Or, Megalithic time-keeping
Or, Equinox and Solstice, the red-herrings
Or, the TME Christmas Bonus.
Something topical for this time of the year.
Question: What do we mean by a Solstice?
Answer (from someone with an MBO* degree) : It's the day of the year when the sun is visible for the longest or shortest time.Time
. There it is, the word's been said.
How would megalithic folk, with no clocks or watches, have any idea what the time was?
Or how to tell the time?
Or measure the passage of time?
Question: In the absence of a clock, what would megalithic folk have been observing or measuring?
Answer: It was the observed motion and positions of the sun, moon, planets and stars.
All these observed positions are, of course, relative to the Earth, and especially where you are on the Earth. Last Sunday, 21 December 2014, apparently, the northern hemisphere experienced the shortest day of its year at 23:03 GMT - the moment the North Pole is tilted furthest from the sun as the Earth continues on its orbit.
According to a recent BBC article
:The solstice doesn't always occur on 21 December. Sometimes it nudges into the early hours of 22 December, which will happen again next year. The hour of day also varies. Last year's arrived at 17:11. Next year's will at 04:38.
Especially for those of us who get up in the dark to travel to work, the more astute of these early risers might have perceived a curious development, which may have passed by the more bleary-eyed unnoticed. 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!
e.g. Sunrise and sunset in London in 2014/5
Day / Sunrise / Sunset / Day length (h:mm:ss)
11 December 2014 - 07:56 / 15:51 / 7:55:37
21 December 2014 - 08:04 / 15:53 / 7:49:45
31 December 2014 - 08:06 / 16:01 / 7:54:39
31 January 2015 - 07:41 / 16:48 / 9:06:42
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? It's because there's not 24 hours in a day!
There are two reasons why the length of the solar day varies, the first being the fact that the axis of the Earth's rotation is tilted - 23.5 degrees from vertical - and second, the Earth's speed varies because it moves in an elliptical orbit around the sun, accelerating when it is closer to the star's gravitational pull and decelerating when it is further away.
* MBO = Master of the Bleeding Obvious