THE MILKY WAY - An Insider's Guide By William H. Waller Princeton University Press (2013) ISBN 978 0 691 12224 3 $29.95/£19.95
It is only during the past century that we have come to realise that our home galaxy is not the whole universe, but only one of countless millions of stellar islands that populate an ever expanding cosmos. The author's enthusiasm for his subject is clear from the start, and reflects some of that childlike sense of wonder that is highly infectious, and which none of us should ever lose. The book begins with a description of the different structures that make up the Milky Way, such as globular clusters, gas clouds and the many kinds of star. A historical survey then describes how various cultures and mythologies across the world from ancient times have attempted to explain the celestial glories, and how the rise of Science has led to our present understanding. Early astronomy was purely visual, but as the electromagnetic spectrum has expanded, then so has our ability to explore the universe using different wavelengths, radio, infra-red, X-ray, gamma ray and others that have each brought their own strengths and given us their own unique pictures to interpret. The structures to be found within the galaxy are described, together with the development of the stars, from their births in enormous gas clouds through their lives on the main sequence to their ultimate fates as planetary nebulae, white dwarfs, neutron stars or black holes, depending on their masses. The part played by the earliest stars in the creation of the heavier elements and their seeding of the universe with these to form rocky planets like the Earth is also explained. This leads on to a discussion of the possibilities for life elsewhere in the galaxy. The author is an enthusiastic supporter of the Search for Extraterrestrial Intelligence (SETI), and concludes that we should play our full part as `citizens' of the Milky Way, our home galaxy, without which we would not exist. While a basic grasp of physics and astronomy is helpful to the enjoyment of the book, it is not essential, and a glossary explains most of the scientific terms. Mathematical formulae are kept to a minimum, and can safely be skimmed over, though a full appreciation of the graphs may require closer scrutiny. The photographs are quite stunning. As new techniques and more elaborate apparatus for exploring the universe are being developed, our knowledge and understanding are increasing exponentially. This excellent and comprehensive guide to the Milky Way may well be the definitive book on the subject for the time being, but it is unlikely to remain so for too long.