Atomic Clocks and the SI

Atomic Clocks and Time Measurement

• Caesium is the element used in atomic clocks to measure time.
• The basis for the International System of Units' definition of a second is the caesium frequency.
• The SI unit of time is the second.
• The numerical value of the caesium frequency used to define a second is 9,192,631,770 Hz.
• The phenomenon that serves as the basis for the International System of Units' definition of a second is the energy transition of caesium-133 atoms.
• The system of atomic clocks around the world is called International Atomic Time (TAI).
• The system of Coordinated Universal Time (UTC) is based on International Atomic Time (TAI).
• The role of atomic clocks is to provide a precise and consistent way of measuring time.