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HEPL Seminar

Thursday, 3 March 2005
2.45pm - Refreshments
3pm - Presentation
Location: HEPL Conference Room

Shooting the Moon: Probing Fundamental Gravity in the Solar System

Tom Murphy
UC San Diego

The fundamental incompatability of quantum mechanics with general relativity together with our well-quantified ignorance of large-scale gravity (dark energy, dark matter) strongly suggests that we intensify our tests of gravity. APOLLO (the Apache Point Observatory Lunar Laser-ranging Operation) is a new project that will bring about order-of-magnitude improvements in testing several fundamental aspects of gravity. Using a 3.5 meter telescope to bounce laser pulses off of the retroreflector arrays left on the moon by the Apollo astronauts, APOLLO will be capable of millimeter range-precision. By determining the exact shape of the lunar orbit, it will be possible to test the equivalence principle, the time-rate-of-change of the gravitational constant, gravitomagnetism, and geodetic precession to at least ten times better precision than presently tested. In addition, APOLLO will be sensitive to departures from the inverse- square law of gravity and can potentially probe the effects of extra dimensions to which only gravity has access.


Tom Murphy is an assistant professor in the physics department at UC San Diego, and a member of CASS, the Center for Astrophysics and Space Sciences. He is working on an ultra-precise test of General Relativity using the technique of lunar laser ranging.



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