Conventionality in Distant Simultaneity

TLDR

Einstein’s 1905 synchronization procedure defines standard signal synchrony, yet it has been argued that no logical or physical basis exists for preferring it over alternative synchronizations. This paper investigates the range of consistent non‑standard signal synchronizations for a single inertial system and for sets of such systems. The authors demonstrate that consistency constraints significantly reduce the freedom in choosing synchronizations. Consistent non‑standard synchronizations are possible, but the authors argue that standard synchronizations are physically preferable if special relativity’s predictions hold, thereby trivializing or refuting Reichenbach and Grünbaum’s conventionality thesis.

Abstract

In his original paper of 1905, “On the Electrodynamics of Moving Bodies”, Einstein described a procedure for synchronizing distant clocks at rest in any inertial system K. Clocks thus synchronized may be said to be in standard signal synchrony in K. It has often been claimed that there are no logical or physical reasons for preferring standard signal synchronizations to any of a range of possible non-standard ones. In this paper, the range of consistent non-standard signal synchronizations, first for any one inertial system, and second for any set of such systems, is investigated, and it is shown that the requirement of consistency leaves much less room for choice than is commonly supposed. Nevertheless consistent non-standard signal synchronizations appear to be possible. However, it is also shown that good physical reasons for preferring standard signal synchronizations exist, if the Special Theory of Relativity yields correct predictions. The thesis of the conventionality of distant simultaneity espoused particularly by Reichenbach and Grünbaum is thus either trivialized or refuted.