Varying gravity. Dirac's legacy in cosmology and geophysics
In usual understanding cosmology and geophysics are separate fields of research -- and this with a certain right since generally processes in these fields proceed on different time scales. But in the 1960s and 1970s, there was a vivid discussion about a possible interconnection between relativistic cosmology and geophysics because the Jordan-Brans-Dicke theory of gravity leads to a varying gravitational coupling parameter (a varying gravitational ``constant''). This result supported an early hypothesis by Dirac, and Jordan and others argued that, as a consequence, Earth has increased in size such that this form of varying gravity could be considered as an alternative to the hypothesis explaining the continental drift by plate tectonics. Today, the latter viewpoint is established. This, however, does not mean that Jordan-Brans-Dicke-type theories are out of discussion, it was only recognized that the cosmological influence on Earth expansion is too small to be measured. Therefore, cosmology and geophysics go again separate ways. The author considers mainly the stage to about 1980, but in brief he refers also to modern developments in both fields. This book is a stimulating reading material because it contains a lot of historical and systematic information in cosmology and geophysics. Moreover, it shows how fantasy can help to overcome disciplinary borderlines, although -- as in this case -- fantasy can go wrong.
scientific article; zbMATH DE number 6492265