[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
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