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.

The Doomsday Clock has been used to examine the world’s vulnerability to global catastrophe for nearly a century.

The Bulletin of the Atomic Scientists shifted the hands of the symbolic clock to 89 seconds to midnight, citing the threat of climate change, nuclear war and the misuse of artificial intelligence.