The December solstice will occur at 17:47 (or 5.47pm) Coordinated Universal Time (UTC) on December 21, 2009. It is also known as the winter solstice in the northern hemisphere and the summer solstice in the southern hemisphere due to the seasonal differences. Its date varies from December 20 to December 23 depending on the year in the Gregorian calendar.
To find the December solstice date in other time zones or other years, please use the Seasons Calculator.
The December Solstice Explained
The December solstice occurs when the sun reaches its most southerly declination of -23.5 degrees. In other words, it is when the North Pole is tilted 23.5 degrees away from the sun. Depending on the Gregorian calendar, the December solstice occurs annually on a day between December 20 and December 23. On this date, all places above a latitude of 66.5 degrees north are now in darkness, while locations below a latitude of 66.5 degrees south receive 24 hours of daylight.
The sun is directly overhead on the Tropic of Capricorn in the southern hemisphere during the December solstice. It also marks the longest day of the year in terms of daylight hours for those living south of the Tropic of Capricorn. Those living or travelling south from the Antarctic Circle towards the South Pole will see the midnight sun during this time of the year.
On the contrary, for an observer in the northern hemisphere, the December solstice marks the day of the year with the least hours of daylight for those living north of the Tropic of Cancer. Those living or traveling north of the Arctic Circle towards the North Pole will not be able to see the sun during this time of the year.
December solstice in relation to seasons
It is important to note that earth does not move at a constant speed in its elliptical orbit. Therefore the seasons are not of equal length: the times taken for the sun to move from the vernal equinox to the summer solstice, to the autumnal equinox, to the winter solstice, and back to the vernal equinox are roughly 92.8, 93.6, 89.8 and 89.0 days respectively. The consolation in the northern hemisphere is that spring and summer last longer than autumn and winter (when the December solstice occurs).
The relative position of the earth’s axis to the sun changes during the cycle of seasons. This phenomenon is the reason why the sun’s height above the horizon changes throughout the year. It is also responsible for the seasons through controlling the intensity and duration of sunlight received at various locations around the planet.
Tags: Interesting, Science
