Coordinated Universal Time (UTC) to retain “leap second”
http://www.itu.int/net/pressoffice/press_releases/2015/53.aspx -- Take care. Thanks, Brian Inglis, Calgary, Alberta, Canada
At least they seem to be deferring decision rather than actively deciding in favor of leap seconds. Still, is anyone actually advocating in favor of leap seconds? Who is being helped by keeping mean solar time at noon UTC or whatever the point of leap seconds is? On Thu, Nov 19, 2015 at 8:57 PM, Brian Inglis < Brian.Inglis@systematicsw.ab.ca> wrote:
http://www.itu.int/net/pressoffice/press_releases/2015/53.aspx -- Take care. Thanks, Brian Inglis, Calgary, Alberta, Canada
Outside of astronomical calculations, is there any relevance? Wouldn't it make more sense for the astronomers to adjust their calculations than for the whole world to adjust the clocks? Alas, it would probably be easier to convince the world to set their clocks by TAI than it would be to remove leap seconds from the definition of UTC. "Easier" being a relative term. From: paul@ganssle.io Date: Thu, 19 Nov 2015 22:15:49 -0500 To: Brian.Inglis@systematicsw.ab.ca CC: time-nuts@febo.com; tz@iana.org Subject: Re: [tz] Coordinated Universal Time (UTC) to retain “leap second” At least they seem to be deferring decision rather than actively deciding in favor of leap seconds. Still, is anyone actually advocating in favor of leap seconds? Who is being helped by keeping mean solar time at noon UTC or whatever the point of leap seconds is? On Thu, Nov 19, 2015 at 8:57 PM, Brian Inglis <Brian.Inglis@systematicsw.ab.ca> wrote: http://www.itu.int/net/pressoffice/press_releases/2015/53.aspx -- Take care. Thanks, Brian Inglis, Calgary, Alberta, Canada
On 2015-11-20, Paul Ganssle <paul@ganssle.io> wrote:
At least they seem to be deferring decision rather than actively deciding in favor of leap seconds. Still, is anyone actually advocating in favor of leap seconds? Who is being helped by keeping mean solar time at noon UTC or whatever the point of leap seconds is?
I got into an argument about this with ESR (in an NTPsec announcement thread on his blog) a few months ago and he said:
You think a timescale which is an integer number of seconds offset from TAI and which is within a second or so of London’s Mean Solar Time is wholly unnecessary. This demonstrates that you aren’t a marine navigator, an astronomer, or (where it bites especially hard) an aviator. It’s from these people that the real-world pushback against decoupling international standard time from mean solar is coming, and they have good reasons.
So, those people, I guess. It's still not entirely clear to me why they need civil time coupled to it, but there you go.
On Fri, Nov 20, 2015 at 12:16 AM, Random832 <random832@fastmail.com> wrote:
On 2015-11-20, Paul Ganssle <paul@ganssle.io> wrote:
At least they seem to be deferring decision rather than actively deciding in favor of leap seconds. Still, is anyone actually advocating in favor of leap seconds? Who is being helped by keeping mean solar time at noon UTC or whatever the point of leap seconds is?
I got into an argument about this with ESR (in an NTPsec announcement thread on his blog) a few months ago and he said:
You think a timescale which is an integer number of seconds offset from TAI and which is within a second or so of London’s Mean Solar Time is wholly unnecessary. This demonstrates that you aren’t a marine navigator, an astronomer, or (where it bites especially hard) an aviator. It’s from these people that the real-world pushback against decoupling international standard time from mean solar is coming, and they have good reasons.
So, those people, I guess. It's still not entirely clear to me why they need civil time coupled to it, but there you go.
The only reason (at least, until UT1-TAI builds up to 2 or 3 hours) is celestial navigation using civil time, which should be good to half a km or so just using UTC clock time. Note, by the way, that the Navy is worried about hacks to the navigation infrastructure sufficiently to make celestial mechanics a required course once again at the Naval Academy. http://www.latimes.com/nation/la-na-celestial-navigation-20151025-story.html Regards Marshall Eubanks
On 2015-11-20 00:50, Marshall Eubanks wrote:
On Fri, Nov 20, 2015 at 12:16 AM, Random832 <random832@fastmail.com <mailto:random832@fastmail.com>> wrote:
On 2015-11-20, Paul Ganssle <paul@ganssle.io <mailto:paul@ganssle.io>> wrote: > At least they seem to be deferring decision rather than > actively deciding in favor of leap seconds. Still, is anyone > actually advocating in favor of leap seconds? Who is being > helped by keeping mean solar time at noon UTC or whatever the > point of leap seconds is?
I got into an argument about this with ESR (in an NTPsec announcement thread on his blog) a few months ago and he said:
> You think a timescale which is an integer number of seconds > offset from TAI and which is within a second or so of London’s > Mean Solar Time is wholly unnecessary. This demonstrates that > you aren’t a marine navigator, an astronomer, or (where it > bites especially hard) an aviator. It’s from these people that > the real-world pushback against decoupling international > standard time from mean solar is coming, and they have good > reasons.
So, those people, I guess. It's still not entirely clear to me why they need civil time coupled to it, but there you go.
The only reason (at least, until UT1-TAI builds up to 2 or 3 hours) is celestial navigation using civil time, which should be good to half a km or so just using UTC clock time.
500m would miss a harbour entrance or runway and could land you on the rocks or fly you into a mountain. Nav, survey, timing software dealing with locations and times assumes an earth centered reference. Problems telecomms utilities have dealing with leap seconds seem pretty insignificant compared to impacts on legal, finance, and transportation standards, regulations, industries, cargo, and passengers. Also the judges, lawyers, politicians, financiers, and electorate in many jurisdictions expect time to be mean solar, delta political standard/daylight time offsets, and technical leap seconds, wherever it does not still explicitly mandate an offset to GMT (which still includes much of the Commonwealth, former colonies, and nations traditionally allied to the UK).
Note, by the way, that the Navy is worried about hacks to the navigation infrastructure sufficiently to make celestial mechanics a required course once again at the Naval Academy. http://www.latimes.com/nation/la-na-celestial-navigation-20151025-story.html Doh! Might be good to have some backup when ECM or a missile takes out your antennae, power, storage, ...! Navies should be run to expect to do more than just show the flag, launch planes/helos, or deliver marines.
-- Take care. Thanks, Brian Inglis, Calgary, Alberta, Canada
On Nov 20, 2015, at 12:16 AM, Random832 <random832@fastmail.com> wrote:
On 2015-11-20, Paul Ganssle <paul@ganssle.io> wrote: ...
You think a timescale which is an integer number of seconds offset from TAI and which is within a second or so of London’s Mean Solar Time is wholly unnecessary. This demonstrates that you aren’t a marine navigator, an astronomer, or (where it bites especially hard) an aviator. It’s from these people that the real-world pushback against decoupling international standard time from mean solar is coming, and they have good reasons.
I'm puzzled. Are there still marine navigators who have a sextant at hand, never mind know how to use one, let alone active use it? And celestial navigation in airplanes disappeared, what, 50 years ago? More? paul
Am 20.11.2015 16:53, schrieb Paul_Koning@dell.com:
On Nov 20, 2015, at 12:16 AM, Random832 <random832@fastmail.com> wrote:
On 2015-11-20, Paul Ganssle <paul@ganssle.io> wrote: ...
You think a timescale which is an integer number of seconds offset from TAI and which is within a second or so of London’s Mean Solar Time is wholly unnecessary. This demonstrates that you aren’t a marine navigator, an astronomer, or (where it bites especially hard) an aviator. It’s from these people that the real-world pushback against decoupling international standard time from mean solar is coming, and they have good reasons.
I'm puzzled. Are there still marine navigators who have a sextant at hand, never mind know how to use one, let alone active use it? And celestial navigation in airplanes disappeared, what, 50 years ago? More?
paul
The US Navy does: http://www.slate.com/blogs/future_tense/2015/10/19/u_s_naval_academy_reinsta... And based on the photo inside the article the russian do also re, wh
walter harms <wharms@bfs.de> wrote: |Am 20.11.2015 16:53, schrieb Paul_Koning@dell.com: |> I'm puzzled. Are there still marine navigators who have a sextant \ |> at hand, never mind know how to use one, let alone active use it? \ |> And celestial navigation in airplanes disappeared, what, 50 years a\ |> go? More? |The US Navy does: |http://www.slate.com/blogs/future_tense/2015/10/19/u_s_naval_academy_\ |reinstates_celestial_navigation_education.html | |And based on the photo inside the article the russian do also Not taking into account Polynesians which didn't need even that, not few people are afraid that western society would collapse uncontrollably because knowledge that has been acquired over milleniums has been carelessly forgotten in less than a century. I.e., i for one wouldn't survive without a supermarket, especially in winter. I know how to preserve fruit, but that is it. --steffen
This is why there is a leapsecs mailing list. Can we please not talk about this here? Thanks. p.s.: not necessary to talk about there, either. Just read the archives for the past few years. --jhawk@mit.edu John Hawkinson
John Hawkinson <jhawk@mit.edu> wrote: |This is why there is a leapsecs mailing list. |Can we please not talk about this here? Thanks. | |p.s.: not necessary to talk about there, either. Just read the archives |for the past few years. Oh. «Darkness falls across the land …». Sorry. (I really don't plan a self-resurrection; the picture of that super-scripted box-breaking-down link showed people giving a gift, most likely artistic artwork that hurt from the moneyside. On the other hand it is true; and, thus, things should be done to address it, just like the TZ DB anticipates in the future. IMHO. Not smart.) --steffen
On Nov 20, 2015, at 11:46 AM, walter harms <wharms@bfs.de> wrote:
Am 20.11.2015 16:53, schrieb Paul_Koning@dell.com:
...
I'm puzzled. Are there still marine navigators who have a sextant at hand, never mind know how to use one, let alone active use it? And celestial navigation in airplanes disappeared, what, 50 years ago? More?
paul
The US Navy does: http://www.slate.com/blogs/future_tense/2015/10/19/u_s_naval_academy_reinsta...
That's not what the article says. It says that the academy is doing a 3 hour intro on celestial navigation. That doesn't teach much more than "this technology exist and in decades past there were people who knew how to use it". Now, if they brought back the full course, and started putting sextants, chronometers, and nav tables on every navy ship, then I'd agree. paul
On Fri 2015-11-20T15:53:52 +0000, Paul_Koning@dell.com hath writ:
I'm puzzled. Are there still marine navigators who have a sextant at hand, never mind know how to use one, let alone active use it? And celestial navigation in airplanes disappeared, what, 50 years ago?
The celestial navigation relies on an almanac. If the almanacs were changed to tabulate according to "cesium atomic days" of SI seconds instead of "mean solar days" of earth rotation then everything would work. The tricky part is getting everyone to agree to that change. -- Steve Allen <sla@ucolick.org> WGS-84 (GPS) UCO/Lick Observatory--ISB Natural Sciences II, Room 165 Lat +36.99855 1156 High Street Voice: +1 831 459 3046 Lng -122.06015 Santa Cruz, CA 95064 http://www.ucolick.org/~sla/ Hgt +250 m
On Fri, Nov 20, 2015 at 12:35 PM, Steve Allen <sla@ucolick.org> wrote:
On Fri 2015-11-20T15:53:52 +0000, Paul_Koning@dell.com hath writ:
I'm puzzled. Are there still marine navigators who have a sextant at hand, never mind know how to use one, let alone active use it? And celestial navigation in airplanes disappeared, what, 50 years ago?
The celestial navigation relies on an almanac. If the almanacs were changed to tabulate according to "cesium atomic days" of SI seconds instead of "mean solar days" of earth rotation then everything would work. The tricky part is getting everyone to agree to that change.
No, that will not work. The UTC clock is providing not just the time, but also the rotation of the Earth (UT1). An atomic clock cannot do that (not at the km level), and the tables cannot provide leap seconds (much) in advance. You have a watch, radio, sextant. How do you find your position? Set your watch by the radio, listening to WWV or some other station. That time is in UTC, _which with leap seconds is an approximation to UT1, which cannot be predicted (at the second level) more than a year or two at a time_. Use the clock, tables and sextant to find your position. UTC was set up so that you can do this at the km level using a simple shortwave radio anywhere on Earth. Regards Marshall
-- Steve Allen <sla@ucolick.org> WGS-84 (GPS) UCO/Lick Observatory--ISB Natural Sciences II, Room 165 Lat +36.99855 1156 High Street Voice: +1 831 459 3046 Lng -122.06015 Santa Cruz, CA 95064 http://www.ucolick.org/~sla/ Hgt +250 m
On Fri 2015-11-20T12:55:49 -0500, Marshall Eubanks hath writ:
No, that will not work. The UTC clock is providing not just the time, but also the rotation of the Earth (UT1). An atomic clock cannot do that (not at the km level), and the tables cannot provide leap seconds (much) in advance.
The almanacs are tabulated only a couple of years in advance, and over that short an interval the current predictions of earth orientation have errors about the same as the typical human error using a sextant. Full precision already needs the DUT1 = UT1 - UTC, so if the radio broadcast time signals and almanacs could arrange to agree on a new time scale then a new difference value would preserve that ability. Full disclosure, Marshall and I worked across the building from each other using VLBI to measure earth orientation, so take this discussion as an example of why the ITU-R could not forge a working compromise. -- Steve Allen <sla@ucolick.org> WGS-84 (GPS) UCO/Lick Observatory--ISB Natural Sciences II, Room 165 Lat +36.99855 1156 High Street Voice: +1 831 459 3046 Lng -122.06015 Santa Cruz, CA 95064 http://www.ucolick.org/~sla/ Hgt +250 m
On Fri, Nov 20, 2015 at 1:12 PM, Steve Allen <sla@ucolick.org> wrote:
On Fri 2015-11-20T12:55:49 -0500, Marshall Eubanks hath writ:
No, that will not work. The UTC clock is providing not just the time, but also the rotation of the Earth (UT1). An atomic clock cannot do that (not at the km level), and the tables cannot provide leap seconds (much) in advance.
The almanacs are tabulated only a couple of years in advance, and over that short an interval the current predictions of earth orientation have errors about the same as the typical human error using a sextant.
The USNO's MICA runs up to 2050, but of course does not include future UT1 variations.
Full precision already needs the DUT1 = UT1 - UTC, so if the radio broadcast time signals and almanacs could arrange to agree on a new time scale then a new difference value would preserve that ability.
Well, you could get WWV to announce UT1 - UTC offsets :) But, then, you couldn't do celestial navigation off-shore with an FM or AM radio.
Full disclosure, Marshall and I worked across the building from each
other using VLBI to measure earth orientation, so take this discussion as an example of why the ITU-R could not forge a working compromise.
It does tend to give rise to discussion... Marshall
-- Steve Allen <sla@ucolick.org> WGS-84 (GPS) UCO/Lick Observatory--ISB Natural Sciences II, Room 165 Lat +36.99855 1156 High Street Voice: +1 831 459 3046 Lng -122.06015 Santa Cruz, CA 95064 http://www.ucolick.org/~sla/ Hgt +250 m
participants (10)
-
Brian Inglis -
John Hawkinson -
Marshall Eubanks -
Matt Johnson -
Paul Ganssle -
Paul_Koning＠dell.com -
Random832 -
Steffen Nurpmeso -
Steve Allen -
walter harms