Fratelli's model of the star system, specifically as it relates to the appearance and movements of the planets, seems to be an amalgamation of various ancient and philosophical concepts, but it doesn't directly correspond to any widely recognized model. However, I can clarify concepts from similar astronomical frameworks, particularly those of Aristotle and later models influenced by Ptolemy.
Aristotle's Model:
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Crystalline Spheres: Aristotle posited that the stars and planets were fixed to concentric crystalline spheres. Each sphere rotated around the Earth, which was the center of the universe. This framework was geocentric, meaning it placed Earth at the center of all celestial motion.
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Planetary Motion: In this model, the planets moved in circular orbits within their respective spheres. These motions were explained by the rotation of the spheres themselves, which accounted for the apparent changes in speed and direction as observed from Earth.
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Natural Philosophy: In Aristotelian thought, celestial bodies were composed of aether (the fifth element), which was different from the terrestrial elements (earth, water, air, fire). Therefore, they were believed to have a different nature, leading to their perfect circular motions.
Ptolemaic Model (Later Addition):
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Epicycles: While Aristotle's model maintained the idea of circular motion and crystalline spheres, Ptolemy introduced the concept of epicycles—small circles upon which a planet moved, while the center of that circle moved along a larger circle (the deferent). This helped explain the retrograde motions of the planets.
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Nested Spheres: The idea of nested spheres also came into play in Ptolemy’s model as a means to account for the observed complexities of planetary motion.
In Summary:
- The planets were thought to be attached to crystalline spheres (in Aristotle's view) or moved along intricate paths created by epicycles (in Ptolemy's view).
- Changes in appearance, such as brightness and position, were due to the relative motion of the spheres or the combination of motions in the nested systems.
- The fixed nature of the stars and planets in these models was foundational for understanding the cosmos until the heliocentric model proposed by Copernicus and later refinements by Kepler and Newton revolutionized our understanding of celestial mechanics.
If "Fratelli" was intended to refer to a different model or theory not addressed here, please clarify, and I can offer more specific information!