This book is the first of its kind devoted to the key role played by light and electromagnetic radiation in the universe. Readers are introduced to philosophical hypotheses such as the economy, symmetry and the universality of natural laws, and are then guided to practical consequences such as the rules of geometrical optics and even Einstein's well-known but mysterious relationship, E = mc2. Most chapters feature a pen picture of the life and character of a relevant scientific figure. These ‘Historical Interludes’ include, among others, Galileo's conflicts with the Inquisition, Fourier's taunting of the guillotine, Neils Bohr and World War II, and the unique character of Richard Feynman.The second edition has been revised and made more accessible to the general reader. Whenever possible, the mathematical material of the first edition has been replaced by appropriate text to give a verbal account of the mystery of the phenomenon of light and how its understanding has developed from pre-historic to present times. The emphasis is on reading for interest and enjoyment; formulae or equations which underpin and reinforce the argument are presented in a form which does not interfere with the flow of the text.The book will be of interest to students and teachers, as well as general readers interested in physics.