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Dynamics of the Solar SystemEquinoxesMarch observancesSeptember observances

Equinox

Adapted from Wikipedia · Explorer experience

A satellite view of Earth showing the moment of the September 2022 equinox, when day and night are nearly equal around the world.

An equinox is a special moment in the year when the Sun is right above the Earth's middle line, called the equator. This only happens when the Earth is not tilted toward or away from the Sun.

We have two equinoxes every year, around 20 March and 23 September. The word "equinox" comes from Latin words that mean "equal night." On these days, nighttime and daytime are almost the same length everywhere.

In the Northern Hemisphere, the March equinox starts spring, and the September equinox starts autumn. In the Southern Hemisphere, it is the other way around. People have known about equinoxes for a long time because they help us understand the changing seasons.

During an equinox, the Sun rises in the east and sets in the west for everyone on Earth. This happens because the Sun is straight above the equator. Equinoxes are special times that show how the Earth moves around the Sun.

Images

A stunning view of the Crab Nebula, the remains of a star that exploded long ago, showing colorful clouds of gas and light from space.
Illustration showing Earth during the four astronomical seasons as seen from the north.
A beautiful sunset in Antarctica showing bright pillars of light in the sky, created by natural optical effects.
Diagram showing how the Sun lights up Earth equally during the equinox in March and September.
Diagram showing the path of the Sun across the sky as seen from Earth, helping us understand how the Earth orbits the Sun.
An illustration showing the Earth at the beginning of each of the four astronomical seasons, viewed from space.
A stunning view of the planet Saturn, its rings, and several of its moons captured by the Cassini spacecraft from orbit around Saturn.
A stunning view of Earth rising over the Moon, taken by astronauts during the Apollo 8 mission in 1968.
Map showing the International Date Line and the 180th meridian in the Aleutian Islands region.
An artist's depiction of HE 1523-0901, one of the oldest known stars in our galaxy, located about 7,500 light-years from Earth.

This article is a child-friendly adaptation of the Wikipedia article on Equinox, available under CC BY-SA 4.0.

Images from Wikimedia Commons. Tap any image to view credits and license.