Re: [LEAPSECS] alternative to smearing

Preben Nrager said: > Let's say Newcomb envisions negative JDs, and astronomy thus uses the JD > system. Astronomy then have two different "eternal" timescales, with two > different starting points for zero: The one is the proleptic gregorian > calendar, represented by ISO 8601, with the starting y

Re: [LEAPSECS] alternative to smearing

Preben Norager wrote: >Astronomy then have two different "eternal" timescales, with two >different starting points for zero: Many more than two. MJD, TJD, and the Julian epoch, for example, all have some currency in astronomy, and each have their own zero point. ("Julian epoch" is a somew

Re: [LEAPSECS] alternative to smearing

Zefram wrote: > ("Julian epoch" is a somewhat confusing term: it refers to a linear > count similar to JD, but scaled by a factor of 365.25 such that over the > long term it is frequency locked to the years of the Julian calendar, > and with zero point chosen such that Julian epoch roughly matche

Re: [LEAPSECS] alternative to smearing

Tony Finch said: > It's also worth remembering that with Old Style dates the year started on > the 25th March. It's very easy to be accidentally anachronistic :-) Sometimes and some places. This is why 1751 (not 1752) was the shortest ever year in England but not in Scotland. Wikipedia notes "At

[LEAPSECS] next leap second

John Sauter wrote: >While it is impossible to know for certain when the next leap second >will occur, I predict it will be December 31, 2022. I find that a surprising prediction. What is your basis for it? The extrapolating expression from the current Bulletin A

Re: [LEAPSECS] alternative to smearing

On Wed Jan 11 05:32:05 EST 2017, Clive D.W. Feather wrote: "Why [GDs]?" Because I want the proleptic gregorian calendar to represent Anno Domini. "Why [the zero point in time must be the same for both the daily, and the annual continuous timescale]?" I think there is something special about

Re: [LEAPSECS] alternative to smearing

Dear Zefram Please see my answer to Clive D.W. Feather at https://pairlist6.pair.net/pipermail/leapsecs/2017-January/006697.html I will not argue about what you have against my GDs. You are totally right in all you say. I can only say to you, as I said to Clive: "If you don't care about Chris

Re: [LEAPSECS] alternative to smearing

Preben Norager wrote: >I see the proleptic gregorian calendar, represented by ISO 8601, and the >GDs I propose, as a scientific way to settle the time of the incarnation. It doesn't do that. The birthdate of Jesus is a historical question, and (as I noted) historians are pretty sure that AD 0 isn

Re: [LEAPSECS] alternative to smearing

Having followed some of the arguments in this thread: For the very long time as the length of the day increases, leap seconds are imperative as they will become progressively more common and archaelogists may curse those that don't use them. There might be a case for temporarily discontinuing

Re: [LEAPSECS] Compact encoding of the leap seconds list

Tony Finch wrote: > The plain text version is > > 6+6+12+12+12+12+12+12+12+18+12+12+24+30+24+12+18+12+12+18+18+18+84+36+42+36+18+5? I've changed the binary version to optimize for the common case of positive leap seconds some multiple of 6 months apart, which makes it possible to fit the list in

Re: [LEAPSECS] next leap second

On Wed, 2017-01-11 at 13:07 +, Zefram wrote: > John Sauter wrote: > > While it is impossible to know for certain when the next leap > > second > > will occur, I predict it will be December 31, 2022. > > I find that a surprising prediction.  What is your basis for it? > > The extrapolating exp

Re: [LEAPSECS] alternative to smearing

Just to clarify-- The changing length of the solar day affects the number of days in a year but not the actual length of the year. The earth is not near resonance with any other major solar system bodies so variations in the actual length of the year will be small and of long period. This remains

Re: [LEAPSECS] alternative to smearing

Kaye and Laby (Tables of Physical and Chemical Constants, 15th Ed., 1986, Longman - G.W.C. Kaye and T.H. Laby - ISBN 0-582-46354-8) states that the year for which a mean solar day is 86,400.003 SI seconds was circa 1984. According to the given long term rates of change and assuming that this da

Re: [LEAPSECS] alternative to smearing

I should add that as the universe is now considered to be expanding, that should have some interesting relativistic effects on time and its measurement in the long term On 11/01/2017 23:04, Robert Jones wrote: Kaye and Laby (Tables of Physical and Chemical Constants, 15th Ed., 1986, Longman

Re: [LEAPSECS] alternative to smearing

slight revision On 11/01/2017 23:16, Robert Jones wrote: I should add that as the universe is now considered to be expanding at an accelerated rate, that should have some interesting relativistic effects on time and its measurement in the long term On 11/01/2017 23:04, Robert Jones wrote:

Re: [LEAPSECS] next leap second

John Sauter wrote: >My second source is the estimates of delta T from Stephenson, Morrison >and Hohenkerk. I'd expect the IERS projections to be the more reliable over the next few years. The focus of Stephenson et al is the long term, and they use general-purpose curve fitting methods. The IERS

Re: [LEAPSECS] next leap second

On Wed, Jan 11, 2017 at 3:28 PM, Zefram wrote: > It would be nice to have more sophisticated projections from IERS more > than a year ahead. It would particularly help in evaluating the proposals > that have been made involving scheduling leap seconds further ahead. Especially if they had error