Talk:Tusi-couple

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[edit] Copyright violation?

The opening lines "The Tusi-couple ... (Sotiroudis and Paschos 1999, p. 60; Kanas 2003)" are taken verbatim from [1], without citation (and without giving the full form of the references cited there).

[edit] Description of Tusi Couple

I have removed Maestlin's sentence "The large circle rotates in the opposite direction at half the speed, carrying the small circle with it." since the two animations of the Tusi Couple in the external links both have the small circle rotating within a fixed outer circle. There is also a way to depict the Tusi couple in which two circles of the same size rotate in opposite directions, but this is not the one in the animations or in the diagram from the Vatican manuscript of Tusi's invention. Di Bono's article in JHA discusses the various ways to depict the Tusi couple.

--SteveMcCluskey 00:14, 20 June 2006 (UTC)

I will edit the article to incorporate what Tusi said about the rectilinear Tusi couple, since accuracy needs to take precedence over keeping the article consistent with external links. F.J. Ragep addresses the "rolling" question in his commentary on Tusi's Memoir on Astronomy:

"In point of fact, Tusi does not need two motions to achieve the oscillation of his given point along the diameter of the larger circle; he merely needs to allow the smaller circle to "roll" inside the larger one, which would remain stationary. ... I have belabored this rather obvious point in order to underscore the fact that Tusi does not proceed in this manner. The reason is that this lemma is not simply a mathematical theorem; it is meant to have a physical application and therefore the added stipulations are necessary. For there can be no rolling in the heavens; only rotation in place is allowed since there is no void. It is unfortunate that Kennedy--and others--have persisted in calling the Tusi couple a "rolling device," which is emphatically is not." (vol. 2, pp. 433-34)

If you think that the other two versions of the Tusi couple should be included, don't let the lack of animations or diagrams stop you from writing up a description. Maestlin 18:48, 20 June 2006 (UTC)