More than half of American adults and more than seventy-five percent of young Americans believe in intelligent extraterrestrial life. This level of belief rivals that of belief in God. American Cosmic examines the mechanisms at work behind the thriving belief system in extraterrestrial life, a system that is changing and even supplanting traditional religions. Over the course of a six-year ethnographic study, D. W. Pasulka interviewed successful and influential scientists, professionals, and Silicon Valley entrepreneurs who believe in extraterrestrial intelligence, thereby disproving the common misconception that only fringe members of society believe in UFOs. She argues that widespread belief in aliens is due to a number of factors including their ubiquity in modern media like The X-Files, which can influence memory, and the believability lent to that media by the search for planets that might support life. American Cosmic explores the intriguing question of how people interpret unexplainable experiences, and argues that the media is replacing religion as a cultural authority that offers believers answers about non-human intelligent life.