Stephen Hawking's new book, "The Grand Design" (written together with Leonard Mlodinow), is his first popular science book for about ten years. It seems to have created quite a stir in the non-scientific press, although in reality the book is very much in line with our latest theories in cosmology. Science began with the ancient Greeks, and the book starts off with a summary of their ideas. After a gap of some 1,400 years, a scientific approach to the Universe was revived by men such as Copernicus, Kepler, Galileo, Descartes and Newton. Hawking goes on to describe the history of scientific advances since then, and introduces ideas of what is meant by reality and what constitutes a scientific theory. He introduces us to the mysteries of quantum mechanics and relativity, and explains how our understanding of the Big Bang is growing as a result of our studies of the cosmic microwave background radiation.
But the key part of the book comes when Hawking describes something called M-theory, the leading candidate for the "theory of everything" which it is hoped will unite the two (currently incompatible, but highly successful) theories of quantum mechanics and general relativity. Both M-theory and other strands of evidence increasingly point to the conclusion that our Universe is not, after all, the only universe. The implication of these latest theories is that there are billions - and probably an infinite number - of other universes, each with their own physical laws and physical constants. This is the theory of the Multiverse. At a stroke, the theory explains why there are features of our own Universe which make it suitable for life; this is simply because we could only ever have evolved in the tiny minority of universes with the right set of physical laws.
All in all, a fascinating read. If you want to give a mind-blowing Christmas present to somebody, this is the one.