This is a book about a mathematical formula that nearly everyone—even those who are science-phobic—can recite, but almost no one can actually explain with the slightest degree of coherence. If pressed for details, many of us might draw a straight line between Albert Einstein’s tiny stroke of genius and the detonation of nuclear weapons a half-century later in the New Mexico desert and over the Japanese cities of Hiroshima and Nagasaki. That being the case, the formula E=mc2 evokes conflicting ideas about its meaning as a scientific artifact. We might think, on the one hand, of the young Einstein, laboring away as a frustrated patent clerk in Switzerland, writing a brief paper that shatters the science of physics with a mere five symbols. Viewed in this way, the formula helps us tell a heroic story about how outsiders and misfits often contribute in unexpected ways to the store of human knowledge. Or, less pleasantly we might imagine the horror of a city reduced to cinders by a single bomb whose explosive power owed everything to Einstein’s moment of insight. Here, the story of E=mc2 is a tragic one, reminding us of the worst ends to which human ingenuity can bring us.
David Bodanis’ fascinating little book does indeed tell us these stories, but it does much more than explain the origins and consequences of Einstein’s discovery that mass and energy are interchangeable, and that energy equals mass times the speed of light squared. Rather, the author, a former lecturer at the University of Oxford whose best-selling books range in topics from history to popular science, introduces readers to the assortment of characters who contributed to our understanding of the separate components of the formula itself. In short, accessible sketches, Bodanis summarizes the work of Michael Farraday, an English bookbinder’s apprentice who—by demonstrating that electricity and magnetism were linked—laid the foundation for the modern concept of “energy” in the early 19th century; Antoine-Laurent Lavoisier, the French chemist who vastly expanded our understanding of “mass” before losing his head in the French Revolution; Ole Roemer, the young 17th century Dane who confounded the greatest astronomers of his era by accurately predicting the speed of light; and Emilie du Chatelet, the now-forgotten wife of Voltaire who challenged Newtonian physics by demonstrating that energy could be calculated as mass times the squared velocity at which it travels. Like Einstein, none of these figures was regarded at the time of their discoveries as a leader in their respective fields; all were outsiders. Unlike Einstein, however, their contributions were largely forgotten by subsequent generations of scientists and historians. Bodanis’ book does an admirable job of rescuing them from the margins and offering them a place they deserve in the history of this vital equation.
Besides the biographical sketches (including Einstein’s) that comprise the first half of the book, E=mc2 pays all the necessary attention to the most dramatic application of the formula: the atomic bomb. There are other books that provide a more detailed (and better) account of the subject—Richard Rhodes’ The Making of the Atomic Bomb comes to mind—but Bodanis covers the history well enough, especially for readers unfamiliar with the central plot and major characters. And all readers, no matter how deep their background, will be impressed with Bodanis’ six-page description of what happened in the seconds after the bomb was triggered over Japan; there, the author slows down time to a near-standstill, as neutrons fired into the center of a uranium atom caused it to wobble and tear apart, setting off a chain reaction that altered our world forever.
The final section of the book returns the focus, appropriately enough, to the equation itself, which will continue to operate—regardless of whether humans are around to notice—until the universe creaks to a halt, 1032 years from now. In keeping with much of the rest of the book, Bodanis introduces us to another consensus-challenger, Cecilia Payne, the English-born astronomer whose studies of the sun during the 1920s proved that it consisted mainly of hydrogen. Her discoveries set the stage for others (like the Indian astronomer Subrahmanyan Chandrasekhar) who wondered what might happen when all the stars in the universe—following Einstein’s formula—converted their entire mass to energy and consumed every last speck of hydrogen. Taking into account the actual answers to those questions, and given Bodanis’ brief, compelling description of how the universe will end, readers will perhaps be relieved to remember that humans will have long traveled the route of the dinosaurs by then.
Overall, Bodanis is a talented storyteller with a skillful sense of how to show that E=mc2 formula is the product of human ingenuity and luck. He is also able to demonstrate how the formula—or rather the phenomenon it describes—is, at the bottom of it all, independent of all our efforts to understand and control it.