Poincaré on clocks and radio waves in the ether
Résumé
For most of the twentieth century, historians of physics situated the discovery of the theory of relativity at the cutting edge of contemporary experimental and theoretical physics: ether-drag experiments, electron theory, and the electrodynamics of moving bodies. Following the practical turn in HST, Peter Galison suggested that to better understand the relativity revolution we should review its embedding in turn-of-the-century material cultures of clock coordination and telegraph networks. The co-founders of relativity, Henri Poincaré and Albert Einstein were both engaged with these iconically-modern technologies, at the Paris Bureau of Longitudes, and the Bern Patent Office, respectively. Galison's technology-driven account of the theory of relativity can be extended by taking into consideration Poincaré's contributions to wireless telegraphy, including his studies of the diffraction of wireless waves (1903-1912), and a 1908 lecture series on the stability of current oscillations in the singing-arc radio transmitter. Just a few months after the latter lecture series in Paris, Poincaré delivered another series in Göttingen, financed by the Wolfskehl Foundation. During his talk on the new mechanics issuing from the Lorentz group, Poincaré proposed a thought experiment that corrected his earlier, physically-untenable interpretation of the Lorentz group, ostensibly to accommodate observers in inertial motion with respect to the ether, whom he equipped with timekeepers and radio transmitter-receivers. Poincaré's new radio-based understanding of the physical significance of the Lorentz transformations was closer to the relativity theories of Einstein and Minkowski, while it retained a traditional role for the ether as the seat of radio wave propagation.