Why cesium?

Asked by lilikoi (10105

) 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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6 Answers

Good question. A short bit of research tells me that the resonant vibration frequency of a particular isotope of Cesium is known very precisely. The best cesium atomic clocks are accurate to 1 second in 17 million years.

Ivan (13479

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Makes perfect sense – Thanks!

lilikoi (10105

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Why not cesium?

AstroChuck (37609

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Here’s a link that explains it; Cesium Great question. I learn more from this site than I ever would have imagined.

Trillian (21148

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I am so gonna get swallowed up very quickly by the sheer brilliance of you guys and your science… but I am lurking nevertheless… fascinating subject!

nebule (16452

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The first attempt at an atomic clock was to use the s-p transition of the outer electrons in the beer atom, but that wavelength proved to be highly inconsistent… not so much in its frequency, but it actually staggers.

Grisson (4634

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