Abstract

A comparative analysis is made of the different answers that can be given to the question; what is the distance between two bodies? The physico-mathematical concept emphasizes measurement, extension, geometry and numbers. The physico-philosophical concept emphasizes the interposed bodies (ponderable or ethereal) and the notion of interaction.

Applications are made to the theories of "action at a distance" in Classical physics and to the presumptions (normally ignored) between relatively moving frames in Relativity theory. A difficulty is found in the latter case leading either to the non-uniqueness of the distance between two bodies or to the recovery of absolute simultaneity as a prerequisite for relativistic thought (what Einstein called the "dualistic sin").