HEPL Seminar Series

Thursday, 3 March 2005
2.45pm - Refreshments
3pm - Presentation
**NOTE CHANGE OF TIME**
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.

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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.