New Measurements of G Using the Measurement Standards Laboratory Torsion Balance

This Letter presents the results of a series of measurements of the Newtonian gravitational constant G using the compensated torsion balance developed at the Measurement Standards Laboratory. Since our last published result using the torsion balance in the compensated mode of operation [ Meas. Sci. Technol. 10 439 (1999)], several improvements have been made to reduce the uncertainty in the final result. The new measurements have used both stainless steel and copper large masses. The values of G for the two sets of masses are in good agreement. After combining all of the measurements we get a value of G=6.673 87(0.000 27)×10^-11  m³ kg^-1 s^-2. This new value is 5 parts in 10⁵ smaller than our previous published values.