EINSTEIN'S FRIDGE

A fine account of thermodynamics.

Though there are four, Sen focuses “on the discovery and consequences of the first and second laws of thermodynamics.” The energy of the universe is constant. It can be transformed from one form to another but never created or destroyed, and the entropy (i.e., disorder) of the universe is steadily increasing. These two ideas represent “a scientific milestone every bit as significant as Newton’s laws of motion, which were published two centuries earlier.” Although simple, they require a good deal of explanation for general readers, but Sen knows his business and remains lucid throughout the narrative. For almost 200 years after its invention, the only significant mechanical source of power was the steam engine. Engineers eventually improved it, but Sen concentrates on the scientists who explained it. Sadi Carnot (1796-1832), known as “the father of thermodynamics,” wrote that an engine works by moving heat from a hot reservoir to a cold one. To increase engine efficiency, one must increase the temperature difference. “The production of heat alone,” wrote Carnot, “is not sufficient to give birth to the impelling power: it is necessary that there should also be cold.” Heat never flows from cold to hot without energy input; a refrigerator generates a great deal of heat. Since temperature difference limits efficiency, it can never reach 100%; anything that uses energy wastes a portion of that energy. The unnerving consequence of this waste (entropy) is that the universe will eventually cool and lose energy until it can no longer support life—but not for a long time. Sen includes enjoyable accounts of some of the Victorian Age geniuses (Joule, Kelvin, Helmholtz, Clausius) who worked out the elements of thermodynamics as well as those in the 20th century (Einstein, Turing, Shannon, Hawking) who applied it to the modern age and demonstrated that information and communication technology obey the same laws.

A lesson in how to do popular science right.