Timeline of astronomy Rectification of Planetary Theory", eliminated the need for an equant by introducing an extra epicycle, departing from the Ptolemaic system in a way very similar to what Copernicus later also did. Ibn al-Shatir proposed a system that was only approximately geocentric, rather than exactly so, having demonstrated trigonometrically that the Earth was not the exact center of the universe. His rectification is later used in the Copernican model. Nicolaus Copernicus publishes "De revolutionibus orbium coelestium" containing his theory that Earth travels around the Sun. However, he complicates his theory by retaining Plato's perfect circular orbits of the planets. A brilliant
Earth, Moon, and Planets Earth, Moon, and Planets Earth, Moon, and Planets is a peer-reviewed scientific journal, published approximately ten times per year by Springer Science+Business Media. It was established in 1969 under the title "The Moon", was known as "The Moon and the Planets" from 1978 to 1983, and was first published under the current title in February 1984. The editor-in-chief is Murthy S. Gudipati (Caltech and JPL). The journal's main focus is on research about the Solar System. Besides original research articles, "Earth, Moon, and Planets" publishes conference proceedings, review articles, book reviews, and special issues. "Earth, Moon, and Planets" focuses on