DRU SEFTON, Newhouse News Service, reports:
Let us now take 9,192,631,770 cycles of radiation corresponding to the transition between two hyperfine levels of the ground state of cesium-133 to pay tribute to the atomic clock.
That would be one second.
Fifty years ago this October, the atomic clock first became available commercially. It and its descendants use that cesium frequency to keep time, accurately measuring to one-billionth of a second.