Henri Poincaré and special relativity (Q1594951)

The starting point of this paper is the frequently discussed controversy about the question whether Einstein's theory of special relativity has been anticipated or independently developed by Henri Poincaré. The author does not pretend to offer a new opinion about this topic; the paper is mostly a presentation and critical evaluation of the relevant texts in chronological order, including the contributions of H. A. Lorentz. As a major result, the author finds that as early as 1898, Poincaré had recognized that the statement ``two events occur simultaneously at different places'' has no objective meaning, but contrary to Einstein in 1905, he did not attach a particularly fundamental importance to this discovery. It is not clear at what time Poincaré became aware of Einstein's theory, but according to the evidence presented by the author, this must have happened around 1909/1910. There was not much understanding between Einstein and Poincaré when they met at the first Solvay Congress in 1911, and in the letter of recommendation for Einstein of the same year, Poincaré does not mention even one achievement of Einstein. This article ends with a summary of the situation, by quoting the opinion of Louis de Broglie that it was Einstein who, by a stroke of genius, took the decisive step which led to a transformation of our ideas on space and time, but that Poincaré was (with Lorentz) the one who contributed most to make this step possible.