[ntp:questions] Google and leap seconds

unruh unruh at wormhole.physics.ubc.ca
Wed Sep 21 21:26:23 UTC 2011

On 2011-09-21, Richard B. Gilbert <rgilbert88 at comcast.net> wrote:
> On 9/21/2011 2:59 PM, John Hasler wrote:
>> Richard B. Gilbert writes:
>>> It's unfortunate that the earth DOES NOT rotate exactly 360 degrees in
>>> exactly 24.000000000000 hours. This bit of poor design causes all
>>> sorts of problems.  Leap seconds are just one of the symptoms!
>> Leapseconds are localization, like time zones, daylight saving, and
>> leapyears.  It's unfortunate that they are considered part of the
>> timestream.
> Too bad that the movements of of the planets, moons, etc. are not better 
> behaved.  Lacking the powers of the divine we must work around the fact 
> that the earth does not rotate exactly once in each twenty-four hours, 

Again, that was the exact definition of the second until very recently.
That we now (for the past 50 years or so) define the second in a way divorced from the rotation of the
earth is what the problem is, not that the earth does not rotate in
exactly 24 hours. 

> and the fact that its revolution around the Sun is similarly messy, 
> taking 365 days, six hours, and a few odd minutes and seconds which we 
> account for (mostly) by declaring a "leap year" every four years.  Those 
> "odd minutes and seconds" also add up and must be accounted for every 
> hundred years or so.

It would of course have been better if we had adopted the Dee proposal
of 8 leap years every 33 years, instead of the current mishmash (every 4
years except centries except every fourth century, etc--essentially -- 97 leap years out of every 400) since it would
have been more accurate and given a much smaller deviation of the
calendar year from the true year (+- 1/2 day instead of +- 2 days or so)

Of course everyone complains that doing arthmetic mod 33 is harder than
arithmetic mod 400.

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