[LEAPSECS] Solar time: From mean solar days, to mean solar years

[Warner Losh]

On Aug 20, 2014, at 7:40 PM, Brooks Harris <brooks at edlmax.com> wrote:

> Since the beginning of civilization society has pursued the goal of perfect timekeeping. UTC is one of the great intellectual achievements of mankind.
> 
> The difficulties with Leap Seconds are rooted in computer standards and implementations, not theory. We must strive to advance the state of the art, not abandon 4500 years of timekeeping history just because its difficult. Ceaser didn't quit. Pope Gregory didn't quit. Harrison didn't quit. Newcomb didn't quit.
> 
> "Dropping Leap Seconds" is something like burning great libraries.

Not sure I buy this hyperbole. Leap seconds suffer from many minor issues that are only going to increase as we get more and more connected. The stubborn refusal for any changes in the current implementation has me thinking of them as less than great libraries, and more as pebbles in my shoes. There are many better ways to implement them, and “perfect timekeeping” always begs the question of “perfect for whom.” De we align them with the day or the year? If we pick one over the other, the other gets out of sync.

Warner

> -Brooks
> 
> On 2014-08-20 04:02 PM, Preben Nørager wrote:
>> OMG its 290091200278565000. With THAT my proposal still stands :-)
>> 
>> 
>> 2014-08-20 21:48 GMT+02:00 Keith Winstein <keithw at cs.stanford.edu>:
>> Check that multiplication... :-)
>> 
>> On Wed, Aug 20, 2014 at 2:42 PM, Preben Nørager <samp5087 at gmail.com> wrote:
>> > I can not edit the numbers in my initial post, but I can do it here, and
>> > with that my proposel still stands: Drop the leap second, and continue UTC
>> > without leap
>> > seconds, so that 1 mean solar year is defined as the
>> > duration of 290091175979732 [31556925,9747x9192631770] periods of
>> >
>> > radiation in the caesium atom
>> >
>> >
>> >
>> > 2014-08-20 16:43 GMT+02:00 Keith Winstein <keithw at mit.edu>:
>> >
>> >> To be a pedant [but if you can't be one on the leapsecs mailing
>> >> list...], the SI second is *9192631770* periods of the radiation etc.
>> >> Your figure is high by 1000.
>> >>
>> >> On Wed, Aug 20, 2014 at 9:22 AM, Preben Nørager <samp5087 at gmail.com>
>> >> wrote:
>> >> >
>> >> > In the discussion about whether or not to drop the leap second, I think
>> >> > it
>> >> > is not a question about solar time or not solar time. It is in other
>> >> > words
>> >> > not a question about either solar time or atomic time.
>> >> >
>> >> >
>> >> >
>> >> > If we drop the leap second it will be in favour of another timescale,
>> >> > which
>> >> > uses only atomic clocks to tell the time, but the time in that other
>> >> > timescale will still be based upon a kind of solar time.
>> >> >
>> >> >
>> >> >
>> >> > About a hundred years ago it was decided, that the mean solar year, and
>> >> > not
>> >> > the mean solar day, should be the unit of international time.
>> >> >
>> >> >
>> >> >
>> >> > In 1960 the second was defined as 1/31556925,9747 of the mean solar
>> >> > year,
>> >> > and in 1967 the second was redefined [equally in length to the
>> >> > previously
>> >> > defined second] as the duration of 9192632770 periods of radiation.
>> >> >
>> >> >
>> >> >
>> >> > When the second was defined in 1960 it was defined as a fraction of the
>> >> > so-called tropical year. That was a mistake of wording. The tropical
>> >> > year is
>> >> > a measurement of the solar longitude on the ecliptic, but the
>> >> > international
>> >> > definition of the second is not based upon measurement of the solar
>> >> > longitude on the ecliptic.
>> >> >
>> >> >
>> >> >
>> >> > The definition of the second is based upon Newcomb's theory of the solar
>> >> > system, and in that theory it is the barycenter of the solar system, and
>> >> > not
>> >> > the center of the sun, which defines the length of the solar year.
>> >> >
>> >> >
>> >> >
>> >> > The length of the solar year, according to Newcomb’s theory, is the time
>> >> > for
>> >> > the longitude of the barycenter of the solar system to increase 360
>> >> > decrees.
>> >> >
>> >> >
>> >> >
>> >> > The solar year, thus defined, can be measured either for one year, or
>> >> > for an
>> >> > average of years.
>> >> >
>> >> >
>> >> > But the 1960 and the 1967 definition of the second can also be used as
>> >> > an
>> >> > international definition of the mean solar year.
>> >> >
>> >> >
>> >> >
>> >> > I think we should drop the leap second, and continue UTC without leap
>> >> > seconds as TI [International Time], so that 1 mean solar year is the
>> >> > duration of 290091231835491000 [31556925,9747x9192632770] periods of
>> >> > radiation in the caesium atom.
>> >> >
>> >> > _______________________________________________
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>> >> >
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>> >
>> >
>> 
>> 
>> 
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