Variability of the Physical Constants

Abstract

The accepted numerical values of the physical constants have shown disturbing variations over the period during which presumably precise measurements have been made. The reasons for this have been varied, but in most instances the explanation has been experimental error or incomplete theoretical understanding of the underlying theory. The variations observed over the past forty years in the values of the atomic constants are reviewed and the reasons for some of the variations are presented. On the other hand, Dirac’s Large Number Hypothesis (LNH) introduces the question of the variability of the physical ‘constants’ on the cosmic time scale. Because it is often possible to determine small relative variations in a physical quantity with great sensitivity, there have been some very stringent limits placed on the magnitude of possible long term variations in the values of the constants. A summary of the arguments and of the experimental basis for the conclusions is presented.