'In 1967 this unit of time was defined as 9,192,631,770 cycles of radiation of a cesium-133 atom'
the second
WEIGHTS & MEASURES: In 1967 this unit of time was defined as 9,192,631,770 cycles of radiation of a cesium-133 atom
In 1967 this unit of time was defined as 9,192,631,770 cycles of radiation of a cesium-133 atom
In 1967 this unit of time was defined as 9,192,631,770 cycles of radiation of a cesium-133 atom
WEIGHTS & MEASURES
the second
WEIGHTS & MEASURES