Talk:Ptolemaic system

What about the beliefe there existed two orthogonal oceans, thus both lat/lon was limited to 90/180 deg bounds.Didn't he (Ptolemy) stop making maps near the extreme coordinates, claiming nothing could exist there? (83.226.130.159 16:05, 12 Nov 2004 (UTC))

A book I have in front of me says, "In Ptolemaic astronomy, the stars move about the earth in crystalline spheres, giving out incredibly beautiful music that humans cannot hear." Is there any truth to this? This is just from the sidenotes in the Twelfth Night book I have, but I want to know if there's any veracity in the statement.

Pythagoras talked about the music of the spheres earlier, though he may have referred to ratios or intervals between the orbits rather than literal music. (Hence, "humans cannot hear.") I don't know if Ptolemy even postulated literal crystalline spheres, or if he thought the heavenly bodies moved in response to heavenly Intelligences without physical cause. (I know Aristotle postulated an Intelligence of sorts for each different circular motion, so each imagined epicycle would have its own Mover.) But certainly some in the Middle Ages would have agreed with this. Dan 19:49, 27 November 2005 (UTC)[reply]

Image

The image currently in the article is a good one to illustrate the celestial spheres but lacks much of the key elements of the Ptolemaic system (no epicycles, etc.). I'll try to find another one which will work, but if someone else knows a good, expired source... --Fastfission 23:11, 28 December 2005 (UTC)[reply]

Error?

The paragraph "Replacement with Copernican system" doen't make sense to me. Surely it's in the Copernican system that "Venus can only be either between Earth and the Sun, or on the other side of the Sun" (i.e. not on the other side of Earth from the Sun), giving the correct result that Venus goes through all phases, unlike the planets beyond Earth which cannot be between Earth and the Sun (crescent phase). Have I misread the paragraph?

Merge with Geocentric model?

I think this article should be merged with Geocentric model. Lambiam ^Talk 10:47, 9 April 2006 (UTC)[reply]

Agreed. I favor redirecting from Geocentric model to here. --Art Carlson 14:17, 9 April 2006 (UTC)[reply]

I support, and I am tagging both articles accordingly. Maestlin 00:24, 14 April 2006 (UTC)[reply]

Disagree, Ptolemaic is not the only geocentric model. Heraclides Ponticus and Tycho Brahe both proposed models that were geocentric but completely different from Ptolemy. Do you propose to merge Tychonic system into the same article? Cutler 07:54, 14 April 2006 (UTC)[reply]

Good point. I still support a merge only if the material ends up in the Geocentric model article. However, I can't agree with the specific examples you cited. The Tychonic system is geoheliocentric, not pure geocentric, so there's no compelling reason to merge it. There has been a lot of debate over what system Heraclides actually advocated, but I assume you have in mind the sort of thing Martianus Capella described? That probably deserves a description in both articles, as well as heliocentric. A better example is the Platonic order, which is clearly geocentric yet different from Ptolemy. Maestlin 15:20, 14 April 2006 (UTC)[reply]