Reference Year Displacement

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Reference Year Displacement

Karl Palmen

Dear Michael and Calendar People

 

Here is my attempt to explain what I meant by DR in my guess at what Michael meant by calendar’s centre of oscillation.

 

Michael has mentioned a reference year and this reference year has a length, which he sets his calendar mean year (Y) near to. Unlike Y, the length of the reference year changes slowly from year to year, because of changes in Earth’s rotation, precession rate etc.

 

The reference year displacement (DR) is reckoned in the same way as the calculated displacement (DC), but instead of using Y, one uses the exact length of the reference year for that year.

 

I put this DR in my guess rather than actual displacement, because Michael referred to this centre of oscillation being used to calculate how far off the calendar is (with respect to its reference year). Using actual displacements instead of DR would be complicated, because the actual displacement can change substantially across each displacement year. One could use the average actual displacement across an entire displacement year.

 

Karl

 

16(06(17

 

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Re: Reference Year Displacement

Michael Ossipoff


On Mon, Feb 13, 2017 at 8:36 AM, Karl Palmen <[hidden email]> wrote:

Dear Michael and Calendar People

 

Here is my attempt to explain what I meant by DR in my guess at what Michael meant by calendar’s centre of oscillation.


...except that a guess wasn't needed, because I clearly stated what i was referring to.

I'll say it just one more time:

I was referring to, and said at the time that I was referring to, the center (midpoint) of the oscillation an SEL's calrendar date (including time of day), from one leapyear to the next.

 

Michael has mentioned a reference year and this reference year has a length, which he sets his calendar mean year (Y) near to. Unlike Y, the length of the reference year changes slowly from year to year, because of changes in Earth’s rotation, precession rate etc.


and planetary perturbations.
 

 

The reference year displacement (DR) is reckoned in the same way as the calculated displacement (DC), but instead of using Y, one uses the exact length of the reference year for that year.


Not practical for use with a civil-calendar leapyear-rule.
 

 

I put this DR in my guess rather than actual displacement, because Michael referred to this centre of oscillation being used to calculate how far off the calendar is (with respect to its reference year).


...due to Y being different from even the initial value of the length of an SEL's tropical-year. I wasn't interested in gradual change in the actual length of the reverence-year, over the milennia. I was interested in the initial difference between Y and the length of some SEL's tropical year. 

...such as you'd have if you used one SEL's tropical year, and were concerned about the calendar-date of a different SEL.

But yes, it goes without saying that later gradual change in the actual length of the reference year (whose assumed length is represented by Y) will cause additional drift.

That isn't controversial, and I never said otherwise. It just wasn't what I was talking about. I was talking about the relatively large and immediate drift resulting from the use of one SEL's tropical year, when one is looking at another SEL's calendar-date constancy.

Michael Ossipoff

 

 


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