What precisely defines the Ecliptic's path traced by the Sun on the celestial sphere?
Answer
The imaginary projection of the Earth's orbital plane onto the celestial sphere.
The ecliptic is fundamentally an imaginary line, not a physical track in space. It represents the geometric intersection formed when the plane containing the Earth's annual orbit around the Sun is mapped or projected onto the celestial sphere—the apparent dome surrounding Earth. As the Earth revolves around the Sun over the course of a year, this constant change in our viewing perspective causes the Sun to appear to drift eastward along this specific great circle path against the background of distant stars. This projection is the operational definition used in spherical astronomy to describe the Sun's apparent annual motion.
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