Cough - the rubidium clock or oscillator does have an intrinsic frequency, which is the rubidium hyperfine transition of 6 834 682 610.904 324 Hz, it's just that the frequency generated by the transition in question isn't used to DEFINE the second, so by definition, it must be secondary. Only a Caesium clock is a primary standard, as the second is DEFINED to be the time taken for 9,192,631,770 cycles of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom.[1].
Unless of course they changed the rules recently ... [1] <http://www.bipm.org/en/si/si_brochure/chapter2/2-1/second.html> Dave -----Original Message----- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Poul-Henning Kamp Sent: 23 February 2010 09:53 To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Rb Oscillator - rather fundamental question In message <4b83a33c.1010...@smiffytech.com>, Matthew Smith writes: >Simple and rather fundamental question: does the common or garden >rubidium oscillator constitute an atomic clock? Yes. It is classified as a "secondary" atomic clock, because it does not have an intrinsic physical frequency, like the cesium standards, but it is an atomic frequency, and it is an atomic clock (if you attach a display or a pair of hands :-) -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
