Re: Wall Street Journal Article
On Jul 31, 2005, at 12:19 AM, Poul-Henning Kamp wrote:The topic is: why do IT installations and manufacturers not test leap-seconds. The answer is: because it costs too much.Bull! They don't test against UTC (the full force of an international standard) because they are ignorant of the need to do so. One more time - the solution to ignorance is education, not dumbing down the curriculum. Leap seconds represent a real world constraint. The commercial world is expected to deal with other real world constraints. And, of course, there is the little matter that nobody has bothered to conduct a meaningful survey of the commercial communities no more than the technical communities. The fact that some may have ignored elementary real world tests doesn't imply that their competitors were so cavalier.We're all entitled to our own realities. Yours seem to not coincide with the IT industry to any great extent.George Orwell would be proud: the Sun is fantasy and the IT industry, reality.I don't hear the counter proposal from the astronomers to fix leap seconds.You don't perceive even the possibility of risks associated with disconnecting civil time from solar time - therefore such risks don't exist. You don't hear a counter proposal - therefore such proposals don't exist. Piaget tells us that children should achieve object permanence by the age of two.As Steve Allen says, leap seconds ain't broken. The current standard is viable for hundreds of years. Replacing it with another that guarantees a colossal headache on a similar time scale is daft. But if you want a counter proposal, see http://iraf.noao.edu/~seaman/leap, originally submitted to this list more than four years ago. The current standard is fine - the only problem is that we aren't taking full advantage of it. I'm sure the clever fellows currently wasting their time pushing the ITU proposal could come up with something better than my counter proposal. It sure would be more fun to seek a consensus for improving civil time, rather than continuing to pursue this one-dimensional failure of a debate - in a more and more public arena.Rob SeamanNational Optical Astronomy Observatory
Re: Wall Street Journal Article
On Jul 30, 2005, at 11:23 PM, Poul-Henning Kamp wrote: When you start out on a long march, you don't put a stone in your boot deliberately, and if one is there already, you take it out. Leapseconds is such a stone for real-world IT installations. No. Leap seconds are the real world. Your long march, like others before, is a retreat from reality. If I were a professional astronomer, I would be busy with all those things, but as it is, I have not a single computer anywere which will be negatively affected by missing leap seconds. A) Why do you believe that astronomers are not preparing for the worst - an unfunded, unnecessary, naive and senseless mandate that will likely cost us millions? B) You better hope you are right - a lack of imagination is poor protection. The short cut of eliminating leap seconds will introduce more risks than it will avoid. I thought I heard some astronomer say in this discussion that all applications which need proper timekeeping should use TAI ? Hearing voices again? There is no one single solution to all problems in time. There are many different time scales that are appropriate for different purposes. I would be just as upset if the time lords were attempting to subvert TAI - which, as a matter of fact, they are. If they want to celebrate TAI, simply base civil time directly on TAI, not some odd number of seconds difference that will forever confuse "users" (meaning anybody with a clock). At least now we get bulletins a couple of times per year that explicitly provide the formula for converting between civil time and TAI. Rob Seaman National Optical Astronomy Observatory
Re: Wall Street Journal Article
In message <[EMAIL PROTECTED]>, Steve Allen writes: >On Sun 2005-07-31T09:19:40 +0200, Poul-Henning Kamp hath writ: >> I don't hear the counter proposal from the astronomers to fix leap >> seconds. > >They're not broken. It was my distinct impression from reading http://www.ucolick.org/~sla/leapsecs/dutc.html that in a mere couple of thousand years, we will have more than 12 leap seconds a year. That sounds broken to me. If for some reason astronomers don't think that is broken, then I can't see the logic in claiming that a leap-hour 500 years down the road is broken. >All the surveys which were taken in the past six years indicate that >the majority of time users believe this to be the case. They also >indicate that there is no consensus about whether there needs to be a >change, let alone about what that change might be. Right, and that's why the major industrial states are not doing anything about global warming either: They're not sweating more than they used to. >> Is this discussion really just about astronomers trying to make >> sure this doesn't happen in their lifetime, and if not, why are >> there no counter proposals for a better solution ? > >When the Wall Street Journal reporter called them why did the >proponents of abolition either provide the same old and unjustified >explanations or avoid talking altogether? He didn't call me. -- 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: Wall Street Journal Article
On Sun 2005-07-31T09:19:40 +0200, Poul-Henning Kamp hath writ: > I don't hear the counter proposal from the astronomers to fix leap > seconds. They're not broken. All the surveys which were taken in the past six years indicate that the majority of time users believe this to be the case. They also indicate that there is no consensus about whether there needs to be a change, let alone about what that change might be. > Is this discussion really just about astronomers trying to make > sure this doesn't happen in their lifetime, and if not, why are > there no counter proposals for a better solution ? When the Wall Street Journal reporter called them why did the proponents of abolition either provide the same old and unjustified explanations or avoid talking altogether? The content of that front page story was vetted for over two weeks, and the words "secret" and "secrecy" survived the WSJ editorial process. Why would the proponents risk such a public result? -- Steve Allen <[EMAIL PROTECTED]> WGS-84 (GPS) UCO/Lick ObservatoryNatural Sciences II, Room 165 Lat +36.99858 University of CaliforniaVoice: +1 831 459 3046 Lng -122.06014 Santa Cruz, CA 95064http://www.ucolick.org/~sla/Hgt +250 m
Re: Wall Street Journal Article
In message <[EMAIL PROTECTED]>, Steve Allen writes: >On Sun 2005-07-31T08:23:30 +0200, Poul-Henning Kamp hath writ: >> No, they had everything to do with computers don't liking time to >> jump around. > >But the reality is that no computer system (or any system, for even >NIST and USNO don't know what the value of TAI and UTC is until next >month) can guarantee that it always knows what time it is. Non sequitur. The topic is: why do IT installations and manufacturers not test leap-seconds. The answer is: because it costs too much. >> When you start out on a long march, you don't put a stone in your >> boot deliberately, and if one is there already, you take it out. >> >> Leapseconds is such a stone for real-world IT installations. > >In this sense leap seconds give the system designer the opportunity >and incentive to face reality instead of ignoring it. Taking away >leap seconds will not fix this. We're all entitled to our own realities. Yours seem to not coincide with the IT industry to any great extent. >> I'm pointing out that UTC with leap seconds is unsafe at any speed. > >Presuming that the system clock is always right is delusional. Non sequitur again. >> It would have been much smarter to use TAI, wouldn't it ? I thought >> I heard some astronomer say in this discussion that all applications >> which need proper timekeeping should use TAI ? > >If "proper timekeeping" means time as defined by physics then: >All applications which need proper timekeeping in the reference frame >of the solar system should use TCB. >All applications which need proper timekeeping in the terrestrial >environment should use TCG. >All applications which need proper timekeeping on the surface of the >earth should use TT. >These are the recommendations from astronomers to everyone. > >But these are not practical time scales. [...] So why would astronomers be recommending them ? >> And if anything, if astronomers switched to TAI on 2008-01-01 they >> would not run into this problem in the future. > >TAI is a practical time scale, but its seconds are not of constant >length. [...] Considering that we're comparing to a timescale which would be off by an hour in 600 years, I think these effects can be ignored for now and astronomy could use TAI profitably. >> I think the sneakage happened in 1972 and we're trying to evict it. > >Leap seconds were proposed and instituted by the physicists who ran >the atomic clocks. They were opposed by many astronomers, but after >the shouting stopped (and in the proceedings of the IAU GAs it is >evident that there was shouting) the astronomers agreed that UTC as SI >seconds with leap seconds was the best option. But let me turn this around for a second: I don't hear the counter proposal from the astronomers to fix leap seconds. I hear whinage about leap hours (which might or might not happen, depending on what scientists in the next 500 years decide) but I don't hear anything about how to fix UTC when leapseconds no longer are able to cope with the rate of DUT1 change. Is this discussion really just about astronomers trying to make sure this doesn't happen in their lifetime, and if not, why are there no counter proposals for a better solution ? -- 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: Wall Street Journal Article
On Sun 2005-07-31T08:23:30 +0200, Poul-Henning Kamp hath writ: > No, they had everything to do with computers don't liking time to > jump around. But the reality is that no computer system (or any system, for even NIST and USNO don't know what the value of TAI and UTC is until next month) can guarantee that it always knows what time it is. If the system does not know what time it is (at boot time, or if the system does not have radio or network connectivity) then the system clock can be wrong. If the system clock can be wrong then the system either has to admit that it does not care that it is wrong or the system has to have procedures for correcting that wrongness. The system can correct the wrongness either by changing the length of seconds or by resetting (leaping) the system clock. > When you start out on a long march, you don't put a stone in your > boot deliberately, and if one is there already, you take it out. > > Leapseconds is such a stone for real-world IT installations. In this sense leap seconds give the system designer the opportunity and incentive to face reality instead of ignoring it. Taking away leap seconds will not fix this. > I'm pointing out that UTC with leap seconds is unsafe at any speed. Presuming that the system clock is always right is delusional. > It would have been much smarter to use TAI, wouldn't it ? I thought > I heard some astronomer say in this discussion that all applications > which need proper timekeeping should use TAI ? If "proper timekeeping" means time as defined by physics then: All applications which need proper timekeeping in the reference frame of the solar system should use TCB. All applications which need proper timekeeping in the terrestrial environment should use TCG. All applications which need proper timekeeping on the surface of the earth should use TT. These are the recommendations from astronomers to everyone. But these are not practical time scales. They are Platonic ideals. Some sort of conversion needs to be applied in order to compare them with practical time scales. The algorithms for that conversion are not trivial -- they involve complex numeric calculations. This is a fact of life that cannot be defined away. > And if anything, if astronomers switched to TAI on 2008-01-01 they > would not run into this problem in the future. TAI is a practical time scale, but its seconds are not of constant length. Even if TAI were the result of perfect atomic clocks, TAI currently ignores the diurnal GR effects of changing depth in the gravitational potentials of solar system objects. Someday TAI will have to incorporate those currently-too-subtle effects of the passage of proper time for every given clock. TAI is unarguably the best time scale for use in telecommunications, but that does not make it perfect. And even if TAI were perfect that does not make it the best time scale for civil time. > I think the sneakage happened in 1972 and we're trying to evict it. Leap seconds were proposed and instituted by the physicists who ran the atomic clocks. They were opposed by many astronomers, but after the shouting stopped (and in the proceedings of the IAU GAs it is evident that there was shouting) the astronomers agreed that UTC as SI seconds with leap seconds was the best option. -- Steve Allen <[EMAIL PROTECTED]> WGS-84 (GPS) UCO/Lick ObservatoryNatural Sciences II, Room 165 Lat +36.99858 University of CaliforniaVoice: +1 831 459 3046 Lng -122.06014 Santa Cruz, CA 95064http://www.ucolick.org/~sla/Hgt +250 m
