#CarlSagan covers a wide range of scientific subjects, including the origin of life and a #perspective of our place in the universe...
A 13-part #documentary #series that covers a wide range of #scientific #subjects, including the #origin of #life and a #perspective of our place in the universe narrated by famous American #Scientist – #Carl #Sagan.
A 13-part #documentary #series that covers a wide range of #scientific #subjects, including the #origin of #life and a #perspective of our place in the universe narrated by famous American #Scientist – #Carl #Sagan.
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LearningTranscript
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00:10:09Joseph Fourier. On a routine inspection of the schools in his province, Fourier
00:10:15discovered an exceptional 11-year-old boy, Jean-Francois Champollion.
00:10:24The boy's precocious intellect and remarkable flair for languages had
00:10:29already earned him the admiring attention of local scholars. Fourier, too, was
00:10:33impressed.
00:10:39What Champollion first saw in Fourier's house determined the course of his life
00:10:44and unlocked the secrets of an alien civilization.
00:10:50Fourier had recently participated, as one of many scientists, in Napoleon's
00:10:56expedition to the Middle East. He had been in charge of cataloguing the
00:11:00astronomical monuments of Egypt. The boy was entranced by Fourier's collection of
00:11:08ancient Egyptian artifacts, the mysterious fragments of a lost world.
00:11:14France, at this time, was flooded with such artifacts, plundered by Napoleon, and now a
00:11:28rousing intense interest among scholars and the general public.
00:11:31The boy's attention was caught by a specimen of Egyptian hieroglyphics.
00:11:48The boy's attention was caught by a specimen of Egyptian hieroglyphics.
00:11:52What do they mean, he asked. Nobody knows, was Fourier's reply. Then and there,
00:12:09Champollion resolved that he would understand this language that no one could read, that he
00:12:14would decode the messages from another world and another time. He became a superb linguist and
00:12:20immersed himself in the hieroglyphics.
00:12:28Fourier edited the illustrated description of Napoleon's expedition. The young
00:12:34Champollion studied it hungrily.
00:12:38To the people of Europe, these exotic images revealed an utterly alien civilization. A world of
00:12:46towering monuments and magical names. Dendera, Karnak, Luxor.
00:12:58Every illustration was a riddle posed by the past to the present.
00:13:08And among them were pictures of something called the Rosetta Stone. And portraits of the people
00:13:18who lived among the ruins of the pharaohs.
00:13:22Egypt became the land of Champollion's dreams.
00:13:28But it was not until 1828, 27 years after his fateful visit with Fourier, that Champollion first set foot in Egypt.
00:13:42With his companions, Champollion chartered boats in Cairo and sailed slowly upstream, following the course of the Nile.
00:13:56It was a journey of many weeks, which Champollion recorded in extraordinary detail.
00:14:16This was an expedition through time. A voyage across the centuries to another world.
00:14:34Champollion, as an adult, had already worked out a brilliant decipherment of the hieroglyphics.
00:14:48A word, incidentally, that means sacred carvings.
00:14:52Now Champollion was making a pilgrimage to the scene of the ancient mysteries he had been the first to understand.
00:15:02To understand.
00:15:04To understand.
00:15:10Champollion wrote,
00:15:33The evening of the 16th, we finally arrived at Dendera.
00:15:40We were only an hour away from the temples.
00:15:52Could we resist the temptation, I ask the coldest of you mortals, to dine and leave immediately
00:16:03with the orders of the moment.
00:16:12Alone and without guides, we crossed the fields.
00:16:20Presuming that the temples were in a straight line from our boat, we walked thus for an hour
00:16:25and a half without finding anything.
00:16:28We finally discovered a man who put us on the correct route and ended up walking with
00:16:32us with good graces.
00:16:36The temple appeared to us at last.
00:16:55I shall not try to describe the impression which the porches and above all the portico
00:17:00made on us.
00:17:04We stayed there two hours in ecstasy, running through the huge rooms and trying to read the
00:17:10exterior inscriptions in the moonlight.
00:17:20It was with no small rapture that Champollion entered the secret places of the temple and
00:17:26scanned the words that had waited patiently through half a million nights for a reader.
00:17:36To his brother, Champollion wrote of his joy in confirming that he could understand the
00:17:41writing on these walls.
00:17:43I am now proud, he said, that having followed the course of the Nile to the second cataract,
00:17:50I have the right to announce that there is nothing to modify in our letter on the alphabet of
00:17:56hieroglyphics.
00:18:06Our alphabet is good.
00:18:08It is applicable with the same success, first of all in Egyptian monuments of the epoch of
00:18:13the Romans, and also, which is more interesting, to the inscriptions on all temples, palaces,
00:18:19and tombs of the pharaonic epoch.
00:18:26Champollion was overwhelmed by the grandeur which surrounded him.
00:18:33It is the union, he said, of grace and majesty in the highest degree.
00:18:39We in Europe are only dwarfs.
00:18:42No nation, ancient or modern, has conceived the art of architecture on such a sublime,
00:18:48great, and imposing style as the ancient Egyptians.
00:18:52They ordered everything to be done for people who are a hundred feet high.
00:19:04This is the great temple of Karnak in Upper Egypt, continuously constructed over a period
00:19:12of more than 2,000 years until the time of the Ptolemies.
00:19:17It was here, Champollion wrote, that all the pharaonic magnificence appeared to me.
00:19:24What he had seen elsewhere, he said, seemed to me miserable compared with the colossal conceptions around me.
00:19:33A
00:19:44The
00:19:48The
00:19:52The
00:19:56On these walls and columns at Karnak, at Dendera, and everywhere else in Egypt, Champollion found
00:20:03that he could read the inscriptions, that his decipherment of a few years earlier had been
00:20:08correct. But how had he figured it out? Many had tried and failed to read the hieroglyphics.
00:20:19One group of scholars thought they were a kind of picture code full of murky metaphors,
00:20:23mostly about eyeballs and wavy lines and animals. Birds, especially birds, lots of birds.
00:20:33There were those who deduced from the hieroglyphics that the Egyptians had been
00:20:40colonists from China. There were those who deduced it the other way around.
00:20:49There was one character who, from a single look at the Rosetta Stone, deduced its meaning. He said
00:20:55that the quickness of his decipherment enabled him to avoid the systematic errors which invariably
00:21:02arise from prolonged reflection. You get better results, he was saying, if you don't think
00:21:07about it too much. As in the search for extraterrestrial intelligence today, the unbridled speculation
00:21:15by amateurs served to frighten many professionals right out of the field.
00:21:31Champollion was not frightened. He was also not distracted by the idea of hieroglyphs as pictorial metaphors. Instead, using the insights of a brilliant English physicist named Thomas Young,
00:21:33he proceeded something like this. This is an exact replica of the Rosetta Stone. The original had been found in the year 1799 by a French soldier working on the fortifications of the Nile Delta town of Rashid, which the Europeans in the
00:21:40Persistence not to learn Arabic called Rosetta. It had been part of an ancient temple, which the Europeans, in their persistence not to learn Arabic, called Rosetta. It had been part of an ancient temple of the Nile Delta town of Rashid, which the Europeans, in their persistence not to learn Arabic, called Rosetta.
00:21:58It had been part of an ancient temple, which had been torn down. If we look at it, we see that it clearly represents the same text in three different languages. Up at the top, ancient Egyptian hieroglyphics. In the middle, a kind of cursive and later hieroglyphic called Dimitra.
00:22:28And down at the bottom, the key to the enterprise, Greek. Champollion could, of course, read ancient Greek. He was a superb linguist. And discovered that this stone had been inscribed to commemorate the coronation of King Ptolemy V Epiphanes in the spring of the year 196 BC.
00:22:51As we would expect, the Greek text includes many references to King Ptolemy. Here, for example, you can see it.
00:22:58Now, in roughly the same positions, but in the hieroglyphic text, are these ovals, or cartouches, as they're called. And if this cartouche really means Ptolemy, then the individual hieroglyphs are unlikely to be a
00:23:21pictograms or metaphors, much more likely they're letters, or at least syllables. In addition, Champollion had the presence of mind to count up the number of Greek words and the number of individual hieroglyphics in what are presumably equivalent texts.
00:23:39He found that the number of individual hieroglyphs is much larger than the number of Greek words, again implying that the hieroglyphs are mainly letters and syllables. But which hieroglyphs correspond to which letters?
00:23:55Fortunately, Champollion had available to him a kind of second Rosetta Stone, an obelisk which had been excavated at the Temple of Philae and which had inscribed upon it cartouches representing the hieroglyphic equivalent of another Greek name, Cleopatra.
00:24:15So here we have the Cleopatra cartouche, and here is the Ptolemaeus cartouche. Here we've turned it around, changing left to right to right to left, and spread the hieroglyphs out so we can see them all.
00:24:34Now, immediately we notice that there are some similarities. This first hieroglyph in Ptolemy is a kind of square. The fifth hieroglyph in Cleopatra is a square, but Cleopatra, both of them, seem to represent a P.
00:24:52So, Ptolemy and Cleopatra both give us the same interpretation. A square is a P. Likewise, the fourth hieroglyph in Ptolemy is a lion, Ptole, P-T-O-L.
00:25:10Likewise, the second hieroglyph in Cleopatra is an L. So, again, it's consistent. The pattern is emerging. Likewise, this roper hangman's noose, Pto-O-L-O-M. It's an O.
00:25:27Cleopatra, it's an O. And in this way, Champollion was able to assign letters for each of the hieroglyphs we see here.
00:25:40The first hieroglyphs, Ptolemy, and likewise, Cleopatra. The eagle is an A. Notice there are two different symbols for T, but in English, same sort of thing, F and PH.
00:26:00Champollion discovered that the hieroglyphics were basically a simple substitution cipher. Now, there's other stuff in here.
00:26:07All the rest of this in the cartouche, what's that about? Well, he was later able to find out.
00:26:13This is a symbol called the Ankh, which means life. Here, there's a P-T, and that's a H, makes Ptach, the name of a god.
00:26:20And the whole cartouche read, Ptolemy, ever-living, beloved of the god Ptach. Likewise, the end of the Cleopatra is a short form meaning daughter of Isis.
00:26:34So, it turns out that Champollion's opponents were not wholly wrong. Some of the hieroglyphs, for example, the symbol Ankh, which means life, are ideograms or pictograms.
00:26:47But the key to the enterprise, Champollion's success rested on his realization that the hieroglyphs were essentially letters and syllables.
00:26:58In retrospect, it sounds almost easy, but it took people hundreds of years before they figured it out.
00:27:05Champollion walked these halls and casually read the inscriptions, which had mystified everybody else, answering the question he had posed as a child to Fourier.
00:27:18What do they mean? What a joy it must have been for him to open this one-way communications channel with another civilization, to permit a culture which had been mute for millennia to speak of its history, magic, medicine, religion, politics, philosophy.
00:27:48Today, we also are seeking messages from an ancient and exotic civilization.
00:28:01A civilization hidden from us, not in time, but in space.
00:28:09Today, we are searching for a message from the stars.
00:28:14We have not found it so far.
00:28:16We have as yet no Champollion.
00:28:19But we are just beginning.
00:28:20Perhaps those who will discover and decipher the first interstellar communications are alive at this moment, somewhere on the planet Earth.
00:28:35Extraterrestrial beings will have a different biology, a different culture, a different language.
00:28:41How could we possibly understand their messages?
00:28:43Is there, in any sense, a cosmic Rosetta Stone?
00:28:50I believe there is.
00:28:52All the technical civilizations in the cosmos, no matter how different they are, must have one language in common.
00:28:58The language called science.
00:29:01The laws of nature are everywhere the same.
00:29:07Every chemical element has a specific signature in the spectrum.
00:29:15So there are identical patterns in the light of a candle flame on Earth, and in the light of a distant galaxy.
00:29:25The spectra show not only that the same chemical elements exist throughout the universe, but also that the same laws of quantum mechanics govern atoms everywhere.
00:29:37Beings growing up on any world must come to grips with the identical laws of nature.
00:29:46Galaxies billions of light years distant evolve a spiral form.
00:29:50So does our own Milky Way, the same gravitational forces are at work.
00:29:56And on planets also, there are spiral storm systems on Jupiter.
00:30:05The same patterns are common on Earth.
00:30:08The intelligent beings on every world will, sooner or later, understand the laws of nature.
00:30:17Someday, perhaps soon, a message from the depths of space may arrive on our small world.
00:30:24If we wish to understand it, we first have to understand science.
00:30:29We do not expect an advanced technical civilization on any other planet of our solar system.
00:30:46If they were only a little behind us, 10,000 years, say, they would have no advanced technology at all.
00:30:53And if they were only a little ahead of us, we who are already exploring the solar system, then they should be here by now.
00:31:05To communicate with other civilizations, our technology must reach across not merely interplanetary distances, but interstellar distances.
00:31:21Ideally, the method should be inexpensive.
00:31:23So that a huge amount of information could be sent and received at very little cost.
00:31:30It should be fast, so an interstellar dialogue is eventually possible.
00:31:36It ought to be obvious, so that any technical civilization, no matter what its evolutionary path, will discover it early.
00:31:46Surprisingly, there is such a method.
00:31:49It's called radio astronomy.
00:31:53This is the largest radio radar telescope on the planet Earth, the Arecibo Observatory.
00:32:02It's located in a remote valley on the island of Puerto Rico.
00:32:13It sends and receives radio signals.
00:32:17But it's so large and powerful that it could communicate with an identical radio telescope 15,000 light years away,
00:32:25halfway to the center of the Milky Way, halfway to the center of the Milky Way galaxy.
00:32:29The Arecibo Observatory has been used, although sparingly, to search for signals from civilizations in space,
00:32:40and just once, and just once, to broadcast a message to a distant star cluster called M-13.
00:32:49But is there anyone out there to talk to?
00:32:57With 400 billion stars in the Milky Way galaxy alone, could ours be the only one with an inhabited planet?
00:33:08How much more likely it is that the galaxy is throbbing and humming with advanced societies.
00:33:18Perhaps near one of those pinpoints of light in our night sky,
00:33:22someone quite different from us is glancing idly at the star we call the sun
00:33:27and entertaining, just for a moment, an outrageous speculation.
00:33:44There are an enormous number of stars.
00:33:49Only some of them will have planets suitable for life.
00:33:52On only some of those worlds will intelligence arise.
00:33:59And perhaps a few of those civilizations will avoid the trap jointly set by their technology and their passions.
00:34:10If there are many civilizations, one of them should be rather close by.
00:34:16If there are few civilizations, then even the nearest may be very far away.
00:34:22This is one of the great questions.
00:34:33How many advanced civilizations capable, at least of radio astronomy, are there in the Milky Way galaxy?
00:34:40Let's call the number of such civilizations by the capital letter N.
00:34:46It's a number. It depends on many things.
00:34:48It depends on the total number of stars in the Milky Way.
00:34:51Let's call that N sub star.
00:34:54It depends on the fraction of stars that have planets.
00:34:57Let's call that F sub p.
00:35:00It depends on the average number of planets in a given solar system that are ecologically suitable for life.
00:35:05Let's call that N sub e.
00:35:07It depends on the fraction of suitable planets in which life actually arises.
00:35:13Call that F sub l.
00:35:14It depends on the fraction of inhabited planets on which intelligence emerges.
00:35:20Let's call that F sub i.
00:35:21And on the fraction of those planets in which the intelligent beings evolve a technical communicative civilization.
00:35:31Call that F sub c.
00:35:33Finally, it depends on the fraction of a planet's lifetime that's graced by a technical civilization.
00:35:41Call that F sub l.
00:35:42If we multiply all these numbers together, we've estimated capital N, the number of civilizations.
00:35:52This equation, due mainly to Frank Drake of Cornell, is only a sentence.
00:35:58The verb is equals.
00:36:00So let's try to go through the program of this equation.
00:36:05By carefully counting the number of stars in small but representative regions of the sky,
00:36:11we find that the total number of stars in the Milky Way is about 400 billion.
00:36:20That's a lot of stars.
00:36:22What about planets?
00:36:23Well, in studies of double stars, in investigations of the motions of nearby stars,
00:36:31and in many theoretical studies, we get a strong hint that many, perhaps even most stars,
00:36:41are accompanied by planets.
00:36:42So let's take F sub p, the fraction of stars that have planets, as a quarter.
00:36:50Then the total number of planetary systems in the galaxy is 400 billion times a quarter, or 100 billion.
00:36:59We'll write down our running totals in red.
00:37:04Now, if each system were to have, say, 10 planets, as ours does, there would be 100 billion times 10,
00:37:10or a trillion worlds in the galaxy, a vast arena for the cosmic drama.
00:37:18In our own solar system, there are several bodies that might be suitable for life,
00:37:23life of some sort.
00:37:24There's the Earth, of course, but there are possibilities for Mars, for Titan, perhaps for
00:37:30Jupiter.
00:37:31If other systems are similar, there may be many suitable worlds per system, but to be conservative,
00:37:38let's choose n sub e equal two, two worlds suitable for life per system.
00:37:44Then the number of planets in the galaxy that is suitable for life would be 100 billion times
00:37:47two, or 200 billion.
00:37:49Now, what about life?
00:37:51Under very general cosmic conditions, the molecules of life are readily made.
00:37:56They spontaneously self-assemble.
00:37:59It's conceivable that it might be some impediment, like some difficulty in the origin of the genetic
00:38:04code, say, although I think that's very unlikely given billions of years for evolution.
00:38:09On the Earth, life arose very fast after the planet was formed.
00:38:14So, let's choose f sub l, the fraction of suitable worlds in which life does arise,
00:38:20as a half.
00:38:21In that case, the total number of planets in the Milky Way in which life has arisen once
00:38:26is 100 billion times two times a half, or again, 100 billion.
00:38:30A hundred billion inhabited worlds.
00:38:39Now, the estimates get tougher.
00:38:43Many individually unlikely events had to occur for our species and our technology to emerge.
00:38:49On the other hand, there might be many different roads to high technology.
00:38:53Some scientists think that the path from trilobites to radio telescopes, or the equivalent,
00:39:01goes like a shot in all planetary systems.
00:39:03Other scientists disagree.
00:39:06Let's take some middle ground and choose f sub i as a tenth and f sub c is also a tenth,
00:39:15meaning that only one percent, a tenth times a tenth, of inhabited planets eventually produce
00:39:20a technical civilization.
00:39:23If we were to multiply all these factors together, we would find 100 billion times a tenth times a tenth,
00:39:30or one billion planets, on which civilizations have arisen at least once.
00:39:41Now, what percentage of the lifetime of a planet is marked by a technical civilization?
00:39:47The Earth has harbored a civilization capable of radio astronomy only for a few decades,
00:39:53the last few decades, out of a lifetime of a few billion years.
00:39:57It's hardly out of the question that we might destroy ourselves tomorrow.
00:40:02If that's a typical case, then f sub big L would be a few decades divided by a few billion years,
00:40:11or one hundred millionth, a very small number, and then big N would be a billion times a hundred millionth,
00:40:22or N maybe just ten, ten civilizations, a tiny smattering of pitiful few technological civilizations in the galaxy.
00:40:35But civilizations then might take billions of years of tortuous evolution to arise,
00:40:42and then snuff themselves out in an instant of unforgivable neglect.
00:40:47If this is a typical case, there may be few others, maybe nobody else at all for us to talk to.
00:40:54But consider the alternative, that occasionally civilizations learn to live with high technology
00:41:05and survive for geological or stellar revolutionary timescales if only one percent of civilizations can
00:41:13survive technological adolescence. Then f sub big L would be not a hundred millionth,
00:41:20but only a hundredth. And then the number of civilizations would be a billion times a hundredth.
00:41:28The number of civilizations in the galaxy then would be measured in the millions.
00:41:36Millions of technical civilizations.
00:41:38So, if civilizations do not always destroy themselves shortly after discovering radio astronomy,
00:41:51then the sky may be softly humming with messages from the stars,
00:41:57with signals from civilizations enormously older and wiser than we.
00:42:01If there are millions of technical civilizations in the Milky Way, each capable of radio astronomy,
00:42:11how far away is the nearest one?
00:42:20If they're distributed more or less randomly through space, then the nearest one will be some 200 light-years away.
00:42:27But within 200 light-years, there are hundreds of thousands of stars.
00:42:33To find the needle in this haystack requires a dedicated and systematic search.
00:42:43There are many cosmic radio sources having nothing to do with intelligent life.
00:42:47So, how would we know that we were receiving a message?
00:42:51The transmitting civilization could make it very easy for us if they wished.
00:43:01Imagine we're in the course of a systematic search or in the midst of some more conventional radio observations.
00:43:08And suppose one day we find a strong signal slowly emerging, not just some background hiss,
00:43:16but a methodical series of pulses.
00:43:25The numbers 1, 2, 3, 5, 7, 11, 13, a signal made of prime numbers, numbers divisible only by one and themselves.
00:43:37There is no natural astrophysical process that generates prime numbers.
00:43:46We would have to conclude that someone fond of elementary mathematics was saying hello.
00:43:53This would be no more than a beacon to attract our attention.
00:44:03The main message will be subtler, more hidden, far richer.
00:44:08We may have to work hard to find it.
00:44:10But the beacon signal alone would be profoundly significant.
00:44:20It would mean that someone has learned to survive technological adolescence,
00:44:25that self-destruction is not inevitable, that we also may have a future.
00:44:31Such knowledge, it seems to me, might be worth a great price.
00:44:46Very likely, some new Champollion would go on to decode the main message,
00:44:51using our interstellar Rosetta Stone, the common language of science and mathematics.
00:45:01Think of the glories of an exotic civilization far more advanced than we,
00:45:08collected by the great radio telescopes of Earth.
00:45:12Perhaps they would send a compilation of the knowledge of a million inhabited worlds,
00:45:17the Encyclopedia Galactica.
00:45:25The receipt of an interstellar message would be one of the major events in human history,
00:45:29and the beginning of the deprovincialization of our planet.
00:45:41A serious and systematic radio search for extraterrestrial civilizations may come soon.
00:45:48Preliminary steps are being taken both in the United States and in the Soviet Union.
00:45:53It's comparatively inexpensive.
00:45:58A search taking decades would cost less than the budget overruns on a single modest weapons system
00:46:06in a single year.
00:46:10Our technology is now fully adequate for this great challenge.
00:46:16But no systematic search program has ever been approved by any nation on Earth.
00:46:25When will we decide to search for what other civilizations there may be in the vast cosmic ocean?
00:46:32But whether there are only a few advanced galactic civilizations, or millions,
00:46:44shouldn't some of them have voyaged to Earth?
00:46:47On the one hand, we've argued that if even a small fraction of technical civilizations learn
00:46:58to live with themselves and their potential for self-destruction, then there should by now be
00:47:03enormous numbers of them in the galaxy. On the other hand, despite claims about UFOs and ancient astronauts,
00:47:11there's no credible evidence that the Earth has been visited now or ever. But isn't this a contradiction?
00:47:17If the nearest civilization is, say, 200 light years away, it would take them only 200 years to get
00:47:24from there to here at the speed of light. Even if they were traveling a thousand times slower than that,
00:47:30beings from a nearby civilization could have come here during the tenure of human beings on the Earth.
00:47:35So why aren't they here? There's many possible answers. One is that maybe we're the first. Some
00:47:43technical civilization has to be first to emerge in the history of the galaxy. Or maybe all technical
00:47:50civilizations promptly destroy themselves. That seems to me very unlikely. Or maybe there's some
00:47:57problem with interstellar spaceflight that we've been too dumb to figure out. Or maybe they are here.
00:48:04But in hiding, because of some ethic of non-interference with emerging civilizations,
00:48:10we might imagine them curious and dispassionate, watching us to determine whether,
00:48:17this year again, we manage to avoid self-destruction. But there's another explanation which is consistent
00:48:24with everything else we know. And that's that it's a big cosmos. If a great many years ago,
00:48:31an advanced interstellar spacefaring civilization emerged 200 light years away, why would they come
00:48:37here? They would have no reason to think there was something special about the Earth. There are no
00:48:42signs of human technology, not even our radio transmissions, which have had time to go 200
00:48:48light years. From their point of view, all nearby planetary systems might seem equally attractive for
00:48:54exploration. How would an interstellar civilization set out to explore its neighboring star systems?
00:49:07It might establish staging posts, colonies, on planets of nearby stars. But this would take time,
00:49:14time to find and modify favorable planets, time to build new spacecraft. Eventually, later generations
00:49:23of explorers would set out, wending their way among the worlds, creating an interstellar nervous system,
00:49:29binding up the stars. Perhaps they would come upon another expanding civilization and encounter beings
00:49:37previously known only from their radio transmissions. Star Wars are unlikely. One civilization almost
00:49:45certainly would be far more advanced than the other. It would be no contest.
00:49:53Perhaps they would cooperate, exploring together a small province of the Milky Way.
00:49:59But even nearby civilizations could spend millions of years roving between the stars without ever
00:50:11stumbling upon our obscure solar system. In a galaxy of 400 billion suns, perhaps no one has found us just yet.
00:50:23But advanced interstellar civilizations would know about many worlds, some inhabited, some barren. Perhaps they
00:50:34would share their findings, assembling some vast repository of the knowledge of countless worlds. They might compile
00:50:44an encyclopedia Galactica. Suppose we could browse through that encyclopedia.
00:50:53We would choose some nearby province of the galaxy, a region that's fairly well explored, and then slowly
00:51:08a leaf through the worlds.
00:51:20The young Champollion was inspired by reading Fourier's description of Egypt. Imagine the impact on us if we could study a rich compilation of not merely one world, but billions.
00:51:46Billions.
00:51:48Billions.
00:51:50Billions.
00:51:52Billions.
00:51:54Billions.
00:51:56Billions.
00:51:58Billions.
00:52:00Just possibly, not too far from our solar system,
00:52:28we might find a planet with a technical civilization only a little more advanced than we.
00:52:34Let's look them up in the Galactic Encyclopedia.
00:52:58What would a civilization far more advanced than ours be up to?
00:53:20Elsewhere, there may be engineering on a scale that dwarfs our proudest achievements.
00:53:30There may be cultures that disassemble other planets in their system
00:53:34and reassemble them around their world to make a ring or a shell with their planet inside.
00:53:41Imagine the energy crisis of a really advanced planetary civilization.
00:53:59They've used up all their fuels.
00:54:01They depend on solar power.
00:54:04But their growth is still severely limited by the energy available.
00:54:07An enormous amount of energy is generated by the local star.
00:54:11But most of the star's light doesn't fall on their planet.
00:54:15So perhaps they would build a shell to surround their star
00:54:20and harvest every photon of sunlight.
00:54:25Such beings, such civilizations, would bear little resemblance to anything we know.
00:54:31Perhaps someday, there will be an end of the world.
00:55:01An entry in the Encyclopedia Galactica for our planet.
00:55:05Or perhaps, even now, there exists somewhere a planetary dossier
00:55:10garnered from our television broadcasts or from some discreet survey mission.
00:55:16They might summon up the index of blue worlds in our province of the Milky Way
00:55:20until they came to the listing for Earth.
00:55:24What would they know about us?
00:55:25What would they think of us?
00:55:33What would they think of us?
00:55:33We have always watched the stars and mused
00:55:58about whether there are other beings who think and wonder.
00:56:05In a cosmic setting, vast and old, beyond ordinary human understanding,
00:56:10we are a little lonely.
00:56:12In the deepest sense, the search for extraterrestrial intelligence
00:56:21is a search for who we are.
00:56:25Since Cosmos was first released, interest in UFOs has persisted.
00:56:39It seems to me that there are fewer sightings of strange objects in the skies these days
00:56:44and more stories about personal encounters with alleged extraterrestrials,
00:56:50like the account of Betty and Barney Hill that we dramatized.
00:56:53There are still people who claim to have been abducted by aliens
00:56:57or even sexually abused or even impregnated by them.
00:57:02Best-selling, purportedly serious books have been written about such claims.
00:57:07But the critical fact remains that all we have still is just an anecdote.
00:57:12There are no close-up photographs, no artifacts,
00:57:15nothing that would convince a skeptic.
00:57:18All there are is stories.
00:57:19And stories just aren't good enough on a matter of this importance.
00:57:25I'm still waiting for hard evidence.
00:57:28The radio search for extraterrestrial intelligence has been picking up.
00:57:32In Harvard, Massachusetts, a radio telescope monitoring 8 million separate radio channels
00:57:38has been scanning the skies for signals.
00:57:41This program, called META, is supported entirely by the Pasadena, California-based Planetary Society,
00:57:48paid for by members' contributions.
00:57:51A similar Planetary Society search to examine the southern skies,
00:57:56including the center of the Milky Way galaxy,
00:57:58is to be performed in Argentina.
00:58:01These searches are, by far, the most sophisticated ever attempted.
00:58:06A much more sensitive program, covering almost the entire accessible radio spectrum,
00:58:13is to be mustered by NASA.
00:58:16The search for extraterrestrial intelligence is central to our understanding of the universe
00:58:21and our view of ourselves.
00:58:23It's well worth doing.
00:58:24But the simple fact is that, while we may consider extraterrestrial intelligence highly likely,
00:58:32there is as yet no evidence at all that it exists.
00:58:37The search continues.
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