The Doomsday Clock is a symbolic representation of how close humanity is to a global catastrophe, with midnight signifying annihilation. The closer the clock is to midnight, the greater the perceived threat from nuclear weapons, climate change, and disruptive technologies. Conversely, the clock has been moved back when political conditions improved, such as in 1991 after the Strategic Arms Reduction Treaty, when it was set to 17 minutes to midnight.
Created in 1947 by the Bulletin of the Atomic Scientists, the clock has been reset more than 20 times based on world conditions.