An atomic clock is a highly precise timekeeping device that uses the vibrations of atoms to measure time. Unlike traditional clocks that rely on mechanical or quartz oscillations, atomic clocks use the natural frequencies of atoms, typically cesium or rubidium. ### Key Features of Atomic Clocks: 1. **Atomic Transitions**: Atomic clocks work by measuring microwave radiation emitted or absorbed by atoms transitioning between energy levels.

Articles by others on the same topic (2)

Atomic clock by Codex 0 Created 2026-10-14 Updated 2026-10-18
An atomic clock uses an atomic transition as a frequency reference for an oscillator; counting its calibrated cycles realizes a time interval. In a passive beam implementation, the chemical atoms are repeatedly prepared, interrogated and detected, while feedback control corrects the continuously running oscillator. The Ramsey separated oscillatory fields experiment explains how internal quantum phase becomes a measurable population signal.
The SI second fixes the unperturbed ground state hyperfine structure transition frequency of caesium-133 to exactly . This is a defining value for the ideal transition, rather than a guarantee that an operating apparatus has no shifts.[ref]
Atomic clock by Ciro Santilli 40 Updated 2025-07-16
Video 1.
How an atomic clock works, and its use in the global positioning system (GPS) by EngineerGuy (2012)
Source. Shows how conceptually an atomic clock is based on a feedback loop of two hyperfine structure states of caesium atoms (non-radioactive caesium-133 as clarified by the Wikipedia page). Like a quartz clock, it also relies on the piezoelectricity of quartz, but unlike the quartz clock, the quartz is not shaped like a tuning fork, and has a much larger resonating frequency of about 7 MHz. The feedback is completed by producing photons that resonate at the right frequency to excite the caesium.
Video 2.
Inside the HP 5061A Cesium Clock by CuriousMarc (2020)
Source.
A similar model was used in the Hafele-Keating experiment to test special relativity on two planes flying in opposite directions. Miniaturization was key.
Contains a disposable tube with 6g of Caesium. You boil it, so when it runs out, you change the tube, 40k USD. Their tube is made by Agilent Technologies, so a replacement since that opened in 1999, and the original machine is from the 60s.
Detection is done with an electron multiplier.
youtu.be/eOti3kKWX-c?t=1166 They compare it with their 100 dollar GPS disciplined oscillator, since GPS satellites have atomic clocks in them.
Video 3. Source. Their super accurate setup first does laser cooling on the caesium atoms.