A British physicist looks at some of the enigmatic propositions created by his colleagues over the ages.

Al-Khalili (Quantum Physics/Univ. of Surrey; *The House of Wisdom: How Arabic Science Saved Ancient Knowledge and Gave Us the Renaissance*, 2011, etc.) begins with a few “warm-ups” including “The Game Show Paradox,” in which a contestant considers three doors, one of which conceals a prize. After the contestant chooses one, the host then opens another, which proves not to be the winner, and asks the contestant if she would like to change her choice. In defiance of common sense, it is advantageous to do so; Al-Khalili summarizes the probabilities behind the puzzle. Some of the greatest logical puzzles were the work of the Greek philosopher Zeno, who seemed to prove that motion is impossible. His demonstration seemed annoyingly irrefutable until the development of mathematical tools, such as calculus, for describing change over time. Olbers’ Paradox, on the other hand, revealed deep truths about the universe by asking why the sky is dark at night. Maxwell’s Demon, an imaginary creature that can control individual molecules to overthrow entropy, raises similarly deep issues of fundamental physics. Possibly the most familiar paradox of quantum theory is Schrodinger’s Cat, whose life and death depends on the decay of a radioactive atom in a given stretch of time. Fermi’s Paradox is another that raises questions about the larger universe: If technologically advanced civilizations are common in the universe, why haven’t they visited us? Al-Khalili gives detailed answers to each of these, plus several that grow out of Einstein’s theory of relativity and the possibility of time travel. He ends with a list of unsolved problems of science and a look at the recent question about whether neutrinos have been found to travel faster than light.

An often-entertaining introduction to basic principles of science and philosophy.