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
Paris in the 16th century art, did not come until the very end of the century with the reign of Henry IV. Through the 16th century, there were only four bridges across the Seine, two on each bank, insufficient for the growing city and the amount of traffic they carried. The Paris bridges at the beginning of the 16th century were largely made of wood, and were frequently washed away in floods or knocked down by ice on the frozen river. The most important bridge was the Pont au Change, which had been built in 1304 under Philip le Bel, and was site where the