When most people read about dating an ancient artifact, we think of carbon-14 dating. But as earth scientist Macdougall (Frozen Earth
) tells readers, carbon dating works only if the object contains carbon, and then it can't be more than about 50,000 years old. Many other elements are radioactive, allowing, for example, for a potassium-argon dating system of volcanic and Precambrian rocks, and other applications in studying archeology and human evolution. Macdougall says that scientists have used these various radiometric dating systems for research as far-flung as dating the age of the solar system, figuring out when humans immigrated to the North America and when the Neanderthals died out, determining that a huge tsunami was created by a massive earthquake off the Northwest Pacific Coast in 1700 and nailing down the age of the Shroud of Turin (it dates to the Middle Ages, though controversy persists). Science buffs from all fields along with general readers will find this a helpful handbook on how we are now able to travel to the distant past. B&w photos, line drawings, map. (June)
