Einstein and Mach's Principle

Abstract

Einstein's attempt to realize Machian ideas in the construction of general relativity was undoubtedly a very major stimulus to the creation of that theory. Indeed, the very name of the theory derives from Einstein's conviction that a theory which does justice to Mach's critique of Newton's notion of absolute space must be generally relativis-tic, or covariant with respect to the most extensive possible transformations of the spacetime coordinates. The extent to which general relativity is actually Machian is, however, the subject of great controversy. During the last six months, I have been examining closely all of Einstein's papers that concern the special and general theory of relativity together with a substantial proportion of his correspondence related to relativity. There were several things that I wished to establish: 1) What precisely was the defect (or defects) in the Newtonian scheme that Einstein sought to rectify in his general theory of relativity? 2) How did Einstein propose to rectify the perceived defect(s)? 3) What relation does Einstein's work on his Machian ideas bear to the other ideas and work of his predecessors and contemporaries on the problem of absolute and relative motion? 4) Finally, to what extent did general relativity solve that great and ancient problem of the connection between and status of absolute and relative motion?