Reviews

A central question underlies this brief but crystal-clear account of the history of physical speculation about the universe: does the universe always operate in the same manner or does it allow for divergence? That the universe is static, as once thought, eventually proved impossible to reconcile with evidence from astronomy, for how could an expanding universe follow unchanging laws of nature? Hawking, along with mathematician Roger Penrose, discovered the answer: relativity theory not only allows, but requires, a big bang. The discussion does not end therethe universe may really be static, the ``big bang'' being local history in only a part of the universebut once again Hawking has proved himself a pioneer. David Gordon, Bowling Green State Univ., Ohio

Hawking's discovery that black holes emit particles caused great excitement among astronomers. In this succinct overview of current theories of the cosmos, the Cambridge University physicist modestly weaves in his own notable contributions while giving due credit to his colleagues. He explains why relativity implies that a ``big bang'' occurred and examines string theory, which posits a universe of 10 or 26 dimensions. His understanding of time's flow leads him to conclude that intelligent beings can only exist during the expansion phase of our increasingly chaotic universe. New research on black holes and subatomic particles holds implications for scientists who, like Hawking, are attempting to devise a unified theory linking Einstein to quantum mechanics. The merit of this book is Hawking's ability to make these ideas graspable by the lay reader. (April)