Sunday, 21 December 2014

21st December 2014 - Happy Solstice but not the shortest day!

Thought for the day : "Why are the things sent by car called shipments and things sent by ship cargo?"

So, Winter Solstice. December 21st (Actually may be the 22nd next year apparently as the hours changes each year.) Last year's arrived at 17:11. Next year's will at 04:38. This year will be 23.03.

It would seem logical that after the shortest day has elapsed the mornings would start getting lighter earlier, but this isn't what happens - the mornings continue darkening until early in the new year. Apparently sunrise will be a few minutes later by 31st December when it all starts turning around properly. Apparently Sunset will also fail to start getting later until January.

So what is behind this peculiarity, which appears to fly in the face of received wisdom about the solstice - surely the shortest day should experience the latest sunrise and earliest sunset?
Well, the primary reason behind it all is that a day - a solar day to be precise - is not always exactly 24 hours.

In fact, it is 24 hours only four times a year, and never in December, I read in fellow blogger's "The Science Geek." It is at its shortest around 23 hours 59 minutes and 30 seconds, in early September, and at its longest around 24 hours 30 seconds in December.

The sun lags behind the clock for part of the year, then speeds ahead of it for another. We use 24 hours, the average over the whole year, for all timekeeping purposes.
So, as the solar days in December are on average 24 hours and 30 seconds, while our clocks and watches are still assuming that each day is exactly 24 hours, this causes the day to shift about 30 seconds later each day.

This cumulative shifting explains why the evenings draw in towards their earliest sunset a couple of weeks before the shortest day, and why the mornings continue to get darker until a couple of weeks after.

So, I think this means a few more minutes drinking up time !!!
A good thing the clocks were always at a quarter to eleven in the Crimson Moon...


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