Hi Kevin,
> I'm still puzzled at the reasons for stating that UT1 should not be
> considered as a time scale in this recommendation. How does that serve this
> recommendation? This is a bit of a different question from evaluating UT1 as
> a time scale. Instead, it is a question about the reasons why the evaluation
> of UT1 must be included in this recommendation. Does saying that UT1 is not
> a time scale strengthen the other points in any way? Is it necessary for the
> other points to be accepted?
It is a "statement against interest" as they say in the courts, an implicit
admission that two different timescales are required (in the engineering
sense). The authors don't want to call Universal Time a time scale (in its
avatar as UT1 or otherwise), but they can't eliminate the concept.
Hence also the attempt to subdivide UTC into three separate terms:
"Coordinated" + "Universal" + "Time", rather than the two terms it represents
in historical and the worldwide current context: "Coordinated" + "Universal
Time". This is emphasized by UT1 itself, because by the same logic it would be
"Universal" + "Time" + "1", which is obviously a time. See, for example, the
next bullet:
10. the International Earth Rotation and Reference Systems Service
(IERS) provides a means of accessing UT1 in real-time by means of routinely
available predictions of UT1-UTC with precision 100 000 times better that the
coarse approximation UT1 = UTC currently provided by means of coding UTC to
match UT1 within 0.9 second;
To quote a friend: "If UTC is time, and if UT1 is angle, then what is
(UT1-UTC)? How can one subtract angle from time and have a meaningful result,
without both being instantiations of the same concept?"
There has been an attempt to redefine the language for years, since an earlier
revision of ITU-R TF.460 was edited to remove the original language:
"GMT may be regarded as the general equivalent of UT."
Leap seconds are a means to an end, which is to root civil timekeeping in mean
solar time - that is, in the synodic day. By all means lets discuss alternate
ways to implement this, but simply declaring that Universal Time no longer
exists as a concept is a non-starter. We will reach consensus more quickly by
first seeking common language and concepts. If a new concept is needed, define
a new term.
Rob
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