A new atomic clock is one of the world’s best timekeepers, researchers say — and after years of development, the “fountain”-style clock is now in use helping keep official U.S. time. Known as NIST-F4, ...

While some of us can fall asleep anywhere from a noisy auditorium to a brightly lit train station, others are more fussy, requiring quiet and dark to nod off. [Craig Lindley] likes to minimize light ...

Time already behaves strangely in modern physics. It can stretch, slow, and split depending on speed and gravity. Now a new theoretical study pushes that weirdness into even stranger territory. It ...