A Frequency Metrology approach to Newtonian constant G determination using a pair of extremely high Q simple pendulums in free decay

Abstract

It is argued that simple pendulums exhibiting Q values in excess of 108 can be realized by using high strength fibres to suspend in vacuum a bob of less than 10-3 kg. For a 1 m long pendulum this means damping time constants of several years, long enough to allow experiments in free decay mode, maximizing in this way the expected short term frequency stability. A dual pendulum experiment based on this projection is discussed, which common-modes seismic noise and is expected to yield 10-5 uncertainty on Big G. The value of the latter can be obtained from the variation in relative frequency difference between the two pendulums when they are subjected to well controlled variations of the gravitational field. A discussion is given of Type A and Type B uncertainty contributions, and a tentative accuracy budget is projected.