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Tom Peters (talk | contribs) →Proposed change: TP: a few comments |
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Since the inception of UTC, there have been 22 leap second adjustments (see list), all of them "positive", i.e., adding an extra second to UTC as opposed to skipping one. Leap seconds are announced six months in advance, and occur simultaneously around the world during the last minute of June or December, at 23:59:60 UTC. In recent decades, the Earth has been in a period of acceleration, so fewer leap seconds have been needed. The one announced for [[2005-12-31]] will be the first in seven years, bringing the difference between TAI and UTC to 33 seconds. That is, UTC-TAI = -33 s as of [[2006-01-01]].
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: My comments:
* somewhat too extensive: it is a (brief) account of the history of the second, which should be or already is described in other articles: use links.
* tidal deceleration contributes +2.4 ms/cy to the l.o.d.; the number +1.7 is the observed average over the past 25 centuries. The difference is probably mainly due to so-called glacial rebound, which is another long-term process since the end of the ice age; see the article on [[Delta-T]].
* Jeepien, on your previous comment: I begin to find the discussion meaningless. The reason that we need leap seconds is that the rotation of the Earth is irregular, but nonetheless for civil life we want to keep in sync with the solar day. There are a zillion mechanisms that influence the rotation rate on all time scales, but the tidal deceleration is the main and most persistent one. I don't understand why you and some others are so opposed to even mentioning it. In any case I object to givi ng so much attention to recent short-term irregularities.
* I did not add the piece about creationists misinterpreting the reason for leap seconds, but apparently this is an issue and if it should be addressed, this is the proper place; possibly under its own sub-heading. I say we keep it.
-- [[User:Tom Peters|Tom Peters]] 20050812T10:15 UT
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