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Shooting for — and Hitting — the Moon

A long time ago — 9 years and one month to be precise — I wrote an article for Science Careers profiling Tom Murphy, then a postdoc in physics at the University of Washington in Seattle. Murphy was then on a quest to locate a needle in a haystack — or, less metaphorically, to bounce lasers off a mirror on the surface of the moon and then detect the reflected light.

“It’s like winning the lottery and then being told there’s an
equally remote chance the money will make it to your bank account,” he told me back then. Murphy wasn’t — isn’t — motivated merely by the challenge. The idea is to use the reflected light as a very sensitive test of Einstein’s General Theory of Relativity. The technique is called Lunar Laser Ranging. Today, Murphy and his team have popped into the news for “locat[ing] a
long lost Soviet reflector on the moon,” according to a UCSD press release

Murphy, who is now a professor at the University of California San Diego, has been bouncing light off moon-based reflectors for years. He and his group “routinely use the three hardy reflectors placed on the moon by the
Apollo 11, 14 and 15 missions,” Murphy said, quoted in that press release, “and occasionally the
Soviet-landed Lunokhod 2 reflector–though it does not work well enough
to use when illuminated by sunlight. But we yearned to find Lunokhod

That’s because “Lunokhod 1, by virtue of its location, would provide the best leverage
for understanding the liquid lunar core, and for producing an accurate
estimate of the position of the center of the moon — which is of
paramount importance in mapping out the orbit and putting Einstein’s
gravity to a test,” Murphy said.

The story was covered as a ScienceShot on ScienceNow.