Fact Sheet
Solstices and Equinoxes
Because Earth orbits the Sun, we see different constellations throughout the year. And the Sun (if it were visible at night) appears to move through a stationary starry background. The Sun's apparent path through the stars, over the course of one year, forms a circle called the ecliptic. Twice each year, the Sun's path path crosses the celestial equator (Earth's equator projected onto the sky). At these times, night and day are of equal length. These dates are called equinoxes -- the Latin word for "equal night." Solstices -- Latin for "standing Sun" -- occur when the Sun is at its highest point above the celestial equator (summer solstice, the longest day of the year) and the lowest point below it (winter solstice, the shortest day of the year).
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