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.

The Doomsday Clock is the closest it has ever been to the symbolic point of annihilation in the 74 years it has been in operation.

The Doomsday Clock refers to the amount of time humanity has before it effectively kills itself with emerging technologies.