Science fiction is filled with explorations of alien life. What can aliens teach us about what it means to be human? Aliens from other worlds have been a staple of science fiction since H.G. Wells first popularized the idea of Martians in The War of the Worlds. Whether they truly exist is an open question, but there's no denying the fact that aliens have been objects of both fascination and fear ever since - from Close Encounters to Independence Day. Science fiction has used aliens as metaphors to explore powerful ideas about communication, colonization, politics, power - and our treatment of each other.