On Mon, Mar 20, 2023 at 2:46 PM Richard B Langley <l...@unb.ca> wrote:
> "I'd also note that if GLASNOS can't be fixed by 2035 ..." > > Interesting slip of the tongue. > > Glasnos[t] was taken to mean increased openness and transparency in > government institutions and activities in the Soviet Union (USSR). Glasnost > reflected a commitment of the Gorbachev administration to allowing Soviet > citizens to discuss publicly the problems of their system and potential > solutions. > > Of course, GLONASS was meant. But we are reminded that in today's Russia, > openness and transparency, not to mention freedom of speech, is a thing of > the past. > ah, yes. I lisned to too many Gorby speeches back in the day, eh? Thanks for the amusing correction... Warner > Sorry for being a bit off topic. > > -- Richard Langley > > > ----------------------------------------------------------------------------- > | Richard B. Langley E-mail: l...@unb.ca > | > | Geodetic Research Laboratory Web: http://gge.unb.ca > | > | Dept. of Geodesy and Geomatics Engineering Phone: +1 506 453-5142 > | > | University of New Brunswick > | > | Fredericton, N.B., Canada E3B 5A3 > | > | Fredericton? Where's that? See: http://www.fredericton.ca/ > | > > ----------------------------------------------------------------------------- > > ________________________________________ > From: LEAPSECS <leapsecs-boun...@leapsecond.com> on behalf of Warner Losh > <i...@bsdimp.com> > Sent: March 20, 2023 5:18 PM > To: Leap Second Discussion List > Subject: Re: [LEAPSECS] Inside GNSS published an update of my CGSIC talk > > ✉External message: Use caution. > > > On Mon, Mar 20, 2023 at 1:37 PM Michael Deckers via LEAPSECS < > leapsecs@leapsecond.com<mailto:leapsecs@leapsecond.com>> wrote: > > On 2023-03-20 07:54, Jürgen Appel via LEAPSECS wrote: > > > > In your Conclusion, you say "the CGPM resolution also stipulates that no > > change to current practices can occur before 2035." > > > > This is not how I read read the CGPM document on the BIPM website: > > "The General Conference on Weights and Measures (CGPM), at its 27th > meeting > > [...] decides that the maximum value for the difference (UT1-UTC) will be > > increased in, or before, 2035," > > > > So in case the negative leap seconds become a real threat, according to > my > > interpretation is is an option to increase the tolerance value earlier > than > > 2035 to avoid trying out negative leap seconds a last and first time. > > > > Can someone confirm my view? > > > > You read correctly, the French (official) version has > > ..."décide que la valeur maximale pour la différence > (UT1 - UTC) sera augmentée au plus tard en 2035,".... > > which means "in 2035 at the latest". > > Note also that the definition of UTC as approved by the > CGPM never mentions _any_ explict bound for |UT1 - UTC|; it > only says that (TAI - UTC) is an integral multiple of 1 s > as determined by the IERS. It is the IERS who state that > > "Coordinated Universal Time (UTC) a measure of time > that conforms, within approximately 1 s, to the mean > diurnal motion of the Sun and serves as the basis of > all civil timekeeping." > > quoting the IAU "Nomenclature for Fundamental Astronomy (NFA)" > found at http://syrte.obspm.fr/iauWGnfa/NFA Glossary.html. > > This seems to be lenient enough to allow for not scheduling > a negative leap second even in the case that the difference > (UT1 - UTC) should go a bit below -1 s before 2035. > > So is "approximately" here to be read in the "astronomer" sense that it's > that, give or take an order of magnitude, or some more close reading :) For > astronomy, often times things that are approximately the same can vary > quite a bit, and that's fine. > > More seriously even 2s is approximately 1s if there's some kind of effort > to keep it from freewheeling to 10s, 100s, or 1000s of seconds. > > For example, the Gregorian calendar approximates the year over the > centuries, but any given year can deviate up to 2 days (worst case) from > the idealized solstice dates. > > I'd also note that if GLASNOS can't be fixed by 2035, then a fallback to a > schedule of leap seconds to keep the answer approximately 1s in the long > haul could also be on the table. Having it be scheduled, rather than > observational, has advantages: everybody gets leap years right, and will > for the next few hundred years (maybe with a glitch at 2100 and 2400). A > much lower percentage get leap seconds right because leap second knowledge > propagates imperfectly, even after all these years of trying (my first > anti-leapsecond screeds date back maybe 20 years). So my first choice is > always 'none, cope with shifting civil time on the scale of centuries' but > my second choice is 'schedule for the long-term average and don't worry > about going > 1s' . > > Warner > > Michael Deckers. > > _______________________________________________ > LEAPSECS mailing list > LEAPSECS@leapsecond.com<mailto:LEAPSECS@leapsecond.com> > https://pairlist6.pair.net/mailman/listinfo/leapsecs > _______________________________________________ > LEAPSECS mailing list > LEAPSECS@leapsecond.com > https://pairlist6.pair.net/mailman/listinfo/leapsecs >
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