Astronomical Alignments at Teotihuacan, Mexico


Ivan Šprajc


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Latin American Antiquity

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It is known that the grid pattern characterizing the city layout of Teotihuacan incorporates two slightly different groups of alignments, skewed approximately 15.5° and 16.5° clockwise from cardinal directions. I argue that these alignments were dictated by deliberate and astronomically functional orientations of the Pyramid of the Sun and the Ciudadela. The two structures recorded sunrises and sunsets on two different sets of dates, allowing the use of an observational calendar composed of intervals that included multiples of 20 days and a 260-day period. The evidence presented suggests also that the location of the Sun Pyramid was not determined by the cave that is now underneath the structure and is probably human-made, but rather by a combination of astronomical and topographic criteria: the place allowed the temple built there to be oriented both to sunrises and sunsets on significant dates and, in the perpendicular direction, to Cerro Gordo to the north; furthermore, sunrises on the so-called quarter-days of the year could be observed from the same spot over a prominent mountain on the eastern horizon. The dates corresponding to the Teotihuacan alignments are attested also at other central Mexican archaeological sites and must have been employed, primarily, for scheduling agricultural and associated ritual activities in the yearly cycle.

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