Re: GMT - UTC in Australia
Rob Seaman said: No reasonable standard can be based on constraining the behavior of our descendants 600 years hence. In what way is the requirement |DUT| = 0.9s not constraining the behaviour of our descendants 600 years hence? While I understand your argument about the name UTC: * *EVERY* approach requires constraining the behaviour of our descendants 600 years hence, just in different ways; * Universal Time is a *really* stupid name for a time scale based on the variable rotations of one small piece of rock. -- Clive D.W. Feather | Work: [EMAIL PROTECTED] | Tel:+44 20 8495 6138 Internet Expert | Home: [EMAIL PROTECTED] | Fax:+44 870 051 9937 Demon Internet | WWW: http://www.davros.org | Mobile: +44 7973 377646 Thus plc||
Re: GMT - UTC in Australia
John Cowan says: Secular changes in time zones (if by time zone you mean LCT - UTC, as I suppose) are something we already know how to handle, as they must be taken into account when determining historical UTC/GMT to LCT conversion. Indeed, some countries jigger the dates of their semiannual time changes annually, which is also a secular change in a small way. In addition, there is no reason why all the world's time zones must change in a synchronized way; ad hoc changes, as and when the problems become irritating, will be sufficient. Some jurisdictions might choose to change by half-hour offsets in only three centuries. Ad hoc is not a synonym for secular. I'm pleased to see someone other than the astronomers in this conversation using the word secular, but there continues to be a fundamental confusion of Daylight Saving clock adjustments (periodic) with the silly notion of leap hours (fundamentally secular). No reasonable standard can be based on constraining the behavior of our descendants 600 years hence. The only thing that emasculating UTC will accomplish is to allow sloppy system architects to continue to ignore the true requirements for choosing a time scale - with no guarantee that they'll get the requirement to handle a large and growing DUT1 right, any more than they appear to have gotten the requirement to handle leap seconds right. If a technical project requires unsegmented time, the architects should choose some flavor of TAI - GPS is a good example. If a technical project requires a clock slaved to the Earth's rotation, the architects should choose some flavor of UT. And if a project requires both, UTC is an excellent choice - it delivers TAI with a precision two orders of magnitude higher than its delivery of UT1. How about basing our discussions - and the IAU/IERS/BIPM/ITU-R deliberations - on the technical details of delivering *both* time signals with more complete worldwide coverage and a significantly improved level of precision and accuracy? If you want to buy the astronomers' support, that is surely the best way to do it. Meanwhile, my readings of the requirements for civil time are that the world's clocks should remain fundamentally rooted in time-of-day, not atomic time. Your interpretation may differ - I ain't got a problem with differences of opinion. What I have a problem with is the arrogant behavior of minor league bureaucrats who are seeking to effectuate a fundamental change to the philosophy of civil time without even considering consulting the civilians themselves. You can bet that the Australian legislators who are pushing this bill were given the impression that UTC is just a modern name for GMT - with the sub-text that Australia doesn't want to appear old-fashioned. You can bet that the so-called time lords didn't think to confuse the issue by droning on about the likely unhappy future of leap seconds. The only possible explanation for continuing to call civil time Coordinated Universal Time in the absence of leap seconds is that the public are being misled in order to sneak through this silly leap hour proposal. Whether any one of us supports the proposal or not, we should be able to reach agreement that misinformation is not the appropriate way to make public policy. Gedanken experiment: Call the new system of time resulting from the leap hour proposal International Time, TI for short. Walk through the front door of the world's parliaments and legislatures and attempt to sell TI as a high priority proposal. What would be the likely response? Rob Seaman National Optical Astronomy Observatory
Re: GMT - UTC in Australia
Rob Seaman scripsit: Ad hoc is not a synonym for secular. I'm pleased to see someone other than the astronomers in this conversation using the word secular, but there continues to be a fundamental confusion of Daylight Saving clock adjustments (periodic) with the silly notion of leap hours (fundamentally secular). Not by me. There have been genuinely secular changes in zone, call them silly or not: Pacific/Enderbury (Phoenix Islands Time) changed its time zone from -11:00 to +13:00 in 1995, and Asia/Kashgar (extreme western China) changed its time zone from -5:00 to -8:00 in 1980-05 (its LMT is 5:03:56). No reasonable standard can be based on constraining the behavior of our descendants 600 years hence. They are only constrained in the sense that Pope Gregory was constrained by the decisions of Julius Caesar. By 2600 we may simply not care about the apparent position of the sun (or anything else, perhaps). -- John Cowan [EMAIL PROTECTED] www.reutershealth.com www.ccil.org/~cowan [R]eversing the apostolic precept to be all things to all men, I usually [before Darwin] defended the tenability of the received doctrines, when I had to do with the [evolution]ists; and stood up for the possibility of [evolution] among the orthodox -- thereby, no doubt, increasing an already current, but quite undeserved, reputation for needless combativeness. --T. H. Huxley
Re: GMT - UTC in Australia
On Wed 2005-02-23T23:02:14 -0800, Steve Allen hath writ: [ the New South Wales bill ] defines UTC as being determined by the BIPM. So it remains unclear who ultimately controls the fate of civil time in New South Wales. There is sociology behind this statement. W. Lewandowski is Principal Physiscist at the BIPM time lab. He often chairs sessions at the various precise time conferences, and he did so at CGSIC last September. His introductory Powerpoint presentation is online as presentation number 60 at http://www.navcen.uscg.gov/cgsic/meetings/summaryrpts/44thmeeting/44th_CGSIC_agenda.htm In his slides 6 and 7 he indicates that the transition to uniform time would follow the recommendations of the Torino conference; i.e., a uniform time scale gets a new name. It is not clear that this dare be interpreted as a position statement by the BIPM, nor whether it represents a stance in opposition to the draft documents that the ITU-R has been circulating regarding its preferred re-definition of UTC. I suppose that there are individuals on both sides of the leaps-in-UTC issue at the BIPM, the IERS, and the ITU-R. That was the case at the BIH where the Stoykos championed earth rotation time while Guinot championed atomic time. The Stoykos died first, and with the demise of the BIH they have largely been omitted from the history of time keeping. That recalls the tag line in the posting on POSIX time: http://www.opengroup.org/platform/single_unix_specification/show_mail.tpl?source=Llistname=austin-group-lid= Time folk take their time, they do. Bet they have their time wars too, but they bury their dead in private. In the end the resolution of the leap second issue for civil time may also become a game of who dies first. -- Steve Allen UCO/Lick Observatory Santa Cruz, CA 95064 [EMAIL PROTECTED] Voice: +1 831 459 3046 http://www.ucolick.org/~sla PGP: 1024/E46978C5 F6 78 D1 10 62 94 8F 2E49 89 0E FE 26 B4 14 93
Re: GMT - UTC in Australia
There have been genuinely secular changes in zone, call them silly or not: Pacific/Enderbury (Phoenix Islands Time) changed its time zone from -11:00 to +13:00 in 1995, and Asia/Kashgar (extreme western China) changed its time zone from -5:00 to -8:00 in 1980-05 (its LMT is 5:03:56). Not silly - and not secular. Astronomers (at least) use the term secular to imply monotonic - and therefore cumulative - effects. The TZ changes mentioned are merely examples of single isolated events. Whether they make sense is a local decision. Are we really suggesting that local decisions are improved by ignorance? Perhaps part of the confusion is between definitions (for example, from m-w.com): 3a : occurring once in an age or a century Which is perhaps what Mr. Cowan means, and what the advocates of tolerance for bad temporal system design are certainly relying on. As opposed to what I mean: 3b : existing or continuing through ages or centuries The Earth's rotation will continue to slow (as a general trend) whether we ignore this fact or not. If we are choosing to ignore it, for god's sake at least don't bastardize the name UTC to mean something different than every other flavor of Universal Time. UTC is a useful approximation to GMT. Keep it that way and call any new system of civil time that might win the day something else. It is the height of intellectual dishonesty to do otherwise. Rob Seaman National Optical Astronomy Observatory
Re: GMT - UTC in Australia
UTC is a useful approximation to GMT. Rob, this will always be true, won't it? Whether you have 100 ms time step adjustments, or 100 x e-10 rate adjustments, leap seconds, or leap hours it seems to me there has been and will always be an honest attempt to coordinate the two scales. The question, in your assertion, is what constitutes useful and what magnitude is the approximation. /tvb
Re: GMT - UTC in Australia
Tom Van Baak scripsit: Rob, this will always be true, won't it? Whether you have 100 ms time step adjustments, or 100 x e-10 rate adjustments, leap seconds, or leap hours it seems to me there has been and will always be an honest attempt to coordinate the two scales. No, no. Leap hours are qualitatively different: they change the adjustment between TAI and LCT, ignoring earth rotation altogether. -- I marvel at the creature: so secret and John Cowan so sly as he is, to come sporting in the pool [EMAIL PROTECTED] before our very window. Does he think that http://www.reutershealth.com Men sleep without watch all night? --Faramir http://www.ccil.org/~cowan
Re: GMT - UTC in Australia and elsewhere
In message [EMAIL PROTECTED], Markus Kuhn writes: It seems that apart from the English versions, they all use an equivalent of either the French temps universel (universal time) or the German Weltzeit (world time). Oddly, of the ones I checked, only the Danish version explicitely mentiones UTC. And that is actually a mistake because legally Denmark is still using mean solar time (in Copenhagen I belive) :-) -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 [EMAIL PROTECTED] | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence.
Re: GMT - UTC in Australia
Steve Allen writes: Australia has decided to redefine its legal time scale. http://abc.net.au/science/news/space/SpaceRepublish_1307267.htm The last line in the article implies other jurisdictions are doing the same. The exact text of the laws would be interesting in order to see whether they intend that UTC be matched to mean solar days or not. A big question throughout all of the UTC discussions over the past five years is who they are and whether they have the ability to form a clear and consistent intent in the first place. Determining prior worldwide legal intent - and forming any (hopefully improved) future international legal consensus on civil time - should both be key to any proposed change to UTC. One has to wonder whether any individuals involved in the legal UTC debate in Australia were aware of the leap second controversy in the precision timing community. Whether this was the case or not, the wording of the quoted article makes it clear that UTC is being sold to everyday Australians in its original sense of being a continuing approximation to GMT: UTC is adjusted to remain consistent with GMT using leap seconds every 18 months. Rob Seaman National Optical Astronomy Observatory
Re: GMT - UTC in Australia
On Tue 2005-02-22T18:27:36 -0800, Steve Allen hath writ: Australia has decided to redefine its legal time scale. The bill was introduced today. Details of Bill 11 are found here. http://www.parliament.nsw.gov.au/cgi-bin/isys/isyswebext.exe?op=geturi=/isysquery/irl66ce/1/doc/#hit1 The text of the bill is here http://www.parliament.nsw.gov.au/prod/parlment/nswbills.nsf/0/de842061017f029eca256fb000169179/$FILE/b04-133-16-p01.pdf It defines UTC as being determined by the BIPM. Nowhere is the ITU-R mentioned. The BIPM says UTC is based on TAI, which is acknowledged to be their own responsibiliy, and leaps as determined by the IERS. So it remains unclear who ultimately controls the fate of civil time in New South Wales. But the explicit mention of the CGPM endorsement from 1975 could be interpreted to mean that NSW expects that UTC should conform to mean solar time, and thus it should have leaps. -- Steve Allen UCO/Lick Observatory Santa Cruz, CA 95064 [EMAIL PROTECTED] Voice: +1 831 459 3046 http://www.ucolick.org/~sla PGP: 1024/E46978C5 F6 78 D1 10 62 94 8F 2E49 89 0E FE 26 B4 14 93
GMT - UTC in Australia
Australia has decided to redefine its legal time scale. http://abc.net.au/science/news/space/SpaceRepublish_1307267.htm The last line in the article implies other jurisdictions are doing the same. The exact text of the laws would be interesting in order to see whether they intend that UTC be matched to mean solar days or not. -- Steve Allen UCO/Lick Observatory Santa Cruz, CA 95064 [EMAIL PROTECTED] Voice: +1 831 459 3046 http://www.ucolick.org/~sla PGP: 1024/E46978C5 F6 78 D1 10 62 94 8F 2E49 89 0E FE 26 B4 14 93
