Solstices vs. Equinoxes: How Do They Differ?

This Saturday, March 20, we'll experience one of two annual equinoxes. For the Northern Hemisphere, it's the vernal equinox—the official start of spring—while the Southern Hemisphere will greet fall with the autumnal equinox.

Equinox is more than just a term for a seasonal transition. It originates from the Latin word for equal night, highlighting the key event of the equinox: daylight and nighttime are approximately equal in length. Because Earth is tilted at about 2 degrees, the North Pole typically leans toward or away from the sun. When angled toward the sun, the Northern Hemisphere experiences longer daylight hours; when tilted away, nights are longer. The Southern Hemisphere experiences the opposite. However, twice annually, neither hemisphere tilts towards or away from the sun, resulting in roughly equal hours of day and night. During the equinox, the sun is directly overhead at the Equator.

Solstices occur when the poles are at their furthest and closest points to the sun. During the winter solstice in late December, the North Pole is angled farthest away, causing the Northern Hemisphere to experience its longest night. The sun shines directly over the Tropic of Capricorn, the southernmost latitude the sun strikes. According to Britannica explains, the reverse happens during the summer solstice in late June. The sun is directly above the Tropic of Cancer, the northernmost latitude, as the North Pole tilts toward the sun, giving the Northern Hemisphere the longest daylight of the year, while the Southern Hemisphere endures its longest night.