America’s new top clock will gain or lose just 1 second over the next 300 million years. NIST-F2, built by the US National Institute of Standards and Technology in Boulder, Colorado, came online on 3 April.
Infrared laser beams aimed at a ball of caesium gascoax it into a fountain-like trajectory. As the atoms fall, they absorb and then re-emit bursts of radiation, at an unvarying frequency of 9 192 631 770 Hz. That frequency is the international definition of a second. So, the F2 doesn’t mark time – it defines what time is by establishing how long a second is, and it can be used to precisely calibrate clocks.
The new clock is three times as accurate as the old NIST-F1. And whereas the earlier model was kept at room temperature, NIST-F2 is chilled to minus 193°. This minimises background radiation, boosting accuracy.
Ultraprecise timekeeping underlies technologies such as GPS navigation, electric-grid stability, and baking soufflés.
Find out more about how the NIST-F2 atomic clock works in this video…
– Alex Hutchinson
