Bruce Van Allen schreef: > Some may have seen the news that debate has flared up regarding the > continued use of leap seconds. I don't know whether it will be > resolved soon, so it seemed best to simply acknowledge the issue, and > hope we remember to update the FAQ if something radically changes.
This was based on a slashdot story; nevertheless it was a serious proposal. There was a scientific meeting on the subject in Turin in May, summarized at http://www.mail-archive.com/[EMAIL PROTECTED]/msg00163.html (on the LEAPSECS mailing list!). The options that were mentioned were: - Abandoning leap seconds altogether. This would lead to an error of about an hour in the year 3000 (so the sun would rise and set one hour later then, than in 2003). - Introducing leap hours. The first leap hour would be introduced around 2600, when TAI-UTC is about 30 minutes. - Going back to the 60's, with smaller adjustments to UTC (perhaps by 0.1 seconds). - Keeping the leap seconds. Apparently, the fourth option was favoured by the majority present, and abandoning leap seconds would cost US tax payers half a billion US$. (It doesn't say if this is the total amount, or per tax payer.) > This FAQ entry gets longer every revision, but it seems important for > acceptance of DT that we have a fairly rigorous explanation. I doubt it. Not many people will be interested in the precise details. People who really need to know it (e.g. those to whom it would cost $100,000,000 dollar if the time is out by just one second) won't be convinced by a simple FAQ entry. (I wouldn't be, at those prices.) So I don't really know if the long entry you wrote should be included. But I don't mind if it is, either. You decide! My comments below are based on my web research of a few weeks ago. I could be wrong, but I would like to know where you got some of your info. > ## FAQ entry: ######## > > UTC is widely used in scientific and technical contexts, and is > increasingly accepted as the standard time scale for civic and > business uses. "increasingly accepted"? Is there any business that is half a minute of standard time? (Half an hour, yes. I commute by train.) Better: "UTC (Temps Universel Coordonne, Universal Coordinated Time) is the current standard time scale. Civil time (the time we all use in day-to-day life) is based on UTC, and generally differs exactly an integer number of hours from UTC, depending on your time zone." > Related time scales include: > - GMT (Greenwich Mean Time), in which each twenty-four hour day has > exactly 86,400 uniform seconds by international convention (the > "imperial clock"); AFAIK this is not true. Better: "GMT (Greenwich Mean Time), the civil time in London (and by extension, in the whole UK, and elsewhere) in winter. Since the introduction of UTC, GMT is equal to UTC." > TAI was originally synchronized with UT1 on 1958 January 1 (i.e., on > that date, UT1 - TAI = 0). To reconcile the divergence since then > between TAI and UT1, UTC is defined to differ from TAI by integer > atomic seconds and to differ from UT1 by less than .9 atomic seconds. > To maintain this relationship, leap seconds are introduced as needed > to the UTC time scale, under the supervision of the International > Earth Rotation and Reference Systems Service (<a > href="http://www.iers.org/iers";>IERS</a>). Perhaps these paragraphs could be rewritten a bit clearer: TAI was originally synchronized with UT1 on 1958 January 1 (i.e., on that date, TAI - UT1 = 0). Because of the slowing down of the rotation of the earth, the TAI - UT1 difference has been growing since 1958. In May 2003, TAI - UT1 was measured to be 32.4 seconds. UTC follows UT1 as accurately as possible, while keeping the difference with TAI an integral number of seconds. At the time of writing, TAI - UTC is 32 seconds. To maintain the relationship between UT1 and UTC, a leap second will be introduced as soon as TAI - UT1 reaches 32.9 seconds, as determined by the International Earth Rotation and Reference Systems Service (<a href="http://www.iers.org/iers";>IERS</a>). Eugene
