Re: The opportunity of leap seconds

2006-01-08 Thread Peter Bunclark
On Sat, 7 Jan 2006, Poul-Henning Kamp wrote: What Astronomers use UTC for, in your own many times repeated words, is a convenient approximation of UT1, and consequently it follows that if instead of an approximation astronomers used the Real Thing, leap seconds could harmlessly be removed

Re: The real problem with leap seconds

2006-01-08 Thread Ed Davies
Wow, things have got really stirred up around here. Lots of interesting points but I'll just concentrate on one... Poul-Henning Kamp wrote: Well, the BIPM doesn't really want anybody to use TAI, their director said as much last year, and I can see where he is coming from on that one. Since

Re: The real problem with leap seconds

2006-01-08 Thread Poul-Henning Kamp
In message [EMAIL PROTECTED], Ed Davies writes: Wow, things have got really stirred up around here. Lots of interesting points but I'll just concentrate on one... Poul-Henning Kamp wrote: Well, the BIPM doesn't really want anybody to use TAI, their director said as much last year, and I can

Re: The opportunity of leap seconds

2006-01-08 Thread Steve Allen
On Sun 2006-01-08T12:41:21 +0100, Poul-Henning Kamp hath writ: It sounds to me like BIPM ought to make an Internet service available which will deliver UT1 to astronomers in a timely fashion ? That would have to be the IERS. Something as simple as finger [EMAIL PROTECTED] Or even

Re: predicting leap seconds

2006-01-08 Thread Rob Seaman
On Jan 7, 2006, at 11:01 PM, M. Warner Losh wrote: This would phase in the predictive timeline for leap second insertions, and would also give the IERS control to end the experiment if the time horizons exceeded their ability to predict with confidence. it would also be completely within the

Re: The opportunity of leap seconds

2006-01-08 Thread Rob Seaman
On Jan 8, 2006, at 4:41 AM, Poul-Henning Kamp wrote: It sounds to me like BIPM ought to make an Internet service available which will deliver UT1 to astronomers in a timely fashion ? Not sure BIPM is necessarily the appropriate agent, but otherwise agree 100%. Perhaps we should seek other

Re: The real problem with leap seconds

2006-01-08 Thread Rob Seaman
On Jan 8, 2006, at 5:38 AM, Poul-Henning Kamp wrote: As I understood it, it was mainly that TAI is a post-factum postal timescale. One is left pondering the fact that UTC is now (and would remain under any changes I've heard suggested) a time scale based on TAI. What magic makes one

Re: The opportunity of leap seconds

2006-01-08 Thread Poul-Henning Kamp
In message [EMAIL PROTECTED], Steve Allen writes: Something as simple as finger [EMAIL PROTECTED] Or even just a more stringent formatting of the bulletins on the ftp site could do it as well. I do not believe that any of the IERS bureaus have internet connections and servers which

Re: The real problem with leap seconds

2006-01-08 Thread Poul-Henning Kamp
In message [EMAIL PROTECTED], Steve Allen writes: On Sat 2006-01-07T21:20:33 +0100, Poul-Henning Kamp hath writ: Well, the BIPM doesn't really want anybody to use TAI, their director said as much last year The Italian contribution to the November 2005 WP7A meeting could be interpreted a

Re: The real problem with leap seconds

2006-01-08 Thread Poul-Henning Kamp
In message [EMAIL PROTECTED], Rob Seaman writes: On Jan 8, 2006, at 5:38 AM, Poul-Henning Kamp wrote: As I understood it, it was mainly that TAI is a post-factum postal timescale. One is left pondering the fact that UTC is now (and would remain under any changes I've heard suggested) a time

Re: The opportunity of leap seconds

2006-01-08 Thread Poul-Henning Kamp
In message [EMAIL PROTECTED], Peter Bunclark writes: On Sun, 8 Jan 2006, Poul-Henning Kamp wrote: finger [EMAIL PROTECTED] You mean [EMAIL PROTECTED] That would be quiet useful. Otherwise let's not bother with NTP protocol, just [EMAIL PROTECTED] I don't really care what the service is

interoperability

2006-01-08 Thread Rob Seaman
On Jan 8, 2006, at 9:09 AM, Poul-Henning Kamp wrote: Doing so would once and for all have to divorce earth orientation from that unified time scale, leaving it to governments to align civil time with daylight as they see fit (just like today). Without further debating the meaning of civil

Re: The real problem with leap seconds

2006-01-08 Thread M. Warner Losh
In message: [EMAIL PROTECTED] Poul-Henning Kamp [EMAIL PROTECTED] writes: : In message [EMAIL PROTECTED], Ed Davies writes: : Wow, things have got really stirred up around here. Lots of interesting : points but I'll just concentrate on one... : : Poul-Henning Kamp wrote: : Well, the

Re: interoperability

2006-01-08 Thread Poul-Henning Kamp
In message [EMAIL PROTECTED], Rob Seaman writes: On Jan 8, 2006, at 9:09 AM, Poul-Henning Kamp wrote: Doing so would once and for all have to divorce earth orientation from that unified time scale, leaving it to governments to align civil time with daylight as they see fit (just like today).

Re: The real problem with leap seconds

2006-01-08 Thread Steve Allen
On Sun 2006-01-08T11:44:04 -0700, M. Warner Losh hath writ: How is it that UTC can be realized in realtime, but TAI isn't. I thought the difference between the two was an integral number of seconds, by definition. Is that understanding flawed? I believe the claim would be that UTC(insert

Re: The opportunity of leap seconds

2006-01-08 Thread Tom Van Baak
Research-quality telescopes, in particular all the ones built in the last few decades on alt-azimuth mounts, do of course use UT1; a 0.9s error would be a complex ~10 arcsec error in both axes and give a quite useless pointing performance. However, UTC is often used as a UT1 delivery system;

Re: interoperability

2006-01-08 Thread Tom Van Baak
Without further debating the meaning of civil time, consider the implications of this two stage system. The first stage conveys TAI or something related to it by a constant offset. The second stage at any location (correct me if I misunderstand you) would be a secondary clock disseminated

Re: interoperability

2006-01-08 Thread Rob Seaman
On Jan 8, 2006, at 4:04 PM, Tom Van Baak wrote: You cannot divide timekeeping, time dissemination, into neat stages. Again. My point is strengthened. This being the case, a requirement on one flavor of time transfers to others. We will not solve the problem of creeping complexity and

Re: interoperability

2006-01-08 Thread Daniel R. Tobias
On 8 Jan 2006 at 15:04, Tom Van Baak wrote: You cannot divide timekeeping, time dissemination, into neat stages. In the 1960s if ten labs were told to offset their phase or frequency it affected only a handful of people or systems. Today when IERS announces a leap second, millions of

Re: interoperability

2006-01-08 Thread Tom Van Baak
You cannot divide timekeeping, time dissemination, into neat stages. In the 1960s if ten labs were told to offset their phase or frequency it affected only a handful of people or systems. Today when IERS announces a leap second, millions of machines, systems, and people are affected.

Re: interoperability

2006-01-08 Thread Rob Seaman
On Jan 8, 2006, at 6:41 PM, Tom Van Baak wrote: am not sure I like the idea that eventually my car, traffic lights, airlines, television, and my thermostat will have to be reliably tied to the IERS in order to function properly. This is a general issue with the increasingly tight coupling

Re: interoperability

2006-01-08 Thread John Cowan
Rob Seaman scripsit: The question is: how precisely does this differ from the situation now or in the past? Whether by fiat or not, some common worldwide stage two clock must exist. Again, no it doesn't need to exist. We need a uniform time scale like TAI. And we need local civil time for

Re: interoperability

2006-01-08 Thread Poul-Henning Kamp
In message [EMAIL PROTECTED], Rob Seaman writes: Sensibly designed operating systems keep time in the form of the first stage clock, Perhaps. We have no examples of this. Stage one would be TAI. As we have just been reminded, TAI is not ready for prime time. Stop. You yourself defined

Re: interoperability

2006-01-08 Thread John Cowan
Rob Seaman scripsit: Sure, and you can timestamp then on either timescale, because there is a 1 to 1 translation between the two timescales [1]. Perhaps I miss your meaning here, too. The event of migrating a time zone is a discontinuity just as with a leap second or leap hour. Sure. But

Re: interoperability

2006-01-08 Thread John Cowan
Poul-Henning Kamp scripsit: Windows have got it right now I belive, but it used to be that a file created and transmitted from Denmark at the end of the business day would be older than a file created at the start of business day in California, despite a strict ordering of the events. It's

Re: interoperability

2006-01-08 Thread Poul-Henning Kamp
In message [EMAIL PROTECTED], Rob Seaman writes: As I pointed out close to five years ago, the ultimate long term remediation will likely involve redefining the length of the second: Rob, I think this shows how little you understand of the entire thing. Several SI units are defined relative

Re: interoperability

2006-01-08 Thread Rob Seaman
On Jan 9, 2006, at 12:03 AM, John Cowan wrote: Each locality decides when and how to adjust both its offset from TAI and its seasonal transition function (if any), just as it does today. Not just as today, see intervening messages. What we abandon is a universal time tightly synchronized to

Re: interoperability

2006-01-08 Thread M. Warner Losh
In message: [EMAIL PROTECTED] John Cowan [EMAIL PROTECTED] writes: : But how in practice is it envisaged that a scheme : for migrating time zones versus TAI would work, precisely? : : Straightforwardly. Each locality decides when and how to adjust both : its offset from TAI and its

Re: interoperability

2006-01-08 Thread Peter Bunclark
On Sun, 8 Jan 2006, Tom Van Baak wrote: between astronomical and atomic timescales. Could we rephrase that between geophysical and atomic timescales ? Astronomers measure it and have to compensate for it, not cause it. Reminds me bitterly of the widely reported loss of Mars Climate Orbiter