On 2 February 2011 18:13, Warner Losh <[email protected]> wrote: >> - an SI-based-minute is formed from exactly 60 SI-seconds >> - an SI-based-hour is formed from exactly 60 SI-based-minutes and thus >> exactly 3600 SI-seconds >> - an SI-based-day is formed from exactly 24 SI-based-hours and thus >> exactly 86400 SI-seconds >> > These are true only most of the time. On leap second day, they are all > false and off by 1, typically one low. It all depends on the timescale that > you use, and thus there can't be a universal definition here.
You're reading more into the statement than is intended by trying to interpret them as a time-scale or clock. I'm defining a unit of SI-based-minute that is a multiple of 60 of the unit SI-second. No more no less. >> Solar >> - a solar-day is a measured period of time >> - the length of a solar day in in SI-seconds varies over time >> - the length of a solar day in in SI-seconds is on average increasing with >> time >> - a solar day is not a fixed number of SI-seconds >> - a solar-hour is the period of 1/24th of a single measured solar-day >> - a solar-minute is the period of 1/60th of a solar-hour and thus >> 1/1440th of a single measured solar-day >> - a solar-second is the period of 1/60th of a solar-minute and thus >> 1/86400th of a single measured solar-day > > Except that the last bits are wrong here too. It isn't the measured solar > day, except for UT, but the average of the measured day smoothed in > different ways for UT1 and UT2. > > Also, implicit in this definition is the astronomical term solar-day, so > your definition is circular. A solar day is the amount of time it takes the > earth to rotate until the sun is in the same apparent position in the sky, > as opposed to a sidereal day, which is 360 degrees of rotation. So why not tweak these, or try to build consensus around a different set of statements? >> UTC-2011 >> - the UTC-2011 time-scale is known as UTC in the year 2011 >> - the UTC-2011 time-scale is a continuous count of SI-seconds >> - the UTC-2011 time-scale defines UTC-2011-days >> - a UTC-2011-day is either 86400 SI-seconds or 86401 SI-seconds long >> - the additional SI-second in a UTC-2011-day is a leap-second >> - the presence or absence of a leap-second is determined up to 6 >> months in advance > > yes. This time Bulletin came out this morning, giving only 5 months of > notice of no leap second. > > I'm also not sure that this notation is the best. We're really using > UTC-1972 right now, if we follow the convention of using the year of the > last change. We'd also be on TAI-2008 based on the last time the averaging > algorithm of TAI was changed. We should use UTC-1972 as a terminology if has broader agreement. Stephen _______________________________________________ LEAPSECS mailing list [email protected] http://six.pairlist.net/mailman/listinfo/leapsecs
