Was Ptolemys Theory a Good Model by Modern Standards?
It had convincing strong points: • It fit all of the available data. • It predicted the earth was standing still, in agreement with observation (even though we now know that this observation was wrong). • It predicted approximately where the planets were found even centuries after Ptolemy died. Thus, it was a good scientific theory for its time. With 20/20 hindsight, it had some weaknesses too: • Its predictions tended to drift relative to reality and needed to be adjusted from time to time using more observations. • Was it the simplest possible model? (Modern scientists prefer theories with the fewest possible assumptions; this precept is called Occam’s razor).
