 The simple comparison made above between STR and Newtonian physics in Galilean spacetime is somewhat deceptive. For one thing, Galilean spacetime is a mathematical innovation posterior to Einstein’s 1905 theory; before then, Galilean spacetime had not been conceived, and full acceptance of Newtonian mechanics implied accepting absolute velocities and, arguably, absolute positions, just as laid down in the Scholium. So Einstein’s elimination of absolute velocity was a genuine conceptual advance. Moreover, the Scholium was not the only reason for supposing that there existed a privileged reference frame of ‘rest’: the working assumption of almost all physicists in the latter half of the 19th century was that, in order to understand the wave theory of light, one had to postulate an aetherial medium filling all space, wave-like disturbances in which constituted electromagnetic radiation. It was assumed that the aether rest frame would be an inertial reference frame; and physicists felt some temptation to equate its frame with the absolute rest frame, though this was not necessary. Regardless of this equation of the aether with absolute space, it was assumed by all 19th century physicists that the equations of electrodynamic theory would have to look different in a reference frame moving with respect to the aether than they did in the aether’s rest frame (where they presumably take their canonical form, i.e., Maxwell’s equations and the Lorentz force law). So while theoreticians labored to find plausible transformation rules for the electrodynamics of moving bodies, experimentalists tried to detect the Earth’s motion in the aether. Experiment and theory played collaborative roles, with experimental results ruling out certain theoretical moves and suggesting new ones, while theoretical advances called for new experimental tests for their confirmation or – as it happened – disconfirmation.