Hi I think a better analogy would be:
There don't have to be exactly X atoms in the Avogadro ball for it to be a standard. You simply have to know how many relative to X in order to correct for your gizmo. The gotcha obviously is you need the count of each isotope. The same sort of issue applies to a cesium. You actually measure gravity (and several other things) and correct for them. If there was no way to measure your local gravity (or magnetic field), you would have a lot of trouble using Cs as a primary standard. That said, the currently accepted primary mass standard is simply an arbitrary lump of metal. It does not connect to anything other than it's self. That's not a good thing at all. Bob -----Original Message----- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Mike S Sent: Thursday, January 24, 2013 11:50 AM To: time-nuts@febo.com Subject: Re: [time-nuts] One Kg Quartz Resonator On 1/24/2013 10:38 AM, Jim Lux wrote: > On 1/24/13 7:24 AM, Mike S wrote: >> On 1/23/2013 3:34 AM, Magnus Danielson wrote: >>> On 01/23/2013 02:32 AM, Mike S wrote: >>>> Can you have a Cs under zero acceleration and at zero temperature, the >>>> only conditions for which the second is defined? Since most metric >>>> units >>>> are derived from the definition of the second, are any "primary >>>> standards," in your opinion? >>> >>> Isn't it defined for zero sea-level, that is standard acceleration? >> >> "At its 1997 meeting the CIPM affirmed that: >> This definition refers to a caesium atom at rest at a temperature of 0 >> K." - http://www.bipm.org/en/si/si_brochure/chapter2/2-1/second.html >> >> Sea-level would be 1 g of acceleration, would it not? >> > which sea? OK, "roughly 1 g," but that's missing the point. Which is, a real-world device that realizes the definition of the second is (currently?) impossible. That TAI is a weighted average of many "standards" I think supports that - real world devices must be compensated to be close, but still imperfect. My question was in response to a claim that if "the number and type of atoms in such a standard" (proposed 1 kg silicon sphere) couldn't be counted, "its not a primary standard." The same logic could be applied to the second, and all derived units. _______________________________________________ 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.