De revolutionibus orbium coelestium divided into six "books" (sections or parts), following closely the layout of Ptolemy's "Almagest" which it updated and replaced: Copernicus argued that the universe comprised eight spheres. The outermost consisted of motionless, fixed stars, with the Sun motionless at the center. The known planets revolved about the Sun, each in its own sphere, in the order: Mercury, Venus, Earth, Mars, Jupiter, Saturn. The Moon, however, revolved in its sphere around the Earth. What appeared to be the daily revolution of the Sun and fixed stars around the Earth was actually the Earth's daily rotation on its own axis. Copernicus adhered
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