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Catching Photons Coming from the Moon 146

Roland Piquepaille writes "In 'Shooting the moon,' the San Diego Union-Tribune describes how and why physicists from UCSD are using lasers to send light pulses in direction of an array of reflectors installed on our moon in 1969 by Neil Armstrong and Buzz Aldrin. One of the goals of these experiments is to check the validity of Einstein's theory of general relativity. Another one is to measure the distance between the Earth and moon with a precision of one millimeter by catching photons after their round trip to the moon. But it is amazing to realize how difficult it is to capture photons after such a trip. I also have up a summary, which contains additional details and pictures, if you just want to learn how difficult it is to capture photons back from the moon."
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Catching Photons Coming from the Moon

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  • by calidoscope ( 312571 ) on Saturday July 15, 2006 @12:02AM (#15723539)
    Well if you read TFA from the Union-Trib, the whole point was getting enough accuracy to see if the orbit of the moon followed the predictions of General Relativity exactly. A deviation from those predictions would mean that General Relativity needs amending. The beauty of this experiment is that it is relatively inexpensive - the reflector is already on the moon.
  • Re:nice (Score:4, Insightful)

    by Umbral Blot ( 737704 ) on Saturday July 15, 2006 @12:18AM (#15723581) Homepage
    Oh we had the technology to verify the theory long ago (the atom bomb was one such verification of E=mc^2, the slower decay of fast moving particles is a verification of time dilation, the bending of light arround the sun observable during an eclipse is a verification of the curvature of space time, and the explanation of Mercury's orbit is a verfication of E=mc^2 in the other direction), this is simply an additional check.
  • Seeing the surface (Score:2, Insightful)

    by FractusMan ( 711004 ) on Saturday July 15, 2006 @01:17AM (#15723723)
    This is slightly off topic, but related to sending light and receiving it. From the Earth's surface, just how good of a resolution can we get of the lunar surface? I mean, can we put the 'We never landed on the Moon' theories to rest simply by pointing a good telescope up there and looking for footprints/lunar rover tracks?

We cannot command nature except by obeying her. -- Sir Francis Bacon