Solstices

There are two days during which one of the poles points directly at the sun: June 21 and December 21. These days are called solstices. There is a summer solstice and a winter solstice for each hemisphere.

About June 21, the North Pole points directly at the sun. On this day, the Northern Hemisphere experiences its longest day of the year––the first day of summer, or the summer solstice––and the sun's rays directly hit the earth at the Tropic of Cancer. In the Southern Hemisphere, June 21 is the first day of winter, or the winter solstice. At that time the Arctic Circle receives constant daylight; there is no night! On the other hand, the Antarctic Circle receives no daylight at all on June 21, and it is the shortest day of the year for the Southern Hemisphere. As the earth continues its orbit and the angle of the earth towards the sun changes, the days in the Southern Hemisphere lengthen, while the days in the Northern Hemisphere become shorter.

About December 21, the South Pole points directly at the sun. Which season do you think begins in the Southern Hemisphere on that day? It is the first day of summer, or the summer solstice, and is the longest day of the year. On this same day it is the beginning of winter, or the winter solstice and the shortest day of the year, in the Northern Hemisphere. On this day the sun's rays directly hit the earth at the Tropic of Capricorn.

There are also two equinoxes each year. These are the days when both poles are at a 90º angle from the sun; both hemispheres receive an almost equal amount of solar energy on those days, and daylight lasts about twelve hours all over the earth. The equinoxes usually occur on March 21 and September 22. In the Northern Hemisphere, March 21 is the spring equinox and September 22 is the fall equinox. As you can probably guess, the spring equinox in the Southern Hemisphere is September 22 and the fall equinox is March 21.

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