by Carl Sagan
When we hunt animals, then also can we be killed. We can be gored. Or trampled. Or eaten. What animals do means life and death for us: how they behave, what tracks they leave, their times for mating and giving birth, their times for wandering. We must know these things. We tell our children. They will tell their children.
We depend on animals. We follow them—especially in winter when there are few plants to eat. We are wandering hunters and gatherers. We call ourselves the hunterfolk.
Most of us fall asleep under the sky or under a tree or in its branches. We use animal skins for clothing: to keep us warm, to cover our nakedness and sometimes as a hammock. When we wear the animal skins we feel the animal’s power. We leap with the gazelle. We hunt with the bear. There is a bond between us and the animals. We hunt and eat the animals. They hunt and eat us. We are part of one another.
We make tools and stay alive. Some of us are experts at splitting, flaking, sharpening and polishing, as well as finding, rocks. Some rocks we tie with animal sinew to a wooden handle and make an ax. With the ax we strike plants and animals. Other rocks are tied to long sticks. If we are quiet and watchful, we can sometimes come close to an animal and stick it with the spear.
Meat spoils. Sometimes we are hungry and try not to notice. Sometimes we mix herbs with the bad meat to hide the taste. We fold foods that will not spoil into pieces of animal skin. Or big leaves. Or the shell of a large nut. It is wise to put food aside and carry it. If we eat this food too early, some of us will starve later. So we must help one another. For this and many other reasons we have rules. Everyone must obey the rules. We have always had rules. Rules are sacred.
One day there was a storm, with much lightning and thunder and rain. The little ones are afraid of storms. And sometimes so am I. The secret of the storm is hidden. The thunder is deep and loud; the lightning is brief and bright. Maybe someone very powerful is very angry. It must be someone in the sky, I think.
After the storm there was a flickering and crackling in the forest nearby. We went to see. There was a bright, hot, leaping thing, yellow and red. We had never seen such a thing before. We now call it “flame.” It has a special smell. In a way it is alive. It eats food. It eats plants and tree limbs and even whole trees, if you let it. It is strong. But it is not very smart. If all the food is gone, it dies. It will not walk a spear’s throw from one tree to another if there is no food along the way. It cannot walk without eating. But where there is much food, it grows and makes many flame children.
One of us had a brave and fearful thought: to capture the flame, feed it a little, and make it our friend. We found some long branches of hard wood. The flame was eating them, but slowly. We could pick them up by the end that had no flame. If you run fast with a small flame, it dies. Their children are weak. We did not run. We walked, shouting good wishes. “Do not die,” we said to the flame. The other hunterfolk looked with wide eyes.
Ever after, we have carried it with us. We have a flame mother to feed the flame slowly so it does not die of hunger.* Flame is a wonder, and useful too; surely a gift from powerful beings. Are they the same as the angry beings in the storm?
The flame keeps us warm on cold nights. It gives us light. It makes holes in the darkness when the Moon is new. We can fix spears at night for tomorrow’s hunt. And if we are not tired, even in the darkness we can see each other and talk. Also—a good thing!—fire keeps animals away. We can be hurt at night. Sometimes we have been eaten, even by small animals, hyenas and wolves. Now it is different. Now the flame keeps the animals back. We see them baying softly in the dark, prowling, their eyes glowing in the light of the flame. They are frightened of the flame. But we are not frightened. The flame is ours. We take care of the flame. The flame takes care of us.
The sky is important. It covers us. It speaks to us. Before the time we found the flame, we would lie back in the dark and look up at all the points of light. Some points would come together to make a picture in the sky. One of us could see the pictures better than the rest. She taught us the star pictures and what names to call them. We would sit around late at night and make up stories about the pictures in the sky: lions, dogs, bears, hunterfolk. Other, stranger things. Could they be the pictures of the powerful beings in the sky, the ones who make the storms when angry?
Mostly, the sky does not change. The same star pictures are there year after year. The Moon grows from nothing to a thin sliver to a round ball, and then back again to nothing. When the Moon changes, the women bleed. Some tribes have rules against sex at certain times in the growing and shrinking of the Moon. Some tribes scratch the days of the Moon or the days that the women bleed on antler bones. Then they can plan ahead and obey their rules. Rules are sacred.
The stars are very far away. When we climb a hill or a tree they are no closer. And clouds come between us and the stars: the stars must be behind the clouds. The Moon, as it slowly moves, passes in front of stars. Later you can see that the stars are not harmed. The Moon does not eat stars. The stars must be behind the Moon. They flicker. A strange, cold, white faraway light. Many of them. All over the sky. But only at night. I wonder what they are.
After we found the flame, I was sitting near the campfire wondering about the stars. Slowly a thought came: The stars are flame, I thought. Then I had another thought: The stars are campfires that other hunterfolk light at night. The stars give a smaller light than campfires. So the stars must be campfires very far away. “But,” they ask me, “how can there be campfires in the sky? Why do the campfires and the hunter people around those flames not fall down at our feet? Why don’t strange tribes drop from the sky?”
Those are good questions. They trouble me. Sometimes I think the sky is half of a big eggshell or a big nutshell. I think the people around those faraway campfires look down at us—except for them it seems up—and say that we are in their sky, and wonder why we do not fall up to them, if you see what I mean. But hunterfolk say, “Down is down and up is up.” That is a good answer, too.
There is another thought that one of us had. His thought is that night is a great black animal skin, thrown up over the sky. There are holes in the skin. We look through the holes. And we see flame. His thought is not just that there is flame in a few places where we see stars. He thinks there is flame everywhere. He thinks flame covers the whole sky. But the skin hides the flame. Except where there are holes.
Some stars wander. Like the animals we hunt. Like us. If you watch with care over many months, you find they move. There are only five of them, like the fingers on a hand. They wander slowly among the stars. If the campfire thought is true, those stars must be tribes of wandering hunterfolk, carrying big fires. But I don’t see how wandering stars can be holes in a skin. When you make a hole, there it is. A hole is a hole. Holes do not wander. Also, I don’t want to be surrounded by a sky of flame. If the skin fell, the night sky would be bright—too bright—like seeing flame everywhere. I think a sky of flame would eat us all. Maybe there are two kinds of powerful beings in the sky. Bad ones, who wish the flame to eat us. And good ones who put up the skin to keep the flame away. We must find some way to thank the good ones.
I don’t know if the stars are campfires in the sky. Or holes in a skin through which the flame of power looks down on us. Sometimes I think one way. Sometimes I think a different way. Once I thought there are no campfires and no holes but something else, too hard for me to understand.
Rest your neck on a log. Your head goes back. Then you can see only the sky. No hills, no trees, no hunterfolk, no campfire. Just sky. Sometimes I feel I may fall up into the sky. If the stars are campfires, I would like to visit those other hunterfolk—the ones who wander. Then I feel good about falling up. But if the stars are holes in a skin, I become afraid. I don’t want to fall up through a hole and into the flame of power.
I wish I knew which was true. I don’t like not knowing.
I do not imagine that many members of a hunter/gatherer group had thoughts like these about the st
ars. Perhaps, over the ages, a few did, but never all these thoughts in the same person. Yet, sophisticated ideas are common in such communities. For example, the !Kung* Bushmen of the Kalahari Desert in Botswana have an explanation for the Milky Way, which at their latitude is often overhead. They call it “the backbone of night,” as if the sky were some great beast inside which we live. Their explanation makes the Milky Way useful as well as understandable. The !Kung believe the Milky Way holds up the night; that if it were not for the Milky Way, fragments of darkness would come crashing down at our feet. It is an elegant idea.
Metaphors like those about celestial campfires or galactic backbones were eventually replaced in most human cultures 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 or goddess for every human concern. Gods ran Nature. Nothing could happen without their direct intervention. If they were happy, there was plenty of food, and humans were happy. But if something displeased the gods—and sometimes it took very little—the consequences were awesome: droughts, storms, wars, earthquakes, volcanoes, epidemics. The gods had to be propitiated, and a vast industry of priests and oracles arose to make the gods less angry. But because the gods were capricious, you could not be sure what they would do. Nature was a mystery. It was hard to understand the world.
Little remains of the Heraion on the Aegean isle of Samos, one of the wonders of the ancient world, a great temple dedicated to Hera, who began her career as goddess of the sky. She was the patron deity of Samos, playing the same role there as Athena did in Athens. Much later she married Zeus, the chief of the Olympian gods. They honeymooned on Samos, the old stories tell us. The Greek religion explained that diffuse band of light in the night sky as the milk of Hera, squirted from her breast across the heavens, a legend that is the origin of the phrase Westerners still use—the Milky Way. Perhaps it originally represented the important insight that the sky nurtures the Earth; if so, that meaning seems to have been forgotten millennia ago.
We are, almost all of us, descended from people who responded to the dangers of existence by inventing stories about unpredictable or disgruntled deities. For a long time the human instinct to understand was thwarted by facile religious explanations, as in ancient Greece in the time of Homer, where there were gods of the sky and the Earth, the thunderstorm, the oceans and the underworld, fire and time and love and war; where every tree and meadow had its dryad and maenad.
For thousands of years humans were oppressed—as some of us still are—by the notion that the universe is a marionette whose strings are pulled by a god or gods, unseen and inscrutable. Then, 2,500 years ago, there was a glorious awakening in Ionia: on Samos and the other nearby Greek colonies that grew up among the islands and inlets of the busy eastern Aegean Sea.* Suddenly there were people who believed that everything was made of atoms; that human beings and other animals had sprung from simpler forms; that diseases were not caused by demons or the gods; that the Earth was only a planet going around the Sun. And that the stars were very far away.
This revolution made Cosmos out of Chaos. The early Greeks had believed that the first being was Chaos, corresponding to the phrase in Genesis in the same context, “without form.” Chaos created and then mated with a goddess called Night, and their offspring eventually produced all the gods and men. A universe created from Chaos was in perfect keeping with the Greek belief in an unpredictable Nature run by capricious gods. But in the sixth century B.C., in Ionia, a new concept developed, one of the great ideas of the human species. The universe is knowable, the ancient Ionians argued, because it exhibits an internal order: there are regularities in Nature that permit its secrets to be uncovered. Nature is not entirely unpredictable; there are rules even she must obey. This ordered and admirable character of the universe was called Cosmos.
But why Ionia, why in these unassuming and pastoral landscapes, these remote islands and inlets of the Eastern Mediterranean? Why not in the great cities of India or Egypt, Babylonia, China or Mesoamerica? China had an astronomical tradition millennia old; it invented paper and printing, rockets, clocks, silk, porcelain, and ocean-going navies. Some historians argue it was nevertheless too traditionalist a society, too unwilling to adopt innovations. Why not India, an extremely rich, mathematically gifted culture? Because, some historians maintain, of a rigid fascination with the idea of an infinitely old universe condemned to an endless cycle of deaths and rebirths, of souls and universes, in which nothing fundamentally new could ever happen. Why not Mayan and Aztec societies, which were accomplished in astronomy and captivated, as the Indians were, by large numbers? Because, some historians declare, they lacked the aptitude or impetus for mechanical invention. The Mayans and the Aztecs did not even—except for children’s toys—invent the wheel.
The Ionians had several advantages. Ionia is an island realm. Isolation, even if incomplete, breeds diversity. With many different islands, there was a variety of political systems. No single concentration of power could enforce social and intellectual conformity in all the islands. Free inquiry became possible. The promotion of superstition was not considered a political necessity. Unlike many other cultures, the Ionians were at the crossroads of civilizations, not at one of the centers. In Ionia, the Phoenician alphabet was first adapted to Greek usage and widespread literacy became possible. Writing was no longer a monopoly of the priests and scribes. The thoughts of many were available for consideration and debate. Political power was in the hands of the merchants, who actively promoted the technology on which their prosperity depended. It was in the Eastern Mediterranean that African, Asian, and European civilizations, including the great cultures of Egypt and Mesopotamia, met and cross-fertilized in a vigorous and heady confrontation of prejudices, languages, ideas and gods. What do you do when you are faced with several different gods each claiming the same territory? The Babylonian Marduk and the Greek Zeus was each considered master of the sky and king of the gods. You might decide that Marduk and Zeus were really the same. You might also decide, since they had quite different attributes, that one of them was merely invented by the priests. But if one, why not both?
And so it was that the great idea arose, the realization that there might be a way to know the world without the god hypothesis; that there might be principles, forces, laws of nature, through which the world could be understood without attributing the fall of every sparrow to the direct intervention of Zeus.
China and India and Mesoamerica would, I think, have tumbled to science too, if only they had been given a little more time. Cultures do not develop with identical rhythms or evolve in lock-step. They arise at different times and progress at different rates. The scientific world view works so well, explains so much and resonates so harmoniously with the most advanced parts of our brains that in time, I think, virtually every culture on the Earth, left to its own devices, would have discovered science. Some culture had to be first. As it turned out, Ionia was the place where science was born.
Between 600 and 400 B.C., this great revolution in human thought began. The key to the revolution was the hand. Some of the brilliant Ionian thinkers were the sons of sailors and farmers and weavers. They were accustomed to poking and fixing, unlike the priests and scribes of other nations, who, raised in luxury, were reluctant to dirty their hands. They rejected superstition, and they worked wonders. In many cases we have only fragmentary or secondhand accounts of what happened. The metaphors used then may be obscure to us now. There was almost certainly a conscious effort a few centuries later to suppress the new insights. The leading figures in this revolution were men with Greek names, largely unfamiliar to us today, but the truest pioneers in the development of our civilization and our humanity.
The first Ionian scientist was Thales of Miletus, a city in Asia across a narrow channel of water from the island of Samos. He had traveled in Egypt and was conversant with the knowledge of Babylon. It
is said that he predicted a solar eclipse. He learned how to measure the height of a pyramid from the length of its shadow and the angle of the Sun above the horizon, a method employed today to determine the heights of the mountains of the Moon. He was the first to prove geometric theorems of the sort codified by Euclid three centuries later—for example, the proposition that the angles at the base of an isosceles triangle are equal. There is a clear continuity of intellectual effort from Thales to Euclid to Isaac Newton’s purchase of the Elements of Geometry at Stourbridge Fair in 1663 (p. 68), the event that precipitated modern science and technology.
Thales attempted to understand the world without invoking the intervention of the gods. Like the Babylonians, he believed the world to have once been water. To explain the dry land, the Babylonians added that Marduk had placed a mat on the face of the waters and piled dirt upon it.* Thales held a similar view, but, as Benjamin Farrington said, “left Marduk out.” Yes, everything was once water, but the Earth formed out of the oceans by a natural process—similar, he thought, to the silting he had observed at the delta of the Nile. Indeed, he thought that water was a common principle underlying all of matter, just as today we might say the same of electrons, protons and neutrons, or of quarks. Whether Thales’ conclusion was correct is not as important as his approach: The world was not made by the gods, but instead was the work of material forces interacting in Nature. Thales brought back from Babylon and Egypt the seeds of the new sciences of astronomy and geometry, sciences that would sprout and grow in the fertile soil of Ionia.
Very little is known about the personal life of Thales, but one revealing anecdote is told by Aristotle in his Politics:
[Thales] was reproached for his poverty, which was supposed to show that philosophy is of no use. According to the story, he knew by his skill [in interpreting the heavens] while it was yet winter that there would be a great harvest of olives in the coming year; so, having a little money, he gave deposits for the use of all the olive-presses in Chios and Miletus, which he hired at a low price because no one bid against him. When the harvest time came, and many were wanted all at once, he let them out at any rate which he pleased and made a quantity of money. Thus he showed the world philosophers can easily be rich if they like, but that their ambition is of another sort.