Atomic Time (TAI)

Atomic time, officially known as International Atomic Time (TAI, from the French "Temps Atomique International"), is a high-precision time standard based on the resonance frequency of atoms. It provides a continuous, stable time scale that is not affected by irregularities in Earth's rotation.

TAI is determined by a worldwide network of atomic clocks that measure time based on the electromagnetic radiation emitted by cesium-133 atoms during a specific energy level transition. The second in TAI is defined as the duration of 9,192,631,770 cycles of this radiation, which is the official SI definition of the second.

Unlike UTC (Coordinated Universal Time), TAI does not include leap seconds and therefore runs continuously without adjustments. As a result, as of 2023, TAI is ahead of UTC by 37 seconds due to the leap seconds that have been added to UTC since 1972.

The relationship between TAI and UTC is: UTC = TAI - (number of leap seconds)

Atomic time is crucial for applications requiring extremely precise timekeeping, such as global navigation satellite systems (like GPS), scientific research, and telecommunications. However, for everyday civil timekeeping, UTC is used instead because it stays approximately synchronized with the Earth's rotation.