[time-nuts] One Kg Quartz Resonator

[Jim Lux]

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.