The Geocentric Model, which posits that the Earth is at the center of the universe and all celestial bodies revolve around it, primarily depicts planetary orbits as circular. This model, advocated by thinkers like Ptolemy, struggled to explain the observed retrograde motion of planets without the use of complicated mechanisms such as epicycles.
In contrast, the Heliocentric Model, proposed by Copernicus and later supported by observations from Kepler and Galileo, places the Sun at the center of the solar system. This model acknowledges that the orbits of the planets are elliptical rather than circular, a characteristic quantitatively described by Kepler's First Law of Planetary Motion.
In summary:
- Geocentric Model: Circular orbits
- Heliocentric Model: Elliptical orbits
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