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00:01The cosmos is all that is, or ever was, or ever will be.
00:09Come with me.
00:12A generation ago, the astronomer Carl Sagan stood here and launched hundreds of millions of us on a great adventure.
00:20The exploration of the universe, revealed by science.
00:24It's time to get going again.
00:26We're about to begin a journey that will take us from the infinitesimal to the infinite.
00:33From the dawn of time to the distant future.
00:36We'll explore galaxies and suns and worlds.
00:40Surf the gravity waves of space-time.
00:43Encounter beings that live in fire and ice.
00:47Explore the planets of stars that never die.
00:50Discover atoms as massive as suns and universes smaller than atoms.
00:57Cosmos is also a story about us.
01:01It's the saga of how wandering bands of hunters and gatherers found their way to the stars.
01:07One adventure with many heroes.
01:11Many heroes.
01:22To make this journey, we'll need imagination.
01:25But imagination alone is not enough.
01:27Because the reality of nature is far more wondrous than anything we can imagine.
01:37This adventure is made possible by generations of searchers strictly adhering to a simple set of rules.
01:43Test ideas by experiment and observation.
01:48Build on those ideas that pass the test.
01:51Reject the ones that fail.
01:53Follow the evidence wherever it leads.
01:56And question everything.
01:58Accept these terms, and the cosmos is yours.
02:02The cosmos is yours.
02:03Now, come with me.
02:07Come with me.
02:08Come with me.
02:09Come with me.
02:11Come with me.
02:12To be continued...
02:42To be continued...
03:12To be continued...
03:42To be continued...
04:11To see where we are in space...
04:13Just look out the front window...
04:19In the dimension of time...
04:21The past lies beneath us...
04:23Here's what Earth looked like...
04:27250 million years ago...
04:29If you want to see the future...
04:35Look up...
04:37And this is how it could appear...
04:39250 million years from now...
04:43If we're going to be venturing out...
04:45Into the farthest reaches of the cosmos...
04:47We need to know...
04:49Our cosmic address...
04:51Is the first line of that address...
04:53Is the first line of that address...
05:01We're leaving the Earth...
05:17The only home we've ever known...
05:19For the farthest reaches...
05:21Of the cosmos...
05:23Our nearest neighbor...
05:29The Moon...
05:30Has no sky...
05:31No ocean...
05:33No life...
05:35Just the scars...
05:37Cosmic impacts...
05:39Our star...
05:53Powers the wind...
05:54And the waves...
05:55And all the life...
05:56On the surface of our world...
05:57The Sun...
05:59Holds all the worlds...
06:00Of the solar system...
06:01In its gravitational embrace...
06:03Starting with Mercury...
06:24To cloud-covered Venus...
06:26Where a runaway greenhouse effect...
06:28Has turned it into a kind of hell...
06:38Mars...
06:39A world with as much land...
06:41As Earth itself...
06:56A belt of rocky asteroids...
06:59Circles the Sun...
07:00Between the orbits...
07:01Of Mars and Jupiter...
07:15With its four giant moons...
07:16And dozens of smaller ones...
07:18Jupiter...
07:19Is like its own little solar system...
07:21It has more mass...
07:23Than all the other planets...
07:24Combined...
07:36Jupiter's great red spot...
07:40A hurricane...
07:41Three times the size...
07:42Of our whole planet...
07:43That's been raging...
07:44For centuries...
07:45The crown jewel...
07:46Of our solar system...
07:47Saturn...
07:49Ringed by freeways...
07:50Of countless orbiting...
07:51And slowly tumbling snowballs...
07:53Every snowball...
07:54A little moon...
07:55Every snowball...
07:56A little moon...
07:57A little moon...
07:58Every snowball...
08:01A little moon...
08:03A moon...
08:04Cain...
08:05UCI...
08:06A new snowball...
08:07A new moon...
08:08A new moon...
08:09A new moon...
08:10The crown jewel...
08:11Of our solar system...
08:12The crown jewel...
08:13Of our solar system...
08:15Saturn...
08:16Ringed by freeways...
08:17Of countless...
08:18Orbiting...
08:19And slowly tumbling...
08:21Snowballs...
08:22Every snowball...
08:23A little moon...
08:25Uranus.
08:55And Neptune, the outermost planets, unknown to the ancients and only discovered after the invention of the telescope. Beyond the outermost planet, there's a swarm of tens of thousands of frozen worlds.
09:25And Pluto is one of them.
09:34Of all our spacecraft, this is the one that's traveled farthest from home.
09:52Voyager 1.
09:57She bears a message to a billion years from now.
10:01Something of who we were.
10:04How we felt.
10:06And the music we made.
10:19The deeper waters of this vast cosmic ocean and their numberless worlds lie ahead.
10:25From out here, the sun may look like just another star.
10:42But it still exerts its gravitational hold on a trillion frozen comets, leftovers from the formation of the solar system nearly five billion years ago.
10:53It's called the Oort Cloud.
10:55No one has ever seen it before, nor could they, because each one of these little worlds is as far from its nearest neighbor as Earth is from Saturn.
11:05This enormous cloud of comets encloses the solar system, which is the second line of our cosmic address.
11:20We've only been able to detect the planets of other stars for a few decades, but we already know that planets are plentiful.
11:28They outnumber the stars. Almost all of them will be very different from Earth, and hostile to life as we know it.
11:37But what do we know about life? We've met only one kind so far. Earth life.
11:44See anything? Just empty space, right? Human eyes see only a sliver of the light that shines in the cosmos.
11:52But science gives us the power to see what our senses cannot.
11:57Infrared is the kind of light made visible by night vision goggles.
12:02Throw an infrared sensor across the darkness.
12:05Rogue planet. World without a sun.
12:12A galaxy has billions of them, adrift in perpetual night.
12:16They're orphans cast away from their mother stars during the chaotic birth of their native star systems.
12:25Rogue planets are molten at the core, but frozen at the surface.
12:30There may be oceans and liquid water in the zone between those extremes.
12:39Who knows what might be swimming there?
12:43This is what the Milky Way looks like in infrared.
12:50Every single dot, not just the bright ones, is a star.
12:55How many stars? How many worlds? How many ways of being alive?
13:02Where are we in this picture? See that trailing outer arm?
13:07That's where we live. About 30,000 light years from the center.
13:13The Milky Way galaxy is the next line of our cosmic address.
13:18We're now 100,000 light years from home.
13:21It would take light, the fastest thing there is, 100,000 years to reach us from Earth.
13:28This is the Great Spiral in Andromeda. The galaxy next door.
13:35We call our two giant galaxies, and a smattering of smaller ones, the Local Group.
13:41We can't even find our home galaxy from out here.
13:53It's just one of thousands in the Virgo supercluster.
13:57On this scale, all the objects we see, including the tiniest dots, are galaxies.
14:04Each galaxy contains billions of suns and countless worlds.
14:09Yet, the entire Virgo supercluster itself forms but a tiny part of our universe.
14:16This is the cosmos on the grandest scale we know.
14:21A network of 100 billion galaxies.
14:25It's the last line of our cosmic address.
14:28For now.
14:31Observable universe? What does that mean?
14:35Even for us, in our ship of the imagination, there's a limit to how far we can see in spacetime.
14:41It's our cosmic horizon.
14:44Beyond that horizon, lie parts of the universe that are too far away.
14:49There hasn't been enough time in the 13.8 billion year history of the universe for their light to have reached us.
14:57Many of us suspect that all of this, all the worlds, stars, galaxies and clusters in our observable universe, is but one tiny bubble in an infinite ocean of other universes.
15:16A multiverse.
15:19Universe upon universe.
15:22Worlds without end.
15:25Feeling a little small?
15:31Well, in the context of the cosmos, we are small.
15:36We may just be little guys living on a speck of dust, a float in a staggering immensity.
15:42But we don't think small.
15:45This cosmic perspective is relatively new.
15:48A mere four centuries ago, our tiny world was oblivious to the rest of the cosmos.
15:54There were no telescopes.
15:56The universe was only what you could see with the naked eye.
16:00Back in 1599, everyone knew that the sun, planets and stars were just lights in the sky that revolved around the earth.
16:09And that we were the center of a little universe.
16:13A universe made for us.
16:16There was only one man on the whole planet who envisioned an infinitely grander cosmos.
16:23And how was he spending New Year's Eve of the year 1600?
16:28Why, in prison, of course.
16:32There comes a time in our lives when we first realize we're not the center of the universe.
16:46That we belong to something much greater than ourselves.
16:49It's part of growing up.
16:51And as it happens to each of us, so it began to happen to our civilization in the 16th century.
16:58Imagine a world before telescopes, when the universe was only what you could see with the naked eye.
17:04It was obvious that Earth was motionless.
17:07And that everything in the heavens, the sun, the moon, the stars, the planets, revolved around us.
17:13And then, a Polish astronomer and priest named Copernicus made a radical proposal.
17:18The Earth was not the center.
17:20It was just one of the planets.
17:22And like them, it revolved around the sun.
17:25Many, like the Protestant reformer Martin Luther, took this idea as a scandalous affront to scripture.
17:31They were horrified.
17:33But for one man, Copernicus didn't go far enough.
17:38His name was Giordano Bruno, and he was a natural-born rebel.
17:43He longed to bust out of that cramped little universe.
17:46Even as a young Dominican monk in Naples, he was a misfit.
17:50This was a time when there was no freedom of thought in Italy.
17:53But Bruno hungered to know everything about God's creation.
17:56He dared to read the books banned by the church.
17:59And that was his undoing.
18:02In one of them, an ancient Roman, a man dead for more than 1,500 years, whispered to him of a universe far greater.
18:10One as boundless as his idea of God.
18:14Lucius asked the reader to imagine standing at the edge of the universe and shooting an arrow outward.
18:27If the arrow keeps going, then clearly the universe extends beyond what you thought was the edge.
18:31keep going, say it hits a wall, then that wall must lie beyond what you thought was the edge of
18:36the universe. Now if you stand on that wall and shoot another arrow, they're only the same two
18:42possible outcomes. It either flies forever out into space, or it hits some boundary where you
18:48can stand and shoot yet another arrow. Either way, the universe is unbounded. The cosmos must be
18:56infinite. This made perfect sense to Bruno. The god he worshipped was infinite. So how,
19:03he reasoned, could creation be anything less?
19:20It was the last steady job he ever had.
19:26And then when he was 30, he had the vision that sealed his fate. In this dream, he awakened to a
19:42world enclosed inside a confining bowl of stars. This was the cosmos of Bruno's time.
19:48He experienced a sickening moment of fear, as if the bottom of everything was falling away beneath
20:12his feet. But he summoned up his courage.
20:24I spread confident wings to space and soared toward the infinite, leaving far behind me what
20:30others strained to see from a distance. Here, there was no up, no down, no edge, no center. I saw that
20:39the sun was just another star. And the stars were other suns, each escorted by other earths like our
20:47own. The revelation of this immensity was like falling in love.
20:52Bruno became an evangelist, spreading the gospel of infinity throughout Europe. He assumed that other
21:03lovers of God would naturally embrace this grander and more glorious view of creation.
21:09What a fool I was.
21:11He was excommunicated by the Roman Catholic Church in his homeland, expelled by the Calvinists in
21:18Switzerland, and by the Lutherans in Germany. Bruno jumped at an invitation to lecture at Oxford in
21:26England. At last, he thought, a chance to share his vision with an audience of his peers.
21:34I have come to present a new vision of the cosmos. Copernicus was right to argue that our world is not
21:45the center of the universe. The earth goes around the sun. It's a planet just like the others. But
21:51Copernicus was only the dawn. I bring you the sunrise. The stars are other fiery suns made of the same
22:00substance as the earth. And they have their own watery earths, with plants and animals no less
22:06noble than our own. Are you mad or merely ignorant? Everyone knows there is only one word. What
22:11everyone knows is wrong. Our infinite God has created a boundless universe with an infinite number of
22:18worlds. Do they not read Aristotle, where you come from, or even the Bible? I beg you, reject antiquity,
22:24tradition, faith, and authority. Let us begin anew by doubting everything we assume has been
22:30proven. Your God is too small. A wiser man would have learned his lesson. But Bruno was not such a man.
22:45He couldn't keep his soaring vision of the cosmos to himself, despite the fact that the penalty for doing
22:52so in his world was the most vicious form of cruel and unusual punishment.
23:03Giordano Bruno lived at a time when there was no such thing as the separation of church and state,
23:08or the notion that freedom of speech was a sacred right of every individual. Expressing an idea that
23:14didn't conform to traditional belief could land you in deep trouble.
23:18Recklessly, Bruno returned to Italy. Maybe he was homesick, but still, he must have known that his
23:27homeland was one of the most dangerous places in Europe he could possibly go. The Roman Catholic
23:33Church maintained a system of courts known as the Inquisition, and its sole purpose was to investigate
23:40and torment anyone who dared voice views that differed from theirs.
23:48It wasn't long before Bruno fell into the clutches of the Thought Police.
23:52This wanderer, who worshipped an infinite universe, languished in confinement for eight years.
24:05Through relentless interrogations, he stubbornly refused to renounce his views.
24:10Why was the church willing to go to such lengths to torment Bruno? What were they afraid of?
24:16If Bruno was right, then the sacred books and the authority of the church would be open to question.
24:26Finally, the Cardinals of the Inquisition rendered their verdict.
24:30You are found guilty of questioning the Holy Trinity and the divinity of Jesus Christ.
24:36Of believing that God's wrath is not eternal. That everyone will be saved.
24:42Of asserting the existence of other worlds.
24:48All of the books you have written will be gathered up and burned in Saint Peter's Square.
24:54Reverend Father, these eight years of confinement have given me much time to reflect.
24:59So, you will recant?
25:01My love and reverence for the Creator inspires in me the vision of an infinite creation.
25:07You shall be turned over to the Governor of Rome to administer the appropriate punishment
25:14for those who will not repent.
25:19It may be that you are more afraid to deliver this judgment than I am to hear it.
25:29Let me pray.
25:34Let's pray.
25:39Let me pray.
25:50Let me pray.
26:21Ten years after Bruno's martyrdom, Galileo first looked through a telescope, realizing
26:39that Bruno had been right all along.
26:41The Milky Way was made of countless stars invisible to the naked eye, and some of those
26:46lights in the sky were actually other worlds.
26:50Bruno was no scientist.
26:52His vision of the cosmos was a lucky guess, because he had no evidence to support it.
26:57Like most guesses, it could well have turned out wrong.
27:01But once the idea was in the air, it gave others a target to aim at, if only to disprove
27:06it.
27:09Bruno glimpsed the vastness of space, but he had no inkling of the staggering immensity
27:15of time.
27:20How can we humans, who rarely live more than a century, hope to grasp the vast expanse
27:26of time that is the history of the cosmos?
27:29The universe is 13.8 thousand million years old.
27:33In order to imagine all of Cosmic Time, let's compress it into a single calendar year.
27:39The Cosmic Calendar begins on January 1st, with the birth of our universe.
27:58It contains everything that's happened since then, up to now, which on this calendar is
28:03midnight, December 31st.
28:05On this scale, every month represents about a billion years.
28:10Every day represents nearly 40 million years.
28:14Let's go back as far as we can, to the very first moment of the universe.
28:20January 1st, the Big Bang.
28:24It's as far back as we can see in time, for now.
28:41Our entire universe emerged from a point smaller than a single atom.
28:46Space itself exploded in a cosmic fire, launching the expansion of the universe, and giving birth
28:53to all the energy, and all the matter we know today.
28:57I know that sounds crazy, but there's strong observational evidence to support the Big Bang
29:02theory, and it includes the amount of helium in the cosmos, and the glow of radio waves left
29:07over from the explosion.
29:08As it expanded, the universe cooled, and it was darkness for about 200 million years.
29:16Gravity was pulling together clumps of gas and heating them, until the first stars burst
29:21into light on January 10th.
29:23On January 13th, these stars coalesced to the first small galaxies.
29:38These galaxies merged to form still larger ones, including our own Milky Way, which formed about
29:4611 billion years ago, on March 15th of the cosmic year.
29:51Hundreds of billions of suns, which one is ours, is not yet born.
30:00It will rise from the ashes of other stars.
30:04See those lights flashing like paparazzi?
30:08Each one is a supernova, the blazing death of a giant star.
30:14Stars die and are born in places like this one, a stellar nursery.
30:18They condense like raindrops from giant clouds of gas and dust.
30:23They get so hot that the nuclei of the atoms fuse together deep within them to make the oxygen
30:29we breathe.
30:30The carbon in our muscles, the calcium in our bones, the iron in our blood, all of it was
30:36cooked in the fiery hearts of long-vanished stars.
30:40This star stuff is recycled and enriched again and again through succeeding generations of stars.
30:57How much longer until the birth of our sun?
31:03A long time.
31:05It won't begin to shine for another six billion years.
31:11Our sun's birthday is August 31st on the cosmic calendar.
31:15Four and a half billion years ago.
31:21As with the other worlds of our solar system, Earth was formed from a disk of gas and dust
31:27orbiting the newborn sun.
31:29Repeated collisions produced a growing ball of debris.
31:32We exist because the gravity of that one next to it just nudged it an inch to the left.
31:50What difference could an inch make on the scale of the solar system?
31:54Just wait.
31:56You'll see.
31:56The Earth took one hell of a beating in its first billion years.
32:05Fragments of orbiting debris collided and coalesced until they snowballed to form our Moon.
32:13The Moon is a souvenir of that violent epoch.
32:17If you stood on the surface of that long-ago Earth, the Moon would have looked a hundred times brighter.
32:22It was ten times closer back then, locked in a much more intimate gravitational embrace.
32:29As the Earth cooled, seas began to form.
32:33The tides were a thousand times higher then.
32:36Over the eons, tidal friction within the Earth pushed the Moon away.
32:40Life began somewhere around here, September 21st, three and a half billion years ago in our little world.
32:55We still don't know how life got started.
32:58For all we know, it may have come from another part of the Milky Way.
33:01The origin of life is one of the greatest unsolved mysteries of science.
33:05That's life cooking.
33:11Evolving all the biochemical recipes for its incredibly complex activities.
33:17By November 9th, life was breathing, moving, eating, responding to its environment.
33:26We owe a lot to those pioneering microbes.
33:30Oh yeah, one other thing.
33:32They also invented sex.
33:34December 17th was quite a day.
33:41Life in the sea really took off.
33:44It was exploding with a diversity of larger plants and animals.
33:49Tiktaalik was one of the first animals to venture onto land.
33:55It must have felt like visiting another planet.
33:57Forests, dinosaurs, birds, insects, it all evolved in the final week of December.
34:08The first flower bloomed on December 28th.
34:12As these ancient forests grew and died and sank beneath the surface, their remains transformed into coal.
34:24Three hundred million years later, we humans are burning most of that coal to power and imperil our civilization.
34:33Remember that asteroid back in the formation of the solar system?
34:42The one that got nudged a little to the left?
34:44Well, here it comes.
34:47It's 6.24 a.m. on December 30th on the Cosmic Calendar.
34:51For more than a hundred million years, the dinosaurs were lords of the Earth, while our ancestors, small mammals, scurried fearfully underfoot.
35:09If the asteroid changed all that, suppose it hadn't been nudged at all, it would have missed the Earth entirely.
35:16And for all we know, the dinosaurs might still be here, but we wouldn't.
35:19This is a good example of the extreme contingency, the chance nature of existence.
35:27The universe is already more than 13 and a half billion years old.
35:31Still, no sign of us.
35:33In the vast ocean of time that this calendar represents, we humans only evolved within the last hour of the last day of the Cosmic Year.
35:5111.59 in 46 seconds.
35:54All of recorded history occupies only the last 14 seconds.
35:58And every person you've ever heard of lives somewhere in there.
36:05All those kings and battles, migrations and inventions, wars and loves, everything in the history books happen here in the last seconds of the Cosmic Calendar.
36:19But if we want to explore such a brief moment of Cosmic Time,
36:25we'll have to change scale.
36:28We are newcomers to the Cosmos.
36:50Our own story only begins on the last night of the Cosmic Year.
36:53It's 9.45 on New Year's Eve.
36:57Three and a half million years ago, our ancestors, yours and mine, left these traces.
37:05We stood up and parted ways from them.
37:09Once we were standing on two feet, our eyes were no longer fixated on the ground.
37:13Now, we were free to look up and wonder.
37:16For the longest part of human existence, say, the last 40,000 generations, we were wanderers, living in small bands of hunters and gatherers, making tools, controlling fire, naming things.
37:35To find out what happens next, we'll have to change scale to see the last minute of the last night of the Cosmic Year.
37:571159.
37:59We're so very young on the timescale of the universe that we didn't start painting our first pictures until the last 60 seconds of the Cosmic Year.
38:09A mere 30,000 years ago.
38:21This is when we invented astronomy.
38:24In fact, we're all descended from astronomers.
38:26Our survival depended on knowing how to read the stars in order to predict the coming of the winter and the migration of the wild herds.
38:35And then, around 10,000 years ago, there began a revolution in the way we lived.
38:41Our ancestors learned how to shape their environment, taming wild plants and animals, cultivating land and settling down.
38:49This changed everything.
38:52For the first time in our history, we had more stuff than we could carry.
38:57We needed a way to keep track of it.
39:00At 14 seconds to midnight, or about 6,000 years ago, we invented writing.
39:06And it wasn't long before we started recording more than bushels of grain.
39:10Writing allowed us to save our thoughts and send them much further in space and time.
39:14Tiny markings on a clay tablet became a means for us to vanquish mortality.
39:21It shook the world.
39:23Moses was born seven seconds ago.
39:27Buddha, six seconds ago.
39:30Jesus, five seconds ago.
39:33Muhammad, three seconds ago.
39:36It was not even two seconds ago that, for better or worse, the two halves of the earth discovered each other.
39:42And it was only in the very last second of the cosmic calendar that we began to use science to reveal nature's secrets and her laws.
39:52The scientific method is so powerful that in a mere four centuries, it has taken us from Galileo's first look through a telescope at another world to leaving our footprints on the moon.
40:03It allowed us to look out across space and time to discover where and when we are in the cosmos.
40:13We are a way for the cosmos to know itself.
40:18Carl Sagan guided the maiden voyage of cosmos a generation ago.
40:22He was the most successful science communicator of the 20th century.
40:25But he was first and foremost a scientist.
40:30Carl contributed enormously to our knowledge of the planets.
40:34He correctly predicted the existence of methane lakes on Saturn's giant moon Titan.
40:40He showed that the atmosphere of the early Earth must have contained powerful greenhouse gases.
40:45He was the first to understand that seasonal changes on Mars were due to windblown dust.
40:52Carl was a pioneer in the search for extraterrestrial life and intelligence.
40:57He played a leading role in every major spacecraft mission to explore the solar system during the first 40 years of the space age.
41:04But that's not all he did.
41:09This is Carl Sagan's own calendar from 1975.
41:17Who was I back then?
41:22I was just a 17-year-old kid from the Bronx with dreams of becoming a scientist.
41:26And somehow the world's most famous astronomer found time to invite me to Ithaca in upstate New York and spend a Saturday with him.
41:36I remember that snowy day like it was yesterday.
41:39He met me at the bus stop and showed me his laboratory at Cornell University.
41:44Carl reached behind his desk and inscribed this book for me.
41:47For Niam, a future astronomer.
41:55Carl.
41:57At the end of the day, he drove me back to the bus station.
42:00The snow was falling harder.
42:02He wrote his phone number, his home phone number, on a scrap of paper.
42:05And he said, if the bus can't get through, call me and spend the night at my home with my family.
42:11I already knew I wanted to become a scientist.
42:13But that afternoon, I learned from Carl the kind of person I wanted to become.
42:19He reached out to me and to countless others, inspiring so many of us to study, teach, and do science.
42:27Science is a cooperative enterprise spanning the generations.
42:32It's the passing of a torch from teacher to student to teacher.
42:35A community of minds reaching back to antiquity and forward to the stars.
42:42Now, come with me.
42:45Our journey is just beginning.
43:05About 15th century.
43:06.
43:08It's theój agility of the company.
43:09The spirit of his home, it's the only time for me.
43:10The spirit of his home, it's the only time for me to walk away.
43:11The spirit of his home, which is how he knew about this.
43:14The spirit of his home, and the life of the main goal.
43:16It's all the time for me.
43:18It's only time for me.
43:20Just kidding.
43:22It's more than you wanted to do, I want to be my back to the park.
43:24And the spirit of his home.
43:26A care for me.
43:27A desire for you.
43:29You can look.