The Edge of History
1. A New Way of Thinking. On April 6, 1922, the Société Française de Philosophie (which Henri Poincaré had helped found) convened for a discussion of the special and the general theories of relativity. Among those in attendance were the mathematicians Elie Cartan, Jacques Hadamard, and Paul Painlevé, the physicists Jean Becquerel, Albert Einstein, and Paul Langevin, and the philosophers Henri Bergson, Leon Brunschvicg, Edouard LeRoy, and Emile Meyerson. In the course of the discussions, Bergson expressed his admiration for Einstein's work: 'I see [in this work] not only a new physics, but also, in certain respects, a new way of thinking' [B1].
Special relativity led to new modes of philosophical reflection. It also gave rise to new limericks, such as the one about the young lady from Wight. However, first and foremost this theory brought forth a new way of thinking in physics itself, new because it called for a revision of concepts long entrenched in the physics and chemistry of the classical period. In physics the great novelties were, first, that the recording of measurements of space intervals and time durations demanded more detailed specifications than were held necessary theretofore and, second, that the lessons of classical mechanics are correct only in the limit v/c ≪ 1. In chemistry the great novelty was that Lavoisier's law of mass conservation and Dalton's rule of simply proportionate weights were only approximate but nevertheless so good that no perceptible changes in conventional chemistry were called for. Thus relativity turned Newtonian mechanics and classical chemistry into approximate sciences, not diminished but better defined in the process.
Today these revisions seem harmless and are easy to teach. To Einstein they came rather abruptly, but only after years of unsuccessful thinking. His postulates were obvious to him once he had conceived them. When I talked with him about those times of transition, he expressed himself in a curiously impersonal way. He would refer to the birth of special relativity as 'den Schritt,' the step.
It was otherwise in the case of Lorentz and Poincaré. Each of them had struggled hard with these same problems, made important steps toward their solution, and garnered deep insights along the way. But neither of them had quite made the final transitional steps. In later years all three men, Einstein, Lorentz, and Poincaré, reacted to the special theory of relativity in ways which arouse curiosity.