Poincaré’s Hypothetises and Results Versus Einstein’s

The aim of this chapter is to compare the main results established by Poincaré and Einstein in their publications. Based on the analysis carried out in the previous two chapters, it will be shown that the principle of relativityPrinciple of relativity, the concept of simultaneitySimultaneity, the Lorentz transformationLorentz transformation and the new relativistic velocity addition lawRelativistic velocity addition law, which form the basis of the theory of special relativity, had already been established and published by Poincaré before Einstein had submitted or published anything in a scientific journal. The difference between Poincaré’s dynamicalDynamic approach and Einstein’s kinematicKinematic approach will also help to explain why Poincaré retained the luminiferous etherLuminiferous ether, whereas Einstein may have considered it “superfluous” in the development of his theory, but did not completely renounce it, as has too often been wrongly asserted. The question of the anteriority of Poincaré’s work over that of Einstein having thus been resolved, the question of the authorship of the special theory of relativity arises, which will be the subject of the next chapters.