What Is Equinox?
The two days each year, around March 20 and September 22, when day and night are about equal everywhere and the Sun is straight over the equator. In technical terms: The instant when the subsolar point crosses the equator, near March 20 and September 22-23; day and night are nearly equal worldwide, with daylight slightly longer than 12 hours due to refraction and the Sun's finite disk.
Also called: Vernal Equinox, Autumnal Equinox
Equinox In Plain English
The two days each year, around March 20 and September 22, when day and night are about equal everywhere and the Sun is straight over the equator.
The Technical Definition
The instant when the subsolar point crosses the equator, near March 20 and September 22-23; day and night are nearly equal worldwide, with daylight slightly longer than 12 hours due to refraction and the Sun's finite disk.
Lessons That Use Equinox
- Why We Have Seasons Unit 2: Energy And The Sun
