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 original research articles on formation of stars and planets, evolution of the Solar System including its origin, and the evolution of extra-solar systems including their origins. The focus also includes asteroids, comets, meteoroids, and near-Earth objects, Earth impact hazards, the Solar System-Earth relationship, and related topics. Research coverage encompasses physical and chemical properties of the above-mentioned celestial bodies, and their related chaotic behavior. This journal is abstracted and indexed in the following databases: 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