The arrow of time and the meaning of quantum mechanics are two of the great mysteries of modern physics. This important book - written for non-specialist readers, as well as physicists and philosophers - throws a fascinating new light on both issues, and connects them in a wholly original way. In considering attempts to understand the arrow of time in physics, Huw Price shows that for over a century physicists have fallen repeatedly for the same trap: treating the past and future in different ways. To overcome this natural tendency, we need to imagine a point outside time - an Archimedean viewpoint, as Price calls it - from which to think about the arrow of time in an unbiased way. Taking this Archimedean viewpoint, Price asks why we assume that the past affects the future but not vice versa, and argues that causation is much more symmetric in microphysics: to a limited extent, the future does affect the past. Thus he avoids the usual paradoxes of quantum mechanics, without succumbing to the rival paradoxes of causal loops and time travel.