08 July 2014

There is a celestial map at Hoover Dam

From the Bureau of Reclamation's webpage on artwork at the dam:
Surrounding the base is a terrazzo floor, inlaid with a star chart, or celestial map. The chart preserves for future generations the date on which President Franklin D. Roosevelt dedicated Hoover Dam, September 30, 1935.

The apparent magnitudes of stars on the chart are shown as they would appear to the naked eye at a distance of about 190 trillion miles from earth. In reality, the distance to most of the stars is more than 950 trillion miles.

In this celestial map, the bodies of the solar system are placed so exactly that those versed in astronomy could calculate the precession (progressively earlier occurrence) of the Pole Star for approximately the next 14,000 years. Conversely, future generations could look upon this monument and determine, if no other means were available, the exact date on which Hoover Dam was dedicated.
Photo from a gallery of images


  1. The relative position of the planets to each other are a clock. Mercury circles the sun in around 59 days. So if they can locate Mercury to within 6 degrees of arc, they can be within a day. Then the relative locations of the planets to each other, establish the longer term components. iInce the outer planets have periods of decades, its fairly easy to have a clock that shows a day with time scale over centuries using relative position.

    1. Dear Mr Larrison, I've visited the star map at Hover Dam and would like to correspond with someone like yourself to better understand this monument. What is the process to working out the date " future generations would know the exact date of dedication just looking at the floor and calculating". Please reply to goldrushwally@gmail.com

  2. Sweet, although it's highly unlikely that English will still be around by then. Reminds me of Into Eternity, a documentary on a nuclear waste storage project in Finland meant to last tens of thousands of years. One of the intriguing problems they face is: How do we communicate to our future selves not to dig here?

  3. Regardless of the supposed practical purpose for this star chart, it is a beautiful piece of art in the classic art deco style. Although it's hard to see in the photo gallery at the link, astronomers will note that the Andromeda galaxy is labeled as the "great nebula" in Andromeda, as its identity as a galaxy, and indeed the very existence of galaxies, had only recently been determined, and the artist was apparently not willing to go out on a limb. Utterly amazing how far we've come in 80 years.


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