Tests of Newtonian Gravitation

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This research program includes tests of the Newtonian law of gravity on a laboratory distance scale, searches for new intermediate range forces at strength levels below those currently detectable, and tests of the equivalence principle which underlies the theory of general relativity. The Irvine group plans: (1.) An improved version of their recently conducted experiment for a composition dependence in the apparent gravitational force acting on lead and copper test masses due to a local lead attracting mass. They expect to compare these forces to a few parts in 10 million. (2.) Construction and operation of a rotatable torsion balance, which will be used initially in the laboratory to test the equivalence principle using the earth and sun as acceleration sources, and later at a mountain site with low microseismic background for an improved equivalence principle test and for an ultra high sensitivity search for composition dependent forces. (3.) A test of the inverse square distance dependence of the gravitational force from 2mm to 2 cm. These experiments will provide a high-precision foundation for our knowledge of the gravitational force.