A short-range test of Newton's gravitational inverse-square law

Abstract

Recent attempts at unifying the descriptions of gravity and quantum mechanics predict that Newton's Gravitational Inverse-Square Law will fail below some distance scale, possibly as large as 1 mm. Recent measurements of the Dark Energy content of the universe could also imply short-range modifications to gravity.Our previous tests [1] detected no deviation from the Inverse-Square Law, set new experimental limits on possible short-range violations, and constrained a gravity-strength Yukawa interaction to have a length scale below 197 mum at the 95% confidence level. This dissertation describes an improved next-generation of those tests using a new detector and attractor, each of 21-fold azimuthal symmetry. We tested the inverse-square law at separations down to 65 mum; we can now exclude gravity-strength Yukawa interactions to have a length scale below 79 mum at the 95% confidence level. We observed an apparent deviation from the inverse-square law at the shortest separations; we do not know the origin of this anomaly, nor do we know if it is a gravitational effect. Nevertheless, if this anomaly is parameterized as an additional Yukawa potential, has a characteristic length scale below 50 mum at the 68% confidence level with strength at least 5 times that of gravity. This dissertation is a complete description of this experiment.