Where does the time go? Independent physicist Barbour presents an unusual alternate to the standard way of viewing the four-dimensional universe (three spatial dimensions and time), beginning with how our perception of time is formed. Time, he says, does not exist apart from events: the motions of the sun and the stars, the mechanical movement of a clock. Rather than truly feeling the passing of time, we merely note changes in our surroundings, described by the author as a series of "Nows," like frames of a motion picture. Not only do Nows exist for the events that actually occur, but a large number of Nows represent alternate possibilities, inhabiting a land called Platonia. Which Nows become our perceived reality? The rule of thumb Barbour gives is, "only the probable is experienced." In the "macro" world, the author addresses determinism, Newtonian mechanics and the second law of thermodynamics as they relate to his theory of Nows. In the quantum mechanical realm, he ties his theory of time to the Schrodinger Equation in its various forms. Throughout, the author accompanies his theories not with complex equations but rather with elegant (if sometimes convoluted) diagrams. If these theories sound intriguing, readers already familiar with the Wheeler-DeWitt and Schrodinger equations, eigenstates and wave functions may appreciate this unique perspective. Ultimately, however, Barbour's attempts to "simplify" physics, in particular quantum mechanics, will confuse as many readers as they enlighten. 20 illustrations. (Feb.)

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