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Testing Gravity via Lunar Laser Ranging

Event Details

Event Dates: 

Wednesday, April 23, 2014 - 4:00pm

Seminar Location: 

  • Duane Physics Room G1B20

Speaker Name(s): 

Tom Murphy

Speaker Affiliation(s): 

University of California San Diego
Seminar Type/Subject

Scientific Seminar Type: 

  • Physics Department Colloquium

Event Details & Abstract: 

Forty years ago, Apollo astronauts placed the first of several retroreflector arrays on the moon. Laser range measurements between the earth and the moon have provided some of our best tests to date of general relativity and gravitational phenomenology--including the equivalence principle, the time-rate-of-change of the gravitational constant, the inverse square law, and gravitomagnetism. A new effort called APOLLO (the Apache Point Observatory Lunar Laser-ranging Operation) is now collecting measurements at the unprecidented precision of one millimeter, which will produce order-of-magnitude improvements in a variety of gravitational tests, as well as reveal more detail about the interior structure of the moon. This talk will include an overview of the science, a description of the instrument and its performance, evidence for dust accumulation on the lunar surface, re-discovery of a lost Soviet reflector, and an outlook for advancing the state of gravity tests in the solar system.