Hi Part of the process is to actually measure the local "g" and correct for it. NIST is nowhere near the sea...
Bob -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Jim Lux Sent: Thursday, January 24, 2013 10:38 AM To: [email protected] Subject: Re: [time-nuts] One Kg Quartz Resonator 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? and even if you pick a definition for sea level, g is nowhere near constant in either magnitude or direction at that "surface". (well, there is a "g points down normal to the surface" definition of geoid) ANd then, there are thing like solid earth tides (so your sea level lab is moving up and down a bit), and the local g is changing because of the sun and moon. (moon is about 10 microg, sun half that, I think) Such are the problems faced by people trying to get that 9+ digits of accuracy. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
