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
Allegory of the Planets and Continents Allegory of the Planets and Continents Allegory of the Planets and Continents is an 18th-century painting by Italian artist Giovanni Battista Tiepolo. Done in oil on canvas, the allegorical work uses human figures to represent members of the Greco-Roman pantheon, the planets, and four continents. The painting is an elaborate oil sketch made by Tiepolo in preparation for rendering a similar, larger version of his scene. Tiepolo's work was painted to be hung above a staircase of the Wurzburg Residence in Wurzburg, Germany. The intricate painting depicts figures circling around Tiepolo's rendering of Apollo, the sun god; this represents planets