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
Myth of the flat Earth flat Earth. The widely circulated engraving of a man poking his head through the firmament surrounding the Earth to view the Empyrean, executed in the style of the 16th century, was published in Camille Flammarion's "L'Atmosphère: Météorologie Populaire" (Paris, 1888, p. 163). The engraving illustrates the statement in the text that a medieval missionary claimed that "he reached the horizon where the Earth and the heavens met". In its original form, the engraving included a decorative border that places it in the 19th century. In later publications, some of which claimed that the engraving dates to the 16th century, the