People discovered that the periods of sunlight and darkness were variable many millennia ago, as soon as they had the earliest timekeeping tools. So they also discovered that twice during the year, the days and nights were of equal length. That's the "equinox".
The Equinox itself was not "discovered," as it is a natural phenomenon that occurs twice a year when the plane of the Earth's equator passes the center of the sun. The understanding of the Equinox and its significance in marking the changing seasons has been known since ancient times by various civilizations.
fall equinox partial equinox
The autumnal equinox is also known as the fall equinox and the September equinox. An example of a sentence using "autumnal equinox" is "This year's autumnal equinox falls on a full moon. "
The Autumn equinox.
No. Equinox is a noun.
The spring equinox is March 21, The fall equinox is September 23
The vernal equinox is also known as the spring equinox.
There is 1 day for each equinox: the vernal equinox in spring and the winter equinox in winter.
Spring equinox occurs around March 20 and Fall equinox occurs around September 22 for the Northern Hemisphere. For the Southern Hemisphere these dates are opposite; the Spring equinox is around September 22 and the Fall equinox occurs around March 20.
the march equinox
A synonym of equinox is aphelion.
the spring equinox is in spring.