[LEAPSECS] WP7A status and Re: clinical evidence about time and sun
seaman at noao.edu
Fri Dec 19 18:42:00 EST 2008
On Dec 19, 2008, at 10:34 AM, John Cowan wrote:
> Rob Seaman scripsit:
>> One supposes the lunar synodic period would be divided into 30 parts.
> *One* may suppose it, but others have not, such as Manuel Garcia
> O'Kelly-Davis, an actual (though fictional) resident of Luna,
> the timescale discussions of the "Ad-Hoc Congress for Organization of
> Free Luna":
> Another time they argued "time." Sure, Greenwich time
> bears no relation to lunar. But why should it when we live
> underground? Show me loonie who can sleep two weeks and
> work two weeks; lunars don't fit our metabolism. What was
> urged was to make a lunar exactly equal to twenty-eight days
> (instead of 29 days, 12 hours, 44 minutes, 2.78 seconds)
> and do this by making days longer--and hours, minutes,
> and seconds, thus making each semi-lunar exactly two weeks.
So the two things that would be preserved (in addition to honoring the
lunar day/night cycle), are sexagesimal notation and the 7-day week?
I wonder if Heinlein even realized his tunnel vision here? At any
rate, I'm skeptical that a cycle of 25h19m (in SI units) would be
physiologically acceptable even without the next point:
> Sure, lunar is necessary for many purposes. Controls when
> we go up on surface, why we go, and how long we stay. But,
> aside from throwing us out of gear with our only neighbor,
> had that wordy vacuum skull thought what this would do
> to every critical figure in science and engineering? As
> an electronics man I shuddered. Throw away every book,
> table, instrument, and start over? I know that some of my
> ancestors did that in switching from old English units to
> MKS--but they did it to make things easier. Fourteen inches
> to a foot and some odd number of feet to a mile. Ounces
> and pounds. Oh, Bog!
> Made sense to change that--but why go out of your way to
> create confusion?
The underlying alternatives outlined in the 1999 GPS World article
(and in my screed http://iraf.noao.edu/~seaman/leap) remain. To
synchronize two clocks (Earth and Lunar in this case), you can adjust
the rates on one end or the other, or you can reset the zero point of
one or the other on some sort of schedule. Additionally, if the
differential rates continue to vary, then the scheduling has to vary.
If the clock rates are too far apart, the best solution is to put two
clocks on the wall. (Most of the arguments over the past five years
are equivalent to a requirement to label the clocks correctly. Don't
call it UTC if it isn't UTC.)
It is only that the SI second (essen) and the civil second (1/86400 of
a mean solar day) are still very close that a scheme of ignoring the
whole thing for a few generations can even be entertained. If the SI
second had been chosen (as it arguably should have been) to be some
different, non-denumerable duration, then we would be worrying about
civil timekeeping as the entirely separate issue that it is.
This idea reaches back to the dawn of precision timekeeping.
Harrison's #4 clock succeeded where the first three failed because he
stopped trying to build a perfect clock, and instead chose to
calibrate imperfect chronometers. His navigational solution would
have worked perfectly fine if the rate of the chronometer was quite
distinct from the diurnal rate.
Similarly, if sexagesimal were reserved for angles (like mean solar
time), instead of being misused for interval timing, issues as above
would be simplified because Heinlein wouldn't need to fret
unnecessarily over scientific and engineering units. My copy of "The
Moon is a Harsh Mistress" is in some box in the garage. I gather the
passage is implying that the loonies simply use GMT, rather than
lunations (other than that this matters for "many purposes") or trying
to use the "rationalized" 28-day units?
The key issue in the passage above is the implicit meaning for
timekeeping on Earth, not the Moon.
(Any good quotes from Clarke or Asimov? Heinlein is always a bit too
concerned with his underlying political agenda to focus on details of
technology for its own sake.)
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