Figures of light in the early history of relativity (1905–1914)

When Albert Einstein first presented his theory of the electrodynamics of moving bodies (1905), he began by explaining how his kinematic assumptions led to a certain coordinate transformation, soon to be known as the “Lorentz” transformation. Along the way, the young Einstein affirmed the form-invariance of the equation of a spherical light-wave (or light-sphere covariance, for short) with respect to inertial frames of reference. The introduction of the notion of a light-sphere in this context turned out to be a stroke of genius, as Einstein’s idea resonated with physicists and mathematicians, and provided a way to understand the Lorentz transformation, kinematics, simultaneity, and Lorentz-covariance of the laws of physics. A focus on the light-sphere as a heuristic device provides a new perspective on the reception of relativity theory, and on the scientific community’s identification of Einstein as the theory’s principal architect. Acceptance of relativity theory, according to the best historical accounts, was not a simple function of having read Einstein’s paper on the subject. A detailed understanding of the elements that turned Einsteinian relativity into a more viable alternative than its rivals is, however, not yet at hand. Likewise, historians have only recently begun to investigate how scientists came to recognize Einstein as the author of a distinctive approach to relativity, both from the point of view of participant histories (Staley 1998), as well as from that of disciplinary history (Walter 1999a). The latter studies underline the need for careful analysis when evaluating the rise of Einstein’s reputation in the scientific community, in that this ascent was accompanied by that of relativity theory itself. We know, for example, that the fortunes of relativity theory improved when A.H. Bucherer (1908a) announced the results of electron-deflection experiments in line with relativist predictions. Einstein’s most influential promoter, Max Planck, himself a founder of relativistic dynamics, was in Einstein’s view largely responsible for the attention paid by physicists to relativity theory (Heilbron 1986, 28). Planck also praised Hermann Minkowski’s four-dimensional approach to relativity, the introduction of which marked a turning-point in the history of relativity (Walter 1999a). There is more than Planck’s praise to tie Einstein’s theory of relativity to Minkowski’s spacetime