Apollo Retroreflectors

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http://www.xkcd.com/1441

Yet more proof that man really did walk on the moon.

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Left on the moon by Apollo missions 11, 14, and 15 the three retroreflectors continue to provide an ultra-precise means of determining Earth-Moon distance.

http://en.m.wikipedia.org/wiki/Lunar_Laser_Ranging_experiment

Retroreflectors provide surveyors a precise way of measuring point-to-point distance by timing the two-way time of a laser pulse. The optical design is such that reflected light is returned in the exact direction from which it was sent with very little scatter.

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These methods are faster, safer, and infinitely more accurate than measuring distance by stretching a long steel tape (called a chain for historical reasons) as I did in college surveying camp over 30 years ago. Laser range finders and retroreflectors are the mainstay of modern surveying. This technology did not become commercially available until the 1980s, yet NASA used it in 70s to accurately measure Earth-Moon distance.

With the right equipment anyone can measure the precise distance to the Moon and simultaneously confirm that MEN FROM THE PLANET EARTH
FIRST SET FOOT UPON THE MOON
JULY 1969 A.D.

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