Autumnal equinox

Autumnal Equinox

The autumnal equinox is one of two points in the Earth's orbit where the sun is exactly above the equator. It marks the beginning of autumn in the Northern Hemisphere and spring in the Southern Hemisphere. The term "equinox" comes from the Latin words "aequus" (equal) and "nox" (night), referring to the nearly equal length of day and night that occurs on the equinox.

Astronomical Significance

During the autumnal equinox, the sun crosses the celestial equator from north to south. This event occurs annually around September 22nd or 23rd in the Northern Hemisphere and around March 20th or 21st in the Southern Hemisphere. The exact date and time of the equinox vary each year and can be calculated using astronomical data.

Cultural Significance

The autumnal equinox has been celebrated by various cultures throughout history. In many cultures, it is associated with the harvest season. For example, in Japan, the autumnal equinox is a national holiday known as "Shūbun no Hi", which is part of a seven-day period known as "Higan" during which people pay respects to their ancestors.

Scientific Observations

The autumnal equinox provides a unique opportunity for scientific observations. For instance, it is the only day of the year when the sun rises due east and sets due west for all locations on Earth (except at the poles). This phenomenon can be used to determine due east and west in navigation.

See Also

• Vernal Equinox
• Solstice
• Seasons