Napéjegyenlség

Napéjegyenlség, often translated as equinox, refers to the two days in the year when the Sun is directly above the Earth's equator. This celestial event occurs around March 20th or 21st and September 22nd or 23rd. During an equinox, the length of day and night is approximately equal across the globe, lasting about twelve hours each. This phenomenon is a result of the Earth's axial tilt.

As the Earth orbits the Sun, its axis remains tilted at approximately 23.5 degrees relative to its orbital plane. This tilt causes different hemispheres to receive more direct sunlight at different times of the year, leading to the seasons. However, during the equinoxes, the Earth's tilt is neither towards nor away from the Sun. This alignment means that both the Northern and Southern Hemispheres receive an equal amount of solar illumination.

The vernal equinox in March marks the beginning of spring in the Northern Hemisphere and autumn in the Southern Hemisphere. Conversely, the autumnal equinox in September signifies the start of autumn in the Northern Hemisphere and spring in the Southern Hemisphere. The word "equinox" itself comes from Latin words "aequus" meaning equal, and "nox" meaning night, reflecting the equal duration of day and night.