What is the 'Doomsday Clock' and what happens when it hits midnight?

The Doomsday Clock Is Now 85 Seconds to Midnight. Here’s What That Means

The Doomsday Clock is now at 90 seconds to midnight — the closest we have ever been to global catastrophe

Doomsday Clock - Bulletin of the Atomic Scientists

Nuclear Clock Breakthrough Could Expose Dark Matter and Speed Up the Internet

World War 3: Doomsday clock inches closer to midnight as nuclear war imminent between these countries; experts says threat level for US is...

7 Moments in the History of the Doomsday Clock | HISTORY

The Doomsday Clock, explained