On Thu, 3 Feb 2011, Stephen Colebourne wrote: > > * TAI-2008 does not definitively imply a definition for minutes, hours and > days
Yes it does, since the usual way of writing a TAI instant is in ISO 8601 format. > * definition: solar-time - time kept or measured by the Sun time measured by the rotation of the earth relative to the sun. > * the accurate measurement of solar-time is complex and typically > achieved via cooperation How accurate? Does a precision sundial not count? What about a clock regulated by a transit instrument? Since you say this for every form of time it sounds like a redundant platitude. > * the length of a mean-solar-day in in SI-seconds varies over time > * the length of a mean-solar-day in in SI-seconds is on average > increasing with time > * the length of a mean-solar-day is not a fixed number of SI-seconds This last definition is redundant. (There's a similar redundancy for UT1.) > * definition: UT - a time scale based on the rotation of the Earth > (defined in detail elsewhere) based on the rotation of the Greenwich meridian relative to the Sun. (The specific meridian is what distinguishes it from solar time in general.) > * definition: UT1 - a smoothed variant of UT (defined in detail elsewhere) Mean solar time for the Greenwich meridian. > * the UTC-1972 time-scale is a continuous count of SI-seconds It uses TAI seconds. The number of seconds in a UTC interval cannot be deduced from the standard representation of the start and end UTC instants without the assistance of an auxiliary table of leap seconds. > - a humanity-day is interpreted in line with the rising and setting of the Sun Except in tricky situations like transcontinental flights and living near the poles. > * a UT1-day is the most commonly recognised form of a humanity-day Definitely not, because of DST. Tony. -- f.anthony.n.finch <d...@dotat.at> http://dotat.at/ HUMBER THAMES DOVER WIGHT PORTLAND: NORTH BACKING WEST OR NORTHWEST, 5 TO 7, DECREASING 4 OR 5, OCCASIONALLY 6 LATER IN HUMBER AND THAMES. MODERATE OR ROUGH. RAIN THEN FAIR. GOOD. _______________________________________________ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
