[LEAPSECS] Cheating means more planning, not less
I wrote: Whatever the preferences of the ITU, they will discover that it is simply unacceptable to allow local dates to vary secularly from civil timekeeping dates. Tony Finch replies: Civil time *is* a form of local time. The question isn't about haggling over terminology. We've had that discussion before. Rather, a clock can be deposited at any meridian on any planet, set to any time, running at any rate. The question is whether a particular choice of parameters is useful and sustainable. Additionally if a planet has populations scattered at wide longitudes, the more basic requirement is to organize a coherent system to manage the whole. Identifying the length of the civil day with the length of the mean solar day is the key to providing that coherence. (True now on Mars as well as Earth.) The mean solar day is just the sidereal day plus the synodic correction for lapping the sun once a year. The mean solar day is a global phenomenon. The eccentricity of the Earth's orbit and the tilt of its axis (etc) add periodic terms that average out. Latitude and politics overlay local variations that are a distraction from the central issue. Tidal slowing, on the other hand, represents a global long term secular trend. A trend with global implications demands a global solution. The trend just happens to be slow enough to permit cheating. Consensus based planning is necessary *especially* if we decide to cheat. Cheating is ultimately fruitless over the long term, no matter what. The ITU has a responsibility to consider options with a long term future. A permanent embargo on leap seconds does not have one. Whatever action the ITU takes, it should be fully and carefully planned and not obligate our descendants to clean up an embarrassing mess. Only one - standard time based on mean solar time - has ever been shown to be *practically* workable. Two: standard time plus daylight saving time is the other DST is a trivial gimmick layered on standard time. Standard time is a global system layered on the mean solar day. Ideally we will come out of this exercise with an improvement to standard timekeeping. Wouldn't it be more fun to pursue that project rather than playing an endless game of whack-a-mole with ITU politics? Rob ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] civil-solar correlation with TI
Rob Seaman wrote: Again, the issue is mean solar time, not local solar time. This sentence doesn't make sense to me. You seem to have a different definition of either mean or local from me. To be clear: the (periodic) difference between apparent and mean solar time does not affect my argument, so I ignored it; likewise, the difference between solar time at one's actual longitude (local solar time) and solar time at a nearby round-numbered longitude (standard time) is small and does not affect the psychology. it is a question of discovering requirements implicit in our society. Good point. Historians looking backward want to relate events worldwide and arrange them into coherent timelines. Yes, they'll want the Olson database. Whatever the preferences of the ITU, they will discover that it is simply unacceptable to allow local dates to vary secularly from civil timekeeping dates. I don't see how this follows. Given the Olson database they'll be able to apply the offsets correctly. If the date drift per se really is a problem, that would be a reason to argue for the IDL-jumping version of my scenario, rather than the unbounded-timezone-offset version. -zefram ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
[LEAPSECS] Fwd: Re: Leap second is back
List members might be interested in the message below posted to the Sundial List--yes, some of us are interested in these devices that provide true time ;-). Not that this posting will likely sway current diverse and seemingly entrenched opinions of some members (one way or the other). By the way, I must confess, that reading some of the postings reminds me of the Dilbert cartoon strip at times. ;-) Anyway, happy holidays to all. -- Richard Langley Links to The Times items: http://www.timesonline.co.uk/tol/comment/leading_article/article5361349.ece http://www.timesonline.co.uk/tol/comment/letters/article5385619.ece http://www.timesonline.co.uk/tol/news/uk/science/article5361670.ece http://www.timesonline.co.uk/tol/comment/letters/article5372021.ece http://www.timesonline.co.uk/tol/news/uk/science/article5361935.ece - Forwarded message from Frank King frank.k...@cl.cam.ac.uk - Date: Sat, 27 Dec 2008 09:15:30 + From: Frank King frank.k...@cl.cam.ac.uk Reply-To: Frank King frank.k...@cl.cam.ac.uk Subject: Re: Leap second is back To: Sundial List sund...@uni-koeln.de Dear All, On 9 December, Fred Sawyer reminded us that there will be a leap second at the end of this month. He suggested that the proposal to eliminate Leap Seconds has not been adopted. It is true that this proposal has not yet been adopted but the proposal has certainly not been abandoned. There was a worrying report in the London Times newspaper of 18 December noting that the ITU is still keen to get rid of Leap Seconds. The Times also printed a defence of the Leap Second by David Rooney (Curator of timekeeping at the Royal Greenwich Observatory) and a further defence by my colleague Markus Kuhn (whose office is next to mine!). I mentioned the report to my friend John Chambers who was Head of the UK Time Service from 1993 to 1996 and prompted him to write a letter to the Times giving his views. His letter, as published, can be found at: http://www.timesonline.co.uk/tol/comment/letters/article5385619.ece His letter, as sent (before the Letters Editor got hold of it!), can be found below my signature. Very diplomatically, he notes that it really is no business of the ITU to mess about with Civil Time. Unfortunately, the published version leaves out John's note about sundials. [Do Times readers have no interest in these instruments?] Equally unfortunately, the published version leaves out the important comment that those who want an unchanging timescale can use GPS time. Moreover, GPS time is provided free! Best wishes Frank King Cambridge, UK Original Letter about Leap Seconds as sent to the Times Letters to the Editor, The Times - [This letter is sent exclusively to The Times] Sir, Any intention to interfere with the current worldwide arrangements for civil time by minutes, or even hours (third leader and report (page 8) December 18, letters December 19, 20) are surely beyond the competence of the International Telecommunications Union (ITU). The ITU's scope extends only to time signals as broadcast. Reform of civil time is as important as calendar reform, where the ramifications of the Vatican initiative in 1582 took hundreds of years to settle. Coordinated Universal Time (UTC) is a compromise which has served us well since 1972 as the basis for time zones. It provides a timescale within one second of mean solar time for everyday use. It has seconds markers coincident with the more regular atomic timescale used, for example, in GPS and deep-space navigation. The two are simply related: GPS time is 14s ahead of UTC until after the leap second at the end of this month, then it will be 15s ahead. Sundials are used worldwide to tell the time, requiring neither fuel nor moving parts. Some can be read to an accuracy of better than a minute. Traditional navigation, based on observation of sun and stars, loses less than 400 metres in accuracy when UTC is used. However much train time- keeping improves we can live within these limits in everyday life. Those who need to live a precise life, or whose systems depend on there being 60 seconds in every minute, can already use GPS time. There is no need for another time scale. (Mr) John Chambers (Head of UK Time Service 1993-96) Koskenpääntie 79, 42300 Jämsänkoski, Finland --- https://lists.uni-koeln.de/mailman/listinfo/sundial - End forwarded message - === Richard B. LangleyE-mail: l...@unb.ca Geodetic Research Laboratory Web: http://www.unb.ca/GGE/ Dept. of Geodesy and Geomatics EngineeringPhone:+1 506 453-5142 University of New Brunswick Fax: +1 506 453-4943 Fredericton, N.B., Canada E3B 5A3 Fredericton? Where's that? See: http://www.city.fredericton.nb.ca/
Re: [LEAPSECS] civil-solar correlation with TI
I wrote: Historians looking backward want to relate events worldwide and arrange them into coherent timelines. Zefram replied: Yes, they'll want the Olson database. Precisely. For a scheme such as this to have any chance of working, a requirement is that it be tightly coupled to a mechanism like zoneinfo. This is equivalent to Steve Allen's proposal. Whatever the preferences of the ITU, they will discover that it is simply unacceptable to allow local dates to vary secularly from civil timekeeping dates. I don't see how this follows. Given the Olson database they'll be able to apply the offsets correctly. A further requirement is that there needs to be faith in that database and in how it is tied into the fabric (system of systems) of the world. If the date drift per se really is a problem, that would be a reason to argue for the IDL-jumping version of my scenario, rather than the unbounded-timezone-offset version. Words like jumping and unbounded reflect that the discontinuities represented by leap seconds remain inherent in the system. One way or another, intercalary corrections (of whatever sort) will remain necessary. Since they are necessary, so is a coherent and reliable mechanism for managing them. The devil-may-care ITU proposal is insufficient. Rob ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] Cheating means more planning, not less
On Sat, 27 Dec 2008, Rob Seaman wrote: Rather, a clock can be deposited at any meridian on any planet, set to any time, running at any rate. The question is whether a particular choice of parameters is useful and sustainable. Really what it boils down to is a question of how frequently and by how much we reset our clocks so that civil time (the time used for every-day purposes) has a useful relation to Earth orientation. Additionally if a planet has populations scattered at wide longitudes, the more basic requirement is to organize a coherent system to manage the whole. That's just a matter of quantizing timezone offsets with a reasonably large granularity, as was established in the 19th century. Only one - standard time based on mean solar time - has ever been shown to be *practically* workable. Two: standard time plus daylight saving time is the other DST is a trivial gimmick layered on standard time. Standard time is a global system layered on the mean solar day. I don't think DST is trivial, nor is it a gimmick. It's very tempting to dismiss DST as a stupidity, especially if you try to understand it without regard to the sociology of time. (I used to think so myself.) There is a very good reason for DST and it is entirely to do with the way people collectively relate to clocks. The most obvious artefacts of this relationship are timetables. Ben Franklin's article was satire, but like all good satire it was pointing out an important failure of civic life: that we are too strictly governed by clocks, regardless of how well we use natural daylight. Back when Franklin was writing, relatively few people lived in cities, and timetables were rare - even ideas like opening hours or working hours. But urban living naturally generates timetables: the timing of deliveries of goods from the counryside determines the opening times of the markets, which determines shopping hours, etc. There is an inevitable coupling of the timing of activities between different walks of life. This became painfully obvious in the USA when (over a period of decades) various jurisdictions disagreed about when and where DST should be applied. The worst chaos occurred when physically overlapping jurisdictions used different rules, so different offices in the same city (e.g. government vs. private) would be operating on different time. The chaos only subsided when the US federal government set rules for how DST should be applied, thereby establishing a consensus. What DST teaches us is that the the most important property that civil time must have is consensus over large areas, whether or not this makes sense w.r.t. natural philosophy. DST is a violation of the concept of standard time, but it is more useful to society than strict adherence to a fixed offset from mean solar time. In fact the same lesson is taught by the establishment of GMT as legal time across Britain. Legal precedent said GMT is a violation of local time - despite the fact that nobody in practice behaved as the law said they should, between the establishment of railway time and the endorsement of GMT as legal time. So how is this relevant to leap seconds? Firstly: The history shows that almost any violence can be done to civil time so long as everyone agrees to it. DST shows that sociology can trump astronomy. (Standard time shows the same thing, but DST's arbitrariness makes this fact much more starkly clear.) Broad agreement and consensus is the foundation of civil time. The way that leap seconds work clearly does not have enough consensus, in that people still produce software and standards and specifications that are incompatible with leap seconds. That fact is probably enough to doom them, just like Britain's local time law was doomed to lose to GMT in the 19th century. Secondly: The commonality between DST and UTC is that both of them require us to reset our clocks occasionally to keep them in a convenient relation to the position of the Earth. DST's resets exist because the way we coordinate our activities using timetables (aligned to mean solar time) doesn't work well with the hours of daylight. UTC's resets exist to keep our clocks matched to mean solar time. Can we not accomplish both goals with the same occasional resets, instead of having two independent reset schedules? Would this also solve the problem of leap seconds disagreeing with the practical consensus model of time? Is there any other way of cleaning up this mess? My sunrise time suggestion is not entirely a joke. Originally its serious purpose was to point out that there is a rational basis for DST: our timetables work better if they are anchored to sunrise than to midday. The point of my recent post is that if you are resetting clocks frequently to make gross adjustments, then you do not also need a second reset schedule to make fine adjustments. Sunrise time has layers of satire and absurdity, as well as of astronomy and sociology, but to explain them all
Re: [LEAPSECS] civil-solar correlation with TI
In message: 20081227134333.gm2...@fysh.org Zefram zef...@fysh.org writes: : Historians looking backward : want to relate events worldwide and arrange them into coherent : timelines. : : Yes, they'll want the Olson database. How is the Olson database fundamentally different than the historical data that a future historian would have based on the measurements of the delta between what we call today TAI and UT1 times? It is just more data for them to swizzle into their calculations? Warner ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] Cheating means more planning, not less
In message: 5de48b7a-0d30-4580-b110-7687a75a2...@noao.edu Rob Seaman sea...@noao.edu writes: : Identifying the length of the civil day with the length of the mean : solar day is the key to providing that coherence. (True now on Mars : as well as Earth.) The mean solar day is just the sidereal day plus : the synodic correction for lapping the sun once a year. The mean : solar day is a global phenomenon. The eccentricity of the Earth's : orbit and the tilt of its axis (etc) add periodic terms that average : out. Latitude and politics overlay local variations that are a : distraction from the central issue. Tidal slowing, on the other hand, : represents a global long term secular trend. A trend with global : implications demands a global solution. Correct. However, the die was cast on this in 1958 when the second was defined in terms of atomic behavior. At that point, the game was up, since the basic unit of time was decoupled from the day. We transitioned from having rubber seconds, to having rubber days. I suppose we could push this back further when the second was defined in terms of the mean solar day in 1900, since that changed a division of a day, to the day being so many seconds. A subtle difference that appears to have been lost on the people taking this first step, at least at the time. : The trend just happens to be slow enough to permit cheating. : Consensus based planning is necessary *especially* if we decide to : cheat. Cheating is ultimately fruitless over the long term, no matter : what. Yes. First, people cheated with rubber seconds (and why not, since that's how people cheated before the fixing of the length of the second based on atomic behavior: seconds were always rubber since they were defined in terms of a day that varied in length). Doing this similar cheating with atomic clocks presented many operational problems... Second, people cheated with leap seconds. This cheat has presented many operational problems. : The ITU has a responsibility to consider options with a long term : future. A permanent embargo on leap seconds does not have one. : Whatever action the ITU takes, it should be fully and carefully : planned and not obligate our descendants to clean up an embarrassing : mess. This is both true and false. Assuming, for the sake of argument, that we take the position that the ITU has to have a permanent solution to the clock skew problem, that cannot involve leap seconds. In time, they will be needed more than twice a year, then more than 12x a year, and finally, more than once a day. UTC, as defined today, dies once the length of day is 86401 seconds[*]. With these long-term problems on the horizon, I agree that some solution is needed. A leap second embargo is one radical idea don't sync the clocks: publish the delta. The psychological aspects of this are nice, since time won't drift more than a few minutes in anybody's lifetime for several dozen generations yet. This is as long term as other 'permanent' solutions the ITU has promulgated. So I'm not sure I understand this criticism. : Only one - standard time based on mean solar time - has ever been : shown to be *practically* workable. : : Two: standard time plus daylight saving time is the other : : DST is a trivial gimmick layered on standard time. Standard time is a : global system layered on the mean solar day. But UTC isn't layered on top of the mean solar day. It is merely synchronized to the mean solar day. It is based on the atomic second. And many legal times are being transitioned to UTC. There is a subtle difference between your statement and mine, but an important one. : Ideally we will come out of this exercise with an improvement to : standard timekeeping. Wouldn't it be more fun to pursue that project : rather than playing an endless game of whack-a-mole with ITU politics? Warner [*] Well, it would fail when the day was ~86400.033s since that's when we'd cross the once a month threshold for when the leap seconds can happen. When it crosses 86401, though, we're no longer able to use the same notation we're using today with 23:59:60 although I suppose it could be extended to any hour, then any minute, etc. At some point it becomes totally unworkable, and I arbitrarily selected once a day although my hunch is that it is somewhat before then. ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] Cheating means more planning, not less
On Sat 2008-12-27T19:22:00 -0700, M. Warner Losh hath writ: Correct. However, the die was cast on this in 1958 when the second was defined in terms of atomic behavior. At that point, the game was up, since the basic unit of time was decoupled from the day. We transitioned from having rubber seconds, to having rubber days. I suppose we could push this back further when the second was defined in terms of the mean solar day in 1900, since that changed a division of a day, to the day being so many seconds. A subtle difference that appears to have been lost on the people taking this first step, at least at the time. The cesium chronometer was created in the UK 1955, and within only a few months Markowitz of the USNO was rushing to start comparing it with the lunar observations of the dual rate moon camera, and the results of that intercomparison were reported before the experiment was really over. Markowitz in his role as chair of IAU 31 was in a tremendous race to see that the cesium would be calibrated with ephemeris time. There was barely enough time to reduce the observations they had made let alone to comprehend their meaning for either the short term or long term. During that experiment they noted that the rate of earth rotation was in a particularly fast phase of variation. I believe there is a memoir by Markowitz where he indicated the pressure he felt he was under to get an astronomically based definition before the physicists simply chose a number. I haven't yet seen it, and I can't cite it off the top of my head. I have seen no references which indicate that anyone had then recognized that ephemeris time was roughly in agreement with the mean solar day of 1820. There are a number of places where astronomers incorrectly stated that ephemeris time matched the mean solar day of 1900. -- Steve Allen s...@ucolick.orgWGS-84 (GPS) UCO/Lick ObservatoryNatural Sciences II, Room 165Lat +36.99855 University of CaliforniaVoice: +1 831 459 3046 Lng -122.06015 Santa Cruz, CA 95064http://www.ucolick.org/~sla/ Hgt +250 m ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
Re: [LEAPSECS] civil-solar correlation with TI
M. Warner Losh wrote: How is the Olson database fundamentally different than the historical data that a future historian would have based on the measurements of the delta between what we call today TAI and UT1 times? It is just more data for them to swizzle into their calculations? Because a mean solar clock is automatically a stable subdivision of the calendar - stable over long periods of time as well as geographically. Noon on two different days is separated by an integral number of days no matter what period of time separates the two dates and how the length of day may have varied in the interim. There is no swizzling needed if civil timekeeping remains tied to the Sun. Rob ___ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
