The discussions range over a set of basic problems in physical theory and their possible solutions—the understanding of space and time, quantum and relativity theories and recent attempts to unite them—and deal with related questions in theoretical biology. The approach is non-technical, with an emphasis on the assumptions of modern science and their implications for understanding the world we live in. The book, which originated in a highly successful radio series, provides a vivid first-hand account of some of the astounding and perplexing developments in modern science, a rare overview that will intrigue the informed non-scientist and the scientist alike.