[Leica] Longest night

[hlritter at bex.net (Howard Ritter)]

An interesting footnote is that the natural assumption that the  
earliest sunset and the latest sunrise would also occur on the day of  
(or the night before or the morning after) Winter Solstice isn't true,  
not by a long shot. These occur symmetrically well before and after  
the Solstice. I remember how surprised I was, years ago, when I  
learned that, at 40 degrees north latitude, the earliest sunset comes  
an entire two weeks before the Solstice and the latest sunrise a  
similar length of time after the Solstice. And the earliest end of  
evening twilight/onset of night is three days earlier still, likewise  
the opposite in the morning. The offsets are down to the complex  
interplay and the asymmetries of the geometry of the Earth's  
elliptical orbit, the varying speed of the Earth in its orbit, the  
inclination of the equator to the orbital plane, and the relationship  
between the point in its orbit where the Earth is nearest the Sun  
(perihelion, Jan 4--and it's pure coincidence that these two dates are  
even close to each other) and the point where the plane of the Earth's  
equator passes furthest north of the Sun (the Winter Solstice, Dec  
21). Repeat the above, with appropriate substitutions, for the Summer  
Solstice.

--howard


On Dec 21, 2008, at 4:21 AM, Bob W wrote:

> At 12:04 GMT today it is the midwinter solstice. The shortest day, the
> longest night. That means that from now on the days get longer -  
> hooray! At
> least in the northern hemisphere.
>
> Here's a reminder of this year's midsummer solstice:
>
> http://www.web-options.com/Midsummer2008/
>
> Olympus E-1, 14-54mm & 11-22mm lenses, FL-36 flash
>
> Bob
>
>
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