Updated: Jan 26, 2022
A thru Z Astrology Series; E is for Equinoxes
"Equinox" means "Equal Night" and refers to the time of year when the length of Day and Night are equal. We have two equinoxes each year - one in the spring and one in the fall. These are related to the earth's tilt of axis, which gives us our seasons. When the Northern Hemisphere is tilted towards the sun, we have longer days and shorter nights - our summer. And when the Northern Hemisphere is tilted away from the sun, we have longer nights and shorter days - our winter. At the time of the equinox, Day and Night are equal and we are directly in between summer and winter.
A note on the Solstices
The tilt of the earth's axis has the Northern Hemisphere tilted farthest away from the sun at the time of the year when the sun enters Capricorn. In 6 months time, the tilt of the earth's axis will have the Northern Hemisphere tilted closest to the sun - this is the Summer Solstice and the beginning of Cancer season. We even have named certain parts of the Earth's circumference lines after these points; the Tropic of Capricorn and the Tropic of Cancer. The Equator is between the two - and it is the point tilted closest to the sun during the Spring and Fall equinoxes.
As we annually orbit around the sun, the moments of these seasonal shifts of the solstices and equinoxes make up the key points in our Astrological Calendar using Tropical Astrology. (Also known as Western Astrology) This is why the signs might have slightly different starting/ending dates each year - as the points of the solstices and equinoxes do not fall on the exact same calendar day every year.
Understanding this concept will also help you understand why Tropical Astrology does not align with the placement of constellations. The Astrological Year of Tropical Astrology is designed to line up with seasonal points of time in our orbit around the sun - not with the alignment of the sun with certain constellations. Sidereal Astrology sets the timing of the astrological seasons with the constellations - but not Tropical Astrology. I think both forms of astrology are valid and useful, but generally people will choose one or the other to study and practice. (I work with Tropical Astrology)
Tropical Astrology (in the Northern Hemisphere) 0° Aries - The Spring Equinox - The sun's ecliptic path is aligned with the Equator 0° Cancer - Summer Solstice - the sun's ecliptic path is aligned with the Tropic of Cancer 0° Libra - Fall Equinox - the sun's ecliptic path is aligned with the Equator 0° Capricorn - Winter Solstice - the sun's ecliptic path is aligned with the Tropic of Capricorn
From these points, each sign is divided into 30 degrees, making a 360° wheel equally divided among 12 signs.
These points of the Equinoxes and Solstices all fall in the Cardinal Signs. Cardinal Signs are related to Leadership and Initiation - so it makes sense that these four signs "lead" the change or initiation into each seasonal shift of the year.
As a side note - once you understand that Tropical Astrology (Western Astrology) is designed based on the division of 12 signs through the alignment of the sun's elliptical path with the equinox and solstice points - you understand why the "13th Sign" Ophiuchus is just not a thing. The basis for the 13th Sign of Ophiuchus is rooted in placement of a constellation along the elliptical path of the sun. The signs were named after nearby constellations, but the system of Tropical Astrology is not based only on constellations; it is much more based on the seasonal points of the year on earth. I don't know exactly why the ancient astrologers chose to name the season of Scorpio after the smaller constellation of the Scorpion rather than the larger constellation of Ophiuchus, but the existence of this constellation does not change the 12-sign system.
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