USA TODAY asked Alexandra Bell, the president and CEO of the Bulletin of the Atomic Scientists, a few questions about the Doomsday Clock.

Humanity is closer than ever to catastrophe, according to the atomic scientists behind the Doomsday Clock. The ominous metaphor ticked one second closer to midnight this week. The clock now stands just 89 seconds away — its first move in two years and ...

This particular clock is technically an ion clock, which is different from the more common atomic clocks that are based on measuring the resonant frequencies of a single cesium atom to regulate time keeping. Instead, the ion clock is a type of atomic clock that does its job by using a pair of quantum-linked ions for greater accuracy and stability.