Standards
How does an atomic clock work?
Atomic clocks turn an invariant atomic transition into the world’s most stable tick.
Every clock needs an oscillator
A pendulum clock counts swings and a quartz clock counts crystal vibrations. An atomic clock instead tunes electromagnetic radiation to the natural resonant frequency of atoms, then uses feedback electronics to keep that frequency locked.
The cesium definition of a second
Since 1967, the SI second has been defined using exactly 9,192,631,770 periods of radiation associated with a transition in the ground state of the cesium-133 atom. The atom is not a tiny clock face; it is a reproducible frequency reference.
Why atomic time reaches your phone
National laboratories compare ensembles of atomic clocks, contributing to international time scales. Navigation systems, telecommunications networks and internet time services distribute that timing so ordinary devices can remain aligned.