Equinoxes happen twice a year when our Sun crosses Earth’s Celestial Equator.
This is when the centre of our Sun is on exactly the same plane as Earth’s equator. The Earth’s axis isn’t tilted toward the Sun one way or the other and the hours of night and day are almost equal in length.
By the way, the Celestial Equator is just a projection of Earth’s equator onto the imaginary sphere that we picture surrounding our planet when we look up at the night sky. This imaginary sphere is called the Celestial Sphere.
Interesting facts about Equinoxes
- There are two equinoxes every year.
- In the Southern Hemisphere, the equinox in marach is sometimes called the autumnal equinox and the equinox in September can be called the vernal or spring equinox.
- In the Northern Hemisphere, the names of the equinoxes are reversed.
- The Sun is half way between its most southern position in the sky and its most northern position.
- At equinox, sunrise is due east and sunset is due west.
- The number of daylight hours is almost equal to the number of hours of darkness.
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