by Carl Sagan
We, the nuclear hostages—all the peoples of the Earth—must educate ourselves about conventional and nuclear warfare. Then we must educate our governments. We must learn the science and technology that provide the only conceivable tools for our survival. We must be willing to challenge courageously the conventional social, political, economic and religious wisdom. We must make every effort to understand that our fellow humans, all over the world, are human. Of course, such steps are difficult. But as Einstein many times replied when his suggestions were rejected as impractical or as inconsistent with “human nature”: What is the alternative?
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Mammals characteristically nuzzle, fondle, hug, caress, pet, groom and love their young, behavior essentially unknown among the reptiles. If it is really true that the R-complex and limbic systems live in an uneasy truce within our skulls and still partake of their ancient predelictions, we might expect affectionate parental indulgence to encourage our mammalian natures, and the absence of physical affection to prod reptilian behavior. There is some evidence that this is the case. In laboratory experiments, Harry and Margaret Harlow found that monkeys raised in cages and physically isolated—even though they could see, hear and smell their simian fellows—developed a range of morose, withdrawn, self-destructive and otherwise abnormal characteristics. In humans the same is observed for children raised without physical affection—usually in institutions—where they are clearly in great pain.
The neuropsychologist James W. Prescott has performed a startling cross-cultural statistical analysis of 400 preindustrial societies and found that cultures that lavish physical affection on infants tend to be disinclined to violence. Even societies without notable fondling of infants develop nonviolent adults, provided sexual activity in adolescents is not repressed. Prescott believes that cultures with a predisposition for violence are composed of individuals who have been deprived—during at least one of two critical stages in life, infancy and adolescence—of the pleasures of the body. Where physical affection is encouraged, theft, organized religion and invidious displays of wealth are inconspicuous; where infants are physically punished, there tends to be slavery, frequent killing, torturing and mutilation of enemies, a devotion to the inferiority of women, and a belief in one or more supernatural beings who intervene in daily life.
We do not understand human behavior well enough to be sure of the mechanisms underlying these relationships, although we can conjecture. But the correlations are significant. Prescott writes: “The percent likelihood of a society becoming physically violent if it is physically affectionate toward its infants and tolerant of premarital sexual behavior is 2 percent. The probability of this relationship occurring by chance is 125,000 to one. I am not aware of any other developmental variable that has such a high degree of predictive validity.” Infants hunger for physical affection; adolescents are strongly driven to sexual activity. If youngsters had their way, societies might develop in which adults have little tolerance for aggression, territoriality, ritual and social hierarchy (although in the course of growing up the children might well experience these reptilian behaviors). If Prescott is right, in an age of nuclear weapons and effective contraceptives, child abuse and severe sexual repression are crimes against humanity. More work on this provocative thesis is clearly needed. Meanwhile, we can each make a personal and noncontroversial contribution to the future of the world by hugging our infants tenderly.
If the inclinations toward slavery and racism, misogyny and violence are connected—as individual character and human history, as well as cross-cultural studies, suggest—then there is room for some optimism. We are surrounded by recent fundamental changes in society. In the last two centuries, abject slavery, with us for thousands of years or more, has been almost eliminated in a stirring planet-wide revolution. Women, patronized for millennia, traditionally denied real political and economic power, are gradually becoming, even in the most backward societies, equal partners with men. For the first time in modern history, major wars of aggression were stopped partly because of the revulsion felt by the citizens of the aggressor nations. The old exhortations to nationalist fervor and jingoist pride have begun to lose their appeal. Perhaps because of rising standards of living, children are being treated better worldwide. In only a few decades, sweeping global changes have begun to move in precisely the directions needed for human survival. A new consciousness is developing which recognizes that we are one species.
“Superstition [is] cowardice in the face of the Divine,” wrote Theophrastus, who lived during the founding of the Library of Alexandria. We inhabit a universe where atoms are made in the centers of stars; where each second a thousand suns are born; where life is sparked by sunlight and lightning in the airs and waters of youthful planets; where the raw material for biological evolution is sometimes made by the explosion of a star halfway across the Milky Way; where a thing as beautiful as a galaxy is formed a hundred billion times—a Cosmos of quasars and quarks, snowflakes and fireflies, where there may be black holes and other universes and extraterrestrial civilizations whose radio messages are at this moment reaching the Earth. How pallid by comparison are the pretensions of superstition and pseudoscience; how important it is for us to pursue and understand science, that characteristically human endeavor.
Every aspect of Nature reveals a deep mystery and touches our sense of wonder and awe. Theophrastus was right. Those afraid of the universe as it really is, those who pretend to nonexistent knowledge and envision a Cosmos centered on human beings will prefer the fleeting comforts of superstition. They avoid rather than confront the world. But those with the courage to explore the weave and structure of the Cosmos, even where it differs profoundly from their wishes and prejudices, will penetrate its deepest mysteries.
There is no other species on Earth that does science. It is, so far, entirely a human invention, evolved by natural selection in the cerebral cortex for one simple reason: it works. It is not perfect. It can be misused. It is only a tool. But it is by far the best tool we have, self-correcting, ongoing, applicable to everything. It has two rules. First: there are no sacred truths; all assumptions must be critically examined; arguments from authority are worthless. Second: whatever is inconsistent with the facts must be discarded or revised. We must understand the Cosmos as it is and not confuse how it is with how we wish it to be. The obvious is sometimes false; the unexpected is sometimes true. Humans everywhere share the same goals when the context is large enough. And the study of the Cosmos provides the largest possible context. Present global culture is a kind of arrogant newcomer. It arrives on the planetary stage following four and a half billion years of other acts, and after looking about for a few thousand years declares itself in possession of eternal truths. But in a world that is changing as fast as ours, this is a prescription for disaster. No nation, no religion, no economic system, no body of knowledge, is likely to have all the answers for our survival. There must be many social systems that would work far better than any now in existence. In the scientific tradition, our task is to find them.
Only once before in our history was there the promise of a brilliant scientific civilization. Beneficiary of the Ionian Awakening, it had its citadel at the Library of Alexandria, where 2,000 years ago the best minds of antiquity established the foundations for the systematic study of mathematics, physics, biology, astronomy, literature, geography and medicine. We build on those foundations still. The Library was constructed and supported by the Ptolemys, the Greek kings who inherited the Egyptian portion of the empire of Alexander the Great. From the time of its creation in the third century B.C. until its destruction seven centuries later, it was the brain and heart of the ancient world.
Alexandria was the publishing capital of the planet. Of course, there were no printing presses then. Books were expensive; every one of them was copied by hand. The Library was the repository of the most accurate copies in the world. The art of critical editing was invented there. The Old Testament comes down to us
mainly from the Greek translations made in the Alexandrian Library. The Ptolemys devoted much of their enormous wealth to the acquisition of every Greek book, as well as works from Africa, Persia, India, Israel and other parts of the world. Ptolemy III Euergetes wished to borrow from Athens the original manuscripts or official state copies of the great ancient tragedies of Sophocles, Aeschylus and Euripides. To the Athenians, these were a kind of cultural patrimony—something like the original handwritten copies and first folios of Shakespeare might be in England. They were reluctant to let the manuscripts out of their hands even for a moment. Only after Ptolemy guaranteed their return with an enormous cash deposit did they agree to lend the plays. But Ptolemy valued those scrolls more than gold or silver. He forfeited the deposit gladly and enshrined, as well he might, the originals in the Library. The outraged Athenians had to content themselves with the copies that Ptolemy, only a little shamefacedly, presented to them. Rarely has a state so avidly supported the pursuit of knowledge.
The Ptolemys did not merely collect established knowledge; they encouraged and financed scientific research and so generated new knowledge. The results were amazing: Eratosthenes accurately calculated the size of the Earth, mapped it, and argued that India could be reached by sailing westward from Spain. Hipparchus anticipated that stars come into being, slowly move during the course of centuries, and eventually perish; it was he who first catalogued the positions and magnitudes of the stars to detect such changes. Euclid produced a textbook on geometry from which humans learned for twenty-three centuries, a work that was to help awaken the scientific interest of Kepler, Newton and Einstein. Galen wrote basic works on healing and anatomy which dominated medicine until the Renaissance. There were, as we have noted, many others.
Alexandria was the greatest city the Western world had ever seen. People of all nations came there to live, to trade, to learn. On any given day, its harbors were thronged with merchants, scholars and tourists. This was a city where Greeks, Egyptians, Arabs, Syrians, Hebrews, Persians, Nubians, Phoenicians, Italians, Gauls and Iberians exchanged merchandise and ideas. It is probably here that the word cosmopolitan realized its true meaning—citizen, not just of a nation, but of the Cosmos,* To be a citizen of the Cosmos …
Here clearly were the seeds of the modern world. What prevented them from taking root and flourishing? Why instead did the West slumber through a thousand years of darkness until Columbus and Copernicus and their contemporaries rediscovered the work done in Alexandria? I cannot give you a simple answer. But I do know this: there is no record, in the entire history of the Library, that any of its illustrious scientists and scholars ever seriously challenged the political, economic and religious assumptions of their society. The permanence of the stars was questioned; the justice of slavery was not. Science and learning in general were the preserve of a privileged few. The vast population of the city had not the vaguest notion of the great discoveries taking place within the Library. New findings were not explained or popularized. The research benefited them little. Discoveries in mechanics and steam technology were applied mainly to the perfection of weapons, the encouragement of superstition, the amusement of kings. The scientists never grasped the potential of machines to free people.* The great intellectual achievements of antiquity had few immediate practical applications. Science never captured the imagination of the multitude. There was no counterbalance to stagnation, to pessimism, to the most abject surrenders to mysticism. When, at long last, the mob came to burn the Library down, there was nobody to stop them.
The last scientist who worked in the Library was a mathematician, astronomer, physicist and the head of the Neoplatonic school of philosophy—an extraordinary range of accomplishments for any individual in any age. Her name was Hypatia. She was born in Alexandria in 370. At a time when women had few options and were treated as property, Hypatia moved freely and unselfconsciously through traditional male domains. By all accounts she was a great beauty. She had many suitors but rejected all offers of marriage. The Alexandria of Hypatia’s time—by then long under Roman rule—was a city under grave strain. Slavery had sapped classical civilization of its vitality. The growing Christian Church was consolidating its power and attempting to eradicate pagan influence and culture. Hypatia stood at the epicenter of these mighty social forces. Cyril, the Archbishop of Alexandria, despised her because of her close friendship with the Roman governor, and because she was a symbol of learning and science, which were largely identified by the early Church with paganism. In great personal danger, she continued to teach and publish, until, in the year 415, on her way to work she was set upon by a fanatical mob of Cyril’s parishioners. They dragged her from her chariot, tore off her clothes, and, armed with abalone shells, flayed her flesh from her bones. Her remains were burned, her works obliterated, her name forgotten. Cyril was made a saint.
The glory of the Alexandrian Library is a dim memory. Its last remnants were destroyed soon after Hypatia’s death. It was as if the entire civilization had undergone some self-inflicted brain surgery, and most of its memories, discoveries, ideas and passions were extinguished irrevocably. The loss was incalculable. In some cases, we know only the tantalizing titles of the works that were destroyed. In most cases, we know neither the titles nor the authors. We do know that of the 123 plays of Sophocles in the Library, only seven survived. One of those seven is Oedipus Rex. Similar numbers apply to the works of Aeschylus and Euripides. It is a little as if the only surviving works of a man named William Shakespeare were Coriolanus and A Winter’s Tale, but we had heard that he had written certain other plays, unknown to us but apparently prized in his time, works entitled Hamlet, Macbeth, Julius Caesar, King Lear, Romeo and Juliet.
Of the physical contents of that glorious Library not a single scroll remains. In modern Alexandria few people have a keen appreciation, much less a detailed knowledge, of the Alexandrian Library or of the great Egyptian civilization that preceded it for thousands of years. More recent events, other cultural imperatives have taken precedence. The same is true all over the world. We have only the most tenuous contact with our past. And yet just a stone’s throw from the remains of the Serapaeum are reminders of many civilizations: enigmatic sphinxes from pharaonic Egypt; a great column erected to the Roman Emperor Diocletian by a provincial flunky for not altogether permitting the citizens of Alexandria to starve to death; a Christian church; many minarets; and the hallmarks of modern industrial civilization—apartment houses, automobiles, streetcars, urban slums, a microwave relay tower. There are a million threads from the past intertwined to make the ropes and cables of the modern world.
Our achievements rest on the accomplishments of 40,000 generations of our human predecessors, all but a tiny fraction of whom are nameless and forgotten. Every now and then we stumble on a major civilization, such as the ancient culture of Ebla, which flourished only a few millennia ago and about which we knew nothing. How ignorant we are of our own past! Inscriptions, papyruses, books time-bind the human species and permit us to hear those few voices and faint cries of our brothers and sisters, our ancestors. And what a joy of recognition when we realize how like us they were!
A time line of some of the people, machines and events described in this book. The Antikythera machine was an astronomical computer developed in ancient Greece. Heron of Alexandria experimented with steam engines. The millennium gap in the middle of the diagram represents a poignant lost opportunity for the human species.
We have in this book devoted attention to some of our ancestors whose names have not been lost: Eratosthenes, Democritus, Aristarchus, Hypatia, Leonardo, Kepler, Newton, Huygens, Champollion, Humason, Goddard, Einstein—all from Western culture because the emerging scientific civilization on our planet is mainly a Western civilization; but every culture—China, India, West Africa, Mesoamerica—has made its major contributions to our global society and had its seminal thinkers. Through technological advances in communication our planet is in the final stages of being bound up at a
breakneck pace into a single global society. If we can accomplish the integration of the Earth without obliterating cultural differences or destroying ourselves, we will have accomplished a great thing.
Near the site of the Alexandrian Library there is today a headless sphinx sculpted in the time of the pharaon Horemheb, in the Eighteenth Dynasty, a millennium before Alexander. Within easy view of that leonine body is a modern microwave relay tower. Between them runs an unbroken thread in the history of the human species. From sphinx to tower is an instant of cosmic time—a moment in the fifteen or so billion years that have elapsed since the Big Bang. Almost all record of the passage of the universe from then to now has been scattered by the winds of time. The evidence of cosmic evolution has been more thoroughly ravaged than all the papyrus scrolls in the Alexandrian Library. And yet through daring and intelligence we have stolen a few glimpses of that winding path along which our ancestors and we have traveled:
For unknown ages after the explosive outpouring of matter and energy of the Big Bang, the Cosmos was without form. There were no galaxies, no planets, no life. Deep, impenetrable darkness was everywhere, hydrogen atoms in the void. Here and there denser accumulations of gas were imperceptibly growing, globes of matter were condensing—hydrogen raindrops more massive than suns. Within these globes of gas was first kindled the nuclear fire latent in matter. A first generation of stars was born, flooding the Cosmos with light. There were in those times not yet any planets to receive the light, no living creatures to admire the radiance of the heavens. Deep in the stellar furnaces the alchemy of nuclear fusion created heavy elements, the ashes of hydrogen burning, the atomic building materials of future planets and lifeforms. Massive stars soon exhausted their stores of nuclear fuel. Rocked by colossal explosions, they returned most of their substance back into the thin gas from which they had once condensed. Here in the dark lush clouds between the stars, new raindrops made of many elements were forming, later generations of stars being born. Nearby, smaller raindrops grew, bodies far too little to ignite the nuclear fire, droplets in the interstellar mist on their way to form the planets. Among them was a small world of stone and iron, the early Earth.