Doomsday Clock
The Doomsday Clock is a symbol that represents the estimated likelihood of a human-made global catastrophe, in the opinion of the nonprofit organization Bulletin of the Atomic Scientists. Maintained since 1947, the Clock is a proxy mechanism for threats to humanity from unchecked scientific and technological advances: A hypothetical global catastrophe is represented by midnight on the Clock, with the Bulletin's opinion on how close the world is to "zero" represented by a certain number of minutes or seconds to midnight.