Re: ITU Meeting last year
[EMAIL PROTECTED] wrote on 2005-01-19 20:19 UTC: A resolution was proposed to redefine UTC by replacing leap seconds by leap hours, effective at a specific date which I believe was something like 2020. Thanks for the update! Did the proposed resolution contain any detailed political provisions that specify, who exactly would be in charge of declaring in about six centuries time, when exactly the first UTC leap hour should take place? Will IERS send out, twice a year, bulletins for the next *600 years*, announcing just that UTC will continue as usual for the next 6 months? Not the most interesting mailing list to be on ... And when the day comes, will people still recognize the authority of IERS and ITU in such matters? Keep in mind that the names, identities, and structures of these instritutions will likely have changed several times by then. Also keep in mind that any living memory of the last UTC leap will then have been lost over twenty generations earlier. The subject won't get any less obscure by making the event a 3600x more rare occasion. If this proposal gets accepted, then someone will have to shoulder the burden and take responsibility for a gigantic disruption in the global^Wsolar IT infrastructure sometimes around 2600. I believe, the worry about Y2K was nothing in comparison to the troubles caused by a UTC leap hour. We certainly couldn't insert a leap hour into UTC today. In my eyes, a UTC leap hour is an unrealistic phantasy. Judging from how long it took to settle the last adjusting disruption of that scope (the skipping of 10 leap days as part of the Gregorian calendar reform), I would expect the UTC leap hour to become either very messy, or to never happen at all. Who will be the equivalent of Pope Gregory XIII at about 2600 and where would this person get the authority from to break thoroughly what was meant to be an interrupt-free computer time scale. Even the, at the time, almightly Catholic Church wasn't able to implement the Gregorian transition smoothly by simply decreeing it. Do we rely on some dictator vastly more powerful than a 16-th century pope to be around near the years 2600, 3100, 3500, 3800, 4100, 4300, etc. to get the then necessary UTC leap hour implemented? Remember that UTC is used today widely in computers first of all because it *lacks* the very troublesome DST leap hours of civilian time zones. Most of the existing and proposed workarounds for leap seconds (e.g., smoothing out the phase jump by a small temporary frequency shift) are entirely impractical for leap hours. Please shoot down this leap-hour idea. The problem is not solved by replacing frequent tiny disruptions with rare catastrophic ones. It is hardly ethical to first accept that a regular correction is necessary, but then to sweep it under the carpet for centuries, expecting the resulting mess to be sorted out by our descendents two dozen generations later on. Leap hours are 3600 more disruptive than leap seconds! If ITU wants to turn UTC into an interrupt-free physical time scale decoupled from the rotation of the Earth, then it should say so honestly, by defining that UTC will *never* ever leap in any way, neither by a second, nor by an hour. Markus -- Markus Kuhn, Computer Lab, Univ of Cambridge, GB http://www.cl.cam.ac.uk/~mgk25/ | __oo_O..O_oo__
Re: ITU Meeting last year
Markus Kuhn said: A resolution was proposed to redefine UTC by replacing leap seconds by leap hours, effective at a specific date which I believe was something like 2020. [...] If this proposal gets accepted, then someone will have to shoulder the burden and take responsibility for a gigantic disruption in the global^Wsolar IT infrastructure sometimes around 2600. I believe, the worry about Y2K was nothing in comparison to the troubles caused by a UTC leap hour. We certainly couldn't insert a leap hour into UTC today. In my eyes, a UTC leap hour is an unrealistic phantasy. [...] I may be wrong here, but I thought the leap hour idea did *not* insert a discontinuity into UTC. Rather, in 2600 (or whenever it is), all civil administrations would move their local-UTC offset forward by one hour, in many cases by failing to implement the summer-to-winter step back. Thus in the UK and the US eastern seaboard, the civil time would go: UK US east Summer 2599: UTC + 0100UTC - 0400 Winter 2599/2600: UTC + UTC - 0500 Summer 2600: UTC + 0100UTC - 0400 Winter 2600/2601: UTC + 0100UTC - 0400 Summer 2601: UTC + 0200UTC - 0300 Winter 2601/2602: UTC + 0200UTC - 0400 That *is* practical to implement, though coordination might be harder. On the other hand, adminstrative areas that are near the edge of a zone now could move earlier if they wanted. The world is used to time zones, after all. -- 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: ITU Meeting last year
Markus Kuhn scripsit: In my eyes, a UTC leap hour is an unrealistic phantasy. I agree. But the same effects can be achieved by waiting for local jurisdictions to change the existing LCT offsets as the problem becomes locally serious. They've done it many times in the past and can easily do so again. The fact that America/New_York is either five or four hours behind UTC is not carved in stone anywhere, it's just what happens to work right now. A change to being either four or three hours behind will not have nearly the same disruptive effect as a disruption in UTC. And perhaps people won't even bother. If people in Urumqi right now can tolerate a three-hour difference between LMT and LCT, a slightly different relation between the sun and the clock may seem quite tolerable to our great^20-grandchildren. (Astronomers will howl. They doubtless howled when we broke the connection between the calendar and the synodic month, too. IERS can even maintain OldUTC for their benefit; what matters is what the basis of LCT is, since we all live our lives primarily by LCT.) -- In politics, obedience and support John Cowan [EMAIL PROTECTED] are the same thing. --Hannah Arendthttp://www.ccil.org/~cowan
Re: ITU Meeting last year
Clive D.W. Feather scripsit: That *is* practical to implement, though coordination might be harder. On the other hand, adminstrative areas that are near the edge of a zone now could move earlier if they wanted. The world is used to time zones, after all. For that matter, Newfoundland could decide to change its offset from the current -0330 to -0300 in 2300, and then leave it alone until 2900. The world would spin on quite unaffected. (Newfie joke suppressed here.) -- John Cowan [EMAIL PROTECTED] http://www.reutershealth.comhttp://www.ccil.org/~cowan Humpty Dump Dublin squeaks through his norse Humpty Dump Dublin hath a horrible vorse But for all his kinks English / And his irismanx brogues Humpty Dump Dublin's grandada of all rogues. --Cousin James
Re: ITU Meeting last year
Clive D.W. Feather wrote on 2005-01-20 12:34 UTC: A resolution was proposed to redefine UTC by replacing leap seconds by leap hours, effective at a specific date which I believe was something like 2020. I may be wrong here, but I thought the leap hour idea did *not* insert a discontinuity into UTC. I think, the phrase to redefine UTC by replacing leap seconds by leap hours can only mean going from |UTC - UT1| 1 s to something like |UTC - UT1| 1 h (or some other finite |UTC - UT1| bound like that). That was certainly the idea of the BIPM proposal presented at the Torino meeting. Rather, in 2600 (or whenever it is), all civil administrations would move their local-UTC offset forward by one hour, in many cases by failing to implement the summer-to-winter step back. Such a proposal would be called to redefine UTC by eliminating future leaps (i.e., by establishing a fixed offset between UTC and TAI). It seems perfectly practical, at least as long as |UTC - UT1| 24 h (i.e., for the next 5000 years). What local governments with regional civilian time zones do is outside the influence of the ITU. But if leap seconds were eliminated from UTC and a fixed TAI-UTC offset defined instead, then what you describe above is indeed what I would expect to happen with most of them. Unless we give up the notion of local time zones entirely, there would be a clear need to keep them locked to UT1 + offset to within an hour or so. Markus -- Markus Kuhn, Computer Lab, Univ of Cambridge, GB http://www.cl.cam.ac.uk/~mgk25/ | __oo_O..O_oo__
Re: ITU Meeting last year
On Thu 2005-01-20T13:39:58 +, Markus Kuhn hath writ: That was certainly the idea of the BIPM proposal presented at the Torino meeting. As seen on my online bibliography web page, the proposal probably was a slightly evolved form of this document http://www.fcc.gov/ib/sand/irb/weritacrnc/archives/nc1893wp7a/1.doc -- 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: ITU Meeting last year
In message [EMAIL PROTECTED], John Cowan writes: Markus Kuhn scripsit: In my eyes, a UTC leap hour is an unrealistic phantasy. I think your critizism of it is just as unrealistic. If 600 years down the road we have colonized the solar system, then a large fraction of the population wouldn't care about terrestial solar time anyway, and I'm sure the leap hour will be cancled well in advance. Given that the average western citizen under 30 years already today can barely add up three items in the supermarket without resorting to their mobile phones built in calculator today, I think you can safely assume that you can do anything to the timescale 100 years from now. At that time most people will just as they're told on television (probably in 3D and with full olfactory support) and the few scientists who care will be bogged down in a very theoretical discussion about what it would have done to the cows milk, had cows not been outlawed for foodstuff production many years ago. Considering that the last couple of changes to our timescales were forced through in very short time, say 20 years to be very generous then we can change our timescales 130 times between now and the first leap-hour, and that is provided earthquakes and yet unknown geophysics don't make them unnecessary or make it more necessary. We certainly don't need to decide now who is going to call the leap hour 600 years from now, all we need to decided is who gets to call it as long as the next treaty on time is in force. If that turns out to be 600 years, then it stands for 600 years, if ten years from now we find out what the real nature of time is and need to make a new timescale, then somebody had an easy job for 10 years. The one thing we don't need is flaming rethoric... -- 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: ITU Meeting last year
In message [EMAIL PROTECTED], Tom Van Baak writes: If one uses the rough but often-quoted figure of one leap second about every 500 days then a leap hour would be required on the order of 500 * 3600 / 365 = ~5000 years from now. It's not a linear curve, it's quadratic. I found some slides from the torino meeting where this was laid out very well but I didn't save the URL, sorry. -- 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: ITU Meeting last year
On Thu 2005-01-20T09:33:01 -0800, Tom Van Baak hath writ: So it's safe to say we're talking millennia rather than centuries, yes? I wonder where the notion that it's just a few centuries away came from. If there is something not clear in the presentation on http://www.ucolick.org/~sla/leapsecs/dutc.html I would be obliged to know about it. -- 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: TAI-UT1 prediction
Tom Van Baak wrote on 2005-01-20 17:33 UTC: No one can know for sure but I was wondering if there is a consensus on when the first leap hour would occur? A good table summary of some projections is in http://www.ucolick.org/~sla/leapsecs/dutc.html#dutctable and other discussions are on http://www.ien.it/luc/cesio/itu/ITU.shtml and there in particular in Prediction of Universal Time and LOD Variation - D. Gambis and C. Bizouard, (IERS) http://www.ien.it/luc/cesio/itu/gambis.pdf Even to an order of magnitude? I ask because the above document draft says at least 500 years while others here cite numbers like 600 years, or 5000 years. 5000 years until the next leap second sounds like someone got some very basic maths wrong (by then, a whole leap day would be due), the other two figures sound feasible. Perhaps a confusion about the rotation of earth (UT1 clock frequency) slowing down roughly linearly, therefore the accumulation of the phase difference being (after integrating) an essentially quadratic function? Markus -- Markus Kuhn, Computer Lab, Univ of Cambridge, GB http://www.cl.cam.ac.uk/~mgk25/ | __oo_O..O_oo__
Re: ITU Meeting last year
It's not a linear curve, it's quadratic. I found some slides from the torino meeting where this was laid out very well but I didn't save the URL, sorry. Ah, yes, I forgot the quadratic term. Steve Allen has a nice page at: http://www.ucolick.org/~sla/leapsecs/dutc.html And his table shows the first leap hour would occur in the year 2500 to 2600 time frame. So that's where the 500 or 600 year value people quote comes from; it's a few centuries from now, not millennia afterall. Thanks, /tvb http://www.LeapSecond.com
Re: ITU Meeting last year
In message [EMAIL PROTECTED], Steve Allen writes: On Thu 2005-01-20T09:33:01 -0800, Tom Van Baak hath writ: So it's safe to say we're talking millennia rather than centuries, yes? I wonder where the notion that it's just a few centuries away came from. If there is something not clear in the presentation on http://www.ucolick.org/~sla/leapsecs/dutc.html I enjoyed your page a lot some time ago when I fell over it. Thanks a lot for the effort. -- 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: ITU Meeting last year
On Thu 2005-01-20T12:34:09 +, Clive D.W. Feather hath writ: I may be wrong here, but I thought the leap hour idea did *not* insert a discontinuity into UTC. Rather, in 2600 (or whenever it is), all civil administrations would move their local-UTC offset forward by one hour, in many cases by failing to implement the summer-to-winter step back. The text of the document from USWP 7A continues the trend that has been displayed publicly for several years now, namely that UTC would officially switch from leap seconds to leap hours. This is clearly an artifice, for there can be no expectation that people 5 centuries hence will respect the content of any revision of ITU-R TF.460 made today. It is not even clear that the BIPM is ready to respect it now. Looking at the players, however, a plausible reason for the artifice becomes clear. Many of the proposers are employees of agencies of the US Federal government. Under federal law the legal time of the United States is specified as mean astronomical time, and in the parlance of the era of that legislation that clearly must be interpreted as the form of earth rotation time known as mean solar time. The most recent attempt to change the wording of the US Code failed. To propose the complete abolition of leaps would be to propose a time scale which demonstrably violates federal law. To propose leap hours is to propose an artifice which keeps the proposers from using their positions to advocate a violation of federal law. Legal fiction is a well-tested means of effecting change. It is hard to say what the actual intent is when so few documents have made it out of the inner sanctum of the Time Lords. In the hopes of enlightenment for this list, but without the ability to authenticate these draft documents, I offer the following: http://www.ucolick.org/~sla/leapsecs/SRG7Afinalreport.doc http://www.ucolick.org/~sla/leapsecs/PropRevITU-RTF460-6.doc It seems that atomic clock keepers have lost all interest in the continued existence of mean solar time, sundials, or the analemma. -- 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: ITU Meeting last year
In message [EMAIL PROTECTED], Steve Allen writes: In the hopes of enlightenment for this list, but without the ability to authenticate these draft documents, I offer the following: http://www.ucolick.org/~sla/leapsecs/SRG7Afinalreport.doc http://www.ucolick.org/~sla/leapsecs/PropRevITU-RTF460-6.doc Looks good to me. It seems that atomic clock keepers have lost all interest in the continued existence of mean solar time, sundials, or the analemma. And why shouldn't they ? The job of atomic clock keepers is to keep TAI ticking. I really can't see any problem with the proposal above which even get into the same order of magnitude to the problems and inconvenience leapseconds are today. And I applaud them for setting a transition date which I think would spare us for even one more leap-second. As a private person living at 11°20'22.98 the sun is never in south at noon anyway and we have voluntarily moved it a further 15° away from south half the year already with daylights savings time. I already need to adjust my sundial twice a year anyway (OK, so I'm also at 55°N24' so it's not much use during winter so I don't actually bother but that's besides the point :-). As a computer nerd I can fully appreciate the problems and cost of converting existing systems to cope with larger UT1/UTC difference, but that cost would be peanuts compared to the costs of implementing leap-seconds reliably in future systems that would need it. And for that conversion cost: Just how hard is it to make a computer synchronize with NTP over the internet, pick the DUT1 up from IERS homepage and emit clocksignals which are UT1 approximations for those old computers anyway ? I know several operations computers here in Denmark which think it is 1985 because they cannot cope properly with years in a different century, people can live with that kind of quirk in old computers. Finally as goes with navigation, here in Denmark celestial navigation is now taught as a historical interest course... So yes, we might loose a ship or two if they for some reason rely on celestial navigation. Chances are very good that they were in dire straits already, otherwise they wouldn't have taken their eye off the GPS receiver and the radar long enough to locate the sekstant. Compare that to the number of deaths of just one major software bug triggered by a leapsecond, and things come into perspective nicely. -- 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: ITU Meeting last year
Steve Allen scripsit: If there is something not clear in the presentation on http://www.ucolick.org/~sla/leapsecs/dutc.html I would be obliged to know about it. It's very clear and useful. But: At Torino the proponents of omitting leap seconds supposed that the governments of the world might handle this situation using leap hours introduced into civil time by occasionally omitting the annual ``spring forward'' change to jump to summer/daylight time. However there are serious questions raised by the notion of a leap hour. Given that the first leap hour would not happen for centuries, it is not clear that any systems (legal or technological) would build in the necessary complexity for handling it. Systems already have existing mechanisms for handling large secular changes in LCT. There are many places that adjust their daylight time mechanisms on a yearly basis anyhow. -- Where the wombat has walked,John Cowan [EMAIL PROTECTED] it will inevitably walk again. http://www.ccil.org/~cowan
two world clocks
I keep trying to find time to generate a reply to all the points raised (yet again) during this go-around. New messages keep arriving in the mean time (a phrase that appears to be under attack). Thanks to Demetrios Matsakis for keeping us informed. Thanks to Markus Kuhn for doing a nice job of summarizing why converting to leap hours is equivalent to not bothering to attempt to keep our clocks tracking time-of-day at all. Thanks to my friend Steve Allen for continuing to fight the good fight. There are several issues to address. If I'm going to actually send this I won't get beyond the first such. Surely others must find it remarkable how willing the precision timing community is to pursue the goal of completely eviscerating the delivery of precision time-of-day to the public? Are statements like the following really how you want to sell your product to your funding agencies? Given that the average western citizen under 30 years already today can barely add up three items in the supermarket without resorting to their mobile phones built in calculator today, I think you can safely assume that you can do anything to the timescale 100 years from now. Shouldn't we work to educate the public, not use their ignorance of some issue as justification for degrading service? Poul-Henning Kamp also wrote: As a computer nerd I can fully appreciate the problems and cost of converting existing systems to cope with larger UT1/UTC difference, but that cost would be peanuts compared to the costs of implementing leap-seconds reliably in future systems that would need it. If you expect astronomers and other supporters of the current Universal Time system to repeatedly justify continuing to use the definition of Mean Solar Time that has persisted since 1884, perhaps you could consider doing us the favor of justifying your own statements. What exact future systems are we discussing that will both 1) require the use of Universal Time and 2) not require a definition of Universal Time that is tied to the rotating Earth? I have yet to hear of a system that has trouble handling leap seconds that wouldn't have been better off using TAI instead of UTC. I have yet to hear of a system that has trouble handling leap seconds that wasn't poorly engineered in its handling of time standards. Why should the rest of us pay for some project's bad requirements discovery, bad design and bad implementation? Imagine that the underlying time standards are, indeed, changed. Why should we have any greater expectation that the same suspect engineers wouldn't make a mess of using the new standards? Attempting to move the entire worldwide civil time system to a non-Earth based clock is equivalent to attempting to build a clock designed to run untended for 600 years - in effect, to attempting to build a millennium clock. The alarm must be designed to ring in 599 years time. The trouble with this is not only that it is a massive problem in systems engineering. The trouble with this is that the sociology of time-keeping is working against you. How naive to suppose that anyone will be paying attention when the alarm rings! If you want engineers to build systems that correctly incorporate handling of some phenomenon, you don't require that this phenomenon only be handled every half millennium. That is a recipe for more lazy engineering. Leap seconds are a perfectly workable mechanism. Systems that don't need time-of-day should use TAI. Systems that do need time-of-day often benefit from the 0.9s approximation to UT1 that UTC currently provides. Let's stop pretending that *both* atomic time and time-of-day are not needed. Instead, let's direct our efforts toward implementing improved systems for conveying both of these fundamental timescales to users of both precision and civil time. And most definitely, let's stop these inane and embarrassing closed door discussions among biased insiders. It ain't your clock - it's *our* clock. Rob Seaman National Optical Astronomy Observatory
Re: two world clocks
Rob Seaman scripsit: What exact future systems are we discussing that will both 1) require the use of Universal Time and 2) not require a definition of Universal Time that is tied to the rotating Earth? *sigh* LCT is currently tied to UTC, and converting a count of SI seconds to a UTC time is currently (a) annoying and (b) depends on updating tables. Attempting to move the entire worldwide civil time system to a non-Earth based clock is equivalent to attempting to build a clock designed to run untended for 600 years - in effect, to attempting to build a millennium clock. The alarm must be designed to ring in 599 years time. This is simply not true. The LCT-TI offsets can be adjusted locally as and when they individually start to be a problem. No global changeover is required. Systems that don't need time-of-day should use TAI. Wall clocks need to run in LCT, which is currently founded on UTC. Most people don't need precision time-of-day (which should be rightly called Earth angle and measured in SI radians). They just need there to be a rough correlation between LCT and the sun, and several hours' discrepancy can be tolerated. Just go to Urumqi, or Detroit if Urumqi is too remote. And most definitely, let's stop these inane and embarrassing closed door discussions among biased insiders. Personally, I am a biased outsider. It ain't your clock - it's *our* clock. Eh? Who are you and who are we? -- Not to perambulate John Cowan [EMAIL PROTECTED] the corridors http://www.reutershealth.com during the hours of repose http://www.ccil.org/~cowan in the boots of ascension. --Sign in Austrian ski-resort hotel
Re: two world clocks
In message [EMAIL PROTECTED], Rob Seaman writes: Given that the average western citizen under 30 years already today can barely add up three items in the supermarket without resorting to their mobile phones built in calculator today, I think you can safely assume that you can do anything to the timescale 100 years from now. Shouldn't we work to educate the public, not use their ignorance of some issue as justification for degrading service? Absolutely! but if you read your classics (relevant keywords: bread and circus) you would not expect much success. Poul-Henning Kamp also wrote: As a computer nerd I can fully appreciate the problems and cost of converting existing systems to cope with larger UT1/UTC difference, but that cost would be peanuts compared to the costs of implementing leap-seconds reliably in future systems that would need it. I think you got the sign of my position wrong here: The cost of conversion has been used to argue _for_ keeping the leap seconds, and I say that the cost of _keeping_ the leapseconds will be much higher in terms of software development and testing. I have yet to hear of a system that has trouble handling leap seconds that wasn't poorly engineered in its handling of time standards. Why should the rest of us pay for some project's bad requirements discovery, bad design and bad implementation? Imagine that the underlying time standards are, indeed, changed. Why should we have any greater expectation that the same suspect engineers wouldn't make a mess of using the new standards? The concern I have met from computing system owners is not that they worry _if_ their system will handle leapseconds, but that they don't know _how_ it will handle them. The major problem with leapseconds in computer systems is that they do not happen often enough to be testable, and for anything networked, they are untestable unless we set up dedicated fake time NTP servers (like Judah did for y2k), have reliable GPS simulators etc etc. I saw one test plan for a major safety-of-life system were they dropped leap second testing because the sheer enormity of doing so, including fake GPS, DCF77 and NTP timesources where simply not possible, some of them even illegal. Their plan: Hope leap-seconds are killed. Ther fall-back plan: Shut down for an hour citing emergency computer problems and take the political flack afterwards. You don't even want to know how much money that would cost in lost throughput if leapseconds didn't happen an hour past midnight here. No such relief for the asians. Attempting to move the entire worldwide civil time system to a non-Earth based clock is equivalent to attempting to build a clock designed to run untended for 600 years - in effect, to attempting to build a millennium clock. No it isn't. This is a rubbish argument and you know it. No matter how reasonable Brahe, Keppler and Newton had been, no matter how well they had worked out their plan, no matter how much they had tuned it to their society, we would never have executed it today according to their design without checking, double checking and reevaluation of their premises. And neither are our great^N-grandchildren going to. We are not designing a new timescale to last 600 years here, we are designing a timescale for the next century at best, and given the statistics we should consider ourselves luck if it holds even half that long before somebody finds something wrong with it. If you want engineers to build systems that correctly incorporate handling of some phenomenon, you don't require that this phenomenon only be handled every half millennium. It's not the frequency of the phenomena that is the problem, it's the magnitude. Nobody puts an entire IT department on call for a one second event, you just can't justify the expense to top management and more importantly, with half a years notice you can't budget for it. But every IT manager would do so for an one hour event. The really smart ones will plan their three hours of maintenance to coincide with the event. Leap seconds are a perfectly workable mechanism. For who ? For astronomers ? For computer programmers ? For risk managers ? For insurance companies ? Or do you mean because they're so small that most people just ignore them and since we're in the center/western hemishere we mostly get away it ? Ask the asians what they think of having that second in the middle of the day, then come back and call it workable once more. Let's stop pretending that *both* atomic time and time-of-day are not needed. Instead, let's direct our efforts toward implementing improved systems for conveying both of these fundamental timescales to users of both precision and civil time. And most definitely, let's stop these inane and embarrassing closed door discussions among biased insiders. It ain't your clock - it's *our* clock. I agree, but we have to be realistic and either you are not or you don't know what you need to be
Re: two world clocks
John Cowan replies to my question: What exact future systems are we discussing that will both 1) require the use of Universal Time and 2) not require a definition of Universal Time that is tied to the rotating Earth? LCT is currently tied to UTC, and converting a count of SI seconds to a UTC time is currently (a) annoying and (b) depends on updating tables. Civil time is indeed tied to Universal Time, and UT is defined to be (basically) equivalent to Greenwich Mean Time. This whole discussion is about some obscure committee seeking to change a standard that was founded, more-or-less in its current form, at the Longitude Conference in 1884 (historical corrections welcome, but pick your nits somewhere else). The attendees of the Longitude Conference were high level representatives of the world's great powers. The attendees of the obscure meetings related to the current leap second debate are themselves obscure - well - nerds, like all of us reading this list. To comment on your particular points: a) Clearly I'm annoyed about other aspects of this situation than you are. Why should the annoyance of members of the ITU matter more than the annoyance of other parties? b) Currently the tables are maintained and updated by members of the precision timing community who should indeed be commended for their excellent work over the last quarter century and more. The proposal on the table would require all 6+ billion of us to keep his or her own tables up-to-date. The current situation is better. Wall clocks need to run in LCT, which is currently founded on UTC. Most people don't need precision time-of-day (which should be rightly called Earth angle and measured in SI radians). They just need there to be a rough correlation between LCT and the sun, and several hours' discrepancy can be tolerated. Just go to Urumqi, or Detroit if Urumqi is too remote. Isn't this just a wee bit arrogant? (I toned that down from another word starting with r.) People need good sources of time for a variety of reasons. We are discussing a complete abandonment of the provision of Earth rotation information to the civilian public worldwide. I won't belabor the point of why I think that is bad. The question is, why aren't the precision time keepers debating ways to improve the delivery of time signals to the world community, rather than debating how best to sneak through a proposal to degrade time services? It ain't your clock - it's *our* clock. Eh? Who are you and who are we? I would think that is obvious. You refers to a couple of dozen temporal bureaucrats who likely don't care enough about this issue that they find themselves playing politics with to even bother reading, let alone replying to, this mailing list. We refers to the six billion (and growing) of the rest of us. Civil time is a hell of a fundamental standard to be so whimsically managed. If there are improvements needed - in the short term - to the standard, let's hear the evidence. That long term changes are needed is no surprise (see http://iraf.noao.edu/~seaman/leap for my analysis of the situation), but what the hell is the hurry? Rob Seaman National Optical Astronomy Observatory
Re: two world clocks
Rob Seaman scripsit: b) Currently the tables are maintained and updated by members of the precision timing community who should indeed be commended for their excellent work over the last quarter century and more. The proposal on the table would require all 6+ billion of us to keep his or her own tables up-to-date. The current situation is better. I don't understand that at all. People who need Earth angle (and I am *not* opposed to making that widely available) will need to pick up a correction table from IERS, there's no doubt about that. IERS will continue in exactly its current mission, it's just that its output will no longer affect the value of LCT. And as for keeping tables up to date, that's exactly what programmers (especially programmers of embedded systems) are complaining about having to do now, just to track UTC and LCT. People need good sources of time for a variety of reasons. We are discussing a complete abandonment of the provision of Earth rotation information to the civilian public worldwide. Not at all. We are simply abandoning the notion that LCT is the right way to provide that information. -- Henry S. Thompson said, / Syntactic, structural, John Cowan Value constraints we / Express on the fly. [EMAIL PROTECTED] Simon St. Laurent: Your / Incomprehensible http://www.reutershealth.com Abracadabralike / schemas must die!http://www.ccil.org/~cowan
Re: two world clocks
Poul-Henning Kamp replies: The major problem with leapseconds in computer systems is that they do not happen often enough to be testable, The current UTC standard allows scheduling leap seconds monthly. Is that frequent enough for you? The question isn't whether a leap second occurs. The question is how frequently do opportunities for a leap second occur. I saw one test plan for a major safety-of-life system were they dropped leap second testing because the sheer enormity of doing so, And you are asserting that this is a system that would not have better chosen an unsegmented timescale based on TAI? Or perhaps this system also has a requirement that no other glitches ever be allowed to occur within the clocks? What actual requirement did this system have that equated the preservation of life with tracking UT1? And if there was such a requirement, are you not providing a strong argument for the precision timing community to continue to provide an easily accessible approximation to UT1? Their plan: Hope leap-seconds are killed. Remind me not to rely on their system for my own safety. So their system requires a clock synced to civil time to keep people alive. Does it also suspend a 500 kilo weight over the operator's console with the rope connected to an alarm clock set to go off at the end of June and December? We can pass anecdotes back-and-forth all day long. Is the ITU or some other organization pushing this change actually compiling useful data on all these anecdotes? Ther fall-back plan: Shut down for an hour citing emergency computer problems and take the political flack afterwards. You don't even want to know how much money that would cost in lost throughput if leapseconds didn't happen an hour past midnight here. Yes. I do want to know. Or rather, I want to have confidence that the bureaucrats pushing this silly initiative are actually investing in the world-wide inventory of time users that is warranted by a scheme to change every clock on the planet. The systems which need UT1(-like) time are staffed by very smart people. The systems which need civil time are not. Many of them don't know that other parts of the globe have different time, fewer yet know what the difference is. Sounds like a great business opportunity. There are large numbers of much more obscure standards that programmers manage to get right. What reliable evidence do we have that programmers are screwing up UTC left-and-right? Couldn't we just invest in improving the NTP handling of leap seconds and in implementing new time handling facilities *before* we go about deprecating leap seconds? Today my civil time is already up to one and a half hour wrong according to solar time. Scottland is debating making it up to two and a half hour wrong in order to be in the same zone as most of EU, and some of the new EU member states are discussing making it one or two hours wrong in the other direction for the same reason. On average most of USA must be half an hour off center as well. These are either periodic effects or constant offsets. Leap seconds are due to a secular effect. That secular effect won't go away just because some folks wish very hard. The numbers we attach to civil time have nothing to do with noon, mid-day and such mundane concepts. They actually have very precise, closed form approximations to those concepts. Many of us like the equation of time. Why throw it out? Civil time does not have to be linked hard to the sun as long as it doesn't change too fast. Civil time is used for a myriad of purposes. One might think that the precision timing community would be an excellent choice of folks to enumerate these various purposes. This has not been demonstrated over the past five years. Rather we've seen one lame and lazy attempt after another to avoid doing the detailed leg work needed before changing such a fundamental standard. On the other hand, astronomers and others that need UT1 will be able to take the global timescale, (TAI, UTC or something else) and apply a delta they pick up from a scientific entitity and use the result. As you imply, a vast amount of astronomical software and systems would indeed need to be modified quickly and reliably simply to preserve the current functioning of our systems. Today most of them already have to pick up a +/- 1second delta anyway, No. I would guess that most of them manage to work within the +/- 0.9s approximation of UTC to UT1. Entirely new code and systems would need to be fielded. And yet somehow the precision timing community doesn't make it a priority to explore these new systems. Could it be that this is simply an attempt to dump the tracking of Universal Time back in the laps of the original timekeepers, the astronomers? Many of the people who need civil time still have a hard time with leap years and daylight savings time, and since a lot of these people inexplicably are tasked to implement and code life critical systems, you should not task
