WHY THINGS BREAK: Understanding the World by the Way It Comes Apart

Why can you bend a piece of taffy into all kinds of shapes while a peppermint stick breaks if you push on the middle of it? Why does adding carbon to iron make the resulting metal, steel, stronger, whereas adding sulfur brittles it, making it more liable to break? Eberhart, a professor at the Colorado School of Mines, explains the chemistry of metals and other materials to answer these and similar questions. Scientists still have much to learn about how planes of atoms slide over one another when a substance bends, or why impurities can toughen an alloy. In the past, scientists and manufacturers designed new products on a wing and a prayer, hoping that they wouldn't break. The Titanic went down in large part, Eberhart explains, because the iron used in the ship's hull had been made brittle by sulfur, allowing the iceberg to rip through it easily. Today metallurgists have to be able to develop materials with the exact properties needed to avoid another such disaster—think of the Challenger or of an airplane breaking up in flight because a tiny crack was exacerbated by increasing and decreasing air pressure. Hydrogen-powered cars are still in the future because hydrogen embrittles most substances it comes into contact with, so new and tougher engines need to be designed to withstand it. Though Eberhard uses many examples from everyday life to illustrate his points, his discussion gets more specialized as the book progresses, making it best for science buffs. (Oct.)