Brian Cox and Jeff Forshaw are both renowned professors of physics and so are more than qualified to know both why E=mc² and why we should care.  However, it is one thing to understand such a theory yourself, yet quite another to be able to explain this to an audience of non-physicists whose lack of mathematical knowledge is such that they “can’t remember Pythagoras” theorem” (xi).  In this book the authors manage effectively both to explain why E=mc² and to convince us that we ought to care. 

The first half of the book sets out to explain how Einstein arrived at the equation E=mc².  In order to do so the authors are clearly required to introduce many concepts which, to the non-initiated, appear counterintuitive.  Through their use of everyday examples they very quickly lead the reader to accept there is no such thing as absolute motion, and subsequently proceed skillfully to explain the apparently even greater counterintuitive idea that there is no such thing as absolute space.  In Chapter Two they go one step further and dismiss the concept of absolute time by introducing the notion of the speed of light.  In order to do this they concentrate on the work of the physicists that Einstein built his theory upon, such as Faraday and Maxwell, and explain their importance to the subsequent development of Einstein’s own work.  By the end of Chapter Two the uninitiated reader has already been left in a state of discomfort.

In Chapter Three the authors introduce Einstein’s theory of special relativity. The first part of this is fairly easy for anyone to follow, thanks to their use of basic thought experiments.  However, for the first time in the book the authors then introduce principles of mathematics, including equations.  Although this is necessary for the logical development of the book it is, at this point, that some readers might be scared away.  However, the reader’s perseverance with the book will be rewarded.

The concept of space-time, perhaps the most difficult aspect of the book to understand, is introduced in Chapter Four.  However, Cox and Forshaw do remarkably well to keep the reader engaged through their discussion of some particularly difficult mathematical concepts.  They then finally reach the climax of the first part of the book — why E=mc².  Assuming that the reader has managed to keep up (and it is worth doing so), it is quite a satisfying point to reach.

The second part of the book, which in essence is the ‘why should we care’ part of its title, is perhaps easier to understand yet equally informative   The authors demonstrate, with clarity and ease, how Einstein’s theory of special relativity is important in all aspects of our lives, from our own existence to the workings of everyday objects such as PCs.

The final chapter of the book is perhaps the most complicated, though it is not central to its aim.  In it the authors provide a taster of Einstein’s theory of general relativity and the concept of warped space-time.  Although this chapter is difficult to follow, it certainly made this reader keen to read further — although gaining a physics degree first might be advisable.

Overall the book is an entertaining and enlightening read.  It is perhaps not quite as easy to understand as the authors claim in their preface, but this is perhaps inevitable given the subject matter.

© 2010 Stephen Chadwick

Stephen Chadwick, PhD teaches on the Philosophy program at Massey University, New Zealand.