They are invincible warriors of steel, silky-skinned enticers, stealers of jobs and lovable goofball sidekicks. Legions of robots and androids star in the dream factories of Hollywood and leer on pulp magazine covers, instantly recognizable icons of American popular culture. For two centuries, we have been told tales of encounters with creatures stronger, faster and smarter than ourselves, making us wonder who would win in a battle between...