ABSTRACT
Despite the great advantages of the new quantum theory, it soon became evident that there were limitations. In order to understand the developments of the 1920s and 1930s, it is necessary to digress a little and learn about Einstein’s theory of special and general relativity. In this chapter, both of these theories are introduced on the assumption that the reader is a complete beginner in these areas. The most important concept is that of space–time – the four-dimensional stage upon which future advances in quantum theory are developed.
