Fact Sheet
Shooting the Moon
A laser fires at the Moon from a telescope at McDonald Observatory. The laser beam will bounce off a reflector left on the Moon by Apollo astronauts, and a tiny bit of its light will return to the telescope. By measuring the round-trip travel time, scientists can determine the Earth-Moon distance to within a couple of inches. The measurements are used to study the interior of the Moon, Earth's rotation, and theories of gravity. The laser reflectors are the last of the Apollo experiments. [Frank Armstrong/University of Texas]
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