by David A. Weintraub. Since astronomers already know the answer to this eponymous question to an accuracy of better than one percent (13.7 billion years), this book might perhaps be more aptly titled How Do We Know How Old the Universe Is? Throughout the text, Weintraub (astronomy, Vanderbilt Univ.; Is Pluto a Planet?: A Historical Journey Through the Solar System) takes the reader steadily outward, explaining step by step how astronomers have gleaned key information from clever observations and a grounding in testable principles of physics. Unfortunately, once he begins his discussion of dark matter (about two-thirds of the way through), the science behind the claims of what is well known goes largely unexplained. Since he has done such a wonderful job of it up to this point, readers may forgive the necessity, especially since a graduate course or two would be required to follow all the intricacies. VERDICT Weintraub outlines the rigorous process astronomers have followed from Earth itself out to the edge of the observable universe and makes it accessible to the science-minded lay reader. Highly recommended. --Library Journal
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