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    Re: Leap seconds
    From: Fred Hebard
    Date: 2009 Jan 11, 13:02 -0500

    No need for this Greg.
    
    On Jan 11, 2009, at 12:23 PM, Greg R. wrote:
    
    >
    > Ignoring his usual pomposity (not to mention the unnecessary
    > verbosity and prolixity in this post), I take it that George agrees
    > substantially with what I originally posted (at least in principle,
    > if not necessarily with my particular choice of words).
    >
    > So thanks for finally agreeing with me, George - if only in your
    > usual oblique (and occasionally obtuse) manner. That wasn't so
    > hard, was it?
    >
    > --
    > GregR
    >
    >
    >
    > --- On Sat, 1/10/09, George Huxtable  wrote:
    >
    >> From: George Huxtable 
    >> Subject: [NavList 6976] Re: Leap seconds
    >> To: NavList@fer3.com
    >> Date: Saturday, January 10, 2009, 3:52 PM
    >> Referring, apparently,  to posting [6933] (with which I have
    >> no
    >> disagreement) from Gary LaPook, GregR has written-
    >>
    >>
    >> "George:
    >>
    >> Are you reading this? Because this is EXACTLY what I was
    >> referring to
    >> earlier (i.e. that whatever time scale we use as navigators
    >> is totally
    >> irrelevant - as long as we can correlate it to the time in
    >> an almanac, or
    >> whatever is used to obtain the date/time for a celestial
    >> event).
    >>
    >> I still don't know if you were being troll-ish earlier
    >> or honestly trying to
    >> contribute to the discussion, but at least I'm not the
    >> only one who
    >> understands the concept - however abstract it might be for
    >> some on the list
    >> to comprehend."
    >>
    >> =============================
    >>
    >> Coming from anyone else on this list, I would simply laugh
    >> off the personal
    >> comments in that posting, but GregR has a track record of
    >> repeated and
    >> unwarranted personal unpleasantness in some of his earlier
    >> contributions, so
    >> I am disinclined to treat such matters lightly, from him.
    >>
    >> If he can avoid getting overheated, and deal with any
    >> question on a straight
    >> factual basis, as I will do, we may be able to manage
    >> fruitful discussion
    >> between us. Otherwise, not.
    >>
    >> ============================
    >>
    >> To be honest, I'm not really sure what Greg is arguing
    >> about. He contends
    >> "that whatever time scale we use as navigators is
    >> totally irrelevant - as
    >> long as we can correlate it to the time in an almanac, or
    >> whatever is used
    >> to obtain the date/time for a celestial event"
    >>
    >> I might well agree, depending on what meaning we agree on
    >> for "correlate".
    >> If that includes adjusting for the number of leap seconds
    >> that would have
    >> occurred since the almanac was produced, which is what
    >> would need to happen
    >> if we adopted Atomic Time for our clocks, then GregR and I
    >> do not differ.
    >>
    >> I don't know how long in advance almanacs are
    >> calculated and printed, but
    >> let's say, for the purpose of argument, five years. So
    >> that means that the
    >> almanacs that we use today were produced in 2004. There was
    >> no way the
    >> compilers could predict, then, just how much the Earth
    >> would slow in the
    >> next 5 years. If we were to switch to Atomic Time, it would
    >> mean that before
    >> we could use any of the data in an almanac, we would need
    >> to discover how
    >> much the Earth's spin had diverged from its nominal
    >> rate in that interval,
    >> and allow for it by adjusting the reading of an accurate
    >> clock. That applies
    >> to predictions, not just of the Sun, but of any planet, and
    >> via GHA Aries,
    >> any star. Each one of us, individually, would have to work
    >> out our own
    >> correction, depending on the date of our almanac and the
    >> (unpredictable)
    >> adjustment that's called for. Instead of what happens
    >> now, when it's done
    >> automatically (within less than a second of error, anyway)
    >> for us all, by
    >> applying leap-seconds to everyone's clock.
    >>
    >> It's a matter of discussion whether Atomic Time or the
    >> present compromise of
    >> Leap-second-adjusted time is the most convenient way to
    >> work our clocks in
    >> the future. My personal opinion is that neither is, but a
    >> smoothly adjusted
    >> clock-rate, that corresponds as well as possible to the
    >> observed rotation of
    >> the Earth, would be more viable over the long run. But that
    >> isn't relevant
    >> to our present discussion.
    >>
    >> Let's take the chance, now, to clear up some loose ends
    >> from GregR's initial
    >> posting, [6805]. He had written "Besides, the almanacs
    >> have been on UT since
    >> when - mid 70s? (and thus pretty much
    >> "disconnected" from "sun time")."
    >> On
    >> the contrary, we have seen that almanacs are, indeed,
    >> closely connected with
    >> Sun Time, because UT is, within less than a second, by the
    >> operation of leap
    >> seconds. And I have asked him what it is that he reckons
    >> occurred in the
    >> mid-70s to change that situation, to which there has been
    >> no reply.
    >>
    >> George.
    >>
    >> contact George Huxtable, at  george{at}hux.me.uk
    >> or at +44 1865 820222 (from UK, 01865 820222)
    >> or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.
    >>
    >>
    >>
    >>
    >>
    >>
    >
    > >
    >
    
    
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