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Ballantine Books Edition, September 1997 ISBN: 0-345-37659- Scanned: December, 2000 V.1. Formatted for viewing in Word 97
CARL SAGAN
PALE BLUE DOT
A V I S I O N O F T H E
H U M A N F U T UR E I N S PA C E
F O R S A M
Another wanderer, May your generation see Wonders undreamt.
SPACECRAFT EXPLORATION
OF THE SOLAR SYSTEM
NOTABLE EARLY ACHIEVEMENTS
UNITED STATES
1958 First scientific discovery in space-Van Allen radiation belt (Explorer 1) 1959 First television images of the Earth from space (Explorer 6) 1962 First scientific discovery in interplanetary space -direct observation of the solar wind (Mariner 2) 1962 First scientifically successful planetary mission (Mariner 2 to Venus) 1962 First astronomical observatory in space (OSO-1 ) 1968 First manned orbit of another world ( Apollo 8 to the Moon) 1969 First landing of humans on another world ( Apollo 11 to the Moon) 1969 First samples returned to Earth from another world ( Apollo 11 to the Moon) 1971 First manned roving vehicle on another world ( Apollo 15 to the Moon) 1971 First spacecraft to orbit another planet (Mariner 9 to Mars) 1973 First flyby of Jupiter (Pioneer 10) 1974 First dual-planet mission (Mariner 10 to Venus and Mercury) 1974 First flyby of Mercury (Mariner 10) 1976 First successful Mars landing; first spacecraft to search for life on another planet (Viking 1) 1977 First flybys of Saturn (Pioneer 11) 1981 First manned reusable spacecraft (STS-1) 1980- First satellite to be retrieved, repaired, 1984 and redeployed in space (Solar Maximum Mission) 1985 First distant cometary encounter (International Cometary Explorer to Comet Giacobini-Zimmer) 1986 First flyby of Uranus (Voyager 2) 1989 First flyby of Neptune (Voyager 2) 1992 First detection of the heliopause (Voyager) 1992 First encounter with a main-belt asteroid (Galileo to Gaspra)
CONTENTS
- WANDERERS: AN INTRODUCTION
- YOU ARE HERE
- ABERRATIONS OF LIGHT
- THE GREAT DEMOTIONS
- A UNIVERSE NOT MADE FOR US
- IS THERE INTELLIGENT LIFE ON EARTH?
- THE TRIUMPH OF VOYAGER
- AMONG THE MOONS OF SATURN
- THE FIRST NEW PLANET
- AN AMERICAN SHIP AT THE FRONTIERS OF THE SOLAR SYSTEM
- SACRED BLACK
- EVENING AND MORNING STAR
- THE GROUND MELTS
- THE GIFT OF APOLLO
- EXPLORING OTHER WORLDS AND PROTECTING THIS ONE
- THE GATES OF THE WONDER WORLD OPEN
- SCALING HEAVEN
- ROUTINE INTERPLANETARY VIOLENCE
- THE MARSH OF CAMARINA
- REMAKING THE PLANETS
- DARKNESS
- TO THE SKY!
- TIPTOEING THROUGH THE MILKY WAY
- ABOUT THE AUTHOR
- ACKNOWLEDGMENTS
- REFERENCES
WANDERERS:
AN INTRODUCTION But tell me, who are they, these wanderers.. .? —RAINER MARIA RILKE, "THE FIFTH ELEGY" (1923)
W e were wanderers from the beginning. We knew every stand of tree for a hundred miles. When the fruits or nuts were ripe, we were there. We followed the herds in their annual migrations. We rejoiced in fresh meat. through stealth, feint, ambush, and main-force assault, a few of us cooperating accomplished what many of us, each hunting alone, could not. We depended on one another. Making it on our own was as ludicrous to imagine as was settling down. Working together, we protected our children from the lions and the hyenas. We taught them the skills they would need. And the tools. Then, as now, technology was the key to our survival. When the drought was prolonged, or when an unsettling chill lingered in the summer air, our group moved on—sometimes to unknown lands. We sought a better place. And when we couldn't get on with the others in our little nomadic band, we left to find a more friendly bunch somewhere else. We could always begin again. For 99.9 percent of the time since our species came to be, we were hunters and foragers, wanderers on the savannahs and the steppes. There were no border guards then, no customs officials. The frontier was everywhere. We were bounded only by the Earth and the ocean and the sky—plus occasional grumpy neighbors. When the climate was congenial, though, when the food was plentiful, we were willing to stay put. Unadventurous. Overweight. Careless. In the last ten thousand years—an instant in our long history— we've abandoned the nomadic fife. We've domesticated the plants and animals. Why chase the food when you can make it come to you? For all its material advantages, the sedentary life has left us edgy, unfulfilled. Even after 400 generations in villages and cities, we haven't forgotten. The open road still softly calls, like a nearly forgotten song of childhood. We invest far-off places with a certain romance. This appeal, I suspect, has been meticulously crafted by natural selection as an essential element in our survival. Long summers, mild winters, rich harvests, plentiful game—none of them lasts forever. It is beyond our powers to predict the future. Catastrophic events have a way of sneaking up on us, of catching us unaware. Your own life, or your band's, or even your species' might be owed to a restless few—drawn, by a craving they can hardly articulate or understand, to undiscovered lands and new worlds. Herman Melville, in Moby Dick, spoke for wanderers in all epochs and meridians: "I am tormented with an everlasting itch for things remote. I love to sail forbidden seas.. ." To the ancient Greeks and Romans, the known world comprised Europe and an attenuated Asia and Africa, all surrounded by an impassable World Ocean. Travelers might encounter
LATE IN THE NINETEENTH CENTURY , Leib Gruber was growing up 111 Central Europe, in an obscure town in the immense, polyglot, ancient Austro-Hungarian Empire. His father sold fish when he could. But times were often hard. As a young man, the only honest employment Leib could find was carrying people across the nearby river Bug. The customer, male or female, would mount Leib's back; in his prized boots, the tools of his trade, he would wade out in a shallow stretch of the river and deliver his passenger to the opposite bank. Sometimes the water reached his waist. There were no bridges here, no ferryboats. Horses might have served the purpose, but they had other uses. That left Leib and a few other young men like him. They had no other uses. No other work was available. They would lounge about the riverbank, calling out their prices, boasting to potential customers about the superiority of their drayage. They hired themselves out like four-footed animals. My grandfather was a beast of burden I don't think that in all his young manhood Leib had ventured more than a hundred kilometers from his little hometown of Sassow. But then, in 1904, he suddenly ran away to the New World to avoid a murder rap, according to one family legend. He left his young wife behind. How different from his tiny back-water hamlet the great German port cities must have seemed, how vast the ocean, how strange the lofty skyscrapers and endless hub-bub of his new land. We know nothing of his crossing, but have found the ship's manifest for the journey undertaken later by his wife, Chaiya joining Leib after he had saved enough to bring her over. She traveled in the cheapest class on the Batavia, a vessel of Hamburg registry. There's something heartbreakingly terse about the document: Can she read or write? No. Can she speak English? No. How much money does she have? I can imagine her vulnerability and her shame as she replies, "One dollar." She disembarked in New York, was reunited with Leib, lived just long enough to give birth to my mother and her sister, and then died from "complications" of childbirth. In those few years in America, her name had sometimes been anglicized to Clara. A quarter century later, my mother named her own firstborn, a son, after the mother she never knew.
OUR DISTANT ANCESTORS , watching the stars, noted five that did more than rise and set in stolid procession, as the so-called "fixed" stars did. These five had a curious and complex motion. Over the months they seemed to wander slowly among the stars. Sometimes they did loops. Today we call them planets, the Greek word for wanderers. It was, I imagine, a peculiarity our ancestors could relate to. We know now that the planets are not stars, but other worlds, gravitationally lashed to the Sun. Just as the exploration of the Earth was being completed, we began to recognize it as one world among an uncounted multitude of others, circling the Sun or orbiting the other stars that make up the Milky Way galaxy. Our planet and our solar system are surrounded by a new world ocean the depths of space. It is no more impassable than the last. Maybe it's a little early. Maybe the time is not quite yet. But those other worlds— promising untold opportunities—beckon. In the last few decades, the United States and the former Soviet Union have accomplished something stunning and historic—the close-up examination of all those points of light, from Mercury to Saturn, that moved our ancestors to wonder and to science. Since the advent of successful interplanetary flight in 1962, our machines have flown by, orbited, or landed
on more than seventy new worlds. We have wandered among the wanderers. We have found vast volcanic eminences that dwarf the highest mountain on Earth; ancient river valleys on two planets enigmatically one too cold and the other too hot for running water; a giant planet with an interior of liquid metallic hydrogen into which a thousand Earths would fit; whole moons that have melted; a cloud-covered place with an atmosphere of corrosive raids, where even the high plateaus are above the melting point of lead ancient surfaces on which a faithful record of the violent formation of the Solar System is engraved; refugee ice worlds from the transplutonian depths; exquisitely patterned ring systems, marking the subtle harmonies of gravity; and a world surrounded by clouds of complex organic molecules like those that m the earliest history of our planet led to the origin of life. Silently, they orbit the Sun, waiting. We have uncovered wonders undreamt by our ancestors who first speculated on the nature of those wandering lights in the night sky. We have probed the origins of our planet and ourselves. By discovering what else is possible, by coming face to face with alternative fates of worlds more or less like our own, we have begun to better understand the Earth. Every one of these worlds is lovely and instructive. But, so far as we know, they are also, every one of them, desolate and barren. Out there, there are no "better places." So far, at least. During the Viking robotic mission, beginning in July 1976, in a certain sense I spent a year on Mars. I examined the boulders and sand dunes, the sky red even at high noon, the ancient river valleys, the soaring volcanic mountains, the fierce wind erosion, the laminated polar terrain, the two dark potato-shaped moons. But there was no life—not a cricket or a blade of grass, or even, so far as we can tell for sure, a microbe. These worlds have not been graced, as ours has, by life. Life is a comparative rarity. You can survey dozens of worlds and find that on only one of them does life arise and evolve and persist. Having in all their lives till then crossed nothing wider than a layer, Leib and Chaiya graduated to crossing oceans. They had one great advantage: On the other side of the waters there would be-invested with outlandish customs, it is true—other human beings speaking their language and sharing at least some of their values, even people to whom they were closely related. In our time we've crossed the Solar System and sent four ships to the stars. Neptune lies a million times farther from Earth than New York City is from the banks of the Bug. But there are no distant relatives, no humans, and apparently no life waiting for us on those other worlds. No letters conveyed by recent émigrés help us to understand the new land— only digital data transmitted at the speed of light by unfeeling, precise robot emissaries. They tell us that these new worlds are not much like home. But we continue to search for inhabitants. We can't help it. Life looks for life. No one on Earth, not the richest among us, can afford the passage; so we can't pick up and leave for Mars or Titan on a whim, or because we're bored, or out of work, or drafted into the army, or oppressed, or because, justly or unjustly, we've been accused of a crime. There does not seem to be sufficient short-term profit to motivate private industry. If we humans ever go to these worlds, then, it will be because a nation or a consortium of them believes it to be to its advantage—or to the advantage of the human species. Just now, there are a great many matters pressing in on us that compete for the money it takes to send people to other worlds.
C H A P T E R 1
YOU ARE HERE
The entire Earth is but a point, and the place of our own habitation but a minute corner of it. —MARCUS AURELIUS, ROMAN EMPEROR, MEDITATIONS , BOOK 4 (CA. 170) As the astronomers unanimously teach, the circuit of the whole earth, which to us seems endless, compared with the greatness of the universe has the likeness of a mere tiny point. —AMMIANUS MARCELLINUS ACA. 330-395, THE LAST MAJOR ROMAN HISTORIAN, IN THE CHRONICLE OF EVENTS
T he spacecraft was a long way from home, beyond the orbit of the outermost planet and high
above the ecliptic plane—which is an imaginary flat surface that we can think of as something like a racetrack in which the orbits of the planets are mainly confined. The ship was speeding away from the Sun at 40,000 miles per hour. But in early February of 1990, it was overtaken by an urgent message from Earth. Obediently, it turned its cameras back toward the now-distant planets. Slewing its scan platform from one spot in the sky to another, it snapped 60 pictures and stored them in digital form on its tape recorder. Then, slowly, in March, April, and May, it radioed the data back to Earth. Each image was composed of 640,000 individual picture elements ("pixels"), like the dots in a newspaper wire-photo or a pointillist painting. The spacecraft was 3.7 billion miles away from Earth, so far away that it took etch pixel 5½ hours, traveling at the speed of light, to reach us. The pictures might have been returned earlier, but the big radio telescopes in California, Spain, and Australia that receive these whispers from the edge of the Solar System had responsibilities to other ships that ply the sea of space among them, Magellan, bound for Venus, and Galileo on its tortuous passage to Jupiter. Voyager 1 was so high above the ecliptic plane because, in 1981, it had made a close pass by Titan, the giant moon of Saturn. Its sister ship, Voyager 2 , was dispatched on a different trajectory, within the ecliptic plane, and so she was able to perform her celebrated explorations of Uranus and Neptune The two Voyager robots have explored four planets and nearly sixty moons. They are triumphs of human engineering an. one of the glories of the American space program. They will he in the history books when much else about our time forgotten. The Voyagers were guaranteed to work only until the Saturn encounter. I thought it might be a good idea, just after Saturn, to have them take one last glance homeward. From Saturn, I knew the Earth would appear too small for Voyager to make out any detail. Our planet would be just a point of light, a lonely pixel, hardly distinguishable from the many other points of light Voyager could see, nearby planets and far-off suns. But precise because of the obscurity of our world thus revealed, such picture might be worth having.
Mariners had painstakingly mapped the coastlines of the continents. Geographers had translated these findings into charts and globes. Photographs of tiny patches of the Earth had been obtained first by balloons and aircraft, then by rockets in brief ballistic flight, and at last by orbiting spacecraft—giving a perspective like the one you achieve by positioning your eyeball about an inch above a large globe. While almost everyone is taught that the Earth is a sphere with all of us somehow glued to it by gravity, the reality of our circumstance did not really begin to sink in until the famous frame-filling Apollo photograph of the whole Earth—the one taken by the Apollo 17 astronauts on the last journey of humans to the Moon. It has become a kind of icon of our age. There's Antarctica at what Americans and Europeans so readily regard as the bottom, and then all of Africa stretching up above it: You can see Ethiopia, Tanzania, and Kenya, where the earliest humans lived. At top right are Saudi Arabia and what Europeans call the Near East. Just barely peeking out at the top is the Mediterranean Sea, around which so much of our global civilization emerged. You can make out the blue of the ocean, the yellow-red of the Sahara and the Arabian desert, the brown-green of forest and grassland. And yet there is no sign of humans in this picture, not our reworking of the Earth's surface, not our machines, not ourselves: We are too small and our statecraft is too feeble to be seen by a spacecraft between the Earth and the Moon. From this vantage point, our obsession with nationalism is nowhere in evidence. The Apollo pictures of the whole Earth conveyed to multitudes something well known to astronomers: On the scale of worlds—to say nothing of stars or galaxies—humans are inconsequential, a thin film of life on an obscure and solitary lump of rock and metal. It seemed to me that another picture of the Earth, this one taken from a hundred thousand times farther away, might help in the continuing process of revealing to ourselves our true circumstance and condition. It had been well understood by the scientists and philosophers of classical antiquity that the Earth was a mere point in a vast encompassing Cosmos, but no one had ever seen it as such. Here was our first chance (and perhaps also our last for decades to come). Many in NASA's Voyager Project were supportive. But from the outer Solar System the Earth lies very near the Sun, like a moth enthralled around a flame. Did we want to aim the camera so close to the Sun as to risk burning out the spacecraft's vidicon system? Wouldn't it be better to delay until all the scientific images from Uranus and Neptune, if the spacecraft lasted that long, were taken? And so we waited— and a good thing too—from 1981 at Saturn, to 1986 at Uranus, to 1989, when both spacecraft had passed the orbits of Neptune and Pluto. At last the time came But there were a few instrumental calibrations that needed to be done first, and we waited a little longer. Although the spacecraft were in the right spots, the instruments were still working beautifully, and there were no other pictures to take, a few project personnel opposed it. It wasn't science, they said. Then we discovered that the technicians who devise and transmit the radio commands to Voyager were, in a cash-strapped NASA, to be laid off immediately or transferred to other jobs. If the picture were to be taken, it had to be done right then. At the last minute actually, in the midst of the Voyager 2 encounter with Neptune, the then NASA Administrator, Rear Admiral Richard Truly, stepped in and made sure that these images were obtained. The space scientists Candy Hansen of NASA's Jet Propulsion Laboratory (JPL) and Carolyn Porco of
The Earth is a very small stage in a vast cosmic arena. Think of the rivers of blood spilled by all those generals and emperors so that, in glory and triumph, they could become momentary masters of a fraction of a dot. Think of the endless visited by the inhabitants of one corner of this pixel the scarcely distinguishable inhabitants of some other corner, how frequent their misunderstandings, how eager they are to kill one another, how fervent their hatreds. Our posturings, our imagined self-importance, the delusion that we have some privileged position in the Universe, are challenged by this point of pale light. Our planet is a lonely speck in the great enveloping cosmic dark. In our obscurity, in all this vastness, there is no hint that help will come from elsewhere to save us from ourselves. The Earth is the only world known so far to harbor life. There is nowhere else, at least in the near future, to which our species could migrate. Visit, yes. Settle, not yet. Like it or not, for the moment the Earth is where we make our stand. It has been said that astronomy is a humbling and character-building experience. There is perhaps no better demonstration of the folly of human conceits than this distant image of our tiny world. To me, it underscores our responsibility to deal more kindly with one another, and to preserve and cherish the pale blue dot, the only home we've ever known.
C H A P T E R 2
ABBERATIONS
OF LIGHT
If man were taken away from the world, the rest would seem to be all astray, without aim or purpose... and to be leading to nothing. —FRANCIS BACON , WISDOM OF THE ANCIENTS (1619)
A nn Druyan suggests an experiment: Look back again at the pale blue dot of the preceding
chapter. Take a good long look at it. Stare at the dot for any length of time and then try to convince yourself that God created the whole Universe for one of the 10 million or so species of life that inhabit that speck of dust. Now take it a step further: Imagine that everything was made just for a single shade of that species, or gender, or ethnic or religious subdivision. If this doesn't strike you as unlikely, pick another dot. Imagine it to be inhabited by a different form of intelligent life. They, too, cherish the notion of a God who has created everything for their benefit. How seriously do you take their claim?
“SEE THAT STAR?" "You mean the bright red one?" his daughter asks in return. "Yes. You know, it might not be there anymore. It might be gone by now—exploded or something. Its light is still crossing space, just reaching our eyes now. But we don't see it as it is. We see it as it was." Many people experience a stirring sense of wonder when they first confront this simple truth. Why? Why should it be so compelling? On our little world light travels, for all practical purposes, instantaneously. If a lightbulb is glowing, then of course it's physically where we see it, shining away. We reach out our hand and touch it: It's there all right, and unpleasantly hot. If the filament fails, then the light goes out. We don't see it in the same place, glowing, illuminating the room years after the bulb breaks and it's removed from its socket. The very notion seems nonsensical. But if we're far enough away, an entire sun can go out and we'll continue to see it shining brightly; we won't learn of its death, it may be, for ages to come—in fact, for how long it takes light, which travels fast but not infinitely fast, to cross the intervening vastness. The immense distances to the stars and the galaxies mean that we see everything in space in the past—some as they were before the Earth came to be. Telescopes are time machines. Long ago, when an early galaxy began to pour light out into the surrounding darkness, no witness could have known that billions of years later some remote clumps of rock and metal, ice and organic molecules would fall together to make a place called Earth; or that life would arise and thinking
It was doubtless the view of our foraging and hunting ancestors. The great astronomer of antiquity, Claudius Ptolemaeus (Ptolemy), in the second century knew that the Earth was a sphere, knew that its size was "a point" compared to the distance of the stars, and taught that it lay "right in the middle of the heavens." Aristotle, Plato, St. Augustine, St. Thomas Aquinas, and almost all the great philosophers and scientists of all cultures over the 3,000 years ending in the seventeenth century bought into this delusion. Some busied themselves figuring out how the Sun, the Moon, the stars, and the planets could be cunningly attached to perfectly transparent, crystalline spheres—the big spheres, of course, centered on the Earth—that would explain the complex motions of the celestial bodies so meticulously chronicled by generations of astronomers. And they succeeded: With later modifications, the geocentric hypothesis adequately accounted for the facts of planetary motion as known in the second century, and in the sixteenth. From there it was only a slight extrapolation to an even more grandiose claim—that the "perfection" of the world would be incomplete without humans, as Plato asserted in the Timaeus. "Man... is all," the poet and cleric John Donne wrote in 1625. "He is not a piece of the world, but the world itself; and next to the glory of God, the reason why there is a world." And yet—never mind how many kings, popes, philosophers, scientists, and poets insisted on the contrary—the Earth through those millennia stubbornly persisted in orbiting the Sun. You might imagine an uncharitable extraterrestrial observer looking down on our species over all that time—with us excitedly chattering, "The Universe is created for us! We're at the center! Everything pays homage to us!"—and concluding that our pretensions are amusing, our aspirations pathetic, that this must be the planet of the idiots. But such a judgment is too harsh. We did the best we could. There was an unlucky coincidence between everyday appearances and our secret hopes. We tend not to be especially critical when presented with evidence that seems to confirm our prejudices. And there was little countervailing evidence. In muted counterpoint, a few dissenting voices, counseling humility and perspective, could be heard down through the centuries. At the dawn of science, the atomist philosophers of ancient Greece and Rome— those who first suggested that matter is made of atoms—Democritus, Epicurus, and their followers (and Lucretius, the first popularizer of science) scandalously proposed many worlds and many alien life forms, all made of the same kinds of atoms as we. They offered for our consideration infinities in space and time. But in the prevailing canons of the West, secular and sacerdotal, pagan and Christian, atomist ideas were reviled. Instead, the heavens were not at all like our world. They were unalterable and "perfect." The Earth was mutable and "corrupt." The Roman statesman and philosopher Cicero summarized the common view: "In the heavens... there is nothing of chance or hazard, no error, no frustration, but absolute order, accuracy, calculation and regularity." Philosophy and religion cautioned that the gods (or God) were far more powerful than we, jealous of their prerogatives and quick to mete out justice for insufferable arrogance. At the same time, these disciplines had not a clue that their own teaching of how the Universe is ordered was a conceit and a delusion. Philosophy and religion presented mere opinion—opinion that might be overturned by observation and experiment—as certainty. This worried them not at all. That some of their deeply held beliefs might turn out to be mistakes was a possibility hardly considered. Doctrinal humility
was to be practiced by others. Their own teachings were inerrant and Infallible. In truth, they had better reason to be humble than they knew.
BEGINNING WITH COPERNICUS in the middle sixteenth century, the issue was formally joined. The picture of the Sun rather than the Earth at the center of the Universe was understood to be dangerous. Obligingly, many scholars were quick to assure the religious hierarchy that this newfangled hypothesis represented no serious challenge to conventional wisdom. In a kind of split-brain compromise, the Sun-centered system was treated as a mere computational convenience, not an astronomical reality that is, the Earth was really at the center of the Universe, as everybody knew; but if you wished to predict where Jupiter would be on the second Tuesday of November the year after next, you were permitted to pretend that the Sun was at the center. Then you could calculate away and not affront the Authorities.* "This has no danger in it," wrote Robert Cardinal Bellarmine, the foremost Vatican theologian in the early seventeenth century,
and suffices for the mathematicians. But, to affirm that the Sun is really fixed in the center of the heavens and that the Earth revolves very swiftly around the Sun is a dangerous thing, not only irritating the theologians and philosophers, but injuring our holy faith and making the sacred scripture false."
"Freedom of belief is pernicious," Bellarmine wrote on another occasion. "It is nothing but the freedom to be wrong." Besides, if the Earth was going around the Sun, nearby stars should seem to move against the background of more distant stars as, every six months, we shift our perspective from one side of the Earth's orbit to the other. No such "annual parallax" had been found. The Copernicans argued that this was because the stars were extremely far away—maybe a million times more distant than the Earth is from the Sun. Perhaps better telescopes, in future times, would find an annual parallax. The geocentrists considered this a desperate attempt to save a flawed hypothesis, and ludicrous on the face of it. When Galileo turned the first astronomical telescope to the sky, the tide began to turn. He discovered that Jupiter had a little retinue of moons circling it, the inner ones orbiting faster than the outer ones, just as Copernicus had deduced for the motion of the planets about the Sun. He found that Mercury and Venus went through phases like the Moon (showing they orbited the Sun). Moreover, the cratered Moon and the spotted Sun challenged the perfection of the heavens. This may in part constitute the sort of trouble Tertullian was worried about thirteen hundred years earlier, when he pleaded, "If you have any sense or modesty, have done with prying into the regions of the sky, into the destiny and secrets of the universe."
- (^) Copernicus' famous book was first published with an introduction by the theologian Andrew Osiander, inserted without the knowledge of the dying astronomer. Osiander's well-meaning attempt to reconcile religion and Copernican astronomy ended with these words: "[L]et no one expect anything in the way of certainty of astronomy, since astronomy can offer us nothing certain, lest, if anyone take as true that which has been constructed for .mother use, he go away from this discipline a bigger fool than w hen he cane to it." Certainty could be found only in religion.
say, their instruments do not hear a tinkling sound or detect shards of broken crystal as they crash through the "spheres" that—according to the authoritative opinions that prevailed for millennia— propel Venus or the Sun ill their dutiful motions about the central Earth. When Voyager 1 scanned the Solar System from beyond the outermost planet, it saw, just as Copernicus and Galileo had said we would, the Sun in the middle and the planets in concentric orbits about it. Far from being the center of the Universe, the Earth is just one of the orbiting dots. No longer confined to a single world, we are now able to reach out to others and determine decisively what kind of planetary system we inhabit.
EVERY OTHER PROPOSAL , and their number is legion, to displace us from cosmic center stage has also been resisted, in part for similar reasons. We seem to crave privilege, merited not by our work, but by our birth, by the mere fact that, say, we are humans and born on Earth. We might call it the anthropocentric—the "human-centered"—conceit. This conceit is brought close to culmination in the notion that we are created in God's image: The Creator and Ruler of the entire Universe looks just like me. My, what a coincidence How convenient and satisfying! The sixth-century-B.C. Green philosopher Xenophanes understood the arrogance of the perspective:
"The Ethiopians make their gods black and snub-nosed; the Thracians say theirs have blue eyes and red hair... Yes, and if oxen and horses or lions had hands, and could paint with their hands, and produce works of art as men do, horses would paint the forms of the gods like horses, and oxen like oxen.. ."
Such attitudes were once described as "provincial"—the naive expectation that the political hierarchies and social conventions of an obscure province extend to a vast empire composed of many different traditions and cultures; that the familiar boondocks, our boondocks, are the center of the world. The country bumpkins know almost nothing about what else is possible. They fail to grasp the insignificance of their province or the diversity of the Empire. With ease, they apply their own standards and customs to the rest of the planet. But plopped down in Vienna, say, or Hamburg, or New York, ruefully they recognize how limited their perspective has been. They become "deprovincialized." Modern science has been a voyage into the unknown, with a lesson in humility waiting at every stop. Many passengers would rather have stayed home.
C H A P T E R 3
THE
GREAT
DEMOTIONS
[One philosopher] asserted that he knew the whole secret... [H]e surveyed the two celestial strangers from top to toe, and maintained to their faces that their persons, their worlds, their suns, and their stars, were created solely for the use of man. At this assertion our two travelers let themselves fall against each other, seized with a fit of... inextinguishable laughter. --VOLTAIRE, MICROMEGAS. A PHILOSOPHICAL HISTORY (1752)
I n the seventeenth century there was still some hope that, even if the Earth was not the center of
the Universe, it might be the only "world." But Galileo's telescope revealed that "the Moon certainly does not possess a smooth and polished surface" and that other worlds might look "just like the face of the Earth itself." The Moon and the planets showed unmistakably that they had as much claim to being worlds as the Earth does—with mountains, craters, atmospheres, polar ice caps, clouds, and, in the case of Saturn, a dazzling, unheard-of set of circumferential rings. After millennia of philosophical debate, the issue was settled decisively in favor of "the plurality of worlds." They might be profoundly different from our planet. None of them might be as congenial for life. But the Earth was hardly the only one. This was the next in the series of Great Demotions, downlifting experiences, demonstrations of our apparent insignificance, wounds that science has, in its search for Galileo's facts, delivered to human pride.
WELL, SOME HOPED , even if the Earth isn't at the center of the Universe, the Sun is. The Sun is our Sun. So the Earth is approximately at the center of the Universe. Perhaps some of our pride could in this way be salvaged. But by the nineteenth century, observational astronomy had made it clear that the Sun is but one lonely star in a great self-gravitating assemblage of suns called the Milky Way Galaxy. Far from being at the center of the Galaxy, our Sun with its entourage of dim and tiny planets lies in an undistinguished sector of an obscure spiral arm. We are thirty thousand light years from the Center. Well, our Milky Way is the only galaxy. The Milky Way Galaxy is one of billions, perhaps hundreds of billions of galaxies notable neither in mass nor in brightness nor in how its stars are configured and arrayed. Some modern deep sky photographs show more galaxies beyond the Milky Way than stars within the Milky Way. Every one of them is an island universe containing perhaps a hundred billion suns. Such an image is a profound sermon on humility.
