Definition
An equinox is when the Sun crosses the celestial equator. This happens twice a year, resulting in nearly equal day and night lengths worldwide. Think of it as a balanced cosmic moment. It marks the transition between seasons. The vernal equinox signals the start of spring, while the autumnal equinox marks the beginning of autumn. The Earth is neither tilted towards nor away from the Sun. During an equinox, days and nights are near equal.