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When Anna Sofaer visited Los Alamos Feb. 21, her “Mystery of Chaco Canyon” film played to an overflow crowd in the Bradbury Science Museum. Sofaer will return to the Bradbury Thursday with computer modeler Alan Price, whose new simulation may shine even more light on the mystery of the Sun Dagger.Based on studies of the archaeological record of structures and petroglyphs Sofaer has studied for more than 30 years, the film demonstrates how the Chacoan culture of 1,000 years ago had knowledge of the sun’s solstices and equinoxes, as well as of the moon’s 18.5 year cycle of rising and setting at specific points on the horizon.Sofaer first discovered the “Sun Dagger” during the summer solstice of 1977. The phenomenon consists of a dagger shaped point of light that shines on a deeply etched spiral petroglyph on a butte above Chaco Canyon. Shadows cast on the petroglyph by rock slabs placed in front of the petroglyph mark the track of the moon as well.Alan Price has constructed a computer model to demonstrate the workings of the Sun Dagger construction, which not only tracks the sun’s movements across the sky, but also marks the shadow cast by the moon at significant times of its cycle.“The demonstration will be interactive with the audience,” Sofaer said in an interview last week.
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