Keeping perfect time is far trickier than it sounds. The world’s best clocks that ...

Since 1947 -- after the end of World War II and at the beginning of the Cold War -- the Science and Security Board of the Bulletin of Atomic Scientists have kept what they call a "Doomsday Clock." ...

Optical lattice clocks are emerging timekeeping devices based on tens of thousands of ultracold atoms trapped in an optical lattice (i.e., a grid of laser light). By oscillating between two distinct ...