Douglas McIntyre explains the history and significance of the Doomsday Clock, which was recently set to 89 seconds to midnight—the closest ever. Originally created by atomic scientists, the clock now reflects growing concerns about climate change,

The Doomsday Clock, a symbolic measure of humanity's proximity to catastrophic destruction, has been set at 89 seconds to midnight—the closest it has ever been, symbolizing humanity's shortest margin from potential catastrophe since the clock's creation.