[LEAPSECS] LEAPSECS Digest, Vol 45, Issue 11

[Finkleman, Dave]

Does someone capture and archive these amazing discussions?  Pardon
silly questions from a newcomer.

This kind of knowledgeable exchange is what the ITU is missing.  There
are sound technical reasons for retaining or dispensing with the leap
second.  They need to be exposed, and the proponent of each should
consider what others would have to do in order to accommodate an
alternative.  This discussion thread does that but only to a small
audience of geeks.  

To reveal my bias, if the situation is this arguable, why change
anything?  We conjecture that whatever the cost or inconvenience of
living with the leap second, the costs and difficulties of deprecating
the leap second might be greater.  It is most a matter of who pays the
bill.

Dave Finkleman
Senior Scientist
Center for Space Standards and Innovation
Analytical Graphics, Inc.
7150 Campus Drive
Colorado Springs, CO 80920
 
Phone:  719-510-8282 or 719-321-4780
Fax:  719-573-9079
 
Discover CSSI data downloads, technical webinars, publications, and
outreach events at www.CenterForSpace.com.
-----Original Message-----
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Subject: LEAPSECS Digest, Vol 45, Issue 11

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Today's Topics:

   1. Re: h2g2 (Nero Imhard)
   2. Re: LEAPSECS Digest, Vol 45, Issue 1 (Tony Finch)
   3. Re: LEAPSECS Digest, Vol 45, Issue 1 (Tony Finch)
   4. Re: h2g2 (M. Warner Losh)
   5. Re: h2g2 (Michael Sokolov)
   6. Re: h2g2 (Ian Batten)
   7. Re: LEAPSECS Digest, Vol 45, Issue 1 (Poul-Henning Kamp)
   8. Re: h2g2 (Paul Sheer)


----------------------------------------------------------------------

Message: 1
Date: Fri, 3 Sep 2010 19:37:37 +0200
From: Nero Imhard <nimh at pipe.nl>
Subject: Re: [LEAPSECS] h2g2
To: Leap Second Discussion List <leapsecs at leapsecond.com>
Message-ID: <67EFEC27-33C2-4D35-A48F-F7BE2ED7D846 at pipe.nl>
Content-Type: text/plain; charset=us-ascii


On 2010-09-03, at 15:56, p at 2038bug.com wrote:


>> on the SAME time.  Nobody cares here that solar time and civil time

>> are 43 minutes off. 

> 

> *I* care 


Warner seems to be missing (or ignoring?) the point.

The difference doesn't matter, the fact that the difference is constant
does.

N



------------------------------

Message: 2
Date: Fri, 3 Sep 2010 18:49:29 +0100
From: Tony Finch <dot at dotat.at>
Subject: Re: [LEAPSECS] LEAPSECS Digest, Vol 45, Issue 1
To: Leap Second Discussion List <leapsecs at leapsecond.com>
Message-ID:
	<alpine.LSU.2.00.1009031840050.31615 at hermes-1.csi.cam.ac.uk>
Content-Type: TEXT/PLAIN; charset=US-ASCII

On Fri, 3 Sep 2010, Rob Seaman wrote:

> On Sep 3, 2010, at 2:18 AM, Tony Finch wrote:

>

> > If you are syncing to what is now called "GMT" you are syncing to

UTC

> > because they are now in practice exact synonyms.

>

> And this is precisely what the ITU is planning to break.


I'm not sure that's true. The only de jure definition of GMT is "civil
time in the UK in winter". The British government and its agencies
currently implement GMT as equivalent to UTC. If the ITU change the
definition of GMT, and if the British government continues to follow ITU
recommendations and to disregard the historical astronomical meaning of
GMT, then the equivalence will continue.

Tony.
-- 
f.anthony.n.finch  <dot at dotat.at>  http://dotat.at/
HUMBER THAMES DOVER WIGHT PORTLAND: NORTH BACKING WEST OR NORTHWEST, 5
TO 7,
DECREASING 4 OR 5, OCCASIONALLY 6 LATER IN HUMBER AND THAMES. MODERATE
OR
ROUGH. RAIN THEN FAIR. GOOD.


------------------------------

Message: 3
Date: Fri, 3 Sep 2010 19:06:34 +0100
From: Tony Finch <dot at dotat.at>
Subject: Re: [LEAPSECS] LEAPSECS Digest, Vol 45, Issue 1
To: Leap Second Discussion List <leapsecs at leapsecond.com>
Message-ID:
	<alpine.LSU.2.00.1009031853220.31615 at hermes-1.csi.cam.ac.uk>
Content-Type: TEXT/PLAIN; charset=US-ASCII

On Fri, 3 Sep 2010, Zefram wrote:


> Tony Finch wrote:

> >                        As we have seen there are a lot of intricate

> >details whose necessity people can legitimately disagree about and no

way

> >to determine an official consensus. Which is why I say that

astronomical

> >GMT doesn't exist.

>

> Interesting argument.  I disagree with your central point: I don't

> think an official realisation of GMT is required in order for GMT to

> meaningfully exist.


Note that in the above I'm talking about astronomical GMT. There is an
official realisation of legal GMT, and it is UTC. If you create a new
astronomical timescale it would be wrong to claim it is GMT. GMT(Zefram)
is probably OK though :-)


> Making a clear distinction between ideal and realisation smells like

> modern behaviour; considering the many different meanings of "GMT"

that

> have already been identified, I would not be surprised at it being

> irretrievably ambiguous in this respect.


Yes, definitely. I'm stretching when I claim that the practical
realities
of time in the UK are enough to unambiguously define GMT == UTC
(obviously, or we wouldn't be having this discussion).


> Does anyone have relevant historical documentation on the

philosophical

> definition of GMT?


This is brief and sketchy:
http://www.nmm.ac.uk/explore/astronomy-and-time/astronomy-facts/history/
the-longitude-of-greenwich

Tony.
-- 
f.anthony.n.finch  <dot at dotat.at>  http://dotat.at/
HUMBER THAMES DOVER WIGHT PORTLAND: NORTH BACKING WEST OR NORTHWEST, 5
TO 7,
DECREASING 4 OR 5, OCCASIONALLY 6 LATER IN HUMBER AND THAMES. MODERATE
OR
ROUGH. RAIN THEN FAIR. GOOD.


------------------------------

Message: 4
Date: Fri, 03 Sep 2010 12:04:39 -0600 (MDT)
From: "M. Warner Losh" <imp at bsdimp.com>
Subject: Re: [LEAPSECS] h2g2
To: leapsecs at leapsecond.com, nimh at pipe.nl
Message-ID: <20100903.120439.431102609638877642.imp at bsdimp.com>
Content-Type: Text/Plain; charset=us-ascii

In message: <67EFEC27-33C2-4D35-A48F-F7BE2ED7D846 at pipe.nl>
            Nero Imhard <nimh at pipe.nl> writes:

: 

: On 2010-09-03, at 15:56, p at 2038bug.com wrote:

: 

: >> on the SAME time.  Nobody cares here that solar time and civil time

: >> are 43 minutes off. 

: > 

: > *I* care 

: 

: Warner seems to be missing (or ignoring?) the point.

: 

: The difference doesn't matter, the fact that the difference is

constant does.

I'm asking these question: Why does it matter so much?  What does
keeping things in sync buy you that merely measuring the difference
and knowing that number doesn't?  Why must UTC be used as the method
to synchronize "noon and the sun is approx overhead" when we have wide
timezones that already do that function?  Does the cost of
synchronizing to UTC exceed the benefits from synchronizing there and
not at a different, easier to change level?  Given the changes in how
time is used, propagated, etc, in the last 20, 50 or 100 years, does
it make sense to reevaluate things?

We've undergone a fairy radical paradigm shift in how time is used and
consumed in the past 20 years.  Doesn't it make sense to reevaluate
the system to make sure those items that used to be no big deal but
have become big cost items still fit the needs of the majority of the
users?  Time was when there were hundreds of different fields that
relied on having good time to know where they were (navigators,
surveyors, etc), but with GPS eliminating those users of UTC, do we
have enough of a community of |DUT1| < 1s to justify the costs to the
rest of the world, or is it time that this crowd shoulder the costs of
the raw data they need?

Those are the questions I'm asking...

Oh, and with Daylight Savings Time, the difference isn't even constant
anymore.  And why does MEAN solar time matter more than ACTUAL solar
time?  And what flavor of MEAN solar time is best?  What does solar
time mean on mars, the moon, etc?

Warner


------------------------------

Message: 5
Date: Fri, 3 Sep 2010 18:31:32 GMT
From: msokolov at ivan.Harhan.ORG (Michael Sokolov)
Subject: Re: [LEAPSECS] h2g2
To: leapsecs at leapsecond.com
Message-ID: <1009031831.AA04534 at ivan.Harhan.ORG>

p at 2038bug.com wrote:


> > Nobody cares here that solar time and civil time

> > are 43 minutes off. 

>

> *I* care 


I do too!


> but I'm not important - I'm just one person 


There are TWO of us now!


> many people might care and many people are not getting to make

> the decision because the decision is being made for them. 


That is why I am making preparations for generating my own synthetic
time scale that is steered to serve a realization of MST, contingency
plans for the day when we may no longer be able to depend on Daniel
Gambis to do it for us.

I really liked your earlier idea of setting up an NTP server that would
serve a smooth, variable-rate timescale like UT1 or UTS or UTC-SLS, and
have an associated pledge to continue serving this form of
Earth-following
time regardless of what the ITU does to UTC.  I am thinking along very
similar lines myself.


> further, it's not a decision we can *ever* go back on once it is

> made because reversing back to solar to time would be politically

> far too difficult to get collaboration on. 


But as long as you and I continue to operate our own law-defiant NTP
servers which serve our realization of Earth time instead of the s**t
that ITU peddles, those nature-loving people who wish to live their
personal lives on mean solar time can simply choose to point their own
ntpd instances at our servers instead of those following the ITU -
problem solved.

Furthermore, there are still quite a few countries left on Earth whose
system of rulership is very non-Western.  Perhaps we can convince Raul
Castro or Hugo Chavez to use MST instead of ITU time as the basis of
legal time in Cuba or Venezuela, and to take their time reference from
our "rebel" NTP servers?  Or perhaps we can team with the folks in the
Arab world who are working on the Mecca Time idea?

I would be very willing to work with *anyone* who is in favor of
Earth-anchored time.


> that some NASA/ITU/whoever people find leap seconds "inconvenient"

> for programmers is NOT sufficient reason to ever have started

> pursuing this agenda. 


Total agreement!

MS


------------------------------

Message: 6
Date: Fri, 3 Sep 2010 19:34:59 +0100
From: Ian Batten <igb at batten.eu.org>
Subject: Re: [LEAPSECS] h2g2
To: Leap Second Discussion List <leapsecs at leapsecond.com>
Message-ID: <7A21EAEC-BB0A-4966-A8DB-86B084DF0963 at batten.eu.org>
Content-Type: text/plain; charset=US-ASCII; format=flowed; delsp=yes


> do we

> have enough of a community of |DUT1| < 1s to justify the costs to the

> rest of the world, or is it time that this crowd shoulder the costs of

> the raw data they need?


Of course, one issue is that it's not a matter of |DUT1|<1s, but  
having DUT1 at all.  The formats by which DUT1 is propagated in time  
signals deeply assume <1, so if it became >1 it couldn't be propagated  
in those signals.   Which means that any and all equipment that  
consumes it is instantly broken, as it can't recover UT1.  Even if the  
format could accommodate >1, of course, one assumes that almost all  
sane implementations would sanity check the value of DUT1 to confirm  
it's <1, so would reject the larger value anyway.

You could modify the format, but you'd have to do so in a way which  
didn't then break all the equipment that wants UTC but pokes around in  
the extra data to recover the date, or the summer time indicator, or  
whatever.  And it would involve replacing all the UT1 equipment anyway.

I don't know, and I suspect the ITU don't either, how much (if,  
indeed, there is any) equipment is currently consuming the DUT1  
portion of the national time standards, and why.

ian



------------------------------

Message: 7
Date: Fri, 03 Sep 2010 18:50:16 +0000
From: "Poul-Henning Kamp" <phk at phk.freebsd.dk>
Subject: Re: [LEAPSECS] LEAPSECS Digest, Vol 45, Issue 1
To: Leap Second Discussion List <leapsecs at leapsecond.com>
Message-ID: <89565.1283539816 at critter.freebsd.dk>

In message <alpine.LSU.2.00.1009031840050.31615 at hermes-1.csi.cam.ac.uk>,
Tony F
inch writes:


>If the ITU change the

>definition of GMT, and if the British government continues to follow

ITU

>recommendations and to disregard the historical astronomical meaning of

>GMT, then the equivalence will continue.


Just to highlight how laughable the retroimperialist love for GMT is:

Which exact meridian are we talking about again ?

Are we talking about the meridian Airy drew through his telescope or
the one we actually use, about 100m east of his telescope ?

Did anybody in England gather an orderly mob around GMT, to protect
its imperial virginity, when the WGS84 redefinition of the geodesic
origo changed it by five and a half second ?

Let me remind you that WGS84 _also_ redefined UTC.

Can we please drop this nonsense now ?

Or at least queue it, where it belongs, behind the still pending
tax-refund for the 12 missing days in september 1752 ?

Poul-Henning

-- 
Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk at FreeBSD.ORG         | TCP/IP since RFC 956
FreeBSD committer       | BSD since 4.3-tahoe    
Never attribute to malice what can adequately be explained by
incompetence.


------------------------------

Message: 8
Date: Fri, 03 Sep 2010 20:59:31 +0200
From: Paul Sheer <p at 2038bug.com>
Subject: Re: [LEAPSECS] h2g2
To: Leap Second Discussion List <leapsecs at leapsecond.com>
Cc: Michael Sokolov <msokolov at ivan.Harhan.ORG>
Message-ID: <1283540371.2334.27.camel at localhost>
Content-Type: text/plain




> I really liked your earlier idea of setting up an NTP server that

would

> serve a smooth, variable-rate timescale like UT1 or UTS or UTC-SLS,

and

> have an associated pledge to continue serving this form of

Earth-following

> time regardless of what the ITU does to UTC.  I am thinking along very

> similar lines myself.


really, it would be a bit of a gimmick

if you are serious though and implement some server and client
softare - I'd be happy to host the downloads and deploy on
2038bug.com



> But as long as you and I continue to operate our own law-defiant NTP

> servers which serve our realization of Earth time instead of the s**t

> that ITU peddles, those nature-loving people who wish to live their

> personal lives on mean solar time can simply choose to point their own

> ntpd instances at our servers instead of those following the ITU -

> problem solved.


well the number of user's we are likely to accrue would be
small - most people that use NTP need their servers to stay
within a few milliseconds of everyone else - that is *why*
they use NTP.

-paul






------------------------------

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