Dynamical test of the law of gravitation

Abstract

Although well established in the realm of celestial mechanics, gravitation between two masses has not yet been thoroughly examined in a laboratory. There have been several tests of the interaction since the Cavendish's celebrated experiment1–6, most of them measuring the static attraction between two spherical masses at a distance R less than 0.8 m. The gravitational interaction is weak and, in contrast with the electromagnetic interaction, there is no effective means to shield it. It has therefore proved difficult to increase the distance R over 1 m. Under the circumstances several authors7–9 have noted that the existing experimental data do not exclude a possible term which is added to the newtonian 1/R potential. Meanwhile, on the grounds of elementary particle physics, a number of theoretical papers7,10–14 have been published predicting additional terms which vanish rapidly at R = ∞. We now report a test of the law of gravitation in a range of R up to 4.2 m. The experiment is based on a low frequency dynamical quadrupole–quadrupole interaction between two masses, which was first observed by Sinsky and Weber15,16. Our result agrees with the inverse square law within the accuracy of the experiment.