Time-varying Newtonian gravity and universal motion

Reference is made to the time-dependent gravitational constant G(t) proposed by Dirac in 1937 (see Nature 139 : 323 (1937)), for which there is some limited evidence. It can be incorporated in relativistic theories of gravitation, but the resulting equations are liable to be cumbersome and it is not certain what theory should be used. Attempts are here made to consider the problem in a Newtonian framework. (U.K)