Radio telemetry and the birth of spacetime conventionalism

Scott A. Walter
University of Lorraine and Henri-Poincaré Archives (CNRS)


Albert Einstein's notion of light-sphere invariance (1905) became, in the space of six years, a fundamental tenet of his theory of relativity. The notion was challenged by Henri Poincaré, for whom the apparent form of a lightwave depended on frame velocity. Poincaré's view was in turn challenged (implicitly) by Minkowski's theory of spacetime, and also by advances in wireless radio communication technology. These revolutionary innovations in theory and practice led Poincaré in 1909 to revise his earlier view of space and time, and to devise and promote a new philosophy that I call spacetime conventionalism. According to Poincaré's argument (1912), scientists may freely choose between Galilei spacetime and Minkowski spacetime, as this choice is indifferent for observable phenomena.