"SAGAN:" "Martians." "Why so many speculations and fantasies about Martians rather than Saturnians, say, or Plutonians?" "Because Mars seems, at first glance, very Earth-like." "It's the nearest planet whose surface we can see." "There are polar icecaps, drifting white clouds raging dust storms, seasonally changing patterns even a 24-hour day." "It's tempting to think of it as an inhabited world." "Mars has become a kind of mythic arena onto which we've projected our earthly hopes and fears." "The most tantalizing myths about Mars have proved wrong." "So a few people have swung to the opposite extreme and concluded that the planet is of little interest." "They've begun to sing blues for the Red Planet." "But the real Mars is a world of wonders." "Its future prospects are far more intriguing than our past apprehensions about it." "In our time, we have sifted the sands of Mars established a presence there and fulfilled a century of dreams." "The most startling dream of Mars was that of H.G. Wells who in 1897 wrote The War of the Worlds." "NARRATOR: "No one would have believed in the end of the 19th century that this world was being watched keenly and closely by intelligences greater than man's and yet as mortal as his own." "As men busied themselves about their various concerns they were scrutinized and studied perhaps almost as narrowly as a man with a microscope might scrutinize the transient creatures that swarm and multiply in a drop of water." "With infinite complacency, men went to and fro over this globe about their little affairs serene in their assurance of their empire over matter." "It's possible that the infusoria under the microscope do the same." "(CHILDREN SINGING)" "No one thought of the older worlds of space as sources of human danger or thought of them only to dismiss the idea of life upon them as impossible or improbable." "(CLAPPING)" "It is curious to recall some of the mental habits of those departed days." "At most, terrestrial men fancied there might be other men upon Mars, perhaps inferior to themselves and ready to welcome a missionary enterprise." "Yet across the gulf of space intellects vast and cool and unsympathetic regarded this Earth with envious eyes and slowly and surely drew their plans against us."" "(CHEERING)" "SAGAN:" "Wells' novel captured the popular imagination in the late Victorian era." "This was a time when the automobile was a novelty when the pace of life was still determined by the speed of the horse." "Into this world, Wells introduced an interplanetary fantasy with spaceships, ray guns and implacable aliens." "These were original and disquieting possibilities." "The Martians of H.G. Wells were not merely minor variations on a human theme." "Instead, they were the evolutionary product of a totally alien environment." "Forty years later, this fantasy was still able to frighten millions in war-jittery America when it was dramatized for radio by the young Orson Welles." "A few years before The War of the Worlds was published another, quite different vision of Martians was forming in the mind of a wealthy Bostonian named Percival Lowell." "The Martians of H.G. Wells were a way for the novelist to examine contemporary society through alien eyes." "But the Martians of Percival Lowell were, he believed very real." "It was here that the most elaborate claims in support of life on Mars were developed." "Lowell dabbled in astronomy as a young man." "He went off to Harvard." "He had a semiofficial diplomatic appointment to Korea and otherwise engaged in the usual pursuits of the wealthy for his time." "But his lifelong love was the planet Mars." "Lowell was electrified by the announcement in 1877 by an Italian astronomer, Giovanni Schiaparelli of canali on Mars." "Schiaparelli had reported during a close approach of Mars to the Earth an intricate network of single and double straight lines crisscrossing the bright areas of Mars." "Now, canali in Italian means "channels" or "grooves" but it was promptly translated into English as canals a word which understandably has a certain implication of intelligent design." "A Mars-mania swept through Europe and America and Percival Lowell found himself caught up in it." "In 1892, his eyesight failing Schiaparelli announced he was giving up observing Mars." "Lowell resolved to continue the work." "(ROOF CREAKS)" "He wanted a first-rate observing site undisturbed by clouds or city lights and marked by good seeing." ""Seeing" is the astronomer's term for a steady atmosphere through which the shimmering of an astronomical image in the telescope is minimized." "Lowell built his observatory far away from home on Mars Hill, here in Flagstaff, Arizona." "Lowell sketched the surface features of Mars and particularly the canals, which mesmerized him." "Now, observations of this sort aren't easy." "You put in long hours at the telescope in the chill of the early morning." "Most of the time, the seeing is crummy." "When the seeing is bad the image of Mars blurs and distorts and you have to ignore what you've observed." "But occasionally the image steadies and the features of the planet marvelously flash out at you." "You must then remember what you've seen and accurately commit it to paper." "You must put your preconceptions aside and with an open mind, set down the wonders that Mars holds in store for us." "This is Percival Lowell's own notebook." "Here's what he thought he saw." "Bright and dark areas, a hint of a polar cap and canals." "Lots and lots of canals." "Lowell believed that he was seeing a globe-girdling network of great irrigation canals carrying water from the melting polar caps to the thirsty inhabitants of the equatorial cities." "He believed the planet was inhabited by an older and wiser race perhaps very different from us." "He believed that the seasonal changes in the dark areas were due to the growth and decay of vegetation." "He believed that the planet was Earth-like." "All in all, he believed too much." "Lowell's Martians were a dying race." "Their once-great cities had fallen into ruins." "Lowell believed that the Martian climate was changing that the precious water was trickling away into space that the planet was becoming a desert world." "The canals, he thought, were a last desperate measure a heroic engineering effort to conserve the scarce water." "But their technology, although far more advanced than ours was inadequate to stem a planetary catastrophe." "The most serious contemporary challenge to Lowell's ideas came from an unlikely source:" "The biologist Alfred Russel Wallace co-discoverer of evolution by natural selection." "Wallace correctly showed that the air on Mars was much too cold and thin to permit the existence of liquid water." "He wrote that "only a race of madmen would build canals under such conditions."" "Lowell's Martians were benign and hopeful even a little godlike very different from the malevolent menace posed by H.G. Wells and Orson Welles in The War of the Worlds." "Both sets of ideas passed into the public imagination through Sunday supplements and science fiction and excited generations of 8-year-olds into fantasizing that they themselves might one day voyage to the distant planet Mars." "I remember reading with breathless fascination the Mars novels of Edgar Rice Burroughs." "I journeyed with John Carter gentleman adventurer from Virginia to Barsoom, as Mars was known by its inhabitants." "Wandering among the beasts of burden called thoats winning the hand of the lovely Dejah Thoris Princess of Helium and befriending a 10-foot-high green fighting man named Tars Tarkas as the moons of Mars hurtled overhead on a summer's evening on Barsoom." "It aroused generations of 8-year-olds myself among them to consider the exploration of the planets as a real possibility to wonder whether we ourselves might one day venture to the distant planet Mars." "John Carter got to Barsoom by standing in an open field spreading his hands and wishing hard at Mars." "I can remember spending many an hour in my boyhood arms resolutely outstretched in an open field in twilight imploring what I believed to be Mars to transport me there." "It never worked." "There had to be some better way." "And there was." "The real road to Mars was opened by a boy who loved skyrockets." "(BAND PLAYS)" "Fourth of July celebrations in New England are much the same today as they were in the 1890s." "Then, as now, the highlight of the day's festivities was a rousing fireworks display." "That was the part that Robert Goddard liked the best." "By the time he was 16, he was launching his own rockets." "He wrote in his diary:" ""July 4, 1898:" "Fired cannon and firecrackers all day." "In evening, had five rockets."" " You gonna light it now?" " Yes, I am." "Wow!" "That same year The War of the Worlds was being serialized in the Boston Post." "Goddard eagerly read every word." "The Boston newspapers were also reporting intriguing conjectures by a Professor Lowell whose lectures Goddard would later attend." "The images of Mars spun by Wells and Lowell beguiled the young Goddard and at age 17 on October 19, 1899 they crystallized into an overwhelming vision that provided the direction and purpose of his life." "From the high branches of an old cherry tree on his family's farm Goddard saw a way to do more than just speculate about Mars." "Before anyone had ever flown in an airplane or listened to a radio Goddard decided to invent a machine that would voyage to the planet Mars." "For the rest of his life, he was to commemorate that October day as his anniversary day the birthday of his great dream." "By the 1920s, after years of studying physics and engineering he was experimenting with liquid fuel rockets." "In order to build a rocket capable of reaching high altitudes Goddard had to create the principles of an entirely new technology." "He invented the basic components that propel, stabilize and guide the modern rocket." "It was painstaking and difficult work." "But Goddard took the many setbacks in stride." "He sifted the wreckage of each experiment for clues to guide the next." "Constantly refining old techniques and inventing new ones he gradually raised the rocket from a dangerous toy and set it on its way to becoming an interplanetary vehicle." "Goddard died in 1945 before a rocket had ever left the planet Earth." "Although Mars always remained his objective Goddard knew that such a goal would be ridiculed." "In public he advocated the more modest objective of flying to the moon." "Those boyhood dreams of voyages to the moon and Mars shared by Goddard with his contemporary a Russian scientist named Konstantin Tsiolkovsky were fulfilled only a few decades after their deaths." "But as it turned out, the first planet to be explored by rocket was the Earth." "Now, imagine yourself a visitor from some other and quite alien planet." "You approach the Earth with no preconceptions." "Is the place inhabited?" "At what point can you decide?" "When we look at the whole Earth, there are no signs of life." "We must examine it more closely." "If there are intelligent beings, maybe they create structures which can be seen at a resolution of a few kilometers." "Yet at this level of detail even a great river valley seems utterly lifeless." "There is no sign of life intelligent or otherwise in Washington, D. C or Moscow or Tokyo or Peking." "If there are intelligent beings, they have not much modified the landscape into geometrical patterns at kilometer resolution." "But when we improve the resolution tenfold when we see detail as small as 100 meters across the size of a football field the situation changes." "Many places on Earth seem suddenly to crystallize out revealing an intricate pattern of straight lines squares, rectangles and circles." "Canals, roads, circular irrigation patterns all suggest intelligent life with a passion for Euclidean geometry and territoriality." "On this scale, intelligent life can be discerned." "Boston and Washington and New York." "At 10-meter resolution, we also discover that the Earthlings like to build up." "At twilight or night, other things are visible:" "Oil well fires in the Persian Gulf or the bright lights of large cities." "At a meter resolution, we make out individual organisms:" "Seals on ice floes or people on skis." "Intelligent life on Earth first reveals itself through the geometric regularity of its constructions." "If Lowell's canal network existed, the conclusion that intelligent beings inhabit that planet might be compelling." "But there is no canal network." "Our unmanned spacecraft have examined Mars with 1000 times more detail than any fleeting glimpse available through Percival Lowell's telescope." "There is no question that his Martian canals were of intelligent origin." "The only question was which side of the telescope the intelligence was on." "Where we have strong emotions, we are liable to fool ourselves." "Yet even without the canals, the exploration of Mars evokes the kind of rapture that Columbus or Marco Polo must have felt." "We see many impact craters but we find no canals." "None at all." "There are fault lines in the surface and complex patterns of ridges and valleys but they're all far too small and in the wrong places to be Lowell's canals." "And they don't seem to be manufactured." "There are many signs of water." "Ancient river valleys wind their way among the craters." "Nergal Valley, named after the Babylonian war god is 1000 kilometers long and a billion years old." "There seems to have been a time when Mars was warmer and wetter than it is today." "I wonder if life ever arose in the muddy backwaters of these great river systems." "The waters flowed at the same time that the great volcanoes of the Tharsis Plateau were made." "Before the present continents of Earth were formed it was a very lively epoch on Mars." "Equally old is the Mariner Valley a strange, vast, mist-filled chasm." "If it were on Earth, it would stretch from New York to Los Angeles." "Landslides and avalanches are slowly eroding its walls which collapse to the floor of the valley." "There, the winds remove the particles and create immense sand dune fields." "Signs of high winds are all over Mars." "Often craters have, trailing behind them long streaks of bright or dark material, blown out by the winds natural weathervanes on the Martian surface." "For the sand to be blown about in the thin Martian atmosphere the winds have to be fast sometimes approaching half the speed of sound." "But some of the patterns are so odd and intricate that we cannot be sure they're caused by windblown sand." "And there are other strange markings:" "Furrowed ground, almost resembling a giant plowed field a billion years old and one of the strangest features on Mars the pyramids of Elysium 10 times taller than the pyramids of Egypt." "Perhaps they're only mountains sculpted by the fierce winds but perhaps they're something else." "How marvelous it would be to glide over the surface of Mars to fly over Olympus Mons the largest known volcano in the solar system." "The surface area of Mars is exactly as large as the land area of the Earth." "It will be a long time before this planet is thoroughly explored." "The only canal of Percival Lowell that corresponds to anything real is Mariner Valley." "5000 kilometers long it's a little hard to miss even from Earth." "The Grand Canyon of Arizona would fit into one of its minor tributaries." "Someday we will careen through the corridors of the Valley of the Mariners." "To skim over the sand dunes of Mars is as yet, only a dream." "But we have, in fact sent robot emissaries to Mars." "Their names are Viking 1 and Viking 2." "The problem was where to land them." "We knew that the volcanoes of Tharsis were too high." "The thin Martian atmosphere would not support our descent parachute." "The great Mariner Valley was too rough and unpredictable." "The polar caps were too cold for the lander's nuclear power plant to keep it warm." "There were fascinating places that were too high or too windy or too hard or too soft or too rough or too cold." "We worried about the safety of every landing site." "Perhaps we were too cautious." "Eventually we selected two places." "One, optimistically named Utopia for Viking 2 and another, 8000 kilometers away not far from the confluents of four great channels a landing site for Viking 1 called Chryse Greek for "the land of gold."" "And so, after a voyage of 100 million kilometers on July 20, 1976 Viking 1 landed right on target in the Chryse Plain." "It was less than 80 years since Robert Goddard had his epiphanic vision in a cherry tree in Massachusetts." "After hibernating for a year during its interplanetary passage Viking reawakened on another world." "The first thing it did was to call home reporting a safe arrival." "It began to rouse itself according to instructions memorized earlier." "First, it put out a finger to test the Martian winds." "Then, flexing its arm it flung off a protective glove." "Next, Viking prepared to sniff the air and taste the soil." "Finally it opened its eyes for a look at its new surroundings." "(WHIRRING)" "Viking's first picture assignment was to photograph its own foot." "In case it were to sink into Martian quicksand we wanted to know about it before it disappeared." "Back on Earth, we waited breathlessly for the first images." "Viking painted its picture in vertical strokes, line by line until, with enormous relief, we saw the footpad securely planted in the Martian soil." "This was the first image ever returned from the surface of Mars." "The cameras on each Viking lander revealed a kind of rocky desert." "Beyond the lander itself we saw for the first time the landscape of the Red Planet." "It didn't look like an alien world." "There were rocks and sand dunes and gently rolling hills as natural and familiar as any landscape on Earth." "Forever after, Mars would be a place." "We found that the Martian air was less than 1% as dense as ours and made mostly of carbon dioxide." "There were smaller amounts of nitrogen, argon water vapor and oxygen." "There was almost no ozone." "So the surface wasn't protected from the sun's ultraviolet light as it is on Earth." "On the warmest days, it was distinctly chilly and every night the temperatures plunged to 100 below." "In winter, the surface was dusted with a thin layer of frost." "The landing sites were chosen because they were safe and flat." "Even so, Viking revolutionized our knowledge of this rusty world." "I would, of course, have been surprised to see a grizzled prospector emerge from behind a dune leading his mule." "Yet the idea seemed strangely appropriate." "But at least while we were watching no prospector wandered by." "We studied with exceptional care each picture the cameras radioed back." "But there was no hint of the canals of Barsoom no sultry princesses no 10-foot-tall green fighting men no thoats, no footprints not even a cactus or a kangaroo rat." "Perhaps there was life inside the rocks or under the ground." "If so, it had left no traces." "For most of its history, the Earth had microbes but no living things big enough to see." "Perhaps the same is true for Mars." "The Viking lander is a superbly instrumented and designed machine." "It extends human capabilities to other and alien landscapes." "By some standards, it's about as smart as a grasshopper." "By others, only as intelligent as a bacterium." "There's nothing demeaning in these comparisons." "It took nature hundreds of millions of years to evolve a bacterium and billions of years to make a grasshopper." "With only a little experience in this business we're getting pretty good at it." "In both landing sites in Chryse and Utopia we've begun to dig in the sands of Mars." "On a very small scale, such trenches are the first human engineering works on another world." "The robot arm retrieves soil samples and deposits them into several sifters." "Then the soil is carried to five experiments:" "Two on the chemistry of the soil and three to look for microbial life." "The Viking biology experiments represent a pioneering first effort in the search for life on another world." "The results are tantalizing, annoying provocative, stimulating and deeply ambiguous." "By criteria established before a launch two of the three Viking microbiology experiments seem to have yielded positive results." "First, when Martian soil samples are mixed together with an organic soup from Earth something in the soil seems to have broken food down almost as if there were little Martian microbes which metabolized, enjoyed the soup from Earth." "Second, when gases from Earth were mixed together with Martian soil something seems to have chemically combined the gases with soil almost as if there were little Martian microbes capable of synthesizing organic matter from atmospheric gases." "But the situation is complex." "Mars is not the Earth." "As the legacy of Percival Lowell reminds us, we're liable to be fooled." "Perhaps the ultraviolet light from the sun strikes the Martian surface and makes some chemical which can oxidize foodstuffs." "Perhaps there is some catalyst in the soil which can combine atmospheric gases with the soil and make organic molecules." "The red sands of Mars were excavated seven times at the two different landing sites as distant from each other as Boston is from Baghdad." "Whatever was giving these results was probably all over Mars but was it life, or just the chemistry of the soil?" "Studies suggest that a kind of clay known to exist on Mars can serve as a catalyst to accelerate in the absence of life chemical reactions which resemble the activities of life." "It may be that in the early history of the Earth, before life there were little cycles, chemical cycles running in the soil something like photosynthesis and respiration which were then incorporated by biology once life arose." "There may be life elsewhere than in the two small sites we examined." "Or perhaps there's life of a different sort all over Mars." "Life is just a kind of chemistry of sufficient complexity to permit reproduction and evolution." "I wonder if we'll ever find a specimen of life based not on organic molecules but on something else, something more exotic." "The Viking experiments found that the Martian soil is not loaded with organic remains of once living creatures." "Maybe the surface's reactive chemistry has destroyed organic molecules molecules based on carbon." "Or maybe there's no life on Mars and all Viking found was a funny soil chemistry." "Or maybe there's life, okay but it's not based on organic chemistry as much as life is on Earth." "Personally, I don't think that's a very likely possibility." "I'm a carbon chauvinist." "I freely admit it." "Carbon is tremendously abundant in the cosmos and it makes marvelously complex organic molecules that are terrifically good for life." "I'm also a water chauvinist." "It's an ideal solvent for organic molecules and it stays liquid over a very wide range of temperatures." "But sometimes I wonder, could my fondness for these materials have anything to do with the fact that I'm chiefly made up of them?" "Are we carbon and water-based because these materials were abundant on the Earth at the time of the origin of life?" "Might life elsewhere be based on different stuff?" "(LIQUID GURGLES)" "I'm a collection of organic molecules called Carl Sagan." "You're a collection of almost identical molecules with a different collective label." "But is that all?" "Is there nothing in here but molecules?" "Some people find that idea somehow demeaning to human dignity." "But for myself, I find it elevating and exhilarating to discover that we live in a universe which permits the evolution of molecular machines as intricate and subtle as we." "The essence of life is not the atoms and small molecules that go into us as the way, the ordering the way those molecules are put together." "Now, we sometimes read that the chemicals which make up a human body are worth on the open market, only 97 cents or $10, or some number like that." "And it's depressing to find our bodies valued at so little." "But these estimates are for humans reduced to our simplest possible components." "What is all this stuff in front of me?" "These are exactly the atoms that make up the human body and in the right proportions too." "We're made mostly of water, and that costs almost nothing." "The carbon is counted as coal." "The calcium in our bones is chalk." "The nitrogen in our proteins is liquid air." "The iron in our blood is rusty nails." "Some phosphorus and some trace elements." "If we didn't know better we might be tempted to take all these items and mix them together in a container like this." "And stir." "We could stir all we want and at the end, all we'd have is some boring mixture of atoms." "How could we expect anything else?" "The beauty of a living thing is not the atoms that go into it but the way those atoms are put together:" "Information distilled over 4 billion years of biological evolution." "Incidentally, all the organisms on the Earth are made essentially of that stuff." "An eyedropper full of that liquid could be used to make a caterpillar or a petunia if only we knew how to put the components together." "All life on Earth is made from the same mixture of the same atoms." "On another planet, the jars of life might be filled with very different atoms and small molecules." "But I think the life forms on many worlds will consist, by and large of the same atoms that are popular here maybe even the same big molecules." "So I don't believe we can rescue the idea of life on Mars by appealing to some exotic chemistry." "Sometimes we hear about possible life forms in which silicon replaces carbon or perhaps, liquid ammonia replaces liquid water." "But at Martian temperatures, there are no plausible silicon-based molecules which might carry a genetic code." "And ammonia is liquid only under higher pressures and lower temperatures." "Someday in the distant future we might have a collection of jars each containing the elementary biochemistry of another world." "I don't know if there'll be one labeled "Mars."" "But if there is I bet it will be full of organic molecules." "There's another way to search for life on Mars to seek out the discoveries and delights which that heterogeneous environment promises us." "One of the things that a grasshopper can do but Viking can't is move." "We landed in the dull places on Mars." "For all the solid, scientific findings and hints which Viking provided we know that there are many places on the planet far more interesting." "What we need is a roving vehicle with advanced experiments in biology and organic chemistry able to land in the safe but dull places and wander to the interesting places." "This roving vehicle was developed by the Rensselaer Polytechnic Institute." "It has a long list of dumb things it knows not to do." "A Mars rover hasn't got time to ask if it should attempt a steep slope." "Radio waves traveling at the speed of light take 20 minutes for the roundtrip to Earth." "By the time it got an answer, it might be a heap of twisted metal at the bottom of a canyon." "A rover has to think for itself." "Imagine a rover with laser eyes like this one but packed with sophisticated biological and chemical instruments sampler arms, microscopes and television cameras wandering over the Martian landscape." "It could drive to its own horizon every day." "A distant feature it barely resolves at sunrise it can be sniffing and tasting by nightfall." "Billions of people could watch the unfolding adventure on their TV sets as the rover explores the ancient river bottoms or cautiously approaches the enigmatic pyramids of Elysium." "A new age of discovery would have begun." "Most of the human species would witness the exploration of another world." "Only 80 years ago, we could come no closer to Mars than straining to see a tiny, shimmering image through a telescope in Arizona." "Now our instruments have actually touched down on the planet." "Viking is a legacy of H.G. Wells Percival Lowell, Robert Goddard." "Science is a collaborative enterprise spanning the generations." "When it permits us to see the far side of some new horizon we remember those who prepared the way seeing for them also." "On each lander, there is a microdot on which is written very small the names of 10,000 men and women responsible for Viking's splendid achievement." "One of the names on this microdot belonged to a friend of mine:" "A remarkable microbiologist named Wolf Vishniac." "He was the first person to build a machine to look for microbes on another world." "His friends called it the "Wolf Trap."" "It contained a liquid nutrient to which Martian soil would be added and any microbes that liked the food would grow in that nutrient medium and cloud it." "The Wolf Trap was selected to go with Viking to Mars but NASA is especially vulnerable to budget cuts and it was removed as an economy measure." "It was a terrible blow to Vishniac." "He'd worked 12 years on it." "Others might have stalked off the project but Vishniac was a gentle and dedicated man." "He decided instead to study the most Mars-like environment on this planet:" "The dry valleys of Antarctica, which were long thought to be lifeless." "But Vishniac believed that if he could find microbes growing in these arid polar wastes the chances of life on Mars would improve." "So in November 1973 Vishniac was left in a remote valley in the Asgard Mountains of Antarctica." "He set up hundreds of little sample collectors simple versions of the Viking microbiology experiments." "On December 10th he left camp to retrieve some samples and never returned." "He had wandered to an unexplored area apparently slipped on the ice and fell more than 100 meters." "Maybe something had caught his eye a likely habitat for microbes or a patch of green where none should be." "The last entry in his notebook was:" ""Station 202 retrieved." "2230 hours." "Soil temperature, minus 10 degrees." "Air temperature, minus 16 degrees."" "It had been a typical summer temperature for Mars." "Some of his soil samples were later returned and his colleagues discovered that there is life in the dry valleys of Antarctica that life is even more tenacious than we had imagined." "That fact may turn out to be important for the future history of Mars." "There will be a time when Mars is thoroughly explored." "What then?" "What should we do with Mars?" "If there is life on Mars, then I believe we should do nothing to disturb that life." "Mars, then, belongs to the Martians, even if they are microbes." "But suppose that Mars is in fact lifeless." "Might we in some sense be able to live there to somehow make Mars habitable like the Earth to terraform another world?" "As lovely a world as Mars is it poses certain problems." "There's too little oxygen, no liquid water and too much ultraviolet light." "But all that could be solved if we could make more air." "With higher atmospheric pressures, liquid water would become possible." "With more oxygen we could breathe the atmosphere." "And ozone could form to shield the surface from the solar ultraviolet light." "The evidence for liquid water suggests that Mars once had a denser atmosphere which can't have all escaped to space." "It has to be on the planet somewhere." "In subsurface ice, surely but most accessibly in the present polar caps." "To vaporize the icecaps, we must heat them preferably by covering them with something dark to absorb more sunlight." "That thing ought to also be cheap and able to make copies of itself." "Well, there are such things." "We call them plants." "We would need to evolve by artificial selection and genetic engineering dark plants able to survive the severe Martian environment." "Such plants could be seeded on the vast expanse of the Martian polar icecaps taking root, spreading, giving off oxygen darkening the surface, melting the ice and releasing the ancient Martian atmosphere from its long captivity." "We might even imagine a kind of Martian Johnny Appleseed robot or human roaming the frozen polar wastes in an endeavor which benefits only the generations to come." "It might take hundreds or thousands of years." "We might, then, want to carry the liberated water from the melting polar icecaps to the warmer equatorial regions." "And there's a way to do it:" "We would build canals." "But that's exactly what Percival Lowell believed was happening on Mars in his time." "The idea of a canal network built by Martians may turn out to be a kind of premonition because, if the planet ever is terraformed it will be done by human beings whose permanent residence and planetary affiliation is Mars." "The Martians will be us." "Mars today is strictly relevant to the global environment of the Earth." "Its antiseptic surface is a cautionary tale of what happens if you don't have an ozone layer." "Its great dust storms and the resulting cooling of its surface played a role in the discovery of nuclear winter the catastrophic climate change on Earth predicted to follow nuclear war." "So if you didn't have an ounce of adventuresome spirit in you it would still make sense to support the exploration of Mars." "In recent years, there's been a groundswell of interest in organizing the first expedition of humans to go to the planet Mars." "We first need more robotic missions, including rovers balloons and return- sample missions and more experience in long duration space flight." "But eventually, if all goes well the interplanetary ship or ships would be constructed in Earth orbit launched on the long journey to Mars and then a landing module would set down on the surface." "The crew would emerge making the first human footfalls on another planet." "It would be very expensive, of course although cheaper if many nations share the cost." "The key issue in my mind is whether the unmet needs here on Earth should take priority." "But that's a question even more appropriately addressed to the military budgets now $1 trillion a year worldwide." "You can buy a lot for that." "Justifications for the Mars endeavor have been offered in terms of scientific exploration developing technology, international cooperation education, the environment." "Some see it as the obvious response to the future calling." "Some even think we should go to investigate enigmatic landforms including one that resembles an enormous human face." "Personally, I think this, like hundreds of other blocky mesas there is sculpted by the high-speed winds." "But if we're going anyway, there's no harm in taking a look." "A remarkably diverse group of American leaders has endorsed the Mars goal." "I imagine the emissaries from Earth citizens of many nations wandering down an ancient river valley on Mars trying to understand how a quite Earth-like world was converted into a permanent ice age and looking for signs of ancient life along the river banks." "In the long run the significance of such a mission is nothing less than the conversion of humanity into a multiplanet species." "Recent images from the orbiting Mars Global Surveyor spacecraft (June 2000) revealed gullies apparently eroded by water running on Mars in the geologically recent past." "In July 1 997, NASA deployed the first ever roving vehicle on Mars an experimental prototype called Sojourner." "The rover investigated Mars rocks in the vicinity of its base at the Pathfinder landing vehicle, renamed the Carl Sagan Memorial Station." "In April 1 998, the Mars Global Surveyor spacecraft took a detailed photograph of the so-called "Face on Mars." At high resolution all resemblance to a face vanished." "The blocky mesa looks geological." "SAGAN:" "Imagine that we are travelers from the stars bound for the sun." "We would discover it surrounded by four giant, cloudy, gas worlds:" "Blue Neptune and its frozen moon, Triton." "And then farther in, Uranus and its dark rings made perhaps of organic matter." "Saturn, the jewel of the solar system set within concentric rings..." "And finally, flanked by massive satellites the largest planet, Jupiter." "Its multicolored clouds studded with flashes of lightning." "Still farther in closer to the sun there are no more giant planets only a host of lesser worlds made of rock and metal some with a thin envelope of air." "They huddle about the sun with almost no internal heat of their own tiny places with solid surfaces one of which is a blue and pretty world called Earth." "Half-covered with clouds it is the home planet of travelers who have just learned to sail the sea of space to investigate close-up Jupiter, Saturn, Uranus and Neptune its brothers and sisters in the family of the sun." "Human voyages of exploration to the outer solar system are controlled, so far, from a single place on the planet Earth the Jet Propulsion Laboratory of the National Aeronautics and Space Administration in Pasadena, California." "Here on Sunday, July 8th, 1979 the Voyager 2 spacecraft began its close passage by Jupiter and its moons." "General science systems..." "JPL MAN:" "...are you ready with status check?" "Yes, I am." "SAGAN:" "The spacecraft had been instructed how to explore the Jupiter system by a sequence of commands radioed earlier to its onboard computers." "Power, 450 watts." "Power is go at this time." "DSE systems." "LACP mode is far and counter." "We are at take 21 0." "Direction last recorded was reversed, and the track is track one." "Here we check how faithful an emissary Voyager is." "Does it understand the commands?" "How is its health, its temperature its brains its heart?" "Yes, detailed science is coming up..." ""A" systems and the spacecraft is go." "Roger." "Thank you." "SAGAN:" "The modern ships that sail to the planets are unmanned." "They are beautifully constructed semi-intelligent robots." "Voyager's eyes are two television cameras designed to take many thousands of pictures in the solar system." "Along with other instruments, they are mounted on a scan platform which points at passing planets." "Voyager's brains are three integrated computers set amidships." "It communicates with Earth through a radio antenna mounted like a sail." "Voyager bears a message for any alien civilization it may one day encounter in interstellar space." "Its louvers open and shut to help control the onboard temperature." "But Voyager cruises so far from the sun that it cannot depend on solar power." "Instead, it has a small nuclear power plant quarantined from the rest of the ship." "Many things can go wrong in such pioneering missions." "So people are a little uneasy at Voyager mission control." "Jupiter is surrounded by a shell of invisible but extremely dangerous high-energy charged particles." "If Voyager flies too close its delicate electronics will be fried." "A collision with a small boulder in the rings of Jupiter could send the spacecraft tumbling wildly out of control its antenna unable to find the Earth, its data lost forever." "Voyager 1 and Voyager 2 were launched a month apart in late summer of 1977." "After many alarms and close calls they successfully arrived months apart at the Jupiter system where they worked brilliantly providing the first close-up views of mighty Jupiter and its four large and mysterious moons:" "Io, the innermost of the four Europa and moving away from Jupiter Ganymede and the outermost big moon Callisto." "In a mission that costs a penny a world for every human on the planet Earth." "Voyager's passage by Jupiter accelerated it towards the planet Saturn." "Saturn's gravity will propel it on to Uranus and in this game of cosmic billiards, after Uranus it will plunge on past Neptune, leaving the solar system and becoming an interstellar spacecraft destined to wander forever the great ocean between the stars." "And if Voyager should, sometime in its distant future encounter beings from some other civilization in space it bears a message." "A phonograph record." "Golden, delicate with instruction for use." "And on this record are a sampling of pictures, sounds, greetings and an hour and a half of exquisite music the Earth's greatest hits." "A gift across the cosmic ocean from one island of civilization to another." "The record bears in English an additional handwritten greeting that says:" ""To the makers of music, all worlds, all times."" "These voyages of exploration and discovery are the latest in a long series which have characterized and distinguished the human species." "In the 1 5th and 16th centuries you could travel from Spain to the Azores in a few days." "The same time it takes now to cross that little channel from the Earth to the moon." "It took, then, a few months to traverse the Atlantic Ocean and reach what was called the "New World" the Americas." "Today it takes a few months to cross the inner solar system and reach Mars and Venus, truly and literally new worlds awaiting us." "In the 1 7th and 18th centuries you could travel from Holland to China, say, in a year or two the same time it takes now for Voyager to travel from the Earth to Jupiter." "And in comparison to the resources of the society it cost more then to send sailing ships to the Far East than it does now to send spaceships to the planets." "The passion to explore is at the heart of being human." "This impulse to go, to see, to know has found expression in every culture." "Africa was circumnavigated by Phoenician sailors in the employ of an Egyptian pharaoh in the 7th century B.C." "The islands of the Pacific were settled by skilled and heroic navigators from Indonesia." "Great fleets of ocean-going junks left the ports of Ming Dynasty China to explore India and Africa." "A century later, three ships left Spain under the command of an Italian navigator to discover the Americas." "And then a Portuguese expedition succeeded in sailing all the way around this blue globe." "These voyagers of many cultures were the first planetary explorers." "They have bound the Earth up into one world." "In our exploration of other worlds we follow in their footsteps." "Our present spaceships are the harbingers the vanguard of future human expeditions to the planets." "We have traveled this way before and there is much to be learned by studying those great voyages of a few centuries ago." "In the 1 7th century the citizens of the new Dutch Republic pursued a course of vigorous planetary exploration." "Holland was then a revolutionary society." "It had just declared its independence from the powerful but stagnant Spanish empire and with a newfound self-confidence Holland embraced, more fully than any other nation of its time the spirit of the European Enlightenment." "It was a rational, orderly and creative society." "But because Spanish ports and vessels were closed to the Dutch the economic survival of the tiny republic depended on its ability to construct, man and operate a great fleet of commercial sailing vessels." "The Dutch East India Company was a combined governmental and commercial enterprise which sent shipping to the far corners of the world to acquire rare commodities and resell them at a profit in Europe." "Such voyages were the life's blood of the republic." "Navigational charts and maps were classified as state secrets." "Ships sometimes left with sealed sailing orders the crews embarking for an unknown destination more than a year away on the far side of the planet." "These expeditions were not only commercial exploitations although there was certainly plenty of that." "Beside the usual appeals of ambition, greed national pride and the thirst for adventure the Dutch were also motivated by a powerful scientific curiosity and a fascination with all things new." "New lands, new peoples new plants and animals." "This building, then the Amsterdam town hall still attests to the hardy self-assurance of its 1 7th-century architects." "Its lavish crystal adornments still reflect the glittering pride they felt in their accomplishments and their prosperity." "It took shiploads of marble to build this place." "Constantin Huygens, a poet and diplomat of the time said that this town hall dispelled what he called "the Gothic squint and squalor."" "The Middle Ages had ended, the Enlightenment had begun." "Up there, do you see is Atlas supporting the heavens on his shoulders." "And beneath is Justice with a golden sword and golden scales flanked by Death and Punishment." "And who is it that Justice is trampling underfoot?" "Why, it's Avarice and Envy the gods of the merchants." "The Dutch knew that the unrestrained pursuit of profit posed serious threats to the soul of the nation." "A less allegorical symbol is down here, on the floor." "It is a great inlaid map stretching from West Africa to the Pacific Ocean." "The whole world was then Holland's arena." "In a typical year, many sailing vessels set out halfway around the world for the Far East on voyages of exploration and discovery, of trade journeys taking years to accomplish." "Down the west coast of Africa, through what they called the Ethiopian sea skirting the southern coast of Africa through the Straits of Madagascar and on past the southern tip of India to the Spice Islands and present-day Indonesia." "Another set of voyages went south then east, to New Holland later renamed Australia." "And still other journeys ventured through the Straits of Malacca to the Empire of China." "But Holland was a small country forced to live by its wits." "There was a strong pacifist element in its foreign policy." "Never before or since has Holland boasted such a galaxy of scientists, mathematicians, philosophers and artists." "This was the time of the great painters, Rembrandt and Vermeer." "Because Holland was tolerant of unorthodox opinions it was a refuge for intellectuals fleeing the thought control and censorship of other parts of Europe much as the United States benefited enormously in the 1 930s from the exodus of intellectuals from Nazi-dominated Europe." "And so it was that 17th-century Holland was the home of the great Jewish philosopher Spinoza who Einstein admired so much of René Descartes, a pivotal figure in the history of philosophy and of mathematics and the home of a political scientist named John Locke who was to have a powerful and profound influence on a group of philosophically inclined revolutionaries named Paine, Hamilton, Adams Franklin and Jefferson." "The Dutch University of Leyden offered a professorship to an Italian scientist named Galileo who had been forced by the Catholic Church under threat of torture to recant the heretical position that the Earth went around the sun and not vice versa." "Galileo had close ties with Holland." "His first astronomical telescope was based on a spyglass of Dutch manufacture." "And with it, he discovered the craters of the moon the phases of Venus and the four large moons of Jupiter." "Becoming an exploratory power made Holland a vital intellectual and cultural center as well." "The improvement of sailing technology spurred technology in general." "A key problem in navigation was the determination of longitude." "Latitude could be determined easily the farther south, the more southern constellations you could see." "But longitude required precise timekeeping." "An accurate shipboard clock would continue to keep time in your home port." "The rising and setting of stars would give you the local time and the difference between the two would tell you how far east or west you had gone." "Technological advance required the freest possible pursuit of knowledge." "So Holland became the leading publisher and bookseller in Europe translating works written in other languages and printing books that had been censored elsewhere." "Adventures into exotic lands and encounters with strange societies shook complacency." "They challenged the prevailing wisdom and showed that ideas accepted for thousands of years might be fundamentally in error." "In a time when kings and emperors ruled much of the planet the Dutch Republic was governed, more than any other world power by the people." "They enjoyed a certain material well-being." "But the interiors of their houses celebrated by a generation of Dutch painters suggest restraint and discretion." "The officers of these ships of exploration and trade would return from their long voyages share in the goods they had acquired and discuss the wonders they had encountered." "Holland prospered in its freedom of thought." "In Italy, Galileo had announced other worlds." "Giordano Bruno had speculated on intelligent life elsewhere." "For this they were made to suffer brutally." "But in Holland, the astronomer Christiaan Huygens who strongly supported both ideas, was showered with honors." "Christiaan was the son of Constantin Huygens." "The elder Huygens distinguished himself as a master diplomat of the age, a man of letters a close friend and translator of the English poet, John Donne." "Constantin was also an accomplished composer and musician." "It was Constantin who had discovered a young painter named Rembrandt van Rijn in several of whose works he subsequently appears." "He opened the doors of his house to artists, musicians, writers statesmen and scientists." "A feast of goods and ideas from all over the world awaited them." "The philosopher Descartes, who visited him here said of Constantin Huygens "I could not believe that a single mind could occupy itself with so many things and acquit itself so well in all of them."" "He even excelled at the art of parenthood." "He was a tender and loving father." "His son, Christiaan, flourished in this rich environment demonstrating extraordinary talents for languages, drawing law, science, engineering mathematics and music." ""The world is my country," he said "science my religion."" "Light was the motif of the age the symbolic enlightenment of freedom of thought and religion the light that suffused the paintings of the time and light as an object of scientific study." "The microscope was invented in Holland at this time and became a drawing-room curiosity." "Its inventor was a friend of Christiaan Huygens a man named Anton Leeuwenhoek." "The first microscopes were developed from magnifying glasses used by drapers to examine the quality of cloth." "Leeuwenhoek and Huygens are the grandfathers of much of modern medicine." "Because, to his amazement Leeuwenhoek discovered a universe in a drop of water:" "The microbes, which he described as "animalcules" and thought "cute."" "Leeuwenhoek and Huygens were among the first people to see human sperm cells a hitherto hidden microcosm of the human life cycle." "Leeuwenhoek had discovered the microbial world." "Huygens had argued from his telescopic observations that Mars was another world and probably, an inhabited one." "What a waste of a planet, he thought if Mars were barren." "So the Viking search for microbes on Mars can be traced directly back to Huygens and Leeuwenhoek in 1 7th-century Holland." "The telescope and the microscope developed here represent an extension of human vision to the realms of the very small and the very large." "Our observations of atoms and galaxies were launched in this time and place." "From the bending of light through a lens Huygens advanced the idea that light was a kind of wave." "He ground and polished lenses for the successively larger telescopes he constructed although it did take him a time to figure out how to use them properly." "Huygens was the first person to see a surface feature on the planet Mars." "He was the first person to speculate that Venus is completely covered with clouds." "He was the first person to understand the nature of the rings of Saturn." ""Saturn is surrounded," he wrote "by a thin, flat ring which nowhere touches the body of the planet."" "His discoveries with the telescope who by themselves have ensured his place in the history of human accomplishment." "Huygens was the discoverer of Titan the largest moon of Saturn." "The immense size and changing clouds of Jupiter entranced him." "Astronomers, as well as navigators need accurate clocks to time the movement of the heavens." "Huygens was the inventor of many precision timepieces including the pendulum clock." "To illustrate the sun-centered universe of Copernicus he built computers that reproduced the clockwork of the heavens from Mercury to Saturn." "The machines he designed, he signed "Christiaan Huygens, inventor."" "He was delighted that the Copernican system was widely accepted in everyday life in Holland and acknowledged by astronomers, except those, he wrote who "were a bit slow-witted or under the superstitions imposed by merely human authority." "Across the sea of space the stars are other suns."" "A point which Huygens appreciated perfectly well." "He reasoned that if our planetary system involved the sun and planets going around it that those other suns should likewise have a retinue of planets going around them and also that many of the other planets were inhabited." "He set forth these conclusions in a remarkable book bearing the triumphant title The Celestial Worlds Discovered." "The subtitle is "Conjectures Concerning the Inhabitants, Plants and Productions of the Worlds in the Planets."" "He wrote this book sometime shortly before his death in the year 1 690, in this study." "By and large he imagined that the environments of the other planets and also the inhabitants of the other planets were pretty much like those of 17th-century Europe." "I wonder if he imagined traveling to those other worlds which he had been the first to examine close-up through the telescope." "Perhaps he dreamt that voyages of discovery to the planets would one day be like the voyages of geographical discovery in his time and place." "He did imagine of extraterrestrial beings "that their whole bodies, and every part of them may be quite distinct and different from ours." "'Its a very ridiculous opinion," he says "that it is impossible a rational soul should dwell in any other shape than ours."" "You could be smart, Huygens was saying even if you looked funny." "But he then went on to argue that they didn't look all that funny that extraterrestrial beings must have hands and feet and stand upright and have writing and geometry." "Even that the four moons of Jupiter the Galilean satellites, were there in order to provide a navigational aid, a convenience for the sailors in the Jovian oceans." "Well, maybe." "(WOOD CREAKS)" "That bit of speculation is probably wrong, but think of a citizen of the 1 7th century with the courage and insight to imagine other landscapes and other intelligences." "Might there really be mariners on a million other worlds?" "In his book, Huygens wrote:" ""What a wonderful and amazing scheme have we here of the magnificent vastness of the universe." "So many suns." "So many earths." "And every one of them stocked with so many animals." "Adorned with so many seas." "How must our wonder and admiration be increased when we consider the prodigious distance and multitude of the stars?"" "The Dutch called their ships "flying boats" and the Voyager spacecraft are their descendants true flying boats bound for the stars, and on the way exploring some of those worlds which Christiaan Huygens a man from Earth knew and loved so well." "Travelers' tales:" "A main commodity returned by those sailing ship voyages of centuries ago were stories." "Stories of alien lands and exotic creatures." "They evoked a sense of wonder and stimulated further exploration." "Those tales of strange worlds enabled some Europeans to see themselves anew." "There had been accounts of headless people, foot people cyclops people." "Now the Dutch brought back fantastic stories of giant hunters dodoes rhinos leopards and other creatures." "Modern voyagers also return travelers' tales:" "Tales of a world shattered like a crystal sphere." "A place where the ground is covered with what looks like a network of giant cobwebs." "A world with an underground ocean." "Tiny moons shaped like potatoes." "A yellow and red pockmarked land with lakes of molten sulfur and volcanic eruptions 300 kilometers high." "And a place called Jupiter so large that a thousand Earths would fit inside." "There are no mountains, valleys, volcanoes or rivers there." "Just a vast ocean of gas and clouds." "Everything we see on Jupiter is floating in the sky." "But there's much that is fascinating about Jupiter." "As the solar system condensed out of interstellar gas and dust Jupiter acquired most of the matter not ejected into interstellar space and which didn't fall inwards to form the sun." "Jupiter is made mostly of hydrogen and helium, just like the sun and had Jupiter been a few dozen times more massive the matter in it might have undergone thermonuclear reactions in the interior and Jupiter would have begun to shine by its own light." "Jupiter is a star that failed." "Had it become a star we would be living in a double-star system with two suns in our sky and the nights would come more rarely." "Deep below the clouds of Jupiter, the weights of the layers of atmosphere produce pressures which are much greater than any that are found anywhere on the Earth." "The clouds are this layer here." "The deep interior is this high-pressure place." "The pressure is so large that electrons are squeezed off hydrogen atoms, producing liquid metallic hydrogen." "But at the very core of Jupiter, there may be a lump of rock and iron a giant Earth-like world under astonishing pressures hidden forever at the center of the largest planet." "Just before Voyager encountered Jupiter, you could see that giant planet at night shining in the sky as our ancestors have for the last million years." "And on my way to study the Voyager data arriving at the Jet Propulsion Laboratory I thought that Jupiter would never be the same again." "Never again just a point of light in the night sky but forever after, a place to be explored and known." "To see the first close-up images of a world never before known is a great joy in the life of a planetary scientist." "In the early morning hours of July 9th, 1979, on the real-time television monitors at the Jet Propulsion Laboratory we began to learn about a world called Europa." "These are the modern explorers." "Men and women trained in astronomy, physics, geology or engineering." "Many devoting five to eight years to this single mission." "JPL MAN:" "Cassen's model for Europa says if you start with a liquid you can put in enough energy to keep it liquid." "But Cassen said in order for there to be enough heating going on you had to start the heating before Europa basically cooled off." "But what about relief from the cracks?" "...and Europa there's a twin, a pair there..." "You can't look at a world so different from ours without wondering how both were made." "Just rotate it out a little bit." "Voyager presented us with six new worlds in the Jupiter system alone." "The more you learn about other worlds, the better you understand our own." "We speculate, criticize, argue, calculate, reflect and wonder." "We return again to the astonishing data, and slowly we begin to understand." "The Dutch sailing ships brought back rare and valuable commodities from the new worlds they visited." "Our Voyager spaceships return rare and valuable information to computerized wharves on this shore of the sea of space." "Here the data are stored, enhanced, processed and treasured." "Maps of alien lands will be generated from this information." "In this electric warehouse are tens of thousands of images of previously unknown worlds." "How does a picture from the outer solar system get to us?" "Sunlight shines on Europa, and is reflected back to space where some strikes the phosphors of the Voyager television cameras, generating an image." "The image is radioed back across the immense distance of half a billion kilometers to a radio telescope on Earth." "One in Australia, say." "The telescope then passes the information via communications satellite in Earth orbit to Southern California." "There, it's transmitted by a set of microwave relay towers to a computer at the Jet Propulsion Laboratory and there it is processed." "The picture is like a newspaper wire photo made of a million individual dots of differing shades of gray so fine and close together that at a distance the constituent dots are invisible." "We see only their cumulative effect." "The information specifies how bright or dark each dot is to be." "After processing, the dots are stored on a magnetic disk something like a phonograph record." "By this day, there were already 1 1,000 pictures from Voyager 2 in our electronic library." "Finally, the end product of this remarkable set of links and relays is a hard copy which comes out of this machine showing in this case, the wonders of Europa which were recorded for the first time in human history, today." "It is absolutely astonishing." "Voyager 1 got very good pictures of the other three big moons Galilean satellites of Jupiter, but not of Europa." "It was left to Voyager 2 today to get the first close-up pictures of Europa where we see things that are only a few kilometers across." "At first glance, it looks like nothing so much as the canal network of Mars that Lowell imagined existed on that planet." "We see an amazing, intricate network of crisscrossing straight and curved lines." "Are these straight lines ridges?" "Are they troughs?" "Is it connected with plate tectonics on the Earth?" "How does it illuminate the other satellites of the Jovian system?" "At this moment, the vaunted technology has produced something astonishing." "But it remains for the limitations and cleverness of another device the human brain, to figure it out." "Fortunately, we have plenty of pictures to help us." "What about Gene's idea of geysers down the troughs?" "Geysers down the troughs?" "LARR Y SODERBLOM:" "You need a mechanism to drive it." "SAGAN:" "Larry Soderblom, Voyager imaging team." "LARR Y:" "An idea was proposed a while ago that we might have a sort of champagne-bottle model." "And that's..." "You seal the crust and have liquid underneath that solid crust." "Do you have then a condition which is an explosive effervescence?" "SAGAN:" "Lonnie Lane, deputy project scientist." "You have enough resolution in some of these pictures that you don't see anything spread laterally." "Do we have the high-resolution piece?" "It was right here." "There it is." "We'll pick out the relief, and if we're going to see the things we recognize..." "SAGAN:" "Weeks after the pictures from Europa were received we were still debating what was in them." "It's as if we almost got to the..." "Look at the mesas here." "We almost got the resolution needed to see the craters." "The craters which would last indefinitely on a crust this thin." "Apart from the réseaus there's a set of very fine small dots, markings mostly in the mottled terrain." "Like those guys." "Do you think those are sites of outgassing, calderas, fumaroles, solfataras?" "I don't know, but I'll tell you one thing I just found..." "Look right here." "It disappeared." "See the central peak?" "See the little hole?" "I think it's an impact crater." "Look at the central peak." "SAGAN:" "There are almost no impact craters." "Wait, we just found one." "Almost none." "Therefore, finding one which is alleged to be the exception maybe it's not the exception, but something else." "Perhaps, but you asked about those little holes that we can't make out." "The big craters go away by some rheological deformation and the little ones stay but are out of our resolution." "That's because they're one-tenth the depth of the rigid crust." "Well, maybe." "SAGAN:" "Computer processing of the pictures has revealed a few features on Europa which seem to be impact craters." "But something has wiped out the big craters." "Computer processing also played a major role in an amazing Voyager discovery made on the moon next to Europa a world called lo." "Even from Earth we could tell that lo had a strange color." "We knew that somehow sulfur had been removed from its surface and ejected into a great doughnut of gas orbiting Jupiter." "Then Voyager 1 sailed close to lo." "There were a few places on lo which looked like the mouths of volcanoes but it was hard to be sure." "Then, Linda Morabito, a member of the Voyager navigation team used a computer to enhance the edge of lo in order to bring out the stars behind." "Four days after the Voyager 1 encounter with Jupiter I was looking at an optical navigation frame." "In enhancing this particular quadrant, what became very evident to me was an anomalous crescent in the upper left-hand corner, just off the limb of lo." "SAGAN:" "What was it?" "The plume was in exactly the position of one of the suspected volcanoes." "We realized then that what we were observing was a volcanic plume and, in fact, a volcanic eruption." "SAGAN:" "Voyager had discovered the first active volcano beyond the Earth." "We then found that lo has many volcanoes." "There are at least nine intermittently active plumes and hundreds, maybe thousands, of extinct ones." "The plumes can eject sulfur and other atoms off lo altogether and account for the sulfur clouds surrounding Jupiter." "Rivers of molten sulfur flow down the sides of the volcanic mountains and are the probable source of Io's distinctive colors." "The volcanoes may be tapping some vast underground ocean of liquid sulfur beneath a surface that is only a few thousand years old." "So far, in our voyages to the outer solar system we humans have stayed home and sent robots and computers to explore in our stead." "Someday, perhaps, we'll go ourselves." "But suppose like those Dutch sea captains of the 1 7th century the computers aboard Voyager could keep a ship's log." "That log, a combination of the events of Voyagers 1 and 2 might read something like this:" "Day 1:" "After much concern about provisions and instruments we successfully lift off from Cape Canaveral on our long journey to the planets and the stars." "Day 13:" "We have taken the first photograph of the Earth and moon as worlds together in space." "A pretty pair." "Day 1 70:" "A problem in the deployment of the boom that supports the science scan platform." "If the problem is not solved we will be unable to take most of our pictures." "Day 207:" "Boom problem solved, but failure of main radio transmitter." "If the backup transmitter also fails no one on Earth will ever hear from us again." "Day 21 5:" "We cross the orbit of Mars and enter the main asteroid belt." "Day 570:" "We can now make out finer detail on Jupiter than the largest telescopes on Earth have ever obtained." "Day 640:" "The cloud patterns are distinctive and gorgeous." "No painter trapped on Earth ever imagined a world so strange and lovely." "The white clouds are ammonia crystals, high and cold." "We do not know the nature of the red-brown clouds." "Maybe phosphorous or sulfur as a stain." "Perhaps organic molecules of the sort that led, four billion years ago back on Earth, to the origin of life." "And what is the great red spot?" "(COMPUTER HUMS)" "It is an immense swirling column of gas reaching high above adjacent clouds." "So large that it could hold half a dozen Earths." "Its motion hypnotizes us." "Some think that the red spot is a great spinning storm a million years old." "Day 650:" "Encounter." "A day of wonders." "The ship maneuvers so we can take pictures of the multi-ringed basin on Callisto." "Images of the astonishing lined surface of Ganymede." "A close passage by Europa." "And, a view of volcanic lo." "We successfully negotiate the treacherous radiation belts and accomplish the ring plane crossing." "Looking back, we marvel at the rings and see the sun emerge from behind the giant planet." "We are outward bound on our mission to explore the outer solar system." "Ten thousand years from now Voyager will plunge onward to the stars." "We have made the ships that sail the sea of space." "We travel past Jupiter three quarters of a billion kilometers from the sun Saturn, one and a half billion, Uranus, three billion and Neptune, four and a half billion kilometers away." "In our ship of the mind we retrace the itinerary of the two Voyager spacecraft on their journeys to Saturn and beyond." "Saturn was first glimpsed through the telescope by Galileo." "Its rings first understood by Huygens." "But only now do we begin to penetrate its deeper mysteries." "Saturn is the second largest planet in the solar system." "Like Jupiter, it is cloud-covered, and rotates once every 10 hours." "It has a weaker magnetic field, a weaker radiation belt and a grand, magnificent exquisite system of rings." "The rings are composed of billions of tiny moons each circling Saturn in its own orbit." "The biggest gap in the rings is called the Cassini Division after the colleague of Huygens who first discovered it." "There are many other gaps each produced by the periodic gravitational tugs of one of the larger outer moons." "From just beneath the ring plane we see a sky full of moons." "Within the rings, the individual moons become visible." "They are orbiting chunks of snow and ice each perhaps a meter across." "In young parts of the ring system, there hasn't been enough time for collisions to round the edges of these fragments the snowballs of Saturn." "Far from the rings, bathed in its red light we encounter Saturn's immense cloud-covered moon Titan." "It has an atmosphere denser than that of Mars and a thick layer of red clouds which are probably composed of complex organic molecules produced by solar ultraviolet light and other energy sources from the methane-rich air." "No ship from Earth has ever penetrated those clouds and viewed, close-up, the surface of this tantalizing world." "It seems likely that the ground is covered, encrusted with organic molecules raining from the sky." "There may be volcanoes and valleys of ice and, just perhaps hiding in the warm places, some very different kind of life." "Near an ice cliff of Titan through a rare break in the clouds of organic molecules we can see, looming and lovely, the ringed planet, Saturn." "It is a view that will still be appreciated centuries from now by our descendants, who will know it well." "As well as we have come to know Hudson's Bay and the Barents Sea Indonesia, and Australia and New York." "They will look back to when Titan was first seen by Voyager spaceships on their epic journeys past the giant planets out of the solar system to the great dark between the stars." "Since Cosmos was first shown Voyager spacecraft have explored the systems of the planets Saturn, Uranus, and Neptune and have now passed the outermost planets on their way to the stars." "We inserted the flavor of those encounters in our captain's log." "But with image processing we've been able to reconstruct astonishing movies of some of these worlds." "Here, for example, is Jupiter, with its great red spot." "And volcanic lo, spinning before us." "Icy Enceladus, a tiny moon of Saturn, on much of which, somehow the craters have melted." "And Miranda, of Uranus." "Austere, blue Neptune." "Or consider Titan, the giant moon of Saturn." "We've taken the nitrogen and methane in its atmosphere irradiated it in the lab with electrons of the sort that are beamed at Titan from Saturn's magnetic field and we made this stuff which matches, almost perfectly, the observed properties of the Titan haze." "What is it?" "It's a mixture of complex organic molecules." "You drop some into water and, among other things, you make amino acids, the building blocks of proteins." "So the starting materials of life are raining from the skies of Titan, like manna from heaven." "I can't wait until the Cassini mission sends an entry probe through the organic haze of Titan to its enigmatic surface." "The Voyager spacecraft rush on past the planets and to the stars still returning data." "As it left the planetary part of the solar system Voyager 1 turned back to take one last portrait of the planets of the solar system." "...and one of those pictures was of the Earth." "A tiny blue dot, set in a sunbeam." "Here it is." "That's where we live." "That's home." "We humans are one species, and this is our world." "It is our responsibility to cherish it." "Of all the worlds in our solar system, the only one, so far as we know graced by life." "Already in 1 980, Carl was saying that Jupiter's moon Europa had an underground ocean." "In 1 997, the Galileo spacecraft provided detailed images of ice rafts on Europa which support this interpretation." "As Carl here examines a Voyager image of Europa when it arrives on Earth for the first time, he points out the absence of big craters." "This means the surface is geologically very young and supports the idea of an ocean under a surface layer of ice." "SAGAN:" "The sky calls to us." "If we do not destroy ourselves .we will one day venture to the stars." "There was a time when the stars seemed an impenetrable mystery." "Today, we have begun to understand them." "In ourpersonal lives also, we journey from ignorance to knowledge." "Ourindividual growth reflects the advancement of the species." "The exploration of the cosmos is .a voyage ofself-discovery." "When I was a child, I lived here .in the Bensonhurst section of Brooklyn in the city ofNew York." "I knew my immediate neighborhood intimately .every candy store, front stoop .back yard, empty lot .and wall forplaying Chinese handball." "It was my whole world." "But more than a few blocks away .north of the raucous traffic and elevated railway on 86th Street .was an unknown territory off-limits to my wanderings." "It could have been Mars forall I knew." "Even with an early bedtime in the winter .you could occasionally see the stars." "I would look up at them and wonder what they were." "I'd ask other kids and adults .and they would answer:" ""They're lights in the sky, kid."" "Well, I could tell they were lights in the sky, but what were they?" "There had to be some deeper answer." "I remember I was issued my first library card." "It was some library on 85th Street." "Anyway, it was in alien territory." "And I asked the librarian for a book on stars." "She gave me .a picture book with portraits of men and women .with names like Veronica Lake and Alan Ladd." "I explained that wasn't what I wanted at all." "And for some reason, then obscure to me, she smiled .and got me another book, the right kind of book." "I was so excited to know the answer ." "I opened the book breathlessly, right there in the library .and the book said something astonishing .a very big thought." "Stars, it said, were suns .but very far away." "The sun was a star, but close-up." "How, I wondered, could anybody know such things forsure?" "How did they figure it out?" "Where did they even begin?" "I was ignorant of the idea of angular size." "I didn't know about the inverse square law of the propagation of light." "I didn't have any chance of calculating the distance to the stars." "But I could tell that if the stars were suns .they had to be awfully far away." "Further away than 86th Street, further away than Manhattan .further away, probably, than New Jersey." "The universe had become much grander .than I had ever guessed." "And then I read another astonishing fact." "The Earth, which includes Brooklyn .was a planet." "It went around the sun." "There were other planets." "They also went around the sun .some closer to the sun, some further from the sun." "But planets didn't shine by their own light the way the sun does." "No, planets simply reflected the little bit of light .that shines on them from the sun back to us." "If you were a great distance from the sun .you wouldn't be able to see the Earth or the other planets at all." "Well, then, it stood to reason, I thought .that those other stars ought to have their own planets .and some of those planets ought to have life." "Why not?" "And that life ought to be pretty different from life as we know it ." "life here in Brooklyn." "Ganymede." "Look at this amazing Ganymede stuff." "Wait, wait, wait." "As a child, it was my immense good fortune .to have parents and a few teachers who encouraged my curiosity." "This was my 6th-grade classroom." "I came back here one day to remember what it was like." "I brought some of the pictures of other worlds .that were radioed back by the Voyager spacecraft .ofJupiterand its moons." "This is Calisto which is" "(SAGAN LAUGHS)" "What is a Calisto?" "I want a Calisto." "Now you got it." "What is it?" "It's the outermost big moon of Jupiter." "Who is this guy?" "Europa." "Another Europa." "A black-and-white picture of a ring of Jupiter." "There you go." "That's a prize for honesty." "You didn't get a second." "Which one would you like?" "Every one of us begins life with an open mind .a driving curiosity, a sense of wonder." "I thought it might be fun if we now had some questions." "Why is the Earth round?" "Why isn't it square or any other shape?" "That's a good question." "That's a question I've asked myself." "The answer has to do with gravity." "The Earth has a strong gravity." "If you were to make a mountain very high .higher than Everest, the biggest mountain on Earth .it would be crushed by its own weight." "Gravity pulls everything towards the center." "So any really big bump on the Earth is crushed." "But if you had a small object, a tiny world .the gravity is very low .and then it can be very different from a sphere." "I think I have here a world that isn't a sphere." "Here." "Look at this one." "See?" "It's lumpy." "It's a lumpy world." "It looks like a potato." "There's a large potato orbiting the planet Mars." "This is one of the moons of Mars." "That's a perfect example." "You can have big departures from a sphere if your gravity is low." "Now the question in the front." "Is the sun considered part of the Milky Way galaxy?" "Sure, you're considered part of the Milky Way galaxy." "Everything except other galaxies is part of the Milky Way galaxy." "The sun is one star." "There is a few hundred billion stars in the Milky Way." "Around each star, maybe, is a whole bunch of planets." "And on one of those planets is life .and one of the life forms on that planet is you." "You're a part of the Milky Way galaxy too." "Sometimes I think, how lucky we are to live in this time .the first moment in human history when we are, in fact .visiting other worlds .and engaging in a deep reconnaissance of the cosmos." "But if we had been born in a much earlierage .no matterhow great our dedication, we couldn't have understood .what the stars and planets are." "We would not have known that there were othersuns and other worlds." "This is one of the great secrets wrested from nature .through a million years ofpatient observation and courageous thinking." "Human beings have always asked questions about the stars." "It's as natural as breathing." "But imagine a time before science had found out the answers." "Imagine what it was like, say .hundreds of thousands of years ago .soon after the discovery of fire." "We were just as smart and just as curious then .as we are now." "Sometimes it seems to me that .there were people then who thought like this:" "We are wandering hunter folk." "Fire keeps us warm." "Its light makes holes in the darkness." "It keeps hungry animals away." "In the darkness, we can see each otherand talk." "We take care of the flame." "The flame takes care of us." "The stars are not near to us." "When we climb a hill ora tree, they are no closer." "They flicker with a strange, cold, white .faraway light." "Many of them, all over the sky, but only at night." "I wonder what they are." "One night I thought the stars are flames." "They give a little light at night as fire does." "Maybe the stars are campfires .which other wanderers light at night." "The stars give a much smallerlight than campfires .so they must be very faraway." "I wonderif our campfires ." "look like stars to the people in the sky." "But why don't those campfires and the wanderers who made them .fall down at our feet?" "Why don't strange tribes drop from the sky?" "Those beings in the sky must have greatpowers." "I don't suppose that every hunter-gatherer .had such thoughts about the stars." "But we know from contemporary hunter-gatherer communities .that very imaginative ideas arise." "The Kung Bushmen .of the Kalahari Desert in the Republic of Botswana .have an explanation of the Milky Way." "At their latitude, it's often overhead." "They call it the "backbone of night."" "They believe it holds the sky up." "They believe that if not for the Milky Way .pieces of sky would come crashing down at our feet." "So the Milky Way, in their view, has some practical value." "The backbone of night." "Later on, metaphors about .campfires or backbones .or holes through which the flame could be seen .were replaced in most human communities by another idea." "The powerful beings in the sky were promoted to gods." "They were given names and relatives .and special responsibilities .for the cosmic services they were expected to perform." "There was a god for every human concern." "Gods ran nature." "Nothing happened without the direct intervention of some god." "If the gods were happy, there was plenty of food .and humans were happy." "But if something displeased the gods .and it didn't take much, the consequences were awesome:" "Droughts, floods, storms, wars .earthquakes, volcanic eruptions, epidemics." "The gods had to be propitiated." "And a vast industry of priests arose .to make the gods less angry." "But because the gods were capricious .you couldn't be sure what they would do." "Nature was a mystery." "It was hard to understand the world." "Ourancestors groped in darkness .to make sense of theirsurroundings." "Powerless before nature .they invented rituals and myths .some desperate and cruel .others imaginative and benign." "The ancient Greeks explained .that diffuse band ofbrightness in the night sky .as the milk of the goddess Hera .squirted from herbreast across the heavens." "We still call it the Milky Way." "In gratitude for the many gifts of the gods .ourancestors created works ofsurpassing beauty." "This is all that remains .of the ancient temple ofHera, queen ofheaven:" "A single marble column standing in a vast field ofruins .on the Greek island of Samos." "It was one of the wonders of the world .built bypeople with an extraordinary eye for clarity .and symmetry." "Those who thronged to that temple .were also the architects ofa bridge .from their world to ours." "We were moving once again in our voyage ofself-discovery .on ourjourney to the stars." "Here, 25 centuries ago .on the island of Samos and in the other Greek colonies .which had grown up in the busy Aegean Sea .there was a glorious awakening." "Suddenly, people believed that everything was made of atoms .that human beings and other animals had evolved from simpler forms .that diseases were not caused by demons or the gods .that the Earth was only a planet going around a sun .which was very far away." "This revolution made cosmos out of chaos." "Here, in the sixth century B.C., a new idea developed .one of the great ideas of the human species." "It was argued that the universe was knowable." "Why?" "Because it was ordered." "Because there are regularities in nature .which permitted secrets to be uncovered." "Nature was not entirely unpredictable." "There were rules which even she had to obey." "This ordered and admirable character of the universe .was called cosmos." "And it was set in stark contradiction .to the idea of chaos." "This was the first conflict of which we know .between science and mysticism .between nature and the gods." "But why here?" "Why in these remote islands and inlets of the eastern Mediterranean?" "Why not in the great cities of ." "India or Egypt, Babylon, China, Mesoamerica?" "Because they were all at the center of old empires." "They were set in their ways, hostile to new ideas." "But here in Ionia .were a multitude ofnewly colonized islands and city-states." "Isolation, even ifincomplete, promotes diversity." "No single concentration ofpower could enforce conformity." "Free inquiry became possible." "They were beyond the frontiers of the empires." "The merchants and tourists and sailors ofAfrica ." "Asia and Europe met in the harbors oflonia .to exchange goods and stories and ideas." "There was a vigorous and heady interaction .ofmany traditions, prejudices, languages and gods." "These people were ready to experiment." "Once you are open to questioning rituals .and time-honored practices .you find that one question leads to another." "What do you do when you're faced with several different gods .each claiming the same territory?" "The Babylonian Marduk and the Greek Zeus .were each considered king of the gods .master of the sky." "You might decide, since they otherwise had different attributes .that one of them was merely invented by the priests." "But if one, why not both?" "And so it was here that the great idea arose:" "The realization that there might be a way .to know the world without the god hypothesis." "That there be principles, forces, laws of nature .through which the world might be understood without attributing .the fall of every sparrow to the direct intervention of Zeus." "This is the place where science was born." "That's why we're here." "This Greek revolution happened between 600 and 400 B.C." "It was accomplished by the same practical and productive people .who made the society function." "Political power was in the hands of the merchants .who promoted the technology on which theirprosperity depended." "The earliestpioneers ofscience were .merchants and artisans and their children." "The first Ionian scientist was named Thales." "He was born over there in the city of Miletus .across this narrow strait." "He had traveled in Egypt .and was conversant with the knowledge of Babylon." "Like the Babylonians, he believed that the world had once all been water." "To explain the dry land .the Babylonians added that their god, Marduk .had placed a mat on the face of the waters .and piled dirt on top of it." "Thales had a similar view .but he left Marduk out." "Yes, the world had once been mostly water .but it was a natural process which explained the dry land." "Thales thought it was similar to the silting up he had observed .at the delta of the river Nile." "Whether Thales' conclusions were right or wrong .is not nearly as important as his approach." "The world was not made by the gods .but instead was the result of material forces .interacting in nature." "Thales brought back from Babylon and Egypt .the seeds of new sciences:" "Astronomy and geometry .sciences which would sprout and grow .in the fertile soil of Ionia." "Anaximander of Miletus, over there .was a friend and colleague of Thales .one of the first people that we know of .to have actually done an experiment." "By examining the moving shadow cast by a vertical stick .he determined accurately the lengths of the year and seasons." "For ages, men had used sticks .to club and spear each other." "Anaximander used a stick to measure time." "In 540 B.C., or thereabouts, on this island of Samos .there came to power a tyrant named Polycrates." "He seems to have started as a caterer .and then went on to international piracy." "His loot was unloaded on this very breakwater." "(DRUM BEATS)" "But he oppressed his own people, he made war on his neighbors." "He quite rightly feared invasion." "So Polycrates surrounded his capital city with an impressive wall .whose remains stand till this day." "To carry water from a distant spring through the fortifications .he ordered this great tunnel built." "A kilometerlong, itpierces a mountain." "Two cuttings were dug from eitherside .which met almostperfectly in the middle." "The project took some 15 years to complete." "It is a token of the civil engineering ofits day .and an indication of the extraordinarypractical capability .of the Ionians." "The enduring legacy of the Ionians .is the tools and techniques they developed .which remain the basis ofmodern technology." "This was the time of Theodorus .the master engineer of the age .a man who is credited with the invention of .the key, the ruler, the carpenter's square .the level, the lathe, bronze casting." "Why are there no monuments to this man?" "Those who dreamt and speculated .and deduced about the laws of nature .talked to the engineers and the technologists." "They were often the same people." "The practical and the theoretical were one." "(DRUM BEATS)" "This new hybrid ofabstract thought .and everyday experience blossomed into science." "When these practical men turned theirattention to the natural world .they began to uncover hidden wonders .and breathtaking possibilities." "Anaximanderstudied the profusion ofliving things .and saw theirinterrelationships." "He concluded that life had originated in waterand mud .and then colonized the dry land." ""Human beings," he said..." ""...must have evolved from simpler forms."" "This insight had to wait 24 centuries until its truth was demonstrated .by Charles Darwin." "Nothing was excluded from the investigations of the first scientists." "Even the airbecame the subject of close examination .by a Greek from Sicily named Empedocles." "He made an astonishing discovery .with a household implement that people had used for centuries." "This is the so-called water thief." "It's a brazen sphere with a neck and a hole at the top .and a set of little holes at the bottom." "It was used as a kitchen ladle." "You fill it by immersing it in water." "If, after it's been in there a little bit .you pull it out with the neck uncovered .then the water trickles out the little holes making a small shower." "Instead, if you pull it out with the neck covered .the water is retained." "Now try to fill it .with the neck covered with my thumb." "Nothing happens." "Why not?" "There's something in the way." "Some material is blocking the access of the water into the sphere." "I can't see any such material." "What could it be?" "Empedocles identified it .as air." "What else could it be?" "A thing you can't see can exert pressure .can frustrate my wish to fill this vessel with water .if I were dumb enough to leave my thumb on the neck." "Empedocles had discovered .the invisible." "Air, he thought, must be matter .in a form so finely divided .that it couldn't be seen." "This hint, this whiff of the existence ofatoms .was carried much furtherby a contemporary named Democritus." "Ofall the ancient scientists, it is he who speaks most clearly to us .across the centuries." "The few surviving fragments ofhis scientific writings .reveal a mind of the highest logical and intuitive powers." "He believed that a large number of other worlds wander through space .that worlds are born and die .that some are rich and living creatures .and others are dry and barren." "He was the first to understand that the Milky Way .is an aggregate of the light ofinnumerable faint stars." "Beyond campfires in the sky, beyond the milk ofHera .beyond the backbone ofnight, the mind ofDemocritus soared." "He saw deep connections between the heavens and the Earth." ""Man," he said, "is a microcosm .a little cosmos."" "Democritus came from the Ionian town ofAbdera .on the northern Aegean shore." "In those days, Abdera was the butt ofjokes." "If, around the year400 B.C .in the equivalent ofa restaurant like this .you told a story about someone from Abdera .you were guaranteed a laugh." "It was, in a way .the Brooklyn ofits time." "For Democritus, all of life was to be enjoyed and understood." "For him, understanding and enjoyment .were pretty much the same thing." "He said, "A life without festivity is a long road without an inn."" "Democritus may have come from Abdera, but he was no dummy." "Democritus understood that the complex forms .changes and motions of the material world .all derived from the interaction of very simple moving parts." "He called these parts atoms." "All material objects are collections ofatoms .intricately assembled .even we." "When I cut this apple .the knife must be passing through .empty spaces between the atoms, Democritus argued." "If there were no such empty spaces, no void .then the knife would encounter some impenetrable atom .and the apple wouldn't be cut." "Let's compare the cross sections of the two pieces." "Are the exposed areas exactly equal?" "No, said Democritus, the curvature of the apple .forces this slice to be slightly shorter than the rest of the apple." "If they were equally tall, then we'd have .a cylinder and not an apple." "No matter how sharp the knife .these two pieces have unequal cross sections." "But why?" "Because on the scale of the very small .matter exhibits some irreducible roughness .and this fine scale of roughness Democritus of Abdera identified .with the world of the atoms." "His arguments are not those we use today." "But they're elegant and subtle and derived from everyday experience." "And his conclusions were fundamentally right." "Democritus believed that nothing happens at random .that everything has a material cause." "He said, "I would rather understand one cause .than be king of Persia."" "He believed that poverty in a democracy was far better .than wealth in a tyranny." "He believed that the prevailing religions of his time were evil .and that neither souls nor immortal gods existed." "There is no evidence that Democritus was persecuted for his beliefs." "But then again, he came from Abdera." "However, in his time .the brief tradition of tolerance for unconventional views .was beginning to erode." "Forinstance, the prevailing belief was .that the moon and the sun were gods." "Another contemporary of Democritus, named Anaxagoras, taught .that the moon was a place made of ordinary matter .and that the sun was a red-hot stone far away in the sky." "For this, Anaxagoras was condemned .convicted and imprisoned for impiety .a religious crime." "People began to be persecuted for their ideas." "A portrait of Democritus is now .on the Greek 1 00-drachma note." "But his ideas were suppressed .and his influence on history made minor." "The mystics were beginning to win." "(DRUM BEATS)" "You see, Ionia was also the home .ofanother quite different intellectual tradition." "Its founder was Pythagoras .who lived here on Samos in the 6th century B.C." "According to local legend .this cave was once his abode." "Maybe that was once his living room." "Many centuries later .this small Greek Orthodox shrine was erected on his front porch." "There's a continuity of tradition from Pythagoras to Christianity." "Pythagoras was the first person in the history of the world .to decide that the Earth was a sphere." "Perhaps he argued by analogy with the moon or the sun .maybe he noticed the curved shadow of the Earth on the moon .during a lunar eclipse." "Or maybe he recognized that when ships leave Samos .their masts disappear last." "Pythagoras believed that a mathematical harmony .underlies all ofnature." "The modern tradition ofmathematical argument .essential in all ofscience owes much to him." "And the notion that the heavenly bodies move to a kind of .music of the spheres .was also derived from Pythagoras." "It was he who first used the word cosmos .to mean a well-ordered and harmonious universe .a world amenable to human understanding." "For this great idea, we are indebted to Pythagoras." "But there were deep ironies and contradictions in his thoughts." "Many of the Ionians believed .that the underlying harmony and unity of the universe was accessible .through observation and experiment .the method which dominates science today." "However, Pythagoras had a very different method." "He believed that the laws of nature can be deduced by pure thought." "He and his followers were not basically experimentalists .they were mathematicians .and they were thoroughgoing mystics." "They were fascinated by these five regularsolids .bodies whose faces are all polygons:" "Triangles orsquares .orpentagons." "There can be an infinite number ofpolygons .but only five regularsolids." "Four of the solids were associated with earth, fire, airand water." "The cube, for example, represented earth." "These four elements, they thought, make up terrestrial matter." "So the fifth solid .they mystically associated with the cosmos." "Perhaps it was the substance of the heavens." "This fifth solid was called .the dodecahedron." "Its faces are pentagons, 12 of them." "Knowledge of the dodecahedron .was considered too dangerous for the public." "Ordinary people were to be kept ignorant of the dodecahedron." "In love with whole numbers, the Pythagoreans believed .that all things could be derived from them .certainly all other numbers." "So a crisis in doctrine occurred when they discovered .that the square root of two was irrational." "The square root of two could not be represented as the ratio .of two whole numbers no matter how big they were." "Irrational originally meant only that .that you can't express a number as a ratio." "But for the Pythagoreans, it came to mean something else .something threatening .a hint that their world-view might not make sense .the other meaning of irrational." "Instead of wanting everyone to share and know of their discoveries .the Pythagoreans suppressed the square root of two .and the dodecahedron." "The outside world was not to know." "The Pythagoreans had discovered .in the mathematical underpinnings ofnature .one of the two most powerful scientific tools." "The other, of course, is experiment." "But instead of using theirinsight to advance .the collective voyage ofhuman discovery .they made ofit little more than the hocus-pocus ofa mystery cult." "Science and mathematics were to be removed from the hands .ofmerchants and artisans." "This tendency found its most effective advocate .in a follower ofPythagoras named Plato." "He preferred the perfection of these mathematical abstractions .to the imperfections of everyday life." "He believed that ideas were farmore real than the natural world." "He advised the astronomers not to waste their time .observing stars and planets." "It was better, he believed, just to think about them." "Plato expressed hostility to observation and experiment." "He taught contempt for the real world .and disdain for the practical application ofscientific knowledge." "Plato's followers succeeded in extinguishing the light .ofscience and experiment .that had been kindled by Democritus and the otherlonians." "Plato's unease with the world as revealed by oursenses .was to dominate and stifle Western philosophy." "Even as late as 1600 ." "Johannes Kepler was still struggling to interpret .the structure of the cosmos in terms of ." "Pythagorean solids and Platonic perfection." "Ironically, it was Kepler who helped re-establish the old Ionian method .of testing ideas against observations." "But why had science lost its way in the firstplace?" "What appeal did Pythagoras' and Plato's teachings .have for their contemporaries?" "Theyprovided, I believe .an intellectually respectablejustification .fora corrupt social order." "The mercantile tradition which had led to Ionian science .also led to a slave economy." "You could get richer .if you owned a lot of slaves." "Athens, in the time of Plato and Aristotle .had a vast slave population." "All of that brave Athenian talk about democracy .applied only to a privileged few." "Plato and Aristotle were comfortable in a slave society." "They offered justifications for oppression." "They served tyrants." "They taught the alienation of the body from the mind .a natural enough idea, I suppose, in a slave society." "They separated thought from matter." "They divorced the Earth from the heavens." "Divisions which were to dominate Western thinking .for more than 20 centuries." "The Pythagoreans had won." "In the recognition by Pythagoras and Plato .that the cosmos is knowable .that there is a mathematical underpinning to nature .they greatly advanced the cause ofscience." "But in the suppression of disquieting facts .the sense that science should be kept fora small elite .the distaste for experiment, the embrace ofmysticism .the easy acceptance ofslave societies .theirinfluence has significantly set back .the human endeavor." "The books of the Ionian scientists are entirely lost." "Their views were suppressed, ridiculed and forgotten .by the Platonists and by the Christians .who adopted much of the philosophy of Plato." "Finally, aftera long, mystical sleep .in which the tools of scientific inquiry lay moldering .the Ionian approach was rediscovered." "The Western world reawakened." "Experiment and open inquiry .slowly became respectable once again." "Forgotten books and fragments were read once more." "Leonardo and Copernicus and Columbus .were inspired by the Ionian tradition." "The Pythagoreans and theirsuccessors .held the peculiarnotion that .the Earth was tainted .somehow nasty .while the heavens were pristine and divine." "So the fundamental idea that the Earth is a planet .that we're citizens of the universe .was rejected and forgotten." "This idea was first argued byAristarchus .born here on Samos, three centuries afterPythagoras." "He held that the Earth moves around the sun." "He correctly located ourplace in the solarsystem." "Forhis trouble, he was accused ofheresy." "From the size of the Earth's shadow on the moon during a lunar eclipse .he deduced that the sun had to be much, much larger .than the Earth, and also very far away." "From this he may have argued that it was absurd .for so large an object as the sun to be going around .so small an object as the Earth." "So he put the sun rather than the Earth at the center of the solar system." "And he had the Earth and the other planets going around the sun." "He also had the Earth rotating on its axis once a day." "These are ideas that we ordinarily associate with the name Copernicus." "But Copernicus seems to have gotten some hint of these ideas .by reading about Aristarchus." "In fact, in the manuscript of Copernicus' book .he referred to Aristarchus, but in the final version .he suppressed the citation." "Resistance to Aristarchus, a kind of .geocentrism in everyday life, is with us still." "We still talk about a sun rising .and the sun setting." "It's 2200 years since Aristarchus .and the language still pretends that the Earth does not turn .that the sun is not at the center of the solarsystem." "Aristarchus understood the basic scheme of the solarsystem .but not its scale." "He knew that the planets move in concentric orbits about the sun .and he probably knew their order out to Saturn." "But he was much too modest in his estimates .ofhow farapart the planets are." "In order to calculate the true scale of the solarsystem .you need a telescope." "It wasn't until the 17th century that astronomers were able to get .even a rough estimate of the distance to the sun." "And once you knew the distance to the sun .what about the stars?" "How faraway are they?" "There is a way to measure the distance to the stars .and the Ionians were fully capable of discovering it." "Aristarchus had toyed with the daring idea .that the stars were distant suns." "Now, if a star were as near as the sun .it should appear as big and as bright as the sun." "Everyone knows that the farther away an object is, the smaller it seems." "This inverse proportionality between apparent size and distance .is the basis of perspective in art and photography." "So the further away we are from the sun .the smaller and dimmer it appears." "How far from the sun would we have to be for it to appear .as small and dim as a star?" "Or equivalently, how small a piece of sun .would be as bright as a star?" "An experiment to answer this question was performed in 1 7th-century Holland .by Christiaan Huygens and is very much in the Ionian tradition." "Huygens drilled a number of holes in a brass plate .and held the plate up to the sun." "He asked himself, which hole seemed as bright .as he remembered the star Sirius to have been the previous evening." "Well, the hole that matched was effectively .1l28,000th the apparent size of the sun." "So Sirius, he reasoned, must be 28,000 times .further away than the sun, or about half a light-year away." "It's hard to remember just how bright a star is .hours after you've looked at it, but Huygens remembered very well." "If he had known that Sirius was intrinsically brighter than the sun .he would've gotten the answer exactly right." "Sirius is 8.8 light-years away from us." "Between Aristarchus and Huygens .people had answered that question which had so excited me .as a young boy growing up in Brooklyn:" "The question, "What are the stars?"" "And the answer is that the stars are mighty suns, light-years away .in the depths of interstellar space." "And around those suns, are there otherplanets?" "And on those other worlds .are there beings who wonderas we do?" "Here is a light bulb .which is supposed to represent a nearby star." "Next to it, and very hard to see because of the bright light .is a planet." "We'll need a volunteer." "Who would like to come up, please?" "Ordinarily, it's hard to see the planet .because it's so close that the star washes out the planet." "But if we're able to put something in front of the star .to make an artificial eclipse, then we might be able to see the planet." "I'm gonna stand over here." "Imagine that I'm a telescope .somewhere near the Earth." "And, Tab, if you'd slowly move the disc across." "Good." "A little faster would be nice." "Now you're just beginning to cover over the star." "I really can't see the planet at all." "Keep going." "Now, right there ." "I can't see the star at all .and I see the planet lit by the light of the star." "Now, that is a method for looking for planets .around nearby stars." "And that method uses a spacecraft to hold the disc .and scan the sky for another telescope .to see if there are any planets." "Tab, you accomplished your mission to look for planets around other stars." "Thank you for being our interplanetary spacecraft." "So this is one way." "And there are spaceships that will be able to do this .in the next 1 0 years or so." "And there's another way." "This has already been tried from the Earth." "Imagine that there's a nearby star that you can see." "It's bright and it has a dark companion, a planet .shining only by reflected light near it, so dim you can't see it." "But imagine that this planet and its star .are going around each other." "Like that:" "You can see the star, you can't see the planet." "So now I'm gonna need two volunteers." "You two." "Just to save time because they're in the front row." "I need one of you to turn the star and the planet .and another person to pull the star and planet along." "And what you will see .is that the star you can make out .will be moving in a funny, wiggly pattern .which will be the clue, the evidence .for the existence of the dark planet." "Okay, let's have a spin." "Good." "And a pull." "And you see this funny motion .that the star makes because of the planet." "Thank you." "That's another way of finding out the existence of a planet .that you couldn't see directly." "Well, both of these methods are being used." "And by the time that you people are .as old as I am .we should know, for all the nearest stars .if they have planets going around them." "We might know dozens or even hundreds of other planetary systems .and see if they're like our own or very different .or no other planets going around other stars at all." "That will happen in your lifetime." "It'll be the first time in the world's history that anybody found out .if there are planets around the other stars." "Now, the nearby stars, the ones you can see with the naked eye .those are all in the solar neighborhood." "That's what astronomers call it:" "The neighborhood." "But it's a very tiny place in the Milky Way galaxy." "The Milky Way is that band of light .that you see across the sky on a clear night." "I can't tell if there are any more clear nights in Brooklyn." "You must've seen the Milky Way, a faint band of light at night." "Well, that's just 1 00 billion stars .all seen together .edge on, as in this picture." "If you could get out of the Milky Way and look down on it .it would look like that picture." "If we did look down on the Milky Way .where would the sun and nearby stars be?" "Would it be in the center where things look important .or at least well-lit?" "No." "We would be way out here .in the suburbs, in the countryside of the galaxy." "We're not in any important place." "All the stars you could see would be in a little place like that." "And the Milky Way would be this band of light .1 00 billion stars all together." "The fact that we live in the outskirts of the galaxy .was discovered a long time ago .towards the end of the First World War .by a man named Harlow Shapley .who was mapping the position of these clusters of stars." "See, every one of these is a bunch .of maybe 1 0,000 stars all together." "It's called a globular cluster." "And you can see that they are centered around the middle .the center of the galaxy." "People used to think that the sun was at the center of the galaxy .something important about our position." "That turns out to be wrong." "We live in the outskirts .the globular clusters are centered around .the marvelous middle of the Milky Way galaxy." "And then it turned out that this isn't the only galaxy." "We live in this one .but there are many others." "And as this picture reminds us .there are many different kinds of galaxies .of which ours might be just this one." "There are, in fact, 1 00 billion other galaxies .each of which contains something like 1 00 billion stars." "Think of how many stars and planets and kinds of life there may be .in this vast and awesome universe." "As long as there have been humans .we have searched for ourplace in the cosmos." "Where are we?" "Who are we?" "We find that we live on an insignificantplanet .ofa humdrum star ." "lost in a galaxy tucked away in some .forgotten corner ofa universe in which there are .farmore galaxies than people." "We make our world significant by the courage of our questions .and by the depth of ouranswers." "We embarked on ourjourney to the stars .with a question first framed .in the childhood of ourspecies .and in each generation asked anew .with undiminished wonder:" ""What are the stars?"" "Exploration is in ournature." "We began as wanderers .and we are wanderers still." "We have lingered long enough .on the shores of the cosmic ocean." "We are ready at last .to set sail for the stars." "SAGAN:" "We are drifting in a great ocean of space and time." "In that ocean, the events that shape the future are working themselves out." "Each creature and every world, to the remotest star owe their existence to the great, coursing, implacable forces of nature but also, to minor happenstance." "We are carried with our planet around the sun." "The Earth has made more than 4 billion circuits of our star since its origin." "The sun itself travels about the core of the Milky Way galaxy." "Our galaxy is moving among the other galaxies." "We have always been space travelers." "These fine sand grains are all, more or less, uniform in size." "They're produced from bigger rocks through ages of jostling and rubbing, abrasion and erosion." "Driven in part by the distant moon and sun." "So the roots of the present lie buried in the past." "We are also travelers in time." "But trapped on Earth we've had little to say about where we go in time and space or how fast." "But now we're thinking about true journeys in time and real voyages to the distant stars." "A handful of sand contains about 1 0,000 grains more than all the stars we can see with the naked eye on a clear night." "But the number of stars we can see is only the tiniest fraction of the number of stars that are." "What we see at night is the merest smattering of the nearest stars with a few more distant bright stars thrown in for good measure." "Meanwhile, the cosmos is rich beyond measure." "The number of stars in the universe is larger than all the grains of sand on all the beaches of the planet Earth." "Long ago, before we had figured out that the stars are distant suns they seemed to us to make pictures in the sky." "Just follow the dots." "The Big Dipper constellation today in North America has had many other incarnations." "Every culture, ancient and modern has placed its totems and concerns among the stars." "From a Chinese bureaucrat to a German wagon." "But very ancient cultures would have seen different constellations because the stars move with respect to one another." "We can give a computer the present positions and motions of stars and then run the patterns back into time." "Every constellation is a single frame in a cosmic movie but because our lives are so short because star patterns change slowly we tend not to notice it's a movie." "A million years ago, there was no Big Dipper." "Our ancestors, looking up and wondering about the stars saw some other pattern in the northern skies." "We can also run a constellation, Leo the Lion, say, forward in time and see what the patterns in the stars will be in the future." "A million years from now, Leo might be renamed the constellation of the Radio Telescope." "Although I suspect radio telescopes then will be as obsolete as stone spears are now." "Or, here's the constellation of Cetus the Whale." "A million years ago, it may have been called something else." "Perhaps the Spear." "Now, let's run fast-forward through a billion nights." "Millions of years from now some other very different image will be featured in this cosmic movie." "In Orion the Hunter, things are changing not only because the stars are moving but also because the stars are evolving." "Many of Orion's stars are hot, young and short-lived." "They're born, live and die within a span of only a few million years." "If we run Orion forward in time we see the births and explosive deaths of dozens of stars flashing on and winking off like fireflies in the night." "If we wait long enough, we see the constellations change." "But if we go far enough, we also see the star patterns alter." "Two-dimensional constellations are only the appearance of stars strewn through three dimensions." "Some are dim and near, others are bright but farther away." "Could a space traveler actually see the patterns of the constellations change?" "For that, you must travel roughly as far as the constellation is from us." "Here, we're traveling hundreds of light-years circling all the way around the stars of the Big Dipper." "Inhabitants of planets around other stars will see different constellations than us because their vantage points are different." "Here we are in the constellation Andromeda or at least a model of it next to the constellation Perseus." "Andromeda, in the Greek myth was the maiden who was saved by Perseus from a sea monster." "This star just above me is Beta Andromedae the second brightest star in the constellation 75 light-years from the Earth." "The light by which we see this star has spent 75 years traversing interstellar space on its journey to the Earth." "In the unlikely event that Beta Andromedae blew itself up a week ago Tuesday we will not know of it for another 75 years as this interesting information, traveling at the speed of light crosses the enormous interstellar distances." "When the light we see from this star set out on its long interstellar voyage the young Albert Einstein working as a Swiss patent clerk had just published his epochal special theory of relativity here on Earth." "We see that space and time are intertwined." "We cannot look out into space without looking back into time." "The speed of light is very fast but space is very empty and the stars are very far apart." "The distances that we've been talking about up to now are very small by the usual astronomical standards." "In fact, the distance from the Earth to the center of the Milky Way galaxy is 30,000 light-years." "From our galaxy to the nearest spiral galaxy like our own called M31  and which is also within, that means behind the constellation Andromeda is 2 million light-years." "When the light we see today from M31  left on its journey for Earth there were no human beings although our ancestors were nicely evolving and very rapidly, to our present form." "There are much greater distances in astronomy." "The distance from the Earth to the most distant quasars is 8 or 1 0 billion light-years." "We see them as they were before the Earth itself accumulated before the Milky Way galaxy was formed." "The fastest space vehicles ever launched by the human species are the Voyager spacecraft." "They are traveling so fast that it's only 1 0,000 times slower than the speed of light." "The Voyager spacecraft will take 40,000 years to go the distance to the nearest stars and they're not even headed towards the nearest stars." "But is there a method by which we could travel in a conveniently short time to the stars?" "Can we travel close to the speed of light?" "And what's magic about the speed of light?" "Can't we travel faster than that?" "It turns out that there is something very strange about the speed of light." "Something that provides the key to our understanding of time and space." "The story of its discovery takes us to Tuscany in northern Italy." "There's something timeless about this place." "A century ago, it probably looked very much the same." "If you had traveled these roads in the summer of 1895 you might have come upon a 16-year-old German high-school dropout." "His teacher told him that he'd never amount to anything that his attitude destroyed classroom discipline that he should drop out." "So he left and came here where he enjoyed wandering these roads and giving his mind free rein to explore." "One day, he began to think about light about how fast it travels." "We always measure the speed of a moving object relative to something else." "I'm moving at about 10 kilometers an hour relative to the ground." "But the ground isn't at rest." "The Earth is turning at more than 1600 kilometers an hour." "The Earth itself is in orbit around the sun." "The sun is moving among the drifting stars, and so on." "It was hard for the young man to imagine some absolute standard to measure all these relative motions against." "He knew that sound waves are a vibration of the air and their speed is measured relative to the air itself." "But sunlight travels across the vacuum of empty space." ""Do light waves move relative to something else?" "And if so," he wondered, "relative to what?"" "That teenage dropout's name was Albert Einstein." "And his ruminations changed the world." "He had been fascinated by Bernstein's 1 869 People's Book of Natural Science." "Here, on its very first page it describes the astonishing speed of electricity through wires and light through space." "Einstein wondered, perhaps for the first time, in northern Italy what the world would look like if you could travel on a wave of light." "To travel at the speed of light." "What an engaging and magical thought for a teenage boy on the road where the countryside is dappled and rippling in sunlight." "You couldn't tell you were on a light wave if you were traveling with it." "If you started on a wave crest you would stay on the crest and lose all notion of it being a wave." "Something funny happens at the speed of light." "The more Einstein thought about it, the more troubling it became." "Paradoxes seemed to pop up all over if you could travel at the speed of light." "Certain ideas had been accepted as true without sufficiently careful thought." "One of those ideas had to do with the light from a moving object." "The images by which we see the world are made of light and are carried at the speed of light 300,000 kilometers a second." "You might think that the image of me should be moving out ahead of me at the speed of light plus the speed of the bicycle." "If I'm moving towards you faster than a horse-and-cart then my image should be approaching you that much faster." "My image ought to arrive earlier." "But in reality you don't see any time delay." "In a near collision, for example, you see everything happen at once." "Horse, cart, swerve, bicycle." "All simultaneous." "But how would it look if it were proper to add the velocities?" "Since I'm heading toward you, you'd add my speed to the speed of light." "So my image ought to arrive before the image of the horse-and-cart." "I'd be cycling towards you quite normally." "To me, a collision would seem imminent." "But you'd see me swerve for no apparent reason and have a collision with nothing." "Now, the horse-and-cart aren't headed towards you." "Their image would arrive only at the speed of light." "Could it seem to me that I just missed colliding while to you it wasn't even close?" "In precise laboratory experiments scientists have never observed any such thing." "If the world is to be understood if we are to avoid logical paradoxes when traveling at high speeds then there are rules which must be obeyed." "Einstein called these rules the special theory of relativity." "Light from a moving object travels at the same speed no matter whether the object is at rest or in motion." ""Thou shalt not add my speed to the speed of light."" "Also, no material object can travel at or beyond the speed of light." "Nothing in physics prevents you from traveling close to the speed of light." "99.9 percent the speed of light is just fine." "But no matter how hard you try you can never gain that last decimal point." "For the world to be logically consistent there must be a cosmic speed limit." "The crack of a whip is, due to its tip moving faster than the speed of sound." "It makes a shock wave a small sonic boom in the Italian countryside." "A thunderclap has a similar origin." "So does the sound of a supersonic airplane." "So why is the speed of light a barrier any more than the speed of sound?" "The answer is not just that light travels a million times faster than sound." "It's not merely an engineering problem like the supersonic airplane." "Instead, the light barrier is a fundamental law of nature as basic as gravity." "Einstein found his absolute framework for the world:" "This sturdy pillar among all the relative motions of the cosmos." "Light travels just as fast, no matter how its source is moving." "The speed of light is constant, relative to everything else." "Nothing can ever catch up with light." "Einstein's prohibition against traveling faster than light seems to clash with our common sense notions." "But why should we expect our common sense notions to have any reliability in a matter of this sort?" "Why should our experience at 1 0 kilometers an hour constrain the laws of nature at 300,000 kilometers a second?" "Relativity sets limits on what humans ultimately can do." "The universe is not required to be in perfect harmony with human ambition." "Imagine a place where the speed of light isn't its true value of 300,000 kilometers a second but something a lot less." "Let's say, 40 kilometers an hour and strictly enforced." "Just as in the real world we can never reach the speed of light the commandment here is still "Thou shalt not travel faster than light."" "We can do thought experiments on what happens near the speed of light here 40 kilometers per hour, the speed of a motor scooter." "You can't break the laws of nature." "There are no penalties for doing so." "The real world and this one are merely so arranged that transgressions can't happen." "The job of physics is to find out what those laws are." "Before Einstein, physicists thought that there were privileged frames of reference some special places and times against which everything else had to be measured." "Einstein encountered a similar notion in human affairs." "The idea that the customs of a particular nation his native Germany or Italy or anywhere are the standard which all other societies must be measured." "But Einstein rejected the strident nationalism of his time." "He believed every culture had its own validity." "Also in physics, he understood that there are no privileged frames of reference." "Every observer, in any place, time or motion must deduce the same laws of nature." "(SPEAKING IN ITALIAN)" "A speed is simply how much space you cover in a given time as any kid on a motor scooter knows." "Since near the velocity of light we cannot simply add speeds the familiar notions of absolute space and absolute time independent of your relative motion, must give way." "That's why, as Einstein showed funny things have to happen close to the speed of light." "There, our conventional perspectives of space and time strangely change." "Your nose is just a little closer to me than your ears." "Light reflected off your nose reaches me an instant in time before your ears." "But suppose I had a magic camera so that I could see your nose and your ears at precisely the same instant?" "(SCOOTER STARTS UP)" "(SCOOTER HONKS)" "With such a camera you could take some pretty interesting pictures." "Paolo says goodbye to his little brother, Vincenzo..." "Ciao, Vincenzo." "Ciao, Paolo." "...and rides off." "He's now going more than half the speed of light." "He is almost catching up with his own light waves." "This compresses the light waves in front of him and his image becomes blue." "The shorter wavelength is what makes blue light waves blue." "Also Paolo becomes skinny in the direction of motion." "This isn't just some optical illusion." "It really happens when you travel near the speed of light." "As he roars away, he leaves his own light waves stretched out behind him." "Long light waves are red." "We say that his receding image is red-shifted." "Now Paolo leaves for a short tour of the countryside." "He experiences something even stranger." "Everything he can see is squeezed into a moving window just ahead of him blue-shifted at the center, red-shifted at the edges." "To a passerby, Paolo appears blue-shifted when approaching red-shifted when receding." "But to him, the entire world is both coming and going at nearly the speed of light." "Roadside houses and trees that has already gone past still appear to him at the edge of his forward field of view but distorted and red-shifted." "When he slows down, everything again looks normal." "Only very close to the speed of light does the visible world get squeezed into a kind of tunnel." "You'd see these distortions if you traveled near the speed of light." "Someday, perhaps, interstellar navigators will take their bearings on stars behind them whose images have all crowded together on the forward view screen." "The most bizarre aspect of traveling near the speed of light is that time slows down." "All clocks, mechanical and biological tick more slowly near the speed of light." "But stationary clocks tick at their usual rate." "If we travel close to light speed we age more slowly than those we left behind." "Paolo's watch and his internal sense of time show that he has been gone from his friends for only a few minutes." "But from their point of view, he has been away for many decades." "His friends have grown up, moved on and died." "And his younger brother has been patiently waiting for him all this time." "The two brothers experience the paradox of time dilation." "They've encountered Einstein's special relativity." "Vincenzo." "This was just a thought experiment." "But atomic particles traveling near the speed of light do decay more slowly than stationary particles." "As strange and counterintuitive as it seems time dilation is a law of nature." "Traveling close to the speed of light is a kind of elixir of life." "Because time slows down close to the speed of light special relativity provides us with a means of going to the stars." "This region of northern Italy is not only the caldron of some of the thinking of the young Albert Einstein it is also the home of another great genius who lived 400 years earlier." "Leonardo da Vinci." "Leonardo delighted in climbing these hills and viewing the ground from a great height as if he were soaring like a bird." "He drew the first aerial views of landscapes, villages, fortifications." "I've been talking about Einstein in and around this town of Vinci in which Leonardo grew up." "Einstein greatly respected Leonardo and their spirits, in some sense inhabit this countryside still." "Among Leonardo's many accomplishments in painting, sculpture, architecture, natural history anatomy, geology, civil and military engineering he had a great passion." "He wished to construct a machine which would fly." "He made sketches of such machines, built miniature models constructed great, full-scale prototypes." "And not a one of them ever worked." "There were no machines of adequate capacity available in his time." "The technology was just not ready." "The designs, however, were brilliant." "For example, this bird-like machine here in the Leonardo Museum in the town of Vinci." "Leonardo's great designs encouraged engineers in later epochs although Leonardo himself was very depressed at these failures." "But it's not his fault he was trapped in the 1 5th century." "A somewhat similar case occurred in 1 939 when a group of engineers called the British Interplanetary Society decided to design a ship which would carry people to the moon." "Now, it was by no means the same design as the Apollo ship which actually took people to the moon years later." "But that design suggested that a mission to the moon might one day be a practical engineering possibility." "Today we have preliminary designs of ships which will take people to the stars." "They are constructed in Earth orbit and from there they venture on their great interstellar journeys." "One of them is called Project Orion." "It utilizes nuclear weapons hydrogen bombs against an inertial plate." "Each explosion providing a kind of "putt-putt" a vast nuclear motorboat in space." "Orion seems entirely practical and was under development in the U.S until the signing of the international treaty forbidding nuclear weapons explosions in space." "I think, the Orion starship is the best use of nuclear weapons provided the ships don't depart from very near the Earth." "Project Daedalus is a recent design of the British Interplanetary Society." "It assumes the existence of a nuclear fusion reactor something much safer and more efficient than the existing nuclear fission power plants." "We do not yet have fusion reactors." "One day, quite soon, we may." "Orion and Daedalus might go 10 percent the speed of light." "So a trip to Alpha Centauri, 4 1 l2 light-years away would take 45 years, less than a human lifetime." "Such ships could not travel close enough to the speed of light for the time-slowing effects of special relativity to become important." "It does not seem likely that such ships would be built before the middle of the 21 st century although we could build an Orion starship now." "For voyages beyond the nearest stars, something must be added." "Perhaps they could be used as multigeneration ships so those arriving would be the remote descendants of those who had originally set out centuries before." "Or perhaps some safe means of human hibernation might be found so that space travelers might be frozen and then thawed out when they arrive at the destination centuries later." "But fast interstellar space flight approaching the speed of light is much more difficult." "That's an objective not for a hundred years but for a thousand or for 1 0 thousand but it also is possible." "A kind of interstellar ramjet has been proposed which scoops up the hydrogen atoms which float between the stars accelerates them into an engine and spits them out the back." "But in deep space, there is one atom for every 1 0 cubic centimeters of space." "For the ramjet to work it has to have a frontal scoop hundreds of kilometers across." "Reaching relativistic velocities, the hydrogen atoms will be moving with respect to the interstellar spaceship at close to the speed of light." "If precautions aren't taken the passengers will be fried by these induced cosmic rays." "There's a proposed solution:" "A laser is used to strip electrons off the atoms and electrically charge them while they're some distance away." "And an extremely strong magnetic field is used to deflect the charged atoms into the scoop and away from the spacecraft." "This is engineering on a scale so far unprecedented on the Earth." "We are talking of engines the size of small worlds." "Suppose that the spacecraft is designed to accelerate at 1 g so we'd be comfortable aboard it." "We'd go closer and closer to the speed of light until the midpoint of the journey." "Then the spacecraft is turned around and we decelerate at 1 g to the destination." "For most of the trip, the velocity would be close to the speed of light and time would slow down enormously." "By how much?" "Barnard's Star could be reached by such a ship in eight years, ship time." "The center of the Milky Way galaxy in 21 years." "The Andromeda galaxy in 28 years." "Of course, the people left behind on the Earth would see things somewhat differently." "Instead of 21 years to the galaxy they would measure it as 30,000 years." "When we got back very few of our friends would be around to greet us." "In principle, such a journey mounting the decimal points closer and closer to the speed of light would even permit us to circumnavigate the known universe in 56 years, ship time." "We would return tens of billions of years in the far future with the Earth a charred cinder and the sun dead." "Relativistic space flight makes the universe accessible to advanced civilizations but only to those who go on the journey not to those who stay home." "These designs are probably further from the actual interstellar spacecraft of the future than Leonardo's models are from the supersonic transports of the present." "But if we do not destroy ourselves I believe that we will, one day, venture to the stars." "When our solar system is all explored the planets of other stars will beckon." "Space travel and time travel are connected." "To travel fast into space is to travel fast into the future." "We travel into the future, although slowly, all the time." "But what about the past?" "Could we journey into yesterday?" "Many physicists think this is fundamentally impossible that we could not build a device which would carry us backwards into time." "Some say that even if we were to build such a device it wouldn't do much good." "We couldn't significantly affect the past." "For example, suppose you traveled into the past and somehow or other prevented your own parents from meeting." "Why, then you would probably never have been born which is something of a contradiction, isn't it since you are clearly there." "Other people think that the two alternative histories have equal validity that they're parallel threads, skeins of time that they could exist side by side." "The history in which you were never born and the history that you know all about." "Perhaps time itself has many potential dimensions despite the fact that we are condemned to experience only one of those dimensions." "Now, suppose you could go back into the past and really change it by, let's say something like persuading Queen Isabella not to bankroll Christopher Columbus." "Then you would have set into motion a different sequence of historical events which those people you left behind you in our time would never get to know about." "If that kind of time travel were possible then every imaginable sequence of alternative history might in some sense really exist." "Would it be possible for a time traveler to change the course of history in a major way?" "Well, let's think about that." "History consists for the most part of a complex multitude of deeply interwoven threads biological, economic and social forces that are not so easily unraveled." "The ancient Greeks imagined the course of human events to be a tapestry created by three goddesses:" "the Fates." "Random minor events generally have no long-range consequences." "But some which occur at critical junctures may alter the weave of history." "There may be cases where profound changes can be made by relatively trivial adjustments." "The further in the past such an event is, the more powerful its influence." "What if our time traveler had persuaded Queen Isabella that Columbus' geography was wrong?" "Almost certainly, some other European would have sailed to the New World." "There were many inducements:" "The lure of the spice trade, improvements in navigation..." "The discovery of America around 1 500 was inevitable." "Of course, there wouldn't be any postage stamps showing Columbus and the Republic of Colombia would have another name." "But the big picture would have turned out more or less the same." "In order to affect the future profoundly a time traveler has to pick and choose." "He'd probably have to intervene in a number of events which are very carefully selected so he could change the weave of history." "It's a lovely fantasy to explore those other worlds that never were." "If you had H.G. Wells' time machine maybe you could understand how history really works." "If an apparently pivotal person had never lived Paul the Apostle or Peter the Great or Pythagoras how different would the world really be?" "What if the scientific tradition of the ancient Ionian Greeks had prospered and flourished?" "It would have required many social factors at the time to have been different including the common feeling that slavery was right and natural." "But what if that light that had dawned on the eastern Mediterranean some 2500 years ago had not flickered out?" "What if scientific method and experiment had been vigorously pursued 2000 years before the industrial revolution our industrial revolution?" "What if the power of this new mode of thought, the scientific method had been generally appreciated?" "I think we might have saved 1 0 or 20 centuries." "Perhaps the contributions that Leonardo made would have been made 1 000 years earlier and the contributions of Einstein 500 years ago." "Not that it would have been those people who would've made those contributions because they lived only in our timeline." "If the Ionians had won we might by now, I think, be going to the stars." "We might at this moment have the first survey ships returning with astonishing results from Alpha Centauri and Barnard's Star, Sirius and Tau Ceti." "There would now be great fleets of interstellar transports being constructed in Earth orbit small, unmanned survey ships liners for immigrants, perhaps great trading ships to ply the spaces between the stars." "On all these ships there would be symbols and inscriptions on the sides." "The inscriptions, if we looked closely would be written in Greek." "The symbol perhaps, would be the dodecahedron." "And the inscription on the sides of the ships to the stars something like:" ""Starship Theodorus of the Planet Earth."" "If you were a really ambitious time traveler you might not dally with human history or even pause to examine the evolution on Earth." "Instead, you would journey back to witness the origin of our solar system from the gas and dust between the stars." "Five billion years ago an interstellar cloud was collapsing to form our solar system." "Most clumps of matter gravitated towards the center and were destined to form the sun." "Smaller peripheral clumps would become the planets." "Long ago, there was a kind of natural selection among the worlds." "Those on highly elliptical orbits tended to collide and be destroyed but planets in circular orbits tended to survive." "But if events had been a little different the Earth would never have formed and another planet at another distance from the sun would be around." "We owe the existence of our world to random collisions in a long-vanished cloud." "Soon, the central mass became very hot." "Thermonuclear reactions were initiated and the sun turned on flooding the solar system with light." "But the growing smaller lumps would never achieve such high temperatures and would never generate thermonuclear reactions." "They would become the Earth and the other planets heated not from within, but mainly by the distant sun." "The accretion continued until almost all the gas and dust and small worldlets were swept up by the surviving planets." "Our time traveler would witness the collisions that made the worlds." "Except for the comets and asteroids the chaos of the early solar system was reduced to a remarkable simplicity:" "Nine or so principal planets in almost circular orbits and a few dozen moons." "Now, let's take a different look." "If we view the solar system edge on and move the sun off-screen to the left we see that the small terrestrial planets the ones about as massive as Earth, tend to be close to the sun." "The big Jupiter-like planets tend to be much further from the sun." "But is that the way it has to be?" "Computer studies suggest that there may be many similar systems about stars with the terrestrials in close and the Jovian planets further away." "But some systems might have Jovians and terrestrials mixed together." "There may be great worlds like Jupiter looming in other skies." "Rarely, the Jovian planets may form close to the star the terrestrials trailing away towards interstellar space." "Our familiar arrangement of planets is only one, perhaps typical, case in the vast expanse of systems." "Often, one fledgling planet accumulates so much gas and dust that thermonuclear reactions do occur." "It becomes a second sun." "A binary star system has formed." "From most of these worlds, the vistas will be dazzling." "Not one of them will be identical to the Earth." "A few will be hospitable." "Many will appear hostile." "Where there are two suns in the sky every object will cast two shadows." "What wonders are waiting for us on the planets of the nearby stars?" "Are there radically different kinds of worlds unimaginably exotic forms of life?" "Perhaps in another century or two when our solar system is all explored we will also have put our own planet in order." "Then we will set sail for the stars and the beckoning worlds around them." "In that day, our machines and our descendants approaching the speed of light, will skim the light-years leaping ahead through time, seeking new worlds." "Einstein has shown us that it's possible." "We will journey simultaneously to distant planets and to the far future." "Some worlds, like this one will look out onto a vast gaseous nebula the remains of a star that once was and is no longer." "In all those skies, rich and distant and exotic constellations there may be a faint yellow star perhaps barely visible to the naked eye perhaps seen only through the telescope." "The home star of a fleet of interstellar transports exploring this tiny region of the great Milky Way galaxy." "The themes of space and time are intertwined." "Worlds and stars, like people are born, live and die." "The lifetime of a human being is measured in decades." "But the lifetime of the sun is a hundred million times longer." "Matter is much older than life." "Billions of years before the sun and Earth even formed atoms were being synthesized in the insides of hot stars and then returned to space when the stars blew themselves up." "Newly formed planets were made of this stellar debris." "The Earth and every living thing are made of star stuff." "But how slowly, in our human perspective, life evolved from the molecules of the early oceans to the first bacteria." "Evolution is not immediately obvious to everybody because it moves so slowly and takes so long." "How can creatures who live for only 70 years detect events that take 70 million years to unfold?" "Or 4 billion?" "By the time one-celled animals had evolved the history of life on Earth was half over." "Not very far along to us, you might think but by now almost all the basic chemistry of life had been established." "Forget our human time perspective." "From the point of view of a star evolution was weaving intricate new patterns from the star stuff on the planet Earth, and very rapidly." "Most evolutionary lines became extinct." "Many lines became stagnant." "If things had gone a bit differently a small change of climate, say, or a new mutation or the accidental death of a different humble organism the entire future history of life might have been very different." "Maybe the line to an intelligent technological species would have passed through worms." "Maybe the present masters of the planet would have had ancestors who were tunicates." "We might not have evolved." "Someone else, someone very different would be here now in our stead, maybe pondering their origins." "But that's not what happened." "There's a particular sequence of environmental accidents and random mutations in the hereditary material." "One particular timeline for life on Earth in this universe." "As a result, the dominant organisms on the planet today..." "Along the way, many more species became extinct than now exist." "If history had a slightly different weave some of those extinct organisms might have survived and prospered." "But occasionally, a creature thought to have become extinct hundreds of millions of years ago turns out to be alive and well." "The coelacanth, for example." "For 3 1/2 billion years, life had lived exclusively in the water." "But now, in a great breathtaking adventure it took to the land." "But if things had gone a little differently the dominant species might still be in the ocean or developed spaceships to carry them off the planet altogether." "From our ancestors, the reptiles there developed many successful lines including the dinosaurs." "Some were fast, dexterous and intelligent." "A visitor from another world or time might have thought them the wave of the future." "But after nearly 200 million years, they were suddenly all wiped out." "Perhaps it was a great meteorite colliding with the Earth spewing debris into the air, blotting out the sun and killing the plants that the dinosaurs ate." "I wonder when they first sensed that something was wrong." "The successors of the dinosaurs came from the same reptilian stock but they survived the catastrophe that destroyed their cousins." "Again, there were many branches which became extinct." "And had events been a little different those branches might have led to the dominant form today." "For 40 million years, a visitor would not have been impressed by these timid little creatures but they led to all the familiar mammals of today." "And that includes the primates." "About 20 million years ago, a space time traveler might have recognized these guys as promising bright, quick, agile, sociable, curious." "Their ancestors were once atoms made in stars then simple molecules, single cells polyps stuck to the ocean floor fish, amphibians, reptiles, shrews." "But then they came down from the trees and stood upright." "They grew an enormous brain they developed culture, invented tools domesticated fire." "They discovered language and writing." "They developed agriculture." "They built cities and forged metal." "And ultimately, they set out for the stars from which they had come 5 billion years earlier." "We are star stuff which has taken its destiny into its own hands." "The loom of time and space works the most astonishing transformations of matter." "Our own planet is only a tiny part of the vast cosmic tapestry a starry fabric of worlds yet untold." "Those worlds in space are as countless as all the grains of sand on all the beaches of the Earth." "Each of those worlds is as real as ours." "In every one of them, there's a succession of incidents, events, occurrences which influence its future." "Countless worlds, numberless moments an immensity of space and time." "And our small planet, at this moment here, we face a critical branchpoint in history." "What we do with our world right now will propagate down through the centuries and powerfully affect the destiny of our descendants." "It is well within our power to destroy our civilization and perhaps our species as well." "If we capitulate to superstition or greed or stupidity we can plunge our world into a darkness deeper than the time between the collapse of classical civilization and Italian Renaissance." "But we are also capable of using our compassion and our intelligence our technology and our wealth to make an abundant and meaningful life for every inhabitant of this planet to enhance enormously our understanding of the universe and to carry us to the stars." "In our motorbike sequence we showed how the landscape might look if we barreled through it at close to light speed." "Since then, inspired by this sequence Ping-Kang Hsiung at Carnegie Mellon University produced an exact computer animation." "This is what you'd see if you traveled at ordinary speeds through this red and white lattice." "But this is how it would appear if you were traveling at close to the speed of light." "We're probably many centuries away from traveling close to light speed and experiencing time dilation." "But even then, it might not be fast enough if we wanted to travel to some distant place in the galaxy and then come back to Earth in our own epoch." "Some years after completing Cosmos I took time out from my scientific work to write a novel." "A novel about travel to the center of the Milky Way galaxy." "I was willing to imagine beings and civilizations far more advanced than we but I wasn't willing to ignore the laws of physics." "Was there, even in principle, a way to get very quickly to 30,000 light-years from Earth?" "So I asked my friend Kip Thorne of the California Institute of Technology." "He's a leading expert on the nature of space and time." "Kip thought about it for a while and then answered with about 50 lines of equations which showed that a really advanced civilization might establish and hold open wormholes which we might think of as tubes through the fourth dimension which connect the Earth with another place without having to traverse the intervening distance." "Something like crawling through a wormhole in an apple." "I was happy with this result and used it as a key plot device in Contact." "But such wormholes through space would also be time machines, it seemed to me." "And I used that notion in my novel Contact as well." "Kip Thorne and his colleagues later proved, or so it seemed that time travel of this sort was possible." "Here, look at this." "The key question being explored now is whether such time travel can be done consistently with causes preceding effects, say, rather than following them." "Does nature contrive it so that even with a time machine, you can't intervene to prevent your own conception, for example?" "Even if time travel of this sort is really possible it's far in our technological future." "But maybe other beings much more advanced than we are voyaging to the far future and the remote past not a measly 40 years ago on Earth but to witness the death of the sun, say or the origin of the cosmos." "In the year 1905." "The record for the most distant quasar is now more like 12 million light-years." "In fact, many of the recently discovered extrasolar systems have Jovian planets close to the star." "Any terrestrial planets would still be too small and dim to detect with existing techniques."