The Universe of - sphere of the stars lay beyond the ones...

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The Universe of Aristotle and Ptolemy The celestial sphere that we introduced previously is a convenient fiction to locate objects in the sky. However, the Greek philosopher Aristotle (many of Aristotles works are available at the Internet Classics Archive ) proposed that the heavens were literally composed of 55 concentric, crystalline spheres to which the celestial objects were attached and which rotated at different velocities (but the angular velocity was constant for a given sphere), with the Earth at the center. The following figure illustrates the ordering of the spheres to which the Sun, Moon, and visible planets were attached. (The diagram is not to scale, and the planets are aligned for convenience in illustration; generally they were distributed around the spheres.) There were additional "buffering" spheres that lay between the spheres illustrated. The
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Unformatted text preview: sphere of the stars lay beyond the ones shown here for the planets; finally, in the Aristotelian conception there was an outermost sphere that was the domain of the "Prime Mover". The Prime Mover caused the outermost sphere to rotate at constant angular velocity, and this motion was imparted from sphere to sphere, thus causing the whole thing to rotate. By adjusting the velocities of these concentric spheres, many features of planetary motion could be explained. However, the troubling observations of varying planetary brightness and retrograde motion could not be accommodated: the spheres moved with constant angular velocity, and the objects attached to them were always the same distance from the earth because they moved on spheres with the earth at the center....
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This note was uploaded on 12/04/2011 for the course ANT ANT2000 taught by Professor Monicaoyola during the Fall '10 term at Broward College.

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The Universe of - sphere of the stars lay beyond the ones...

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