On the “Hippopede” of Eudoxus
FEW astronomical theories have exercised so deep and lasting an influence on human thought as the discovery of Eudoxus that the motion of the planets can be explained, at least qualitatively, as the combination of uniform rotations of concentric spheres about inclined axes. The sphericity of the universe, the fundamental importance of uniform circular motion, must have appeared from then on as an established fact. Combined with Aristotle’s idea of the “prime mover” the universe could be understood as one great system, truly geocentric. No wonder that this theory held its fascination for almost two thousand years over the minds of philosophers and even astronomers, in spite of the fact that serious difficulties were apparent almost from the start. The theories developed by specialized astronomers, like Hipparchus or Ptolemy, had to their credit a far superior agreement with the observational data. Nevertheless, the deeply rooted human conviction that simplicity and beauty are criteria of truth kept the hope alive that the homocentric spheres, albeit in some modification, may represent correctly the plan of the creator.
KeywordsHorizontal Plane Incline Plane Concentric Sphere Planet Move Uniform Rotation
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