what is an equinox?
The instant of time when the plane of Earth's equator passes through the geometric center of the Sun's disk.
Equinox
An equinox is commonly regarded as the instant of time when the plane (extended indefinitely in all directions) of Earth's equator passes through the geometric center of the Sun's disk. This occurs twice each year, around 20 March and 23 September. In other words, it is the moment at which the center of the visible Sun is directly above the equator.
what type of path do planets follow around the sun orbit what is ecliptic? The ecliptic is the plane of Earth's orbit around the Sun. is there a celestial reference plane? The ecliptic forms one of the two fundamental planes used as reference for positions on the celestial sphere, the other being the celestial equator. what do you mean by the last term? The celestial equator is the great circle of the imaginary celestial sphere on the same plane as the equator of Earth. what do you mean by the plane of the solar system? Most of the major bodies of the Solar System orbit the Sun in nearly the same plane. This is likely due to the way in which the Solar System formed from a protoplanetary disk
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Equinox [SEP] Introduction
An equinox is commonly regarded as the instant of time when the plane (extended indefinitely in all directions) of Earth's equator passes through the geometric center of the Sun's disk. This occurs twice each year, around 20 March and 23 September. In other words, it is the moment at which the center of the visible Sun is directly above the equator. The word is derived from the Latin ', from ' (equal) and ' (genitive ') (night). On the day of an equinox, daytime and nighttime are of approximately equal duration all over the planet. They are not exactly equal, however, due to the angular size of the Sun, atmospheric refraction, and the rapidly changing duration of the length of day that occurs at most latitudes around the equinoxes.