Myths about the Winter Solstice

By Shlomo   Maital   

Stonehenge

                                               Winter Solstice at Stonehenge, England

Today, Dec. 21, is the shortest day of the year in the Northern Hemisphere. It is known as the winter solstice. But – what is it exactly? Here is some help from the BBC. And a few myths are dispelled.

   What is it exactly?

     “This Sunday, 21 December, the northern hemisphere will experience the shortest day of its year, marked at 22:03 GMT by an astronomical phenomenon known as the winter solstice – the moment the North Pole is tilted furthest from the sun as the Earth continues on its orbit.”

     In the Southern Hemisphere, it is the summer solstice – the moment the South Pole is tilted CLOSEST to the sun as the Earth continues on its orbit.

   Doesn’t the winter solstice occur always on Dec. 21?

   No.  “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.”

   Doesn’t it get light earlier in the morning, from now on? And get darker later?

   No. “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 and the sunset began later two weeks ago.”

   Why??

The answer is a bit complicated, according to a British astronomer. “Because the solar day is not precisely 24 hours. It varies. …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. The sun therefore in effect lags behind the clock for part of the year, then speeds ahead of it for another.   As you can imagine, it would be complete chaos if our clocks and watches had to cope with days of different lengths, so 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.”

   What is the link between Stonehenge, England and the winter solstice?

   The massive stones at Stonehenge are positioned precisely, so that the sunrise on the solstice peeks between the stones. A great many people rise early to watch this wonderful sight, which this year will occur on Dec. 22, as explained above.

Advertisements