Physics and Astronomy Calendar

Recent theories of physics beyond the standard model have predicted deviations from Newtonian gravity at short distances. In order to test these theories, we have a built an apparatus that can measure attonewton-scale forces between small masses separated by distances on the order of 25 microns. A micromachined silicon cantilever was used as the force sensor, and its displacement was measured with a fiber interferometer. We have used our measurements to set bounds on the magnitude alpha and length scale lambda of Yukawa-type deviations from Newtonian gravity; our results presented here yield the best experimental
limit in the range of lambda between 5 and 50 microns. We also discuss initial results from new experiments in which substantial improvements are expected.

1. S.J. Smullin, A.A. Geraci, D.M. Weld, J. Chiaverini, S. Holms, and A. Kapitulnik, Phys. Rev. D 72, 122001-1-20 (2005).