Ever since the first sighting 50 years ago, UFOs have gripped the public imagination. This definitive work highlights the most significant cases and developments -- from the first reports of unidentified flying objects to alien sightings, claims of abductions, religious cults, crash retrievals, and the emergence of witness support groups. Alongside these developments the Spencers discuss the cultural developments and social contexts of the past half-century, such as the release of the film 2001, the first man on the moon and the science fiction boom of the 1950s and 1990s.