E=mc squared by David Bodanis

I'd like to thank one of our daughters, who urged me to purchase a used copy of this book at one of the bookstores in Stratford, ON. I'm glad she did.

David Bodanis begins E=mc2: A Biography of the World's Most Famous Equation (New York: Berkley Books, 2000) with a story that Cameron Diaz, the movie actress, was once asked, in an interview, if there was anything that she, Diaz, wanted to know. She supposedly replied that she would like to understand Einstein's famous equation. Perhaps she read this book. It doesn't impart complete understanding of the equation, but it helps.

Bodanis' book is about the history of science. He introduces a number of ideas, and some of the characters who were important in developing those ideas. He has written things about E, m, c, and 2 that I didn't know before I read the book, and about scientists that I had not heard of.

Here he is on the velocity of light:

[Einstein's] new realization about light changed everything; for the speed of light becomes the fundamental speed limit in our universe: nothing can go faster. . . . light isn't just a number, it is a physical process. There's a big difference. If I say that -273 . . . is the lowest number that there is, you could rightly answer that I'm wrong: that -274 is lower, and -275 is lower yet, and that you can keep on going forever. But suppose we are dealing with temperatures. The temperature of a substance is a readout of how much its inner parts are moving, and at some point they're going to stop vibrating entirely. That happens at about -273 degrees on the centigrade scale, and that's why -273 degrees is said to be "absolute zero" when you're talking about temperature. Pure numbers might be able to go lower, but physical things can't: a coin or a snowmobile or a mountain can't vibrate any less than not vibrating at all.

So it is with light. The 670,000,000 mph figure that Roemer measured for the light speeding down from Jupiter is a statement about what that light is like. It's a physical "thing." (p. 50)

I've been studying, and teaching, science for about a half century, and I had never thought to put it that way before.

Bodanis explains that celeritas, a Latin word meaning "swiftness," is the origin of the use of c for the velocity of light.

He told me some things about women scientists that I wish I had known before. One such woman was Emilie du Châtelet, who added to Newtonian physics the idea that there is such a thing as energy, which exists in many forms, one of them being kinetic energy (the energy an object possesses due to its motion) which, she found, is proportional to the mass of the moving object times its velocity squared. du Châtelet died in childbirth at 40. He also writes about Lise Meitner, who worked out the details of fission, and Cecelia Payne, who made fundamental discoveries about the composition of stars, but was not given a position at Harvard for many years, because of her sex. (Meitner now has an element named after her, so her achievement is recognized, but she was treated shamefully during her lifetime, by a co-worker.) Bodanis also writes about male scientists, lest there be any doubt.

Bodanis covers some interesting history. There are conflicting opinions about the role of Werner Heisenberg in the unsuccesful German atomic bomb program. Bodanis believes that he wanted to succeed, but was thwarted by allied sabotage. He also blames James F. Byrnes, a South Carolinian who advised Truman, for the fission bombing of Japan, when Japan was already close to surrender. There are alternative views on these opinions. He writes that Einstein's famous letter to President Roosevelt, urging US development of the bomb, was ignored. He credits Oppenheimer for his superb administration of the US atomic bomb program.

Most scientifically literate people understand that Einstein's famous equation is a by-product of his special theory of relativity, which is not principally about the equivalence of matter and energy, but about relative motion. I suspect that, like me, they might learn a great deal more about these matters, and other things, from Bodanis' book.