Fundamental constants and their development in time

P. M. Dirac

pp. 45-59

in: Jagdish Mehra (ed), The physicist's conception of nature, Berlin, Springer, 1973

Abstract

The information that experimentalists obtain provides us with a number of constants. These constants usually have dimensions, and then of course, they depend on what units one uses, whether centimetres or inches. Then they are not of theoretical interest. However, one can combine these constants and get from them some which are dimensionless, quite independent of the system of units one uses. It is only the dimensionless ones that are of interest in our theoretical discussion, and it is only these that I shall be dealing with today.