Improved Measurement of the Newtonian Gravitational Constant G

The Newtonian gravitational constant, G, is one of the oldest known fundamental constants in nature, and yet it is known with the least precision of all other fundamental constants. Over the past 200 years numerous measurements have been made using a number of different techniques and have revealed widely varying values of G. Recently, improved measurements have been made by two experiments with results that are consistent at the 12 ppm level. After examination of the methodology used in previous measurements, the research group at IUPUI, in collaboration with Cal Poly Humboldt, will use multiple approaches within a singular torsion pendulum apparatus to precisely determine G. Specifically, measurements will be made using the angular acceleration feedback and time of swing methods in the same apparatus, which was carefully designed for reduced error in both techniques. We expect to obtain a measurement at the 2 ppm level using these new methods. By continuing the use of a torsion pendulum apparatus, we also hope to better understand the current discrepancies among previous experimental results.