[time-nuts] One Kg Quartz Resonator
Poul-Henning Kamp
phk at phk.freebsd.dk
Tue Jan 22 21:07:52 UTC 2013
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In message <50FEF6DB.4020404 at xtra.co.nz>, Bruce Griffiths writes:
>But can the number and type of atoms in such a standard be counted?
>Otherwise its not a primary standard.
Yes.
If you arrange them into a perfect sphere, you can measure the
crystal-grid spacing very precisely with x-rays, and the diameter
even more precisely with lasers.
Interestingly, this experiment may also become the first time we
ever needed to know PI better than 355/113 outside abstract
mathematics.
My friends in metrology all bet on the watt-balance supplying the
new mass definition, rather than the quartz-ball, simply because they
are so much easier to construct. The isotope-separation is really
a killer.
--
Poul-Henning Kamp | UNIX since Zilog Zeus 3.20
phk at 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.
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