Caesium standard

A caesium standard is a special clock that uses a tiny amount of a material called caesium (which is a kind of metal) to help measure time very accurately. The clock works by measuring how many times a certain kind of vibration or movement happens in a second. This vibration is caused by the electrons of the caesium atoms moving back and forth very quickly. By measuring this movement very carefully, the clock can keep very accurate time. It's kind of like how you can count how many times your heart beats in a minute to see how fast it's going. The caesium standard clock is used in many important applications, including telecommunications, GPS systems, and scientific experiments where precise timing is crucial.