Atoomstandaarden

Atoomstandaarden, also known as atomic standards or atomic time scales, are a type of time scale that is based on the resonant frequencies of atoms. Unlike astronomical time scales, which are based on the Earth's rotation, atomic time scales are highly stable and accurate. The primary atomic time scale in use today is International Atomic Time (TAI).

TAI is calculated by the Bureau International des Poids et Mesures (BIPM) from the data of hundreds of atomic clocks located in laboratories around the world. These clocks are typically cesium atomic clocks, which utilize the frequency of the transition between two specific energy levels in cesium atoms. This frequency is extremely stable and has been found to be a reliable indicator of the passage of time.

The definition of the second, the base unit of time in the International System of Units (SI), is based on the cesium atom. Specifically, one second is defined as the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the cesium 133 atom.

Atomic time scales are crucial for many scientific and technological applications, including satellite navigation systems like GPS, telecommunications, and scientific research. They provide a consistent and precise measure of time that is independent of celestial mechanics. While TAI is a continuous and uniform time scale, it does not account for the gradual slowing of the Earth's rotation. Therefore, Coordinated Universal Time (UTC), which is the basis for civil time worldwide, is derived from TAI but is periodically adjusted with leap seconds to keep it synchronized with astronomical time.