Aliens. Monsters. Robots. Spaceships. Superhuman powers. Time machines. Yup, we're talking science fiction. But just why are these ideas so perennially popular?

As scholars and creators of the genre told, many of sci-fi's common scenarios, which may seem to be escapist fantasy, serve to delve into complex themes that beholden-to-reality fiction and nonfiction cannot explore so readily.

By engaging in what-ifs that are either far-out and close to home, science fiction stories can challenge assumptions that otherwise would go unexamined. Sci-fi shows us through film, television and literature where our society might have ended up, for better and for worse, had things been different.