Expanding Earth and declining gravity: a chapter in the recent history of geophysics

摘要

Although speculative ideas of an expanding Earth can befound before World War II, it was only in the 1950s and 1960s that thetheory attracted serious attention among a minority of earth scientists.While some of the proponents of the expanding Earth adopted an empiricistattitude by disregarding the physical cause of the assumed expansion, othersargued that the cause, either fully or in part, was of cosmological origin.They referred to the possibility that the gravitational constant was slowlydecreasing in time, as first suggested by P. Dirac in 1937. As a result of astronger gravitation in the past, the ancient Earth would have been smallerthan today. The gravitational argument for an expanding Earth was proposedby P. Jordan and L. Egyed in the 1950s and during the next 2 decades itwas discussed by several physicists, astronomers and earth scientists. Amongthose who for a period felt attracted by "gravitational expansionism" wereA. Holmes, J. Tuzo Wilson and F. Hoyle. The paper examines the idea of avarying gravitational constant and its impact on geophysics in the periodfrom about 1955 to the mid-1970s.