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| Description: Ancient Astronomy Ancient Greeks Used philosophical arguments to explain natural phenomena Also used some observational data Most ancient Greeks held a geocentric (Earth-centered) view of the universe “Earth-centered” view Earth was a motionless sphere at the center of the universe Stars were on the celestial sphere Transparent, hollow sphere Celestial sphere turns daily around Earth Seven heavenly bodies (planetai) Changed position in sky Seven wanderers Sun Moon Mercury Venus Mars Jupiter Saturn Ancient Greeks Aristarchus (312–230 B.C.) was the first Greek to profess a Sun-centered, or heliocentric, universe Planets exhibit an apparent westward drift Called retrograde motion Occurs as Earth, with its faster orbital speed, overtakes another planet Ptolemaic system A.D. 141 Geocentric model To explain retrograde motion, Ptolemy used two motions for the planets Large orbital circles, called deferents, and Small circles, called epicycles Picture Stats: Views: 753 Filesize: 545.3kB Height: 822 Width: 1036 Source: https://biology-forums.com/index.php?action=gallery;sa=view;id=39643 |