Determination of the Newtonian Gravitational Constant G with Time-of-Swing Method

We present a new value of the Newtonian gravitational constant G by using the time-of-swing method. Several improvements greatly reduce the uncertainties: (1) measuring the anelasticity of the fiber directly; (2) using spherical source masses minimizes the effects of density inhomogeneity and eccentricities; (3) using a quartz block pendulum simplifies its vibration modes and minimizes the uncertainty of inertial moment; (4) setting the pendulum and source masses both in a vacuum chamber reduces the error of measuring the relative positions. By two individual experiments, we obtain G=6.673 49(18)×10^-11  m³ kg^-1 s^-2 with a standard uncertainty of about 2.6 parts in 10⁵.