Many physicists sidestep the philosophical puzzles altogether, preferring to “shut up and calculate.”

If quantum mechanics can be said to have a capital city it is surely Copenhagen, birthplace of the physicist Niels Bohr (1885−1962) and of the formalism he and others developed to make sense of the subatomic realm. Their approach, the “Copenhagen Interpretation,” is expounded in every textbook. Yet it has been questioned many times, and in “What Is Real?” Adam Becker tells a fascinating if complex story of quantum dissidents. Two of the most important not only displeased Bohr, they also attracted the attention of the FBI.