[154417] in North American Network Operators' Group
RE: F-ckin Leap Seconds, how do they work?
daemon@ATHENA.MIT.EDU (Tony Finch)
Tue Jul 3 17:36:24 2012
Date: Tue, 3 Jul 2012 22:35:13 +0100
From: Tony Finch <dot@dotat.at>
To: Peter Lothberg <roll@Stupi.SE>
In-Reply-To: <CMM.0.95.0.1341346704.roll@rutten.stupi.se>
Cc: "nanog@nanog.org" <nanog@nanog.org>
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
Peter Lothberg <roll@Stupi.SE> wrote:
>
> As the definition of a atomic second is 9192631770 complete
> oscillations of cesium 133 between enery level 3 and 4, "everyone" can
> make a second in their lab, that's TAI.
No, TAI isn't based on the SI second you realise in your lab. It's the SI
second realised on the geoid by a large fleet of clocks. If you are on
Mars then TAI isn't based on your SI second, because TAI doesn't tick at a
fixed rate relative to local proper time owing to the orbital differences
of the two planets.
> UT1-UTC is done by observations from radio astronomers VLBI telecopes
> and a comitee, you can't make one in your lab, and it's not real
> time.
You can make quite a good approximation to UT1 with a transit instrument
and knowledge of your position.
Tony.
--
f.anthony.n.finch <dot@dotat.at> http://dotat.at/
Forties, Cromarty, Forth, Tyne, Dogger: Southeasterly 4 or 5. Slight or
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