Placebo cures. Global warming. Extraterrestrial life. Psychokinesis. In a time when scientific claims can sound as strange as science fiction--and can have a profound effect on individual life or public policy--assessing the merits of a far-out, supposedly scientific idea can be as difficult as it is urgent. Into the breach between helpless gullibility and unyielding skepticism steps physicist Robert Ehrlich, with an indispensable guide to making sense of scientific claims. A series of case studies of some of the most controversial (and for the judging public, deeply vexing) topics in the natural and social sciences, Ehrlich's book serves as a primer for evaluating the evidence for the sort of strange-sounding ideas that can shape our lives. A much-anticipated follow-up to his popular Nine Crazy Ideas in Science, this book takes up issues close to readers' everyday reality--issues such as global warming, the dangers of cholesterol, and the effectiveness of placebos--as well as questions that resonate through (and beyond) civic life: Is intelligent design a scientific alternative to evolution? Is homosexuality primarily innate? Are people getting smarter or dumber? In each case, Ehrlich shows readers how to use the tools of science to judge the accuracy of strange ideas and the trustworthiness of ubiquitous experts. As entertaining as it is instructive, his book will make the work of living wisely a bit easier and more reliable for scientists and nonscientists alike.