What is the 'Doomsday Clock,' and what it mean when it gets to midnight

Earth is closer than it's ever been to destruction as Russia, China, the U.S. and other countries become 'increasingly aggressive, adversarial, and nationalistic,' The Bulletin of The Atomic Scientists said as it advanced its 'Doomsday Clock' to 85 seconds till midnight. Subscribe to The Globe and Mail's Morning Update to get stories directly in your inbox: https://www.theglobeandmail.com/newsletters/subscribe-morning-update/