Measurement of Newton's Constant Using a Torsion Balance with Angular   Acceleration Feedback
  We measured Newton's gravitational constant G using a new torsion balance method. Our technique greatly reduces several sources of uncertainty compared to previous measurements: (1) it is insensitive to anelastic torsion fiber properties; (2) a flat plate pendulum minimizes the sensitivity due to the pendulum density distribution; (3) continuous attractor rotation reduces background noise. We obtain G = (6.674215 +- 0.000092)x10^-11 m^3kg^-1s^-2; the Earth's mass is, therefore, M = (5.972245 +- 0.000082)x10^24 kg and the Sun's mass is M = (1.988435 +- 0.000027)x10^30kg. 
Jens H. Gundlach and Stephen M. Merkowitz