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00:00:30In the vastness of the cosmos, there must be other civilizations far older and more advanced than ours.
00:00:58So, shouldn't we have been visited? Shouldn't there be, every now and then, alien ships in the skies of Earth?
00:01:08There's nothing impossible in this idea, and no one would be happier than me if we were being visited.
00:01:13But has it happened in fact? What counts is not what sounds plausible, not what we'd like to believe, not what one or two witnesses claim,
00:01:23but only what is supported by hard evidence, rigorously and skeptically examined. Extraordinary claims require extraordinary evidence.
00:01:38Since 1947, there have been hundreds of thousands of reports of UFOs, unidentified flying objects.
00:01:47This subject has more, I think, to do with religion and superstition than with science.
00:01:53Let's consider one of the most famous accounts of a supposed encounter with alien beings.
00:01:59On September 19th, 1961, an American couple were driving home through New Hampshire.
00:02:05What's the matter, Kelsey?
00:02:08They were returning along a lonely road late at night from a vacation in Canada.
00:02:15Remember, we have only their word for what happened next.
00:02:20They had observed, so they said, a strange moving light in the sky. By definition, an unidentified flying object.
00:02:47It seemed to follow them for miles.
00:02:50What's the matter? What's the matter with that dog?
00:02:53I don't know.
00:03:05After a time, the lighting patterns on the UFO changed.
00:03:10It appeared to land.
00:03:13It blocked the road, preventing them from driving on.
00:03:29They said they saw mouthless creatures approaching, who were not exactly human.
00:03:36Barney? Barney? Barney, what is that?
00:03:43At this point, the story becomes still stranger.
00:03:46They lost all recollection of what happened in the next few hours.
00:03:54But weeks later, they said, they recalled some details and discussed the experience with others.
00:04:01Twenty-six months later, under hypnosis, they reported that a UFO had landed and that the crew had emerged.
00:04:14They were captured, they said, and taken aboard the craft.
00:04:28That was the story told by Betty and Barney Hill.
00:04:31Virtually all scientists who've studied it are skeptical.
00:04:35But UFO enthusiasts think the Hill case is a classic example of a close encounter of the third kind.
00:04:50Why? What makes it so special?
00:05:06While on board, Betty had noticed a book written in an unknown hieroglyphic writing.
00:05:11She was also shown a strange window through which she could see a glowing pattern of dots connected with lines.
00:05:20It was, they told her, a star map displaying the routes of interstellar commerce.
00:05:26Afterwards, the Hills were released and permitted to return home.
00:05:30Or at least, this is their story.
00:05:31Now, believers find this account compelling, or at least plausible, chiefly because of the alleged star map.
00:05:39Here's what Betty Hill said it looked like.
00:05:42Now, why would anybody take this seriously?
00:05:45Because here is a real map, widely publicized by UFO enthusiasts, of 15 selected nearby stars, including the sun, as seen from one particular vantage point in space.
00:05:57This map includes stars that were first catalogued several years after Betty Hill recalled what she said she saw in the alien ship.
00:06:07Her map required, we are told, information that was not then available on the Earth.
00:06:13There is a resemblance between the two maps, but that's mainly because the lines corresponding to navigation routes have been copied from the Hill map onto the real star map.
00:06:23If we were to substitute some other set of lines for the Hill lines, we find that the eye suddenly is biased against seeing any agreement between the two maps at all.
00:06:36To make an objective test, however, let's remove the lines altogether.
00:06:41And then there is very little resemblance left.
00:06:48But these particular stars are selected from a large catalog of star positions.
00:06:53Our vantage point in space is also selected to make the best possible fit with the Hill map.
00:06:58If you can pick and choose from a large number of stars, viewed from any vantage point in space you want, you can always find something resembling the pattern you're looking for.
00:07:10I'm surprised that nobody could find a better fit to the Hill map.
00:07:14The Hill's own psychiatrist described their story as a kind of dream.
00:07:21There's no corroborating evidence, the star map argument is worthless, and yet this is one of the best attested cases of UFO close encounters.
00:07:31For all I know, we may be visited by a different extraterrestrial civilization every second Tuesday.
00:07:36But there's no support for this appealing idea. The extraordinary claims are not supported by extraordinary evidence.
00:07:46There are curious daylight photos of UFOs.
00:07:53Some look suspiciously like hats or hubcaps thrown into the air. Photos can be faked.
00:08:00More common are unidentified lights at night. They're often aircraft. But if we can't identify a light, that doesn't make it a spaceship.
00:08:18Here's a movie of what you might think is a UFO. Actually, it's a piece of an asteroid burning up as it enters the Earth's atmosphere.
00:08:30Most reports of unidentified flying objects turn out to be something else, like the refracted image of a bright planet or the re-entry of an artificial satellite.
00:08:43Some are psychological aberrations. Some are hoaxes.
00:08:46Never is there any compelling physical evidence, a detailed close-up photograph of a strange spacecraft or a small device of extraterrestrial manufacturer, a book written in alien hieroglyphics.
00:09:01Never. There are reports of such things, but never the things themselves.
00:09:06The search for alien civilizations retains its importance, despite the striking failure of the UFO evidence.
00:09:18Most astronomers, for example, consider extraterrestrial life a subject worthy of vigorous, if cautious, pursuit.
00:09:24For myself, I find something irresistible in the idea of discovering a token, maybe a simple inscription, which would provide the key to understanding an alien and exotic civilization.
00:09:38This is an appeal we humans have felt before.
00:09:41In 1801, a famous physicist was the governor of the French province of Isser.
00:10:02His name was Joseph Fourier.
00:10:03On a routine inspection of the schools in his province, Fourier discovered an exceptional 11-year-old boy, Jean-Francois Champollion.
00:10:18The boy's precocious intellect and remarkable flair for languages had already earned him the admiring attention of local scholars. Fourier, too, was impressed.
00:10:38What Champollion first saw in Fourier's house determined the course of his life and unlocked the secrets of an alien civilization.
00:10:47Fourier had recently participated as one of many scientists in Napoleon's expedition to the Middle East.
00:10:57He had been in charge of cataloguing the astronomical monuments of Egypt.
00:11:04The boy was entranced by Fourier's collection of ancient Egyptian artifacts, the mysterious fragments of a lost world.
00:11:17France at this time was flooded with such artifacts, plundered by Napoleon, and now a rousing intense interest among scholars and the general public.
00:11:30The boy's attention was caught by a specimen of Egyptian hieroglyphics.
00:11:47What do they mean, he asked?
00:12:03Nobody knows, was Fourier's reply.
00:12:05Then and there, Champollion resolved that he would understand this language that no one could read, that he would decode the messages from another world and another time.
00:12:17He became a superb linguist and immersed himself in the hieroglyphics.
00:12:21Fourier edited the illustrated description of Napoleon's expedition.
00:12:33The young Champollion studied it hungrily.
00:12:38To the people of Europe, these exotic images revealed an utterly alien civilization.
00:12:43A world of towering monuments and magical names, Dendera, Karnak, Luxor.
00:12:58Every illustration was a riddle posed by the past to the present.
00:13:02And among them were pictures of something called the Rosetta Stone.
00:13:13And portraits of the people who lived among the ruins of the pharaohs.
00:13:21Egypt became the land of Champollion's dreams.
00:13:26But it was not until 1828, 27 years after his fateful visit with Fourier, that Champollion first set foot in Egypt.
00:13:45With 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.
00:14:06It was a journey of many weeks, which Champollion recorded in extraordinary detail.
00:14:26This was an expedition through time, a voyage across the centuries to another world.
00:14:33Champollion, as an adult, had already worked out a brilliant decipherment of the hieroglyphics.
00:14:47A word, incidentally, that means sacred carvings.
00:14:54Now Champollion was making a pilgrimage to the scene of the ancient mysteries he had been the first to understand.
00:15:01Patrick boy lived on the first to understand.
00:15:04New Beach
00:15:07nuestros
00:15:10nuestros
00:15:18nuestros
00:15:24Champollion wrote,
00:15:32The evening of the 16th, we finally arrived at Dendera.
00:15:44We were only an hour away from the temples.
00:15:51Could we resist the temptation?
00:15:53I ask the coldest of you mortals.
00:16:01To dine and leave immediately were the orders of the moment.
00:16:12Alone and without guides, we crossed the fields.
00:16:16Presuming that the temples were in a straight line from our boat, we walked thus for an hour and a half without finding anything.
00:16:27We finally discovered a man who put us on the correct route and ended up walking with us with good graces.
00:16:33The temple appeared to us at last.
00:16:43I shall not try to describe the impression which the porches and above all the portico made on us.
00:17:00We stayed there two hours in ecstasy, running through the huge rooms and trying to read the exterior inscriptions in the moonlight.
00:17:14It was with no small rapture that Champollion entered the secret places of the temple and scanned the words that had waited patiently through half a million nights for a reader.
00:17:32To his brother, Champollion wrote of his joy in confirming that he could understand the writing on these walls.
00:17:42I am now proud, he said, that having followed the course of the Nile to the second cataract, I have the right to announce that there is nothing to modify in our letter on the alphabet of hieroglyphics.
00:17:56Our alphabet is good, it is applicable with the same success, first of all in Egyptian monuments of the epoch of the Romans, and also, which is more interesting, to the inscriptions on all temples, palaces and tombs of the pharaonic epoch.
00:18:26Champollion was overwhelmed by the grandeur which surrounded him.
00:18:32It is the union, he said, of grace and majesty in the highest degree.
00:18:39We in Europe are only dwarfs.
00:18:41No nation, ancient or modern, has conceived the art of architecture on such a sublime, great and imposing style as the ancient Egyptians.
00:18:51They ordered everything to be done for people who are 100 feet high.
00:18:58This is the great temple of Karnak in Upper Egypt, continuously constructed over a period of 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.
00:19:33On these walls and columns at Karnak, at Dendera, and everywhere else in Egypt,
00:19:50Champollion found that he could read the inscriptions that his decipherment of a few years earlier had been correct.
00:20:09But how had he figured it out?
00:20:11Many had tried and failed to read the hieroglyphics.
00:20:18One 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.
00:20:28Birds, especially birds, lots of birds.
00:20:33There were those who deduced from the hieroglyphics that the Egyptians had been colonists from China.
00:20:42There were those who deduced it the other way around.
00:20:48There was one character who, from a single look at the Rosetta Stone, deduced its meaning.
00:20:54He said that the quickness of his decipherment enabled him to avoid the systematic errors which invariably arise from prolonged reflection.
00:21:04You get better results, he was saying, if you don't think about it too much.
00:21:09As in the search for extraterrestrial intelligence today,
00:21:13the unbridled speculation by amateurs served to frighten many professionals right out of the field.
00:21:24Champollion was not frightened.
00:21:33He was also not distracted by the idea of hieroglyphs as pictorial metaphors.
00:21:38Instead, using the insights of a brilliant English physicist named Thomas Young,
00:21:45he proceeded something like this.
00:21:47This is an exact replica of the Rosetta Stone.
00:21:52The original had been found in the year 1799 by a French soldier working on the fortifications of the Nile Delta town of Rashid,
00:22:01which the Europeans, in their persistence not to learn Arabic, called Rosetta.
00:22:07It had been part of an ancient temple which had been torn down.
00:22:12If we look at it, we see that it clearly represents the same text in three different languages.
00:22:20Up at the top, ancient Egyptian hieroglyphics.
00:22:24In the middle, a kind of cursive and later hieroglyphic called Demotic.
00:22:29And down at the bottom, the key to the enterprise, Greek.
00:22:33Champollion could, of course, read ancient Greek.
00:22:35He was a superb linguist.
00:22:38And discovered that this stone had been inscribed to commemorate the coronation of King Ptolemy V Epiphanes in the spring of the year 196 BC.
00:22:52As we would expect, the Greek text includes many references to King Ptolemy.
00:22:57Here, for example, you can see it.
00:22:59Ptolemy V Epiphanes
00:23:01Now, in roughly the same positions, but in the hieroglyphic text, are these ovals or cartouches, as they're called.
00:23:14And if this cartouche really means Ptolemy, then the individual hieroglyphs are unlikely to be pictograms or metaphors.
00:23:23Much more likely they're letters, or at least syllables.
00:23:27In 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.
00:23:47Again implying that the hieroglyphs are mainly letters and syllables.
00:23:51But which hieroglyphs correspond to which letters?
00:23:56Fortunately, Champollion had available to him a kind of second Rosetta Stone, an obelisk which had been excavated at the Temple of Philae,
00:24:05and which had inscribed upon it cartouches representing the hieroglyphic equivalent of another Greek name, Cleopatra.
00:24:18So here we have the Cleopatra cartouche, and here is the Ptolemaeus cartouche.
00:24:27Here we've turned it around, changing left to right to right to left, and spread the hieroglyphs out so we can see them all.
00:24:33Now immediately we notice that there are some similarities.
00:24:38This first hieroglyph in Ptolemy is a kind of square.
00:24:42The fifth hieroglyph in Cleopatra is a square.
00:24:45But Cleopatra, both of them seem to represent a P.
00:24:52So Ptolemy and Cleopatra both give us the same interpretation.
00:24:58A square is a P.
00:25:00Likewise, the fourth hieroglyph in Ptolemy is a lion.
00:25:07Ptole, P-T-O-L.
00:25:10Likewise, the second hieroglyph in Cleopatra is an L.
00:25:15So again, it's consistent.
00:25:17The pattern is emerging.
00:25:19Likewise, this rope or hangman's noose, Pto-O-L-O-Mi.
00:25:25It's an O.
00:25:26Cleopatra, it's an O.
00:25:29And in this way, Champollion was able to assign letters for each of the hieroglyphs we see here.
00:25:38Ptolemy's, and likewise, Cleopatra.
00:25:50The eagle is an A.
00:25:53You notice there are two different symbols for T, but in English, same sort of thing, F and PH.
00:26:00Champollion discovered that the hieroglyphs were basically a simple substitution cipher.
00:26:05Now, there's other stuff in here.
00:26:08All the rest of this in the cartouche, what's that about?
00:26:11Well, he was later able to find out.
00:26:13This is a symbol called the Ankh, which means life.
00:26:16Here, there's a P-T, and that's a H.
00:26:19It makes Ptach, the name of a god.
00:26:21And the whole cartouche read, Ptolemy, ever-living, beloved of the god Ptach.
00:26:29Likewise, 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.
00:26:39Some 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.
00:26:57In retrospect, it sounds almost easy, but it took people hundreds of years before they figured it out.
00:27:07Champollion 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?
00:27:20What a joy it must have been for him to open this one-way communications channel with another civilization.
00:27:28To permit a culture which had been mute for millennia to speak of its history, magic, medicine, religion, politics, philosophy.
00:27:41Today, we also are seeking messages from an ancient and exotic civilization.
00:28:01A civilization hidden from us, not in time, but in space.
00:28:10Today, 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.
00:28:18But 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?
00:28:44Is there in any sense a cosmic Rosetta Stone?
00:28:50I believe there is.
00:28:51All the technical civilizations in the cosmos, no matter how different they are, must have one language in common.
00:28:59The language called science.
00:29:04The laws of nature are everywhere the same.
00:29:07Every chemical element has a specific signature in the spectrum.
00:29:16So there are identical patterns in the light of a candle flame on Earth and in the light of a distant galaxy.
00:29:22The 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.
00:29:38Beings 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.
00:29:51So does our own Milky Way.
00:29:52So does our own Milky Way.
00:29:53The same gravitational forces are at work.
00:29:57And on planets also.
00:29:59There are spiral storm systems on Jupiter.
00:30:05The same patterns are common on Earth.
00:30:10The intelligent beings on every world will sooner or later understand the laws of nature.
00:30:16Some day, 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.
00:30:42If 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.
00:31:03To communicate with other civilizations, our technology must reach across not merely interplanetary distances, but interstellar distances.
00:31:21Ideally, the method should be inexpensive, so that a huge amount of information could be sent and received at very little cost.
00:31:27It should be fast, so an interstellar dialogue is eventually possible.
00:31:34It ought to be obvious, so that any technical civilization, no matter what its evolutionary path, will discover it early.
00:31:44Surprisingly, there is such a method.
00:31:48There is such a method.
00:31:49It's called radio astronomy.
00:31:55This is the largest radio radar telescope on the planet Earth, the Arecibo Observatory.
00:32:06It's located in a remote valley on the island of Puerto Rico.
00:32:09It sends and receives radio signals, but it's so large and powerful that it could communicate with an identical radio telescope 15,000 light years away, halfway to the center of the Milky Way galaxy.
00:32:28The Arecibo Observatory has been used, although sparingly, to search for signals from civilizations in space, and just once, to broadcast a message to a distant star cluster called M13.
00:32:49But is there anyone out there to talk to?
00:33:00With 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, someone quite different from us is glancing idly at the star we call the sun and entertaining just for a moment an outrageous speculation.
00:33:38There are an enormous number of stars.
00:33:48Only some of them will have planets suitable for life.
00:33:53On only some of those worlds will intelligence arise.
00:33:58And perhaps a few of those civilizations will avoid the trap jointly set by their technology and their passions.
00:34:08If there are many civilizations, one of them should be rather close by.
00:34:15If there are few civilizations, then even the nearest may be very far away.
00:34:21This is one of the great questions. How many advanced civilizations capable, at least of radio astronomy, are there in the Milky Way galaxy?
00:34:39Let's call the number of civilizations by the capital letter N.
00:34:46It's a number. It depends on many things.
00:34:49It depends on the total number of stars in the Milky Way. Let's call that N sub star.
00:34:55It depends on the fraction of stars that have planets. Let's call that F sub P.
00:34:59It depends on the average number of planets in a given solar system that are ecologically suitable for life. Let's call that N sub B.
00:35:09It depends on the fraction of suitable planets in which life actually arises. Let's call that F sub L.
00:35:14It depends on the fraction of inhabited planets on which intelligence emerges. Let's call that F sub I.
00:35:23And on the fraction of those planets in which the intelligent beings evolve a technical communicative civilization. Call that F sub C.
00:35:32Finally, it depends on the fraction of a planet's lifetime that's graced by a technical civilization. Call that F sub L.
00:35:45If we multiply all these numbers together, we've estimated capital N, the number of civilizations.
00:35:53This equation, due mainly to Frank Drake of Cornell, is only a sentence. The verb is equals.
00:35:59So, let's try to go through the program of this equation. By 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. That's a lot of stars.
00:36:21What about planets? Well, in studies of double stars, in investigations of the motions of nearby stars, and in many theoretical studies,
00:36:34we get a strong hint that many, perhaps even most stars, are 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, ten planets, as ours does, there would be 100 billion times ten,
00:37:11or a trillion worlds in the galaxy, a vast arena for the cosmic drama.
00:37:16In our own solar system, there are several bodies that might be suitable for life, life of some sort.
00:37:25There's the Earth, of course, but there are possibilities for Mars, for Titan, perhaps for Jupiter.
00:37:31If other systems are similar, there may be many suitable worlds per system, but to be conservative,
00:37:37let'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 are suitable for life would be 100 billion times two, or 200 billion.
00:37:50Now, what about life? Under very general cosmic conditions, the molecules of life are readily made.
00:37:57They spontaneously self-assemble. It's conceivable that it might be some impediment,
00:38:02like some difficulty in the origin of the genetic code, say,
00:38:05although 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, as...
00:38:20A half.
00:38:22In 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.
00:38:34A 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.
00:38:50On 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.
00:39:04Other scientists disagree.
00:39:06Let's take some middle ground and choose F sub I as a tenth,
00:39:11a tenth, and F sub C as also a tenth, meaning that only one percent, a tenth times a tenth,
00:39:19of inhabited planets eventually produce a 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,
00:39:54the last few decades, out of a lifetime of a few billion years.
00:39:58It'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.
00:40:18And then, big N would be a billion times a hundred millionth,
00:40:22or in maybe just ten, ten civilizations, a tiny smattering of pitiful few.
00:40:32technological civilizations in the galaxy.
00:40:36But, civilizations then might take billions of years of tortuous evolution to arise,
00:40:43and then snuff themselves out in an instant of unforgivable neglect.
00:40:48If 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 and survive for geological or stellar revolutionary timescales.
00:41:08If only one percent of civilizations can survive technological adolescence, then F sub big L would be not a hundred millionth, but only a hundredth.
00:41:22And then the number of civilizations would be a billion times a hundredth.
00:41:29The number of civilizations in the galaxy then would be measured in the millions, millions 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, how far away is the nearest one?
00:42:16If they are distributed more or less randomly through space, then the nearest one will be some 200 light years away.
00:42:26But 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.
00:42:48So, 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.
00:43:00Imagine we are in the course of a systematic search, or in the midst of some more conventional radio observations.
00:43:07And suppose one day, we find a strong signal slowly emerging, not just some background hiss, but a methodical series of pulses.
00:43:20The numbers 1, 2, 3, 5, 7, 11, 13, a signal made of prime numbers.
00:43:34Numbers divisible only by one, and themselves.
00:43:37There is no natural astrophysical process that generates prime numbers.
00:43:44We would have to conclude that someone fond of elementary mathematics was saying, hello.
00:43:51This 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.
00:44:28That 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,
00:44:52using 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.
00:45:13Perhaps they would send a compilation of the knowledge of a million inhabited worlds,
00:45:18the 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.
00:45:52It's comparatively inexpensive.
00:45:55A search taking decades would cost less than the budget overruns on a single modest weapons system in a single year.
00:46:06Our technology is now fully adequate for this great challenge, but no systematic search program has ever been approved by any nation on Earth.
00:46:21When will we decide to search for what other civilizations there may be in the vast cosmic ocean?
00:46:33But whether there are only a few advanced galactic civilizations, or millions, shouldn'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 to live with themselves and their potential for self-destruction,
00:47:02then there should by now be enormous numbers of them in the galaxy.
00:47:05On the other hand, despite claims about UFOs and ancient astronauts, there's no credible evidence that the Earth has been visited, now or ever.
00:47:15But isn't this a contradiction?
00:47:18If the nearest civilization is, say, 200 light years away, it would take them only 200 years to get from there to here at the speed of light.
00:47:26Even if they were traveling a thousand times slower than that, beings from a nearby civilization could have come here during the tenure of human beings on the Earth.
00:47:36So why aren't they here?
00:47:38There's many possible answers. One is that maybe we're the first.
00:47:43Some technical civilization has to be first to emerge in the history of the galaxy.
00:47:47Or maybe all technical civilizations promptly destroy themselves. That seems to me very unlikely.
00:47:56Or maybe there's some problem with interstellar space flight that we've been too dumb to figure out.
00:48:01Or 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, this year again, we manage to avoid self-destruction.
00:48:21But there's another explanation which is consistent with everything else we know.
00:48:26And that's that it's a big cosmos.
00:48:30If a great many years ago, an advanced interstellar space-faring civilization emerged 200 light years away, why would they come here?
00:48:37They would have no reason to think there was something special about the Earth.
00:48:42There are no signs of human technology, not even our radio transmissions, which have had time to go 200 light years.
00:48:49From their point of view, all nearby planetary systems might seem equally attractive for exploration.
00:49:00How would an interstellar civilization set out to explore its neighboring star systems?
00:49:05It might establish staging posts, colonies, on planets of nearby stars.
00:49:12But this would take time, time to find and modify favorable planets, time to build new spacecraft.
00:49:19Eventually, later generations of explorers would set out, wending their way among the worlds, creating an interstellar nervous system, binding up the stars.
00:49:31Perhaps they would come upon another expanding civilization and encounter beings previously known only from their radio transmissions.
00:49:41Star Wars are unlikely.
00:49:44One civilization almost certainly would be far more advanced than the other.
00:49:48It would be no contest.
00:49:49No contest.
00:49:53Perhaps they would cooperate, exploring together a small province of the Milky Way.
00:50:00But even nearby civilizations could spend millions of years roving between the stars without ever stumbling upon our obscure solar system.
00:50:14In a galaxy of 400 billion suns.
00:50:17In a galaxy of 400 billion suns.
00:50:21Perhaps no one has found us, just yet.
00:50:23But advanced interstellar civilizations would know about many worlds, some inhabited, some barren.
00:50:33Perhaps they would share their findings, assembling some vast repository of the knowledge of countless worlds.
00:50:41They might compile an encyclopedia Galactica.
00:50:49Suppose we could browse through that encyclopedia.
00:50:52We would choose some nearby province of the galaxy, a region that's fairly well explored, and then slowly leaf through the worlds.
00:51:09The young Champollion was inspired by reading Fourier's description of Egypt.
00:51:37Imagine the impact on us, if we could study a rich compilation of not merely one world, but billions.
00:51:46Billions.
00:52:16Just possibly, not too far from our solar system, we might find a planet with a technical civilization only a little more advanced than we.
00:52:33Let's look them up in the galactic encyclopedia.
00:52:38.
00:53:08What would a civilization far more advanced than ours be up to?
00:53:24Elsewhere, 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.
00:53:38Or a shell, with their planet inside.
00:53:54Imagine the energy crisis of a really advanced planetary civilization.
00:53:59They've used up all their fuels, they depend on solar power.
00:54:03But 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 and harvest every photon of sunlight.
00:54:23Such beings, such civilizations, would bear little resemblance to anything we know.
00:54:31Perhaps someday...
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