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Sun reaches southernmost point at solstice

December 21, 2015. If you live in North America, the solstice comes for you on this date.

The December solstice is when the sun reaches its southernmost point for the year. In 2015, it happens at 4:48 Universal Time on December 22. That means that, here in North America, the solstice falls on December 21 at 11:48 p.m. EST, 10:48 p.m. CST, 9:48 p.m. MST and 8:48 p.m. PST. Translate to your time zone here.

Looking at the world map below, you can see that the 2015 December solstice happens at sunset in the Pacific Ocean, midnight in the Americas, sunrise in Africa and noontime in Asia.

Day and night sides of Earth on the December 2015 solstice

Day and night sides of Earth at the instant of the December 2015 solstice (2015 December 22 at 4:48 Universal Time). Note that the north polar region of Earth must endure 24 hours of night, while the south polar region gets to bask in 24 hours of daylight. Image credit: Earth and Moon Viewer

Day and night sides of Earth at the instant of the December 2015 solstice (2015 December 22 at 4:48 Universal Time). Note that the north polar region of Earth has 24 hours of night, while the south polar region basks in 24 hours of daylight. Image via Earth and Moon Viewer

On the December solstice, we celebrate the (unofficial) first day of winter in the Northern Hemisphere and first day of summer in the Southern Hemisphere. Unofficial? Yes. Winter and summer start at the solstices by tradition, not official decree.

Yet these solstices bring very real occurrences to our sky, which you can witness for yourself. In both the Northern and Southern Hemispheres, the December solstice brings the southernmost sunrise and the southernmost sunset of the year. If you stand in one spot day after day, week after week – for example, gazing out a window toward the sunrise or sunset on the horizon – you will surely notice the sunset’s northward trek along the horizon over the coming months. From time to time, try fixing a bit of tape to the window on which you’ve written the date, to help you mark the sun’s passage.

In the Northern Hemisphere, the southernmost sunrise and sunset usher in the year’s shortest day and the longest night. In the Southern Hemisphere, it’s the exact opposite, for the year’s southernmost sunrise and sunset give the Southern Hemisphere its longest day and shortest night.

Solstice tale of two cities

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Oliver Nagy made this cool image between the June and December solstices in 2014.  The camera was fixed to a single spot for the entire exposure time, and it continuously recorded the sun's path as glowing trail s across the sky.   The breaks and gaps between the lines are caused by clouds.  This image shows the shifting path of the sun over the months between a June and December solstice.  As seen from the Northern Hemisphere, the sun's path gets lower each day.

Oliver Nagy made this cool image between the June and December solstices in 2014. The camera was fixed to a single spot for the entire exposure time, and it continuously recorded the sun’s path as glowing trail s across the sky. The breaks and gaps between the lines are caused by clouds. This image shows the shifting path of the sun over the months between a June and December solstice. As seen from the Northern Hemisphere, the sun’s path gets lower each day.

Earth has seasons because our world is tilted on its axis with respect to our orbit around the sun. Image via NASA.

Not everyplace worldwide has a sunrise and a sunset on the day of the December solstice. North of the Arctic Circle – or north of 66.5o north latitude – there is no sunrise or sunset today, because the sun stays beneath the horizon all day long. South of the Antarctic Circle – at 66.5o south of the equator – you won’t see a sunrise or sunset either, because the sun stays above the horizon all day.

View larger. | 2004 December solstice as viewed at the Lawrence Hall of Science in Berkeley, California, USA. Photo via Wikimedia.

After the sun reaches its southernmost point on the sky’s dome on the December solstice, watch as the sun seems to pause for a number of days before it starts its northward trajectory on the sky’s dome once again.

Bottom line: In 2015, the December solstice comes on December 21 at 10:48 p.m. CST. That’s December 22 at 4:48 Universal Time. It’s when the sun on our sky’s dome reaches its farthest southward point for the year. At this solstice, the Northern Hemisphere has its shortest day and longest night of the year. Happy solstice, everyone!

Winter solstice from Stonehenge

For the Western Hemisphere, first full moon on Christmas since 1977

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Bruce McClure

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