The layman does not often have the opportunity of reading a simple exposition of advanced scientific thought written by the man who ddi the actual creative thinking. In this book, which is the result of a happy collaboration between the author of the theory of Relativity and one of his own co-workers in research, there will be found an easily understod but authoritative account of the growth of ideas in physical science from the earliest concepts to the more abstruse theories of modern times. The story they have to tell of this evolutionary development is one of the most fascinating that the human mind can meet with--the story of mankind's attempt to comprehend through inventive thought its own relationship to the external world. In simple, straightforward language, avoiding all highly technical terms and mathematical formulae, the authors have traced with beautiful clarity the steps from the mechanical view, to the more satisfactory explanations evolved by modern science. They illustrated their more difficult points with graphic clearness by a series of diagrams, and by using comparisons with the experiences of everyday life. They make comprehensible to the average reader the whole range of evolving thought in physical science, and they explain the significance of the most important contributors since the time of Newton--the inventions of the ideas of Field, Relativity, and Quanta.