Equinox and Solstices

Ecliptic is the earths orbit around the sun

Celestial equator is a circle that bands the sphere of the Earth at it’s thickest point, defining 0° of terrestrial latitude. The Equator separates the northern hemisphere from the southern hemisphere. The Equator is perpendicular to the Earth’s Axis of Rotation. The Earth spins on its Axis of Rotation once a day. Equator is tilted 23 1/2° with respect to the Ecliptic.

The Earth’s rotation “wobbles” during the year between the Tropic of Cancer and Tropic of Capricorn. This is what causes the seasons.

In the spring: Vernal Equinox. The Earth axis of rotation is perpendicular to the Sun and perpendicular to the Line of Intersection between the Ecliptic and the Celestial Equator.

90-degrees and 3 months later we have Summer Solstice where Earth’s axis of rotation is tilted towards the Sun (Tropic of Cancer), and is aligned with the Line of Intersection. We have summer and the longest day in the Northern Hemisphere. This is opposite in the Southern Hemisphere where there will be Winter and the shortest day.

Another 90-degrees of orbit and we have Autumnal Equinox with Earths’ axis of rotation similar as at Vernal Equinox, but with the “other” side of the earth facing the sun.

Lastly, after another 90-degree of orbit we have Winter Solstice where Earth’s axis of rotation is tilted away from the Sun (Tropic of Capricorn), and we get the shortest day and Winter in the Norther Hemisphere and Summer and longest day in the Southern Hemisphere.

Equinox means that the day and night are of equal length all over the Earth.

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