Despite antipathy from ''nasty, noisy negativists,'' this physicist/lecturer has been seriously investigating UFOs since the Roswell, New Mexico incident of an alleged U.S. government cover-up of extraterrestrial contact. After laying a scientific framework for examining the data and countering arguments against their extraterrestrial source, he makes a case for at least some UFOs being alien spacecraft. The book includes forewords by former astronaut Edgar Mitchell and UFO researcher Bruce Maccabee.