Editing Deferent and epicycle (section)

==Bad science==
"Adding epicycles" has come to be used as a derogatory comment in modern scientific discussion. The term might be used, for example, to describe continuing to [[ad hoc hypothesis|try to adjust]] a theory to make its predictions match the facts. There is a generally accepted idea that extra epicycles were invented to alleviate the growing errors that the Ptolemaic system noted as measurements became more accurate, particularly for Mars. According to this notion, epicycles are regarded by some as the paradigmatic example of bad science.<ref>See e.g., Kolb, Rocky, ''Blind Watchers of the Sky'', Addison–Wesley, 1996. p. 299. ({{ISBN|0-201-48992-9}})</ref>

Copernicus added an extra epicycle to his planets, but that was only in an effort to eliminate Ptolemy's equant, which he considered a philosophical break away from Aristotle's perfection of the heavens. Mathematically, the second epicycle and the equant produce nearly the same results, and many Copernican astronomers before Kepler continued using the equant, as the mathematical calculations were easier. Copernicus' epicycles were also much smaller than Ptolemy's, and were required because the planets in his model moved in perfect circles. [[Johannes Kepler]] would later show that the planets move in ellipses, which removed the need for Copernicus' epicycles as well.<ref>{{cite web |title=Whose Revolution? Copernicus, Brahe & Kepler {{!}} Modeling the Cosmos {{!}} Articles and Essays {{!}} Finding Our Place in the Cosmos: From Galileo to Sagan and Beyond {{!}} Digital Collections {{!}} Library of Congress |url=https://www.loc.gov/collections/finding-our-place-in-the-cosmos-with-carl-sagan/articles-and-essays/modeling-the-cosmos/whose-revolution-copernicus-brahe-and-kepler |access-date=2021-12-06 |website=Library of Congress, Washington, D.C.}}</ref>