Tracking time is one of those things that seems easy, until you really start to get into the details of what time actually is. We define a second as 9,192,631,770 oscillations of a cesium atom.

A millimeter might not seem like much. But even a distance that small can alter the flow of time. “This is fantastic,” says theoretical physicist Marianna Safronova of the University of Delaware in ...

Physicists from JILA — a CU Boulder and National Institute of Standards and Technology institute — were able to measure an effect called time dilation at the smallest scale ever, which they say could ...