The Longest and Shortest Days of the Year
Solstice and Equinoxes
The Earth's orbit around the Sun causes the seasons. As the Earth orbits, its axis is tilted, which means that different parts of the Earth receive more or less direct sunlight at different times of the year. This tilt causes the solstices and equinoxes.
What is a Solstice?
A solstice is the day with the most or least amount of daylight during a year. The word "solstice" comes from the Latin words "sol" (sun) and "sistere" (to stand still). This is because, on the day of a solstice, the Sun appears to stop moving north or south in the sky for a few days before reversing direction.
In the Northern Hemisphere, the summer solstice occurs on or around June 21, and the winter solstice occurs on or around December 21. In the Southern Hemisphere, the summer solstice occurs on or around December 21, and the winter solstice occurs on or around June 21.
What is an Equinox?
An equinox is the day when the Sun crosses the celestial equator, which is an imaginary line that circles the Earth halfway between the North and South Poles. The word "equinox" comes from the Latin words "aequus" (equal) and "nox" (night). This is because, on the day of an equinox, the length of day and night is approximately equal all over the world.
In the Northern Hemisphere, the spring equinox occurs on or around March 21, and the fall equinox occurs on or around September 21. In the Southern Hemisphere, the spring equinox occurs on or around September 21, and the fall equinox occurs on or around March 21.
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