[LEAPSECS] civil-solar correlation with TI
seaman at noao.edu
Fri Dec 26 12:27:39 EST 2008
On Dec 23, 2008, at 9:33 AM, Zefram wrote:
> Suppose that people in the future overwhelmingly want local civil
> time of day to continue to approximate local solar time of day.
Again, the issue is mean solar time, not local solar time. An
underlying timescale based on mean solar time is what allows all the
local civil/solar issues to be resolved cleanly together.
Just to be clear, it also isn't a question of people's "preferences",
it is a question of discovering requirements implicit in our society.
One may or may not agree with me that mean solar time is the key, but
at no point over the millennia will the issue just be one of what
people want (whether overwhelmingly or not).
> [...] I think in this situation it is inevitable that the timezones
> will shift.
> [...] After five millenia Britain might be on TI-65h. The local
> date gets to be substantially different from the TI date, to the
> same sort of degree that the local hour-of-day currently differs
> from the UTC hour-of-day. Timezone offsets continue to grow
> secularly without bound. Sounds unworkable? Possibly, but I can't
> put my finger on any reason why large offsets per se would cause the
> system to collapse.
Because time is a quantity with memory. Historians looking backward
want to relate events worldwide and arrange them into coherent
timelines. Whatever the preferences of the ITU, they will discover
that it is simply unacceptable to allow local dates to vary secularly
from civil timekeeping dates.
We can speculate on all sorts of systems of timekeeping, up to and
including Star Trek style stardates. Many different systems can be
described that are technically workable. Only one - standard time
based on mean solar time - has ever been shown to be *practically*
workable. Before adopting another - even by so apparently subtle a
change as omitting that first leap second in 2019 - a carefully
crafted analysis of the consequences and a coherent plan of action
should be developed.
Red tape? Bah Humbug! It is simple common sense to plan ahead. The
issue isn't one of a second here and there - the issue is keeping the
definition of the word "day" straight.
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