Book excerpt: Is the world warming due to the Greenhouse Effect? Can nuclear weapon arsenals be relied upon without periodic testing? Is the world running out of oil? What action should be taken against an outbreak of foot-and-mouth or BSE? Why can't scientists provide certain answers to these and many other questions? The uncertainty of science is puzzling. It arises when scientists have more than one answer to a problem or disagree amongst themselves. In this engaging book, Henry Pollack guides the reader through the maze of contradiction and uncertainty, acquainting them with the ways that uncertainty arises in science, how scientists accommodate and make use of uncertainty, and how in the face of uncertainty they reach their conclusions. Taking examples from recent science headlines and every day life, Uncertain Science ... Uncertain World enables the reader to evaluate uncertainty from their own perspectives, and find out more about how science actually works.