What is an equinox?

An equinox is an astronomical event that occurs twice a year when the plane of Earth’s equator passes through the center of the Sun, resulting in nearly equal day and night durations. The term “equinox” is derived from Latin, meaning “equal night,” reflecting the balanced distribution of sunlight during this time.

There are two equinoxes in a year, namely the Vernal Equinox and the Autumnal Equinox. The Vernal Equinox occurs around March 20th in the Northern Hemisphere, marking the beginning of spring. On this day, the Sun crosses the celestial equator from south to north, and day and night are approximately equal in length worldwide. Simultaneously, in the Southern Hemisphere, it is the beginning of autumn.

Conversely, the Autumnal Equinox occurs around September 22nd in the Northern Hemisphere, signaling the start of fall. During this equinox, the Sun crosses the celestial equator from north to south, again resulting in nearly equal day and night lengths globally. In the Southern Hemisphere, the Autumnal Equinox corresponds to the beginning of spring.

Equinoxes are important celestial events, influencing cultural traditions, calendars, and serving as crucial markers in understanding Earth’s axial tilt and its impact on the changing seasons.