AS101 Lecture Notes - Lecture 4: Ptolemy, Circular Motion, Retrograde And Prograde Motion
Document Summary
Many ancient civilizations used astronomy to help with their lives, astronomy could be used to help grow crops, predict flooding etc. People have been studying the sky for thousands of years. Ancient greek scientists started to think that the earth was a sphere and began to test this theory. Greeks believed that heavenly objects moved on circular paths at constant speed, with earth being motionless at the centre of the universe: aristotle mainly created this model. Planets seemed to follow complicated paths in the sky, including episodes of retrograde motion that are difficult to explain in terms of motion on circular paths at constant speeds. Claudius ptolemy created an elaborate geometrical and mathematical model to explain details of the observed motions of the planets, while assuming earth was motionless at the centre of the universe. First principle: something that seems obviously true and needs no further explanation. Believed as a first principle that the heavens were perfect.
