Manjit Kumar, contributor
MOST of us have a vague idea of what energy is, if only because we have to pay for it. We know that it is the E in Einstein's famous equation, E=mc2, and all of us have an opinion about the pros and cons of nuclear energy. For William Blake's devil in The Marriage of Heaven and Hell, energy was "eternal delight", yet Newton never fully appreciated the importance of a concept that was rarely used until the 19th century.
So, what is energy? Easy to ask the question but, as Jennifer Coopersmith shows in Energy, the Subtle Concept, finding the answer was a messy and tangled affair, involving plenty of argument and controversy. It's a tale of persecuted genius, of royal patronage, of social climbers and dreamers, of rich men and poor men, a foundling, entrepreneurs and industrialists, lawyers, engineers, a taxman, a spy and a brewer. Some were showered with honours, others neglected until long after death.
The concept of energy is hard to grasp because it is something that cannot be directly observed. It was only in the early 19th century that it was even recognised as a distinct physical quantity. Since then it has played a vital role in the development of science and technology. Its importance lies in the fact that it possesses the very rare property of being preserved. Energy cannot be created or destroyed; it can only be converted from one form to another. So fundamental is this property to nature that it is enshrined, in more sober scientific terms, as the first law of thermodynamics.
The first step on the long road to understanding the true nature of this relationship had been taken in the 1800s by Benjamin Thompson, an Anglo-American physicist, inventor and soldier of fortune. While supervising the boring of new cannons Thompson realised that heat might be a form of motion rather than a special weightless substance called "caloric". Most remained unconvinced, largely because Thompson was a notorious opportunist and spy. The turning point came in the form of experiments performed, in the 1840s, by English brewer and amateur scientist James Prescott Joule, who introduced the term thermodynamics.
The conservation of energy is arguably the most important law in physics. But what exactly is being conserved? Are some forms of energy more fundamental than others? You will have to read the book to find out. Coopersmith sets out to answer such questions and to explain the concept of energy through the history of its discovery. This is neither a straightforward narrative nor one for the faint-hearted. Those not put off by the odd bit of mathematics, will be well-rewarded by dipping into this book.(Image: Theo Allosf/Corbis)
Energy, the Subtle Concept: The Discovery of Feynman's Blocks from Leibniz to Einstein
by Jennifer Coopersmith
Oxford University Press