Physicists are quietly rewriting one of the most basic units in science, using a new generation of optical clocks that can keep time so precisely they barely lose a beat over the age of the universe.

The world’s most accurate clock now belongs to researchers at the National Institute of Standards and Technology (NIST). Its new optical atomic clock, built around a single trapped aluminum ion, can ...

Researchers at the U.S. National Institute of Standards & Technology (NIST) say they have created the most accurate atomic clock to date — one that can measure time down to the 19th decimal place.