| The Magazine of the CALIFORNIA ACADEMY OF SCIENCES |
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Skywatcher Light Before Dawn
Thirty-two thousand years ago, an artisan carefully gouged a series of circles and crescent-shaped pits into a flat, palm-sized piece of bone. The marks, although carved at different times, form a single serpentine pattern. They remain as enigmatic today as when they were discovered in a French cave a century ago. We know that the bone carver's contemporaries worked stone, wood, and bone into tools and figurines, illuminated cave walls with vivid images of mammoths, aurochs, and shamans, and buried their dead with ceremony. Did they also study the skies, match the movements of the Sun and stars to the seasons, and measure time by the phases of the Moon? Does this incised bone, in fact, preserve the first known astronomical notation, a record of patient skywatching by a Paleolithic Galileo? Alexander Marshack, a science writer turned archeologist, studied this artifact from Abri Blanchard, and hundreds of others from Paleolithic to Neolithic times, in minute detail. When he traced the marks through their loops and turns, he found that they fell into groups that mirrored the phases of the Moon over a two-and-a-quarter-month period. Although most archaeologists remain skeptical, he is convinced that the markings depict "the turning of the Moon" 32 millennia ago. Marshack believes that our ancient ancestors observed the phases of the Moon for the most practical of reasons. "Correlating the movements in the sky with the comings and goings of plants and animals structured their way of life," he says. "All the things they did were done to a schedule-the right time, the right place, the right season. That's when you hunted particular animals. That's when you went into caves to do the paintings." It makes sense to archeoastronomers-scientists from a variety of disciplines who try to discover what prehistoric people knew about the sky-that the Moon was the first celestial object our ancestors methodically studied. Besides its mystery and beauty, the Moon is the model of cyclical change. Each month it goes through a dramatic circle of birth, growth, decline, death, and rebirth. Archeoastronomer Edwin Krupp points out that the Moon underlies our very concept of measurement. The Indo-European root "me" appears, slightly transformed, in the words moon, month, and menstruate, and even in measure itself. About 25,000 years ago, an unknown artist carved a bas-relief of a woman, called the Venus of Laussel, into a limestone slab. The carving suggests that Ice Age Europeans linked the Moon with the vital matter of human fertility. This female figure one of thousands that archeologists have found, holds a crescent-shaped horn in her right hand while her left hand rests on her ample belly. Thirteen lines-suggesting the number of lunar months in a year-are cut into the crescent. Only later did skywatchers begin to track the slower cycles of the Sun and stars. Two thousand years before the prehistoric residents of the British Isles erected great stone circles like Stonehenge, nomadic cattle-herders built a dramatic ceremonial center devoted to the Sun, at Nabta, in the Sahara Desert west of the Nile. It lay in ruins for nearly 5,000 years until anthropologist Fred Wendorf, of Southern Methodist University, and astronomer J. McKim Malville, of the University of Colorado, excavated it in 1997. About 7,000 years ago, the nomads, who came to Nabta to water their cattle at a seasonal lake fed by the summer monsoons, began to build megalithic tombs and alignments of standing stones. One line of stones marches due east from the tombs, while an outlying monolith indicates north. The builders could have gained their accurate knowledge of the cardinal directions only through careful observation of the stars. Malville's most recent calculations show that the site's longest alignment, six stones spanning nearly a kilometer, points towrd the heliacal rising of Sirius-the horizon point where the bright star was first visible just before dawn. A few hundred meters from the tombs stands a kind of miniature Stonehenge-a calendar circle four meters in diameter framed by four closely spaced pairs of stones. Two of the pairs of stones orient the structure north to south. Peering through the other aligned pairs at dawn 6,000 years ago, a watcher would have been dazzled by the summer solstice sunrise. Like ancient Polynesians and today's Bedouins, Malville says, the nomads of Nabta had to use the stars to navigate across vast spaces devoid of landmarks. "These were star-navigating people," he says. "They had to use the stars to move across the desert-and the Sahara is a very big desert." Malville and Wendorf speculate that when the monsoons failed about 5,000 years ago, these astronomically-savvy nomads may have moved to the banks of the Nile and contributed to the development of the complex agricultural society that built the first pyramids 300 years later. Until the dawn of agriculture, people may have needed no calendar except the Moon. Many traditional cultures mark time with a year composed of a set number of lunar months, often named to match the seasons. The Moon of the Newborn Reindeer, Moon of the First Leaves, and Moon of the Shedding Antlers, for example, reflect the Chukchi's Siberian world. Twelve lunar months of 29.5 days add up to a year of 354 days, nine hours. The solar year-which stakes out the seasons-is almost eleven days longer. A calendar based on twelve Moons would drift through the seasons like an unanchored boat. The Egyptians were the first, by several thousand years, to solve this problem. Because the annual flooding of the Nile controlled their lives, they were attuned to celestial events that coincided with it. Sirius, the brightest star in the sky, which they called Sothis and identified with the fertility goddess Isis, first appeared in the predawn sky each year just as the Nile began its life-giving floods. While the rising of the Nile varied year to year, Sothis appeared with perfect regularity. Through careful observations more than 6,000 years ago, the Egyptians pegged the solar year to 365 days. The late June reappearance of Sothis after 70 days of invisibility became their New Year's Day, Peret Sepdet, and was celebrated with great ceremony. The Egyptians were the first to tally the years, about 6,200 years ago. And they were also the first to divide the night and day into twelve hours, using the rising of bright stars-later called decans-to mark the hours till dawn. Sirius and the stars of Orion's belt are the only decans Egyptologists have identified for sure. Like many cultures, the Egyptians wove the skies into the beliefs that structured their lives. According to Ronald Wells, an astronomer affiliated with the University of California at Berkeley, one great myth-of the sky goddess Nut giving birth to the Sun god Ra-"catalyzed both time keeping and calendar development, endowed the concept of divine royalty, and instituted the matrilineal inheritance of the throne." The Egyptians conceived of Nut as a naked female arched across the sky. The myth, recorded in dynastic times, has Ra entering Nut's mouth, passing through her starry body, and emerging, reborn, from her loins. In 1994, Wells theorized that the Egyptians equated Nut's body with the Milky Way, seeing her head in our constellation Gemini, and her birth canal in Cygnus, where cosmic dust clouds split the Milky Way into two "legs." Early in Egyptian prehistory, about 6,500 years ago, the Sun would have set just before Gemini-Nut's head-at the spring equinox, as if swallowed by the goddess. Nine months later, at the winter solstice, the Sun, reborn, would have risen very close to Cygnus, as if emerging from the birth canal. If Wells is right, the Egyptians observed the night sky in great detail, and used that knowledge within their unique belief system. While many archeoastronomers see Wells's theory as highly speculative, they agree that the Egyptians were the first to discover that the actual solar year is 365- 1/4 days in length, although they never incorporated this into their civil calendar. Two thousand years later, after Caesar consolidated control of Egypt, he made the 365-1/4-day year the foundation of the Roman calendar. The Romans went on to colonize most of Europe and the British Isles, bequeathing us our year and our months. While the Egyptians were perfecting their calendar, people throughout the British Isles and Western Europe were building ceremonial centers of great stones arrayed in circles, ellipses, and less regular shapes. Many of these structures, along with outlying stones and points on the horizon, contain suggestive alignments with summer or winter solstices and with astronomically important risings or settings of the Moon. Clive Ruggles, an archeoastronomer at the University of Leicester, challenges the popular belief that Stonehenge and other megalithic monuments were observatories, although they clearly incorporate astronomical observations in their designs. Instead, he says, they were hubs for the most important gatherings and rituals of their builders. They were more like theaters, he believes, capturing the Sun and Moon at special times to illuminate and dramatize important ceremonies. We can get a sense of how our Neolithic forebears used their astronomical knowledge-and its symbolic power-at Newgrange, in County Meath, Ireland. Newgrange consists of a complex of stone monuments built 5,000 to 6,000 years ago. A crypt occupies a ridge overlooking the valley of the River Boyne. A 19-meter-long passage runs from a doorway on the southeast side to the three inner chambers that held the dead. At sunrise, for several days around the winter solstice, sunlight pours into the passageway through a transom-like opening above the once-sealed entrance and splashes against the wall of the burial chambers. How awe-inspiring it must have been, 50 centuries ago, to wield such control over the Sun-to know that at dawn on the darkest day of the year, at your command, the Sun would form a shimmering bridge from death's bedchamber to the skies. By the time the Romans added the British Isles to their empire, Newgrange and Stonehenge were already 2,000 years old, their builders and ceremonies lost in time. But long before the Romans made the planets their gods, before scribes began to record the deeds of pharaohs and kings, before the dawn of civilization, people had been watching the skies for 30,000 years or more. They pondered the comings and goings of the gods who lived there, and wove the cycles of the Moon, the regularities of the Sun, and the patterns of the stars into the fabric of their lives. It's from that rich and ancient tapestry that our calendar, our seasonal rituals, and our sciences have evolved. Robert Adler, author of Sharing the Children, is a freelance science writer based in the San Francisco Bay Area. |
Fall 1999
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