The 26,000-Year Astronomical Monument Hidden in Plain Sight

The star map of “Safety Island” has baffled visitors for decades.

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One of the two massive bronze cast sculptures that flank Hoover Dam’s Monument Plaza. (Photo by Alexander Rose)
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Marking in the terrazzo floor of Monument Plaza showing the location of Vega, which will be our North Star in roughly 12,000 years. (Photo by Alexander Rose)
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Left: Monument Plaza with access road on left. (Image courtesy of US Bureau of Reclamation). Right: Hansen laying out the axial precession. (Image courtesy of US Bureau of Reclamation)
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Markings on the floor showing that Thuban was the North Star for the ancient Egyptians at the time of the Great Pyramids. (Photo by Alexander Rose)
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The giant bronze statues being craned into place. (Image courtesy of US Bureau of Reclamation)
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Hansen next to the completed axial precession layout before the terrazzo was laid in. (Image courtesy of US Bureau of Reclamation)
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Long exposure of star trails depicting how all the stars appear to revolve around the earth’s celestial axis, which is currently pointed close to our current North Star — Polaris. Note that when I say that the stars of the night sky “appear to” rotate around Polaris, it is because this apparent rotation is only due to our vantage point on a rotating planet. (Image courtesy of NASA)
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Figure 1. The earth sits at roughly a 23 degree tilt. Axial precession is that tilt slowly wobbling around in a circle, changing what we perceive as the celestial pole or “North Star.” (Image from Wikipedia entry on Axial Precession.)
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Figure 2. Description overlaid on the original technical drawing for the layout of terrazzo floor. (Underlay courtesy of US Bureau of Reclamation, color notations by Alexander Rose.)
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A high resolution drawing of the terrazzo layout. (Courtesy of US Bureau of Reclamation)

Executive director of The Long Now Foundation, founder of The Interval Bar, builder of combat and cocktail robots, and large flamethrowers.

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