[LEAPSECS] Changing the name of UTC

Thu Oct 16 18:02:02 EDT 2014

With regards to Gerard's question (below), I think the answer is that his timescale is one of a large class of possible timescales that could be given any name desired as soon as anybody had a use for it.   It would be trivial to compute the calendar dates he talks about of course,  but it's not clear to me who would care about such a timescale.    Pulsar astronomers, for example, would not use it.   To reduce observations with the best precise time available, they want Terrestrial Time (TT), which is computed by the BIPM as a time series in the form TT-UTC.   No matter what is done with UTC, astronomers who need the precision should use the BIPM tables to take care of not just leap seconds but certain more subtle corrections to UTC.   On the other hand, what is needed by lawyers, insurance companies, historians, etc. is the calendar date and appropriate legal time associated with the events of interest - they wouldn't care about SI seconds.

I'd like to take the opportunity to ask this crowd what they think of the statements below:

1. Those who are in favor of UTC redefinition currently oppose the name change (emphasis on currently)

2. Those who are against UTC redefinition insist that the name should be changed.

3. There is no one who says he/she would support UTC redefinition, but ONLY IF the name is also changed.

Are there any significant exceptions to this generalization?    I was told by a British source that a "certain stakeholder" had indicated he did not care either way about the redefinition, but if a redefinition were to occur this stakeholder thought the name should be changed.   I believe this story, but it is a fact that these sources are working under very strict constraints set by their bosses in the UK government, with very close oversight by the same.

I have also observed the cases wherein webmasters are believed to be opposed the redefinition have not corrected errors on their web pages even when they are aware of them.    I'm unaware of web pages put up by groups in favor of the redefinition, but if anyone knows of such omissions on the pro-redefinition side I'd be curious and maybe could use my influence to correct.   I'm not interested in minor errors, but in errors of fact that are either significant in themselves or which as presented allow misinterpretation by others. 

Back to the name change, a list of arguments each way is below.   Pro means in favor of a name change.   Have I missed any arguments?

Pro: Keeping the name UTC would cause confusion.

Con: Keeping the name UTC would reduce confusion.

Pro: UTC would be ambiguous if the name were kept, because UT1-UTC would be unbounded.

Con: UTC would be still be uniquely defined if the name were kept.   That's because integrated step function is well defined, and UT1-UTC  would be something like that.

Pro: A presentation from a representative of the appropriate committee of the International Standards Organization says the name should be changed.

Con: The ISO has 290 committees, which people frequently disagree with and are not bound to follow.  In this case the advisory opinion goes against the standard metrological practice of not changing names.  The best example is UTC itself when  frequency steers to UT1 were eliminated.   Also the meter, which went from a physical meter bar in Paris to the product of the speed of light with the SI second.  And the kg, which is about to be redefined but no one is suggesting a name change.  Another example where changing the name would have caused confusion is the 2006 redefinition of the term "planet". 

Special Con: GMT was redefined in 1925 with a 12 hour shift so the day would change at midnight instead of noon, with no name change.   Although the GMT redefinition did lead to some confusion, there is no way the UK would have considered abandoning the name GMT.

Pro's answer to special CON: The Universal Times were set up several years later, partly in response to the GMT shift (I don't know the details). 

Pro: Universal in UTC means rotation of the Earth (as in UT0, UT1, and UT2)

Con: Universal in UTC means universally used (as are the numerical UT's by the way)

Pro's answer to CON: Universal was meant to mean rotation at the time the name was selected

Con's reply to Pro's answer to CON: The two ideas were not contradictory back then, given that the C in UTC means coordinated between laboratories.   Therefore even written descriptions, if they exist and support the PRO arguments, would not be relevant.

P.S. I only receive daily digests, so I apologize if someone sent an email today that I seem to be ignoring.

-----Original Message-----

Message: 2
Date: Wed, 15 Oct 2014 11:20:35 -0400
From: "Gerard Ashton" <ashtongj at comcast.net>
To: "'Leap Second Discussion List'" <leapsecs at leapsecond.com>
Subject: [LEAPSECS] Name of proleptic leap-secondless UTC
Message-ID: <000e01cfe88b$91c99880$b55cc980$@comcast.net>
Content-Type: text/plain;	charset="us-ascii"

If the view put forward in Australia's document cited by Steve Allen prevails, something serious is missing. Every time scale I've ever heard of has a projection into the past, before the time scale was fully defined. Of course, the precision of such projections is limited by the available data, but people will insist on projecting every time scale into the past. So UTC abandons the insertion of leap seconds at time F. What shall we call the time scale which is formed by subtracting the desired number of SI seconds from F and, if desired, expressing as a Gregorian or Julian calendar date and time of day at quasi-Greenwich, where each day consists of exactly
86,400 SI seconds?

Gerard Ashton

-----Original Message-----
From: LEAPSECS [mailto:leapsecs-bounces at leapsecond.com] On Behalf Of Steve Allen
Sent: Wednesday, October 15, 2014 11:07 AM
To: Leap Second Discussion List
Subject: [LEAPSECS] draft CPM report on UTC

Australia has released the content of the draft CPM report on UTC, one of the two competing documents that was on the table at the end of the WP7A meeting earlier in this year.

http://acma.gov.au/Industry/Spectrum/Spectrum-planning/International-plannin
g-ITU-and-other-international-planning-bodies/wrc-15-agenda-item-114

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