Cosmologies with variable gravitational constant

Abstract

In 193 7 Dirac presented an argument, based on the soealIed large dimensionless numbers, which led him to the conclusion that the Newtonian gravitational constant G changes with epoch. Towards the end of the last century Ernst Maeh had given plausible arguments to link the property of inertia of matter to the large scale structure of the universe. Mach's principle also leads to cosmological models with a variable gravitational constant. Three cosmoIogies which predict a variable G are discussed in this paper both from theoretical and observational points of view.