ASTRON 103 Chapter Notes - Chapter 11: Retrograde And Prograde Motion, Celestial Equator, Geocentric Model
5 Oct 2016
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Their own orbital motion around the sun: always remain within narrow band on either side of the ecliptic (within zodiac) Because orbits all lie in nearly the same plane. Shift n & s of celestial equator because ecliptic is tilted by 23. 5 . Move west to east (normally: because their movement across the celestial sphere is slower than the effect of. Retrograde motion: retrograde motion: when a planet moves westward instead of eastward. Planets appear to switch direction when the earth overtakes & passes them. Motion / path of the planet through stars zigzags or loops backward for a month or more. Geocentric model: earth at the center of the universe: eudoxus (400-347 b. c. e) created a model. A new model explaining retrograde came later - crystalline sphere. Ptolemy"s model: claudius ptolemy: roman astronomer who developed a geocentric model of. B. the solar system that could predict most of the observable motions of the planets.
