What on earth is Bill Bryson doing writing a book of popular science-A Short History of Almost Everything? Largely, it appears, because this inquisitive, much-travelled writer realised, while flying over the Pacific, that he was entirely ignorant of the processes that created, populated and continue to maintain the vast body of water beneath him. In fact, it dawned on him that "I didn't know the first thing about the only planet I was ever going to live on". The questions multiplied: What is a quark? How can anybody know how much the Earth weighs? How can astrophysicists (or whoever) claim to describe what happened in the first gazillionth of a nanosecond after the Big Bang? Why can't earthquakes be predicted? What makes evolution more plausible than any other theory? In the end, all these boiled down to a single question-how do scientists do science? To this subject Bryson devoted three years of his life, reading books and journals and pestering the people who know (or at least argue about it); and we non-scientists should be pretty grateful to him for passing his findings on to us. Broadly, his investigations deal with seven topics, all of enormous interest and significance: the origins of the universe; the gradual historical discovery of the size and age of the earth (and the beginnings of the awesome notion of deep time); relativity and quantum theory; the present and future threats to life and the planet; the origins and history of life (dinosaurs, mass extinctions and all); and the evolution of man. Within each of these, he looks at the history of the subject, its development into a modern discipline and the frameworks of theory that now support it. This is a pretty broad brief (life, the universe and everything, in fact), and it's a mark of Bryson's skill that he is able to carve a clear path through the thickets of theory and controversy that infest all these disciplines, all the while maintaining a cracking pace and a fairly judicious tone without obvious longueurs or signs of haste. Even readers fairly familiar with some or all of these areas of discourse are likely to learn from A Short History. If not, they will at least be amused-the tone throughout is agreeable, mingling genuine awe with a mild facetiousness that often rises to wit. One compelling theme that appears again and again is the utter unpredictability of the universe, despite all that we think we know about it. Nervous page-turners may care to omit the sensational chapters on the possible ways in which it all might end in disaster-Bryson enumerates with cheerful relish the kind of event that makes you want to climb under the bedclothes: undetectable asteroid colliding with the earth; superheated magma chamber erupting in your back garden; ebola carrier getting off a plane in London or New York; the HIV virus mutating to prevent its destruction in the mosquito's digestive system. [+]