A major problem with quantum mechanics is that the dominant Copenhagen interpretation is not conducive to providing visual images of what is going on. With special and general relativity, the initially unsettling ideas that time and distance are not invariants but depend upon the state of motion of the observer and that space can be warped by the presence of mass and energy have gone mainstream. Not so with quantum mechanics. Although of the same vintage as relativity, quantum mechanics has continued to greatly perplex people because it undermines the realist position that other theories, including relativity, take for granted, of a world existing independent of the observer, whose features we can discover by making observations. The denial of this made even Einstein uneasy.
This has resulted in two approaches to the subject. One is a hard-nosed attitude that argues that scientific theories are not obliged to provide us with visualizations of processes that take place beyond the reach of our sensory capabilities. Instead, we should simply use the mathematical machinery of quantum mechanics to calculate quantities of interest that can be measured, something that it has been remarkably successful in doing. P. A. M. Dirac's words that “the main object of physical science is not the provision of pictures, but is the formulation of laws governing phenomena and the application of these laws to the discovery of new phenomena” are often quoted to support this view. However, such a level of operational expertise and understanding is only available to those willing to spend many years studying the subject.
We also have a proliferation of books and articles that take the alternative approach that strives to provide the general public with some kind of understanding of what is “really” going on using metaphors and analogies and no mathematics. Unfortunately, some authors who write in this vein have exaggerated the strange aspects in order to make all manner of metaphysical claims that have little basis in the actual theory.
Ball's book belongs in the second category but seeks to correct popular misconceptions that have emerged from such efforts. His argument is that quantum mechanics is strange but not always in the way that people think and that recent experiments have provided insight into what had earlier been purely intellectual speculations about what it all means.
His book consists of two parts. He starts with familiar quotations from Niels Bohr (“Anyone who is not shocked by quantum theory has not understood it”) and Richard Feynman (“I think I can safely say that nobody understands quantum mechanics”) which emphasize the strangeness of quantum mechanics. He tries to demystify what we might call “quantum mechanics greatest hits”: Heisenberg's Uncertainty Principle, Schrödinger's cat and the superposition of states, wave-particle duality, measurement and wave function collapse, the double-slit experiment, non-locality, the EPR paradox, and Bell's theorem. I would venture that most physicists would not find much that is new in this largely historical overview.
In the second part, Ball goes into more recent areas of research which are less familiar and would be of interest even to professional physicists. Ball argues that ultimately quantum mechanics is not a theory about how tiny particles behave but instead comprises a set of rules for representing and manipulating information (a notoriously slippery concept) and the causative influences involved in a system and about what is and is not knowable about it. He uses that framework to discuss recent advances in entanglement, quantum cryptography, quantum teleportation, quantum computing, and the Many Worlds interpretation and other alternatives to the Copenhagen interpretation.
For example, he presents the view that the measurement process (in which a superposition of quantum states interacts with a classical macroscopic detector) does not mean that the coherent entangled wave function has instantaneously collapsed but that the initial state rapidly spread its entanglement to the detector elements and the rest of the environment, a process known as decoherence. This imprints information about the initial quantum state onto its environment, but since detectors are able to reflect only part of that information, it appears as if the wave function collapsed.
There are some minor annoyances. The subtitle uses a familiar internet clickbait trope of making a provocative but unjustifiable sweeping claim. The initial reaction of this reviewer was “Really? Everything? How do you know what I know?” If readers are willing to get past that initial negative reaction, they will find that Ball writes well and treats his subject seriously and not sensationally. Another problem is the lack of in-text citations to the bibliography. Their absence hinders attempts to read more deeply on the topics, and the skimpy notes section is of no help. A third irritant that could have been easily avoided is that although the book is split up into chapters, there are no chapter numbers and no table of contents. If one wants to refer to material elsewhere in the book, one has to flip through the pages to find the relevant section. It makes even this review less helpful because I cannot point readers to the chapters where specific topics are discussed.
As with all such books that seek to explain this essentially mathematical theory without mathematics, the result is a series of assertions that readers have to simply accept at face value and can result in some of them rapidly feeling out of their depth. But all in all, this is a worthwhile addition to the many books that seek to make quantum mechanics understandable.
Mano Singham is a theoretical nuclear physicist and retired director of the University Center for Innovation in Teaching and Education at Case Western Reserve University. His interests extend to the history and philosophy of science, epistemology, and learning theory. His latest book The Great Paradox of Science: Why its Theories Work so Well Without Being True will be published in 2019 by Oxford University Press.
