneered the space age, mentoring its greatest visionary and voice.
11:29Sometimes, the cosmos just barges right in and breaks down your door.
11:54Like tonight.
11:57What's going on here?
11:59Our planet is passing through the epic remnants of a comet.
12:03A debris field millions of miles long.
12:05That's why it looks like it's raining stars tonight.
12:09But they're not stars at all.
12:11Just bits of rock and ice burning up in Earth's atmosphere.
12:15It's called a meteor shower.
12:17And this one happens at the same time every year.
12:21Why?
12:22Because it takes a year for Earth to orbit the sun and return to that same place where the comet streaked by so long ago.
12:29So, that's what a year is.
12:32This could be a piece of that comet.
12:36Or possibly a fragment of an asteroid.
12:39It came from another world.
12:41A leftover from the creation of our solar system.
12:45But how to understand it?
12:48Well, back in Gerard Kuyper's time, during the middle of the 20th century,
12:51it depended on what kind of a scientist you were.
12:54The geologists would bring their hammers and break the sucker apart
12:59and look at its dust under a microscope to study its crystalline structure.
13:04It was their way of finding out which missing piece in this puzzle of Earth the meteorite could provide.
13:10The chemists were searching for the same answers.
13:14But they would drop it in acid to see if it could be transformed from one compound into another.
13:19Torturing it to see if it would give up its secrets about nature.
13:24The chemists would want to see it at its most naked.
13:36Stripped down to its mass, its density, its hardness, its resistance to heat.
13:41The biologists wouldn't even stop to pick it up.
13:47Back then, they would have walked right by it.
13:50Because they didn't think there was any chance
13:52that a meteorite from space had anything to do with them.
13:56Life could only be from one place.
14:00Right here.
14:02Earth.
14:02And you want to know the craziest thing?
14:10Back then, the astronomers would have walked right by it, too.
14:15Their sights were focused on the distance.
14:17And we can't really blame them.
14:19What was happening in astronomy back then?
14:22Big ideas about things far beyond our solar system.
14:25Einstein's theory of relativity, with its vision of riding a light beam across the cosmos.
14:32And Edwin Hubble's discovery that the universe was expanding.
14:36The distant galaxies were flying away from one another.
14:39That's what raised goosebumps.
14:41Not looking at a dumb rock lying in your own backyard.
14:45Studying the planets, moons, comets, and meteors of our own tiny solar system seemed like Little
14:51League, until Kuiper dared to venture into territories off-limits to astronomy.
14:58Night after night, he would stay up here, a virtuoso playing the 45-ton instrument like
15:04a violin, searching the solar system for clues to its origin.
15:09A mystery that he alone recognized was insoluble, without the cooperative enterprise of all the
15:16scientific disciplines.
15:17But the scientists didn't know they needed one another.
15:21There wasn't a single university department where scientists of multiple disciplines could
15:26study planetary astronomy.
15:28So here, in the middle of nowhere, in a corner of West Texas, Kuiper conducted his one-man exploration
15:38of the solar system.
15:47He looked at Titan, one of Saturn's moons, and discovered that it had an atmosphere.
15:58It was thick with methane.
16:01A point of light in the sky had suddenly become a real place.
16:05Kuiper used the spectroscope to probe the acrid clouds in the upper atmosphere of Jupiter, to
16:12see what they were made of, their chemical and atomic structures.
16:16And when he looked at the red planet Mars, he found carbon dioxide in its atmosphere, and
16:21he wondered, am I looking at my planet's future, or its past?
16:27But to some people, Kuiper was doing nothing more than trespassing, butting into chemical
16:34matters where an astronomer had no business.
16:37Harold Urey was a chemist.
16:40Like Gerard Kuiper, he also had to fight his way into science.
16:45Urey's family was poor, like Kuiper's.
16:48So he took a job teaching grammar school in a mining camp in Montana.
16:55The parents of one of his students urged him to find a way to get to college.
17:01Harold Urey took that advice all the way to a Nobel Prize in chemistry.
17:08By 1949, he was riding high.
17:12A distinguished professor at the University of Chicago.
17:14Then and now, one of the world's great capitals of science.
17:20But when Urey read his morning paper, something began to curdle inside him.
17:25A rising resentment.
17:27First, a pang at a fellow scientist's heightened celebrity.
17:32Well, that was normal.
17:34Then he got to the part about the origin of the planets.
17:38He was offended that an astronomer was making pronouncements about the chemical nature of
17:43the solar system.
17:44That was his turf.
17:50Scientists are human.
17:52We're primates.
17:54We carry the same evolutionary baggage as everyone else.
17:58Kuiper and Urey were two alpha males who chose scientific argument as their weapon of combat.
18:04And the two men fought over a single hostage.
18:10A young student.
18:11When Carl Sagan was a kid, he lived here in a small apartment in Brooklyn.
18:20In the mid-1940s, he made this drawing, filled with predictions, that is now in the U.S. Library of Congress.
18:33In the mid-1940s, he made this drawing, filled with predictions, that is now in the U.S. Library of Congress.
18:47In the mid-1940s, he made this drawing, filled with predictions, that is now in the U.S. Library of Congress.
18:52In an era where life here was in the last seconds of its four-billion-year captivity,
18:57on Earth, he dreamed of going to the planets, and even going to the planets.
19:03But he didn't want to just go in his imagination.
19:32He wanted to really go.
19:35He wanted to know what those worlds were really like.
19:39And he knew that the only way to do that was to become a scientist.
19:44The boy would come under the wings of the two warring giants.
19:49As much as they hated each other, he loved them both.
19:53Together, the three of them would tear down the walls between the sciences.
19:57And the boy would tear down the tallest wall.
20:02The one between science and everyone else.
20:05Do something for me.
20:15I need you to pretend that we live in a time before any spacecraft or human had ever left Earth.
20:22No one had ever seen our world from space.
20:25The most extravagant fantasies of the greatest artists were no match for what was coming.
20:31This is how one of them imagined Earth must look from space.
20:36And then, in one instant, on a single day, everything changed.
20:43This is how Mother Earth looked when she was naked.
20:48Before nearly 5,000 satellites were in orbit around her.
20:53Before anyone had ever counted backwards from ten.
20:57One, two, three, two, three, two, one.
21:14One, two, three, two, one, one, five, seven, six, four, one.
21:27Two, three, one, four, five, seven, seven, eight, seven, ten, seven, eight, eight, seven, eight, nine, ten.
21:31On October 4th, 1957, the Soviet Union became the first nation to dip its toe into the shallows
21:54of the cosmic ocean. It launched Sputnik 1, a simple radio transmitter that circled Earth
22:02every 96 minutes. All over the planet, people came outside to find this new light in the sky,
22:16a man-made moon. Nothing could stop us from achieving our most daring dreams.
22:26Think of it. Something we made was a new light in the night sky. Something like a star.
22:35As this was happening, the boy was becoming a scientist, and this new knowledge moved him
22:42as nothing before had. All he could think was that he wanted to share it with everyone on Earth.
22:50But that kind of thing was frowned upon by scientists. They saw themselves as being members of an elite
22:57club. In 1950, when Carl Sagan was just a high school student, he wrote a paper that earned him
23:04an invitation to work in the lab of H.J. Mueller, who had won the Nobel Prize for his discovery
23:10that radiation causes mutations in genes. By the time Carl got to the University of Chicago,
23:17he was beginning to make a name for himself, and Harold Urey chose to mentor him. Urey, the chemist,
23:25was now doing the thing that he had resented Kuiper for, trespassing on the turf of another
23:30scientific discipline. This time, it was biology. Urey and his team wanted to know how life could have
23:38originated from lifeless matter. Working with another student of his, Stanley Miller, Urey designed
23:47an experiment to simulate the chemical conditions of the atmosphere on the early Earth. They wanted
23:53to see whether those basic chemicals could have led to amino acids, the building blocks of life.
23:59Could lightning have provided the spark that awakened matter into life?
24:08And if it could happen here on Earth, where else could it have happened, Carl wondered.
24:14When he wrote a paper speculating on that possibility, Urey responded harshly. He scolded his apprentice
24:24for venturing beyond his expertise. But still, Carl loved Urey because he knew that this toughness
24:31would make him a better scientist. In the summer, Carl traveled to the enemy camp, to McDonald Observatory,
24:39to observe Mars with Gerard Kuiper, the only planetary astronomer on Earth. That year, Mars was in a favorable
24:48opposition to Earth. The two worlds would be the closest they'd been in 30 years. But the weather
24:56didn't cooperate. Not in Texas, but on Mars. A global wind-blown dust storm there prevented Kuiper and Sagan
25:05from seeing anything new. Instead, they spent those summer nights talking of many things. The older man
25:12taught the young scientist the most efficient ways to test his bold new ideas. They fantasized about what
25:19those possible worlds circling other stars might be like. These two fearless scientific imaginations
25:26ventured throughout the galaxy all that summer. The gates to the Wonderworld were swinging open for Carl.
25:33And all of this was happening as we were reaching beyond the planet for the very first time.
25:48Soviet Union Sputnik scared the hell out of the United States. The Cold War was a contest between dueling
25:54ideologies about property and freedom. When the Russians got there first, it seemed to reflect badly on our
26:02worldview. And if they could send an object into orbit above our heads, we could no longer protect our
26:09skies. Suddenly, there was a new delivery system for nuclear weapons. Nowhere on Earth could be
26:15safeguarded against espionage or attack. We needed a space program of our own. The National Aeronautics and Space
26:23Administration was founded a year after Sputnik in 1958. Science was at last ready to see Earth as Kuiper had
26:32been seeing it for years as a planet. What a concept. It may seem obvious to us now, but in a time of
26:40fanatical fight-to-the-death nationalism, it was a thunderbolt. But Kuiper's feud with Yuri still raged, even as they both
26:49took leadership roles in the fledgling space program. Karl continued ferrying between their
26:55warring labs. The enmity between the two men was emotionally so corrosive that he said at the time
27:02he felt like the child of divorced parents, and he was the only bridge left between them. Yuri fought for
27:09NASA to go to the moon. Among his reasons was a desire to know, at last, how the solar system formed.
27:24Kuiper predicted what it would be like when we got there. That when we stepped down on the lunar
27:29surface for the first time, it would feel like walking on crunchy snow.
27:33The moon is a silent world because it has no atmosphere to carry sound waves. But Neil Armstrong
27:42later said that he felt Kuiper's crunchy snow when he stepped down onto the surface for the very first
27:48time. Some of the things the wanderers left behind.
28:01Thanks to Yuri and Kuiper, Karl Sagan was part of this great adventure. He was living his most
28:07extravagant childhood fantasies. He briefed the Apollo astronauts before they left for the moon,
28:14and he was there when scientists first met to evaluate the information gained from the dawn of space
28:20exploration. For the first time ever, the biologists, the geologists, the astronomers, the physicists,
28:28the chemists were all talking to one another. Actually, mostly shouting. The young Karl Sagan
28:36stood up at one of their first joint scientific meetings and said,
28:40hey guys, we're the first generation of scientists to receive these riches. We're in this together.
28:48He set a tone for planetary science that still holds today. He edited the first modern
28:55interdisciplinary journal for researchers studying the worlds of the cosmos, Icarus, which continues to
29:02this day. And he did something else. He started a lifelong campaign to bring the revelations of
29:09science to everyone. And he was one of a handful of scientists who made the search for possible
29:15worlds, for extraterrestrial life, and for intelligence, respectable scientific pursuits.
29:22We've only been hunting for new worlds for a few decades, but we've already discovered many thousands of them.
29:29We think some of them are hospitable to life, and at least a dozen of them are earth-like.
29:41What will they be like?
29:42Carl Sagan wanted to liberate his scientific imagination from the single example of life that we know,
30:08earth life. He envisioned what the life of another very different world would be like.
30:14Sagan collaborated with fellow astrophysicist Ed Salpeter in the design of plausible ecological
30:21systems for life in the roiling clouds of Jupiter. The challenge was to imagine such life forms without
30:29violating the laws of physics, chemistry, or biology. Is life so tenacious that it could even make a home
30:38in this storm of hydrogen, helium, water, ammonia, and methane? There's no accessible solid surface.
30:47It's just this thick, cloudy atmosphere in which organic molecules are falling like manna from heaven.
30:55Like the products of Harold Urey and Stanley Millard's laboratory experiment on life's origin.
31:00However, this environment poses a problem for life. The atmosphere is turbulent and deep down
31:07it's very hot. An organism must be careful that it's not carried downward to the hell below.
31:13One way to make a living under these conditions is to reproduce before you sink and get fried.
31:21Your only hope is that convection will carry some of your offspring to the higher and cooler layers of
31:27the atmosphere. Such organisms could be very small. Sagan and Salpeter called them sinkers.
31:40But you could also be a floater. A vast hydrogen blimp, pumping helium and heavier gases out of your
31:46interior and retaining only the lightest gas, hydrogen. Sagan and Salpeter reasoned that like a hot air balloon,
31:55you'd stay buoyant by keeping your interior warm using energy acquired from the foods you eat.
32:01A floater must eat organic molecules or make its own food from sunlight and air as plants do on earth.
32:10The bigger a floater is, the more efficient it will be up to a point.
32:15Floaters would be immense, several kilometers across. Enormously larger than the greatest whale that ever was.
32:25Beings the size of cities. The floaters may propel themselves through the planetary atmosphere
32:31with gusts of gas, like a ramjet or rocket. Sagan and Salpeter imagined them arranged in great lazy herds,
32:41for as far as the eye could see. The patterns on their skin are adaptive camouflage, implying that they
32:49have problems too, because there is at least one other ecological niche in such an environment.
32:54Hunters. Hunters. Hunters are fast, maneuverable.
33:12Hunters eat the floaters, both for their organic molecules and for their store of pure hydrogen.
33:24Hunters. Hunters. Hunters. Hunters. Hunters. Hunters.
33:43There cannot be very many Hunters because if they consume all the floaters,
33:48the Hunters themselves will perish.
33:54When scientists of the 21st century tested Sagan's imaginary life forms against what
34:09they knew of life, they realized that the concept of a habitable zone had to be expanded.
34:16It moved into the cloud tops of gas giants and the subsurface oceans of ice worlds and
34:22places we've yet to imagine, of all those worlds, of all those stars, one must have been first.
34:36Come with me to the oldest world we know.
34:39We're in a globular cluster, a densely packed ball of a million stars called M4, on the
34:54outskirts of the Milky Way galaxy.
34:58When pulsars, rapidly rotating neutron stars, were first discovered, scientists wondered
35:03if they were a sign of intelligent life, because of the regularity of their radio signals.
35:11Once upon a time, this star was a blue supergiant.
35:14But after a few million years, it ran out of fuel, went supernova, then collapsed into this
35:19ball of neutrons, no larger than a small town.
35:24Its nearby companion, a white dwarf star, another burned out stellar corpse, orbits only a few
35:29million miles away.
35:32That's not why we've come here.
35:34We've come in search of the oldest known planet in the cosmos.
35:40The cosmos was young when this star, a white dwarf, was born, 12.7 billion years ago.
35:47The star was single then, long before it was captured by the pulsar.
35:51It gave birth to a world.
35:53That world is out here somewhere, taking 100 Earth years to orbit these two shrunken stars.
36:01The fact that it exists bodes well for those who dream of virtually infinite possible worlds.
36:08If it formed less than a billion years after the cosmos itself, then stars started fostering
36:14planets soon after the beginning of time.
36:18Nurturing worlds is what stars do.
36:24And what will the fate of this oldest of planets be?
36:28Sorry to say, it's a lonely one.
36:31Sometime in the next billion years, the two stars will be gravitationally ambushed by a
36:36third.
36:41A red dwarf star will come barreling into their vicinity.
36:49Its gravity will send this ancient world careening out of its system and into the lonely dark between
36:56the stars, a rogue planet doomed to wander, a never ending oblivion.
37:04But there are also homes away from home that call to us, illuminated and warmed not by one star, but three.
37:12I want to take you to Gliese 667, a triple star system with six worlds, three of them enough like Earth to hold the promise of life as we know it.
37:24The stars A and B are both a little smaller than our sun.
37:43sun this pair of orange dwarfs orbit each other star c orbits them both it's a red dwarf they're
37:54the most common kind of star in the galaxy as many as 80 percent of all the stars in the cosmos
38:01may be red dwarfs they consume their hydrogen fuel slowly so they last longer more massive stars like
38:10blue giants maintain such high pressures that they burn out quickly
38:27this outermost world of the glisa 667 system is four times the size of earth but it's too far from its
38:35stars to have liquid water on its surface that doesn't mean it's lifeless we don't yet know
38:41enough about life to say what might be going on beneath its frozen shell we haven't yet reached
38:47the habitable zone of this star system getting closer but not there yet this even larger world
38:55is impressive but still just outside that region considered to be hospitable to life
39:01and to the human scientific imagination
39:08now this is more like it the kind of atmosphere that promises life is here
39:31so
39:38so
39:40I don't know.
40:10I don't know.
40:40I don't know.
41:10I don't know.
41:41We haven't even begun to get to know all the living things on this tiny world.
41:46Think of all the possibilities, the different kinds of life there must have been and are and will be in the cosmos.
41:54Thanks to Gerard Kuiper, Harold Urey, and so many other scientists, we now know that it takes just a few million years for stars to evolve and planets and moons to coalesce out of gas and dust.
42:07In other words, a solar system.
42:11It's a long period of gestation, but far from rare.
42:24In our own galaxy, it happens about once every month.
42:29In the observable universe, which we now think contains as many as a trillion galaxies, containing some 200 million trillion stars, a cosmos of 200 million trillion stars.
42:45A thousand solar systems may be forming every single second.
42:51That's a thousand new solar systems right there.
42:54A thousand new solar systems.
43:00A thousand new solar systems.
43:02A thousand new solar systems.
43:04There's thousands of souls.
43:06There's thousands of souls.
43:08Thousands of souls.
43:34The End