The Doomsday Clock

The Doomsday Clock was conceived by the board of directors of the Bulletin of the Atomic Scientists at the University of Chicago and made its first appearance in 1947. The clock conveys in a very graphic way the number of minutes left before humanity destroys the world with nuclear weapons. Since 2007 the clock has been set to 5 minutes before midnight. The Wikipedia entry on the Doomsday Clock contains many more fascinating details, including how the clock has been incorporated into popular culture.