AstroPhysics16 - Sun and three extra spheres for each...

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Greek Astronomers • Thales (624-546 BC) proposed the first known model of the Universe • Anaximander (610-546 BC) Earth floats in empty space, surrounded by stars and two rings on which the Sun and the Moon travel. He is credited for inventing the celestial sphere. He imagined the earth to be cylindrical • Pythagoras (560-480 BC): earth was round. This was confirmed by Aristotle a century later by observing shadow of earth during lunar eclipse • Plato (428-348 BC) asserted that heavenly motions were in perfect circles • Eudoxus (400-347 BC): Earth-centered Geocentric model with 8 co-rotating. Spheres were all aligned differently to give motions in agreement with observations. Needed two extra spheres for Moon and
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Unformatted text preview: Sun and three extra spheres for each planet for retrograde motion. Total of 27 spheres. Aristotle (384-322 BC) postulated gravity and physical laws of motion Aristotles Cosmology: Two worlds: heavenly ether and sub-lunar Earth, Water, Air and Fire. Introduced 56-sphere geocentric model but still in error. He couldnt explain variation in Moons size and variation in planets brightness but his model that Earth is in the center of the Universe stood for 2000 years. After Aristotle, the models became more quantitative. Eratosthenes (300 BC): measures size of Earth to 1% accuracy....
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AstroPhysics16 - Sun and three extra spheres for each...

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