Four laws that drive the universe
Peter Atkins
Oxford: OUP 2007 | Pp130 | £9.99 | ISBN0 199 23236 9
Reviewed by Peter Hughes

Peter Atkins is a writer who expresses complicated ideas simply and accurately by using clear and precise language. Thermodynamics is notoriously difficult to write about without the use of rigorous mathematics and the success of the author's The Second Law  and Galileo's finger  shows how well he has succeeded to date. His latest book lives up to his earlier high standards.  

The title may surprise some people, who may claim that there are only three laws, but in this book Atkins, quite rightly, emphasises the importance of the Zeroth Law in establishing the concept of temperature. He skilfully dismisses the false concept that heat is a form of energy in favour of the correct one that 'heat is mode of transfer of energy'. Many people may feel that there is nothing new to say about the First Law. For them, I suggest they read the lucid paragraphs on the fluctuation-dissipation theorem and Noether's theorem, both of which give additional insight into the well-known conservation of energy criterion.  

Atkins' treatment of the Second Law follows the familiar route he has made so popular in his lectures and writing. In a heat engine, he rightly emphasises the importance of the cold sink which, when heat is absorbed, produces a gain in entropy to counterbalance the loss of entropy caused by removing thermal energy from the hot body. He uses his well-known analogy of the disturbance caused by a sneeze in a quiet library compared to that caused by a sneeze in a busy street to show the importance of the background noise (temperature) when considering entropy increases. He finishes the chapter by considering how population inversions may be regarded as negative temperatures, and the implications of entropy changes during heat transfer under these conditions.  

Atkins minimises the importance of the Third Law, pointing out that it is not necessary that the entropy of all substances should approach zero as the temperature is reduced, merely that they should approach the same value. 

Sixthformers (and their teachers) will gain much from this book and it would provide an excellent semi-qualitative introduction for undergraduates before they tackle the standard textbooks. Written by a chemist with chemists in mind, the concepts of enthalpy changes and free energy changes (both Helmholtz and Gibbs varieties) are given an extensive airing even though, as the author points out, they are not fundamental concepts of thermodynamics but are really convenient book-keeping exercises.  

I find students who have been introduced to entropy via physics are often mystified when they meet a chemical reaction that involves a decrease in entropy. The new A2 syllabuses for chemistry will introduce the concept of entropy and I hope this topic may be an opportunity for chemists, physicists and biologists to present a united thermodynamic front. This book will certainly help.