Re: Risks of change to UTC

2006-01-23 Thread David Malone
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

Re: Risks of change to UTC

2006-01-23 Thread Clive D.W. Feather
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

Re: Risks of change to UTC

2006-01-23 Thread Steve Allen
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

Re: Risks of change to UTC

2006-01-23 Thread John Cowan
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

Re: Risks of change to UTC

2006-01-22 Thread Michael Sokolov
John Cowan [EMAIL PROTECTED] wrote: Once we have accomplished the former [changing the basis of civil time], I don't give a hoot about the latter [hobbling UTC]. Keep UTC if you want. Then what are you doing here? Why don't you go to your elected representatives in whatever country you call

Re: Risks of change to UTC

2006-01-22 Thread Mark Calabretta
On Sat 2006/01/21 10:11:04 PDT, M. Warner Losh wrote in a message to: LEAPSECS@ROM.USNO.NAVY.MIL You really should read the archives of this list. We've been over this in great detail. TAI is specifically contraindicated as a time I don't think new contributors (or even old ones) should have

Re: Risks of change to UTC

2006-01-22 Thread Mark Calabretta
On Sat 2006/01/21 15:15:32 PDT, M. Warner Losh wrote in a message to: LEAPSECS@ROM.USNO.NAVY.MIL Somewhere around betwee 45,000-80,000 you'll need more than one leap second a day. You should recognize this as a reductio ad absurdum argument; at that time there will be 86401 SI seconds per day -

Re: Risks of change to UTC

2006-01-21 Thread James Maynard
M. Warner Losh wrote: UTC works for navigation, but leap seconds pose problems for other users of time. Stating absolutely that UTC is not broken ignores these other users. Those other uses, for whom leap seconds pose a problem, should be using a time scale that does not have leap seconds.

Re: Risks of change to UTC

2006-01-21 Thread M. Warner Losh
In message: [EMAIL PROTECTED] James Maynard [EMAIL PROTECTED] writes: : M. Warner Losh wrote: : UTC works for navigation, but leap seconds pose problems for other : users of time. Stating absolutely that UTC is not broken ignores : these other users. : : Those other uses, for whom

Re: Risks of change to UTC

2006-01-21 Thread Daniel R. Tobias
On 21 Jan 2006 at 10:11, M. Warner Losh wrote: I maintain that for human activity, there's no need for leap seconds at all. In each person's lifetime, the accumulated error is on the order of a few minutes. Over generations, the problems with noon drifting to 1pm can trivially be solved by

Re: Risks of change to UTC

2006-01-21 Thread M. Warner Losh
In message: [EMAIL PROTECTED] Daniel R. Tobias [EMAIL PROTECTED] writes: : On 21 Jan 2006 at 10:11, M. Warner Losh wrote: : : I maintain that for human activity, there's no need for leap seconds : at all. In each person's lifetime, the accumulated error is on the : order of a few

Re: Risks of change to UTC

2006-01-21 Thread Rob Seaman
On Jan 20, 2006, at 10:17 PM, M. Warner Losh wrote: Any watch that is smart enough to decode those signals would be smart enough to add this minor correction as well. A viable time scale could be constructed from any periodic (or near periodic) waveform - there's nothing magic about the tick,

Re: Risks of change to UTC

2006-01-21 Thread Rob Seaman
On Jan 21, 2006, at 12:03 AM, M. Warner Losh wrote: WWV and most of the world's time stations broadcast DUT1. I should have added in my last message that some change in the signal format would be necessary if the range of DUT1 exceeds 0.9s. Bearing in mind that the ITU proposal would cease

Re: Risks of change to UTC

2006-01-21 Thread Daniel R. Tobias
On 21 Jan 2006 at 15:15, M. Warner Losh wrote: For some perspective, we've been using UTC for only ~50 years and the gregorian calendar for only ~1500 years. I'd anticipate that something would need to be done about the slowing of the day well before 4300 years have passed. Actually, that's

Re: Risks of change to UTC

2006-01-21 Thread Rob Seaman
On Jan 21, 2006, at 10:11 AM, M. Warner Losh wrote: Over generations, the problems with noon drifting to 1pm can trivially be solved by moving the timezones that civilian time uses. Neither trivial or a solution - quadratic disaster still looms. Keeping universal time synchronized to an

Re: Risks of change to UTC

2006-01-20 Thread John Cowan
Rob Seaman scripsit: Only a minority (small minority, one would think) of systems currently include any DUT1 correction at all - although these will perhaps tend to be the most safety-critical applications. [...] That is, of course, one of the major issues for astronomers - we rely on UTC

Re: Risks of change to UTC

2006-01-20 Thread Neal McBurnett
On Fri, Jan 20, 2006 at 03:12:15PM -0500, John Cowan wrote: Rob Seaman scripsit: Only a minority (small minority, one would think) of systems currently include any DUT1 correction at all - although these will perhaps tend to be the most safety-critical applications. [...] That is, of

Re: Risks of change to UTC

2006-01-20 Thread James Maynard
In reply to Rob Seaman, John Cowan wrote: Seaman: [A]s clock time diverges further and further from solar time, more systems in more communities (transportation, GIS, innumerable scientific disciplines, what have you) would be revealed to need remediation. Cowan: Can you spell out some of

Re: Risks of change to UTC

2006-01-20 Thread M. Warner Losh
In message: [EMAIL PROTECTED] James Maynard [EMAIL PROTECTED] writes: : ones position using sight reduction tables. Today a mechanical watch or : chronometer, or a battery-powered wristwatch, can be set to UTC using : radio time signals. Then when power fails, the sailor still has a :

Re: Risks of change to UTC

2006-01-20 Thread John Cowan
Neal McBurnett scripsit: To sum it up, PLEASE don't fundamentally change the DEFINITION of UTC, or you risk whole new kinds of confusion. Hopefully by now the folks on this list that don't like leap seconds at least have agreed that any change should be to a new time scale like TI, and

Re: Risks of change to UTC

2006-01-20 Thread John Cowan
James Maynard scripsit: Small boats, sea water, and electrical systems don't mix very well. The damp, salty environment all too often leads to failures of a boat's electrical system. A prudent sailor should not rely for navigation only on electrically powered systems like GPS or loran. Your

Re: Risks of change to UTC

2006-01-20 Thread James Maynard
M. Warner Losh wrote: In message: [EMAIL PROTECTED] James Maynard [EMAIL PROTECTED] writes: : M. Warner Losh wrote: : In message: [EMAIL PROTECTED] : James Maynard [EMAIL PROTECTED] writes: : : ones position using sight reduction tables. Today a mechanical watch or :

Re: Risks of change to UTC

2006-01-20 Thread James Maynard
M. Warner Losh wrote: : If DUT1 is broadcast, then one can set the time keeping device to UT1 : by a means similar to setting it to UTC, even if DUT1 exceeds 0.9s : with a similar accuacy (or better). There's nothing that says a watch : has to display UTC to be set correctly. You seem to

Re: Risks of change to UTC

2006-01-20 Thread Brian Garrett
- Original Message - From: James Maynard [EMAIL PROTECTED] To: LEAPSECS@ROM.USNO.NAVY.MIL Sent: Friday, January 20, 2006 9:33 PM Subject: Re: [LEAPSECS] Risks of change to UTC M. Warner Losh wrote: In message: [EMAIL PROTECTED] James Maynard [EMAIL PROTECTED] writes

Re: Risks of change to UTC

2006-01-20 Thread M. Warner Losh
In message: [EMAIL PROTECTED] James Maynard [EMAIL PROTECTED] writes: : M. Warner Losh wrote: : : : If DUT1 is broadcast, then one can set the time keeping device to UT1 : : by a means similar to setting it to UTC, even if DUT1 exceeds 0.9s : : with a similar accuacy (or better).

Risks of change to UTC

2006-01-16 Thread Rob Seaman
On Jan 15, 2006, at 1:07 PM, John Cowan wrote: There are a lot of systems, it seems, that assume DUT1 is bounded by either 0.9s or 1s. If leap seconds are turned off, then I'd expect that these will break and be replaced by systems that assume DUT1 is unbounded. Ah. I see. You are focusing