[LEAPSECS] the big artillery

michael.deckers michael.deckers at yahoo.com
Thu Nov 6 06:40:17 EST 2014

   On 2014-11-05 15:30, Warner Losh wrote on the
   determination of TAI - UT1:

> Now, back to the SI second vs the UT1 second. The UT1 second is 1E-8 or 1E-9 different
> from the SI second. Unless they are computing the results to 7 or more digits, the answers
> will be identical, no matter which definition of second you use.

   I don't understand. Measuring (mean solar day)/(1 d) is equivalent to
   measuring d(TAI - UT1)/d(UT1); if you assume the first quantity is 1,
   then the second becomes 0. Looking at a recent Bulletin B, the uncertainty
   for measurements of the rate d(UT1)/d(TAI) is of the order 1₁₀-9 (the IERS
   give 13 digits!), and typical uncertainty for LOD is around 10 µs/d.
   The IERS certainly won't fudge on their units.

   Michael Deckers.

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