E=mc2 · A Biography of the World's Most Famous Equation

**Our Review**

In his introduction, author David Bodanis relates the story of the genesis of this book. He was reading an interview with Cameron Diaz where the interviewer asked if there was anything else the actress wanted to know, and she said, "What does E=mc2 really mean?" Dubbed in the subtitle "The World's Most Famous Equation," E=mc2 falls into the larger category of things people feel they should comprehend. As Bodanis points out, it seems like Albert Einstein's little formula should be understandable -- after all, it only consists of five symbols!

The first part of the book takes each of those five symbols in turn and explains its history. E stands for energy; = for equals; m for mass; c for the speed of light; and the superscript 2 for squared. There was a time before any of these symbols existed; even the = sign had a sputtering start. It is only in the past couple of hundred years that humanity has come to understand that energy is something to be measured and that it has the ability to change. These properties were discovered and refined by people like Michael Faraday, who in the 19th century made the connection between electricity and magnetism. Likewise, Antoine Laurent Lavoisier -- whom Bodanis characterizes as "an accountant with a soul that could soar" -- was instrumental in observing the conservation of mass. These discoveries laid the foundation for Einstein's astonishing insight that energy and mass can actually convert into each other. The speed of light (186,000 miles per second) multiplied by itself is a pretty hefty number, so it doesn't take very much mass to convert into a vast amount of energy. Bodanis continues with a concise chronology of how that knowledge was turned into history's most infamous weapon, the atomic bomb, recounting such exploits as the World War II raid to disable Germany's heavy-water plant. That same equation has been with us always, though. Long before the Manhattan Project, E=mc2 made the stars shine -- including our own star, the sun.

*E=mc2* accomplishes exactly what it sets out to do. By the end, readers know what the equation is and what it does, without having to swim through a lot of other theories and equations.

*--Laura Wood, Science & Nature Editor*