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Why cesium?
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March 10th, 2010
From a Tipler book:
“The unit of time, the second (s), was originally defined in terms of the rotation of the earth and was equal to (1/60)(1/60)(1./24) of the mean solar day. The second is now defined in terms of a characteristic frequency associated with the cesium atom…The second is defined so that the frequency of light from a certain transition in cesium is 9,192,631,770 cycles per second….”
Why cesium? And why that particular transition?
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