"Hello." "My name is Ann Druyan." "When Carl Sagan, Steven Soter and I wrote the Cosmos TV series in the late 1970s a lot of things where different." "Back then, the U.S. and the Soviet Union held the hole planet in their perpetual hostage crisis called the Cold War." "The wealth and scientific ingenuity of our civilization was being squandered on a runaway arms raise." "Then employed half the world scientists and infested the world with 50.000 nuclear weapons." "So much has happened since then." "The Cold War is history and science has made great strides." "We've completed the spacecraft recognizance of the Solar System the preliminary mapping of the visible universe that surrounds us and we've charted the universe within:" "the human genome." "When Cosmos was first broadcast there was no World Wide Web it was a different world." "What a tribute to Carl Sagan a scientist who took many a punch for daring to speculate that even after 20 of the most eventful years in the history of science Cosmos requires few revisions and indeed is rich in prophecy." "Cosmos is both the history of the scientific enterprise and an attempt to convey the spiritual high of its central revelation:" "Our oneness with the universe." "Now, please, enjoy Cosmos, the proud saga of how through the searching of 40.000 generations of our ancestors we have come to discover our coordinates in space and in time." "And how, through the awesomely powerful method of science we have been able to reconstruct the sweep of cosmic evolution and defined our own part in its great story." "SAGAN:" "The cosmos is all that is or ever was or ever will be." "Our contemplations of the cosmos stir us." "There is a tingling in the spine, a catch in the voice a faint sensation, as if a distant memory of falling from a great height." "We know we are approaching the grandest of mysteries." "The size and age of the cosmos are beyond ordinary human understanding." "Lost somewhere between immensity and eternity is our tiny planetary home, the Earth." "For the first time, we have the power to decide the fate of our planet and ourselves." "This is a time of great danger." "But our species is young and curious and brave." "It shows much promise." "In the last few millennia, we've made the most astonishing and unexpected discoveries about the cosmos and our place within it." "I believe our future depends powerfully on how well we understand this cosmos in which we float like a mote of dust in the morning sky." "(SEA GULL CHIRPS)" "We're about to begin a journey through the cosmos." "We'll encounter galaxies and suns and planets life and consciousness..." "Worlds of ice and stars of diamond." "Atoms as massive as suns and universes smaller than atoms." "But it's also a story of our own planet and the plants and animals that share it with us." "And it's a story about us:" "How we achieved our present understanding of the cosmos how the cosmos has shaped our evolution and our culture and what our fate may be." "We wish to pursue the truth, no matter where it leads." "But to find the truth, we need imagination and skepticism both." "We will not be afraid to speculate." "But we will be careful to distinguish speculation from fact." "The cosmos is full beyond measure of elegant truths of exquisite interrelationships of the awesome machinery of nature." "The surface of the Earth is the shore of the cosmic ocean." "On this shore, we have learned most of what we know." "Recently, we've waded a little way out maybe ankle-deep, and the water seems inviting." "Some part of our being knows this is where we came from." "We long to return." "And we can." "Because the cosmos is also within us." "We're made of star-stuff." "We are a way for the cosmos to know itself." "The journey for each of us begins here." "We're going to explore the cosmos in a ship of the imagination unfettered by ordinary limits on speed and size drawn by the music of cosmic harmonies it can take us anywhere in space and time." "Perfect as a snowflake organic as a dandelion seed it will carry us to worlds of dreams and worlds of facts." "Come with me." "Before us is the cosmos on the grandest scale we know." "We are far from the shores of Earth in the uncharted reaches of the cosmic ocean." "Strewn like sea froth on the waves of space are innumerable faint tendrils of light." "Some of them containing hundreds of billions of suns." "These are the galaxies drifting endlessly in the great cosmic dark." "In our ship of the imagination we are halfway to the edge of the known universe." "In this, the first of our cosmic voyages we begin to explore the universe revealed by science." "Our course will eventually carry us to a far-off and exotic world." "But from the depths of space, we cannot detect even the cluster of galaxies in which our Milky Way is embedded much less the sun or the Earth." "We are in the realm of the galaxies 8 billion light years from home." "No matter where we travel, the patterns of nature are the same as in the form of this spiral galaxy." "The same laws of physics apply everywhere throughout the cosmos." "But we have just begun to understand these laws." "The universe is rich in mystery." "Near the center of a cluster of galaxies there's sometimes a rogue, elliptical galaxy made of a trillion suns which devours its neighbors." "Perhaps this cyclone of stars is what astronomers on Earth call a quasar." "Our ordinary measures of distance fail us here in the realm of the galaxies." "We need a much larger unit:" "the light year." "It measures how far light travels in a year nearly 10 trillion kilometers." "It measures not time, but enormous distances." "In the Hercules cluster the individual galaxies are about 300,000 light years apart." "So light takes about 300,000 years to go from one galaxy to another." "Like stars and planets and people galaxies are born, live and die." "They may all experience a tumultuous adolescence." "During their first 100 million years, their cores may explode." "Seen in radio light, great jets of energy pour out and echo across the cosmos." "Worlds near the core or along the jets would be incinerated." "I wonder how many planets and how many civilizations might be destroyed." "In the Pegasus cluster, there's a ring galaxy the wreckage left from the collision of two galaxies." "A splash in the cosmic pond." "Individual galaxies may explode and collide and their constituent stars may blow up as well." "In this supernova explosion a single star outshines the rest of its galaxy." "We are approaching what astronomers on Earth call the Local Group." "Three million light years across, it contains some 20 galaxies." "It's a sparse and rather typical chain of islands in the immense cosmic ocean." "We are now only 2 million light years from home." "On the maps of space, this galaxy is called M31 the great galaxy Andromeda." "It's a vast storm of stars and gas and dust." "As we pass over it we see one of its small satellite galaxies." "Clusters of galaxies and the stars of individual galaxies are all held together by gravity." "Surrounding M31 are hundreds of globular star clusters." "We're approaching one of them." "Each cluster orbits the massive center of the galaxy." "Some contain up to a million separate stars." "Every globular cluster is like a swarm of bees bound by gravity every bee, a sun." "From Pegasus, our voyage has taken us 200 million light years to the Local Group dominated by two great spiral galaxies." "Beyond M31 is another very similar galaxy." "Its spiral arms slowly turning once every quarter billion years." "This is our own Milky Way seen from the outside." "This is the home galaxy of the human species." "In the obscure backwaters of the Carina-Cygnus spiral arm we humans have evolved to consciousness and some measure of understanding." "This region of the Milky Way galaxy is now usually called the Local Arm or the Orion Arm, but the spiral arm nomenclature remains rather fuzzy." "Concentrated in its brilliant core and strewn along its spiral arms are 400 billion suns." "It takes light 100,000 years to travel from one end of the galaxy to the other." "Within this galaxy are stars and worlds and, it may be, an enormous diversity of living things and intelligent beings and space faring civilizations." "Scattered among the stars of the Milky Way are supernova remnants each one the remains of a colossal stellar explosion." "These filaments of glowing gas are the outer layers of a star which has recently destroyed itself." "The gas is unraveling returning star-stuff back into space." "(PULSAR HISSES)" "And at its heart, are the remains of the original star a dense, shrunken stellar fragment called a pulsar." "A natural lighthouse, blinking and hissing." "A sun that spins twice each second." "Pulsars keep such perfect time that the first one discovered was thought to be a sign of extraterrestrial intelligence." "Perhaps a navigational beacon for great ships that travel across the light years and between the stars." "There may be such intelligences and such starships but pulsars are not their signature." "Instead, they are the doleful reminders that nothing lasts forever that stars also die." "We continue to plummet, falling thousands of light years towards the plane of the galaxy." "This is the Milky Way our galaxy seen edge on." "Billions of nuclear furnaces converting matter into starlight." "Some stars are flimsy as a soap bubble." "Others are 100 trillion times denser than lead." "The hottest stars are destined to die young." "But red giants are mostly elderly." "Such stars are unlikely to have inhabited planets." "But yellow dwarf stars, like the sun are middle-aged and they are far more common." "These stars may have planetary systems." "And on such planets, for the first time on our cosmic voyage we encounter rare forms of matter:" "Ice and rock, air and liquid water." "Close to this yellow star is a small, warm, cloudy world with continents and oceans." "These conditions permit an even more precious form of matter to arise:" "Life." "But this is not the Earth." "Intelligent beings have evolved and reworked this planetary surface in a massive engineering enterprise." "In the Milky Way galaxy, there may be many worlds on which matter has grown to consciousness." "I wonder, are they very different from us?" "What do they look like?" "What are their politics, technology, music, religion?" "Or do they have patterns of culture we can't begin to imagine?" "Are they also a danger to themselves?" "Among the many glowing clouds of interstellar gas is one called the Orion Nebula only 1 500 light years from Earth." "These three bright stars are seen by earthlings as the belt in the familiar constellation of Orion the hunter." "The nebula appears from Earth as a patch of light the middle star in Orion's sword." "But it is not a star." "It is another thing entirely." "A cloud that veils one of nature's secret places." "This is a stellar nursery, a place where stars are born." "They condense by gravity from gas and dust until their temperatures become so high that they begin to shine." "Such clouds mark the births of stars as others bear witness to their deaths." "After stars condense in the hidden interiors of interstellar clouds what happens to them?" "The Pleiades are a loose cluster of young stars only 50 million years old." "These fledgling stars are just being let out into the galaxy." "Still surrounded by wisps of nebulosity the gas and dust from which they formed." "There are clouds that hang like inkblots between the stars." "They are made of fine, rocky dust organic matter and ice." "Inside, a few stars begin to turn on." "Nearby worlds of ice evaporate and form long, comet-like tails driven back by the stellar winds." "Black clouds, light years across drift between the stars." "They're filled with organic molecules." "The building blocks of life are everywhere." "They are easily made." "On how many worlds have such complex molecules assembled themselves into patterns we would call alive?" "Most stars belong to systems of two or three or many suns bound together by gravity." "Each system is isolated from its neighbors by the light years." "We are approaching a single, ordinary, yellow dwarf star surrounded by a system of nine planets dozens of moons, thousands of asteroids and billions of comets:" "The family of the sun." "Only four light hours from Earth is the planet Neptune and its giant satellite, Triton." "Even in the outskirts of our own solar system we humans have barely begun our explorations." "Only a century ago we were ignorant even of the existence of the planet Pluto." "Its moon, Charon, remained undiscovered until 1978." "Since the discovery of Kuiper Belt objects in 1 992, Pluto has come to be seen as the largest member of this population of comets." "The rings of Uranus were first detected in 1977." "Many astronomers no longer regard it as a planet." "There are new worlds to chart even this close to home." "Saturn is a giant gas world." "If it has a solid surface it must lie far below the clouds we see." "Saturn's majestic rings are made of trillions of orbiting snowballs." "We are now only 80 light minutes from home." "A mere 1 1/2 billion kilometers." "The largest planet in our solar system is Jupiter." "On its dark side, super bolts of lightning illuminate the clouds as first revealed by the Voyager spacecraft in 1979." "Inside the orbit of Jupiter are countless shattered and broken world-lets:" "The asteroids." "These reefs and shoals mark the border of the realm of giant planets." "We are now entering the shallows of the solar system." "Here there are worlds with thin atmospheres and solid surfaces:" "Earth-like planets with landscapes crying out for careful exploration." "This world is Mars." "In 1976, after a year's voyage two robot explorers from Earth landed on this alien shore." "On Mars, there is a volcano as wide as Arizona and almost three times the height of Mount Everest." "We've named it Mount Olympus." "This is a world of wonders." "Mars is a planet with ancient river valleys and violent sandstorms driven by winds at half the speed of sound." "There is a giant rift in its surface 5000 kilometers long." "It's called Vallis Marinaris." "The valley of the Mariner spacecraft that came to explore Mars from a nearby world." "In this, our first cosmic voyage we have just begun the reconnaissance of Mars and all those other planets and stars and galaxies." "In voyages to come, we will explore them more fully." "But now, we travel the few remaining light minutes to a blue and cloudy world, third from the sun." "The end of our long journey is the world where we began." "Our travels allow us to see the Earth anew as if we came from somewhere else." "There are a hundred billion galaxies and a billion trillion stars." "Why should this modest planet be the only inhabited world?" "To me, it seems far more likely that the cosmos is brimming over with life and intelligence." "But so far, every living thing every conscious being every civilization we know anything about lived there, on Earth." "Beneath these clouds the drama of the human species has been unfolded." "We have, at last, come home." "Welcome to the planet Earth." "A place with blue nitrogen skies oceans of liquid water cool forests soft meadows." "A world positively rippling with life." "In the cosmic perspective, it is, for the moment, unique." "The only world in which we know with certainty that the matter of the cosmos has become alive and aware." "There must be many such worlds scattered through space but our search for them begins here with the accumulated wisdom of the men and women of our species acquired at great cost over a million years." "There was once a time when our planet seemed immense." "When it was the only world we could explore." "Its true size was first worked out in a simple and ingenious way by a man who lived here in Egypt, in the third century B.C." "This tower may have been a communications tower." "Part of a network running along the North African coast by which signal bonfires were used to communicate messages of state." "It also may have been used as a lighthouse a navigational beacon for sailing ships out there in the Mediterranean Sea." "It is about 50 kilometers west of what was once one of the great cities of the world, Alexandria." "In Alexandria, at that time there lived a man named Eratosthenes." "A competitor called him "beta," the second letter of the Greek alphabet because, he said, "Eratosthenes was second best in everything."" "But it seems clear, in many fields, Eratosthenes was "alpha."" "He was an astronomer, historian, geographer philosopher, poet, theater critic and mathematician." "He was also the chief librarian of the Great Library of Alexandria." "And one day while reading a papyrus book in the library he came upon a curious account." "Far to the south, he read at the frontier outpost of Syene something notable could be seen on the longest day of the year." "On June 21st the shadows of a temple column, or a vertical stick would grow shorter as noon approached." "As the hours crept towards midday the sun's rays would slither down the sides of a deep well which on other days would remain in shadow." "And then, precisely at noon columns would cast no shadows." "And the sun would shine directly down into the water of the well." "At that moment the sun was exactly overhead." "It was an observation that someone else might easily have ignored." "Sticks, shadows, reflections in wells the position of the sun simple, everyday matters." "Of what possible importance might they be?" "But Eratosthenes was a scientist and his contemplation of these homely matters changed the world in a way, made the world." "Because Eratosthenes had the presence of mind to experiment to actually ask whether back here, near Alexandria a stick cast a shadow near noon on June the 21 st." "And it turns out, sticks do." "An overly skeptical person might have said that the report from Syene was an error." "But it's an absolutely straightforward observation." "Why would anyone lie on such a trivial matter?" "Eratosthenes asked himself how it could be that at the same moment a stick in Syene would cast no shadow and a stick in Alexandria, 800 kilometers to the north would cast a very definite shadow." "Here is a map of ancient Egypt." "I've inserted two sticks, or obelisks." "One up here in Alexandria and one down here in Syene." "Now, if at a certain moment each stick casts no shadow, no shadow at all that's perfectly easy to understand, provided the Earth is flat." "If the shadow at Syene is at a certain length and the shadow at Alexandria is the same length that also makes sense on a flat Earth." "But how could it be, Eratosthenes asked that at the same instant there was no shadow at Syene and a very substantial shadow at Alexandria?" "The only answer was that the surface of the Earth is curved." "Not only that but the greater the curvature, the bigger the difference in the lengths of the shadows." "The sun is so far away that its rays are parallel when they reach the Earth." "Sticks at different angles to the sun will cast shadows at different lengths." "For the observed difference in the shadow lengths the distance between Alexandria and Syene had to be about seven degrees along the surface of the Earth." "By that, I mean, if you would imagine these sticks extending all the way down to the center of the Earth they would there intersect at an angle of seven degrees." "Well, seven degrees is something like a 50th of the full circumference of the Earth, 360 degrees." "Eratosthenes knew the distance between Alexandria and Syene." "He knew it was 800 kilometers." "Why?" "Because he hired a man to pace out the entire distance so that he could perform the calculation I'm talking about." "Now, 800 kilometers times 50 is 40,000 kilometers." "That must be the circumference of the Earth." "That's how far it is to go once around the Earth." "That's the right answer." "Eratosthenes' only tools were sticks, eyes, feet and brains." "Plus a zest for experiment." "With those tools, he correctly deduced the circumference of the Earth to high precision with an error of only a few percent." "That's pretty good figuring for 2200 years ago." "Then, as now, the Mediterranean was teeming with ships." "Merchantmen, fishing vessels, naval flotillas." "But there were also courageous voyages into the unknown." "400 years before Eratosthenes, Africa was circumnavigated by a Phoenician fleet in the employ of the Egyptian pharaoh Necho." "They set sail probably in boats as frail and open as these out from the Red Sea, down the east coast of Africa up into the Atlantic and then back through the Mediterranean." "That epic journey took three years about as long as it takes Voyager to journey from Earth to Saturn." "After Eratosthenes, some may have attempted to circumnavigate the Earth." "But until the time of Magellan, no one succeeded." "What tales of adventure and daring must earlier have been told as sailors and navigators, practical men of the world gambled their lives on the mathematics of a scientist from ancient Alexandria." "Today, Alexandria shows few traces of its ancient glory of the days when Eratosthenes walked its broad avenues." "Over the centuries, waves of conquerors converted its palaces and temples into castles and churches, then into minarets and mosques." "The city was chosen to be the capital of his empire by Alexander the Great on a winter's afternoon in 331 B.C." "A century later, it had become the greatest city of the world." "Each successive civilization has left its mark." "But what now remains of the marvel city of Alexander's dream?" "Alexandria is still a thriving marketplace still a crossroads for the peoples of the Near East." "But once, it was radiant with self-confidence certain of its power." "Can you recapture a vanished epoch from a few broken statues and scraps of ancient manuscripts?" "In Alexandria, there was an immense library and an associated research institute." "And in them worked the finest minds in the ancient world." "(CAN CLUNKS)" "(DOOR SQUEAKS)" "Of that legendary library all that survives is this dank and forgotten cellar." "It's in the library annex, the Serapeum which was once a temple but was later reconsecrated to knowledge." "These few moldering shelves probably once in a basement storage room are its only physical remains." "But this place was once the brain and glory of the greatest city on the planet Earth." "If I could travel back into time this is the place I would visit." "The Library of Alexandria at its height, 2000 years ago." "Here, in an important sense began the intellectual adventure which has led us into space." "All the knowledge in the ancient world was once within these marble walls." "In the great hall, there may have been a mural of Alexander with the crook and flail and ceremonial headdress of the pharaohs of ancient Egypt." "This library was a citadel of human consciousness a beacon on our journey to the stars." "It was the first true research institute in the history of the world." "And what did they study?" "They studied everything." "The entire cosmos." ""Cosmos" is a Greek word for the order of the universe." "In a way, it's the opposite of chaos." "It implies a deep interconnectedness of all things." "The intricate and subtle way that the universe is put together." "Genius flourished here." "In addition to Eratosthenes, there was the astronomer Hipparchus who mapped the constellation and established the brightness of the stars." "And there was Euclid who brilliantly systematized geometry who told his king, who was struggling with some difficult problem in mathematics that there was no royal road to geometry." "There was Dionysius of Thrace, the man who defined the parts of speech:" "nouns, verbs and so on who did for language, in a way, what Euclid did for geometry." "There was Herophilus, a physiologist who identified the brain rather than the heart as the seat of intelligence." "There was Archimedes, the greatest mechanical genius until the time of Leonardo da Vinci." "And there was the astronomer Ptolemy, who compiled much of what today is the pseudoscience of astrology." "His Earth-centered universe held sway for 1 500 years showing that intellectual brilliance is no guarantee against being dead wrong." "And among these great men, there was also a great woman." "Her name was Hypatia." "She was a mathematician and an astronomer the last light of the library whose martyrdom is bound up with the destruction of this place seven centuries after it was founded." "Look at this place." "The Greek kings of Egypt who succeeded Alexander regarded advances in science, literature and medicine as among the treasures of the empire." "For centuries, they generously supported research and scholarship." "An enlightenment shared by few heads of state, then or now." "(FOUNTAIN GURGLES)" "Off this great hall were 1 0 large research laboratories." "There were fountains and colonnades, botanical gardens and even a zoo with animals from India and sub-Saharan Africa." "There were dissecting rooms and an astronomical observatory." "But the treasure of the library consecrated to the god Serapis built in the city of Alexander was its collection of books." "The organizers of the library combed all the cultures and languages of the world for books." "They sent agents abroad to buy up libraries." "Commercial ships docking in Alexandria harbor were searched by the police not for contraband, but for books." "The scrolls were borrowed, copied and returned to their owners." "Until studied, these scrolls were collected in great stacks called, "books from the ships."" "Accurate numbers are difficult to come by but it seems that the library contained at its peak nearly one million scrolls." "The papyrus reed grows in Egypt." "It's the origin of our word for "paper."" "Each of those million volumes which once existed in this library were handwritten on papyrus manuscript scrolls." "What happened to all those books?" "The classical civilization that created them disintegrated." "The library itself was destroyed." "Only a small fraction of the works survived." "And as for the rest, we're left only with pathetic scattered fragments." "But how tantalizing those remaining bits and pieces are." "For example, we know that there once existed here a book by the astronomer Aristarchus of Samos who apparently argued that the Earth was one of the planets that, like the other planets, it orbits the sun and that the stars are enormously far away." "All absolutely correct." "But we had to wait nearly 2000 years for these facts to be rediscovered." "The astronomy stacks of the Alexandria Library." "Hipparchus." "Ptolomeus." "Here we are." "Aristarchus." "This is the book." "How I'd love to be able to read this book to know how Aristarchus figured it out." "But it's gone." "Utterly and forever." "If we multiply our sense of loss for this work of Aristarchus by 1 00,000 we begin to appreciate the grandeur of the achievement of classical civilization and the tragedy of its destruction." "We have far surpassed the science known to the ancient world but there are irreparable gaps in our historical knowledge." "Imagine what mysteries of the past could be solved with a borrower's card to this library." "For example, we know of a three-volume history of the world now lost, written by a Babylonian priest named Berossus." "Volume I dealt with the interval from the creation of the world to the Great Flood." "A period that he took to be 432,000 years or about 1 00 times longer than the Old Testament chronology." "What wonders were in the books of Berossus!" "But why have I brought you across 2000 years to the Library of Alexandria?" "Because this was when and where we humans first collected seriously and systematically the knowledge of the world." "This is the Earth as Eratosthenes knew it." "A tiny, spherical world, afloat in an immensity of space and time." "We were, at long last, beginning to find our true bearings in the cosmos." "The scientists of antiquity took the first and most important steps in that direction before their civilization fell apart." "But after the Dark Ages, it was by and large the rediscovery of the works of these scholars done here that made the Renaissance possible and thereby powerfully influenced our own culture." "When, in the 1 5th century, Europe was at last ready to awaken from its long sleep it picked up some of the tools, the books and the concepts laid down here more than a thousand years before." "By 1600, the long-forgotten ideas of Aristarchus had been rediscovered." "Johannes Kepler constructed elaborate models to understand the motion and arrangement of the planets the clockwork of the heavens." "And at night, he dreamt of traveling to the moon." "His principal scientific tools were the mathematics of the Alexandrian Library and an unswerving respect for the facts however disquieting they might be." "His story, and the story of the scientists who came after him are also part of our voyage." "Seventy years later, the sun-centered universe of Aristarchus and Copernicus was widely accepted in the Europe of the Enlightenment." "The idea arose that the planets were worlds governed by laws of nature and scientific speculation turned to the motions of the stars." "The clockwork in the heavens was imitated by the watchmakers of Earth." "Precise timekeeping permitted great sailing ship voyages of exploration and discovery which bound up the Earth." "This was a time when free inquiry was valued once again." "(SPEAKING IN FOREIGN LANGUAGE)" "250 years later, the Earth was all explored." "New adventurers now looked to the planets and the stars." "The galaxies were recognized as great aggregates of stars island universes millions of light years away." "In the 1920s, astronomers had begun to measure the speeds of distant galaxies." "ASTRONOMER 1:" "What time is it?" "7:1 5." "ASTRONOMER 1:" "Lights off, please." "They found that the galaxies were flying away from one another." "To the astonishment of everyone the entire universe was expanding." "We had begun to plumb the true depths of time and space." "The long, collective enterprise of science has revealed a universe some 1 5 billion years old." "The time since the explosive birth of the cosmos the big bang." "The current estimates for the age of the universe range from 1 2 to 1 5 billion years." "(THUNDER CRASHES)" "The cosmic calendar compresses the local history of the universe into a single year." "If the universe began on January 1st it was not until May that the Milky Way formed." "Other planetary systems may have appeared in June, July and August but our sun and Earth, not until mid-September." "Life arose soon after." "Everything humans have ever done occurred in that bright speck at the lower right of the cosmic calendar." "The big bang is at upper left in the first second of January 1st." "Fifteen billion years later is our present time the last second of December 31st." "Every month is 1¼ billion years long." "Each day represents 40 million years." "Each second stands for some 500 years of our history." "The blinking of an eye in the drama of cosmic time." "At this scale, the cosmic calendar is the size of a football field but all of human history would occupy an area the size of my hand." "We're just beginning to trace the long and tortuous path which began with the primeval fireball and led to the condensation of matter:" "Gas, dust, stars, galaxies, and at least in our little nook of the universe planets, life, intelligence and inquisitive men and women." "We've emerged so recently that the familiar events of our recorded history occupy only the last seconds of the last minute of December 31st." "But some critical events for the human species began much earlier minutes earlier." "So we change our scale from months to minutes." "Down here, the first humans made their debut around 10:30 p.m. on December 31st." "And with the passing of every cosmic minute each minute 30,000 years long we began the arduous journey towards understanding where we live and who we are." "11:46 only 14 minutes ago humans have tamed fire." "11:59:20, the evening of the last day of the cosmic year the 11th hour, the 59th minute, the 20th second the domestication of plants and animals begins:" "An application of the human talent for making tools." "11:59:35, settled agricultural communities evolved into the first cities." "We humans appear on the comic calendar so recently that our recorded history occupies only the last few seconds of the last minute of December 31 st." "In the vast ocean of time which this calendar represents all our memories are confined to this small square." "Every person we've ever heard of lived somewhere in there." "All those kings and battles, migrations and inventions, wars and loves." "Everything in the history books happens here in the last 10 seconds of the cosmic calendar." "We on Earth have just awakened to the great oceans of space and time from which we have emerged." "We are the legacy of 15 billion years of cosmic evolution." "We have a choice:" "We can enhance life and come to know the universe that made us or we can squander our 15 billion-year heritage in meaningless self-destruction." "What happens in the first second of the next cosmic year depends on what we do, here and now with our intelligence and our knowledge of the cosmos." "SAGAN:" "All my life I've wondered about life beyond the Earth." "On those countless other planets that we think circle other suns is there also life?" "Might the beings of other worlds resemble us or would they be astonishingly different?" "What would they be made of?" "In the vast Milky Way galaxy how common is what we call life?" "The nature of life on Earth and the quest for life elsewhere are the two sides of the same question." "The search for who we are." "All living things on Earth are made of organic molecules a complex microscopic architecture built around atoms of carbon." "In the great dark between the stars there also are organic molecules in immense clouds of gas and dust." "Inside such clouds there are batches of new worlds just forming." "Their surfaces are very likely covered with organic molecules." "These molecules almost certainly are not made by life although they are the stuff of life." "On suitable worlds, they may lead to life." "Organic matter is abundant throughout the cosmos produced by the same chemistry everywhere." "Perhaps, given enough time the origin and evolution of life is inevitable on every clement world." "There will surely be some planets too hostile for life." "On others, it may arise and die out or never evolve beyond its simplest forms." "And on some small fraction of worlds there may develop intelligences and civilizations more advanced than ours." "All life on our planet is closely related." "We have a common organic chemistry and a common evolutionary heritage." "And so our biologists are profoundly limited." "They study a single biology one lonely theme in the music of life." "Is it the only voice for thousands of light years or is there a cosmic fugue, a billion different voices playing the life music of the galaxy?" "This blue world is where we grew up." "There was once a time before life." "Our planet is now burgeoning with life." "How did it come about?" "How were organic molecules originally made?" "How did life evolve to produce beings as elaborate and complex as we able to explore the mystery of our own origins?" "Let me tell you a story about one little phrase in the music of life on Earth." "(WIND BLOWS)" "In the history of humans in the 12th century Japan was ruled by a clan of warriors called the Heike." "The nominal leader of the Heike, the emperor of Japan was a 7-year-old boy named Antoku." "His guardian was his grandmother, the Lady Nii." "(DRUM BEATS)" "The Heike were engaged in a long and bloody war with another Samurai clan, the Genji." "Each asserted a superior ancestral claim to the imperial throne." "(BATTLE CRIES)" "Their decisive encounter occurred at Dannoura in the Japanese Inland Sea on April 24 in the year 1 185." "The Heike were badly outnumbered and outmaneuvered." "With their cause clearly lost the surviving Heike warriors threw themselves into the sea and drowned." "The emperor's grandmother, the Lady Nii resolved that they would not be captured by the enemy." "What happened next is related in "The Tale of the Heike":" ""The young emperor asked the Lady Nii, 'Where are you to take me?" "'" "She turned to the youthful sovereign with tears streaming down her cheeks and comforted him." "(WATER LAPS)" "Blinded with tears the child sovereign put his beautiful small hands together." "He turned first to the east to say farewell to the god of Ise and then to the west to recite a prayer to the Amida Buddha." "The Lady Nii took him in her arms, and with the words:" "'In the depths of the ocean is our capital' sank with him at last beneath the waves."" "The destruction of the Heike battle fleet at Dannoura marked the end of the clan's 30-year rule." "The Heike all but vanished from history." "Only 43 Heike survived, all women." "These former ladies-in-waiting of the Imperial Court were reduced to selling flowers and other favors to the fishermen near the scene of the battle." "These women and their offspring by the fishermen established a festival to commemorate the battle." "To this day, every year, on the 24th of April their descendants proceed to the Akama shrine which contains the mausoleum of the drowned 7-year-old emperor, Antoku." "There, they conduct a ceremony of remembrance for the life and death of the Heike warriors." "But there is a strange postscript to this story:" "The fishermen say that the Heike samurai wander the bottom of the Inland Sea in the form of crabs." "There are crabs here which have curious markings on their backs." "Patterns which resemble a human face with the aggressive scowl of a samurai warrior from medieval Japan." "(DRUM BEATS)" "These Heike crabs, when caught, are not eaten." "They are thrown back into the sea in commemoration of the doleful events of the battle of Dannoura." "This legend raises a lovely problem:" "How does it come about that the face of a warrior is cut on the carapace of a Japanese crab?" "How could it be?" "The answer seems to be that humans made this face." "But how?" "Like many other features, the patterns on the back or carapace of this crab are inherited." "But among crabs, as among humans, there are different hereditary lines." "Now, suppose purely by chance among the distant ancestors of this crab there came to be one which looked just a little bit like a human face." "Long before the battle, fishermen may have been reluctant to eat a crab with a human face." "In throwing it back into the sea they were setting into motion a process of selection." "If you're a crab and your carapace is just ordinary the humans are gonna eat you." "But if it looks a little bit like a face they'll throw you back and you can have lots of baby crabs that all look just like you." "As many generations passed of crabs and fisher-folk alike the crabs with patterns that looked most like a samurai face preferentially survived." "Until eventually, there was produced not just a human face not just a Japanese face but the face of a samurai warrior." "All this has nothing to do with what the crabs might want." "Selection is imposed from the outside." "The more you look like a samurai, the better your chances of survival." "Eventually, there are a lot of crabs that look like samurai warriors." "(DRUM BEATS)" "This process is called artificial selection." "In the case of the Heike crab, it was effected more or less unconsciously by the fishermen and certainly without any serious contemplation by the crabs." "Humans, for thousands of years have deliberately selected which plants and animals shall live." "We're surrounded by farm and domestic animals fruits, vegetables." "Where do they come from?" "Were they once free-living in the wild and then induced to adopt some less strenuous life on the farm?" "No." "They are, almost all of them, made by us." "The essence of artificial selection for a horse or a cow a grain of rice or a Heike crab, is this:" "Many characteristics are inherited." "They breed true." "Humans encourage the reproduction of some varieties and discourage the reproduction of others." "The variety selected for, eventually becomes abundant." "The variety selected against, becomes rare, maybe extinct." "But if artificial selection makes such changes in only a few thousand years what must natural selection working for billions of years, be capable of?" "The answer is all the beauty and diversity in the biological world." "That life evolved over the ages is clear from the changes we've made in the beasts and vegetables but also from the record in the rocks." "The fossil evidence speaks to us unambiguously of creatures that were once present in enormous numbers and that have now vanished utterly." "There are more species that have become extinct than exist today." "They are the terminated experiments in evolution." "These guys, the trilobites, appeared 600 million years ago." "They were around for 300 million years." "They're all gone." "There's none left." "But in those old rocks, there are no fossils of people or cattle." "We've evolved only recently." "Evolution is a fact, not a theory." "It really happened." "(BEE BUZZES)" "That the mechanism of evolution is natural selection was the discovery of Charles Darwin and Alfred Russel Wallace." "Here's how it works:" "Nature is prolific." "There are many more creatures that are born than can possibly survive." "So those varieties which are, by accident, less well adapted don't survive, or at least they leave fewer offspring." "Now, mutations, sudden changes in heredity are passed on." "They breed true." "The environment selects the occasional mutations which enhance survival." "The resulting series of slow changes in the nature of living beings is the origin of new species." "Many people were scandalized by the ideas of evolution and natural selection." "Our ancestors looked at the intricacy and the beauty of life and saw evidence for a great designer." "The simplest organism is a far more complex machine than the finest pocket watch." "And yet, pocket watches don't spontaneously self-assemble or evolve in slow stages on their own from say, grandfather clocks." "A watch implies a watchmaker." "There seemed to be no way atoms could spontaneously fall together and create, say a dandelion." "The idea of a designer is an appealing and altogether human explanation of the biological world." "But as Darwin and Wallace showed there's another way equally human and far more compelling." "Natural selection, which makes the music of life more beautiful as the eons pass." "(LOUD RUMBLE)" "To understand the passage of the eons we have compressed all of time into a single cosmic year with the big bang on January first." "Every month here represents a little over a billion years." "The Earth didn't form until the cosmic year was two-thirds over." "Our understanding of the history of life is very recent occupying only the last few seconds of December 31 that small white spot at bottom right in the cosmic calendar." "What happened on Earth may be more or less typical of the evolution of life on many worlds." "But in its details the story of life on Earth is probably unique in all the Milky Way galaxy." "The secrets of evolution are time and death." "Time for the slow accumulation of favorable mutations and death to make room for new species." "Life on Earth arose in September of the cosmic calendar when our world, still battered and cratered from its violent origin may have looked a little like the moon." "The Earth is about four and a half billion years old." "In the cosmic calendar it condensed out of interstellar gas and dust around September 1 4." "We know from the fossil record that life originated soon after maybe around September 25, something like that probably in the ponds and oceans of the primitive Earth." "The first living things were not as complex as a one-celled organism which is already a highly sophisticated form of life." "No, the first stirrings of life were much more humble and happened on the molecular level." "In those early days, lightning and ultraviolet light from the sun were breaking apart hydrogen-rich molecules in the atmosphere." "The fragments of the molecules were spontaneously recombining into more and more complex molecules." "The products of this early chemistry dissolved in the oceans forming a kind of organic soup of gradually increasing complexity." "Until one day, quite by accident a molecule arose that was able to make crude copies of itself using as building blocks the other molecules in the soup." "This was the ancestor of DNA the master molecule of life on Earth." "It's made of four different parts, called nucleotides which constitute the four letters of the genetic code the language of heredity." "Each of the nucleotides, the rungs on the DNA ladder are a different color in this model." "The instructions are different for different organisms." "That's why organisms are different." "Now, a mutation is a change of a nucleotide a misspelling of the genetic instructions." "Most mutations spell genetic nonsense since they're random." "They harm the next generation." "But a very few, by accident make better sense than the original codes, and aid evolution." "DNA is about a billion times smaller than we see it here." "Each of those things that looks like a piece of fruit is an atom." "Without the tools of science the machinery of life would be invisible." "Four billion years ago the ancestors of DNA competed for molecular building blocks and left crude copies of themselves." "There were no predators;" "the stuff of life was everywhere." "The oceans and murky pools that filled the craters were, for these molecules, a Garden of Eden." "With reproduction, mutation and natural selection the evolution of living molecules was well underway." "Varieties with specialized functions joined together making a collective." "The first cell." "The organic soup eventually ate itself up." "But by this time, plants had evolved, able to use sunlight to make their own building blocks." "They turned the waters green." "One-celled plants joined together:" "The first multi-cellular organisms." "Equally important was the invention, not made until early November of sex." "It was stumbled upon by the microbes." "By December 1, green plants had released copious amounts of oxygen and nitrogen into the atmosphere." "The sky is made by life." "Then, suddenly, on December 1 5 there was an enormous proliferation of new life forms an event called the "Cambrian Explosion."" "We know from fossils that life arose shortly after the Earth formed suggesting that the origin of life might be an inevitable chemical process on countless Earth-like planets throughout the cosmos." "But on the Earth, in nearly 4 billion years, life advanced no further than algae." "So maybe more complex forms of life are harder to evolve harder even than the origin of life itself." "If this is right, the planets of the galaxy might be filled with microorganisms but big beasts and vegetables and thinking beings might be comparatively rare." "By December 18, there were vast herds of trilobites foraging on the ocean bottom and squid-like creatures with multicolored shells were everywhere." "We know enough to sketch in a few of the subsequent details." "The first fish and the first vertebrates appeared on December 19." "Plants began to colonize the land on December 20." "The first winged insects fluttered by on December 22." "On this date also, there were the first amphibians creatures something like the lungfish able to survive both on land and in water." "Our direct ancestors were now leaving the oceans behind." "The first trees and the first reptiles evolved on December 23:" "Two amazing evolutionary developments." "We are descended from some of those reptiles." "The dinosaurs appeared on Christmas Eve." "There were many different kinds of dinosaurs." "The Earth was once their planet." "Many stood upright and had some fair intelligence." "Great lizards crashed and thundered through the steaming jungles." "Unnoticed by the dinosaurs, a new creature whose young were born live and helpless was making its timid debut." "The first mammals emerged on December 26 the first birds on the following day." "But the dinosaurs still dominated the planet." "Then suddenly, without warning, all over the planet at once the dinosaurs died." "The cause is unknown, but the lesson is clear:" "Even 160 million years on a planet is no guarantee of survival." "The dinosaurs perished around the time of the first flower." "On December 30, the first creatures who looked even a little bit human, evolved accompanied by a spectacular increase in the size of their brains." "And then, on the evening of the last day of the last month only a few million years ago the first true humans took their place on the cosmic calendar." "The written record of history occupies only the last 10 seconds of the cosmic year." "Now, let's take a closer look at who our ancestors were." "A simple chemical circumstance led to a great moment in the history of our planet." "There were many molecules in the primordial soup." "Some were attracted to water on one side and repelled by it on the other." "This drove them together into a tiny enclosed spherical shell like a soap bubble, which protected the interior." "Within the bubble, the ancestors of DNA found a home and the first cell arose." "It took hundreds of millions of years for tiny plants to evolve giving off oxygen." "But that branch didn't lead to us." "Bacteria that could breathe oxygen took over a billion years to evolve." "From a naked nucleus, a cell developed with a nucleus inside." "Some of these amoeba-like forms led eventually to plants." "Others produced colonies with inside and outside cells performing different functions." "Becoming a polyp attached to the ocean floor filtering food from the water and evolving little tentacles to direct food into a primitive mouth." "This humble ancestor of ours also led to spiny-skinned armored animals with internal organs including our cousin, the starfish." "But we don't come from starfish." "About 550 million years ago filter feeders evolved gill slits which were more efficient at straining food particles." "One evolutionary branch led to acorn worms." "Another led to a creature which swam freely in the larval stage but, as an adult, was still firmly anchored to the ocean floor." "Some became living hollow tubes." "But others retained the larval forms throughout the life cycle and became free-swimming adults with something like a backbone." "Our ancestors now 500 million years ago, were jawless filter-feeding fish a little like lampreys." "Gradually, those tiny fish evolved eyes and jaws." "Fish then began to eat one another if you could swim fast, you survived." "If you had jaws to eat with, you could use your gills to breathe in the water." "This is the way modern fish arose." "During the summer, swamps and lakes dried up." "Some fish evolved a primitive lung to breathe air until the rains came." "Their brains were getting bigger." "If the rains didn't come, it was handy to be able to pull yourself to the next swamp." "That was a very important adaptation." "The first amphibians evolved, still with a fish-like tail." "Amphibians, like fish, laid their eggs in water where they were easily eaten." "But then a splendid new invention came along:" "The hard-shelled egg, laid on land where there were as yet no predators." "Reptiles and turtles go back to those days." "Many of the reptiles hatched on land never returned to the waters." "Some became the dinosaurs." "One line of dinosaurs developed feathers, useful for short flights." "Today, the only living descendants of the dinosaurs are the birds." "The great dinosaurs evolved along another branch." "Some were the largest flesh-eaters ever to walk the land." "But 65 million years ago they all mysteriously perished." "Meanwhile, the forerunners of the dinosaurs were also evolving in a different direction." "Small, scurrying creatures with the young growing inside the mother's body." "After the extinction of the dinosaurs, many different forms developed." "The young were very immature at birth." "In the marsupials, the wombat, for example and in the mammals, the young had to be taught how to survive." "The brain grew larger still." "Something like a shrew was the ancestor of all the mammals." "One line took to the trees, developing dexterity stereo vision, larger brains and a curiosity about their environment." "Some became baboons, but that's not the line to us." "Apes and humans have a recent common ancestor." "Bone for bone, muscle for muscle, molecule for molecule." "There are almost no important differences between apes and humans." "Unlike the chimpanzee, our ancestors walked upright freeing their hands to poke and fix and experiment." "We got smarter." "We began to talk." "Many collateral branches of the human family became extinct in the last few million years." "We, with our brains and our hands, are the survivors." "There's an unbroken thread that stretches from those first cells to us." "Let's look at it again..." "Those are some of the things that molecules do given 4 billion years of evolution." "We sometimes represent evolution as the ever-branching ramifications of some original trunk each branch pruned and clipped by natural selection." "Every plant and animal alive today has a history as ancient and illustrious as ours." "Humans stand on one branch." "But now we affect the future of every branch of this 4-billion-year-old tree." "How lovely trees are." "The human species grew up in and around them." "We have a natural affinity for trees." "Trees photosynthesize they harvest sunlight they compete for the sun's favors." "Look at those two trees there pushing and shoving for sunlight but with grace and astonishing slowness." "There are so many plants on the Earth that there's a danger of thinking them trivial of losing sight of the subtlety and efficiency of their design." "They are great and beautiful machines, powered by sunlight taking in water from the ground and carbon dioxide from the air and converting them into food for their use and ours." "This is a museum of living plants." "The Royal Botanic Gardens at Kew in London." "Every plant uses the carbohydrates it makes as an energy source to go about its planty business." "And we animals, who are ultimately parasites on the plants we steal the carbohydrates so we can go about our business." "In eating the plants and their fruits we combine the carbohydrates with oxygen which as a result of breathing, we've dissolved in our blood." "From this chemical reaction, we extract the energy which makes us go." "In the process, we exhale carbon dioxide which the plants then use to make more carbohydrates." "What a marvelous cooperative arrangement." "Plants and animals each using the other's waste gases the whole cycle powered by abundant sunlight." "But there would be carbon dioxide in the air even if there were no animals." "We need the plants much more than they need us." "There are family resemblances among the organisms of the Earth." "Some are very apparent, such as the use of the number five." "Humans have five major bodily projections:" "One head, two arms, two legs." "So do ducks although the functions of their projections are not quite the same." "An octopus or a centipede has a different plan." "And a being from another planet might be much stranger still." "These family resemblances continue and on a much deeper level when we go to the molecular basis of life." "There are tens of billions of different kinds of organic molecules." "Yet only about 50 of them are used in the essential machinery of life." "The same 50 employed over and over again ingenious, for different functions in every living thing." "And when we go to the very kernel of life on Earth to the proteins that control cell chemistry to the spiral or helix of nucleic acids which carry the hereditary information we find these molecules to be identical in all plants and animals of our planet." "This oak tree and me, we're made of the same stuff." "If you go back, you'll find that we have a common ancestor." "That's why our chemistry is so alike." "Let's take a trip to examine this common basis of life." "A voyage to investigate the molecular machinery at the heart of life on Earth." "A journey to the nucleus of the cell." "First we need a cell." "I have trillions." "I can afford to donate a few." "The casual act of pricking a finger is an event of some magnitude on the scale of the very small." "Millions of red blood cells are detoured from their usual routes." "But most continue to cruise about the body carrying their cargoes of oxygen to the remotest freckle." "We're about to enter the living cell a realm, in its own way, as complex and beautiful as the realm of galaxies and stars." "Among the red blood cells, we encounter a white blood cell a lymphocyte whose job it is to protect me against invading microbes." "It makes antibodies on its furrowed surface but its interior is like that of many cells." "Plunging through the membrane, we find ourselves inside the cell." "Here, every structure has its function." "These dark green blobs are factories where messenger molecules are busy building the enzymes which control the chemistry of the cell." "The messengers were instructed and dispatched from within the nucleus, the heart and brain of the cell." "All the instructions on how to get a cell to work and how to make another are hidden away in there." "We find a tunnel, a nuclear pore an approach to the biological holy of holies." "These necklaces, these intricately looped and coiled strands are nucleic acids, DNA." "Everything you need to know on how to make a human being is encoded in the language of life in the DNA molecule." "This is the DNA double helix a machine with about 100 billion moving parts, called atoms." "There are as many atoms in one molecule of DNA as there are stars in a typical galaxy." "The sequence of nucleotides, here brightly colored is all that's passed on from generation to generation." "Change the order of the nucleotides and you change the genetic instructions." "DNA must replicate itself with extreme fidelity." "The reproduction of a DNA molecule begins by separating the two helices." "This is accomplished by an unwinding enzyme." "Like some precision tool, this enzyme, shown in blue breaks the chemical bonds that bind the two helices of DNA." "The enzyme works its way down the molecule unzipping DNA as it goes." "Each helix copies the other supervised by special enzymes." "The organic soup inside the nucleus contains many free nucleotides." "The enzyme recognizes an approaching nucleotide and clicks it into place reproducing another rung in the double helix." "When the DNA is replicating in one of your cells a few dozen nucleotides are added every second." "Thousands of these enzymes may be working on a given DNA molecule." "When an arriving nucleotide doesn't fit the enzyme throws it away." "We call this proofreading." "On the rare occasions of a proofreading error the wrong nucleotide is attached and a small random change has been made in the genetic instructions." "A mutation has occurred." "This enzyme is a pretty small molecule but it catches nucleotides, assembles them in the right order it knows how to proofread it's responsible in the most fundamental way for the reproduction of every cell and every being on Earth." "That enzyme and DNA itself are molecular machines with awesome powers." "Within every living thing, the molecular machines are busy making sure that nucleic acids will continue to reproduce." "A minor cut in my skin sounds a local alarm and the blood spins a complex net of strong fibers to form a clot and staunch the flow of blood." "There's a very delicate balance here:" "Too much clotting and your blood stream will solidify." "Too little clotting and you'll bleed to death from the merest scratch." "The balance is controlled by enzymes instructed by DNA." "Down here, there's also a kind of sanitation squad surrounds invading bacteria and ravenously consumes them." "This mopping-up operation is a part of the healing process again controlled by DNA." "These cells are parts of us, but how alien they seem." "Within each of them, within every cell there are exquisitely evolved molecular machines." "Nucleic acids, enzymes, the cell architecture every cell is a triumph of natural selection." "And we're made of trillions of cells." "We are, each of us, a multitude." "Within us is a little universe." "Human DNA is a coiled ladder a billion nucleotides long." "Many possible combinations of nucleotides are nonsense." "That is they translate into proteins which serve no useful function whatever." "Only a comparatively few nucleic acid molecules are any good for life forms as complicated as we are." "But even so, the number of useful ways of assembling nucleic acids is stupefyingly large." "It's probably larger than the total number of atoms in the universe." "This means that the number of possible kinds of human beings is vastly greater than the number of human beings that has ever lived." "This untapped potential of the human species is immense." "There are ways of putting nucleic acids together which will function far better by any criterion you wish to choose than the hereditary instructions of any human being who has ever lived." "Fortunately, we do not know, or at least do not yet know how to assemble alternative sequences of nucleotides to make alternative kinds of human beings." "In the future, we might be able to put nucleotides together in any desired sequence to produce human characteristics we think desirable." "A disquieting and awesome prospect." "We human beings don't look very much like a tree." "We certainly view the world differently than a tree does." "But down deep, at the molecular heart of life we're essentially identical to trees." "We both use nucleic acids as the hereditary material." "We both use proteins as enzymes to control the chemistry of the cell." "And most significantly, we both use the identical code book to translate nucleic acid information into protein information." "Any tree could read my genetic code." "How did such astonishing similarities come about?" "Why are we cousins to the trees?" "Would life on some other planet use proteins?" "The same proteins?" "The same nucleic acids?" "The same genetic code?" "The usual explanation is that we are all of us, trees and people anglerfish, slime molds, bacteria all descended from a single and common instance of the origin of life 4 billion years ago in the early days of our planet." "Now, how did the molecules of life arise?" "(THUNDER)" "(LIGHTNING BUZZES)" "In a laboratory at Cornell University we mix together the gases and waters of the primitive Earth supply some energy and see if we can make the stuff of life." "But what was the early atmosphere made of, ordinary air?" "If we start with our present atmosphere the experiment is a dismal failure." "Instead of making proteins and nucleic acids all we make is smog, a backwards step." "Why doesn't such an experiment work?" "Because the air of today contains molecular oxygen." "But oxygen is made by plants." "It's obvious that there were no plants before the origin of life." "We mustn't use oxygen in our experiments because there wasn't any in the early atmosphere." "This is reasonable because the cosmos is made mostly of hydrogen which gobbles oxygen up." "The Earth's low gravity has allowed most of our hydrogen gas to trickle away to space." "There's almost none left." "But 4 billion years ago our atmosphere was full of hydrogen-rich gases:" "Methane, ammonia, water vapor." "These are the gases we should use." "Taking great care to ensure the purity of these gases my colleague, Bishun Khare, pumps them from their holding flasks." "An experiment like this was first performed by Stanley Miller and Harold Urey in the 1950s." "(GASES FIZZLE)" "The starting gases are now introduced into a large reaction vessel." "We could shine ultraviolet light, simulating the early sun." "But in this experiment the gases will be sparked as the primitive atmosphere was by early lightning." "(LIGHTNING BUZZES)" "After only a few hours, the interior of the reaction vessel becomes streaked with a strange brown pigment a rich collection of complex organic molecules including the building blocks of the proteins and the nucleic acids." "Under the right conditions, these building blocks assemble themselves into molecules resembling little proteins and little nucleic acids." "These nucleic acids can even make identical copies of themselves." "In this vessel are the notes of the music of life although not yet the music itself." "Now, no one, so far has mixed together the gases and waters of the primitive Earth and at the end of the experiment had something crawl out of the flask." "There's still much to be understood about the origin of life including the origin of the genetic code." "But we've only been at such experiments for 30 years." "Nature's had a 4-billion-year head start." "Incidentally, there's nothing in such experiments that's unique to the Earth." "The gases we start with, the energy sources we use are entirely common through the cosmos." "So chemical reactions something like these must be responsible for the organic matter in interstellar space and the amino acids in the meteorites." "Similar chemical reactions must have occurred on a billion other worlds in the Milky Way galaxy." "Look how easy it is to make great globs of this stuff." "The molecules of life fill the cosmos." "Now..." "What would life elsewhere look like?" "Even if it had an identical molecular chemistry to life on Earth which I very much doubt it could not be very similar in form to familiar organisms on the Earth." "The random character of the evolutionary process must create elsewhere creatures very different from any that we know." "Think of a world something like Jupiter with an atmosphere rich in hydrogen, helium, methane, water and ammonia in which organic molecules might be falling from the skies like manna from heaven like the products of the Miller-Urey experiment." "Could there be life on such a world?" "There's a special problem." "The atmosphere is turbulent and down deep, before we ever come to a surface, it's very hot." "If you're not careful, you'll be carried down and fried." "If you reproduce before you're fried turbulence will carry your offspring into the higher and cooler layers." "Such organisms could be very little." "We call them sinkers." "The physicist E.E. Salpeter and I at Cornell have calculated something about the life that might exist on such a world." "Vast living balloons could stay buoyant by pumping heavy gases from their interiors or by keeping their insides warm." "They might eat the organic molecules in the air or make their own with sunlight." "We call these creatures floaters." "We imagine floaters kilometers across enormously larger than the greatest whale that ever was beings the size of cities." "We conceive of them arrayed in great, lazy herds as far as the eye can see concentrated in the updrafts in the enormous sea of clouds." "But there can be other creatures in this alien environment: hunters." "Hunters are fast and maneuverable." "They eat the floaters, both for their organic molecules and for their store of pure hydrogen." "But there can't be many hunters because if they destroy all the floaters, they themselves will perish." "Physics and chemistry permit such life forms." "Art presents them with a certain reality but nature is not obliged to follow our speculations." "If there are billions of inhabited worlds in the Milky Way galaxy then I think it's likely there are a few places which might have hunters and floaters and sinkers." "Biology is more like history than it is like physics." "You have to know the past to understand the present." "There is no predictive theory of biology, nor is there for history." "The reason is the same:" "Both subjects are still too complicated for us." "But we can understand ourselves much better by understanding other cases." "The study of a single instance of extraterrestrial life..." "No matter how humble, a microbe would be just fine." "...will de-provincialize biology." "It will show us what else is possible." "We've heard so far the voice of life on only a single world but for the first time, as we shall see we've begun a serious scientific search for the cosmic fugue." "Recently, we've learned more about the origin of life." "Do you remember RNA that nucleic acid that our cells use as messengers carrying the genetic information out of the cell nucleus?" "Well, it's been found that RNA, like protein can control chemical reactions as well as reproduce itself, which proteins can't do." "Many scientists now wonder if the first life on Earth was an RNA molecule." "It now seems feasible that key molecular building blocks for the origin of life, fell out of the skies 4 billion years ago." "Comets have been found to have a lot of organic molecules in them and they fell in huge numbers on the primitive Earth." "We also mention the extinction of the dinosaurs and most of the other species on Earth about 65 million years ago." "We now know that a large comet hit the Earth at just that time." "The dust pall from that collision must've cooled and darkened the Earth perhaps killing all the dinosaurs, but sparing the small, furry mammals who were our ancestors." "Other cometary mass extinctions in other epochs seem likely." "If true, this would mean that comets have been the bringers both of life and death." "SAGAN:" "There are two ways to view the stars:" "As they really are and as we might wish them to be." "There are the Pleiades a group of young stars astronomers recognize as leaving their stellar nurseries of gas and dust." "And this is the Crab Nebula a stellar graveyard, where gas and dust are being dispersed back into the interstellar medium." "Inside it is a dying pulsar." "Both the Pleiades and the Crab Nebula are in a constellation astrologers long ago named Taurus the Bull." "They imagined it to influence our daily lives." "Astronomers say that the planet Saturn is an immense globe of hydrogen and helium encircled by a ring of snowballs 50,000 kilometers wide and that Jupiter's great red spot is a giant storm raging for perhaps a million years." "But the astrologers see the planets as affecting human character and fate." "Jupiter represents a regal bearing and a gentle disposition." "And Saturn, the gravedigger fosters, they say, mistrust, suspicion, and evil." "To the astronomers, Mars is a place as real as the Earth a world awaiting exploration." "But the astrologers see Mars as a warrior the instigator of quarrels, violence and destruction." "Astronomy and astrology were not always so distinct." "For most of human history, the one encompassed the other." "But there came a time when astronomy escaped from the confines of astrology." "The two traditions began to diverge in the life and mind of Johannes Kepler." "It was he who demystified the heavens by discovering that a physical force lay behind the motions of the planets." "He was the first astrophysicist and the last scientific astrologer." "The intellectual foundations of astrology were swept away 300 years ago and yet, astrology is still taken seriously by a great many people." "Have you ever noticed how easy it is to find a magazine on astrology?" "Virtually every newspaper in America has a daily column on astrology." "Almost none of them have even a weekly column on astronomy." "People wear astrological pendants check their horoscopes in the morning even our language preserves an astrological aspect." "For example, take the word "disaster"." "It comes from the Greek for "bad star"." "Italians once believed disease was caused by the influence of the stars." "It's the origin of our word "influenza."" "The zodiacal signs used by astrologers even ornament this statue of Prometheus in New York City." "Prometheus, who stole fire from the gods." "What is all this astrology business?" "Fundamentally, it's the contention that the constellations of the planets at the moment of your birth profoundly influences your future." "A few thousand years ago the idea developed that the motions of the planets determined the fates of kings dynasties, empires." "Astrologers studied the motions of the planets and asked what had happened last time that, say Venus was rising in the constellation of the Goat?" "Maybe something similar would happen this time." "It was a subtle and risky business." "Astrologers became employed only by the state." "In many countries it became a capital offense for anyone but official astrologers to read the portents in the skies." "Why?" "Because a good way to overthrow a regime was to predict its downfall." "Chinese court astrologers who made inaccurate predictions were executed." "Others simply doctored the records so that afterwards they were in perfect conformity with events." "Astrology developed into a strange discipline:" "A mixture of careful observations, mathematics and record-keeping with fuzzy thinking and pious fraud." "Nevertheless, astrology survived and flourished." "Why?" "Because it seems to lend a cosmic significance to our daily lives." "It pretends to satisfy our longing to feel personally connected with the universe." "Astrology suggests a dangerous fatalism." "If our lives are controlled by a set of traffic signals in the sky why try to change anything?" "Here, look at this." "Two different newspapers, published in the same city on the same day." "Let's see what they do about astrology." "Suppose you were a Libra that is born between September 23 and October 22." "According to the astrologer for the New York Post:" ""Compromise will help ease tension."" "Well. maybe." "It's sort of vague." "According to the New York Daily News' astrologer:" ""Demand more of yourself." Well, also vague." "But also pretty different." "It's interesting that these predictions are not predictions." "They tell you what to do, they don't say what will happen." "They're consciously designed to be so vague that it could apply to anybody and they disagree with each other." "Astrology can be tested by the lives of twins." "There are many real cases like this:" "One twin is killed in childhood in, say, a riding accident, or is struck by lightning but the other lives to a prosperous old age." "Suppose that happened to me." "My twin and I would be born in precisely the same place and within minutes of each other." "Exactly the same planets would be rising at our births." "If astrology were valid how could we have such profoundly different fates?" "It turns out that astrologers can't even agree among themselves what a given horoscope means." "In careful tests they're unable to predict the character and future of people they know nothing about except the time and place of birth." "Also, how could it possibly work?" "How could the rising of Mars at the moment of my birth affect me then or now?" "I was born in a closed room." "Light from Mars couldn't get in." "The only influence of Mars which could affect me was its gravity." "But the gravitational influence of the obstetrician was much larger than the gravitational influence of Mars." "Mars is a lot more massive but the obstetrician was a lot closer." "The desire to be connected with the cosmos reflects a profound reality for we are connected." "Not in the trivial ways that the pseudo-science of astrology promises but in the deepest ways." "Our little planet is under the influence of a star." "The sun warms us." "It drives the weather." "(We now know that not all life depends on sunlight.)" "It sustains all living things." "(Life may even have begun in the sunless depths.)" "Four billion years ago, it brought forth life on Earth." "But our sun is only one of a billion trillion stars within the observable universe." "And those countless suns all obey natural laws some of which are already known to us." "How did we discover that there are such laws?" "If we lived on a planet where nothing ever changed there wouldn't be much to do." "There'd be nothing to figure out." "There'd be no impetus for science." "And if we lived in an unpredictable world where things changed in random or complex ways we wouldn't be able to figure things out." "And again, there'd be no such thing as science." "But we live in an in-between universe where things change, all right but according to patterns, rules or as we call them, laws of nature." "If I throw a stick up in the air it always falls down." "If the sun sets in the west it always rises again the next morning in the east." "And so, it's possible to figure things out." "We can do science, and with it we can improve our lives." "Human beings are good at understanding the world." "We always have been." "We were able to hunt game or build fires only because we had figured something out." "There once was a time before television before motion pictures, before radio, before books." "The greatest part of human existence was spent in such a time." "And then over the dying embers of the campfire on a moonless night we watched the stars." "The night sky is interesting." "There are patterns there." "If you look closely, you can see pictures." "One of the easiest constellations to recognize lies in the northern skies." "In North America, it's called the Big Dipper." "The French have a similar idea." "They call it La Casserole." ""The casserole."" "In medieval England, the same pattern of stars reminded people of a simple wooden plow." "The ancient Chinese had a more sophisticated notion." "To them these stars carried the celestial bureaucrat on his rounds about the sky seated on the clouds and accompanied by his eternally hopeful petitioners." "The people of northern Europe imagined another pattern." "To them it was Charles' Wain, or wagon." "A medieval cart." "But other cultures saw these seven stars as part of a larger picture." "It was the tail of a great bear which the ancient Greeks and Native Americans saw instead of the handle of a dipper." "But the most imaginative interpretation of this larger group of stars was that of the ancient Egyptians." "They made out a curious procession of a bull and a reclining man followed by a strolling hippopotamus with a crocodile on its back." "What a marvelous diversity in the images various cultures saw in this particular constellation." "But the same is true for all the other constellations." "Some people think these things are really in the night sky but we put these pictures there ourselves." "We were hunter folk so we put hunters and dogs lions and young women up in the skies." "All manner of things of interest to us." "When 17th century European sailors first saw the southern skies they put all sorts of things of 17th century interest up there." "Microscopes and telescopes, compasses and the sterns of ships." "If the constellations had been named in the 20th century I suppose we'd put there refrigerators and bicycles rock stars, maybe even mushroom clouds." "A new set of human hopes and fears placed among the stars." "But there's more to the stars than just pictures." "For example, stars always rise in the east and always set in the west taking the whole night to cross the sky if they pass overhead." "There are different constellations in different seasons." "The same constellations always rise at, say, the beginning of autumn." "It never happens that a new constellation suddenly appears out of the east, one that you never saw before." "There's a regularity, a permanence a predictability about the stars." "In a way, they're almost comforting." "The return of the sun after a total eclipse its rising in the morning after its troublesome absence at night and the reappearance of the crescent moon after the new moon all spoke to our ancestors of the possibility of surviving death." "Up there in the skies was a metaphor of immortality." "Almost a thousand years ago in the American Southwest the Anasazi people built a stone temple an astronomical observatory to mark the longest day of the year." "Dawn on that day must have been a joyous occasion a celebration of the generosity of the sun." "They built this ceremonial calendar so that the sun's rays would penetrate a window and enter a particular niche on this day alone." "That kind of precision is a triumph of human intelligence." "It outlives its creators." "Today, this is a lonely place." "The Anasazi people are no more." "They had learned to predict the changing of the seasons." "They could not predict the changing of the climate and the failure of the rains." "But their temple continues to catch the sun's first rays on the summer solstice." "I imagine the Anasazi people gathered in these pews every June 21  dressed with feathers and turquoise to celebrate the power of the sun." "These upper niches there are 28 of them may represent the number of days for the moon to reappear in the same constellation." "These people paid a lot of attention to the sun and the moon and the stars." "And other devices based on somewhat similar designs can be found in Angkor Wat in Cambodia Stonehenge in England Abu Simbel in Egypt Chichén Itzá in Mexico and in the Great Plains of North America." "Now, why did people all over the world go to such great trouble to teach themselves astronomy?" "It was literally a matter of life and death to be able to predict the seasons." "We hunted antelope or buffalo whose migrations ebbed and flowed with the seasons." "Fruits and nuts were ready to be picked in some times and not in others." "When we invented agriculture, we had to take care and sow our seeds and harvest our crops at just the right season." "Annual meetings of far-flung nomadic peoples were set for prescribed times." "Now..." "Some alleged calendrical devices might be due to chance." "For example the accidental alignment of a window and a niche but there are other devices, wonderfully different." "Today, only the dry ruins of the great Anasazi cities have survived the ravages of time." "Not far from these ancient cities in an almost inaccessible location there is another solstice marker." "This one of singular and unmistakable purpose." "The deliberate arrangement of three great stone slabs allows a sliver of sunlight to pierce the heart of a carved spiral only at noon on the longest day of the year." "(WIND WHISTLES)" "The wind whips through the canyons here in the American Southwest and there's no one to hear it but us." "A reminder of the 40,000 generations of thinking men and women who preceded us about whom we know next to nothing upon whom our society is based." "When our prehistoric ancestors studied the sky after sunset they observed that some of the stars were not fixed with respect to the constant pattern of the constellations." "Instead, five of them moved slowly forward across the sky then backward for a few months, then forward again as if they couldn't make up their minds." "We call them planets the Greek word for "wanderers"." "These planets presented a profound mystery." "The earliest explanation was that they were living beings." "How else explain their strange, looping behavior?" "Later, they were thought to be gods and then disembodied astrological influences." "But the real solution to this particular mystery is that planets are worlds, that the Earth is one of them and that they go around the sun according to precise mathematical laws." "This discovery has led directly to our modern global civilization." "The merging of imagination with observation produced an exact description of the solar system." "Only then could you answer the fundamental question at the root of modern science:" "What makes it all go?" "Two thousand years ago, no such question would have been asked." "The prevailing view had then been formulated by Claudius Ptolemy an Alexandrian astronomer and also the preeminent astrologer of his time." "Ptolemy believed that the Earth was the center of the universe that the sun and the moon and the planets like Mars went around the Earth." "It's the most natural idea in the world." "The earth seems steady, solid, immobile while we can see the heavenly bodies rising and setting every day." "But then, how explain the loop-the-loop motion of the planets in the sky?" "Mars, for example?" "This little machine shows Ptolemy's model." "The planets were imagined to go around the Earth attached to perfect crystal spheres but not attached directly to the spheres but indirectly through a kind of off-center wheel." "The sphere turns, the little wheel rotates and as seen from the Earth, Mars does its loop-the-loop." "This model permitted reasonably accurate predictions of planetary motion." "Good enough predictions for the precision of measurement in Ptolemy's time and much later." "Supported by the church through the Dark Ages Ptolemy's model effectively prevented the advance of astronomy for 1 500 years." "Finally, in 1 543, a quite different explanation of the apparent motion of the planets was published by a Polish cleric named Nicolaus Copernicus." "Its most daring feature was the proposition that the sun was the center of the universe." "The Earth was demoted to just one of the planets." "The retrograde, or loop-the-loop motion happens as the Earth overtakes Mars in its orbit." "You can see that, from the standpoint of the Earth Mars is now going slightly backwards and now it is going in its original direction." "This Copernican model worked at least as well as Ptolemy's crystal spheres." "But it annoyed an awful lot of people." "The Catholic Church later put Copernicus' work on its list of forbidden books." "And Martin Luther described Copernicus in these words:" ""People give ear to an upstart astrologer." "This fool wishes to reverse the entire science of astronomy."" "Close quote." "The confrontation between the two views of the cosmos Earth-centered and sun-centered reached its climax with a man who, like Ptolemy, was both an astronomer and an astrologer." "He lived in a time when the human spirit was fettered and the mind chained when angels and demons and crystal spheres were imagined up there in the skies." "Science still lacked the slightest notion of physical laws underlying nature." "But the brave and lonely struggle of this man was to provide the spark that ignited the modern scientific revolution." "Johannes Kepler was born in Germany in 1 57 1." "He was sent to the Protestant seminary school in Maulbronn to be educated for the clergy." "(BELL RINGS)" "It was a strict, disciplined life." "Up before dawn to begin a long day of prayer and study." "This was the age of the Reformation." "Maulbronn was a kind of educational and ideological boot camp training young Protestants in theological weaponry against the fortress of Roman Catholicism." "(SPEAKS IN GERMAN)" "There was little reassurance or comfort here for a sensitive boy like Kepler." "He was intelligent and he knew it." "That, together with his stubbornness and his fierce independence served to isolate him from the other boys." "Kepler made few friends in his two years at Maulbronn." "Amen." "So he kept to himself, withdrawn into the world of his own thoughts which were often concerned with his imagined unworthiness in the eyes of God." "He despaired of ever attaining salvation." "(SPEAKS IN GERMAN)" "But God to him was more than punishment." "God was also the creative power of the universe." "And the young Kepler's curiosity about God was even greater than his fear." "He wanted to know God's plan for the world." "He wanted to read the mind of God." "This was his obsession." "It was to inspire all his great achievements." "It was to take him, and Europe out of the cloister of medieval thought." "In places like Maulbronn, the faint echoes of the genius of antiquity still reverberated." "Here, in addition to theology Kepler was exposed to Greek and Latin, music and mathematics." "And it was in geometry that he thought he glimpsed the image of perfection." "He was later to write:" ""Geometry existed before the Creation." "It is coeternal with the mind of God." "Geometry provided God with a model for the Creation." "Geometry is God himself."" "But the real world of Kepler's time was far from perfect." "It was haunted by fear, pestilence, famine and war." "Superstition was a natural refuge for people who were powerless." "Only one thing seemed certain:" "the stars themselves." "It was remembered that in ancient times, the astrologer, Ptolemy and the sage, Pythagoras, had taught that the heavens were harmonious and changeless." "Ptolemy had said that the motions of the planets through the stars were portents of events here below." "Was it the influence of Mars and Venus that made his father a brutal man a mercenary who had abandoned him?" "(CHILDREN LAUGHING)" "Did an unfortunate conjunction of planets in an adverse sign make his mother a mischievous and quarrelsome woman?" "If such things were fated by the stars then perhaps there were hidden patterns underlying the unpredictable chaos of daily life." "Patterns as constant as the stars." "But how could you discover them?" "Where would you begin?" "If the world and everything in it was crafted by God then shouldn't you begin with a careful study of physical reality?" "Was not all of creation an expression of the harmonies in the mind of God?" "The book of nature had waited 1,500 years for a reader." "In 1 589, Kepler left Maulbronn to continue his studies at the great university in Tübingen." "It was a liberation to find himself amidst the most vital intellectual currents of the time." "One of his teachers revealed to him the revolutionary ideas of Copernicus." "Kepler relished this urbane scholarly community." "Here, his genius was recognized at last." "Kepler was not to be ordained after Tübingen." "Instead, to his surprise, he found himself summoned to Graz in Austria to become a teacher of high school mathematics." "Kepler was not a very good teacher." "The first year in Graz, his class had only a handful of students." "The second year, none." "He mumbled." "He digressed." "He was, at times, utterly incomprehensible." "He was distracted by an incessant clamor of speculations and associations that ran through his head." "(MUMBLES)" "One pleasant summer afternoon with his students longing for the end of the lecture he was visited by a revelation that was to alter radically the future course of astronomy and the world." "(TOP CLUNKS)" "There were only six planets known in his time:" "Mercury, Venus, Earth, Mars, Jupiter and Saturn." "For some time, Kepler had been wondering:" "Why only six planets?" "Why not 20 planets, or 100?" "And why this particular spacing between their orbits?" "No one had ever asked such questions before." "In the course of a lecture on astrology Kepler inscribed within the circle of the zodiac a triangle with three equal sides." "He then noticed, quite by accident that a smaller circle inscribed within the triangle bore the same relationship to the outer circle as did the orbit of Jupiter to the orbit of Saturn." "Could a similar geometry relate the orbits of the other planets?" "Now Kepler remembered the perfect solids of Pythagoras." "Of all the possible three-dimensional shapes there were only five whose sides were regular polygons." "He believed that the two numbers were connected that the reason there were only six planets was that there were only five regular solids." "In these perfect solids, nested one within the other he believed he had discovered the invisible supports for the spheres of the six planets." "This connection between geometry and astronomy could admit only one explanation:" "The hand of God, mathematician." ""The intense pleasure I received from this discovery can never be told in words," he said." ""Now I no longer became weary at work." "Days and nights I passed in mathematical labors until I could see if my hypothesis would agree with Copernicus' or if my joy would vanish into thin air."" "But no matter how he hard tried, the perfect solids and planetary orbits did not agree with each other very well." "Why didn't it work?" "Because, unfortunately, it was wrong." "The true orbital sizes of the planets we now know have absolutely nothing to do with the five perfect solids as the later discovery of Uranus, Neptune and Pluto shows." "But Kepler spent the rest of his life pursuing this geometrical phantasm." "He couldn't abandon it, and he couldn't make it work." "His frustration must have been enormous." "Finally he decided that the accepted planetary observations were inaccurate and not his model of the nested solids." "Only one man had access to more precise observations." "That man was Tycho Brahe who, coincidentally, had recently written Kepler to come and join him." "Kepler was reluctant at first, but he had no choice." "In 1 598, a wave of oppression enveloped Graz." "It was spearheaded by the local archduke who vowed to restore Catholicism to the province and in his own words "would rather make a desert of the country than rule over heretics."" "Kepler's school was closed." "People were forbidden to worship or to sing hymns or to own books of a heretical nature." "Those who refused Catholicism were fined 10% of their assets and exiled from the country on pain of death." "Kepler chose exile." ""Hypocrisy, I have never learned." "I am in earnest about faith." "I do not play with it."" "For Kepler, it was only the first in a series of exiles forced upon him by religious fanatics." "Now he decided to accept Tycho Brahe's open invitation." "Brahe, a wealthy Danish nobleman, lived in great splendor and had recently been appointed Imperial Mathematician at Prague." "Kepler left Graz with his wife and stepdaughter and set out on the difficult journey." "Kepler's wife was not a happy woman." "She was chronically ill and had recently lost two young children." "The marriage was no comfort." "She had no understanding of his work and regarded his profession with contempt." "Kepler was married to his work and every tedious mile was bringing him closer to the great Tycho Brahe, whose observations he devoutly hoped, would confirm his theory." "Kepler envisioned Tycho's domain as a sanctuary from the evils of the time." "He aspired to be a worthy colleague to the illustrious Tycho who for 35 years had been immersed in exact measurements of a clockwork universe ordered and precise." "(PARTY CHATTER)" "(MUSIC PLAYS)" "(LAUGHING)" "But Tycho's court was not at all what Kepler had expected." "TYCHO:" "Vinol" "Tycho himself was a flamboyant figure adorned with a gold nose." "The original was lost in a student duel fought over who was the superior mathematician." "And he maintained a circus-like entourage of assistants, distant relatives and assorted hangers-on." "(SPEAKING IN FOREIGN LANGUAGE)" "Kepler had no use for the endless revelry." "He impatient to see Tycho's data." "But Tycho would give him only a few scraps at a time." ""Tycho," he said, "gave me no opportunity to share in his studies." "He would only, in the course of a meal, mention as if in passing today, the figure of the apogee of one planet." "Tomorrow, the nodes of another."" "Kepler was ill-suited for such games and the general climate of intrigue offended his sense of propriety." "Their cruel mockery of the pious and scholarly Kepler depressed and saddened him." ""My opinion of Tycho is this:" "He is superlatively rich but knows not how to make proper use of it."" "Tycho possesses the best observations, he also has collaborators." "He lacks only the architect who would put all this to use."" "(BAND PLAYS)" "Tycho was unable to turn his observations into a coherent theory of the solar system." "He knew he needed the brilliant Kepler's help." "But simply to hand over his life's work to a potential rival?" "That was unthinkable." "(KEPLER SHOUTS)" "Tycho was the greatest observational genius of the age and Kepler the greatest theoretician." "Either man alone could not achieve the synthesis which both felt was now possible." "TYCHO:" "Keplerel" "The birth of modern science which is the fusion of observation and theory teetered on the precipice of their mutual distrust." "The two repeatedly quarreled and were reconciled." "Until, a few months later Tycho died of his habitual overindulgence in food and wine." "Kepler wrote to a friend:" ""On the last night of Tycho's gentle delirium he repeated over and over again these words like someone composing a poem:" "'Let me not seem to have lived in vain." "Let me not seem to have lived in vain.'" "And he did not."" "Eventually, after Tycho's death Kepler contrived to extract the observations from Tycho's reluctant family." "Observations of the apparent motion of Mars through the constellations obtained over a period of many years." "The data, from the last few decades before the invention of the telescope were by far the most precise ever obtained up to that time." "Kepler worked with a kind of passionate intensity to understand Tycho's observations." "What real motions of the Earth and Mars about the sun could explain, to the precision of measurement the apparent motion, as seen from the Earth, of Mars in the sky." "And why Mars?" "Tycho had told Kepler that the apparent motion of Mars was the most difficult to reconcile with a circular orbit." "After years of calculation, he believed he'd found the values for a Martian circular orbit which matched ten of Tycho Brahe's observations within two minutes of arc." "There are sixty minutes of arc in an angular degree and of course, 90 degrees from horizon to zenith." "So a few minutes of arc is a small quantity to measure especially without a telescope." "But Kepler's ecstasy of discovery soon crumbled into gloom." "Two further observations by Tycho were inconsistent with his orbit by as much as eight minutes of arc." "Kepler wrote, "If I had believed we could ignore these eight minutes I would've patched up my hypothesis accordingly." "Since it was not permissible to ignore them those eight minutes pointed the road to a complete reformation of astronomy."" "The difference between a circular orbit and the true orbit of Mars could be distinguished only by precise measurement and by a courageous acceptance of the facts." "Kepler was profoundly annoyed at having to abandon a circular orbit." "It shook his faith in God as the Maker of a perfect celestial geometry." ""Having cleaned the stable of astronomy of circles and spirals," he said he was left with "only a single cartful of dung."" "He tried various oval-like curves, calculated away made some arithmetical mistakes which caused him to reject the correct answer." "Months later, in some desperation he tried the formula for the first time for an ellipse." "The ellipse matched the observations of Tycho beautifully." "In such an orbit, the sun isn't at the center." "It is offset." "It's at one focus of the ellipse." "When a given planet is at the far point in its orbit from the sun it goes more slowly." "As it approaches the near point, it speeds up." "Such motion is why we describe the planets as forever falling towards the sun but never reaching it." "Kepler's first law of planetary motion is simply this:" "A planet moves in an ellipse with the sun at one focus." "As a planet moves along its orbit, it sweeps out in a given period of time, an imaginary wedge-shaped area." "When the planet's far from the sun, the area's long and thin." "When the planet is close to the sun, the area is short and squat." "Though the shapes of the wedges are different Kepler found that their areas are exactly the same." "This provided a precise description of how a planet changes its speed in relation to its distance from the sun." "Now, for the first time astronomers could predict where a planet would be in accordance with a simple and invariable law." "Kepler's second law is this:" "A planet sweeps out equal areas in equal times." "Kepler's first two laws of planetary motion may seem a little remote and abstract." "Planets move in ellipses and they sweep out equal areas in equal times." "So what?" "It's not as easy to grasp as circular motion." "We might have a tendency to dismiss it to say it's a mere mathematical tinkering something removed from everyday life." "But these are the laws our planet itself obeys." "As we, glued by gravity to the surface of the Earth hurtle through space we move in accord with laws of nature which Kepler first discovered." "When we send spacecraft to the planets when we observe double stars when we examine the motion of distant galaxies we find that all over the universe, Kepler's laws are obeyed." "Many years later Kepler came upon his third and last law of planetary motion." "A law which relates the motion of the various planets to each other which lays out correctly the clockwork of the solar system." "He discovered a mathematical relationship between the size of a planet's orbit and the average speed at which it travels around the sun." "This confirmed his long-held belief that there must be a force in the sun that drives the planets." "A force stronger for the inner, fast-moving planets and weaker for the outer, slow-moving planets." "Isaac Newton later identified that force as gravity." "Answering at last the fundamental question:" "What makes the planets go?" "Kepler's third or Harmonic Law states that the squares of the periods of the planets the time for them to make one orbit are proportional to the cubes, the third power of their average distances from the sun." "So the further away a planet is from the sun, the slower it moves but according to a precise mathematical law." "Kepler was the first person in the history of the human species to understand correctly and quantitatively how the planets move how the solar system works." "The man who sought harmony in the cosmos was fated to live at a time of exceptional discord on Earth." "Exactly eight days after Kepler's discovery of his third law there occurred in Prague an incident that unleashed the devastating Thirty Years' War." "The war's convulsions shattered the lives of millions of people." "Kepler lost his wife and young son to an epidemic spread by the soldiery." "His royal patron was deposed and he was excommunicated from the Lutheran church for his uncompromising independence on questions of belief." "He was a refugee once again." "The conflict portrayed on both sides as a "holy war" was more an exploitation of religious bigotry by those hungry for land and power." "This war introduced organized pillage to keep armies in the field." "The brutalized population of Europe stood by helpless as their plowshares and pruning hooks were literally beaten into swords and spears." "Rumor and paranoia swept through the countryside enveloping especially the powerless." "Among the many scapegoats chosen were elderly women living alone, who were charged with witchcraft." "(THUNDER)" "(HORSE WHINNIES)" "(WOMAN CRIES)" "Kepler's mother was taken away in the middle of the night in a laundry chest." "It took Kepler six years of unremitting effort to save her life." "In Kepler's little hometown, about three women were arrested tortured and killed as witches every year between 1 61 5 and 1 629." "And Katarina Kepler was a cantankerous old woman." "She engaged in disputes which annoyed the local nobility and she sold drugs." "Poor Kepler thought that he himself had contributed inadvertently, to his mother's arrest." "It came about because he had written one of the first works of science fiction." "It was intended to explain and popularize science and was called The Somnium." ""The Dream."" "He imagined a journey to the moon with the space travelers standing on the lunar surface looking up to see, rotating slowly above them the lovely planet Earth." "Part of the basis for the charge of witchcraft was that in his dream, Kepler used his mother's spells to leave the Earth." "But he really believed that one day human beings would launch celestial ships with sails adapted to the breezes of heaven filled with explorers who, he said "would not fear the vastness of space."" "He speculated on the mountains, valleys, craters climate and possible inhabitants of the moon." "Before Kepler astronomy had little connection with physical reality." "But with Kepler came the idea that a physical force moves the planets in their orbits." "He was the first to combine a bold imagination with precise measurements to step out into the cosmos." "It changed everything." "This fusion of facts with dreams opened the way to the stars." "As a boy Kepler had been captured by a vision of cosmic splendor a harmony of the worlds which he sought so tirelessly all his life." "Harmony in this world eluded him." "His three laws of planetary motion represent we now know a real harmony of the worlds." "But to Kepler, they were only incidental to his quest for a cosmic system based on the perfect solids." "A system which, it turns out, existed only in his mind." "Yet, from his work we have found that scientific laws pervade all of nature that the same rules apply on Earth as in the skies that we can find a resonance, a harmony between the way we think and the way the world works." "When he found that his long-cherished beliefs did not agree with the most precise observations he accepted the uncomfortable facts." "He preferred the hard truth to his dearest illusions." "That is the heart of science." "SAGAN:" "This is the age of planetary exploration when our ships have begun to sail the heavens." "In those heavens, there are some worlds much like hell." "Our planet is, in comparison, much like a heaven." "But the gates of heaven and hell are adjacent and unmarked." "The Earth is a lovely and more or less placid place." "Things change, but slowly." "You can lead a full life and never encounter a natural catastrophe more violent than a storm." "And so we become complacent relaxed unconcerned." "But in the history of the solar system and even in human history there are clear records of extraordinary and devastating catastrophes." "We have now achieved the dubious distinction of making our own major catastrophes both intentional and inadvertent." "On the landscapes of other planets where past records are better preserved there's abundant evidence of major catastrophes." "It's all a matter of time scale." "An event which is improbable in 1 00 years may be inevitable in 1 00 million." "But even on the Earth in this century there have been bizarre natural events." "In remote central Siberia there was a time when the Tungus people told strange tales of a giant fireball that split the sky and shook the Earth." "They told of a blast of searing wind that knocked down people and forests." "It happened, they said, on a summer's morning in the year 1908." "In the late 1920s L.A. Kulik, a Soviet scientist organized expeditions to try and solve the mystery." "He built boats to penetrate this trackless land:" "Snowbound in winter a swampy morass in summer." "Eyewitnesses told of a ball of flame larger than the sun that had blazed across the sky 20 years before." "Kulik assumed a giant meteorite had struck the Earth." "He expected to find an enormous impact crater and rare meteorite fragments chipped off some distant asteroid." "However, at ground zero Kulik found upright trees stripped of their branches but not a trace of the meteorite or its impact crater." "He was deeply puzzled." "He thought there were meteorite fragments buried in the swampy ground." "So he set about digging trenches and pumping out the water." "But the expected meteoritic rock and iron was not found." "Undaunted, Kulik went on to make a thorough survey despite the swarms of insects and other hardships." "Because he discovered something that, in his own words "exceeded all tales of eyewitnesses and my wildest expectations."" "For more than 20 kilometers in every direction from ground zero the trees were flattened radially outward like broken matchsticks." "There must've been a powerful explosion several kilometers above the ground." "The pressure wave, spreading out at the speed of sound was reconstructed from barometric records at weather stations across Siberia, through Russia and on into Western Europe." "Dust from the explosion reflected so much sunlight back to Earth that people could read by it at night in London, 10,000 kilometers away." "This really remarkable occurrence is called the Tunguska Event." "But what was it?" "Well, perhaps, some scientists have suggested it was a chunk of antimatter from space annihilated on contact with the ordinary matter of the Earth disappearing in a flash of gamma rays." "But the radioactivity you'd expect from matter-antimatter annihilation is to be found nowhere at the impact site." "Or, perhaps, other scientists have suggested it was a mini black hole from space which impacted the Earth in Siberia tunneled through the solid body of Earth and plunged out the other side." "But the records of atmospheric shock waves give not a hint of something booming out of the North Atlantic later that day." "Or maybe, other people have speculated, it was a spaceship of some unimaginably advanced extraterrestrial civilization in desperate mechanical trouble crashing in a remote region of an obscure planet." "Well, if so, it's pretty startling that at the impact site there is not a piece, not the tiniest transistor of a crashed spacecraft." "More prosaically, perhaps it was a large meteorite or a small asteroid which hit the Earth." "But even here, there are no observable telltale rocky or metallic fragments of the sort that you'd expect from such an impact." "The key point of the Tunguska Event is that there was a tremendous explosion, a great shock wave many trees burned, an enormous forest fire and yet, no crater in the ground." "There seems to be only one explanation which is consistent with these facts." "And that explanation is this:" "In 1 908, a piece of a comet hit the Earth." "No one saw it approach." "A small point of light lost in the glare of the morning sun." "It had been drifting for centuries through the inner solar system like an iceberg in the ocean of interplanetary space." "But this time, by accident there was a planet in the way." "From the time and direction of its approach, what hit the Earth seems to have been a fragment of a comet named Encke." "Hurtling at more than 100,000 kilometers an hour it was a mountain of ice about the size of a football field and weighing almost a million tons." "There was no warning, until it plunged into the atmosphere." "(COMET RUMBLES)" "If such an explosion happened today it might be thought, in the panic of the moment to be produced by a nuclear weapon." "Such a cometary impact and fireball simulates all the effects of a 15-megaton nuclear burst including the mushroom cloud, with one exception:" "There would be no radiation." "So could a rare but natural event the impact of a comet with Earth trigger a nuclear war?" "It's a strange scenario:" "A small comet hits the Earth as millions have during Earth's history and the response of our civilization is promptly to self-destruct." "Maybe it's unlikely, but it might be a good idea to understand comets and collisions and catastrophes a little bit better than we do." "Now, a comet, at least as far as we understand them today is made mostly of ice:" "Water ice, maybe some ammonia ice a little bit of methane ice." "So in striking the Earth's atmosphere a modest cometary fragment will produce a great radiant fireball and a mighty blast wave." "It'll burn trees and level forests and make a sound heard around the world." "But it need not make a crater in the ground." "Why?" "Because the ices in the comet are all melted in the impact." "And there's going to be very few recognizable pieces of comet left on the ground." "We humans like to think of the heavens as stable serene, unchanging." "But comets suddenly appear and hang ominously in the sky, night after night, for weeks." "So the idea developed that the comet had to be there for a reason." "The reason was that comets were predictions of disaster that they foretold the deaths of princes and the fall of kingdoms." "In 1 066, for example the Normans witnessed an apparition or appearance of Halley's comet." "Since a comet must, they thought, predict the fall of some kingdom they promptly invaded England." "Here's King Harold of England looking a little glum." "The events were noted in the Bayeux tapestry a kind of newspaper of the day." "Or, in the early 13th century Giotto, one of the founders of modern realistic painting witnessed another apparition of comet Halley and inserted it into a nativity he was painting." "A harbinger of a different sort of change of kingdoms." "Around 1517 another great comet appeared." "This time it was seen in Mexico." "And the Aztec emperor, Moctezuma maybe this is he promptly executed his astrologers." "Why?" "They hadn't predicted the comet, and they sure hadn't explained it." "Moctezuma was positive that the comet foretold some dreadful disaster." "He became distant and gloomy and in that way, helped to set the stage for the successful Spanish conquest of Mexico under Cortés." "In many cases, a superstitious belief in comets becomes a self-fulfilling prophecy." "Here are two quite different representations of the great comet of 1 577:" "This one pictured by the Turks and this one by the Germans." "In 1 705, Edmund Halley finally figured out that the same spectacular comet was booming by the Earth every 76 years, like clockwork." "That comet is now called, appropriately, comet Halley." "And it's the same one that we talked about before, the comet of 1 066." "At that point, the subject began to lose a little of its burden of superstition, but hardly all." "Public fear of comets survived." "Well, for example look at this terribly nasty comet of 1 857 that some people figured would splinter the Earth." "By 1 91 0, Halley's comet returned once more." "But this time, astronomers using a new tool, the spectroscope had discovered cyanogen gas in the tail of a comet." "Now, cyanogen is a poison." "The Earth was to pass through this poisonous tail." "The fact that the gas was astonishingly, fabulously thin reassured almost nobody." "For example, look at the headlines in the Los Angeles Examiner for May 9, 1 91 0:" ""Say, Has That Comet 'Cyanogened' You Yet?"" ""Entire Human Race Due For Free Gaseous Bath." "Expect High Jinks."" "Or take this from the San Francisco Chronicle, May 15, 1910:" ""Comet Comes And Husband Reforms."" ""Comet Parties Now Fad In New York."" "Amazing stuff!" "In 1 91 0, people were holding comet parties, not so much to celebrate the end of the world as to make merry before it happened." "There were entrepreneurs who were hawking comet pills." "I think I'm gonna take one for later." "And there were those who were selling gas masks to protect against the cyanogen." "And comet nuttiness didn't stop in 1910." "Long before 1066, humans marveled at comets." "Our generation is beginning to understand them." "Mercury, Venus, Earth and Mars are small planets made mostly of rock and iron." "Farther out where it's colder, are the giant planets made mostly of gas." "But comets originate from a great cloud beyond the planets almost halfway to the nearest star." "Occasionally, one falls in accelerated by the sun's gravity." "Because it's made mostly of ice, the comet evaporates as it approaches the sun." "The vapor is blown back by the solar wind forming the cometary tail." "Then it's flung back into outer darkness its orbit so large that it will not return for millions of years." "These are the long-period comets." "For every one plunging close enough to the sun to be discovered there may be a billion others slowly drifting beyond Pluto's orbit." "Very rarely, a long-period comet is captured in the inner solar system becoming a short-period comet." "It passes near a major planet, like Saturn." "The planet provides a small gravitational tug enough to deflect it into a much smaller orbit." "Though few are captured this way, those that are become well-known because they all return in short intervals." "Once trapped in the inner solar system, among the planets the chances of another near-collision are increased." "Here, a second encounter with Saturn further reduces the comet's orbital period to decades." "A comet may take 10,000 years between close planetary encounters." "But in this computer study, we've sped things up." "A third encounter, this time with Jupiter further reduces the comet's orbital period." "Now the comet must approach the sun and grow a tail every few years." "Since the dust and gas in the tail are lost forever to space the comet must slowly be eroding." "Pieces of it break off." "Sometimes, as we've seen, they even strike the Earth." "In a few thousand years if a short-period comet hasn't hit a planet it will have evaporated away almost entirely leaving sand-sized fragments, which become meteors and its core which, perhaps, becomes an asteroid." "Suppose I were a pretty typical comet." "And what you would see would be a kind of tumbling snowball spending most of my time out here in the outer solar system." "I'd be a kilometer across." "I'd be living most of my days in the gloom beyond Saturn, orbiting the sun." "But once every century, I would find myself careening inward, faster and faster towards the inner solar system." "By the time I would cross the orbit of Jupiter on my way to the orbit of Mars I'd be heating up because I'd be getting closer to the sun." "I'd be evaporating a little bit." "Small pieces of dust and ice would be blown behind me by the solar wind forming an incipient cometary tail." "On the scale of such a solar system model I, me, a cometary nucleus would be smaller than a snowflake." "Although, when fully developed, my tail would be longer than the spacing between the worlds." "Now, sooner or later must collide with planets." "The Earth and the moon must have been bombarded by comets and asteroids the debris from the early history of the solar system." "In interplanetary space, there are more small objects than large ones." "So there must be, on a given planetary surface many more impacts of small objects than of large objects." "So a thing like the Tunguska impact happens on the Earth maybe every thousand years." "But the impact of a giant cometary nucleus like Halley's comet, let's say happens only every billion years or so." "Now, is there evidence of past collisions?" "When a large comet or a large, rocky asteroid hits a planet it makes a bowl-shaped crater." "The well-preserved impact craters on Earth were all formed fairly recently." "The older ones have been softened, filled in or rubbed out by running water and mountain building." "Impacts make craters on other worlds and about as often." "But when the air is thin when water rarely flows, when mountain building is feeble the ancient craters are retained." "This is the case on the moon and Mercury and Mars our neighboring terrestrial planets." "They huddle around the sun their source of heat and light a little bit like campers around a fire." "They are about 4½ billion years old." "And all bear witness to an age long gone of major collisions which do not happen at that scale and frequency anymore." "If we move out past the terrestrial planets beyond Mars we find ourselves in a different regime of the solar system in the realm of Jupiter and the other giant, or Jovian planets." "These are great worlds composed largely of the gases hydrogen and helium, some other stuff too." "When we look at the surface, we do not see a solid surface but only an occasional patch of atmosphere and a complex array of multicolored clouds." "These are serious planets not fragmentary little world-lets like the Earth." "In fact, 1 000 Earths would fit in the volume of Jupiter." "If a comet or asteroid were to accidentally impact Jupiter, it would be very unlikely to leave a crater." "It might make a momentary hole in the clouds, but that's it." "Nevertheless, we know that the outer solar system has been subject to a many-billion-year history of impact cratering." "Jupiter's moon Callisto is studded with thousands of craters." "Clear evidence of ancient collisions beyond Mars." "And there are craters on other moons of Jupiter." "Most of the thousands of large craters on our own moon were excavated billions of years ago." "But were any recorded in historical times?" "The odds against it are about 1000-to-one." "(BELL RINGS)" "Nevertheless, there's a possible eyewitness account of just such an event." "It was the Sunday before the feast of Saint John the Baptist in the summer of 1178." "The monks of Canterbury Cathedral had completed their evening prayers and were about to retire for the night." "The scholarly brother, Gervase returned to his cell to read while some of the others went outside to enjoy the gentle June air." "(PLAYS FLUTE)" "In the midst of their recreation they chanced to witness an astonishing sight:" "A violent explosion on the moon." "This was a time when the heavens were thought to be changeless." "The moon, the stars and the planets were deemed pure because they followed an unvarying celestial routine." "They were expected to behave without unseemly disruptions like monks in a monastery." "Was it wise to discuss such a vision?" "In every time and culture there are pressures to conform to the prevailing prejudices." "But there are also, in every place and epoch those who value the truth, who record the evidence faithfully." "Future generations are in their debt." "A fire on the moon." "Might it be some portent of ill fortune?" "Should the chronicler of the monastery be told?" "Was this event an apparition of the evil one?" "Gervase of Canterbury was a historian considered today a reliable reporter of political and cultural events of his time." "This is his account of the eyewitness testimony he was given:" ""Now there was a bright new moon and as usual in that phase its horns were tilted toward the east." "And suddenly the upper horn split in two." "From the midpoint of this division, a flaming torch sprang up spewing out over a considerable distance fire, hot coals and sparks." "After these transformations," Gervase continued "the moon from horn to horn that is along its whole length took on a blackish appearance."" "Gervase took depositions from all the eyewitnesses." "He later wrote:" ""The writer was given this report by men who saw it with their own eyes and are prepared to stake their honor on an oath that they have made no addition or falsification."" "Gervase committed the account to paper enabling astronomers eight centuries later to try and reconstruct what really happened." "It may be that 200 years before Chaucer five monks saw an event more wonderful than many another celebrated Canterbury tale." "If a small drifting mountain were to hit the moon it would set our satellite swinging like a bell." "Eventually, the tremors would die down, but not in a mere 800 years." "So is the moon still quivering from that impact?" "The Apollo astronauts emplaced arrays of special mirrors on the moon." "Reflectors made by French scientists were also put on the moon by Soviet Lunakhod vehicles." "When a laser beam from Earth strikes a mirror and bounces back the roundtrip travel time can be measured." "At the McDonald Observatory of the University of Texas a laser beam is prepared for firing at the reflectors on the moon 380,000 kilometers away." "By multiplying the travel time by the speed of light the distance to that spot can be determined to a precision of 7 to 10 centimeters:" "The width of a hand." "When such measurements are repeated over years even an extremely slight wobble in the moon's motion can be determined." "The accuracy is phenomenal." "The error is much less than one-millionth of a percent." "The moon, it turns out, is gently swinging like a bell just as if it had been hit by an asteroid less than 1000 years ago." "(RINGING)" "So there may be physical evidence in the age of space flight for the account of the Canterbury monks in the 12th century." "If 800 years ago a big asteroid hit the moon the crater should be prominent today still surrounded by bright rays thin streamers of dust spewed out by the impact." "In billions of years, lunar rays are eroded but not in hundreds." "And there is a recent ray crater called Giordano Bruno in the region of the moon where an explosion was reported in 1178." "The entire evolution of the moon is a story of catastrophes." "4 1/2 billion years ago the moon was accreting from interplanetary boulders and craters were forming all over its surface." "The energy so released helped melt the crust." "After most of this debris was swept up by the moon, the surface cooled." "But about 3.9 billion years ago a great asteroid impacted." "It generated an expanding shock wave and re-melted some of the surface." "The resulting basin was then flooded probably by dark lava producing one of the dry seas on the moon." "More recent impacts excavated craters with bright rays named after Eratosthenes and Copernicus." "The familiar features of the man in the moon are a chronicle of ancient impacts." "Most of the original asteroids were swept up in the making of the moon and planets." "Many still orbit the sun in the asteroid belt." "Some, themselves almost fractured by gravity tides and by impacts with other asteroids have been captured by planets:" "Phobos around Mars, for example or a close moon of Jupiter called Amalthea." "Similar to the asteroid belt are the rings of Saturn..." "Maybe the rings of Saturn are a moon which was prevented from forming by the tides of Saturn." "Or maybe it's the remains of a moon that wandered too close and was torn apart by the tides of Saturn." "It's certainly a lovely place." "Jupiter also has a newly discovered ring system which is invisible from the Earth." "Now, there is a curious argument alleging major recent collisions in the solar system proposed by a psychiatrist named Immanuel Velikovsky in 1 950." "He suggested that an object of planetary mass, which he called a comet was somehow produced in the Jupiter system." "He doesn't say exactly how it's produced but maybe it's spat out of Jupiter." "Anyway, however it was made some 3500 years ago, he imagines it made repeated close encounters with Mars with the Earth-moon system having as entertaining biblical consequences the parting of the Red Sea so that Moses and the Israelites could safely avoid the host of pharaoh and the stopping of the Earth's rotation when Joshua commanded the sun to stand still in Gibeon." "He also imagined that there was extensive flooding and the volcanoes all over the Earth at that time." "Well, then after a very complicated game of interplanetary billiards is completed Velikovsky proposed that this comet entered into a stable, almost perfectly circular orbit becoming the planet Venus which he claimed never existed until then." "Now, these ideas are almost certainly wrong." "There's no objection in astronomy to collisions." "We've seen collision fragments and evidence throughout the solar system." "The problem is with recent and major collisions." "In any scale model like this it's impossible to have both the sizes of the planets and the sizes of their orbits to the same scale because then the planets would be too small to see." "If the planets were really to scale in such a model as grains of dust it would then be entirely clear that a comet entering the inner solar system would have a negligible chance of colliding with a planet in only a few thousand years." "Moreover Venus is a rocky and metallic hydrogen-poor world whereas Jupiter, where Velikovsky imagines it comes from is made of almost nothing but hydrogen." "There is no energy source in Jupiter to eject planets or comets." "If one did enter the inner solar system there is no way it could stop the Earth from rotating." "And if it could, there's no way Earth could start rotating again at anything like 24 hours a day." "There's no geological evidence for flooding and volcanism 3500 years ago." "Babylonian astronomers observed Venus in its present stable orbit before Velikovsky said it existed." "And so on." "There are many hypotheses in science which are wrong." "That's all right." "It's the aperture to finding out what's right." "Science is a self-correcting process." "To be accepted, new ideas must survive the most rigorous standards of evidence and scrutiny." "The worst aspect of the Velikovsky affair is not that many of his ideas were wrong or silly or in gross contradiction to the facts." "Rather, the worst aspect is that some scientists attempted to suppress Velikovsky's ideas." "The suppression of uncomfortable ideas may be common in religion or in politics, but it is not the path to knowledge." "And there's no place for it in the endeavor of science." "We do not know beforehand where fundamental insights will arise from about our mysterious and lovely solar system." "And the history of our study of the solar system shows clearly that accepted and conventional ideas are often wrong and that fundamental insights can arise from the most unexpected sources." "We've evolved on the planet Earth and so we find it a congenial place." "But just next door is Venus until recently, enveloped in mystery." "It has almost the same size and mass as the Earth." "Might our sister world be a balmy summer planet a little warmer than the Earth because it's closer to the sun?" "Are there craters, volcanoes, mountains, oceans, life?" "The first to look at Venus through a telescope was Galileo in 1609." "But all he could see was a featureless disk." "As optical telescopes got bigger, that's all anybody could see:" "A disk with no details on it at all." "Venus evidently was covered with an opaque layer thick clouds concealing the surface." "For centuries, even the composition of the clouds of Venus was unknown." "I mean, you could go outside, look up, see Venus with the naked eye observe sunlight reflected from the clouds of Venus." "What were you looking at?" "What were the clouds made of?" "Nobody knew." "As a result, imagination ran riot." "The absence of anything you could see on Venus led some scientists and others to deduce that the surface was a swamp." "The argument, if we can dignify it with such a phrase went like this:" ""I can't see a thing on the surface of Venus."" ""Why not?"" ""Because it's covered with a dense layer of clouds."" ""What are clouds made of?"" ""Water, of course." "Therefore, Venus must have a lot of water on it."" ""Then the surface must be wet."" ""If the surface is wet, it's probably a swamp." "If there's a swamp, there's ferns." "If there's ferns maybe there's even dinosaurs."" "Observation:" "You couldn't see a thing." "Conclusion: dinosaurs." "If just looking at Venus was so unproductive what else could you do?" "The next clue came from early work with that:" "A glass prism." "An intense beam of ordinary white light is passed through a narrow slit and then through the prism." "The result is to spread the white light out into its constituent rainbow of colors." "This rainbow pattern is called a spectrum." "Think about it." "White light enters the prism what comes out of the prism is colored light." "Lots of colors." "Where did they come from?" "They must've been hiding in the white light." "White light must be a mixture of many colors." "Here we see the spectrum running from violet, blue, green, yellow, orange, to red." "Since we see these colors, we call this the spectrum of visible light." "The sun emits lots of visible light." "The air is transparent to it." "So our eyes evolved to work in visible light." "But there are many other frequencies of light which our eyes can't detect." "Beyond the violet is the ultraviolet." "It's just as real, but you need instruments to detect it." "Beyond the ultraviolet are the x-rays and then the gamma rays." "On the other side of visible light, beyond the red is the infrared, again real, again invisible." "Beyond the infrared are the radio waves." "Now, this entire range from the gamma rays way over there to the radio waves all the way over here are simply different kinds of light." "They differ only in the frequency." "They're all useful, by the way, in astronomy." "But because of the limitations of our eyes we have a prejudice, a bias, a chauvinism to this tiny rainbow band of visible light." "Now, a spectrum can be used in a simple and elegant way to determine the chemical composition of the atmosphere of a planet or star." "Different atoms and molecules absorb different frequencies or colors of light." "And those absorbed or missing frequencies appear as black lines in the spectrum of the light we receive from the planet or star." "Each and every substance has a characteristic fingerprint a spectral signature which permits it to be detected over a great distance." "As a result, the gases in the atmosphere of Venus at a distance of 60 million kilometers their composition's been determined from the Earth." "It's amazing to me still, we can tell what a thing is made out of at an enormous distance away, without ever touching it." "Our eyes can't see in the near infrared part of the spectrum." "But our instruments can." "Here's the absorption pattern of lots and lots of carbon dioxide:" "Dark lines in characteristic patterns at specific frequencies." "You'd detect a different set of infrared lines if, say, water vapor were present." "If Venus were really soaking wet, then you could determine that by finding the pattern of water vapor in its atmosphere." "But around 1 920, when this experiment was first performed the Venus atmosphere seemed to have not a hint not a smidgen, not a trace of water vapor above the clouds." "And so instead of a swampy, soaking wet surface it was suggested that Venus was bone-dry, a desert planet with clouds composed of fine silicate dust." "But later, spectroscopic observations revealed the characteristic absorption lines of an enormous amount of carbon dioxide." "Scientists thought there must be lots of carbon compounds on the surface making this a planet covered with petroleum." "Others agreed that the atmosphere was dry but thought the surface was wet." "With all that CO 2, it had to be carbonated water." "Venus, they thought, was covered with a vast ocean of seltzer." "The first hint of the true situation on Venus came not from the visible, ultraviolet or infrared part of the spectrum but from over here in the radio region." "We're used to the idea of radio signals from intelligent life or at least semi-intelligent life, radio and television stations." "But there are all kinds of reasons why natural objects emit radio waves." "One reason is that they're hot." "And when, in 1 956 Venus was, for the first time, observed by a radio telescope the planet was discovered to be emitting radio waves as if it were at an extremely high temperature." "But the real demonstration that Venus' surface was astonishingly hot came when the first spacecraft penetrated the clouds of Venus and slowly settled on the surface of the nearest planet." "These were the unmanned spacecraft of the Soviet Venera series." "In our spaceship of the imagination, we retrace their course." "From a distance, our sister planet seems serene and peaceful its clouds motionless." "These clouds are near the top of a great ocean of air about 100 kilometers thick, composed mainly of carbon dioxide." "There's some nitrogen, a little water vapor and other gases but only the merest trace of hydrocarbons." "The clouds turn out to be, not water but a concentrated solution of sulfuric acid." "Even in the high clouds Venus is a thoroughly nasty place." "The clouds are stained yellow by sulfur." "There are great lightning storms." "As we descend, there are increasing amounts of the noxious gas sulfur dioxide." "The pressures become so high that early Venera spacecraft were crushed like old tin cans by the weight of the surrounding atmosphere." "Beneath the clouds in the dense, clear air it's as bright as on an overcast day on Earth." "But the atmosphere is so thick that the ground seems to ripple and distort." "The atmospheric pressure down here is 90 times that on Earth." "The temperature is 380 degrees centigrade, 900 degrees Fahrenheit." "Hotter than the hottest household oven." "This is a world marked by searing heat crushing pressures, sulfurous gases and a desolate, reddish landscape." "Far from the balmy paradise imagined by some early scientists Venus is the one place in the solar system most like hell." "But today, as in ancient tradition there are travelers who will dare a visit to the underworld." "Venera 9 was the first spacecraft in human history to return a photograph from the surface of Venus." "It found the rocks curiously eroded perhaps by the corrosive gases perhaps because the temperature is so high that the rocks are partly molten and sluggishly flow." "The Soviet Venera spacecraft, their electronics long ago fried are slowly corroding on the surface of Venus." "They are the first spaceships from Earth ever to land on another planet." "The reason Venus is like hell seems to be what's called the greenhouse effect." "Ordinary visible sunlight penetrates the clouds and heats the surface." "But the dense atmosphere blankets the surface and prevents it from cooling off to space." "An atmosphere 90 times as dense as ours made of carbon dioxide, water vapor and other gases lets in visible light from the sun but will not let out the infrared light radiated by the surface." "The temperature rises until the infrared radiation trickling out to space just balances the sunlight reaching the surface." "The greenhouse effect can make an Earth-like world into a planetary inferno." "In this caldron, there's not likely to be anything alive even creatures very different from us." "Organic and other conceivable biological molecules would simply fall to pieces." "The hell of Venus is in stark contrast with the comparative heaven of its neighboring world our little planetary home, the Earth." "Here, the atmosphere is 90 times thinner." "Here, the carbon dioxide and water vapor make a modest greenhouse effect which heats the ground above the freezing point of water." "Without it, our oceans would be frozen solid." "A little greenhouse effect is a good thing." "But Venus is an ominous reminder that on a world rather like the Earth things can go wrong." "There is no guarantee that our planet will always be so hospitable." "To maintain this clement world we must understand it and appreciate it." "The Earth is a place to our eyes more beautiful than any other that we know." "But this beauty has been sculpted by change:" "Gentle, almost undetectable change and sudden, violent change." "In the cosmos, there is no refuge from change." "The Sphinx:" "human head, lion's body constructed more than 5500 years ago." "That face was once crisp and cleanly rendered like this paw I am standing on." "The paw has been buried in the sand until recently and protected from erosion." "The face is now muddled and softened because of thousands of years of sandblasting in the desert and a little rainfall." "In New York City, there is an obelisk called Cleopatra's Needle which comes from Egypt." "In only a little more than a century in New York's Central Park the inscriptions on that obelisk have been almost totally obliterated." "Not by sand and water but by smog and industrial pollution." "A bit like the atmosphere of Venus." "Slow erosion wipes out information." "On the Earth mountain ranges are destroyed by erosion in maybe tens of millions of years small impact craters in maybe hundreds of thousands of years." "And the greatest artifacts of human beings in thousands or tens of thousands of years." "In addition to such slow and uniform processes there are rare but sudden catastrophes." "The Sphinx is missing a nose." "In an act of idle desecration, some soldiers once shot it off." "If you wait long enough, everything changes." "Slow, uniform processes, unheralded events:" "The sting of a sand grain the fall of a drop of water can, over the ages, totally rework the landscape." "And rare, violent processes exceptional events that will not recur in a lifetime also make major changes." "Both the insignificant and the extraordinary are the architects of the natural world." "The destruction of trees and grasslands makes the surface of the Earth brighter." "It reflects more sunlight back to space and cools our planet." "After we discovered fire we began to incinerate forests intentionally to clear the land by a process called "slash and burn" agriculture." "And today, forests and grasslands are being destroyed frivolously, carelessly by humans who are heedless of the beauty of our cousins the trees and ignorant of the possible climatic catastrophes which large-scale burning of forests may bring." "(TREES BREAKING)" "The indiscriminate destruction of vegetation may alter the global climate in ways that no scientist can yet predict." "It has already deadened large patches of the Earth's life-supporting skin." "And yet, we ravage the Earth at an accelerated pace as if it belonged to this one generation as if it were ours to do with as we please." "The Earth has mechanisms to cleanse itself to neutralize the toxic substances in its system." "But these mechanisms work only up to a point." "Beyond some critical threshold, they break down." "The damage becomes irreversible." "Our generation must choose." "Which do we value more:" "short-term profits or the long-term habitability of our planetary home?" "The world is divided politically." "But ecologically it is tightly interwoven." "There are no useless threads in the fabric of the ecosystem." "If you cut any one of them, you will unravel many others." "We have uncovered other worlds with choking atmospheres and deadly surfaces." "Shall we then re-create these hells on Earth?" "We have encountered desolate moons and barren asteroids." "Shall we then scar and crater this blue-green world in their likeness?" "Natural catastrophes are rare." "But they come often enough." "We need not force the hand of nature." "If we ruin the Earth, there is no place else to go." "This is not a disposable world." "And we are not yet able to re-engineer other planets." "The cruelest desert on Earth is far more hospitable than any place on Mars." "The bright, sandy surface and dusty atmosphere of Mars reflect enough sunlight back to space to cool the planet freezing out all its water, locking it in a perpetual ice age." "Human activities brighten our landscape and our atmosphere." "Might this ultimately make an ice age here?" "At the same time, we are releasing vast quantities of carbon dioxide increasing the greenhouse effect." "The Earth need not resemble Venus very closely for it to become barren and lifeless." "It may not take much to destabilize the Earth's climate to convert this heaven, our only home in the cosmos into a kind of hell." "The study of the global climate, the sun's influence the comparison of the Earth with other worlds..." "These are subjects in their earliest stages of development." "They are funded poorly and grudgingly." "Meanwhile, we continue to load the Earth's atmosphere with materials about whose long-term influence we are almost entirely ignorant." "There are worlds that began with as much apparent promise as Earth." "But something went wrong." "Knowing that worlds can die alerts us to our danger." "If a visitor arrived from another world, what account would we give of our stewardship of the planet Earth?" "In the history of the solar system, have worlds ever been destroyed?" "Most of the moons in the outer solar system have craters on them made by cometary impacts." "Some have such large craters though that if the impacting comets had been just a little bit bigger the moons would have been shattered." "What would the results of such a collision look like?" "(EXPLOSION)" "Maybe a planetary ring." "The idea has been growing that little worlds are every now and then, demolished by a cometary impact." "The fragments then slowly coalesce, and a moon arises again from its own ashes." "Some moons may have been destroyed and reconstituted many times." "For our own world, the peril is more subtle." "Since this series was first broadcast the dangers of the increasing greenhouse effect have become much more clear." "We burn fossil fuels, like coal and gas and petroleum putting more carbon dioxide into the atmosphere and thereby heating the Earth." "The hellish conditions on Venus are a reminder that this is serious business." "Computer models that successfully explain the climates of other planets predict the deaths of forests parched croplands, the flooding of coastal cities environmental refugees widespread disasters in the next century unless we change our ways." "What do we have to do?" "Four things." "One: much more efficient use of fossil fuels." "Why not cars that get 70 miles a gallon instead of 25?" "Two: research and development on safe alternative energy sources especially solar power." "Three: reforestation on a grand scale." "And four: helping to bring the billion poorest people on the planet to self-sufficiency which is the key step in curbing world population growth." "Every one of these steps makes sense apart from greenhouse warming." "No one has proposed that the trouble with Venus is that there once was Venusians who drove fuel-inefficient cars." "But our nearest neighbor, nevertheless, is a stark warning on the possible fate of an Earth-like world." "Recent studies suggest that a piece of a rocky asteroid exploded high in the atmosphere." "The comet Encke hypothesis has been abandoned." "The object was probably a piece of an asteroid a rocky mass some 200 feet (60 meters) across and weighing half a million tons." "The rocky asteroid mass exploded and was pulverized high in the atmosphere." "This produced a fireball and a blast wave in the air but no crater in the ground." "There are now thought to be a few trillion long-period comets in the Oort Cloud, which extends about halfway to the nearest star." "Computer simulations show that this mechanism cannot account for the observed number of short-period comets." "The short-period comets probably come from the newly found Kuiper Belt of comets orbiting just beyond the orbit of Neptune." "The fragments of a comet, called Shoemaker-Levy 9, actually did plunge into Jupiter in 1 994." "They produced enormous fireballs and stained the atmosphere with dark clouds that lasted for weeks." "The latest theory of lunar origin assumes that a Mars-sized planet collided with the young Earth." "Some of the debris ejected out from the impact formed an orbiting ring around the Earth from which the Moon formed."