Stephen Hawking described it as 'the discovery of the century, if not of all time', yet the scientists who first detected the cosmic radiation that was identified as the afterglow of the big bang had to admit that it was more by accident than intention. At first its discoverers mistook the readings for the disruption caused by the droppings of pigeons that had nested in their telescope, and yet they went on to win the Nobel prize. In the mid-1990s, ''New Scientist'' writer Marcus Chown drove across America to interview the key scientists who had made this astonishing discovery. Their account and Chown's description of their achievement was published to much acclaim. But now, over a decade later, in this new and fully revised edition, he goes behind the hype and the hysteria to provide a clear and lively explanation of one of the biggest discoveries in modern science - and a brilliant picture of what happened next.