Skies over Crestone, August 2008
by Kim Malville

Perseid meteor shower, Aug 12

Sky Almanac
The month starts with fabulous views of three planets low in the western horizon about 30° at the lower right is the brightest, Venus. To the upper left of Venus you can find Saturn, much dimmer, but still brighter than its surroundings. Further up along this line is Mars. The slender crescent moon will be close to these planets August 2, 3, and 4.
August 1: New moon. A total solar eclipse will be visible over parts of northern China, Siberia, and northern Canada. The partial eclipse will be seen by billions of people and by even more non-human sentient beings throughout Europe, the Middle East, and southern Asia.
August 2: Look for the tiny crescent moon near Venus shortly after sunset.
August 11-12: The maximum of the Perseid meteor shower. The moon will set at 1am on August 11, and an hour later on August 12, will be the maximum of the shower. You will have 3-4 hours of dark sky until the sky brightens. You can identify the Perseids because they radiate outward from an area of the sky between the constellations of Perseus and Cassiopeia. There will be a few other meteors from lesser showers but these will be obviously slower than the Perseids. Keep warm and awake!
August 13-16: Look to the western horizon about 30 minutes after sunset. Mercury begins to appear in twilight, to the lower right of Venus. On August 14, 15, and 16, the three planets Venus, Saturn, and Mercury perform a slow dance with each other. They are all moving eastward (not retrograde) but at different speeds. Mercury and Venus are faster than Mars and Saturn. Binoculars will help you view the dance.
August 16: Full moon. A partial lunar eclipse will be visible throughout most of the world, except for North America. Although partial, the lunar eclipse will still be deep and probably blood red in Europe and Africa.

Astronomy of the ancient pueblos
August is a good opportunity for exploring some of the ruins of Chaco Canyon, Mesa Verde, Chimney Rock, and Hovenweep. The people who lived in these ancient buildings in AD 900-1300 were excellent astronomers. What makes their astronomy so fascinating and so compelling is that it appears to have been almost entirely homegrown, the independent discoveries of smart and alert people who paid attention to the heavens. Unlike the astronomy of ancient Europe, Puebloan astronomy was not associated with a writing system, and it developed in an isolated culture in a relatively short period. Western astronomy, by contrast, borrowed heavily from other cultures and matured over millennia.

Not only did we adopt Greek, Roman, and Arabic star names and constellations, but also we relied heavily on earlier discoveries by astronomers in Greece, Rome, Egypt and India. For example, the ancient Greeks used the difference between the shapes of the moon and of the earth’s shadow during eclipse to estimate the relative sizes of the earth and moon. About 350 BC Aristotle had concluded the earth was not flat because of its curved shadow on the moon. Then, a hundred years later, Aristarchus of Samos noticed that shadow of the earth is less rounded than moon itself. He concluded that if the sun is very far away, the earth must be about 3 times larger than the moon (the actual value is 3.7). Not bad for 23 millennia ago, but Aristarchus had texts to read and collaborators throughout the Mediterranean to consult.

The ancient Puebloans were probably the first people in the western hemisphere to discover the 18.6 year standstill cycle of the moon. The moon at major standstill rises further to the north than the sun at summer solstice, and every 18.6 years it rises between the rock towers of Chimney Rock, where folks from Chaco Canyon built a great house to view the spectacle. The Puebloans also invented a horizon calendar, which would have been necessary to schedule annual festivals. Some of the huge and dramatic buildings in Chaco Canyon were aligned to true north, which means they also invented a technique to determine true north.

Migration, trade, periodic festivals, pilgrimage, as well as danger and violence contributed to development and meaning of Puebloan astronomy. Their astronomy must have been a much more important feature of everyday life than it is for us today. For them the sky was a region of wonder and power, sunlight and rain, danger and sustenance. The sky provided rain, sunshine, direction, and time. Its stars kept traders from wandering in circles and pilgrimage festivals running on time.

Toward the end of the thirteenth century, terrible things began to happen in the Four Corners. Life became difficult due to uncertain rainfall, and there was an agonizing and poignant downward slide into warfare and violence. Towers were built at Hovenweep for protection of families and sources of water. The defensible entrance for the tower near Holly House at Hovenweep reveals how threatened people felt. They gathered into walled villages such as Sand Canyon, Castle Rock, and Goodman Point. Even though massacre, torture, and cannibalism threatened, astronomy remained important. They oriented their buildings and great kivas to the solstice sun and to the North Pole. People turned to the ancient sky gods for protection during dangerous times.

Last month, I published an expanded edition Prehistoric Astronomy in the Southwest. One of the points I make is that one doesn’t need to go to Machu Picchu or Stonehenge to find mysterious ruins with tantalizing hints of ancient knowledge. The ruins of Chaco Canyon, the twin towers of Chimney Rock, the cliff dwellings of Mesa Verde, and the dramatic towers of Hovenweep provide mystery and adventure comparable to that of the stone circles of Great Britain or the pyramids of Egypt. Furthermore, less gasoline is required.

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