How did Aristotles ideas of motion explain planetary motion?
buildToggle(‘a10’); Answer Planets orbited the Earth on combinations of rotating transparent, crystalline spheres. They were beyond the sub-lunary sphere thus all their motion was circular and “unforced”. • Suggest a reason why Aristotle’s model was able to be incorporated into Western Christian theology. buildToggle(‘a11’); Answer Aristotle had the Earth at the centre of the Universe, that is a “special place”. The heavens were perfect and unchanging whilst Earth was subject to decay and corruption. • What device/s did Ptolemy use to explain retrograde motion? buildToggle(‘a12’); Answer Ptolemy used a combination of epicycles and deferents to explain retrograde motion. The diagram below shows this: A planet orbits point x in a circular path called the epicycle. The deferent is the circular path that point x takes around the centre of motion, C. Credit: R. Hollow CSIRO • State three reasons why Ptolemy’s model lasted for so long. buildToggle(‘a13’); Answer • It worked, ie it could be u
