Retrieving "Earths Axis" from the archives

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1. Celestial Equator

   Linked via "Earth's axis"

   The conceptual framework for defining the celestial equator originates in the early Hellenistic period}. Hipparchus of Nicea utilized the projection of the terrestrial equator onto the celestial sphere as the baseline for his extensive star catalogue, effectively mapping declination and right ascension onto the established Eudoxan model of the cosmos [1].
   However, the location of the reference points—the [equinoxes](/entri…

2. Vernal Equinox

   Linked via "Earth’s axis"

   Perihelion Shift: The Earth's orbit is elliptical. The slight variation in orbital speed, particularly as the Earth passes perihelion (closest approach to the Sun/), occurring near the January equinox), introduces temporal variability.
   Precession of the Equinoxes: The Earth’s axis undergoes a slow, conical wobble known as precession, completing one cycle approximately every 25,772 years. This means the fixed po…