From 1980 through 1984, I worked on my PhD thesis, which dealt with the rather arcane topic of the energetic properties of certain chemical compounds. The branch of science that describes those energetic properties in terms of heat and work is called thermodynamics, and it is how I became familiar with the concept called “entropy.” Through the years I have noticed that the concept of entropy was used in many more fields besides physics and chemistry. Struck by the simplicity of thermodynamics, the fact that it had remained virtually unchanged for decades, and that the theory quietly determines many aspects of our daily lives, but not realized by many, I got the idea to write a book about it for the non-scientist.
So what is the purpose of this book, and what will the reader be left with? Succinctly stated, this narrative describes the discovery of an extremely powerful (and in essence simple) theory that fundamentally influences our society and our everyday lives. In doing so, this volume sketches the historical, social, and economical contexts that surround the development of thermodynamics. Without being subjected to a lot of formulas, the reader will gain a good impression of how the scientific and scientific and philosophical communities dealt with the entropy concept after its introduction, and how insight on the subject gradually increased. Chapters 1 and 2 follow the historical development of the thermodynamic theory, visiting the Second Law and First Law of Thermodynamics in chronological order – an approach that I believe will give readers a good sense of the problems that scientists wrestled with more than a century ago. (For instance, it was not until late in the 19th century that scientists began thinking of heat as a kind of fluid called “caloric,” comparable to the fanciful “aether” which was thought to transmit light waves in a vacuum.) In addition, readers will learn that thermodynamics theory was crucial to the birth of quantum mechanics and relativity, two earth shocking theories that transformed classical physics into modern physics. This book also will use familiar situations to illustrate theoretical concepts – for example, why can’t I get better gas mileage out of my car? How are the 10,000 kilo joules (which is 2500 kilo calories) s consume daily used in the body? What is the difference between heat and energy? Why does an air pump heat up when I use it to inflate my bicycle tires? Of course, a lot of attention is paid to steam engines, those industrial wonders that first inspired the study of thermodynamics, and we’ll also look at how thermodynamics reaches into areas outside science, such as art and religion.
The book is divided in two parts. In Part one, classical thermodynamics is discussed with a review and description of fundamental phenomena such as temperature and heat, followed by a detailed analysis of how mechanical theory (which deals with the laws of locomotion) developed over time, from Aristotle and the ancient Greeks to Newton, who completed the theory around 1600. Despite its tremendous success in explaining the orbits of planets and satellites (among other things), the mechanical theory failed to account for simple observations, such as the direction of heat flow and the occurrence of irreversibility (for instance, the forward-only direction of time). All the laws of Newtonian mechanics allow processes to go in either direction, and therefore cannot deal with these phenomena. We also touch several times on the direction of time and relate the past and future of the universe to the law of entropy, showing what the final consequences may be in the long term – such as the “Heat ” envisioned by Helmholz. Of course, we cannot ignore the colorful history of perpetual engines, and will portray a few of them. Then we extend our journey by considering the development of physics between 1800 and 1900, and we focus on a key interpretation of entropy developed by Ludwig Boltzmann around 1900. Boltzmann’s statistical mechanical theory clarified the relationship between entropy and the degree of organization of the atoms and molecules of a given system. Also, we seek to understand whether the birth of the new physical theories around 1900 – the quantum mechanical theory of Max Planck and the relativistic theory of Albert Einstein – had any impact on the theory of thermodynamics and whether, in turn, thermodynamics played any role in the creation of these theories. Before getting the answers to these questions, the reader receives a quick course – in layman’s terms – in the basic principles of both theories, and what led Planck and Einstein to create them.
In Part Two, we describe the impact of thermodynamics on our world. Entropy always increases; we can only minimize the amount of entropy production by making sure that the processes stay as close as possible to reversibility, which often means that processes must proceed at very low speed. Much of the energy wasted in modern industrial economies is the price we pay for speed. The high degree of irreversibility in many production processes (where high speed is often used in order to maximize “performance”) is in fact accelerating the entropy production of our world. As a result, compared to the medieval era, we are more rapidly approaching the heat situation which can also be taken as a measure of how quickly we are degrading our environment and essentially leaving less entropy for our children to work with. We also will show how environmental economists have used the concept of entropy and what conclusions they have drawn. A lot of progress in the development of thermodynamic theory was made by physicians such as Clausius, Mayer, and Helmholtz, and not by physicists. That was partly because the doctors wanted to understand the reasons behind the production of animal heat. At some point, there was an interesting theory that the friction of the stream in the veins produced body heat! It took some years before it became clear that combustion was the actual source. Undoubtedly, the reader will wonder how, despite the natural push for chaos engendered by the Second Law of Thermodynamics, nature has nonetheless created tremendously well-organized forms of life (DNA, for example). Sometimes it seems that Mother Nature is tending toward the creation of extremely complex systems, in defiance of entropy. The answer to this paradox is that we must first properly define the boundaries of the system we are considering. In this case, the boundaries of that system could be the entire world. When we do this correctly, we will conclude that the creation of life comes at the cost of available energy elsewhere in our system. In other words, the creation of life extracts lots of energy from other parts of the system, and so increases entropy.
Finally, we will go to quite different fields where entropy has played a role. Since Boltzmann’s invention of the statistical mechanical and interpretation of entropy, many people from widely divergent disciplines have speculated on how entropy can be used and should be interpreted, even in such unlikely areas as communication theory, religion, and art. The Appendices at the back of the book contain further examples and illustrations, such as the entropic cases for solar and nuclear energy, and whether the human body can be considered a heat engine. In summary, thermodynamics is a convincing illustration of the power of the human mind when applied to a very fundamental field, namely the understanding of energy transfers. As Einstein has said, it is safe to assume that this theory will live on forever, and will continue to provide our society with insights and guidance in energy conservation and many other areas. Throughout the book I have highlighted opinions of experts while trying not to give my opinions or interpretations on the subject. The reason is that what can be found in the mainstream literature is clear enough and more than sufficient for what we want to achieve here: to explain the birth and use of the concept of entropy. No need for more interpretations. It is my humble hope that the reader will enjoy the book as much as I have enjoyed carrying out the research and writing it. While preparing the manuscript I was encouraged and helped by a few people to whom I would like to express my sincere appreciation: Prof. Dr. Hilde Van Gelder (Catholic University of Leuven), Dr. Mart Graef (Philips Semiconductors), Drs. Martin Heerschap (General Electric Financial Services), Dan McGowan (SEMATECH) Dr. Paul Newman (Univ. of Texas), Ron Schmitz, Lucas Schmitz and Prof. Dr. Ir. Jan Steggerda (emeritus professor Catholic University of Nijmegen). Also, very stimulating inputs and ideas were given by Millicent Treloar from William Andrew Publishing.
 However, also those with a background in thermodynamics obtained during their engineering studies will find many topics they were not aware of such as in the social and economic fields outside chemistry and physics where the concept of entropy has been used. Although we cannot escape a few very fundamental ones (à la E=mc2). “By following the historical development of the subject usually more knowledge can be gained than by inspecting the polished final product”, quote from Walter Moore in his book Physical Chemistry.