January 22, 2021
Towards the end of the 19th century, many physicists attempted to mathematically account for the motion of charged particles relative to the ether using Maxwell's theory. It was found for example that the inertia of charged particles depends on their velocity relative to the ether. Some interesting theoretical studies of the electrodynamics of moving charges was carried out by Lorentz. To simplify his calculations, Lorentz introduced some new variables, for instance the "local time" t'=t-(v x)/c² . Lorentz: "…The form of this expression suggests the introduction of a new independent variable instead of t ..." To be able to introduce this variable, magnitudes of the order v²/c² were neglected in the calculation .