Wirebook › Glossary › Atomic clock
What is an atomic clock?
In one sentence: An extremely precise clock that keeps time by counting the vibrations of atoms. GPS satellites carry several.
A little more
Ordinary clocks count the swings of a pendulum or the wobbles of a tiny quartz crystal, which drift a little with heat and age. An atomic clock counts something that never changes: the natural vibration of atoms such as caesium, which ticks 9,192,631,770 times a second. That number is literally how a second is defined.
The best atomic clocks would lose less than a second in millions of years. GPS satellites carry several each, because their whole job is telling the exact time.
It's a bit like… A metronome that every musician in the world agrees on, and that never speeds up or slows down.