Although this is somewhat off-subject I will take the liberty of commenting on this once:
The physical phenomenon which is used as a frequency reference in the paper in Science is the recoil splitting (of the relevant Caesium transition). This is well-known and has been studied experimentally for some time. It is important for example as a method for measuring h/m; a reference cited in the paper reports the current best such result and gives information on previous measurements. The frequency reference method described in the paper in Science is irrelevant for accurate frequency and time measurement, since the accessible uncertainty is many orders of magnitude worse than that of primary frequency standards. For many years and independently of this paper, the international metrology community has been considering the possibility of redefining the kilogram by assigning a conventional value to h. This would indeed create a link between the kg and the second, analogous to that which already exists between the metre and the second due to the attribution of a conventional value to c. Best regards Philip On 12 févr. 2013, at 18:23, Yaakov Stein wrote: > Hi all, > > We all know that in relativity theory E = m c^2 > and that in quantum mechanics E = h f (where f is the wave frequency), > so that a mass m corresponds to a frequency f = m c^2 / h (called its Compton > frequency). > > However, until now it has not been practical to directly relate frequency and > mass, > because c^2/h is just too big. > > Well, in a new article http://www.sciencemag.org/content/339/6119/554.abstract > researchers from Berkeley have been able to build a clock with an accuracy of > E-9 > that directly connects mass and frequency. > Eventually this may lead to linking the definitions of the second and the > kilogram. > > Y(J)S > > _______________________________________________ > TICTOC mailing list > [email protected] > https://www.ietf.org/mailman/listinfo/tictoc -- SYRTE/LNE-SYRTE Observatoire de Paris - CNRS - UPMC - LNE 61 ave de l'Observatoire, 75014 Paris, France tel +33 1 40 51 22 46 fax +33 1 43 25 55 42 mail [email protected]
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