The SI unit of time is the second, represented by the symbol s.
The second is a base unit in the International System of Units (SI), meaning it's defined independently and not derived from other units. Its current definition is based on the frequency of radiation emitted by cesium-133 atoms. More specifically, the 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.
While other units of time exist, such as minutes, hours, days, and years, they are not part of the SI system and are defined in terms of the second. For example:
- 1 minute = 60 seconds
- 1 hour = 60 minutes = 3600 seconds
- 1 day = 24 hours = 86,400 seconds
The precise definition of the second is crucial for accurate scientific measurements and technological applications worldwide, including atomic clocks, telecommunications, and global navigation systems like GPS.
