Equinox

Astrophysical Concepts

An equinox is the moment when the Sun appears directly above Earth's equator. It occurs twice yearly, around 20 March and 23 September, when the Sun rises almost exactly in the east and sets almost exactly in the west. Day and night are approximately equal in duration worldwide, though not exactly equal because of the Sun's angular size, atmospheric refraction, and changing day length. The March and September equinoxes have opposite seasonal names in the two hemispheres.

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Frequency: Twice each year, around 20 March and 23 September
Astronomical definition: Sun's apparent geocentric longitude is 0° or 180°
Day and night: Approximately equal in duration worldwide

Sources and credits

Article: Equinox (English Wikipedia)
Wikidata: Q1315
Text: Card text is adapted from the English Wikipedia article by an automated summary. Wikipedia content is available under CC BY-SA 4.0; see the article history for its contributors. CC BY-SA 4.0 · Article history and contributors
Illustration: AI-generated illustration. Not a photograph or documentary image. (model: gpt-image-2.5-flare)
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