Winter Solstice 2011: Shortest Day of the Year Thursday
Today marks the winter solstice of 2011, the shortest day of the calendar year with fewer hours of daylight for those living in the northern hemisphere.
Also known as the December solstice, the event took place Thursday at 12:30 a.m. EST. To those in the southern hemisphere Thursday marked the Summer solstice, and the longest day of the year in terms of daylight hours. This is because the sun is directly overhead on the Tropic of Capricorn in the southern hemisphere.
In the northern hemisphere, those traveling north of the Arctic Circle towards the North Pole will not be able to see the sun during this time of year. This is because the North Pole is tilted furthest away from the sun at the solstice.
On the contrary, those living or traveling south from the Antarctic Circle towards the South Pole will be able to see the midnight sun during this time of year.
The Winter solstice occurs when the sun reaches its most southern position at -23.5 degrees. In other words, it is when the North Pole is tilted 23.5 degrees away from the sun.
As of Thursday, all places above the latitude of 66.5 degrees north (Arctic Polar Circle) are now in 24-hour darkness. However, places below the latitude of 66.5 degrees south (Antarctic Polar Circle) are experiencing 24-hour sunlight.
The Winter solstice normally takes place on Dec. 21 or Dec. 22 in the Gregorian calendar.
The event has not fallen on Dec. 23 since 1903 and will not occur on this date again until the year 2303, according to timateanddate.com. Even more rare is a December solstice falling on Dec. 20. The next one will occur in the year 2080, according to the Gregorian calendar.
Because the earth does not move at a constant speed in its elliptical orbit, each season is not equal in length. As a result, spring and summer are longer than autumn and winter in the northern hemisphere.