Category
📺
TVTranscript
00:00The dream of becoming a citizen of the cosmos was born here more than two millennia ago.
00:28In the city of Alexandria, named after and conceived by its dead conqueror, Alexander the Great.
00:36The Ptolemies, the Greek kings who inherited the Egyptian portion of Alexander's empire, built this library and its associated research institution.
00:46Rarely, if ever, before or since, has there been a government that was willing to spend so much of its gross national product on the acquisition of knowledge.
00:57And it paid off, big time.
01:01Every ship entering Alexandria's harbor was searched, not for contraband, but for books that might be copied and stored here.
01:09In what was then the greatest library on earth.
01:19Here, Eratosthenes, one of the chief librarians, accurately calculated the size of the earth and invented geography.
01:27Pythagoras.
01:29Hypatia.
01:30Euclid.
01:31Euclid set forth the precepts of geometry in a textbook that remained in use for 2300 years.
01:49The Old Testament Bible comes down to us mainly from the Greek translations made here.
02:01The original manuscripts are the masterpieces of Greek comedy and drama, poetry, science, engineering, medicine and history.
02:11The total work product of the awakening of ancient civilization was kept here.
02:17Estimates vary on the total number of scrolls.
02:20They range from 500,000 to nearly a million.
02:25And all of it, all of this is but a tiny fraction of the information that you have at your fingertips at this very moment.
02:35The collective knowledge of our species, our own electronic library of Alexandria, may be accessed by anyone who has a device and the interest and the freedom to do so.
02:49This was not true in Alexandria, where knowledge belonged to the elite.
02:55So in the 4th century AD, when the mob came to destroy the library and the genius of classical civilization, there were not enough people to defend it.
03:06What will happen the next time the mob comes?
03:19To
03:32How will it
03:39How will we
04:48We've come a long way together, traveling from deep inside the heart of an atom, clear
04:57out to the cosmic horizon, and from the beginning of time to the distant future.
05:02I think we're ready to perform an experiment.
05:06It's not the kind of experiment that requires a laboratory.
05:36You can do it in your head.
05:38It's called a thought experiment.
05:42Pick a star.
05:43Any one of the hundreds of billions of stars in our Milky Way galaxy.
05:48Which is just one galaxy out of the hundred billion in the known universe.
05:52How about that star?
05:55Or that one?
05:57Okay, this one.
05:59It's orbited by dozens of planets and moons.
06:03Suppose on one of them, there lives an intelligent species, one of the ten million life forms on that planet.
06:10And there's a subgroup of that species who believe they have it all figured out.
06:16Their world is the center of the universe.
06:20A universe made for them.
06:22And that they know everything they need to know about it.
06:26Their knowledge is complete.
06:27How seriously would you take their claim?
06:37Our ancestors believed the universe was made for them.
06:40It was natural to assume that we were at the center.
06:44After all, looks like the sun and stars all revolve around us.
06:48We still speak of the sun rising.
06:50The architecture of our language, myths, and dreams comes from that pre-scientific age.
06:57This is our planet, as it was known then.
07:01Just before Columbus set sail.
07:03This first globe of the Earth was cutting edge when Martin Beheim made it in 1492.
07:10Like everyone else, he believed that the jigsaw puzzle of geography was complete.
07:16There were three continents.
07:17Europe, Africa, and Asia.
07:19And only the great world ocean in between.
07:23Beheim had no clue that North and South America even existed.
07:29It's easy to feel smug, right?
07:33Well, the fact is, Martin Beheim knew infinitely more about his world, the Earth,
07:39than we know about ours, the universe.
07:43A recent lesson in humility will serve to illustrate.
07:47In 1912, Victor Hess made a series of voyages into the sky above Austria and found the thing that scientists love best.
07:58And even today, a century later, we are still searching for a complete explanation of what Hess found.
08:14A new kind of energy had recently been discovered, radioactivity.
08:21It was given off by certain elements like radium, but it was also found in the air, even far away from radioactive rocks.
08:31It was everywhere.
08:32Where did this strange energy come from?
08:34Where did this strange energy come from?
08:37No one knew.
08:38Hess suspected that it might come from above the Earth.
08:42To test his hypothesis, he carried radiation detectors high into the sky.
08:47During a risky ascent in a hydrogen balloon, he attained an altitude of more than three miles.
08:55When he reached the thin, cold upper half of the atmosphere,
08:59he found that the radiation was more than twice as strong as on the ground.
09:14The radiation must be coming from above.
09:18That's why its intensity was weaker on the ground.
09:21The Earth's atmosphere was absorbing most of it.
09:25Some thought that the radiation might come from the sun.
09:29To test that idea, Hess timed one of his ascents to coincide with a solar eclipse.
09:34But the eclipse had no effect on the radiation.
09:46Hess also found that the radiation was just as strong at night as in daylight.
09:51It was coming from above, but not from the sun.
09:55What Hess did not know was that the solar wind doesn't move that quickly.
10:00And so, for the wrong reason, he came to the right conclusion.
10:06Hess had discovered cosmic rays.
10:09Showers of subatomic particles that crisscrossed the universe at nearly the speed of light.
10:15Without the shielding effect of the Earth's atmosphere, they would be lethal.
10:19Some cosmic rays can carry as much energy as a bullet fired from a rifle.
10:24It would take decades to trace those cosmic rays back to a death of unimaginable violence.
10:31The cosmic rays that Viktor Hess detected in the skies above Austria posed a mystery to scientists.
10:53Radioactivity in minerals on Earth, like uranium ore, comes from the disintegration of atoms.
10:59But cosmic rays were of a different nature.
11:03They were far more powerful than anything known in Hess's world.
11:08Scientists wondered for two decades what could possibly produce cosmic rays.
11:13Enter Fritz Zwicky.
11:16Most brilliant man you've never heard of.
11:18In 1933, he and a colleague discovered that some stars flare up to become as bright as their entire galaxy for a few weeks before fading out again.
11:30Fritz Zwicky was the first person to understand what just happened.
11:34He correctly surmised that this is the way a massive star dies.
11:39It blows its guts out into space.
11:41He called this kind of stellar death a supernova.
11:50And predicted that the dying star would shrink from about a million miles across to only ten.
11:55This corpse would be so dense that a single grain of it would weigh as much as the Great Pyramid in Egypt.
12:04It would consist almost entirely of subatomic particles called neutrons.
12:09So, he named these bizarre objects neutron stars.
12:12And 35 years after Zwicky predicted their existence, astronomers began to find them.
12:17We call them pulsars when they spin rapidly and emit regular pulses of radio energy.
12:23Supernovas and neutron stars could account for a wide range of cosmic rays, but not the most energetic ones.
12:30Nothing yet known to science can explain them.
12:33And we're fine with that.
12:35It's one of the things I love about science.
12:37We don't have to pretend we have all the answers.
12:39Zwicky also came up with the idea that the gravity of a galaxy warps the fabric of space around it to act like a lens.
12:48This distorts and magnifies light from any other galaxy lying directly behind it.
12:53So, astronomers on Earth would see multiple images of that same distant galaxy, deformed as in a funhouse mirror.
13:02Forty years after this prediction, we started finding them too.
13:06And Zwicky made yet another discovery back in the 1930s.
13:13While studying the coma cluster of galaxies, he noticed something funny about the way they moved.
13:20The galaxies were going way too fast.
13:23So fast that they should have been flying apart from each other.
13:27Because all the stars and all those galaxies had far too little gravity to hold the cluster together.
13:32Zwicky thought that something else must be binding them to each other.
13:37That mysterious missing component would have to weigh something like 50 times as much as the stars themselves.
13:45But no one paid much attention to this wild notion.
13:48Just another one of Zwicky's crazy ideas.
13:51In our solar system, the innermost planet, Mercury, moves much faster than the outermost one, Neptune.
13:58And that makes sense, right?
13:59The harder you push or pull on something, the faster it goes.
14:03The sun's gravity weakens with increasing distance.
14:06So, the planets that are farther from the sun move more slowly.
14:09Everyone expected that the outermost stars in a galaxy would act the same way.
14:17Most of the stars are concentrated towards the center.
14:20So, their collective gravity pulls on the other stars the same way the sun pulls on the planets.
14:27But in the 1970s, when astronomer Vera Rubin studied the Andromeda Galaxy,
14:32she discovered that the outer stars obeyed no such rule.
14:35Unlike the outer planets in the solar system, the outer stars in the galaxy were all going at the same speed as the stars that were closer in.
14:44And they were moving way faster than expected.
14:48That's funny, Vera thought.
14:50There must be something weird about the Andromeda Galaxy.
14:54So, she looked at another galaxy.
14:56Same story.
14:58And another.
14:59Vera studied 60 galaxies and found that all of them seemed to be violating the law of gravity.
15:05A core principle of physics.
15:08After some initial healthy skepticism, her colleagues looked for themselves and found that Vera was right.
15:16It's not that Isaac Newton had gotten the law of gravity wrong.
15:20Vera Rubin had discovered that the gravity of something massive and invisible was forcing the stars to go fast.
15:26And then, someone remembered crazy old Fritz Wicke.
15:34And the unknown source of gravity in the galaxy clusters that he called dark matter back in 1933.
15:42Vera Rubin had verified the existence of a new, much larger cosmos.
15:53And just like the one we thought we knew, it was filled with mystery.
15:59Dark matter is completely unobservable, except for its gravitational effect, which makes visible stars and galaxies move faster.
16:06It's nature is another deep mystery.
16:11Rubin had provided the evidence for an invisible universe nearly ten times more massive than the one we thought we knew.
16:18It was as if we had been standing on the seashore at night, mistakenly believing that the froth on the waves was all there was to the ocean.
16:28Vera Rubin looked at the stars and realized they were merely the foam on the waves.
16:35And that the greatest part of the ocean remained unknown.
16:39But wait, it gets crazier.
16:41Our Milky Way galaxy, a few hundred billion stars, plus the clouds of gas and dust, the stuff of once and future stars, and about a hundred billion other galaxies.
16:59All of that, including those uncounted billions of trillions of planets, moons, and comets, amounts to only 5% of what is actually there.
17:12Because there's a bigger unsolved mystery than dark matter.
17:16Dark energy, which makes up even more of the cosmos and drives its expansion.
17:21And it was Fritz Zwicky's supernovas that lit the way to the revelation of its existence.
17:30In one scenario, a star consumes all of its nuclear fuel.
17:38Then cools and suddenly collapses under its own gravity.
17:43The star rebounds in a massive explosion.
17:47Leaving behind a neutron star or a black hole.
17:51Since the mass of the original star can fall within a wide range, its peak brightness as a supernova can also vary widely.
18:00So you can't tell how far away it is just from how bright it looks.
18:05A relatively nearby supernova might appear just as bright as one that was more powerful but farther away.
18:12But there's another kind of supernova that comes in only one strength.
18:16It marks the violent grand finale of a tango danced by a giant star and a dwarf.
18:23As the two stars orbit closely around each other, the giant sheds its outer layers of gas onto the dwarf.
18:33When the added weight becomes too much for it to bear, the dwarf detonates like a stupendous thermonuclear bomb.
18:41For a few weeks, the brilliance of such a supernova rivals the combined light of all the stars in its galaxy.
18:49This kind of supernova always has the same maximum power output, about 5 billion times brighter than our Sun.
18:57With big telescopes, we can see them in galaxies very far away, out toward the edge of the observable Universe.
19:14Because all such supernovas have the same wattage, they are ideal tools for measuring distances to the farthest reaches of the Universe.
19:22We call them Standard Candles.
19:30In 1929, Edward Hubble discovered that the Universe is expanding.
19:36The distant galaxies are drifting away from one another.
19:39Later, we learn that the expansion began some 14 billion years ago with the explosive birth of the Universe, the Big Bang.
19:47Everybody assumed that the rate of expansion would be slowing down due to the mutual pull of gravity between all the parts of the Universe.
19:58If there is enough dark matter, its gravity would eventually bring the expansion to a stop, and the Universe would then fall back on itself.
20:05In that case, everything would eventually collapse in a big crunch.
20:12On the other hand, if the Universe had less dark matter, the expansion would continue forever, just getting slower and slower.
20:19Two competing teams of astronomers were observing those supernovas in distant galaxies.
20:24It turned out to be another one of those, that's funny, moments.
20:29In 1998, both teams independently came to the same conclusion.
20:34The expansion isn't slowing down at all. It's speeding up.
20:38This means the Universe will continue to expand forever.
20:42There seems to be a mysterious force in the Universe, one that overwhelms gravity on the grandest scale, to push the cosmos apart.
20:50Most of the energy of the Universe is bound up in this unknown force.
20:56We call it dark energy.
20:58But that name, like dark matter, is merely a code word for our ignorance.
21:04It's okay not to know all the answers.
21:07It's better to admit our ignorance than to believe answers that might be wrong.
21:11Pretending to know everything closes the door to finding out what's really there.
21:16Tonight, our ships sail into even more exotic waters.
21:23Come with me.
21:24Come with me.
21:36Only two of our ships have ventured into the great dark ocean of interstellar space.
21:42The longest odyssey in all of history was launched back in 1977.
21:48NASA's Voyager 1 and 2.
21:54The Voyagers move about 40,000 miles an hour.
21:58They gave us our first close-up look at Jupiter's Great Red Spot.
22:03A hurricane three times the size of Earth, and one that's been raging since at least 1644 when it was first observed.
22:11For all we know, it could be thousands of years old.
22:15The Voyagers discovered the first active volcano on another world.
22:20A Jupiter's moon Io.
22:24And an ocean beneath the icy surface of the moon Europa.
22:27With at least twice as much water as we have here on Earth.
22:35The Voyagers dared to fly across Saturn's rings and revealed that they were made of hundreds of thin bands of orbiting snowballs.
22:46On Saturn's giant moon Titan, Voyager detected an atmosphere four times denser than Earth's.
22:58That hinted at the existence of hydrocarbon seas on Titan, which we later confirmed.
23:03Voyager 2 gave us our first portrait of the outermost planet Neptune.
23:11Where the winds roar at a thousand miles per hour.
23:17And its moon Triton, where geysers of boiling nitrogen, shoot five miles high.
23:24Voyager successfully completed its mission of discovery to the outer planets.
23:34But its odyssey into the darkness was just beginning.
23:4035 years after its launch, Voyager 1 became the first of our spacecraft to enter an uncharted realm.
23:46The Sun is constantly shooting out streams of charged particles in all directions, moving at a million miles an hour.
23:55This solar wind blows a vast magnetic bubble.
24:00Our heliosphere that extends beyond the outer planets.
24:04It pushes out against the thin gas of interstellar space.
24:08There's a border where one ends and the other begins.
24:12Voyager 1 reported back to Earth that its detectors were being pummeled by more and more cosmic rays.
24:20Until then, we didn't know where the interstellar ocean began.
24:24Voyager 1 pressed on past a boundary we had never crossed before.
24:30The heliosphere shields us from most of the deadly cosmic rays.
24:34When stormy solar winds blow, this zone of protection grows.
24:38In calm solar weather, it shrinks.
24:39When a star goes supernova in our galactic neighborhood.
24:43The debris from the exploded star pushes the heliosphere back towards the Sun.
24:50If it's strong enough to push it all the way back to Earth's orbit, our planet gets a radioactive bath of supernova debris.
24:58Luckily, this doesn't happen very often.
25:01The last one was perhaps 2 million years ago.
25:05A neighboring star explodes a million years before there's even such a thing as the human species.
25:12How can we possibly know this?
25:15Because the dying star left its traces miles below the surface of the ocean.
25:19Manganese nodules, small rocks like this one, are scattered over much of the deep sea floor.
25:30They grow very slowly.
25:32I'm talking a millimeter in a million years.
25:37Layer upon layer.
25:40These nodules grow in partnership with bacteria by taking up minerals dissolved in the seawater.
25:47A supernova produces a radioactive form of iron, unlike anything made by natural processes on Earth.
25:57Researchers found telltale traces of this iron in a thin layer below the surface of the manganese nodules.
26:03They used the known rate of growth of the nodules to date that layer and to connect it to the fate of a star that perished eons ago.
26:15The difference between seeing nothing but a pebble and reading the history of the cosmos inscribed inside it is science.
26:27The interstellar ocean is dark and deep.
26:30Out here the sun is just the brightest star in the sky.
26:35Yet the Voyagers maintain their regular communications with NASA's Jet Propulsion Laboratory.
26:40Talking back and forth across the light hours that separate these ships from their home port.
26:46No other objects touched by human hands have ever ventured this far from home.
26:51Even after they lose their ability to respond to our command, the last and by far the longest phase of the Voyager mission will begin.
27:06Back in 1979 when both Voyagers rounded Jupiter, its massive gravity acted as a slingshot, flinging them out of the solar system to travel among the stars of our galaxy.
27:25For a billion years, Carl Sagan recognized that the Voyager mission offered two free tickets to something approaching eternity.
27:34He assembled a small team to create a message to any civilization that might one day encounter the derelict spacecraft.
27:43Twenty-six centuries ago, the Assyrian King S.R. Haddon wrote,
27:52I had monuments made of bronze and inscriptions of baked clay.
27:59I'd left them in the foundations for future times.
28:03These hieroglyphics continue that ancient tradition.
28:07They are inscribed on the cover of a message designed to be read by the beings of other worlds and times.
28:13What could we possibly have in common with an alien civilization with its own separate evolutionary history and one so far advanced beyond us that they can patrol interstellar space?
28:27One thing at least, a universal language. Science.
28:33It's hard to break the bonds of gravity.
28:36You can only sail the cosmic seas if you speak mathematics and physics.
28:40Hydrogen is the most common element in the universe.
28:45The electron in a hydrogen atom flips the direction of its spin at a constant rate or frequency.
28:51Hydrogen atoms are like tiny natural clocks.
28:55Tick. Tock.
28:57Now we have a unit of time in common with the extraterrestrials.
29:01This will come in handy when we get to the next level of the message.
29:05Here's our return address in space.
29:06Pulsars are rapidly spinning neutron stars that give off regular bursts of radio waves.
29:13You can set your clock by them.
29:16The sun is at the center of this diagram, and the lines point to the 14 nearest pulsars.
29:22A simple code labels each pulsar with its unique frequency, using the tick-tock of a hydrogen atom as the unit of time.
29:28So alien astronomers could use this diagram to locate the home star of the Voyager spacecraft in our galaxy.
29:37They could also tell how long ago the spacecraft was launched.
29:41And that's important, because the Voyager record has a projected shelf life of a thousand million years.
29:46Become an extraterrestrial archaeologist for a few moments.
29:53An artifact has been fished out of the interstellar ocean.
29:57It was made by beings that lived about a billion years ago.
30:01What would you make of them and their world?
30:03They've sent us their music and greetings in 59 human languages.
30:13Hello from the children of planet Earth.
30:18Planet Earth.
30:19And one whale language.
30:21And a sound essay that includes a Saturn V rocket launch.
30:27A mother's first words to her newborn baby.
30:31Oh, come on now.
30:34The brainwaves of a young woman newly fallen in love.
30:41And the sound of a pulsar.
30:43All of that will live for a billion years.
31:06How long is a billion years?
31:13If you compress all the time since the Big Bang, the explosive birth of the universe, into a single Earth year, a billion years is about one month of that year.
31:29What was happening on Earth a billion years ago?
31:36Most of Earth's land was amassed into a supercontinent called Rodinia.
31:40It was a barren desert, no animals, no plants.
31:44A billion years ago, there wasn't enough oxygen in our atmosphere to form an ozone layer.
31:49And without it, ultraviolet radiation prevented life from colonizing the land.
31:54Rodinia probably looked more like Mars than present-day Earth.
31:57The giant world ocean produced huge rainstorms causing flooding and erosion.
32:04Glaciers formed.
32:06And their slow but relentless movements carved the land into new shapes.
32:10Single-celled organisms dominated the oceans.
32:14But some existed in colonies called microbial mats.
32:17And the first multicellular organisms would soon evolve.
32:22And a billion years from now?
32:25What will Earth be like?
32:27Long after our cities, the Egyptian pyramids, the Rocky Mountains have all been eroded to dust?
32:31There are few things we can say with confidence about such a far distant time.
32:42The only thing we can say for sure is that Earth as we know it will be so changed that we would scarcely recognize it as home.
32:50But even a thousand million years from now, something of who we were and the music that we made in that long-ago spring will live on.
33:08In that distant future, our Sun will have completed another four orbits around the center of the galaxy.
33:14And the Voyagers will have ventured far from the Sun.
33:30Carl Sagan was a member of Voyager's imaging team.
33:33And it was his idea that Voyager take one last picture.
33:37A generation before, an astronaut on the last Apollo flight to the Moon
33:41had taken a picture of the whole Earth, the planet as a world without borders.
33:48It became an icon of a new consciousness.
33:51Carl realized the next step in this process.
33:55He convinced NASA to turn the Voyager 1 camera back towards Earth when the spacecraft went beyond Neptune
34:03for one last look homeward at what he called the Pale Blue Dot.
34:11That's here. That's home. That's us.
34:12On it, everyone you love, everyone you know, everyone you ever heard of, every human being who ever was, lived out their lives.
34:30The aggregate of our joy and suffering.
34:35Thousands of confident religions, ideologies and economic doctrines.
34:40Every hunter and forager.
34:43Every hero and coward.
34:45Every creator and destroyer of civilization.
34:48Every king and peasant.
34:50Every young couple in love.
34:52Every mother and father.
34:53Hopeful child.
34:54Hopeful child.
34:56Inventor and explorer.
34:58Every teacher of morals.
35:00Every corrupt politician.
35:02Every superstar.
35:04Every supreme leader.
35:06Every saint and sinner in the history of our species.
35:09Lived there.
35:11On a mote of dust.
35:13Suspended in a sunbeam.
35:15The earth is a very small stage.
35:20In a vast cosmic arena.
35:24Think of the rivers of blood.
35:28Spilled by all those generals and emperors.
35:31So that in glory and triumph they could become the momentary masters.
35:36Of a fraction of a dot.
35:39Think of the endless cruelties visited by the inhabitants of one corner of this pixel.
35:47On the scarcely distinguishable inhabitants of some other corner.
35:52How frequent their misunderstandings.
35:55How eager they are to kill one another.
35:58How fervent their hatreds.
36:02Our posturings.
36:04Our imagined self-importance.
36:06The delusion that we have some privileged position in the universe.
36:11Are challenged.
36:13By this point of pale light.
36:16Our planet.
36:18Is a lonely speck.
36:20In the great enveloping cosmic dark.
36:24In our obscurity.
36:27In all this vastness.
36:29There is no hint.
36:31That help will come from elsewhere.
36:33To save us.
36:34From ourselves.
36:36The earth is the only world known so far.
36:39To harbor life.
36:41There is nowhere else.
36:43At least in the near future.
36:45To which our species could migrate.
36:47Visit.
36:49Yes.
36:50Settle.
36:52Not yet.
36:53Like it or not.
36:54For the moment.
36:56The earth is where we make our stand.
36:59It has been said that astronomy is a humbling.
37:03And character building experience.
37:06There is perhaps no better demonstration.
37:09Of the folly of human conceits.
37:12Than this distant image.
37:15To me.
37:17It underscores our responsibility.
37:19To deal more kindly with one another.
37:22And to preserve.
37:23And cherish.
37:25The pale blue dot.
37:27The only home.
37:28We've ever known.
37:29How did we.
37:30Tiny creatures.
37:31Living on that speck of dust.
37:32Ever manage.
37:33To figure out.
37:34How to send spacecraft.
37:35Out among the stars.
37:36Of the Milky Way.
37:37Only a few centuries ago.
37:38A mere second.
37:39Of cosmic time.
37:40We knew nothing.
37:41Of where.
37:42Or when.
37:43We were.
37:44Oblivious to the rest.
37:45Of the cosmos.
37:46We inhabited.
37:47A kind of prison.
37:48A tiny universe.
37:49Bounded.
37:50By a nutshell.
37:51How did we escape.
37:52From the prison.
37:53It was the work.
37:54Of generations of searchers.
37:55Who took five.
37:56And.
37:57Five.
37:58And.
37:59Five.
38:00Five.
38:01Five.
38:02Five.
38:03Five.
38:04Five.
38:05Five.
38:06Five.
38:07Five.
38:08Five.
38:09Five.
38:10Five.
38:11Five.
38:12Five.
38:13Five.
38:14Five.
38:15Five.
38:16Five.
38:17Five.
38:18Five.
38:19Five.
38:20Five.
38:21Five.
38:22Five.
38:23Five.
38:24Five.
38:25Five.
38:26Five.
38:27Five.
38:28Five.
38:29Five.
38:30Five.
38:31Five.
38:32Five.
38:33Five.
38:34Five.
38:35Five.
38:36Five.
38:37Five.
38:38Five.
38:39Five.
38:40Five.
38:41Five.
38:42Five.
38:43Five.
38:44Five.
38:45Five.
38:46make it so. Test ideas by the evidence gained from observation and experiment.
38:54If a favorite idea fails a well-designed test, it's wrong. Get over it.
39:02Follow the evidence wherever it leans. If you have no evidence, reserve judgment.
39:11And perhaps the most important rule of all? Remember, you could be wrong.
39:17Even the best scientists have been wrong about some things.
39:21Newton, Einstein, and every other great scientist in history.
39:26They all made mistakes. Of course they did. They were human.
39:31Science is a way to keep from fooling ourselves and each other.
39:38Have scientists known sin?
39:44Of course. We have misused science just as we have every other tool at our disposal.
39:51And that's why we can't afford to leave it in the hands of a powerful few.
39:57The more science belongs to all of us, the less likely it is to be misused.
40:06These values undermine the appeals of fanaticism and ignorance.
40:11And after all, the universe is mostly dark, dotted by islands of light.
40:19Learning the age of the Earth or the distance to the stars or how life evolves, what difference does that make?
40:26Well, part of it depends on how big a universe you're willing to live in.
40:30Some of us like it small. That's fine. Understandable.
40:36But I like it big.
40:38And when I take all of this into my heart and my mind, I'm uplifted by it.
40:42And when I have that feeling, I want to know that it's real.
40:46That it's not just something happening inside my own head.
40:50Because it matters what's true.
40:52And our imagination is nothing compared with nature's awesome reality.
41:02I want to know what's in those dark places.
41:07And what happened before the Big Bang.
41:12I want to know what lies beyond the cosmic horizon and how life began.
41:17Are there other places in the cosmos where matter and energy have become alive and aware?
41:34I want to know my ancestors. All of them.
41:38I want to be a good, strong link in the chain of generations.
41:42I want to protect my children and the children of ages to come.
41:47We, who embody the local eyes and ears and thoughts and feelings of the cosmos.
41:53We've begun to learn the story of our origins.
41:56Star stuff. Contemplating the evolution of matter.
42:00Tracing that long path by which it arrived at consciousness.
42:04We and the other living things on this planet carry a legacy of cosmic evolution spanning billions of years.
42:11If we take that knowledge to heart, if we come to know and love nature as it really is,
42:17then we will surely be remembered by our descendants as good, strong links in the chain of life.
42:23And our children will continue this sacred searching, seeing for us as we have seen for those who came before.
42:30Discovering wonders yet undreamt of in the cosmos.
42:35possibilities still the cosmos.
43:00Oh, my God.
43:30Oh, my God.