Editing Albert Brudzewski (section)

=== Tusi couple ===
The Tusi couple was known as an epicycle arrangement that creates straight line motion of the planets, created by Copernicus.<ref>{{cite journal |last=Watson |first=A |date=1919 |title=Copernicus |journal=Journal of the Royal Astronomical Society of Canada |volume=13 |pages=264–282}}</ref> Some think that Brudzewski is the source for Copernicus's model of the Tusi couple. Albert does account for the moon and its double epicycles where he mentions a spot on the moon.<ref name=":0" /> The spot on the Moon is the problem of explaining the appearance of the face of the Moon when always viewing the Earth. These views were not aligned with the Tusi couple. Although, it is speculated that Copernicus could have encountered such a model, where the primary epicycle carries the center of a second epicycle. This is not the Tusi couple, but it could be slightly changed to match its model. The spot on the moon that is always viewed from the Earth would not appear if there was no epicyclical motion of the moon. The motion of the moon was termed as prosneusis motion which was part of the lunar theory. This motion means motion of inclination and turning, which corresponds to the single epicycle in Ptolemy's theory of the moon, and the two epicycles in Brudzewski's model.<ref name=":0" />

Brudzewski was aware of the possibility of linear motions from circular motions based on his model of Mercury's motion. This could be an alternative way that Copernicus generated his idea of linear motion for the Tusi couple. Although it seems that Copernicus used Albert's ideas, he highly relied on Islamic sources for the Tusi couple. Copernicus's parameters for the moon are exactly the same as those of [[Ibn al-Shatir]]. It is unclear where Copernicus truly got his ideas.<ref name=":0" />