Relativity Reexamined

After my last book on scientific uncertainty was published by Academic Press (1964), I felt relieved and free to go back to a variety of problems or dreams I had been pushing aside and postponing. Some problems seemed clearly stated but not solved, while many ideas remained rather cloudy or uncertain and required a good deal of thinking over. I decided to start looking into relativity which I wanted to examine from a new angle and with an unconventional perspective; traveling along high roads is no fun, but wandering on forgotten tracks may lead to some wild summit from which you suddenly discover the whole landscape with an uncommon beauty. All along my scientific career I felt an attraction toward problems arising along the border of a theory, in this little known territory where it joins a domain reserved to another theory. How does the first theoretical description check with the painting drawn from the second theory: How can you use either wave theory or discrete particles and obtain similar results, both agreeing with experiments? How do you know where to use geometrical optics or physical light waves? Coming back to relativity, where and how does it rejoin classical mechanics? Every example may reveal some curious situation: sometimes (but not too often) one of the solutions may appear as a convergent series, where the first term corresponds to the first theory, but this is not a general rule. Very often one may discover semi-convergent series, that can be used only up to a certain term and come close enough to the solution of the other theory, in the boundary region.