G^εε lab's equivalence principle experiment

Baron Roland von Eötvös performed amazing experiments on the equivalence of inertial and gravitational mass. Since his work experiments have become progressively more refined. The G^εε Lab at Washington University in St. Louis has built a new experiment in the hopes of refining these tests even further. We have operated a prototype of this experiment by continuously monitoring the angular orientation of a torsion balance for over 115 days and the results we have obtained are promising. The experience we have gained from this experiment suggest the need for improved thermal and magnetic shielding; it also gives us confidence that long-period torsion balances have the ability to significantly improve the bounds on violation of the Equivalence Principle. Here we describe our instrument and how these experiences will be used to improve our next generation torsion balance.