In the description of Eudoxus’s model for the sun he says one the three circles which describe solar motion is “the circle which runs along the middle of the zodiac”. Does this refer to the ecliptic plane? What I thought is that it does mean the same thing as the ecliptic, which as seen from earth when looking up to the night sky, appears as if it cuts the zodiac in the middle. In a spherical model, the Sun’s apparent movement can be described as running along the constellations of the zodiac throughout the year on a “circle” which is known as the ecliptic.

Am I getting this wrong?

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    $\begingroup$ I don't want to make this an answer, as I'm not an expert, but I believe you're correct. The sun does move across the zodiac on the ecliptic plane as you said, unlike the planets which vary slightly off the ecliptic plane. Eudoxus said 3 spheres, not the 3 circles - minor nitpick. $\endgroup$ – userLTK Feb 5 at 3:30

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