Talk:Copernican heliocentrism
From Wikipedia, the free encyclopedia
[edit] Accuracy of the Copernican System
The article currently says "Copernicus' system was not experimentally better than Ptolemy's model". For any one planet, a geocentric system with one circular epicycle is exactly equivalent to a heliocentric system with circular orbits. However such a geocentric system allows two parameters for each orbit (the radius of the deferent and the radius of the epicycle) wheras the equivalent heliocentric system has only one parameter per orbit plus one for the system as a whole. On the face of it, under these circumstances, the geocentric system should produce more accurate predictions.
Actualy, both the geocentric and heliocentric systems were more complicated than this. Copernicus allowed more epicycles and Ptolomy allowed non-uniform motion (according to Gingerich). It seems likely to me that the non-uniform motion would still produce more accurate results. Anyone know whether this is true? Rjm at sleepers 07:59, 27 March 2007 (UTC)
[edit] Phases of Venus
This article and Gingerich both assert that observation of the phases of Venus provided a proof of heliocentrism. It seems to me that there would be phases of Venus on a geocentric system as well. Can anyone offer an explanation? Rjm at sleepers 10:17, 27 March 2007 (UTC)
