Tests of Newtonian Gravitation for Unpolarized and Spin Polarized Matter (Physics)

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This program shall develop and apply cryogenic and room temperature torsion balances to search for anomalous long-range interactions in nature. Such interactions reveal themselves as anomalies in the effective gravitational interaction. Recent strong impetus for such investigations comes from reported experimental evidence for a very weak long range "fifth force" in nature. An experiment is being conducted to test for such a force by searching for a composition dependence in the forces experienced by equal masses of different materials suspended from a torsion balance located on a hillside. A related experiment is being designed to search for composition dependence experienced by such a balance due to a local movable mass. Another experiment is being conducted to search for anomalous long range interactions between samples with polarized electron spins, magnetically isolated with superconducting shields. The performance of the torsion balance is being evaluated to assess its suitability for application to other experiments in gravitation such as an improved test of the equivalence of inertial and gravitational mass.