December 21: Winter and Summer Solstices

December 21st marks the winter solstice in the northern hemisphere. This astronomical event represents the time of the year when the path traveled by the sun is the farthest away from the northern part of the globe. Because the sun is traveling the shortest path through the sky, this is the day with the longest night in the year.

The figure below shows the earth’s orbit around the sun. On the right side, we can see that the earth’s inclination during the winter solstice causes the sun rays to shift southward, being directly overhead at the Tropic of Capricorn. After the winter solstice, the sunlight starts to increase again.

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Winter solstice, 2017

During this time of the year, we have cold, snow, hot beverages, family gatherings, holiday decorations… However, we can see by the figure above that while the sun rays are the farthest away from the northern hemisphere, they are the closest to the southern hemisphere. Our winter solstice is the summer solstice in the southern part of our planet. So how different is this time of the year south of the Equator?

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