Einstein, the reality of space, and the action-reaction principle

TL;DR

This paper explores Einstein's emphasis on the action-reaction principle in general relativity, analyzing historical and conceptual developments that shaped his views post-1915.

Contribution

It provides a detailed historical and conceptual analysis of why Einstein highlighted the action-reaction principle in relation to general relativity.

Findings

Einstein linked the action-reaction principle to Mach's analysis of inertia.

De Sitter's 1917 results influenced Einstein's views on Mach's principle.

Correspondence with Schlick clarified Einstein's evolving perspective.

Abstract

Einstein regarded as one of the triumphs of his 1915 theory of gravity --- the general theory of relativity --- that it vindicated the action--reaction principle, while Newtonian mechanics as well as his 1905 special theory of relativity supposedly violated it. In this paper we examine why Einstein came to emphasise this position several years after the development of general relativity. Several key considerations are relevant to the story: the connection Einstein originally saw between Mach's analysis of inertia and both the equivalence principle and the principle of general covariance, the waning of Mach's influence owing to de Sitter's 1917 results, and Einstein's detailed correspondence with Moritz Schlick in 1920.