Paul J. Nahin is emeritus professor of electrical engineering at the University of New Hampshire. He is the author of many popular math books, including most recently In Pursuit of Zeta-3: The World's Most Mysterious Unsolved Math Problem; Hot Molecules, Cold Electrons: From the Mathematics of Heat to the Development of the Trans-Atlantic Telegraph Cable; and How to Fall Slower Than Gravity: And Other Everyday (and Not So Everyday) Uses of Mathematics and Physical Reasoning (all Princeton).