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Autumnal Equinox Facts

Twice a year, both periods of day and night are equal length because the sun is situated directly over the equator during the autumnal equinox. 

This phenomenon occurs in the Northern Hemisphere on September 22 and 23, while it occurs in the Southern Hemisphere on March 20 and 21.

Autumnal Equinox Facts for Kids

  • It marks the change of seasons from summer to fall in the northern hemisphere
  • It marks the change of seasons from winter to spring in the southern hemisphere.
  • In the southern hemisphere, the autumnal equinox is referred to as vernal equinox.
  • As autumn approaches, the days become shorter.
  • In Latin, the word equinox means ‘equal’ and ‘night’.
  • Harvest Moon is the full moon close to the autumnal equinox.
  • China celebrates the autumnal equinox with a festival called the Mid-Autumn Festival (or Moon Festival).

What Causes the Equinox

Earth’s axis is tilted at 23.5 degrees, so the hemispheres lose their warmth when they tilt away from the sun. 

Because of the axial tilt and Earth’s orbit, the sun sits directly above the celestial equator at certain times of the year. This usually happens twice a year.

We see a terminator or twilight zone through the North and South Poles when equinoxes occur. A terminator, or twilight zone, is a line divided between the day and night sides of a planet.

During the autumnal equinox, the sun’s rays are less direct, resulting in colder temperatures.

Other than Earth, every planet in our solar system has seasons.

What Is an Equinox?

“Equinox” comes from the Latin aequus, which means equal, and nox, which means night. The Solar equinox marks when the Sun crosses an imaginary line that is analogous to the equator on Earth. The equinox occurs precisely when the Sun passes through this line. 

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The autumnal equinox is when the Sun crosses the equator from north to south. The vernal equinox marks this change from south to north. During autumn, the Sun rises later, and the nightfall comes earlier. The December Solstice is the day when days get longer and nights get shorter.

Autumnal Equinox Celebrations Around the World

Throughout ancient times, many cultures celebrated the autumnal equinox. 

A passage and chamber in Newgrange in Ireland are illuminated by the Winter Solstice sun. An opening on top of the mound is called the roof-box. Near the winter solstice, a beam of light pierces the roof and travels up the 19-meter passage and into the chamber. During the early morning hours, the beam widens, illuminating the entire chamber.

In pagan mythology, the equinox marks the beginning of the harvest festival, Mabon. During this period, Pagans also prepare for the coming of winter with a bigger festival called Samhain.

Japan’s Buddhists view this period (Ohigan) as a celebration of the afterlife and visit the graves of ancestors.

Ancient Mesopotamian civilizations existed roughly two thousand years ago near Chankillo, Peru. Its 13 aligned towers track the sun during equinoxes and solstices.

During this period, China and Vietnam celebrate Mid-Autumn Festival or Moon Festival. This lunar calendar-based holiday occurs during the 8th lunar month. Eating mooncakes is a traditional thing during this festival.

During each equinox, Neo-Druids travel to Stonehenge to reminisce about the harvest and prepare for the winter.

In ancient Greece, the gods Dionysus and Apollo were honored during the season.

The sun pyramid at Teotihuacan became the main ceremonial center during the equinox in Mesoamerican history.

As queen of the underworld, Persephone was married to Haides (Hades). Her mother, Demeter, was also worshipped alongside the goddess of spring growth Hera in the Eleusinian Mysteries. Cora tells the story of Persephone being abducted by Hades to the underworld. Demeter is able to save her daughter, but only for nine months. Every fall, Persephone returns to Hades in the underworld to spend three months with him.