[LEAPSECS] How good could civil timekeeping be?
seaman at noao.edu
Wed Feb 13 12:57:15 EST 2008
The threads are coming fast and furious. Cutting to the chase.
If the precision timekeeping establishment falters in its role of
delivering a useful representation of mean solar time, clearly some
other community will have to pick up the slack. It is likely not
helpful to bring the Goddess into it, but I personally spurn no
The heart of civil timekeeping is the dynamic tension between the two
definitions of the "second":
- as 1/86400 of a mean solar day, and
- as the SI unit of time
If this distinction had been made crystal clear in the beginning, we
wouldn't be having this discussion now.
Recall the historical idea of calling the SI unit the "essen". What
if, in addition, the essen had a duration of a size that could not be
confused with the fractional part of the day? For example, what if
the essen had been chosen such that the acceleration due to gravity
was a convenient 1.0 meters per essen-squared. So:
1.0 m/essen^2 = 9.8 m/s^2
1.0 second = 3.13 essen, and
1.0 essen = 0.319 second
In this case (or pick some other physically significant value), there
never would have been the confusion about counting essens using
sexigesimal notation. In particular, a meaningless tally of 86400
essens would have wrapped around 3+ times per day. And the definition
of a day - that is, an actual mean solar day - would remain clear.
In short, the distinction between the role of the second and the role
of the essen in timekeeping architecture would remain obvious.
This design pattern can be used to distinguish technically viable
solutions - like UTC with leap seconds, and Steve's expression of TI -
from technically nonviable solutions like a so-called "UTC" without
leap seconds. The role of political expediency in the decision-making
would be clear. I won't say expediency still wouldn't triumph over
technical common sense, but that fact would be clear to all.
> And that is, pretty close, the proposal in WP7A, except they mention
> the "leap-hours" as a silly figleaf to the astronomers and other die-
> hard sun-in-the-south-at-noon (mostly religious) addicts.
Let me - yet again - emphasize that people with diametrically opposed
notions of timekeeping all regard the leap hour as an absurd notion.
> come up with a workable proposal, canvas it for the right people,
> repeat until done.
This group is one place the canvas is taking place. Part of making a
proposal workable is pointing out the unworkable proposals, especially
if the unworkable ones are receiving undue (and unwise) political
At any rate, glad to see that you agree that the process should focus
on characterizing the workability of coherently expressed and properly
communicated proposals. That's pretty much what I've been saying for
eight years. It is also simply the definition of a trade-off study.
I especially like that you focus on this as an iterative process.
National Optical Astronomy Observatory
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