© 1995, Astronomical Society of the Pacific, 390 Ashton Avenue, San Francisco, CA 94112.
Edwin C. Krupp at the Saqqara pyramids near Cairo, Egypt. Krupp has poked around nearly 600 archaeological sites throughout the world. He is director of Griffith Observatory in Los Angeles and author of several books, including In Search of Ancient Astronomies and Echoes of Ancient Skies: The Astronomy of Lost Civilizations. Photo by Robin Rector Krupp.
by Louis Winkler, Pennsylvania State University
Indiana Jones is a registered trademark of Lucasfilm Ltd.
Archaeoastronomy, like the study of dinosaurs, reconstructs things and circumstances of the deep past. There's the intrigue of the megaliths of Stonehenge, the ancient pyramids of Egypt, the earthen figures of Britain and Peru, and the bloody rituals of the Maya. The earliest societies of the British Isles, Egypt, China, Peru, and North America all paid close attention to the skies (see figure 1). The ancient Maya, Romans, Christians, Jews, and Muslims all devised calendars. To make sense of these great structures and sophisticated concepts, archaeologists and astronomers have pooled their talents. They work together to understand ethnic groups over six millennia of world history.
As a science, archaeoastronomy is unusual in the amount of subjectivity that it involves. Although based on astronomy and spherical geometry, interpretations of sites can vary wildly. For teachers, this is a blessing. High-school students can get involved in real problems. They can perform activities either in the classroom or field, and if funds are available, they can visit actual archaeological sites. Some of the material requires little or no mathematical manipulation; the most difficult involves simple trigonometry.
First You Must Measure...
...And Then You Can Understand
Changes in the Sky
Messages on a Hillside
One of the fundamental objectives of archaeoastronomy is to find an alignment at a site. Archaeoastronomers look for pairs of stones or architectural features, located at some distance from each other. When they find a pair, they stand at one and look toward the other. Does it lie in the direction of a particular celestial body, such as the Sun, the Moon, a star, or a planet? If so, it suggests that the celestial body was carefully observed by that society. If the alignment is backed up with a relevant calendar, mythology, or early writing, it helps us to understand and appreciate the culture.
Astronomers as depicted by the ancient Maya. The Maya thought highly of their astronomers, who developed a sophisticated calendar and techniques to predict eclipses. These representations come from three Mayan books, called the Nuttall Codex (left), Selden Codex (center), and Bodleian Codex (right). Courtesy of G. Kohlmann and L. Blanco, CIEA del Instituto Politecnico Nacional, Mexico.
We can even tell how carefully the society observed the body. If the distance between the two sighting points is short, the alignment was just a rough guide, probably used to point in the general direction of the celestial object when a particular ceremony was performed. Longer separations, however, result in higher precision alignments. People could use these alignments to synchronize their calendars or track the exact path of a celestial object.
Precision sightings were some of the earliest known scientific efforts of humanity. In ancient Egypt, precision alignments oriented Cheops' pyramid. In the classical Maya period, precision alignments determined the synodic period of the planet Venus, the length of time for the planet to undergo a cycle of brightness variation (see figure 2). And in the early Bronze Age of the British Isles, precision alignments told people the length of the year, from which they predicted the coming of the seasons.
Maya glyphs of Venus. Figures courtesy of Louis Winkler unless otherwise indicated.
The amount of attention people paid to the stars varied from society to society. Most cultures grouped stars into constellations and gave them names. The modern constellations have Mesopotamian and European origins. The Chinese utilized many more, but smaller, constellations; Native Americans used fewer, but much larger, constellations. The mythologies of stars and constellations are sketchy, since stories of the stars were transmitted orally. People seem to have devised mythologies for the purpose of preserving history relevant to their culture, as well as helping them to remember the complex appearance of the night sky. When certain stars appeared near the horizon simultaneously with the Sun, people could reckon what time of year it was.
Ancient observers paid close attention to the positions of the Sun or Moon near the horizon, particularly when they were at their most northerly or southerly positions. In their most northerly position, the Sun and Moon rose highest in the sky and so attained their greatest astrological significance. (In the tropics, this extreme was in the zenith, or directly overhead, twice a year.) At their most southerly position, the Sun and Moon were at the end of one cycle and the beginning of another. To the ancients, this affected not only the celestial body, but also dead people, who were presumed to have gone on to an afterlife associated with the heavens.
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