Tomorrow is the shortest day of the year for those of us living in the Northern Hemisphere. It is the Winter Solstice, also referred to as the ‘Southern Solstice’ (because the South Pole faces the Sun) and for obvious reasons ‘December Solstice’.
On the day of the Winter Solstice the Sun, at noon, will be at its lowest point above the horizon for the year — it will also rise at the furthest point Southeast it ever reaches during the year. The sunset that day will also be at the most Southerly point.
The Winter Solstice was a very important day in olden times. On this day the Sun God (Sol) had to be beseeched not to abandon the world, but to come back to start another year … It was one of the most important holidays of the year. ‘Christmas Revels‘ is a celebration of how various cultures dealt with this pivotal day of the year. In the 4th Century Christian leaders morphed the Solstice holiday into becoming Christmas.
If you want to be pedantic, ‘solstice’ per se refers to the exact moment when the Earth ‘turns the corner’ in its orbit around the Sun. It is the exact moment when the South Pole is at its closest to the Sun for that orbit. That exact moment is fleeting. Less than a minute. It will occur tomorrow, December 21, 2012, at 11:12 AM G.M.T. For us in New Hampshire, 5 hours behind G.M.T., it will thus occur at 6:12 AM. But, we tend to call the whole day, which could fall on the 20th or 22nd of December, though the 21st is the most common, ‘Winter Solstice’.
Note that the increase in the length of the (or the decrease leading up to the Solstice) is a bit jerky varying between 4 and 5 seconds a day in the above chart. This amount changes over the year. But, the inconsistency remains. It is also worth noting that the increase in the length of the day is not evenly split between sunrise and sunset. There is always some level of asymmetry. January 4, 2013 to January 5, 2015, we gain a whole minute, but the sun rise time is the same for both days. That whole minute has to do with the sun set shifting from 4:24 pm to 4:25 pm (in Concord, NH).
The Solstices and the Equinoxes (when all of Earth get an exact 12 hours of day light) have all to do with the 4 seasons of the Earth, which in turn comes about because of the Earth’s crucial 23.5° axial tilt. That is what causes the two different hemispheres to jut out at the Sun at different angles as the Earth completes its yearly orbit around the Sun. At the Winter Solstice the Northern Hemisphere is further from the Sun, so it takes longer for sunlight to reach it. The following pictures should remind you of what the seasons and the Solstices are all about.
So, join me in rejoicing. The shortest day is here. Summer is on the way.
P.S., That the stupid Mayan doomsday fell on the Solstice is not a coincidence.