Re: Risks of change to UTC
Professional and amateur astronomers are not the only ones who need good estimates of UT1. I've been wondering about this for a bit. Do astronomers and navigators actually want UT1 or do they want GMST? Since UT1 is based on a mean sun, which I guess no one actually observs, it would seem that GMST would be much more useful for figuring out your position or observing something. As far as I can see from my 1992 edition of the Explanatory Supplement to the Astronomical Almanac, UT1 and GMST were (defined?) to be related to one another by a cubic (2.24-1): GMST1 of 0hUT1 = 24110.54841s + 8640184.812877s T + 0.093104s T^2 + 0.062s T^3 What I don't know is: are the coefficients of this equation constant, or periodically updated by the IAU? Do astronomers, navigators and almanacs have to update their calculations when/if the IAU make a change? Why do I think they may change? Well, In older explanatory supplements to the IERS bulletins, such as this one: http://igscb.jpl.nasa.gov/mail/igsmail/1999/msg00077.html they give a reference for the relationship used as a paper by Aoki et al., 1982. However, in this more recent explanatory supplement: http://hpiers.obspm.fr/eoppc/bul/bulb/explanatory.html the relationship seems to have been changed to ones documented in (Capitaine et al., 2000, Capitaine et al., 2003, McCarthy and Petit, 2004). They say that that This relationship was developed to maintain consistency with the previous defining relationship, but I think this probably means that they were stitched together in a smooth way, not that they are identical. If it is the case that the GMST/UT1 relationship is changed regularly and astronomers/navigators have to keep up with those changes, then leap seconds could be put into this relationship (amounting to moving the mean sun when needed). I'm guessing that this suggestion is only slightly less crazy than strapping rockets onto the Earth to speed up its rotation ;-) David.
Re: Risks of change to UTC
M. Warner Losh said: 1500 years ago, no one spoke English. Chances are the people that deal with this problem in 1000 or 2000 years won't speak any language recognizable to anybody alive today. Why not? Greek and Latin, to name two, were spoken that long ago and are recognisable today. And the English of 1000 years ago is still an official language of the Netherlands (under the name Frisian). -- 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: the tail wags the dog
Steve Allen said: The official time of the US for commerce and legal purposes is UTC(NIST). The official time of the US DOD is UTC(USNO). The official time of the Federal Republic of Germany is UTC(PTB). etc. The official time of the UK is GMT. -- 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: Risks of change to UTC
On Mon 2006-01-23T11:08:29 +, David Malone hath writ: As far as I can see from my 1992 edition of the Explanatory Supplement to the Astronomical Almanac, UT1 and GMST were (defined?) the relationship seems to have been changed to ones documented in (Capitaine et al., 2000, Capitaine et al., 2003, McCarthy and Petit, 2004). They say that that This relationship was developed to maintain consistency with the previous defining relationship, but I think this probably means that they were stitched together in a smooth way, not that they are identical. The explanatory supplment is a place for revealed truth. The underlying process is only evident in the literature and reading between the lines of the reports of the triennial IAU General Assemblies. May I not so humbly suggest looking at http://www.ucolick.org/~sla/leapsecs/timescales.html for a slightly explained version with links to most of the papers and dates of changes. -- Steve Allen [EMAIL PROTECTED]WGS-84 (GPS) UCO/Lick ObservatoryNatural Sciences II, Room 165Lat +36.99858 University of CaliforniaVoice: +1 831 459 3046 Lng -122.06014 Santa Cruz, CA 95064http://www.ucolick.org/~sla/ Hgt +250 m
Re: the tail wags the dog
On Mon 2006-01-23T14:02:01 +, Clive D.W. Feather hath writ: Steve Allen said: The official time of the US for commerce and legal purposes is UTC(NIST). The official time of the US DOD is UTC(USNO). The official time of the UK is GMT. Please distinguish between official and legal. The legal time of the US is (in many more words) GMT. The officials who are charged by congress with the task of providing time provide UTC. The situation is exactly the same in the UK. http://www.npl.co.uk/time/truetime.html http://www.npl.co.uk/time/msf.html I reiterate that the tail wags the dog. -- Steve Allen [EMAIL PROTECTED]WGS-84 (GPS) UCO/Lick ObservatoryNatural Sciences II, Room 165Lat +36.99858 University of CaliforniaVoice: +1 831 459 3046 Lng -122.06014 Santa Cruz, CA 95064http://www.ucolick.org/~sla/ Hgt +250 m
Re: Risks of change to UTC
Clive D.W. Feather scripsit: Why not? Greek and Latin, to name two, were spoken that long ago and are recognisable today. Indeed, and they passed through a far tighter bottleneck than anything likely today. Not even the most diligently destructive barbarian can extirpate the written word from a culture wherein the *minimum* edition of most books is fifteen hundred copies. There are simply too many books. --L. Sprague de Camp, _Lest Darkness Fall_ And the English of 1000 years ago is still an official language of the Netherlands (under the name Frisian). Bread, butter, and green cheese / Is good English and good Friese. Brea, bûter, en griene tsiis / Is goed Ingelsk en goed Frysk. (That û is u-circumflex, in case of encoding problems.) -- Long-short-short, long-short-short / Dactyls in dimeter, Verse form with choriambs / (Masculine rhyme): [EMAIL PROTECTED] One sentence (two stanzas) / Hexasyllabically http://www.reutershealth.com Challenges poets who / Don't have the time. --robison who's at texas dot net
Re: wikipedia Leap Seconds collaboration
In message: [EMAIL PROTECTED] Neal McBurnett [EMAIL PROTECTED] writes: : Rob Seaman wrote: : I hope we can all continue this discussion in a more positive manner. : : It is the nature of email lists to be good at stimulating discussion, : and bad at generating clear resolutions. Thus was the FAQ born. But : we have a more modern technology than FAQs, the wiki, which can more : effectively funnel passionate energy from groups of people with : diverging ideas into coherent descriptions of a variety of viewpoints, : suitable for enlightening the world. Imperfectly, to be sure, but : better than a mail list : : I think the thing we need to do is build on what clarity we can find : in the moment, and document it at wikipedia. If the folks discussing : the Jesus article can arrive at a relatively stable set of positions : (and last time I looked, they had done remarkably well, considering), : surely we can also. : : Note the relatively successful policy of presenting things from a : Neutral Pointof View (NPOV): : : http://en.wikipedia.org/wiki/Wikipedia:Neutral_point_of_view : : So would folks be willing to collaborate at : : http://en.wikipedia.org/wiki/Leap_second : : and related pages? I've contributed to the unix time over leap seconds pages, and would be happy to help. I feel I can write a good argument for both sides, even though I have my preferences. Warner
Re: wikipedia Leap Seconds collaboration
Be careful. The goals of the folk on this mailing list and the goals of the wikipedia project are probably not aligned. http://en.wikipedia.org/wiki/Wikipedia:What_Wikipedia_is_not In particular, note the section Wikipedia is not a publisher of original thought. It is certainly possible for people on this list to help improve the wikipedia's coverage of articles related to time keeping, but the wikipedia article is not an appropriate place for a group attempting to hash out a consensus on a mailing list to record all of its thoughts. -Tim Shepard [EMAIL PROTECTED]
Re: the tail wags the dog
In message: [EMAIL PROTECTED] Steve Allen [EMAIL PROTECTED] writes: : The legal time of the US is (in many more words) GMT. : The officials who are charged by congress with the task of providing : time provide UTC. The legal time in the US is the mean solar time at a given meridian, as determined by the secretary of commerce (the actual law is a little more verbose than this, but this is an accurate boil down) plus some weird options for 'border states' which timezone they are in. This is why NIST provides UTC and leap seconds happen on the UTC schedule rather than some other schedule that would produce the same results. It is also why there are leap seconds and not the old-style frequency adjustments + tiny steps. Both of these schemes fit the law, as it is rather vague in the words it uses in a legal sense (the term mean solar time isn't legally defined, but does have an accepted scientific meaning). Other schemes could also fit the law that aren't UTC today since there's no what we would call 'DUT1 tolerance' written into the law... Warner
Re: wikipedia Leap Seconds collaboration
On Mon, Jan 23, 2006 at 11:20:45AM -0500, Tim Shepard wrote: Be careful. The goals of the folk on this mailing list and the goals of the wikipedia project are probably not aligned. http://en.wikipedia.org/wiki/Wikipedia:What_Wikipedia_is_not In particular, note the section Wikipedia is not a publisher of original thought. It is certainly possible for people on this list to help improve the wikipedia's coverage of articles related to time keeping, but the wikipedia article is not an appropriate place for a group attempting to hash out a consensus on a mailing list to record all of its thoughts. Thanks - very true. An important point is that folks should include references to other sources. But there are a ton of other sources, and when we're behaving well, we already reference them in these discussions. I think having more folks working on wikipedia will both help our discussion here, and encourage folks to generate web pages and other sources for new proposals. My wikipedia talk page contains a number of relevant policy references, some of which may be a bit dated: http://en.wikipedia.org/wiki/User_talk:Nealmcb And note that it is good practice to discuss major or controvertial proposed changes to, e.g. the leap seconds page, at the associated discussion page, e.g. http://en.wikipedia.org/wiki/Talk:Leap_second Cheers, Neal McBurnett http://bcn.boulder.co.us/~neal/ Signed and/or sealed mail encouraged. GPG/PGP Keyid: 2C9EBA60
Re: the tail wags the dog
Rob Seaman scripsit: The legal time in the US is the mean solar time at a given meridian, as determined by the secretary of commerce ...and many may have seen Mr. Gutierrez shooting the sun with his sextant out on the Mall in front of the AS Museum :-) With all the words that have flowed over the spillway, I'm not sure the point has been made that a feature of solar time is precisely that it can be reliably recovered from observations whenever and wherever needed (once you are located with respect to a meridian, of course). I don't understand this. You can't shoot the mean sun with a sextant, only the friendly (apparent, whatever) sun. So at the very least you need an analemma. In any case, the majority of the world has managed to live with the fact that the day-of-month can no longer be recovered by examining the moon, although if we were still hunter-gatherers a purely lunar calendar would make a lot of sense. -- XQuery Blueberry DOMJohn Cowan Entity parser dot-com [EMAIL PROTECTED] Abstract schemata http://www.reutershealth.com XPointer errata http://www.ccil.org/~cowan Infoset Unicode BOM --Richard Tobin
