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.
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