How does an atomic clock work? How does it start telling extremely precise time?
In: Technology
Real atomic clocks use some gas of a specific element, like caesium or rubidium. The element has a natural resonance frequency, which means it interacts most strongly with microwaves of a specific frequency.
You stick the gas in a box and beam microwaves at it. You can then detect how strongly the gas interacts with the microwaves (e.g. by producing more microwaves or absorbing them, depending on the design). So you have a circuit generate the microwaves at an adjustable frequency, and then you have another circuit basically “tune” the first one until it finds the best frequency, much like you would manually tune a radio to a station until you get the best reception. After a while the whole thing slowly becomes very stable when the right frequency is found and narrowed down.
To count seconds, you have a third circuit just divide down the microwave signal. Since you know the frequency at which the gas should resonate, you just count up to that number and every time you reach it, a second has passed.
The store-bought clocks you find labeled “atomic clocks” are just normal clocks with a radio receiver that picks up time signals sent by a radio station that itself has a real atomic clock.
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