At the dawn of the nuclear age, scientists created the Doomsday Clock as a symbolic representation of how close humanity is to destroying the world. On Tuesday, nearly eight decades later, the clock ...

For many years, cesium atomic clocks have been reliably keeping time around the world. But the future belongs to even more accurate clocks: optical atomic clocks. In a few years' time, they could ...

Most clocks, from wristwatches to the systems that run GPS and the internet, work by tracking regular, repeating motions. To build a clock, you need something that ticks in a perfectly repeatable way.