Who Were the Sea Peoples?

Stark ( Bearing False Witness ) seems to think that Copernicus had to introduce “loops” (epicycles) into the planets' circular orbits to get the orbital period correct: “it would not do for the earth to circle the sun in only three hundred days” (151). This is silly: one can always change the diameter or speed of a circular orbit in one's model and thus get the orbital period correct. The real problem with positing circular orbits instead of the actual elliptical ones has to do with the relationship of different parts of a planet's orbit, as can be seen with a visual representation: In the portions of a planet's orbit where the ellipse if flatter than a circle, the planet will appear to move too fast for it to have a circular orbit. And in the portions of its elliptical orbit where the ellipse is more curved than a circle, the planet will appear to move too slowly . So the actual problem with Copernicus's system (and Ptolemy's) is not that circular orbi...

He preferred Coperican orbits to Ptolemaic because... well, let's have him tell us: "If God... had wanted the planets to execute spirals... he could have easily brought it about... "[But] what would God have preferred: that the planets should fly about in composite, ever-changing, and irregular curved motions... or that each should describe a circle, uniform and regular as possible...? There is no one who philosophizes soberly who would not affirm the latter opinion and altogether reject the former." -- quoted in Howard Margolis, It Started with Copernicus , p. 91 So, a major reason for Galileo's scientific choice here was his contemplation of what God would have preferred .