The Doomsday Clock now stands at 89 seconds to midnight, the closest to catastrophe in its nearly eight-decade history. Here's a look at how — and why — it's moved.

What is the Doomsday Clock? It's 2025 and scientists have reset the clock closer to midnight and global catastrophe. Here's what it all means.

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,