To use all functions of this page, please activate cookies in your browser.
With an accout for my.chemeurope.com you can always see everything at a glance – and you can configure your own website and individual newsletter.
- My watch list
- My saved searches
- My saved topics
- My newsletter
Additional recommended knowledge
By the definition of the SI second, the transition between the two hyperfine ground states corresponds, in the absence of external influences (e.g., the Earth's magnetic field), to radiation with a frequency of exactly 9 192 631 770 Hz.
The value 9 192 631 770 Hz was chosen so that the cesium second equalled, to the limit of human measuring ability in 1960 when it was adopted, the existing standard ephemeris second based on the Earth's orbit around the Sun. Because no other measurement involving time had been as precise, the effect of the change was less than the experimental uncertainty of all existing measurements.
Source: from Federal Standard 1037C and from MIL-STD-188
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Caesium_standard". A list of authors is available in Wikipedia.|