Peter Lothberg <r...@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 <d...@dotat.at> http://dotat.at/ Forties, Cromarty, Forth, Tyne, Dogger: Southeasterly 4 or 5. Slight or moderate. Rain or drizzle, fog banks. Moderate or poor, occasionally very poor.
