[LEAPSECS] Cheating means more planning, not less
M. Warner Losh
imp at bsdimp.com
Sun Dec 28 18:57:08 EST 2008
In message: <1FB1C7F7-95F4-450A-B823-349ABA3B8A77 at noao.edu>
Rob Seaman <seaman at noao.edu> writes:
: However, nobody has been arguing for rubber seconds. (Except on
: extremely long timescales exceeding the current age of civilization on
: Earth.) Your assertion is a straw man:
Actually, it isn't. Your arguments are so full of logical fallacies
that I don't even bother any more.
I know that nobody is proposing rubber seconds today. You know I know
that. I'm saying that the second used to be a measure of the change
in the earth, since it was a subdivision of the day. By its very
nature, it was rubber, since it was a subdivision of something that
was rubber. It is called historical perspective, and is quite
relevant to your assertions that there's something inherently 'mean
solar time' about UTC. There isn't. It is an atomic scale that is
presently kept in sync with mean solar time.
And there were rubber seconds from 1961 until 1972. The clocks were
ticking at slight offsets to the atomic time to keep the atomic time
scale (UTC) in sync with the mean solar time. This, I was arguing,
was an extension of the prior 'rubber seconds' which were a division
of the day, which was by its very nature rubber in length for a very
: Meanwhile, the length of day has been malleable since before the
: Cambrian Explosion, let alone over any modern human timescale. We are
: saying nothing new here.
: The real observation is the familiar one of dual timescales. Focus on
: the SI second and we see the world through atomic eyeballs. Focus on
: the primacy of the definition of the day in civil timekeeping, and
: Earth orientation pops out.
: Both timescales are necessary.
I think we disagree about what is primary in the civil time keeping.
I don't think it has to be mean solar time, except in a very gross
sense of the terms. I think it can vary quite a bit from mean local
solar time, and it will still work. I believe that the tolerance of
local time is on the order of 10000 times less strict than the current
practice of inserting a leap second when UT1 and UTC differ by too
much (typically by more than .5s). It can easily tolerate a large
variance and people are still cool with it. 10000x translates to
something just over an hour.
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