Ongoing Tests of the Inverse Square Law over very small Distances*

Attempts to unify the Standard Model and General Relativity often include features that violate the Weak Equivalence Principle (WEP) and/or the gravitational Inverse-Square Law (ISL), representing proposals to fundamentally alter our understanding of gravity. Nevertheless, to this date no violations of either principle have ever been observed. To advance our understanding in this area, undergraduate researchers and faculty at Cal Poly Humboldt are using an experiment to measure gravitational interactions over distances of less than 50 microns. The experiment uses a torsion pendulum with equal masses of two different materials arranged as a composition dipole. The twist of the torsion pendulum is measured as an attractor mass in a parallel-plate configuration is oscillated nearby, generating a time-dependent torque on the pendulum. The magnitude of this torque at this heretofore untested scale will demonstrate either physical deviations from the WEP/ISL or further restrict proposed Quantum Gravity theories that require small-scale violations of these principles. This talk will cover the project’s progress so far, as well as the possible experimental results we expect, and what those results would imply.