The quantum question

Beyond measure: modern physics, philosophy and the meaning of quantum theory
Jim Baggott
Oxford, UK: OUP 2003 | Pp xvi + 380 | 20.00 (SB) | ISBN 0198525362
Reviewed by Peter B. Karadakov

At first glance, it may appear that this extensively revised new version of Baggott’s book is essentially a non-mathematical introduction to quantum mechanics for those who are ready to give up their attempts to understand the subject as soon as they encounter a couple of equations. In fact, Beyond measure proves to be much more than that: it provides a fascinating account of the history of quantum theory, easy-to-follow guidance in a wide range of quantum principles, and an intriguing discussion of the impact of quantum ideas on modern philosophy.

The book is divided into five parts: discovery, formalism, meaning, experiment and alternatives. None of these, even the section on formalism, confront the reader with intimidating mathematical detail. Equations are almost entirely banished to a set of 27 clearly written appendices. These are not required for understanding the main text but provide a useful bridge between Baggott’s non-mathematical approach and the rigour of standard quantum mechanics textbooks.

Despite the fact that Beyond measure gets closer to laying out a ’royal road’ to quantum mechanics than a number of scientists would consider possible, it is not just the uninitiated who could benefit from this book. Many of those who use or teach quantum theory on a daily basis have learned it within the framework of the orthodox ’Copenhagen’ interpretation, which Baggott proposes is ’.quite simply, not meant to be understood’. To grasp the conceptual and philosophical limitations of this interpretation, revealed in the last three parts of the book, can be far from straightforward, especially if one is already well-versed in the accompanying mathematical formalism.

For anyone with more than a passing interest in the quantum world, Baggot’s book should prove difficult to put down after reading the first couple of pages: I am tempted to say that it very much does for quantum theory what Hawking’s A brief history of time did for astronomy and cosmology. To help those who wish to discuss the book and quantum theory in general, the author has launched a website, which features a forum with several discussion topics: history, formalism, philosophy and interpretation, experiment and alternative interpretations.