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    Question ID:   1755         Current Version: 1
Question: How is the second defined?
Category: Science > Physics
Keywords: ratiation, atom, second, time, define, definition
Type: how
Rating:(1 ratings)    Views: 1742    Discussions: 0   In Watch Lists: 1  

 
    Answer:
The international definition of a second is "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 atom." This definition was agreed upon in 1967. Atomic clocks based on the cesium atom then became the primary means for accurate timekeeping.
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