[time-nuts] How many seconds in a year?

Hal Murray hmurray at megapathdsl.net
Wed Oct 15 06:38:42 UTC 2008


> Which now gets me back to my question. If I want to make a clock that
> chimes once per solar year when we have completed a cycle it will
> count down a number of seconds then chime. So I want to know the
> number of seconds   in a Mean Year, accurate enough so that in 200
> years time it will still be right. 

What does "right" mean?

The traditional leap year calculation is good down to (roughly) 1 day per 400 
years.  That's 86400 seconds per 400 years or 216 seconds per year.  Or 
perhaps significantly better.

(Those old geezers had really good telescopes and knew how to drive them.  
One of the proposals fighting for the navigation prize that Harrison 
eventually won was getting time by watching Jupiter's moons.  They even 
corrected for speed of light delays due to relative orbital positions.)

Leap seconds happen every year or so, at least so far.  Who knows what will 
happen tomorrow.  Thats 1/2 % of the leap year corrections.

So what do you mean my "right"?  Do you want legal midnight?  Sidereal 
midnight?  Solar midnight?  ....  How close do you want to be?

200 years is halfway through the 400 year leap cycle, so if you do one 
obvious thing, you will be off roughly 1/2 day.







-- 
These are my opinions, not necessarily my employer's.  I hate spam.






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