 |
|
 |
|
Dr Robert A. Hatch - University of Florida
|
|
|
|
| The most influential geometrical astronomer of antiquity was undoubtedly Claudius Ptolemy (fl. 140 AD). All of Ptolemy's planetary models were geocentric (earth-centered) and geostatic (earth-stationary) and assumed a finite cosmos. But unlike Aristotle, Ptolemy was primarily interested in providing good geometrical descriptions. He appears to have been less concerned with developing a plausible physical, real, causal cosmology. Rather, Ptolemy sought to 'save the appearances.' All evidence indicates his principal concern was to supply geometrical means to describe and predict planetary motions. Astronomy was geometry. It was a means to an end, an 'instrumental' form of knowledge designed to provide positive, practical results. Or so the story goes. There is some evidence, notably in his Planetary Hypotheses, that Ptolemy wished to go beyond mere geometrical, astronomical description into the more risky business of real, physical, causal cosmology. The above illustration shows part of Ptolemy's model conceived as substantial circles moving inside other circles. Here Ptolemy in some sense reified the otherwise abstract geometrical circles, the deferents and epicycles. This illustration appeared in Boulliau's Philolaus (Amsterdam 1639). For other illustrations and applications of Ptolemy's Model Click Here. |
rah.jan.99
|
|
Copyright 1998 - Dr Robert A. Hatch - All Rights Reserved