This is a book review of Reversing the Arrow of Time by Bryan W. Roberts.
Reversing the Arrow of Time, by Bryan W. Roberts (Cambridge University Press), 2022. Pp. 263, 25 x 19.5 cm. Price £29.99/$39.99 (hardbound, ISBN 978 1 009 12332 7).
Roberts, a philospher of physics and associate professor at the London School of Economics and Political Science (where he is director of the Centre for Philosophy of Natural and Social Sciences), explores not only the statistical-mechanics and cosmological arrows of time, but also others (radiation, quantum collapse, and causal structure), concluding that all of those "misfire" in the sense that they are not true arrows of time at a fundamental physical level. Possible reasons are resorting to heuristics, relying on boundary conditions, and describing a situation with missing information. It is not that those bogus of arrows of time are unimportant; indeed, they can provide a good explanation for our asymetric experiences. Most important for cosmology is the "past hypothesis" that the Universe started in a low-entropy state. But that discussion doesn't occur until the fifth (of eight) chapters. The first four provide a brief introduction to and a very detailed discussion of the problem from both mathematical and philosophical points of view. In addition to physics, there is a huge amount of detail here, probably unfamiliar to many readers. By contrast, there is little exposition of the various arrows of time themselves, but most readers probably need nothing more than a definition and brief description. The book is complementary to many discussions about (real or imagined) arrows of time in physics, and is clearly written despite the philosophical and mathematical details.