Copernicus Model of the Universe

Epicycles have been used to explain the observed motions of the planets since the ancient greeks, and they featured prominently in ptolemy's model. But when copernicus reordered everything and made the planets go around the sun, he scrapped somel es of the ptolemaic system. To compensate for those, he actually had to add more epicycles than ptoleMY used. A circle on a circle was called an epicuclos, or an epicycle, as we say in english.