WHY DOES E=MC2:
(And Why Should We Care?)
By Brian Cox and Jeff Forshaw
Da Capo, 264 pp., illustrated, $24
BEFORE THE BIG BANG:
The Prehistory of Our Universe
By Brian Clegg
St. Martin's, 320 pp., $25.99
E=mc{+2} is the supermodel of equations. It’s a fashion brand and a Mariah Carey album. Sculptures are made out of it; energy drinks are named for it. The formula is 104 years old, but it’s still sexy, if you know what I mean.
Actually, what do I mean? E=mc{+2}? Einstein wrote it down first; I’ve got that. But that’s about as far as I can get on my own. Thankfully, a couple of patient Englishmen have written “Why Does E=mc2: (And Why Should We Care?)’’ to help willing souls dig a bit deeper.
Brian Cox is a particle physicist. Jeff Forshaw is a theoretical physicist. Cox also is one of People magazine’s “sexiest men alive.’’ Forshaw, presumably, doesn’t let that get to him. Together the authors present a mild-mannered, digressive, mostly math-free walk-through of the world’s most famous equation.
“What E=mc{+2} says,’’ our guides tell us, “is that energy and mass are interchangeable, much like dollars and euros are interchangeable, and that the speed of light is the exchange rate.’’
Let’s say you had a kilogram of stuff. And let’s say I did something to your stuff to make it disappear. Now that your stuff is gone, Einstein’s equation demands that a kilogram’s worth of energy must remain behind. I’ve exchanged your mass for energy.
“Before Einstein,’’ Cox and Forshaw write, “no one had dreamed that mass could be destroyed and converted into energy because mass and energy seemed to be entirely disconnected entities.’’ Common sense suggests energy and mass are different things. Space and time seem to be, too. But common sense, the authors remind us, is often dead wrong.
One way to look at the history of modern science is to say that it represents a century-by-century reordering of common sense. Copernicus showed us we weren’t standing still at the center of the universe. Galileo showed us that all motion is relative depending on who observes it. Darwin showed us that our bodies and minds are the result of eons of natural selection. None of these things seemed true at first glance.
Then Einstein came along and proved that not only is motion relative, but so are space and time. No absolute, celestial clock ticks away in the sky. Not only that, but vast quantities of latent energy are locked away in mass. That’s how coal fires, atomic bombs, and the sun work.