Abstract

It was only after the death of the French physicist Paul Langevin in 1946, that his famous colleague Albert Einstein strongly emphasized and honored his contributions to the theory of special relativity, similar as he did in obituaries for two other pioneer physicists of the turn of the century, Poincaré and Lorentz. But Langevin and Einstein were connected by a deep personal friendship which began in the first decades of the 20th century in spite of sharp political tensions and scientific barriers especially between Germany and France. From the physical point of view, Langevin did not accept all of the basic concepts of special relativity at once even if he developped some important consequences. Their friendship and esteem for each other was based mainly on political and ideological affinities and culminated in the visits of Einstein in Paris and Langevin in Berlin