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Mexican ruin was solar observatory.

The Danzantes temple at Monte Alban, one of the most popular tourist sites in Oaxaca, Mexico, is a 2,200-year-old solar observatory, claims University of Texas at Austin astrophysicist R. Robert Robbins. He says that the structure is like no other Indian observatory identified in the New World and apparently was constructed for mass viewing. "The point where you have to stand to make all the phenomena behave properly is at a gate in the plaza. At most solar temples, the vantage point is in a fairly inaccessible spot that could only have accommodated the astronomer-priest and a couple of other people at most. But at Monte Alban, a large number of people could be accommodated, so it's possible that the priest would bring big groups into the plaza to show them what was happening."

Constructed around 200 B.C., Monte Alban was excavated in the 1930s after centuries of neglect. Robbins discovered the astronomical significance of the temple when he traveled to Monte Alban soon after the autumnal equinox of 1989. Although archaeologists already had determined that one of the buildings on the grounds was of astronomical significance, no one had been able to figure out how the temple fit into the scheme of things.

Speculating that the temple was a solar observatory, Robbins arrived at the site about 11 days after the equinox and, with the aid of hand-held instruments, discovered a spot outside the plaza gate where the sun and physical markers atop the temple were aligned the evening the seasons changed. From the vantage point of the gate at sundown, the sun appears to descend into a narrow slot in the middle of the temple roof on the first day of fall and first day of spring - the two days the sun is directly on the celestial equator. By running some calculations, he determined that the sun descends into the south corner of the temple roof on the first day of winter (when the sun is at its southernmost point) and into the north corner of the roof on the first day of summer (when the sun is at its northernmost point). Thus, the temple was determined to be a solar observatory.

Robbins next turned his attention to a peculiarly shaped building on the grounds that was proven years ago to be aligned with certain astronomical phenomena. Shaped something like an arrowhead, the building has layers that face slightly different directions and its interior is honeycombed with tunnels and hidden rooms. The arrowhead points southwest to the setting point of five of the brightest stars in the sky - or at least it pointed to them 2,000 years ago.

The reason the phenomena no longer can be observed is because of precession - a process in which the Earth wobbles on its axis just as a toy top does in the direction of its spin. A complete precessional rotation around the axis takes 26,000 years. Because the Earth is inclined by 23 degrees, a few hundred years can result in a significant change in the rising and setting points of stars on the horizon. The rising and setting points of the sun, however, are not affected by precession.

Although the various alignments may seem to have little significance today, the religious importance in the prehistory of the New World virtually is certain, and the discovery exhibits a sophisticated knowledge of the heavens, Robbins points out. Indicative of the Indians' skills is the fact that they were able to determine the first days of fall and spring (the equinoxes), because nothing unusual happens in the sky on those days unless the observer is at the equator where the sun is directly overhead.
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Publication:USA Today (Magazine)
Date:Jun 1, 1993
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