Some years before warped space and light bent by gravity made him a global celebrity befriended by film stars and mobbed by crowds, Albert Einstein had been a lowly third-class technical expert at the Swiss Patent Office in Bern. There, as he worked on the theory of relativity in his spare time, Einstein sorted out inventions that were just about feasible from those fatally flawed.
The practical application of physics was something that Einstein returned to in 1926 after reading about the deaths of an entire family due to inhaling poisonous fumes from a faulty refrigerator. As Paul Sen explains, the tragedy motivated Einstein to collaborate on designs for safer refrigerators that eventually led to some 45 patents in six different countries.
An award-winning science documentary film-maker, Sen knows how to grab the attention of an audience. Einstein’s Fridge may be the title but the clue as to the true scope and ambition of this elegantly written and engaging book lies in the subtitle. Thermodynamics is Sen’s “science of fire, ice and the universe” and it lies at the heart of much that we take for granted, from fridges to the biochemistry of life-saving drugs.
Together with energy, concepts such as entropy, heat and temperature may not sound as fascinating as the mysteries of quantum mechanics but they and the laws of thermodynamics govern everything from the behaviour of atoms to that of living cells, from the workings of car engines to the radiation emitted by black holes. Einstein said that thermodynamics “is the only physical theory of universal content which I am convinced will never be overthrown, within the framework of applicability of its basic concepts”.
Energy is one of these fundamental components and it cannot be created or destroyed; it can only be converted from one form to another. A pendulum, for example, converts potential energy into kinetic energy and vice versa as it swings to and fro. At the ends of the swing there is only potential energy and only kinetic energy at the bottom of the arc. Basically: you can’t get something for nothing. So deep-seated is this fact about nature that it’s enshrined, in more sober scientific terms, as the first law of thermodynamics.
Sen maintains that the history of science is the history that really matters and it’s easy to see why as he points out that thermodynamics explains why we must eat and breathe and also how the universe will one day end. We learn that it was William Thomson, later better known as Lord Kelvin, who coined the term “thermodynamics” in 1849, after reading the work of Sadi Carnot, a former French military engineer who died in a mental asylum aged just 36.
The fact that coal in France cost three times more than in England’s industrial heartland due to difficulties in extracting and moving it, meant the French engineers were interested in improving the efficiency of steam engines. Carnot was no exception, but his approach to learning how to extract the maximum amount of work out of burning a given amount of coal relied on understanding the operations of an imaginary, ideal engine. Carnot summarised his methods and results in Reflections on the Motive Power of Fire (1824) but hardly anybody noticed. It was Kelvin who saved Carnot from obscurity by hailing his work as “an epoch-making gift to science”.
An even more important contribution was the formulation in 1850 by German scientist Rudolf Clausius of the second law of thermodynamics: heat will not pass spontaneously from a colder to a hotter body. Heat, the transfer of energy from A to B due to a temperature difference, explained such everyday occurrences as a hot cup of coffee getting cold and an ice cube in a glass of water melting. But left undisturbed, the reverse never happened. Why not? Entropy was Clausius’ answer. It’s a measure of the randomness or disorder of a system and explains why some processes occur in nature and others do not. A cold cup of coffee spontaneously getting hotter would lead to negative entropy, something nature abhors and so is forbidden.
It’s a measure of Sen’s achievement that by combining science, history and biography he takes us on a successful tour through thermodynamics beginning with the seminal contributions of Carnot and Clausius, via those of an English brewer, a German doctor, a Scottish laird and an Austrian genius to the work of Jacob Bekenstein and Stephen Hawking on black holes and entropy. As such, Einstein’s Fridge is the story of the science of our past, present and future — from the steam engine to that of evaporating black holes at the end of the cosmos.
Einstein’s Fridge: The Science of Fire, Ice and the Universe, by Paul Sen, William Collins, RRP£20, 320 pages
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