Winter solstice

by Toby Swaford, K-12 Education Coordinator

The Winter Solstice usually occurs on December 21st or 22nd in the Northern Hemisphere. Described as the first day of winter, the solstice is caused by the Earth’s tilted axis (roughly 23.5 degrees) as it orbits around the sun. This is the phenomenon that causes both the change of seasons and the amount of sunlight we receive each day. Speaking of which, the Winter Solstice is often described as the shortest day of the year, although it technically still has 24-hours in it. Granted most of those hours are a little on the dark side (at least for those of us in the Northern Hemisphere), with sunrise occurring around 7:30 AM, and the sun setting just nine hours later at 4:30 PM.

During the late fall and early winter, the sun seems to hang lower on the horizon than at any other time of the year, due to the Northern Hemisphere being tilted away from the sun at its most extreme angle during our year long journey around the solar system. Conversely, the Summer Solstice takes place when the North Pole is angled closer to the sun, giving us the maximum amount of daylight we’ll get all year.

The term solstice is derived from the Latin, translating as the “sun stands still.” If you watch the sun rise and set over the next few days, these events will seem to take place in the same two parts of the sky each day. This stability is short lived and in the next few weeks the daylight will begin to last a bit longer. This occurrence held special meaning for many of the cultures found throughout the Northern Hemisphere and is the basis for the myriad of winter holidays celebrated today.


December 2009
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