Variable G: a solution to the missing mass problem

It was suggested by Dirac in 1937 that the gravitational constant G might vary with time, an idea that has been taken up by Hoyle and Narlikar and by other cosmologists. Substantial observational support has been obtained for a secular decrease in G of (7.5 +- 2.7) x 10-11 per year; this deserves to be explored further. The primary concern in this communication is the explanation afforded for the 'missing mass' paradox. The hypothesis of a variable gravitational constant is stated to solve this problem completely, and also promises to assist studies on the formation, structure, and evolution of galaxies. Most galaxies probably form by the fragmentation of a protocluster gas cloud, and with a steadily weakening gravitational field subsequent breakup of most early clusters into small groups and isolated galaxies is to be expected; prediction of the quasi-homogeneous distribution of single galaxies is also to be expected. (U.K.)