The smallest conceivable length of time might be no larger than a millionth of a billionth of a billionth of a billionth of a second. That's according to a new theory describing the implications of ...

The new kilogram has finally arrived. Updates to scientists’ system of measurement went into force May 20, redefining the kilogram and several other units in the metric system. The revamp does away ...

Scientists have measured the shortest unit of time ever: the time it takes a light particle to cross a hydrogen molecule. That time, for the record, is 247 zeptoseconds. A zeptosecond is a trillionth ...

A new measurement moves scientists closer to revamping how we keep time. After scientists redefined the unit of mass, the kilogram, in 2019, they set their sights on overhauling the fundamental unit ...