Definition

Noun: A highly precise timekeeping device that uses the consistent frequency of microwave radiation emitted or absorbed by caesium atoms during electron transitions between two specific hyperfine energy levels of their ground state. This frequency serves as the fundamental reference for defining the international standard second.

Examples of Usage

• The caesium clock is the primary standard for Coordinated Universal Time (UTC).
• Modern global navigation systems rely on the extreme accuracy of the caesium clock.
• Scientists calibrated the new telescope using a signal from a caesium clock.

Advanced Usage

• Primary frequency standard: A caesium clock that operates as the defining standard for the second, as opposed to commercial or secondary clocks that are calibrated to it.
• Fountain clock: A specific, advanced type of caesium clock where atoms are tossed vertically (like a fountain) to increase observation time and thus precision.

Variants and Related Words

• Atomic clock: The broader category of timekeeping devices that use atomic transitions. A caesium clock is the most common type of primary atomic clock.
• Cesium clock: An alternative spelling, primarily used in American English.
• Frequency standard: A device that generates a very precise and stable frequency; a caesium clock is a type of primary frequency standard.

Synonyms

• Atomic frequency standard
• Cesium atomic clock

Related Phrases

• To be based on a caesium clock: To use a caesium clock as its fundamental timing reference.
  • The national time service is based on a caesium clock.
• Caesium clock accuracy: Refers to the phenomenal precision of these devices, typically losing or gaining less than one second in millions of years.
  • The experiment required caesium clock accuracy.

Noun

1. an atomic clock based on the energy difference between two states of the caesium nucleus in a magnetic field