TLDR: Atomic clocks are extremely accurate clocks that measure time by monitoring the resonant frequency of atoms. They are used for precise timekeeping and navigation.
An atomic clock is a special kind of clock that measures time using atoms. Atoms have different energy levels, and when they transition between these levels, they emit or absorb electromagnetic radiation at a very specific frequency. This frequency is used to define a second, which is the unit of time in the International System of Units (SI).
The accuracy of atomic clocks is incredibly high, and they are used as the standard for timekeeping around the world. They are used in various industries, including telecommunications and science. Atomic clocks are powered by electricity and are able to maintain their accuracy over long periods of time.
One of the main applications of atomic clocks is in satellite navigation systems like GPS. The precise timekeeping capabilities of atomic clocks are essential for calculating accurate positions based on the speed of light. Even a small timing error of a billionth of a second can result in a significant positional error.
The most common type of atomic clock uses caesium atoms, which are cooled to very low temperatures. The primary standard for atomic clocks in the United States is the NIST-F2 caesium fountain clock, which has an uncertainty of 1 second in 300 million years.
The history of atomic clocks dates back to the 1950s, when the first practical atomic clock using caesium atoms was built in the United Kingdom. Since then, atomic clocks have been studied and developed by various research institutions and national laboratories around the world.
The definition of a second as the duration of a certain number of vibrations of a caesium atom was established in 1968 and has been the basis for timekeeping ever since. However, there are ongoing efforts to develop even more accurate atomic clocks based on optical clocks or other technologies.
In addition to traditional atomic clocks, there are also chip-scale atomic clocks that are much smaller and consume less power. These clocks have expanded the applications of atomic clocks to various portable and commercial devices.
Overall, atomic clocks are incredibly precise timekeeping devices that rely on the resonant frequency of atoms to measure time. They are used in various industries and applications, including satellite navigation and scientific research.