I suggest that UT, as a concept, can be extended as far back as the
location of Greenwich
can be discerned, even if it was known by some other name. I suggest
that encompass all
recorded history. Since UT1 was originally defined as a function of
sidereal time and the function was created by Simon Newcomb, UT1 can be
extended back to
1900. UT2 was used in the 1950s to 1970s. See McCarthy and Seidelmann's
_TIME From Earth
Rotation to Atomic Physics_ p. 14.
I would also suggest that for the class of problems that people who
don't want to know
about leap seconds will try to solve with computers (and a class
restricted to events that
were recorded long before ordinary computer could provide timestamps
with sub-minute
accuracy) the time scale for a given application will be the wrist watch
of the person on
the street, reduced by use of a time zone offset to Greenwich. Before
that, the time
scale will be the biological clock of the person recording the event,
reduced by an estimate
of the recorder's longitude to Greenwich.
Gerry Ashton
On 1/29/2011 5:31 PM, Stephen Colebourne wrote:
On 29 January 2011 15:06, Gerard Ashton<[email protected]> wrote:
I suggest the following replacement for parts of the the Instant
description. I offer the replacement because the wording of
UTC-SLS clearly only applies after 1 January 1972, and that
scale should be regarded as undefined prior to that date.
Thanks for the thoughts. I can see where you are driving at, but since
UT/UT1/UT2 are not well-defined in the far past AFAIK, then the
definition below isn;t ideal either. I agree that something needs to
change though.
Stephen
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