MYSTERIES OF TERRA FIRMA: The Age and Evolution of the Earth

The quest to determine the age of the earth has busied physicists, geologists and mathematicians for hundreds of years. Clever but ultimately arcane methods for divining the planet's birth date, including calculating the amount of salt in the ocean, yielded guesses ranging from 10 million up to billions of years. Powell, head of Los Angeles's Museum of Natural Science and former member of the National Sciences Board under Bush and Reagan, deftly balances rigorous scientific descriptions with the story's many lively, human elements. Until it became a data-driven science at the beginning of the 20th century, chance and personality played a large role in geology's evolution. Earlier estimates of the Earth's age were constrained by the Church and later by the dogma of 19th-century geologists like the eminent Lord Kelvin, who seemingly held the science back as much as he contributed to it. The discovery that certain isotopes emit radioactivity at a constant rate led to the science of radiometry and the first best guesses at Earth's age. The development of the paleomagnetic time scale as well as theories about "earth behavior" (continental drift, plate tectonics) further refined the answer. Powell conjures up brilliant and hard-working scientists with ease, and ably conveys the quixotic leaps that have led to current understanding—Alfred Wegener hypothesized a broken super continent when, looking at a world map, he noticed that the Atlantic's two opposite coastlines matched up. So how old is Earth? According to Powell, it's approximately 4.5 billion years old. (Nov. 6)

Forecast:This impressive debut book will draw solid sales from historians and general science readers.