Precise Measurement Of Period Of Torsion Balance And The Study Of "Abnormal Mode" In The Determining G

Since Cavendish reported the first experiment value of G, nearly 300 different measurements of G have been made over the two centuries. G is still the least precisely determined constant among all the fundamental constants of nature. The difficult in measuring G stems from the extreme weakness of gravitational force. Additional problem is that the external gravitational field can not be shielded. Up to now, the precision measurement is still a hot point over the world.This paper mainly deals with some key problems about determining G by means of the swing time method. The disturbance such as temperature, nonlinear gravitational field and static electronic field has been studied. The correlation method is used to determine the period of a torsion pendulum. Calculation shows that this method can not only suppress the disturbance of the white noise, but also be insensitive to the drift and the damping of the torsion pendulum. The frequency estimate based on this method is an approximative minimum variance unbiased (MVU) estimator. The equations describing the dynamics of torsion balance has been proposed. We solved these nonlinear equations by means of numeric computation. The computed curve shows that the "abnormal mode" of the experimental data is an intrinsic mode of motion.