News Physics

Atomic clocks take a step toward redefining the second

A new clock comparison is the most precise yet, accurate to within a quadrillionth of a percent

a ytterbium atomic clock in a NIST lab

Scientists compared three atomic clocks, including the ytterbium atomic clock shown, in a step toward a future redefinition of the second.

N. Phillips/NIST

By Emily Conover

- More than 2 years ago

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 of time, the second (SN: 5/20/19).